Topics

Notified!ūüėć #mach2gto #Mach2GTO


Bill Long
 

Finally, just in time for full moon. ūüėȬ†


From: main@ap-gto.groups.io <main@ap-gto.groups.io> on behalf of Wayne Hixson via Groups.Io <wayneh9026@...>
Sent: Sunday, March 8, 2020 1:36 PM
To: main@ap-gto.groups.io <main@ap-gto.groups.io>
Subject: Re: [ap-gto] Notified!ūüėć #mach2gto #mach2gto
 
Thanks very much - the clearing is here in the northwest too!

Wayne Hixson, Stargazer


On Sunday, March 8, 2020, 12:59:13 PM PDT, Terri Zittritsch <theresamarie11@...> wrote:


On Sun, Mar 8, 2020 at 01:14 PM, Ray Gralak wrote:
You can always start APPM after twilight before it gets dark enough to image.

Depending on your camera download time and plate solve time you should be able to get 2-3 points per minute. Thus, 50 points easily in 30 minutes (25 points per side).

Thanks Ray,    Sounds like a good thing to play with on a full moon night before a little narrow band imaging.    Right now it looks like it might be clear again.    
Two days in a row after getting a new toy is unheard of.

Terri


Joseph Beyer
 

Terri,

The software is straight forward to setup and APPM gives you the option to choose one of the standard point models or modify your model as needed for your particular needs in particular sky exposures in all directions.  You can also increase or decrease the density of modeling points depending on your needs.  It's impressive software.  I created my model offline during the day which only took a couple minutes then when I got everything setup and polar aligned opened APPM and ran the model.  I use SGP/Platesolve2 to provide APPM with the data and it took about 40 minutes for 51 points.  My system may run a bit slower than some but starting early in the evening I was able to begin imaging at the same time or earlier than I did before building the model.   

I don't use plate solving anymore as the pointing is very accurate.  Someone posted that their go-tos weren't spot on and it was pointed out that sky maps often don't place some objects, particularly nebulous ones, in the center of the field.  If you look at a plate solved object on Astrobin or whatever source, choose a star or point you'd like to be directly in the center.  Pick that in CdC and slew to it - it'll be centered nearly perfectly. 

The other features of APCC - meridian limits, horizon limits, etc. are definitely worth using as well.  The ability to slew to an object in the east and start imaging with the counterweights in an "up" position makes meridian flips a thing of the past.

Have fun, it sounds like an amazing new mount.

Joe 

On Sun, Mar 8, 2020 at 12:24 PM Terri Zittritsch <theresamarie11@...> wrote:
Thanks Joe, I'll look at it.  I guess I'm not clear on how long it takes to create a model.  I thought this a long process.  If it's just a few points, then that sounds just like I do already with blind solve or two, and then plate solving targets.   Do you use a solver for your model?



Terri


uncarollo2 <chris1011@aol.com>
 

 
I polar aligned as close as I ever do with polemaster
1) Polemaster does not necessarily insure good polar alignment. Only drift alignment can reduce drift.
 
2) Having perfect polar alignment does not insure zero drift due to atmospheric refraction
 
3) doing a drift alignment can produce zero drift for both RA and Dec if you use the right method, but this zero drift will only occur in the area around the zenith. In other parts of the sky the stars do not move at sidereal rate, and will also drift slowly in Dec. This is fundamental, and no amount of polar alignment will prevent drift.
 
4) In our new keypad software we have added the King rate which reduces the RA drift in those parts of the sky where the sidereal rate is incorrect, however the King rate does not address Dec drift. We have modeling software in the new keypad which can be used to compensate for drift in both axes, and can allow unguided imaging. You can also go full model with APCC Pro, but I would recommend using that for permanent setups where you can spend some time getting a really good all-sky model.
 
Rolando 
 
 
-----Original Message-----
From: Terri Zittritsch <theresamarie11@...>
To: main <main@ap-gto.groups.io>
Sent: Sun, Mar 8, 2020 6:24 am
Subject: Re: [ap-gto] Notified!ūüėć #mach2gto #mach2gto

Hi Ray, thank you for your very fast responses.    So if I might ask another follow-on:   If I install APCC, and call the telescope from either CDC or SGPro, does it call APCC then versus the V2 driver directly?    Your comment about RA rate correction intrigues me.  I didn't realize I needed APCC to be running to get good results.   I've kept my logs from last night, but it wasn't entirely what I expected.   I polar aligned as close as I ever do with polemaster, and put the PHD2 settings so I wouldn't chase-the-seeing as they say.  I did turn off guiding at one point and ran the phd tool to evaluate drift.  There was more than I expected on RA.   Is this because I'm not running APCC?     Here is where my lack of experience with AP products fails me.   
Maybe I need to bite the bullet and install APCC.

T


Terri Zittritsch
 

On Sun, Mar 8, 2020 at 05:31 PM, uncarollo2 <chris1011@...> wrote:
1) Polemaster does not necessarily insure good polar alignment. Only drift alignment can reduce drift.
 
2) Having perfect polar alignment does not insure zero drift due to atmospheric refraction
 
3) doing a drift alignment can produce zero drift for both RA and Dec if you use the right method, but this zero drift will only occur in the area around the zenith. In other parts of the sky the stars do not move at sidereal rate, and will also drift slowly in Dec. This is fundamental, and no amount of polar alignment will prevent drift.
 
4) In our new keypad software we have added the King rate which reduces the RA drift in those parts of the sky where the sidereal rate is incorrect, however the King rate does not address Dec drift. We have modeling software in the new keypad which can be used to compensate for drift in both axes, and can allow unguided imaging. You can also go full model with APCC Pro, but I would recommend using that for permanent setups where you can spend some time getting a really good all-sky model.
 
Rolando 
 
Hi Rolando,
In looking at my graph without guiding input, the center of my RA trace drifted around 6.25 arc seconds in 11 minutes (in RA).    In DEC, the trace shows only  about 3.75 arc seconds of drift in 11 minutes.      The peak to peak of the each graph was similar, and more than 2.5 arc seconds P-P.     I sent this to you in a screen shot.   I expect this is telling me that the seeing was poor at best, based on these values.   I was still getting round stars (while actively guiding).   Such is life in Vermont under the jet stream!

I'm happy to report that I've successfully installed APCC, and set it up and at least tested it out without any clear sky.    Everything connects as it should.    Called George today, who was very helpful, to provided guidance on some of the finer points.    Now just waiting for clear skies.

Terri


uncarollo2 <chris1011@aol.com>
 

 
In looking at my graph without guiding input, the center of my RA trace drifted around 6.25 arc seconds in 11 minutes (in RA).    In DEC, the trace shows only  about 3.75 arc seconds of drift in 11 minutes.      The peak to peak of the each graph was similar, and more than 2.5 arc seconds P-P.     I sent this to you in a screen shot.   I expect this is telling me that the seeing was poor at best, based on these values.
The RA and Dec drift rates indicate fairly large Polar Alignment error. It means your Polemaster is giving you a significant PA error for whatever reason. That's why I don't rely on electronic devices for polar alignment. If you want the drift rate to be zero, then you have to do drift alignment where you twiddle with the Alt and Az adjusters until the drift rates are zero (which is the definition and goal of drift alignment). Ray Graylack's Pempro does that without muss or fuss in surprisingly short time. Once I have drift alignment zeroed in, I simply attach my right angle Polar scope, place Polaris at the correct point on the dial via the push-pull adjustment and I'm good to go from then on using only the Polar scope. Of course with guiding the drift doesn't matter, but for best performance it is good to have essentially zero drift. Yerkes observatory did it in the late 1800's and they had some pretty crude methods with that 40" refractor mount. But it was good enough to allow unguided imaging for considerable time exposures.
 
Every generation of astro-imagers has to go thru this learning process, and the fundamentals never change. The 2.5 arc sec P-P excursions are almost exactly what the seeing was for that night, so that will be the best you will get under those conditions. No way anything less than a $1million active guiding system along with high power laser for forming an artificial star will do any better.
 
By the way, your Vermont skies are not too bad. In the last week I had 1.2 arc sec FWHM resolution with no guiding (simple model in the keypad only) for 2 nights, then the seeing morphed into 7.5 arc sec FWHM stars when the trade winds picked up. Sky was crystal clear but stars looked like small shaggy dogs.
 
Rolando
 
 
-----Original Message-----
From: Terri Zittritsch <theresamarie11@...>
To: main <main@ap-gto.groups.io>
Sent: Mon, Mar 9, 2020 1:45 pm
Subject: Re: [ap-gto] Notified!ūüėć #mach2gto #mach2gto

On Sun, Mar 8, 2020 at 05:31 PM, uncarollo2 <chris1011@...> wrote:
1) Polemaster does not necessarily insure good polar alignment. Only drift alignment can reduce drift.
 
2) Having perfect polar alignment does not insure zero drift due to atmospheric refraction
 
3) doing a drift alignment can produce zero drift for both RA and Dec if you use the right method, but this zero drift will only occur in the area around the zenith. In other parts of the sky the stars do not move at sidereal rate, and will also drift slowly in Dec. This is fundamental, and no amount of polar alignment will prevent drift.
 
4) In our new keypad software we have added the King rate which reduces the RA drift in those parts of the sky where the sidereal rate is incorrect, however the King rate does not address Dec drift. We have modeling software in the new keypad which can be used to compensate for drift in both axes, and can allow unguided imaging. You can also go full model with APCC Pro, but I would recommend using that for permanent setups where you can spend some time getting a really good all-sky model.
 
Rolando 
 
Hi Rolando,
In looking at my graph without guiding input, the center of my RA trace drifted around 6.25 arc seconds in 11 minutes (in RA).    In DEC, the trace shows only  about 3.75 arc seconds of drift in 11 minutes.      The peak to peak of the each graph was similar, and more than 2.5 arc seconds P-P.     I sent this to you in a screen shot.   I expect this is telling me that the seeing was poor at best, based on these values.   I was still getting round stars (while actively guiding).   Such is life in Vermont under the jet stream!

I'm happy to report that I've successfully installed APCC, and set it up and at least tested it out without any clear sky.    Everything connects as it should.    Called George today, who was very helpful, to provided guidance on some of the finer points.    Now just waiting for clear skies.

Terri


Terri Zittritsch
 
Edited

On Tue, Mar 10, 2020 at 01:59 AM, uncarollo2 <chris1011@...> wrote:
The RA and Dec drift rates indicate fairly large Polar Alignment error. It means your Polemaster is giving you a significant PA error for whatever reason. That's why I don't rely on electronic devices for polar alignment. If you want the drift rate to be zero, then you have to do drift alignment where you twiddle with the Alt and Az adjusters until the drift rates are zero (which is the definition and goal of drift alignment). Ray Graylack's Pempro does that without muss or fuss in surprisingly short time. Once I have drift alignment zeroed in, I simply attach my right angle Polar scope, place Polaris at the correct point on the dial via the push-pull adjustment and I'm good to go from then on using only the Polar scope. Of course with guiding the drift doesn't matter, but for best performance it is good to have essentially zero drift. Yerkes observatory did it in the late 1800's and they had some pretty crude methods with that 40" refractor mount. But it was good enough to allow unguided imaging for considerable time exposures.
 
Every generation of astro-imagers has to go thru this learning process, and the fundamentals never change. The 2.5 arc sec P-P excursions are almost exactly what the seeing was for that night, so that will be the best you will get under those conditions. No way anything less than a $1million active guiding system along with high power laser for forming an artificial star will do any better.
 
By the way, your Vermont skies are not too bad. In the last week I had 1.2 arc sec FWHM resolution with no guiding (simple model in the keypad only) for 2 nights, then the seeing morphed into 7.5 arc sec FWHM stars when the trade winds picked up. Sky was crystal clear but stars looked like small shaggy dogs.
 
Rolando
Thank you again Roland for your personal time here.    I think what you're telling me is that by drift aligning, and then adjusting your polar scope to put polaris in the correct position based on the drift alignment, that you're calibrating your polar scope for refraction effects at your location.   I guess you're actually moving your reticle to match where polaris is after drift aligning.   I know Polemaster is supposed to be able to account for some refractive effect, but likely not super-accurate and just some kind of calculated estimate.    Are you also saying that for a particular location, refractive effects are constant?

If the offset due to refractive effects is constant, then maybe I can estimate in polemaster.    Right now I have no idea what this might look like (how much).   I guess maybe a drift align one night with polemaster monitor running will give me my answer.     The other complication is that I have no pier or 100% stable setup.   I wonder how much error results from using a tripod vs. a pier,  and then how much variation this causes throughout the night.    


T


uncarollo2 <chris1011@aol.com>
 

 
I wonder how much error results from using a tripod vs. a pier,  and then much variation I'll see throughout the night.    
You should be able to get polar alignment good enough and keep it so with a solid tripod. Once aligned, I have not seen a tripod change the polar alignment.
 
Good polar alignment for imaging should result in Dec drift of 1 arc sec per 10 minutes at the meridian. If you also drift align the RA at the zenith, you should then also get 1 arc sec or better drift in 10 minutes for up to 2 hours on either side of the zenith. In PHD2 you can monitor your drift using the Trend Lines. You can then make tiny adjustments to the Alt and Az while watching the trend Lines and eventually zero in on perfect PA. Do the Azimuth first until the Dec line becomes flat - ignore the RA. Then tweak the Altitude until the RA line becomes flat. Do it on an overhead star. You might have to iterate a couple of times to get both Trend lines flat for at least 5 minutes. 
 
Roland
 
 
-----Original Message-----
From: Terri Zittritsch <theresamarie11@...>
To: main <main@ap-gto.groups.io>
Sent: Tue, Mar 10, 2020 2:17 am
Subject: Re: [ap-gto] Notified!ūüėć #mach2gto #mach2gto

On Tue, Mar 10, 2020 at 01:59 AM, uncarollo2 <chris1011@...> wrote:
The RA and Dec drift rates indicate fairly large Polar Alignment error. It means your Polemaster is giving you a significant PA error for whatever reason. That's why I don't rely on electronic devices for polar alignment. If you want the drift rate to be zero, then you have to do drift alignment where you twiddle with the Alt and Az adjusters until the drift rates are zero (which is the definition and goal of drift alignment). Ray Graylack's Pempro does that without muss or fuss in surprisingly short time. Once I have drift alignment zeroed in, I simply attach my right angle Polar scope, place Polaris at the correct point on the dial via the push-pull adjustment and I'm good to go from then on using only the Polar scope. Of course with guiding the drift doesn't matter, but for best performance it is good to have essentially zero drift. Yerkes observatory did it in the late 1800's and they had some pretty crude methods with that 40" refractor mount. But it was good enough to allow unguided imaging for considerable time exposures.
 
Every generation of astro-imagers has to go thru this learning process, and the fundamentals never change. The 2.5 arc sec P-P excursions are almost exactly what the seeing was for that night, so that will be the best you will get under those conditions. No way anything less than a $1million active guiding system along with high power laser for forming an artificial star will do any better.
 
By the way, your Vermont skies are not too bad. In the last week I had 1.2 arc sec FWHM resolution with no guiding (simple model in the keypad only) for 2 nights, then the seeing morphed into 7.5 arc sec FWHM stars when the trade winds picked up. Sky was crystal clear but stars looked like small shaggy dogs.
 
Rolando
Thank you again Roland for your personal time here.    I think what you're telling me is that by drift aligning, and then adjusting your polar scope to put polaris in the correct position based on the drift alignment, that you're calibrating your polar scope for refraction effects at your location.   I guess you're actually moving your reticle to match where polaris is after drift aligning.   I know Polemaster is supposed to be able to account for some refractive effect, but likely not super-accurate and just some kind of calculated estimate.    Are you also saying that for a particular location, refractive effects are constant?

If the offset due to refractive effects is constant, then maybe I can estimate in polemaster.    Right now I have no idea what this might look like (how much).   I guess maybe a drift align one night with polemaster monitor running will give me my answer.     The other complication is that I have no pier or 100% stable setup.   I wonder how much error results from using a tripod vs. a pier,  and then much variation I'll see throughout the night.    


T


Terri Zittritsch
 

On Tue, Mar 10, 2020 at 02:44 PM, uncarollo2 <chris1011@...> wrote:
You should be able to get polar alignment good enough and keep it so with a solid tripod. Once aligned, I have not seen a tripod change the polar alignment.
 
Good polar alignment for imaging should result in Dec drift of 1 arc sec per 10 minutes at the meridian. If you also drift align the RA at the zenith, you should then also get 1 arc sec or better drift in 10 minutes for up to 2 hours on either side of the zenith. In PHD2 you can monitor your drift using the Trend Lines. You can then make tiny adjustments to the Alt and Az while watching the trend Lines and eventually zero in on perfect PA. Do the Azimuth first until the Dec line becomes flat - ignore the RA. Then tweak the Altitude until the RA line becomes flat. Do it on an overhead star. You might have to iterate a couple of times to get both Trend lines flat for at least 5 minutes. 
 
Thank you Rolando, I will give it a try next time I'm out.  You know, whenever I setup, I wonder just how stable things are.   My tripods by themselves are generally stable    But if for instance, a tripod foot settles 1mm, this can result in a 4 arc minute change in the polar pointing (referring to C. Woodhouse in the Astrophotography manual), I haven't done the calculations myself to validate this, but seems reasonable given the minuet changes required to get polar aligned (present incredibly poor accuracy aside).   Now that I've looked into it a bit, seems many people get amazingly good polar alignment results and not sure why mine is off so much (indicating as much as 5 minutes off the pole) when I am very careful in the process.     And just thinking about what it's doing, I'm not sure what could drive the inaccuracy except an incorrect refractive compensation.    In any case, some work for me to do.   Thanks again.