Spikes in DEC #guiding #Guiding


Seb@stro
 

Hello all, 

I'm having some spikes in my DEC guiding at times tonight. The worst ones seem to occur at periodic interval around 20-25 seconds but not all the time. Like about a dozen times in 400s periods. RMS values are good but DEC is about 40% bigger than RA because of these excursions. 

Conditions are fairly good now. No wind at all. Balance was quite accurate (as far as my eye can tell) in both RA and DEC. PA error reported by PHD2 is below 5 arc-min. I have a NUC on top of OTA, so no cable snag possible. Seeing is fair at 3.5-4".

My setup:
-EdgeHD 800 reduced to 1400mm FL
-Guide cam pixel scale : 1.7"/px
-Guiding through OAG at 3-4 seconds interval

Imaging M106 which is about 2hrs past meridian at the time of writing this.

That said, I'm not that familiar with guiding at such focal length... Any thoughts on what might be causing this ?

Sebastien


 

Hi  Sebastien

Please upload your guidelogs for this https://openphdguiding.org/getting-help/ 


Screen caps aren't enough information, but a quick glance looks like you have pretty bad polar alignment which would dramatically impact your DEC guiding

guidelogs would tell more


I wonder how much of an issue guiding is here - your overall rms is 0.49" and your image scale is 1.7"/pix, i'm guessing even if you addressed this you may not see a difference in your images


Brian
 

On Sun, May 2, 2021 at 9:44 PM Seb@stro <sebastiendore1@...> wrote:
Hello all, 

I'm having some spikes in my DEC guiding at times tonight. The worst ones seem to occur at periodic interval around 20-25 seconds but not all the time. Like about a dozen times in 400s periods. RMS values are good but DEC is about 40% bigger than RA because of these excursions. 

Conditions are fairly good now. No wind at all. Balance was quite accurate (as far as my eye can tell) in both RA and DEC. PA error reported by PHD2 is below 5 arc-min. I have a NUC on top of OTA, so no cable snag possible. Seeing is fair at 3.5-4".

My setup:
-EdgeHD 800 reduced to 1400mm FL
-Guide cam pixel scale : 1.7"/px
-Guiding through OAG at 3-4 seconds interval

Imaging M106 which is about 2hrs past meridian at the time of writing this.

That said, I'm not that familiar with guiding at such focal length... Any thoughts on what might be causing this ?

Sebastien



--
Brian 



Brian Valente


Seb@stro
 

Hi Brian,

Thanks for your reply.  Logs here: https://openphdguiding.org/logs/dl/PHD2_logs_BqZp.zip

I should probably have added that my imaging scale is 1.04"/px. So it's probably impacting a bit, maybe not much... But to be honest my concern was also about the working order the mount.  

But don't get me wrong, I'm coming from a low budget asian mount and got the Mach2 about 2 months ago. It performs WAAAAAAAAYYYYYYYYYYYYYYY better, no question there. So there's the fact that I'm not very familiar with AP mounts limits regarding tracking and guiding yet. Had a handful of clear nights only. And I know my system is the challenging kind (mirrors, long FL, reducer backfocus, etc.)... So I just thought I'd ask for educated guess here.

Might also be PA as you pointed out. But I thought I did well since I polar aligned with RAPAS at the beginning of my session and refined with PHD2 polar drift align afterward. When I ran the Guiding assistant, I recall it was saying it was around 2-3 arcmin from the NCP... Do you think it's reasonable for my imaging scale (1"/px) ?

Sebastien


De : main@ap-gto.groups.io <main@ap-gto.groups.io> de la part de Brian Valente <bvalente@...>
Envoyé : 3 mai 2021 00:48
À : main@ap-gto.groups.io <main@ap-gto.groups.io>
Objet : Re: [ap-gto] Spikes in DEC #guiding #guiding
 
Hi  Sebastien

Please upload your guidelogs for this https://openphdguiding.org/getting-help/ 


Screen caps aren't enough information, but a quick glance looks like you have pretty bad polar alignment which would dramatically impact your DEC guiding

guidelogs would tell more


I wonder how much of an issue guiding is here - your overall rms is 0.49" and your image scale is 1.7"/pix, i'm guessing even if you addressed this you may not see a difference in your images


Brian
 

On Sun, May 2, 2021 at 9:44 PM Seb@stro <sebastiendore1@...> wrote:
Hello all, 

I'm having some spikes in my DEC guiding at times tonight. The worst ones seem to occur at periodic interval around 20-25 seconds but not all the time. Like about a dozen times in 400s periods. RMS values are good but DEC is about 40% bigger than RA because of these excursions. 

Conditions are fairly good now. No wind at all. Balance was quite accurate (as far as my eye can tell) in both RA and DEC. PA error reported by PHD2 is below 5 arc-min. I have a NUC on top of OTA, so no cable snag possible. Seeing is fair at 3.5-4".

My setup:
-EdgeHD 800 reduced to 1400mm FL
-Guide cam pixel scale : 1.7"/px
-Guiding through OAG at 3-4 seconds interval

Imaging M106 which is about 2hrs past meridian at the time of writing this.

That said, I'm not that familiar with guiding at such focal length... Any thoughts on what might be causing this ?

Sebastien



--
Brian 



Brian Valente


 

HI Sebastian

I suggest you take this up with AP in their forums

encoder mounts like the Mach 2 require some basic correct setup, and i'm not sure yours is there (i'm not suggesting there's anything wrong with the mount at all: you are guiding < 0.50")

 looking at a typical run, your DEC is odd for the following reasons: 
- those excursions are not the result of any PHD type of correction
- all your corrections are in one direction both RA and DEC, and corrections exhibit a clumping 

this is dec showing the large instantaneous jumps and guiding in only one direction 
image.png

image.png

I suggest you do a guiding assistant run for a few minutes to measure polar misalignment. it could be something is terribly off on polar align, but based on what you're saying i don't know. 



On Sun, May 2, 2021 at 10:29 PM Seb@stro <sebastiendore1@...> wrote:
Hi Brian,

Thanks for your reply.  Logs here: https://openphdguiding.org/logs/dl/PHD2_logs_BqZp.zip

I should probably have added that my imaging scale is 1.04"/px. So it's probably impacting a bit, maybe not much... But to be honest my concern was also about the working order the mount.  

But don't get me wrong, I'm coming from a low budget asian mount and got the Mach2 about 2 months ago. It performs WAAAAAAAAYYYYYYYYYYYYYYY better, no question there. So there's the fact that I'm not very familiar with AP mounts limits regarding tracking and guiding yet. Had a handful of clear nights only. And I know my system is the challenging kind (mirrors, long FL, reducer backfocus, etc.)... So I just thought I'd ask for educated guess here.

Might also be PA as you pointed out. But I thought I did well since I polar aligned with RAPAS at the beginning of my session and refined with PHD2 polar drift align afterward. When I ran the Guiding assistant, I recall it was saying it was around 2-3 arcmin from the NCP... Do you think it's reasonable for my imaging scale (1"/px) ?

Sebastien


De : main@ap-gto.groups.io <main@ap-gto.groups.io> de la part de Brian Valente <bvalente@...>
Envoyé : 3 mai 2021 00:48
À : main@ap-gto.groups.io <main@ap-gto.groups.io>
Objet : Re: [ap-gto] Spikes in DEC #guiding #guiding
 
Hi  Sebastien

Please upload your guidelogs for this https://openphdguiding.org/getting-help/ 


Screen caps aren't enough information, but a quick glance looks like you have pretty bad polar alignment which would dramatically impact your DEC guiding

guidelogs would tell more


I wonder how much of an issue guiding is here - your overall rms is 0.49" and your image scale is 1.7"/pix, i'm guessing even if you addressed this you may not see a difference in your images


Brian
 

On Sun, May 2, 2021 at 9:44 PM Seb@stro <sebastiendore1@...> wrote:
Hello all, 

I'm having some spikes in my DEC guiding at times tonight. The worst ones seem to occur at periodic interval around 20-25 seconds but not all the time. Like about a dozen times in 400s periods. RMS values are good but DEC is about 40% bigger than RA because of these excursions. 

Conditions are fairly good now. No wind at all. Balance was quite accurate (as far as my eye can tell) in both RA and DEC. PA error reported by PHD2 is below 5 arc-min. I have a NUC on top of OTA, so no cable snag possible. Seeing is fair at 3.5-4".

My setup:
-EdgeHD 800 reduced to 1400mm FL
-Guide cam pixel scale : 1.7"/px
-Guiding through OAG at 3-4 seconds interval

Imaging M106 which is about 2hrs past meridian at the time of writing this.

That said, I'm not that familiar with guiding at such focal length... Any thoughts on what might be causing this ?

Sebastien



--
Brian 



Brian Valente



--
Brian 



Brian Valente


 

PS

i just found your PA run sorry i missed that

the DEC is a little bit concerning here. this is without any motor running and 3 second exposures, and yet the DEC looks remarkably uneven, especially with encoders (compare this to your RA in blue)
image.png


On Sun, May 2, 2021 at 10:29 PM Seb@stro <sebastiendore1@...> wrote:
Hi Brian,

Thanks for your reply.  Logs here: https://openphdguiding.org/logs/dl/PHD2_logs_BqZp.zip

I should probably have added that my imaging scale is 1.04"/px. So it's probably impacting a bit, maybe not much... But to be honest my concern was also about the working order the mount.  

But don't get me wrong, I'm coming from a low budget asian mount and got the Mach2 about 2 months ago. It performs WAAAAAAAAYYYYYYYYYYYYYYY better, no question there. So there's the fact that I'm not very familiar with AP mounts limits regarding tracking and guiding yet. Had a handful of clear nights only. And I know my system is the challenging kind (mirrors, long FL, reducer backfocus, etc.)... So I just thought I'd ask for educated guess here.

Might also be PA as you pointed out. But I thought I did well since I polar aligned with RAPAS at the beginning of my session and refined with PHD2 polar drift align afterward. When I ran the Guiding assistant, I recall it was saying it was around 2-3 arcmin from the NCP... Do you think it's reasonable for my imaging scale (1"/px) ?

Sebastien


De : main@ap-gto.groups.io <main@ap-gto.groups.io> de la part de Brian Valente <bvalente@...>
Envoyé : 3 mai 2021 00:48
À : main@ap-gto.groups.io <main@ap-gto.groups.io>
Objet : Re: [ap-gto] Spikes in DEC #guiding #guiding
 
Hi  Sebastien

Please upload your guidelogs for this https://openphdguiding.org/getting-help/ 


Screen caps aren't enough information, but a quick glance looks like you have pretty bad polar alignment which would dramatically impact your DEC guiding

guidelogs would tell more


I wonder how much of an issue guiding is here - your overall rms is 0.49" and your image scale is 1.7"/pix, i'm guessing even if you addressed this you may not see a difference in your images


Brian
 

On Sun, May 2, 2021 at 9:44 PM Seb@stro <sebastiendore1@...> wrote:
Hello all, 

I'm having some spikes in my DEC guiding at times tonight. The worst ones seem to occur at periodic interval around 20-25 seconds but not all the time. Like about a dozen times in 400s periods. RMS values are good but DEC is about 40% bigger than RA because of these excursions. 

Conditions are fairly good now. No wind at all. Balance was quite accurate (as far as my eye can tell) in both RA and DEC. PA error reported by PHD2 is below 5 arc-min. I have a NUC on top of OTA, so no cable snag possible. Seeing is fair at 3.5-4".

My setup:
-EdgeHD 800 reduced to 1400mm FL
-Guide cam pixel scale : 1.7"/px
-Guiding through OAG at 3-4 seconds interval

Imaging M106 which is about 2hrs past meridian at the time of writing this.

That said, I'm not that familiar with guiding at such focal length... Any thoughts on what might be causing this ?

Sebastien



--
Brian 



Brian Valente



--
Brian 



Brian Valente


Seb@stro
 

Thanks for your analysis Brian. 

What you see there is due to serious wind gusts present at the beginning of the run. I even had to remove the dew shield to help with that... But by 11:15-11:30PM, wind had entirely stopped. 

It's more with the spikes that I am concerned. By the time I saw them, conditions had greatly improved (no wind, 60% RH, -1 Celsius) compared to the beginning of the session.

At any rate, sincere thanks for chiming in. I'll see what AP thinks about that tomorrow (well, later today 🙂).

Clear skies,
Sebastien

De : main@ap-gto.groups.io <main@ap-gto.groups.io> de la part de Brian Valente <bvalente@...>
Envoyé : 3 mai 2021 03:03
À : main@ap-gto.groups.io <main@ap-gto.groups.io>
Objet : Re: [ap-gto] Spikes in DEC #guiding #guiding
 
PS

i just found your PA run sorry i missed that

the DEC is a little bit concerning here. this is without any motor running and 3 second exposures, and yet the DEC looks remarkably uneven, especially with encoders (compare this to your RA in blue)
image.png



Howard Hedlund
 

Hi Sebastien,
First off, remember that the declination axis does not track unless a model is present, and then it would only be extremely slow.  Dec spikes pretty much have to come from software that is controlling the autoguiding, especially in a mount with the Absolute Encoder System like the Mach2.  I haven't had a chance to look at your PHD logs yet, but first, what software are you using along with PHD2?   APCC?  TheSkyX?  SGPro?  Something else?  If you are using APCC, please send me its zipped log files from the session above.  To use PHD2, you must have the AP V2 driver in play.  Those logs will also be valuable.
Send to:   howard at astro-physics dot com
I'm in the middle of a rush project, so please be patient with me and don't expect an analysis in the next 10 minutes!  ;^)
Also, please note that Brian V. is an excellent source of advice.  Take what he tells you seriously.
Howard Hedlund
Astro-Physics Technical Support


Roland Christen
 

Hello Sebastien,

I sent you an e-mail, please check.

Roland



-----Original Message-----
From: Seb@stro <sebastiendore1@...>
To: main@ap-gto.groups.io
Sent: Sun, May 2, 2021 11:44 pm
Subject: [ap-gto] Spikes in DEC #guiding

Hello all, 

I'm having some spikes in my DEC guiding at times tonight. The worst ones seem to occur at periodic interval around 20-25 seconds but not all the time. Like about a dozen times in 400s periods. RMS values are good but DEC is about 40% bigger than RA because of these excursions. 

Conditions are fairly good now. No wind at all. Balance was quite accurate (as far as my eye can tell) in both RA and DEC. PA error reported by PHD2 is below 5 arc-min. I have a NUC on top of OTA, so no cable snag possible. Seeing is fair at 3.5-4".

My setup:
-EdgeHD 800 reduced to 1400mm FL
-Guide cam pixel scale : 1.7"/px
-Guiding through OAG at 3-4 seconds interval

Imaging M106 which is about 2hrs past meridian at the time of writing this.

That said, I'm not that familiar with guiding at such focal length... Any thoughts on what might be causing this ?

Sebastien


--
Roland Christen
Astro-Physics


Seb@stro
 

Hi Brian,

encoder mounts like the Mach 2 require some basic correct setup, and i'm not sure yours is there

Just re-reading your comment above and  I'm not sure I clearly understand what you mean by "basic correct setup". Are suggesting I should refine some settings within the imaging/guiding softwares ? Or are you saying I should look into the mechanical aspect of the OTA, OAG, camera, etc. ?

I just saw Howard and Roland also replied, so I will follow-up with them as well. 

I must add I am not just blown away by the mount's performance which, as you pointed out, is very good at < 0.5", but also by AP's ***** (five stars) customer service. A flawless customer experience...

Sebastien


De : main@ap-gto.groups.io <main@ap-gto.groups.io> de la part de Brian Valente <bvalente@...>
Envoyé : 3 mai 2021 03:00
À : main@ap-gto.groups.io <main@ap-gto.groups.io>
Objet : Re: [ap-gto] Spikes in DEC #guiding #guiding
 
HI Sebastian

I suggest you take this up with AP in their forums

encoder mounts like the Mach 2 require some basic correct setup, and i'm not sure yours is there (i'm not suggesting there's anything wrong with the mount at all: you are guiding < 0.50")

 looking at a typical run, your DEC is odd for the following reasons: 
- those excursions are not the result of any PHD type of correction
- all your corrections are in one direction both RA and DEC, and corrections exhibit a clumping 

this is dec showing the large instantaneous jumps and guiding in only one direction 
image.png

image.png

I suggest you do a guiding assistant run for a few minutes to measure polar misalignment. it could be something is terribly off on polar align, but based on what you're saying i don't know. 



On Sun, May 2, 2021 at 10:29 PM Seb@stro <sebastiendore1@...> wrote:
Hi Brian,

Thanks for your reply.  Logs here: https://openphdguiding.org/logs/dl/PHD2_logs_BqZp.zip

I should probably have added that my imaging scale is 1.04"/px. So it's probably impacting a bit, maybe not much... But to be honest my concern was also about the working order the mount.  

But don't get me wrong, I'm coming from a low budget asian mount and got the Mach2 about 2 months ago. It performs WAAAAAAAAYYYYYYYYYYYYYYY better, no question there. So there's the fact that I'm not very familiar with AP mounts limits regarding tracking and guiding yet. Had a handful of clear nights only. And I know my system is the challenging kind (mirrors, long FL, reducer backfocus, etc.)... So I just thought I'd ask for educated guess here.

Might also be PA as you pointed out. But I thought I did well since I polar aligned with RAPAS at the beginning of my session and refined with PHD2 polar drift align afterward. When I ran the Guiding assistant, I recall it was saying it was around 2-3 arcmin from the NCP... Do you think it's reasonable for my imaging scale (1"/px) ?

Sebastien


De : main@ap-gto.groups.io <main@ap-gto.groups.io> de la part de Brian Valente <bvalente@...>
Envoyé : 3 mai 2021 00:48
À : main@ap-gto.groups.io <main@ap-gto.groups.io>
Objet : Re: [ap-gto] Spikes in DEC #guiding #guiding
 
Hi  Sebastien

Please upload your guidelogs for this https://openphdguiding.org/getting-help/ 


Screen caps aren't enough information, but a quick glance looks like you have pretty bad polar alignment which would dramatically impact your DEC guiding

guidelogs would tell more


I wonder how much of an issue guiding is here - your overall rms is 0.49" and your image scale is 1.7"/pix, i'm guessing even if you addressed this you may not see a difference in your images


Brian
 

On Sun, May 2, 2021 at 9:44 PM Seb@stro <sebastiendore1@...> wrote:
Hello all, 

I'm having some spikes in my DEC guiding at times tonight. The worst ones seem to occur at periodic interval around 20-25 seconds but not all the time. Like about a dozen times in 400s periods. RMS values are good but DEC is about 40% bigger than RA because of these excursions. 

Conditions are fairly good now. No wind at all. Balance was quite accurate (as far as my eye can tell) in both RA and DEC. PA error reported by PHD2 is below 5 arc-min. I have a NUC on top of OTA, so no cable snag possible. Seeing is fair at 3.5-4".

My setup:
-EdgeHD 800 reduced to 1400mm FL
-Guide cam pixel scale : 1.7"/px
-Guiding through OAG at 3-4 seconds interval

Imaging M106 which is about 2hrs past meridian at the time of writing this.

That said, I'm not that familiar with guiding at such focal length... Any thoughts on what might be causing this ?

Sebastien



--
Brian 



Brian Valente



--
Brian 



Brian Valente


 

Hi Sebastian

I meant things exactly like what Roland said - he suggested it was DEC imbalance.

On Mon, May 3, 2021 at 11:43 AM Seb@stro <sebastiendore1@...> wrote:
Hi Brian,

encoder mounts like the Mach 2 require some basic correct setup, and i'm not sure yours is there

Just re-reading your comment above and  I'm not sure I clearly understand what you mean by "basic correct setup". Are suggesting I should refine some settings within the imaging/guiding softwares ? Or are you saying I should look into the mechanical aspect of the OTA, OAG, camera, etc. ?

I just saw Howard and Roland also replied, so I will follow-up with them as well. 

I must add I am not just blown away by the mount's performance which, as you pointed out, is very good at < 0.5", but also by AP's ***** (five stars) customer service. A flawless customer experience...

Sebastien


De : main@ap-gto.groups.io <main@ap-gto.groups.io> de la part de Brian Valente <bvalente@...>
Envoyé : 3 mai 2021 03:00
À : main@ap-gto.groups.io <main@ap-gto.groups.io>
Objet : Re: [ap-gto] Spikes in DEC #guiding #guiding
 
HI Sebastian

I suggest you take this up with AP in their forums

encoder mounts like the Mach 2 require some basic correct setup, and i'm not sure yours is there (i'm not suggesting there's anything wrong with the mount at all: you are guiding < 0.50")

 looking at a typical run, your DEC is odd for the following reasons: 
- those excursions are not the result of any PHD type of correction
- all your corrections are in one direction both RA and DEC, and corrections exhibit a clumping 

this is dec showing the large instantaneous jumps and guiding in only one direction 
image.png

image.png

I suggest you do a guiding assistant run for a few minutes to measure polar misalignment. it could be something is terribly off on polar align, but based on what you're saying i don't know. 



On Sun, May 2, 2021 at 10:29 PM Seb@stro <sebastiendore1@...> wrote:
Hi Brian,

Thanks for your reply.  Logs here: https://openphdguiding.org/logs/dl/PHD2_logs_BqZp.zip

I should probably have added that my imaging scale is 1.04"/px. So it's probably impacting a bit, maybe not much... But to be honest my concern was also about the working order the mount.  

But don't get me wrong, I'm coming from a low budget asian mount and got the Mach2 about 2 months ago. It performs WAAAAAAAAYYYYYYYYYYYYYYY better, no question there. So there's the fact that I'm not very familiar with AP mounts limits regarding tracking and guiding yet. Had a handful of clear nights only. And I know my system is the challenging kind (mirrors, long FL, reducer backfocus, etc.)... So I just thought I'd ask for educated guess here.

Might also be PA as you pointed out. But I thought I did well since I polar aligned with RAPAS at the beginning of my session and refined with PHD2 polar drift align afterward. When I ran the Guiding assistant, I recall it was saying it was around 2-3 arcmin from the NCP... Do you think it's reasonable for my imaging scale (1"/px) ?

Sebastien


De : main@ap-gto.groups.io <main@ap-gto.groups.io> de la part de Brian Valente <bvalente@...>
Envoyé : 3 mai 2021 00:48
À : main@ap-gto.groups.io <main@ap-gto.groups.io>
Objet : Re: [ap-gto] Spikes in DEC #guiding #guiding
 
Hi  Sebastien

Please upload your guidelogs for this https://openphdguiding.org/getting-help/ 


Screen caps aren't enough information, but a quick glance looks like you have pretty bad polar alignment which would dramatically impact your DEC guiding

guidelogs would tell more


I wonder how much of an issue guiding is here - your overall rms is 0.49" and your image scale is 1.7"/pix, i'm guessing even if you addressed this you may not see a difference in your images


Brian
 

On Sun, May 2, 2021 at 9:44 PM Seb@stro <sebastiendore1@...> wrote:
Hello all, 

I'm having some spikes in my DEC guiding at times tonight. The worst ones seem to occur at periodic interval around 20-25 seconds but not all the time. Like about a dozen times in 400s periods. RMS values are good but DEC is about 40% bigger than RA because of these excursions. 

Conditions are fairly good now. No wind at all. Balance was quite accurate (as far as my eye can tell) in both RA and DEC. PA error reported by PHD2 is below 5 arc-min. I have a NUC on top of OTA, so no cable snag possible. Seeing is fair at 3.5-4".

My setup:
-EdgeHD 800 reduced to 1400mm FL
-Guide cam pixel scale : 1.7"/px
-Guiding through OAG at 3-4 seconds interval

Imaging M106 which is about 2hrs past meridian at the time of writing this.

That said, I'm not that familiar with guiding at such focal length... Any thoughts on what might be causing this ?

Sebastien



--
Brian 



Brian Valente



--
Brian 



Brian Valente



--
Brian 



Brian Valente


Seb@stro
 

Thank you Brian and Roland.

While its not impossible that DEC balance was off for some reason, I would say it's unlikely as I usually do it the same manner Roland described and last night was no different. In fact, I even use the dovetail riser as a reference point (see below) when loading the OTA which I know is pretty spot-on balance. But I always check in Park2, before balancing RA, swing it to Park3, balance RA and then send to Park5 to check again and adjust if necessary.

Unfortunately, as I setup and tear down every night, I can't assess if that was the culprit. Will need to wait for the next clear night to see if any different, hopefully by the end of the week.



Here's a shot with all 4 DEC clutches fully loosened and OTA at balance point above. I can easily move it up and down with a single finger by lightly pushing on the top/bottom side of the dewshield or backend of the camera and it won't freefall in any case.



I also should say that I did a Guide Assistant run at the end of the night like you suggested, and PHD2 then reported a 20 arc-min from NCP ! 

Now, I'm not clear on how such a difference (from the beginning of the night, where it supposedly was in the 2-3" range) could have occured as I almost overtighten and triple-check each and every knobs, clutches or whatever I can grab onto before firing up the imaging session. I make sure of that because temperature sometimes falls quite suddenly at night at this time of year (20C in like 1-2 hrs) and I've experience times where metal contraction was enough to virtually loosen things up. Last night was not that bad (about 10C between evening and midnight) but maybe I overlooked one of the dovetail knobs or the wheels that tighten the altitude adjustment, but again I'd be surprised.

Another thought I had today, was the possibility that the Polar Drift Align routine in PHD2 might have had difficulties in evaluating the field rotation correctly. Especially since the field of view through the OAG is tiny at 1422mm (like under half a degree with QHY5-174MM) in addition to the serious wind gusts that were relentlessly pushing against the assembly and then, encoders fighting back to keep it on target as you saw on the erratic initial Guiding Assistant plot. 

In the end, could it be possible it might have mistakenly directed me away from the pole instead of towards it ?

The thing I am uncertain about that theory however is how that would explain the 130s periodic spikes I got for a while. If my PHD2 settings were reasonable and Dec balance OK, then I just hope I have not prematurely worn out the gears/motors/else by accident in some way. I'm usually pretty careful, but life taught me that too much care can end up in the entire opposite of what you're trying to achieve sometimes... :-S

Sébastien


Seb@stro
 

Ooops, not sure why the second photo showing balance in Park5 didn't go through. Please see attached.



De : main@ap-gto.groups.io <main@ap-gto.groups.io> de la part de Seb@stro <sebastiendore1@...>
Envoyé : 3 mai 2021 22:03
À : main@ap-gto.groups.io <main@ap-gto.groups.io>
Objet : Re: [ap-gto] Spikes in DEC #guiding #guiding
 
Thank you Brian and Roland.

While its not impossible that DEC balance was off for some reason, I would say it's unlikely as I usually do it the same manner Roland described and last night was no different. In fact, I even use the dovetail riser as a reference point (see below) when loading the OTA which I know is pretty spot-on balance. But I always check in Park2, before balancing RA, swing it to Park3, balance RA and then send to Park5 to check again and adjust if necessary.

Unfortunately, as I setup and tear down every night, I can't assess if that was the culprit. Will need to wait for the next clear night to see if any different, hopefully by the end of the week.



Here's a shot with all 4 DEC clutches fully loosened and OTA at balance point above. I can easily move it up and down with a single finger by lightly pushing on the top/bottom side of the dewshield or backend of the camera and it won't freefall in any case.



I also should say that I did a Guide Assistant run at the end of the night like you suggested, and PHD2 then reported a 20 arc-min from NCP ! 

Now, I'm not clear on how such a difference (from the beginning of the night, where it supposedly was in the 2-3" range) could have occured as I almost overtighten and triple-check each and every knobs, clutches or whatever I can grab onto before firing up the imaging session. I make sure of that because temperature sometimes falls quite suddenly at night at this time of year (20C in like 1-2 hrs) and I've experience times where metal contraction was enough to virtually loosen things up. Last night was not that bad (about 10C between evening and midnight) but maybe I overlooked one of the dovetail knobs or the wheels that tighten the altitude adjustment, but again I'd be surprised.

Another thought I had today, was the possibility that the Polar Drift Align routine in PHD2 might have had difficulties in evaluating the field rotation correctly. Especially since the field of view through the OAG is tiny at 1422mm (like under half a degree with QHY5-174MM) in addition to the serious wind gusts that were relentlessly pushing against the assembly and then, encoders fighting back to keep it on target as you saw on the erratic initial Guiding Assistant plot. 

In the end, could it be possible it might have mistakenly directed me away from the pole instead of towards it ?

The thing I am uncertain about that theory however is how that would explain the 130s periodic spikes I got for a while. If my PHD2 settings were reasonable and Dec balance OK, then I just hope I have not prematurely worn out the gears/motors/else by accident in some way. I'm usually pretty careful, but life taught me that too much care can end up in the entire opposite of what you're trying to achieve sometimes... :-S

Sébastien


Roland Christen
 


I just hope I have not prematurely worn out the gears/motors/else by accident in some way.
You cannot wear out the gears and motors.

Roland


-----Original Message-----
From: Seb@stro <sebastiendore1@...>
To: main@ap-gto.groups.io <main@ap-gto.groups.io>
Sent: Mon, May 3, 2021 9:03 pm
Subject: Re: [ap-gto] Spikes in DEC #guiding #guiding

Thank you Brian and Roland.

While its not impossible that DEC balance was off for some reason, I would say it's unlikely as I usually do it the same manner Roland described and last night was no different. In fact, I even use the dovetail riser as a reference point (see below) when loading the OTA which I know is pretty spot-on balance. But I always check in Park2, before balancing RA, swing it to Park3, balance RA and then send to Park5 to check again and adjust if necessary.

Unfortunately, as I setup and tear down every night, I can't assess if that was the culprit. Will need to wait for the next clear night to see if any different, hopefully by the end of the week.



Here's a shot with all 4 DEC clutches fully loosened and OTA at balance point above. I can easily move it up and down with a single finger by lightly pushing on the top/bottom side of the dewshield or backend of the camera and it won't freefall in any case.



I also should say that I did a Guide Assistant run at the end of the night like you suggested, and PHD2 then reported a 20 arc-min from NCP ! 

Now, I'm not clear on how such a difference (from the beginning of the night, where it supposedly was in the 2-3" range) could have occured as I almost overtighten and triple-check each and every knobs, clutches or whatever I can grab onto before firing up the imaging session. I make sure of that because temperature sometimes falls quite suddenly at night at this time of year (20C in like 1-2 hrs) and I've experience times where metal contraction was enough to virtually loosen things up. Last night was not that bad (about 10C between evening and midnight) but maybe I overlooked one of the dovetail knobs or the wheels that tighten the altitude adjustment, but again I'd be surprised.

Another thought I had today, was the possibility that the Polar Drift Align routine in PHD2 might have had difficulties in evaluating the field rotation correctly. Especially since the field of view through the OAG is tiny at 1422mm (like under half a degree with QHY5-174MM) in addition to the serious wind gusts that were relentlessly pushing against the assembly and then, encoders fighting back to keep it on target as you saw on the erratic initial Guiding Assistant plot. 

In the end, could it be possible it might have mistakenly directed me away from the pole instead of towards it ?

The thing I am uncertain about that theory however is how that would explain the 130s periodic spikes I got for a while. If my PHD2 settings were reasonable and Dec balance OK, then I just hope I have not prematurely worn out the gears/motors/else by accident in some way. I'm usually pretty careful, but life taught me that too much care can end up in the entire opposite of what you're trying to achieve sometimes... :-S

Sébastien

--
Roland Christen
Astro-Physics


 

Seb

When i first reviewed your PHD logs, it appeared to me your polar alignment was quite off. All your corrections were in one direction

You said you thought it was the wind, but i have my doubts about that

so it's possible your polar alignment may be misaligned for whatever reason

On Mon, May 3, 2021 at 7:13 PM Seb@stro <sebastiendore1@...> wrote:
Ooops, not sure why the second photo showing balance in Park5 didn't go through. Please see attached.



De : main@ap-gto.groups.io <main@ap-gto.groups.io> de la part de Seb@stro <sebastiendore1@...>
Envoyé : 3 mai 2021 22:03
À : main@ap-gto.groups.io <main@ap-gto.groups.io>
Objet : Re: [ap-gto] Spikes in DEC #guiding #guiding
 
Thank you Brian and Roland.

While its not impossible that DEC balance was off for some reason, I would say it's unlikely as I usually do it the same manner Roland described and last night was no different. In fact, I even use the dovetail riser as a reference point (see below) when loading the OTA which I know is pretty spot-on balance. But I always check in Park2, before balancing RA, swing it to Park3, balance RA and then send to Park5 to check again and adjust if necessary.

Unfortunately, as I setup and tear down every night, I can't assess if that was the culprit. Will need to wait for the next clear night to see if any different, hopefully by the end of the week.



Here's a shot with all 4 DEC clutches fully loosened and OTA at balance point above. I can easily move it up and down with a single finger by lightly pushing on the top/bottom side of the dewshield or backend of the camera and it won't freefall in any case.



I also should say that I did a Guide Assistant run at the end of the night like you suggested, and PHD2 then reported a 20 arc-min from NCP ! 

Now, I'm not clear on how such a difference (from the beginning of the night, where it supposedly was in the 2-3" range) could have occured as I almost overtighten and triple-check each and every knobs, clutches or whatever I can grab onto before firing up the imaging session. I make sure of that because temperature sometimes falls quite suddenly at night at this time of year (20C in like 1-2 hrs) and I've experience times where metal contraction was enough to virtually loosen things up. Last night was not that bad (about 10C between evening and midnight) but maybe I overlooked one of the dovetail knobs or the wheels that tighten the altitude adjustment, but again I'd be surprised.

Another thought I had today, was the possibility that the Polar Drift Align routine in PHD2 might have had difficulties in evaluating the field rotation correctly. Especially since the field of view through the OAG is tiny at 1422mm (like under half a degree with QHY5-174MM) in addition to the serious wind gusts that were relentlessly pushing against the assembly and then, encoders fighting back to keep it on target as you saw on the erratic initial Guiding Assistant plot. 

In the end, could it be possible it might have mistakenly directed me away from the pole instead of towards it ?

The thing I am uncertain about that theory however is how that would explain the 130s periodic spikes I got for a while. If my PHD2 settings were reasonable and Dec balance OK, then I just hope I have not prematurely worn out the gears/motors/else by accident in some way. I'm usually pretty careful, but life taught me that too much care can end up in the entire opposite of what you're trying to achieve sometimes... :-S

Sébastien



--
Brian 



Brian Valente


Seb@stro
 

Reassuring, thanks!
Sébastien


De : main@ap-gto.groups.io <main@ap-gto.groups.io> de la part de Roland Christen via groups.io <chris1011@...>
Envoyé : 3 mai 2021 22:45
À : main@ap-gto.groups.io <main@ap-gto.groups.io>
Objet : Re: [ap-gto] Spikes in DEC #guiding #guiding
 

I just hope I have not prematurely worn out the gears/motors/else by accident in some way.
You cannot wear out the gears and motors.

Roland


-----Original Message-----
From: Seb@stro <sebastiendore1@...>
To: main@ap-gto.groups.io <main@ap-gto.groups.io>
Sent: Mon, May 3, 2021 9:03 pm
Subject: Re: [ap-gto] Spikes in DEC #guiding #guiding

Thank you Brian and Roland.

While its not impossible that DEC balance was off for some reason, I would say it's unlikely as I usually do it the same manner Roland described and last night was no different. In fact, I even use the dovetail riser as a reference point (see below) when loading the OTA which I know is pretty spot-on balance. But I always check in Park2, before balancing RA, swing it to Park3, balance RA and then send to Park5 to check again and adjust if necessary.

Unfortunately, as I setup and tear down every night, I can't assess if that was the culprit. Will need to wait for the next clear night to see if any different, hopefully by the end of the week.



Here's a shot with all 4 DEC clutches fully loosened and OTA at balance point above. I can easily move it up and down with a single finger by lightly pushing on the top/bottom side of the dewshield or backend of the camera and it won't freefall in any case.



I also should say that I did a Guide Assistant run at the end of the night like you suggested, and PHD2 then reported a 20 arc-min from NCP ! 

Now, I'm not clear on how such a difference (from the beginning of the night, where it supposedly was in the 2-3" range) could have occured as I almost overtighten and triple-check each and every knobs, clutches or whatever I can grab onto before firing up the imaging session. I make sure of that because temperature sometimes falls quite suddenly at night at this time of year (20C in like 1-2 hrs) and I've experience times where metal contraction was enough to virtually loosen things up. Last night was not that bad (about 10C between evening and midnight) but maybe I overlooked one of the dovetail knobs or the wheels that tighten the altitude adjustment, but again I'd be surprised.

Another thought I had today, was the possibility that the Polar Drift Align routine in PHD2 might have had difficulties in evaluating the field rotation correctly. Especially since the field of view through the OAG is tiny at 1422mm (like under half a degree with QHY5-174MM) in addition to the serious wind gusts that were relentlessly pushing against the assembly and then, encoders fighting back to keep it on target as you saw on the erratic initial Guiding Assistant plot. 

In the end, could it be possible it might have mistakenly directed me away from the pole instead of towards it ?

The thing I am uncertain about that theory however is how that would explain the 130s periodic spikes I got for a while. If my PHD2 settings were reasonable and Dec balance OK, then I just hope I have not prematurely worn out the gears/motors/else by accident in some way. I'm usually pretty careful, but life taught me that too much care can end up in the entire opposite of what you're trying to achieve sometimes... :-S

Sébastien

--
Roland Christen
Astro-Physics


Seb@stro
 

Well, I'm not the one who will contest your analysis, Brian. As Howard said earlier, your advice is to be taken seriously, and I agree! 🙂 And I also agree with your argument about the guiding pulse being in only one direction and being compatible with bad PA.

The reason why I said it was good in the first place is only because PHD told me so (see attached). It wasn't based on anything other data. Hence my hypothesis about it struggling to show me the real NCP when I did the Polar Drift Align in the gusty conditions...

Anyway, AP is also working with me behind the scenes to help figure out what could have happened. So, we'll see if they can shed some light on this from their perspective.

Sébastien


De : main@ap-gto.groups.io <main@ap-gto.groups.io> de la part de Brian Valente <bvalente@...>
Envoyé : 3 mai 2021 22:55
À : main@ap-gto.groups.io <main@ap-gto.groups.io>
Objet : Re: [ap-gto] Spikes in DEC #guiding #guiding
 
Seb

When i first reviewed your PHD logs, it appeared to me your polar alignment was quite off. All your corrections were in one direction

You said you thought it was the wind, but i have my doubts about that

so it's possible your polar alignment may be misaligned for whatever reason


Roland Christen
 

The fact that both RA and Dec are drifting so fast in just a few minute's time indicates either that your polar alignment is way off, or that the object that you are calibrating on is not near the celestial equator and meridian.

Roland

-----Original Message-----
From: Seb@stro <sebastiendore1@...>
To: main@ap-gto.groups.io <main@ap-gto.groups.io>
Sent: Mon, May 3, 2021 10:42 pm
Subject: Re: [ap-gto] Spikes in DEC #guiding #guiding

Well, I'm not the one who will contest your analysis, Brian. As Howard said earlier, your advice is to be taken seriously, and I agree! 🙂 And I also agree with your argument about the guiding pulse being in only one direction and being compatible with bad PA.

The reason why I said it was good in the first place is only because PHD told me so (see attached). It wasn't based on anything other data. Hence my hypothesis about it struggling to show me the real NCP when I did the Polar Drift Align in the gusty conditions...

Anyway, AP is also working with me behind the scenes to help figure out what could have happened. So, we'll see if they can shed some light on this from their perspective.

Sébastien


De : main@ap-gto.groups.io <main@ap-gto.groups.io> de la part de Brian Valente <bvalente@...>
Envoyé : 3 mai 2021 22:55
À : main@ap-gto.groups.io <main@ap-gto.groups.io>
Objet : Re: [ap-gto] Spikes in DEC #guiding #guiding
 
Seb

When i first reviewed your PHD logs, it appeared to me your polar alignment was quite off. All your corrections were in one direction

You said you thought it was the wind, but i have my doubts about that

so it's possible your polar alignment may be misaligned for whatever reason


--
Roland Christen
Astro-Physics


Seb@stro
 

Hi,

For reference, I did calibrate near M3 which was the nearest I could get from the celestial equator/meridian at the time, given high trees that obstruct my sight in the south. 

But guess what, it seems Brian, Howard and Roland were right from the very beginning. (Who would have thought? Silly me...)

It seems my DEC axis was indeed in severe imbalance and my PA was off after all... Moreover, it was entirely human mistake (as it usually is in these kind of situation).

Curious to know how I found out ? Here it goes. Given all hypothesis were pointing in the same direction (DEC imbalance, PA off), one can only admit the simplest explanation is that indeed these are right somehow. That was difficult to admit for me, since I was convinced I had done everything right from the beginning (and I had, as a matter of fact). But at the end of the night (that's one clue), even PHD2 figures were shouting at me : PA was 20 arc-min off and DEC corrections were in only one direction.

So I mentally replayed the night, trying to remember the smallest and finest details. And it struck me. Remember the wind ? And me saying I had to remove the dew shield to help with that ? And there you have it ! That simple: I had REMOVED the DEW SHIELD ! That explains how my 2.3' PA went to 20.1', (even if I removed it carefully it seems - it was tightly put as it only holds with friction so I had to pull it out with some force). One down. That could also explain the imbalance but at that point, I was still skeptical it could have been "severe" because that thing is made of thin plastic and pretty lightweight (< 13oz) compared to the rest of the load. That and the fact that when I work on the setup inside, the dewshield is also OFF (but dustcap is ON and only slightly lighter). Anyway, simple experiment would confirm: scope in park 5, dewshield ON, DEC balanced, unlock the clutches, remove dew shield. See result in attached JPG. Definitely a severe imbalance...

Mystery solved (for me at least, it was a mystery) and lesson learned: once set up, don't touch the dew shield (basic, I should have known).

Thanks to Brian and all the folks at AP, you guys did challenge me enough to bring me back on the right track. BTW, I haven't said it publicly yet but as others have already said, that Mach2 is a marvel of engineering and craftsmanship. Thanks AP for making this piece of art real. That mount and the customer service that comes with it is definitely worth every penny.

Sébastien


De : main@ap-gto.groups.io <main@ap-gto.groups.io> de la part de Roland Christen via groups.io <chris1011@...>
Envoyé : 4 mai 2021 11:21
À : main@ap-gto.groups.io <main@ap-gto.groups.io>
Objet : Re: [ap-gto] Spikes in DEC #guiding #guiding
 
The fact that both RA and Dec are drifting so fast in just a few minute's time indicates either that your polar alignment is way off, or that the object that you are calibrating on is not near the celestial equator and meridian.

Roland

-----Original Message-----
From: Seb@stro <sebastiendore1@...>
To: main@ap-gto.groups.io <main@ap-gto.groups.io>
Sent: Mon, May 3, 2021 10:42 pm
Subject: Re: [ap-gto] Spikes in DEC #guiding #guiding

Well, I'm not the one who will contest your analysis, Brian. As Howard said earlier, your advice is to be taken seriously, and I agree! 🙂 And I also agree with your argument about the guiding pulse being in only one direction and being compatible with bad PA.

The reason why I said it was good in the first place is only because PHD told me so (see attached). It wasn't based on anything other data. Hence my hypothesis about it struggling to show me the real NCP when I did the Polar Drift Align in the gusty conditions...

Anyway, AP is also working with me behind the scenes to help figure out what could have happened. So, we'll see if they can shed some light on this from their perspective.

Sébastien


De : main@ap-gto.groups.io <main@ap-gto.groups.io> de la part de Brian Valente <bvalente@...>
Envoyé : 3 mai 2021 22:55
À : main@ap-gto.groups.io <main@ap-gto.groups.io>
Objet : Re: [ap-gto] Spikes in DEC #guiding #guiding
 
Seb

When i first reviewed your PHD logs, it appeared to me your polar alignment was quite off. All your corrections were in one direction

You said you thought it was the wind, but i have my doubts about that

so it's possible your polar alignment may be misaligned for whatever reason


--
Roland Christen
Astro-Physics


Roland Christen
 

So, were you imaging with the dewshield off and unbalanced?

Rolando


-----Original Message-----
From: Seb@stro <sebastiendore1@...>
To: main@ap-gto.groups.io <main@ap-gto.groups.io>
Sent: Wed, May 5, 2021 11:31 am
Subject: Re: [ap-gto] Spikes in DEC #guiding #guiding

Hi,

For reference, I did calibrate near M3 which was the nearest I could get from the celestial equator/meridian at the time, given high trees that obstruct my sight in the south. 

But guess what, it seems Brian, Howard and Roland were right from the very beginning. (Who would have thought? Silly me...)

It seems my DEC axis was indeed in severe imbalance and my PA was off after all... Moreover, it was entirely human mistake (as it usually is in these kind of situation).

Curious to know how I found out ? Here it goes. Given all hypothesis were pointing in the same direction (DEC imbalance, PA off), one can only admit the simplest explanation is that indeed these are right somehow. That was difficult to admit for me, since I was convinced I had done everything right from the beginning (and I had, as a matter of fact). But at the end of the night (that's one clue), even PHD2 figures were shouting at me : PA was 20 arc-min off and DEC corrections were in only one direction.

So I mentally replayed the night, trying to remember the smallest and finest details. And it struck me. Remember the wind ? And me saying I had to remove the dew shield to help with that ? And there you have it ! That simple: I had REMOVED the DEW SHIELD ! That explains how my 2.3' PA went to 20.1', (even if I removed it carefully it seems - it was tightly put as it only holds with friction so I had to pull it out with some force). One down. That could also explain the imbalance but at that point, I was still skeptical it could have been "severe" because that thing is made of thin plastic and pretty lightweight (< 13oz) compared to the rest of the load. That and the fact that when I work on the setup inside, the dewshield is also OFF (but dustcap is ON and only slightly lighter). Anyway, simple experiment would confirm: scope in park 5, dewshield ON, DEC balanced, unlock the clutches, remove dew shield. See result in attached JPG. Definitely a severe imbalance...

Mystery solved (for me at least, it was a mystery) and lesson learned: once set up, don't touch the dew shield (basic, I should have known).

Thanks to Brian and all the folks at AP, you guys did challenge me enough to bring me back on the right track. BTW, I haven't said it publicly yet but as others have already said, that Mach2 is a marvel of engineering and craftsmanship. Thanks AP for making this piece of art real. That mount and the customer service that comes with it is definitely worth every penny.

Sébastien


De : main@ap-gto.groups.io <main@ap-gto.groups.io> de la part de Roland Christen via groups.io <chris1011@...>
Envoyé : 4 mai 2021 11:21
À : main@ap-gto.groups.io <main@ap-gto.groups.io>
Objet : Re: [ap-gto] Spikes in DEC #guiding #guiding
 
The fact that both RA and Dec are drifting so fast in just a few minute's time indicates either that your polar alignment is way off, or that the object that you are calibrating on is not near the celestial equator and meridian.

Roland

-----Original Message-----
From: Seb@stro <sebastiendore1@...>
To: main@ap-gto.groups.io <main@ap-gto.groups.io>
Sent: Mon, May 3, 2021 10:42 pm
Subject: Re: [ap-gto] Spikes in DEC #guiding #guiding

Well, I'm not the one who will contest your analysis, Brian. As Howard said earlier, your advice is to be taken seriously, and I agree! 🙂 And I also agree with your argument about the guiding pulse being in only one direction and being compatible with bad PA.

The reason why I said it was good in the first place is only because PHD told me so (see attached). It wasn't based on anything other data. Hence my hypothesis about it struggling to show me the real NCP when I did the Polar Drift Align in the gusty conditions...

Anyway, AP is also working with me behind the scenes to help figure out what could have happened. So, we'll see if they can shed some light on this from their perspective.

Sébastien


De : main@ap-gto.groups.io <main@ap-gto.groups.io> de la part de Brian Valente <bvalente@...>
Envoyé : 3 mai 2021 22:55
À : main@ap-gto.groups.io <main@ap-gto.groups.io>
Objet : Re: [ap-gto] Spikes in DEC #guiding #guiding
 
Seb

When i first reviewed your PHD logs, it appeared to me your polar alignment was quite off. All your corrections were in one direction

You said you thought it was the wind, but i have my doubts about that

so it's possible your polar alignment may be misaligned for whatever reason


--
Roland Christen
Astro-Physics

--
Roland Christen
Astro-Physics


Seb@stro
 

So, were you imaging with the dewshield off and unbalanced?

For some time, yes. 

I put it back at some point when winds went away (maybe an hour or two after I started), which should have restored balance, but possibly sent PA farther off at the same time.

Target (M106) was also pretty high (75degrees altitude) at the beginning of session and for a while (had just crossed the meridian when I started imaging), so at first, unbalance was possibly less an issue (OTA being mostly vertical) but worsen with time, as RA tracked into West, increasing horizontal component of the OTA. That degradation over time is also consistent with what I recall I experienced. 

Sébastien