#1  
Old 06-05-2010, 08:22 PM
Moon's Avatar
Moon (James)
This sentence is false

Moon is offline
 
Join Date: Oct 2008
Location: Melbourne
Posts: 1,147
Guiding in Maxim DL

I'd be interested to know what you make of this graph. To me it looks like it's waiting too long before sending a correction. When it sends the correction, it get gets very close but starts drifting again.

What to do - reduce the minimum move x / y? Any other ideas?

(the scale is in pixels and the guide exposures are 8 sec duration)

James
Attached Thumbnails
Click for full-size image (Guide.JPG)
45.9 KB86 views
Click for full-size image (guide2.JPG)
40.3 KB72 views
Reply With Quote
  #2  
Old 06-05-2010, 08:27 PM
Octane's Avatar
Octane (Humayun)
IIS Member #671

Octane is offline
 
Join Date: Dec 2005
Location: Canberra
Posts: 11,159
James,

I could be wrong, but, I think, unless you have a high-quality Astro-Physics or Paramount, 8 seconds may be a bit long for guide exposure duration.

Try dropping down to 2-2.5 and re-check?

H
Reply With Quote
  #3  
Old 06-05-2010, 08:54 PM
Moon's Avatar
Moon (James)
This sentence is false

Moon is offline
 
Join Date: Oct 2008
Location: Melbourne
Posts: 1,147
H
Lucky me I have one of those mounts :-)
I picked 8 sec because I want to try guiding through the HA filter. I found at 8 secs it doesn't loose the guide star, which is good. But your right, I should try it with a faster guide rate and see what happens.
I need to figure out how to view the log of corrections maxim actually sends to the mount...

Found it! I need to make it send more corrections to the mount..

Track Log Started at UT 2010-05-06 10:47:28
UT Time, Star X, Star Y, OffsetX, OffsetY, Corr X, Corr Y, Bright
10:47:37, 14.84, 161.38, -1.16, -3.62, 0.00, -1.00, 1689
10:47:50, 15.08, 163.64, -0.92, -1.36, 0.00, -0.43, 1835
10:48:02, 15.47, 164.57, -0.53, -0.43, 0.00, 0.00, 58209
10:48:12, 15.65, 164.47, -0.35, -0.53, 0.00, 0.00, 58209
10:48:20, 15.55, 164.33, -0.45, -0.67, 0.00, -0.21, 58209
10:48:32, 15.89, 164.54, -0.11, -0.46, 0.00, 0.00, 58209
10:48:41, 15.90, 164.31, -0.10, -0.69, 0.00, -0.21, 58209
10:48:53, 16.39, 164.86, 0.39, -0.14, 0.00, 0.00, 58119
10:49:02, 16.54, 164.80, 0.54, -0.20, 0.00, 0.00, 58119
10:49:11, 16.82, 165.04, 0.82, 0.04, 0.00, 0.00, 58119
10:49:20, 16.66, 164.89, 0.66, -0.11, 0.00, 0.00, 58119
10:49:29, 16.72, 164.70, 0.72, -0.30, 0.00, 0.00, 58119
10:49:37, 16.87, 164.46, 0.87, -0.54, 0.00, 0.00, 58101
10:49:46, 17.06, 164.42, 1.06, -0.58, 0.00, 0.00, 58101
10:49:55, 17.18, 164.28, 1.18, -0.72, 0.21, -0.20, 58101
10:50:10, 16.57, 164.90, 0.57, -0.10, 0.00, 0.00, 58119
10:50:19, 16.72, 165.00, 0.72, -0.00, 0.00, 0.00, 58119
10:50:27, 16.80, 164.63, 0.80, -0.37, 0.00, 0.00, 58101
10:50:36, 16.71, 164.42, 0.71, -0.58, 0.00, 0.00, 58101
10:50:45, 16.86, 164.52, 0.86, -0.48, 0.00, 0.00, 58101
10:50:54, 17.23, 164.38, 1.23, -0.62, 0.22, 0.00, 57926
10:51:07, 16.50, 164.76, 0.50, -0.24, 0.00, 0.00, 58119
10:51:16, 16.47, 164.56, 0.47, -0.44, 0.00, 0.00, 58119
10:51:25, 16.63, 164.68, 0.63, -0.32, 0.00, 0.00, 58119
10:51:34, 16.67, 164.60, 0.67, -0.40, 0.00, 0.00, 58119
10:51:43, 16.89, 164.75, 0.89, -0.25, 0.00, 0.00, 58119
10:51:51, 17.16, 164.52, 1.16, -0.48, 0.21, 0.00, 58101
Reply With Quote
  #4  
Old 09-05-2010, 01:50 AM
jase (Jason)
Registered User

jase is offline
 
Join Date: Sep 2006
Location: Melbourne, Victoria
Posts: 3,916
James, is it a problem?

The graph looks like its -/+ 0.6 pixels, perhaps higher as it reaches the 1080 milestone. You've not provided your imaging train arcsec/pixel combination, but even then I can't see it as being an issue given you're probably being governed by seeing or other factors. I'm assuming you've trained PEC.

If you're attempting to guide through the Ha filter, make sure you bin 2x2 the guide chip to improve its sensitivity. May throw the arcsec/pixel combination out as opposed to the imaging chip, but with MaximDL's intelligence when it comes to monitoring the guide star centroid, it won't be an issue (sub pixel).
Reply With Quote
  #5  
Old 09-05-2010, 08:14 AM
Bassnut's Avatar
Bassnut (Fred)
Narrowfield rules!

Bassnut is offline
 
Join Date: Nov 2006
Location: Torquay
Posts: 5,064
looks to me like polar align is out X (RA?). drifting and then over correcting or backlash. Or, its tring to correct all the time, but youve turned agressivness down to minimise backlash, and its not correcting enough between backlash events.

same possibly on Y, not correcting agressively enough with some backlash, or its drifting so fast the corrections cant get it to the centerline (mostly).

All this depends on your image scale, you might not actually have a problem.

8 secs is OK on a stable mount with good PEC.
Reply With Quote
  #6  
Old 09-05-2010, 08:26 AM
Moon's Avatar
Moon (James)
This sentence is false

Moon is offline
 
Join Date: Oct 2008
Location: Melbourne
Posts: 1,147
Have a look at the attached graph - this is the running total of the corrections issued.
It seems all the corrections are for drift - I don't have a problem with that. (I didn't have tpoint on at the time)

To me it looks like maxim only issue a correction when the error has reached some threshold - how do I change the threshold number? I'm looking for a setting such as 'only issue a correction when the error is greater than xxx pixels / arc sec".

The scope is 1,625mm / f/8 with STL11k.

James
Attached Thumbnails
Click for full-size image (Graph.png)
46.0 KB25 views
Reply With Quote
  #7  
Old 09-05-2010, 08:33 AM
Bassnut's Avatar
Bassnut (Fred)
Narrowfield rules!

Bassnut is offline
 
Join Date: Nov 2006
Location: Torquay
Posts: 5,064
whats the image scale of the guiding?
Reply With Quote
  #8  
Old 09-05-2010, 09:07 AM
Moon's Avatar
Moon (James)
This sentence is false

Moon is offline
 
Join Date: Oct 2008
Location: Melbourne
Posts: 1,147
If my maths is right, the guide chip is 0.95 arc sec/pixel.

In PHD the setting is called 'Min. motion (pixel)'. (I still have my Maxim DL learner plates on....)
Attached Thumbnails
Click for full-size image (phd.png)
17.7 KB34 views
Reply With Quote
  #9  
Old 09-05-2010, 09:59 AM
Bassnut's Avatar
Bassnut (Fred)
Narrowfield rules!

Bassnut is offline
 
Join Date: Nov 2006
Location: Torquay
Posts: 5,064
Well then the guidings pretty good anyway (I assume you took guide binning into account).
In yr second pic, on the advanced tab, I have yet to work out if min move is "dont move untill the correction required exceeds this" or "make any move no less than this", but the min move value does make a difference, I use 0.1secs, fiddle with it and see what happens.

If thats not the problem, then I recon you should be cranking up the agressiveness tho, to at least get corrections around the centreline.
Reply With Quote
  #10  
Old 10-05-2010, 12:43 AM
Octane's Avatar
Octane (Humayun)
IIS Member #671

Octane is offline
 
Join Date: Dec 2005
Location: Canberra
Posts: 11,159
Fred,

The minimum move value is a sub-pixel value. So, in your case, your setting of "0.1" -- if movement > 0.1 pixels; then make adjustment.

H
Reply With Quote
Reply

Bookmarks

Thread Tools
Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT +10. The time is now 03:06 AM.

Powered by vBulletin Version 3.8.7 | Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
Advertisement
Bintel
Advertisement
Testar
Advertisement