Fine tuning PHD2 settings for 1100 with Encoders #Guiding


Andrew J
 

We finally got a clear night and I was finally able to create a pointing model and attempt my first imaging run last night with my 1100GTO-AEL. I created about a 200 point model and setup PHD2 following some helpful advice from Brian Valente here on this forum back in July.

 

Here are my settings:

 

  • Used Guiding Assistant to set the RA/DEC MinMo by letting it run for about 5 mins
  • Set sidereal guide rate to 1x
  • Use 4 second guiding exposures
  • Set a 10 second "time lapse" between exposures
  • Use lowpass 2 algorithm on both RA and DEC
  • Set Medium aggressiveness (I used 65 for RA and 80 for DEC)
  • Don’t use backlash compensation


Although my guiding was much better than I ever got with my Mach1, I still think there might be some room for improvement. Here is the graph that I had at the end of the session that was fairly representative of what I saw earlier in the night. I tried fumbling with the MinMo and Aggressive settings to try and smooth it out a bit, but was unable to get a better result. I would welcome any recommendation on how I can improve my settings or things to try.

 

Thanks in the advance for the help

Andrew J


Roland Christen
 

First I would let the mount track and record the tracking graph with corrections turned off. That will give you a baseline of the amount of natural sky scintillation (or seeing) that your site is experiencing. You cannot guide out seeing, so that will be the best you can do on that particular night. It depends on where your setup is located, of course - the further north and near the leeward side of mountains, the worse the seeing. The further south you are, and closer to the Gulf, the steadier the seeing will be.
You need to establish a baseline so that you don't have any unrealistic expectations about achieving a certain rms guiding error. Watching the Dec axis fluctuations over a 5 minute period is the best way to see that because the Dec motor will be sitting exactly still and any fluctuations or P-P value will be caused only by the atmosphere above. Of course you don't want to do this with the model running, and also you want to disregard any drift due to polar misalignment, atmospheric refraction, etc.

Set a 10 second "time lapse" between exposures
Second, I would cut my guide exposure to between 2 and 3 seconds and drop the 10 second delay down to 2 to 3 seconds.

Rolando

-----Original Message-----
From: Andrew J <andjones132@...>
To: main@ap-gto.groups.io
Sent: Fri, Oct 8, 2021 3:25 pm
Subject: [ap-gto] Fine tuning PHD2 settings for 1100 with Encoders #Guiding

We finally got a clear night and I was finally able to create a pointing model and attempt my first imaging run last night with my 1100GTO-AEL. I created about a 200 point model and setup PHD2 following some helpful advice from Brian Valente here on this forum back in July.
 
Here are my settings:
 
  • Used Guiding Assistant to set the RA/DEC MinMo by letting it run for about 5 mins
  • Set sidereal guide rate to 1x
  • Use 4 second guiding exposures
  • Set a 10 second "time lapse" between exposures
  • Use lowpass 2 algorithm on both RA and DEC
  • Set Medium aggressiveness (I used 65 for RA and 80 for DEC)
  • Don’t use backlash compensation


Although my guiding was much better than I ever got with my Mach1, I still think there might be some room for improvement. Here is the graph that I had at the end of the session that was fairly representative of what I saw earlier in the night. I tried fumbling with the MinMo and Aggressive settings to try and smooth it out a bit, but was unable to get a better result. I would welcome any recommendation on how I can improve my settings or things to try.
 
Thanks in the advance for the help

Andrew J

--
Roland Christen
Astro-Physics


Andrew J
 

On Fri, Oct 8, 2021 at 01:39 PM, Roland Christen wrote:
ld let the mount track and record the tracking grap
Hi Roland.

Thank you for taking the time reply. I really appreciate the help. The main reason ordered the 1100 with Encoders is I was hoping my guiding would significantly improve and maybe even get to the point where could image without guiding at all.

I have change the delay to 2000ms. The 10s delay seemed like a bit long, but was willing to give it a try. 

Regarding, letting the mount track without guiding, I think that is pretty much what the PHD2 Guiding Assistant does (see screen shot). After letting it run for about 5 mins it reported a total RMS of around 0.23 arc-sec. It then recommend the MinMo of 0.20 for RA and 0.30 for DEC (never understood why these number need to be different). I tried bumping this up a bit during the night, but it didn't seem to help much.

I just was not sure if the results I was getting was just the best I should expect given my crappy skies here in Houston, or if I was just not fully dialed in. What always bugs me is to see my DEC axis jumping around. If I am polar aligned, which both PemPro and PHD2 say I am, then I would not expect much movement in my DEC, but it is jumping all over the place. I tried turning down the aggression as a lot of the gyrations look like over corrections. Maybe I just need to keep turning down the aggression in PHD to get rid of those spikes?

Andrew


 

Hi Andrew

can you please upload your guidelog for that session. I assume you followed the baseline guiding steps?

screen captures are interesting but aren't helpful for analysis

On Fri, Oct 8, 2021 at 2:43 PM Andrew J <andjones132@...> wrote:
On Fri, Oct 8, 2021 at 01:39 PM, Roland Christen wrote:
ld let the mount track and record the tracking grap
Hi Roland.

Thank you for taking the time reply. I really appreciate the help. The main reason ordered the 1100 with Encoders is I was hoping my guiding would significantly improve and maybe even get to the point where could image without guiding at all.

I have change the delay to 2000ms. The 10s delay seemed like a bit long, but was willing to give it a try. 

Regarding, letting the mount track without guiding, I think that is pretty much what the PHD2 Guiding Assistant does (see screen shot). After letting it run for about 5 mins it reported a total RMS of around 0.23 arc-sec. It then recommend the MinMo of 0.20 for RA and 0.30 for DEC (never understood why these number need to be different). I tried bumping this up a bit during the night, but it didn't seem to help much.

I just was not sure if the results I was getting was just the best I should expect given my crappy skies here in Houston, or if I was just not fully dialed in. What always bugs me is to see my DEC axis jumping around. If I am polar aligned, which both PemPro and PHD2 say I am, then I would not expect much movement in my DEC, but it is jumping all over the place. I tried turning down the aggression as a lot of the gyrations look like over corrections. Maybe I just need to keep turning down the aggression in PHD to get rid of those spikes?

Andrew



--
Brian 



Brian Valente


Terry Martin
 

"the further north and near the leeward side of mountains, the worse the seeing"

Oh ya, I can attest to that!  I am so envious when I hear of people talk about 0.3 arc/sec better or total RMS guiding.

But luckily I have a Mach2 that saves the day.

Terry


Roland Christen
 

I don't see any screen shots

Roland



-----Original Message-----
From: Andrew J <andjones132@...>
To: main@ap-gto.groups.io
Sent: Fri, Oct 8, 2021 4:43 pm
Subject: Re: [ap-gto] Fine tuning PHD2 settings for 1100 with Encoders #Guiding

On Fri, Oct 8, 2021 at 01:39 PM, Roland Christen wrote:
ld let the mount track and record the tracking grap
Hi Roland.

Thank you for taking the time reply. I really appreciate the help. The main reason ordered the 1100 with Encoders is I was hoping my guiding would significantly improve and maybe even get to the point where could image without guiding at all.

I have change the delay to 2000ms. The 10s delay seemed like a bit long, but was willing to give it a try. 

Regarding, letting the mount track without guiding, I think that is pretty much what the PHD2 Guiding Assistant does (see screen shot). After letting it run for about 5 mins it reported a total RMS of around 0.23 arc-sec. It then recommend the MinMo of 0.20 for RA and 0.30 for DEC (never understood why these number need to be different). I tried bumping this up a bit during the night, but it didn't seem to help much.

I just was not sure if the results I was getting was just the best I should expect given my crappy skies here in Houston, or if I was just not fully dialed in. What always bugs me is to see my DEC axis jumping around. If I am polar aligned, which both PemPro and PHD2 say I am, then I would not expect much movement in my DEC, but it is jumping all over the place. I tried turning down the aggression as a lot of the gyrations look like over corrections. Maybe I just need to keep turning down the aggression in PHD to get rid of those spikes?

Andrew

--
Roland Christen
Astro-Physics


Andrew J
 

Hi Brian.

Here is a link to my logs from my last imaging session. Hope they help.

https://openphdguiding.org/logs/dl/PHD2_logs_nBLW.zip
--
Andrew


Andrew J
 

Hi Roland.

It maybe that the screen shots don't show up on all clients. I can see them when logged into groups.io on my pc.

Andrew


Roland Christen
 

I would like to see a screen shot of the RA and Dec with no guide corrections. That will tell what the baseline seeing is in your area. This is the minimum that you can expect and cannot be bettered when guiding. This is fundamental in understanding of what tracking and guiding does. Without that simple test I cannot really evaluate your setup and what you can expect the rms guiding to be.

Some explanation of terms:

Seeing is simply the amount of random motion that a star exhibits due to various atmospheric effects. It is usually expressed in P-P arc seconds. Knowing that value allows setting the Min Move.

P-P is the maximum fluctuation above and below the zero point with drift component removed.

RMS is a good indicator of the amount of error that is added to the theoretical FWHM star size of your optical setup. For example if your system's theoretical resolution is 2 arc sec FWHM and the RMS is 0.5, then the star size will increase to approximately 2.5 arc sec FWHM. RMS is typically 1/4 of the P-P value.

Seeing has zero to do with light pollution or Bortle or transparency or whether you are in the country or in the middle of a large metropolis. Seeing can be superb when the sky is super hazy and you can see no stars but only bright objects like the planets and the Moon. Seeing can be particularly bad when the sky is super transparent and you can see mag7 stars with the unaided eye. Do not confuse seeing with transparency.

Rolando



-----Original Message-----
From: Andrew J <andjones132@...>
To: main@ap-gto.groups.io
Sent: Sat, Oct 9, 2021 4:00 pm
Subject: Re: [ap-gto] Fine tuning PHD2 settings for 1100 with Encoders #Guiding

Hi Roland.

It maybe that the screen shots don't show up on all clients. I can see them when logged into groups.io on my pc.

Andrew

--
Roland Christen
Astro-Physics


 

Hi Andrew

In general it looks good, but I think the main limiter for you is your min move is set too high.

You are achieving about 0.5" RMS with DEC and RA nearly identical, and it turns out your min moves are about 0.5", so you aren't going to get better unless you adjust them lower. 

Also for future reference when you upload guidelogs, it's helpful to include a calibration run and as Roland mentioned an unguided run of 10-15 minutes to see what the mount performance and seeing look like


Brian


Andrew J
 

Hi Roland.

Thank you for your feedback. I will get the screen shots with no guiding corrections after I let it run for 5 - 10 mins. Unfortunately, clouds have rolled in again and not expected to clear again until next weekend. I will revive this thread once I have the screen shots. 

Some explanation of terms:

 

Seeing is simply the amount of random motion that a star exhibits due to various atmospheric effects. It is usually expressed in P-P arc seconds. Knowing that value allows setting the Min Move.

 

P-P is the maximum fluctuation above and below the zero point with drift component removed.

 

RMS is a good indicator of the amount of error that is added to the theoretical FWHM star size of your optical setup. For example if your system's theoretical resolution is 2 arc sec FWHM and the RMS is 0.5, then the star size will increase to approximately 2.5 arc sec FWHM. RMS is typically 1/4 of the P-P value.

 

Seeing has zero to do with light pollution or Bortle or transparency or whether you are in the country or in the middle of a large metropolis. Seeing can be superb when the sky is super hazy and you can see no stars but only bright objects like the planets and the Moon. Seeing can be particularly bad when the sky is super transparent and you can see mag7 stars with the unaided eye. Do not confuse seeing with transparency.

 

 

Thank you for explanation of the termination around of Seeing . I must admit I still struggle to get my head around this. I understand the concept that we need to let PHD2 run unguided for a period of time to determine the Seeing on a given night and use that information to set the MinMo in PHD2. However, I still struggle with how to get the necessary inputs. For example, once I have an unguided PHD2 Graph, how can I determine my P-P arc seconds seeing? How can I determine what is the theoretical FWHM of my system? Once I know the P-P arc seconds seeing and my systems theoretical FWHM, how can I derive the best MinMo settings for a given imaging session? I thought all I needed was to get the Total RMS from the Guiding Assistant and the use this to determine my MinMo. That said, I have not been able to understand the relationship between the Total RMS and what PHD2 recommends as the MinMo values. Maybe once I publish the unguided screenshots you or some of the gurus here can help explain how to interpret and extract the required information from the graph and feed that information into the guiding algorithms. A explanation using screenshots I think would be really helpful (at least for me).

 

I recently acquired and setup a Unihedron SQM meter thinking it might help determine my Seeing. My best readings recently have been Naked-Eye Limiting Magnitude (NELM) of ~4.4 and Mag/sq Arcsec (MPSAS) of ~18.5, which translates into a White/City Sky Bortle value. Based on what you have said above, I interpret this to mean that all this meter will do is help me determine is my Transparency. It will not help determine my Seeing. Is this a correct interpretation?

 

I appreciate that this is not a PHD2 forum, but I trust the expertise and recommendations that I receive here over what I might find on other forums. Plus I really want to see how this applies specifically to AP mounts with encoders. I do think getting a solid understanding of these concepts can help us get the most out of our mounts.

 

 Andrew


Andrew J
 

Hi Brian.

Thank you for taking the time to review the data and for providing guidance on how to upload my guide logs in the future. Once we get some clear skies here again, I will try and aquire the necessary data. As mentioned in another post, I am still struggling to get my head around some of these key concepts even thou I have been imaging since 2016. I have read and researched this on my own the best I can, but I obviously still don't get it. I am determined to get this figured out so I can get the most out of my AP mount (and maybe help others who struggle with this as well). I gues Push Hear Dummy is still not dumbed down enough for me... :)

Andrew


Roland Christen
 


I recently acquired and setup a Unihedron SQM meter thinking it might help determine my Seeing. My best readings recently have been Naked-Eye Limiting Magnitude (NELM) of ~4.4 and Mag/sq Arcsec (MPSAS) of ~18.5, which translates into a White/City Sky Bortle value. Based on what you have said above, I interpret this to mean that all this meter will do is help me determine is my Transparency. It will not help determine my Seeing. Is this a correct interpretation?
Yes, SQM meters will not determine seeing. They determine the combination of transparency and light pollution levels. Has nothing to do with seeing.

Rolando


-----Original Message-----
From: Andrew J <andjones132@...>
To: main@ap-gto.groups.io
Sent: Mon, Oct 11, 2021 9:37 am
Subject: Re: [ap-gto] Fine tuning PHD2 settings for 1100 with Encoders #Guiding

Hi Roland.

Thank you for your feedback. I will get the screen shots with no guiding corrections after I let it run for 5 - 10 mins. Unfortunately, clouds have rolled in again and not expected to clear again until next weekend. I will revive this thread once I have the screen shots. 

Some explanation of terms:
 
Seeing is simply the amount of random motion that a star exhibits due to various atmospheric effects. It is usually expressed in P-P arc seconds. Knowing that value allows setting the Min Move.
 
P-P is the maximum fluctuation above and below the zero point with drift component removed.
 
RMS is a good indicator of the amount of error that is added to the theoretical FWHM star size of your optical setup. For example if your system's theoretical resolution is 2 arc sec FWHM and the RMS is 0.5, then the star size will increase to approximately 2.5 arc sec FWHM. RMS is typically 1/4 of the P-P value.
 
Seeing has zero to do with light pollution or Bortle or transparency or whether you are in the country or in the middle of a large metropolis. Seeing can be superb when the sky is super hazy and you can see no stars but only bright objects like the planets and the Moon. Seeing can be particularly bad when the sky is super transparent and you can see mag7 stars with the unaided eye. Do not confuse seeing with transparency.
 
 
Thank you for explanation of the termination around of Seeing . I must admit I still struggle to get my head around this. I understand the concept that we need to let PHD2 run unguided for a period of time to determine the Seeing on a given night and use that information to set the MinMo in PHD2. However, I still struggle with how to get the necessary inputs. For example, once I have an unguided PHD2 Graph, how can I determine my P-P arc seconds seeing? How can I determine what is the theoretical FWHM of my system? Once I know the P-P arc seconds seeing and my systems theoretical FWHM, how can I derive the best MinMo settings for a given imaging session? I thought all I needed was to get the Total RMS from the Guiding Assistant and the use this to determine my MinMo. That said, I have not been able to understand the relationship between the Total RMS and what PHD2 recommends as the MinMo values. Maybe once I publish the unguided screenshots you or some of the gurus here can help explain how to interpret and extract the required information from the graph and feed that information into the guiding algorithms. A explanation using screenshots I think would be really helpful (at least for me).
 
I recently acquired and setup a Unihedron SQM meter thinking it might help determine my Seeing. My best readings recently have been Naked-Eye Limiting Magnitude (NELM) of ~4.4 and Mag/sq Arcsec (MPSAS) of ~18.5, which translates into a White/City Sky Bortle value. Based on what you have said above, I interpret this to mean that all this meter will do is help me determine is my Transparency. It will not help determine my Seeing. Is this a correct interpretation?
 
I appreciate that this is not a PHD2 forum, but I trust the expertise and recommendations that I receive here over what I might find on other forums. Plus I really want to see how this applies specifically to AP mounts with encoders. I do think getting a solid understanding of these concepts can help us get the most out of our mounts.
 
 Andrew

--
Roland Christen
Astro-Physics


 

Hi Andrew

I appreciate the struggle!

There are a lot of things to know and learn and understand how they relate to each other.

You may also get a lot of conflicting advice on how to go about understanding things, which can further confuse and complicate things. 



I do want to offer a few of my observations on some questions you have:

>>>>once I have an unguided PHD2 Graph, how can I determine my P-P arc seconds seeing

The guiding assistant output will show your P-P error, the DEC error is a rough approximation of your seeing conditions. 

>>>How can I determine what is the theoretical FWHM of my system?

assuming you aren't diffraction limited (and likely you aren't), you can take very short exposure of maybe 1-3 seconds. That should give you a good indication of achievable FWHM for your system and observing conditions. You should probably use a center crop to eliminate things like backfocus and collimation. 

>>>Once I know the P-P arc seconds seeing and my systems theoretical FWHM, how can I derive the best MinMo settings for a given imaging session? I thought all I needed was to get the Total RMS from the Guiding Assistant and the use this to determine my MinMo.

The guiding assistant's purpose is to provide you with that information and make that calculation. It's a really good starting point. However, there can be some artistry involved in tuning your system. For example, as I mentioned previously I noticed your min moves showed some oscillations in your guiding, To me this usually means you can tighten up the min move and probably improve your guiding results. That's from my couple years experience with the 1600ae in extremely good seeing conditions and making plenty of mistakes trying to figure out the same thing. 

Your encoders add an additional level of simplicity and complexity: they take care of a lot of things non-encoder mounts rely on guiding to do. For you (and me) that means you have to know the ideal balance between guiding and letting the encoders do their work.  The "bump guiding" Roland has referred to in the past is a good approach for this. 

Overall, if you are looking for a set of procedures to calculate conditions and performance, and then plug in these numbers that will somehow give you more accurate min move and improved guiding, I think you will find that an exercise in frustration.Calculating theoretical settings is a lot different than watching your guiding and knowing what to look for. The PHD guiding assistant is a great starting point, and I think experience will be the path forward for evaluating and improving things.

I'm sure others will have plenty of feedback on this as well.
 
Brian


On Mon, Oct 11, 2021 at 7:50 AM Andrew J <andjones132@...> wrote:
Hi Brian.

Thank you for taking the time to review the data and for providing guidance on how to upload my guide logs in the future. Once we get some clear skies here again, I will try and aquire the necessary data. As mentioned in another post, I am still struggling to get my head around some of these key concepts even thou I have been imaging since 2016. I have read and researched this on my own the best I can, but I obviously still don't get it. I am determined to get this figured out so I can get the most out of my AP mount (and maybe help others who struggle with this as well). I gues Push Hear Dummy is still not dumbed down enough for me... :)

Andrew



--
Brian 



Brian Valente


Andrew J
 

Hi Brian.

This is really helpful!! You are right, as a software developer I keep thinking this is just an equation that needs to be solved and all I need is the right inputs. No doubt there is some "artistry" involved. That said, I do want to at least understand what the 'theoretical" settings should be and use those as my starting point.

I think in large part I am just getting hung up on the terminology. If I look at this output from PHD2 Guiding Assistant, are you saying that my P-P Arc Seconds is the Declination, Peak of 0.73 px (1.44 arc sec)? If yes, how does this help me determine what MinMo I should use as a starting point? I took this screen shot before I hit the finish button, but it came back and recomended a RA MinMo = 0.20 and a DEC MinMo = 0.30. 



As mentioned in a previous post, I did another imaging run on Saturday night and all I changed was the aggression on both axis to 0.63 or RA and 0.72 for DEC and my graph fattened out quite a bit. I was able to achive an RMS of 0.23 on one point during the night. I think by relaxing the Aggression it alllowed the encoders to "do their work".

I have been imaging from a permant setup for about 6 years now (previously with a Mach1) and guiding has always been my achillies heel. I get it close enough to get round stars, but have to admit I really don't understand it. Now that I have a mount that can track extreamly accurately, I want to make sure I am using it to its full potential. 

FYI. In case it helps. In addition to the 1100GTO mount, I am also using a  Tele-Vue NP101is. I bought this scope specifically for the 1100's "shack down cruise". I wanted a short scope to give me plenty of room for error around the Pier until I get APCC, SGP, etc. fine tuned. My primay scope is a TEC 140, but I am not putting on until I get everything working together and able I am able to have several all night imaging runs without issue. For guiding, I am use the Baader Vario Finder 10x60 along with AP's bracket to help reduce flexure. Primary camera is an ATIK 16200 and guide cam is a ZWO ASI178MM.

Andrew


Roland Christen
 

I still don't see a screen shot of the RA and Dec unguided tracking graph, so I really cannot explain to you how the results of that graph will show you what is happening. It is the key to setting the Min Move for any given night, which is really the most important setting. You want to set MinMove such that the guider loop does not chase random sky motion due to seeing. The numbers below give a clue but they cannot get you to understand the why. That is what I wanted to be able to convey to you and others who may be watching this newsgroup.

Please post a short 2 - 3 minute guide graph taken with 1 second guide exposures and corrections turned off. The easiest way to turn corrections off is to set MinMove to 20.0 for both axes. No need to do a GA or other fancy tests.

Why is it that people don't want to do this simple test? It's not hard and takes literally just minutes, but reveals everything you need to know. And i will explain it all in an annotated visual once I get your graph.

Rolando

-----Original Message-----
From: Andrew J <andjones132@...>
To: main@ap-gto.groups.io
Sent: Mon, Oct 11, 2021 2:11 pm
Subject: Re: [ap-gto] Fine tuning PHD2 settings for 1100 with Encoders #Guiding

Hi Brian.

This is really helpful!! You are right, as a software developer I keep thinking this is just an equation that needs to be solved and all I need is the right inputs. No doubt there is some "artistry" involved. That said, I do want to at least understand what the 'theoretical" settings should be and use those as my starting point.

I think in large part I am just getting hung up on the terminology. If I look at this output from PHD2 Guiding Assistant, are you saying that my P-P Arc Seconds is the Declination, Peak of 0.73 px (1.44 arc sec)? If yes, how does this help me determine what MinMo I should use as a starting point? I took this screen shot before I hit the finish button, but it came back and recomended a RA MinMo = 0.20 and a DEC MinMo = 0.30. 



As mentioned in a previous post, I did another imaging run on Saturday night and all I changed was the aggression on both axis to 0.63 or RA and 0.72 for DEC and my graph fattened out quite a bit. I was able to achive an RMS of 0.23 on one point during the night. I think by relaxing the Aggression it alllowed the encoders to "do their work".

I have been imaging from a permant setup for about 6 years now (previously with a Mach1) and guiding has always been my achillies heel. I get it close enough to get round stars, but have to admit I really don't understand it. Now that I have a mount that can track extreamly accurately, I want to make sure I am using it to its full potential. 

FYI. In case it helps. In addition to the 1100GTO mount, I am also using a  Tele-Vue NP101is. I bought this scope specifically for the 1100's "shack down cruise". I wanted a short scope to give me plenty of room for error around the Pier until I get APCC, SGP, etc. fine tuned. My primay scope is a TEC 140, but I am not putting on until I get everything working together and able I am able to have several all night imaging runs without issue. For guiding, I am use the Baader Vario Finder 10x60 along with AP's bracket to help reduce flexure. Primary camera is an ATIK 16200 and guide cam is a ZWO ASI178MM.

Andrew

--
Roland Christen
Astro-Physics


Andrew J
 

Thanks Roland. As soon as I get clear skies again I will post a screen shot of the unguided tracking graph. 

Andrew


Roland Christen
 

Just a few minutes is all I need.

Roland

-----Original Message-----
From: Andrew J <andjones132@...>
To: main@ap-gto.groups.io
Sent: Mon, Oct 11, 2021 5:49 pm
Subject: Re: [ap-gto] Fine tuning PHD2 settings for 1100 with Encoders #Guiding

Thanks Roland. As soon as I get clear skies again I will post a screen shot of the unguided tracking graph. 

Andrew

--
Roland Christen
Astro-Physics


 

>>>If I look at this output from PHD2 Guiding Assistant, are you saying that my P-P Arc Seconds is the Declination, Peak of 0.73 px (1.44 arc sec)? 

Yes, but p-p can be (and probably is) misleading. if you have a wind gust, bump the mount, cable snag, etc. it could end up artificially increasing p-p when in fact it's not meaningful at all. 
 
>>>If yes, how does this help me determine what MinMo I should use as a starting point? I took this screen shot before I hit the finish button, but it came back and recomended a RA MinMo = 0.20 and a DEC MinMo = 0.30.

It doesn't really. you shouldn't be trying to figure out the min move, that's the whole point of the guiding assistant: to establish min move values (it does other stuff but this is its main purpose). 

i'll have to go back and talk with Bruce (author of PHD) on exactly how he calculates the min moves, but i suspect it's the high frequency RMS values he looks at (look at your screen in upper right)


Brian



On Mon, Oct 11, 2021 at 12:11 PM Andrew J <andjones132@...> wrote:
Hi Brian.

This is really helpful!! You are right, as a software developer I keep thinking this is just an equation that needs to be solved and all I need is the right inputs. No doubt there is some "artistry" involved. That said, I do want to at least understand what the 'theoretical" settings should be and use those as my starting point.

I think in large part I am just getting hung up on the terminology. If I look at this output from PHD2 Guiding Assistant, are you saying that my P-P Arc Seconds is the Declination, Peak of 0.73 px (1.44 arc sec)? If yes, how does this help me determine what MinMo I should use as a starting point? I took this screen shot before I hit the finish button, but it came back and recomended a RA MinMo = 0.20 and a DEC MinMo = 0.30. 



As mentioned in a previous post, I did another imaging run on Saturday night and all I changed was the aggression on both axis to 0.63 or RA and 0.72 for DEC and my graph fattened out quite a bit. I was able to achive an RMS of 0.23 on one point during the night. I think by relaxing the Aggression it alllowed the encoders to "do their work".

I have been imaging from a permant setup for about 6 years now (previously with a Mach1) and guiding has always been my achillies heel. I get it close enough to get round stars, but have to admit I really don't understand it. Now that I have a mount that can track extreamly accurately, I want to make sure I am using it to its full potential. 

FYI. In case it helps. In addition to the 1100GTO mount, I am also using a  Tele-Vue NP101is. I bought this scope specifically for the 1100's "shack down cruise". I wanted a short scope to give me plenty of room for error around the Pier until I get APCC, SGP, etc. fine tuned. My primay scope is a TEC 140, but I am not putting on until I get everything working together and able I am able to have several all night imaging runs without issue. For guiding, I am use the Baader Vario Finder 10x60 along with AP's bracket to help reduce flexure. Primary camera is an ATIK 16200 and guide cam is a ZWO ASI178MM.

Andrew



--
Brian 



Brian Valente


Andrew J
 

FYI. Bruce Waddington just did a presentation on TAIC on PHD2's Guiding Assistance.

https://youtu.be/LbhxX7PH2CE