Problem with meridian flip #Mach2GTO #APCC


David Johnson
 

This concerns the Mach2GTO.  I'm in the northern hemisphere.  I woke up this morning, and I found out that I didn't get any data after my target passed the meridian.  Sequence Generator Pro told me that there was an error when trying to do a meridian flip, and SGP aborted the sequence, although the mount went happily along.  I did have the meridian limits set, but for the declination it was pointing to, it continued (safely) to go counterweight up without hitting the meridian limit, and that's how I found it this morning (very CW up).  I want to emphasize that I have not had this problem before, despite doing dozens, if not hundreds, of automatic meridian flips with my Mach2.  I'm going to wake up tonight and see what happens when it tries to do a meridian flip.  Meanwhile, I do have a theory on what may be the problem.  For the first time with Mach2, I'm using a camera-lens system and not an OTA.  I probably don't really need to do APPM at this scale (~23 arcseconds/pixel), but I wanted to try it and see what happens.  It mapped fine after some tweaking.  However, the error when the mount is pointing to the west was huge.  This is probably due to the fact that the lens system had a lot of cone error, given the way it's mounted.  I'll try to work on issue this tonight, but, due to the mounting system, I'll probably always have some significant cone error. 

However, it got me to wondering about what happens if SGP asks for the meridian flip, and the mount thinks, due to correction from APPM, that after the flip, the mount would actually stay on the same side as before the flip.  In other words, after the flip, the camera system would point to west of the meridian, but the mount would point to the east, due to the cone error and the correction of it for points west of the meridian.  Maybe then, the mount would not do a meridian flip, as requested by SGP?  This might be the problem I had last night.  An obvious solution is to delay the flip until the mount and camera system would both be pointing to the west, assuming it's safe, which it would be in my case.  

Anyway, I saw an extreme example last night, but it seems like this could happen with smaller cone errors and might be an issue.  The bottom line question is, what happens if software asks for a meridian flip, and, due to APPM correction, the mount (not the optical system) would still point to the east, after the meridian flip, due to cone error.  Would the mount still flip?


George
 

David,

 

Please review our video regarding setting the meridian flip when using APCC and SG Pro:

https://www.youtube.com/astrophysicscorp

 

Regards,

 

George

 

George Whitney

Astro-Physics, Inc.

Phone:  815-222-6538 (direct line)

Phone:  815-282-1513 (office)

Email:  george@...

Video Tutorials: https://www.youtube.com/astrophysicscorp 

 

From: main@ap-gto.groups.io <main@ap-gto.groups.io> On Behalf Of David Johnson
Sent: Tuesday, June 28, 2022 10:13 AM
To: main@ap-gto.groups.io
Subject: [ap-gto] Problem with meridian flip #Mach2GTO #APCC

 

This concerns the Mach2GTO.  I'm in the northern hemisphere.  I woke up this morning, and I found out that I didn't get any data after my target passed the meridian.  Sequence Generator Pro told me that there was an error when trying to do a meridian flip, and SGP aborted the sequence, although the mount went happily along.  I did have the meridian limits set, but for the declination it was pointing to, it continued (safely) to go counterweight up without hitting the meridian limit, and that's how I found it this morning (very CW up).  I want to emphasize that I have not had this problem before, despite doing dozens, if not hundreds, of automatic meridian flips with my Mach2.  I'm going to wake up tonight and see what happens when it tries to do a meridian flip.  Meanwhile, I do have a theory on what may be the problem.  For the first time with Mach2, I'm using a camera-lens system and not an OTA.  I probably don't really need to do APPM at this scale (~23 arcseconds/pixel), but I wanted to try it and see what happens.  It mapped fine after some tweaking.  However, the error when the mount is pointing to the west was huge.  This is probably due to the fact that the lens system had a lot of cone error, given the way it's mounted.  I'll try to work on issue this tonight, but, due to the mounting system, I'll probably always have some significant cone error. 

However, it got me to wondering about what happens if SGP asks for the meridian flip, and the mount thinks, due to correction from APPM, that after the flip, the mount would actually stay on the same side as before the flip.  In other words, after the flip, the camera system would point to west of the meridian, but the mount would point to the east, due to the cone error and the correction of it for points west of the meridian.  Maybe then, the mount would not do a meridian flip, as requested by SGP?  This might be the problem I had last night.  An obvious solution is to delay the flip until the mount and camera system would both be pointing to the west, assuming it's safe, which it would be in my case.  

Anyway, I saw an extreme example last night, but it seems like this could happen with smaller cone errors and might be an issue.  The bottom line question is, what happens if software asks for a meridian flip, and, due to APPM correction, the mount (not the optical system) would still point to the east, after the meridian flip, due to cone error.  Would the mount still flip?


 

HI David

>>>what happens if software asks for a meridian flip, and, due to APPM correction, the mount (not the optical system) would still point to the east, after the meridian flip, due to cone error.  Would the mount still flip?


I don't think it works that way. APPM is a tracking rate enhancement at that point, your pointing would still be dictated by your initial plate solve and tracking. 

If I think about your question generally as to potential issues around the meridian, there are bigger gremlins that could potentially cause this issue: differences in time settings between SGP and the mount for example. There is even a feature in APCC that accounts for this

In all cases, I think having a good amount of "buffer time" can be used to account for these small differences

This was covered in some detail in the SGP flip settings tutorial from AP


On Tue, Jun 28, 2022 at 8:13 AM David Johnson <dajohns37@...> wrote:
This concerns the Mach2GTO.  I'm in the northern hemisphere.  I woke up this morning, and I found out that I didn't get any data after my target passed the meridian.  Sequence Generator Pro told me that there was an error when trying to do a meridian flip, and SGP aborted the sequence, although the mount went happily along.  I did have the meridian limits set, but for the declination it was pointing to, it continued (safely) to go counterweight up without hitting the meridian limit, and that's how I found it this morning (very CW up).  I want to emphasize that I have not had this problem before, despite doing dozens, if not hundreds, of automatic meridian flips with my Mach2.  I'm going to wake up tonight and see what happens when it tries to do a meridian flip.  Meanwhile, I do have a theory on what may be the problem.  For the first time with Mach2, I'm using a camera-lens system and not an OTA.  I probably don't really need to do APPM at this scale (~23 arcseconds/pixel), but I wanted to try it and see what happens.  It mapped fine after some tweaking.  However, the error when the mount is pointing to the west was huge.  This is probably due to the fact that the lens system had a lot of cone error, given the way it's mounted.  I'll try to work on issue this tonight, but, due to the mounting system, I'll probably always have some significant cone error. 

However, it got me to wondering about what happens if SGP asks for the meridian flip, and the mount thinks, due to correction from APPM, that after the flip, the mount would actually stay on the same side as before the flip.  In other words, after the flip, the camera system would point to west of the meridian, but the mount would point to the east, due to the cone error and the correction of it for points west of the meridian.  Maybe then, the mount would not do a meridian flip, as requested by SGP?  This might be the problem I had last night.  An obvious solution is to delay the flip until the mount and camera system would both be pointing to the west, assuming it's safe, which it would be in my case.  

Anyway, I saw an extreme example last night, but it seems like this could happen with smaller cone errors and might be an issue.  The bottom line question is, what happens if software asks for a meridian flip, and, due to APPM correction, the mount (not the optical system) would still point to the east, after the meridian flip, due to cone error.  Would the mount still flip?




David Johnson
 

Thanks for the help.  I had never needed to set a delay before, but with this system, it appears to be necessary.  Worked fine for three nights in a row.  First wide-field image using the Mach2.  Result here.


Karen Christen
 

That’s a really nice result, David!

Karen

AP

 

From: main@ap-gto.groups.io <main@ap-gto.groups.io> On Behalf Of David Johnson
Sent: Saturday, July 2, 2022 10:20 AM
To: main@ap-gto.groups.io
Subject: Re: [ap-gto] Problem with meridian flip #Mach2GTO #APCC

 

Thanks for the help.  I had never needed to set a delay before, but with this system, it appears to be necessary.  Worked fine for three nights in a row.  First wide-field image using the Mach2.  Result here.


--
Karen Christen
Astro-Physics


David Johnson
 

Thanks


 

David, wow that's a great widefield image. so much detail! well done

Brian