Jump to content


Photo

Position Error Issues


  • Please log in to reply
8 replies to this topic

#1 ColinR

ColinR

    Member

  • Beta Tester
  • 9 posts

Posted 01 March 2017 - 10:04 PM

Until recently I've been quite manual in the way I have been doing my imaging. Using TSX to slew and centre objects, MaximDL for focusing and capture, getting up throughout the night to refocus.

This week I've started trying to get semi-automated imaging up and running. Started with Sequence Generator Pro which I have found hit and miss, sometimes it'll get through most of the night without a hitch and other times it'll make it to the second target before running into a Position error in Autoslew. Thinking that it was maybe SGP having a conflict with Autoslew.

Last night I tried CCDAP which I had controlling the ASCOM driver as opposed to TSX. The first time I started a CCDAP run it ran for 20 minutes (doing a 30 panel mosaic so a lot of short runs) and then hit the third target and had a position error. I just stopped the sequence, turned off the motors and manually Homed the mount. Did this sort of thing a few more times.

Eventually I just turned the Position Error sensitivity from 1 (default) to half way (15) on both DEC and RA, pushed go and went to bed.

Checked it in the morning and it had managed to focus (FocusMax pointed to bright star and back on target) and must have had an error moments later as the first sub was ruined. I'm doing 60s exposures so I was taking about 300 throughout the night.

Having lowered the sensitivity it was actually able to auto correct for the Position Error throughout the imaging session, something it hadn't done previously. So I've got a random spattering of good and bad subs from that imaging run, about a 50% deletion rate with 60s subs.

I'm at a loss as to what's causing the issue. It doesn't seem to do it before I start actual imaging. Being on a mobile setup I've got to do all of my polar alignment stuff, create various pointing models. Even when I was setting up FocusMax (first light) it had no issues. This makes me think it is an issue with SGP or CCDAP controlling the mount via the ASCOM driver.

Spent a couple of hours these last few days trying to find information on what causes or dealing with Position Errors but I'm yet to find any information at all.

Has anyone had to deal with this? Or have any suggestions?

#2 john32712

john32712

    Member

  • Beta Tester
  • 119 posts
  • LocationFlorida USA

Posted 03 March 2017 - 04:56 AM

I don't have an answer, but I am heading down the same road you are. I have CCDAutopilot and would like to use it. But need a workaround for MLPT. How are you implementing MLPT?

 

My mount has absolute encoders so it will be interesting to see if I experience any of this....

 

BTW, if you run a sequence in Maxim, do you have any issues?

 

 

John Nemcik



#3 MarkS

MarkS

    Member

  • Beta Tester
  • 408 posts
  • LocationMelbourne, Australia

Posted 04 March 2017 - 07:45 AM

Hi Colin,

 

Are you absolutely sure of the balance? Balance is very critical, and in my experience the DDM60 can get into trouble even when I think I've got the balance good. As my payload has increased with heavier focuser, camera etc, the problem has become more acute.

 

Sequence has a feature to enable relaxation slews at given intervals during a run.These slews 'reset' the motor currents to lower values. I always use the feature, as it often prevents Position Errors. If you are periodically autofocusing during a run by slewing to a AF star, as Sequence does, this also provides the relaxation effect.

 

Maybe you should try to incorporate a similar feature if you are not using Sequence.

 

Mark



#4 ColinR

ColinR

    Member

  • Beta Tester
  • 9 posts

Posted 05 March 2017 - 12:33 AM

I don't have an answer, but I am heading down the same road you are. I have CCDAutopilot and would like to use it. But need a workaround for MLPT. How are you implementing MLPT?

 

My mount has absolute encoders so it will be interesting to see if I experience any of this....

 

BTW, if you run a sequence in Maxim, do you have any issues?

 

 

John Nemcik

 

At the moment I am only working on one target in a night so I am creating the MLPT before I start imaging. I have found that CCDAP and the ASI1600 don't go so well together when doing LRGB Imaging, same with ACP. They're both great programs BUT they have a lot of "dead time" which isn't that bad unless you're imaging at 1.6e- read noise :P

 

I've been doing it in Maxim for a long time but it does mean I need to go and focus manually (push the focus button in FocusMax) every hour. I want sleep! Apart from the lack of automation I have found MaximDL to work very well.

 

 

Hi Colin,

 

Are you absolutely sure of the balance? Balance is very critical, and in my experience the DDM60 can get into trouble even when I think I've got the balance good. As my payload has increased with heavier focuser, camera etc, the problem has become more acute.

 

Sequence has a feature to enable relaxation slews at given intervals during a run.These slews 'reset' the motor currents to lower values. I always use the feature, as it often prevents Position Errors. If you are periodically autofocusing during a run by slewing to a AF star, as Sequence does, this also provides the relaxation effect.

 

Maybe you should try to incorporate a similar feature if you are not using Sequence.

 

Mark

 

I could check the balance in different positions a bit more, I tend to balance with everything horizontal pointing at the horizon. Seems to be the most sensitive balance position. I do sometimes get the "near enough is good enough" mentality when both red lines are touching but not centred on one another. Should I be spending that extra minute or two getting them exact? I have sometimes wondered if its worth it as the focuser movement (FLI PDF) will cause slightly change the weight distribution as the night goes on.

 

The last night I set up I used Sequence and didn't have any issues thankfully. I need to refocus every hour so I guess thats a built in relaxation feature, I've never even considered using that feature though. Might see if I can setup tonight and see if another night of Sequence is largely trouble free.



#5 Jay

Jay

    Member

  • Beta Tester
  • 125 posts
  • LocationFinland

Posted 05 March 2017 - 10:16 AM

Colin,

 

There is no need to refocus manually if using Maxim DL, FocusMax and TSX. Try this, I've been using it for a long time. 

http://www.felopaul.com/

 

MaxPilote is a bit like Autopilote just better. You can (and have to) use other party software with it like Maxim DL and FocusMax. MaxPilote is very stable and it's free...

 

Jay


Edited by Jay, 05 March 2017 - 10:36 AM.


#6 tbaehnck

tbaehnck

    Member

  • Beta Tester
  • 66 posts
  • LocationNorderstedt, Germany

Posted 05 March 2017 - 09:43 PM

Jay,

Very interessting that you are using maxpilote.
I have tried in the past but maxpilote never show my fits. It shows just black, also in maxviewer. The programmer seems not to be very interested in helping with this issue.
When I open and save the fits in Pixinsight it works but not the original fits out of the cameras taken with maximdl.
Maybe you have a tip for me.
Thx and br

#7 Jay

Jay

    Member

  • Beta Tester
  • 125 posts
  • LocationFinland

Posted 06 March 2017 - 08:52 AM

Jay,

Very interessting that you are using maxpilote.
I have tried in the past but maxpilote never show my fits. It shows just black, also in maxviewer. The programmer seems not to be very interested in helping with this issue.
When I open and save the fits in Pixinsight it works but not the original fits out of the cameras taken with maximdl.
Maybe you have a tip for me.
Thx and br

 

 

Very strange problem. I'm using Maxim DL, FocusMax, TSX, AAG cloudwatcher and observatory software, and have never had any problems with the MaxPilote. The MaxWiever and MaxSelector are very nice additional features.

 

What camera do you have ? I've been using SBIG and QHY cameras and MaxPilote has been very reliable...

 

Jay


Edited by Jay, 06 March 2017 - 09:02 AM.


#8 tbaehnck

tbaehnck

    Member

  • Beta Tester
  • 66 posts
  • LocationNorderstedt, Germany

Posted 07 March 2017 - 06:02 PM

Hi Jay,

 

I have a starlight sxvr-h16 and an Atik 460exm. And also with my old Atik314L it has been the same.

I thought it is something wrong with the fits header because if I save the fits in a diffent programm again then maxpilote can show the images.

My imaging software is maximdl

 

Thomas



#9 Jay

Jay

    Member

  • Beta Tester
  • 125 posts
  • LocationFinland

Posted 08 March 2017 - 07:26 AM

Hi Thomas,

 

All I can say is that the issue is probably related to Atik drivers. Have you tried the MaxPilote Yahoo group ?. My experience when dealing with Laurent (Felopaul) has been very positive. He incorporated the "unguided" option to MaxPilote software in couple of days when I told him about ASA mounts few years ago.

 

Jay 


Edited by Jay, 08 March 2017 - 07:26 AM.





0 user(s) are reading this topic

0 members, 0 guests, 0 anonymous users