#1  
Old 24-05-2009, 03:31 PM
AlexN's Avatar
AlexN
Tunnel Vision

AlexN is offline
 
Join Date: Mar 2008
Location: Brisbane, Australia
Posts: 6,708
Sbig Self Guiding Issue..

I'm looking for thoughts from fellow SBIG self guiding users...

Recently I've had an odd issue.. The drives calibrate, however the vectors are off by 90 degrees (as seen in the attached image) However, despite successfully completing calibration, it will make corrections in the wrong direction..

In the guider subframe, it will hold the star perfectly until it starts drifting up in the field of view (which is RA).. when it moves up in the field of view, it makes a correction, moving the star further up in the FOV, it continues this until the star is gone from the field of view.

Polar alignment is accurate enough that 2 minute unguided exposures are possible at 1600mm focal length.. so I dont think that is the issue..

I notice in CCDSofts guiding settings tab, there is an input field labeled "Declination" Am I supposed to put the current declination of the telescope into this field to give the guider some idea of what corrections to make? or is something else at play here?

Any info is greatly appreciated..

Cheers..

Attached image of callibration results tab of CCDSoft.
Attached Thumbnails
Click for full-size image (self guiding issue.jpg)
29.8 KB21 views
Reply With Quote
  #2  
Old 24-05-2009, 03:44 PM
rat156's Avatar
rat156
Registered User

rat156 is offline
 
Join Date: Aug 2005
Location: Melbourne
Posts: 1,653
Hi Alex,

Your calibration is failing somehow. The only reason the vectors are off by 90deg is if the camera is 90deg to vertical. Put the camera back in so the flat part of the "D" is pointing up. Re do your calibration and check that the x and y vectors are aligned with the axes.

Cheers
Stuart
Reply With Quote
  #3  
Old 24-05-2009, 03:48 PM
Peter Ward's Avatar
Peter Ward
Galaxy hitchhiking guide

Peter Ward is offline
 
Join Date: Dec 2007
Location: The Shire
Posts: 6,627
Alex,

You have the x direction reversed (location of this setting depends on the software used...but you should find it under autoguider tab)

Less than orthogonal calibration vectors are due mount backlash.

rgds
Peter
Reply With Quote
  #4  
Old 24-05-2009, 04:04 PM
AlexN's Avatar
AlexN
Tunnel Vision

AlexN is offline
 
Join Date: Mar 2008
Location: Brisbane, Australia
Posts: 6,708
Stuart - I had the camera so the flat part of the D shape was pointing to the ground when the scope was parked.. The annoyance is It worked fine like this with my Celestron C11, however with the 8" RC it doesnt seem to work? Odd..

Peter - Yes I realized that as I posted the image here.. It was part of my trouble shooting routine on the night.. I'll be sure to rectify that before the next night out...

I'll try re-orientating the axis of the camera in the focuser until all the vectors line up... And it looks as though I'll have to do something about that backlash issue... I've been slowly correcting the backlash compensation in CCDSoft v5 to try and get the vectors orthogonal, But I fear that ultimately this is going to come down to correcting the backlash problem in the gears of the mount..

Cheers for the suggestions so far..

Alex.
Reply With Quote
  #5  
Old 24-05-2009, 04:04 PM
Bassnut's Avatar
Bassnut (Fred)
Narrowfield rules!

Bassnut is offline
 
Join Date: Nov 2006
Location: Sydney
Posts: 4,771
Other than whats been said, I dont bother with the Dec setting, although I understand it helps a bit if you enter that.
Reply With Quote
  #6  
Old 24-05-2009, 04:09 PM
AlexN's Avatar
AlexN
Tunnel Vision

AlexN is offline
 
Join Date: Mar 2008
Location: Brisbane, Australia
Posts: 6,708
Well I'll give it a go Fred, and I'll have a read on correcting backlash in the EQ6..
Reply With Quote
  #7  
Old 24-05-2009, 05:39 PM
gbeal
Registered User

gbeal is offline
 
Join Date: Oct 2004
Location: New Zealand
Posts: 4,299
Alex,
while it is ages since I even looked at CCDSoft, it was my understanding that if you have the mount "controlled" by TheSky the declination is automatically taken care of. It is with maxim anyway.
Gary
Reply With Quote
  #8  
Old 24-05-2009, 06:36 PM
Dennis
Dazzled by the Cosmos.

Dennis is offline
 
Join Date: May 2005
Location: Brisbane
Posts: 10,868
Quote:
Originally Posted by gbeal View Post
Alex,
while it is ages since I even looked at CCDSoft, it was my understanding that if you have the mount "controlled" by TheSky the declination is automatically taken care of. It is with maxim anyway.
Gary
Yes Gary – that’s right; when The Sky is controlling the mount, I have noticed that the Dec field is automatically filled in, as are the RA and DEC coordinates of the centre of the field of view in the FITs header of the saved image.

In CCDSoft, make sure that File Preferences is set to the appropriate Version of The Sky.

Cheers

Dennis
Attached Thumbnails
Click for full-size image (CCDSoft TheSky.jpg)
43.5 KB10 views
Reply With Quote
  #9  
Old 24-05-2009, 06:41 PM
Dennis
Dazzled by the Cosmos.

Dennis is offline
 
Join Date: May 2005
Location: Brisbane
Posts: 10,868
Here is the ST7 orientation from the ST7 User Manual.

Cheers

Dennis
Attached Thumbnails
Click for full-size image (ST7 Orientation.jpg)
55.2 KB14 views
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 08:05 PM.

Powered by vBulletin Version 3.8.7 | Copyright ©2000 - 2019, Jelsoft Enterprises Ltd.
Advertisement
Meade Australia
Advertisement
Lunatico Astronomical
Advertisement
Bintel
Advertisement
SkyWatcher Australia
Advertisement
OzScopes Authorised Dealer
Advertisement
NexDome Observatories
Advertisement
Celestron Australia
Advertisement
Astronomy and Electronics Centre
Advertisement