Sbig Self Guiding Issue..

[AlexN]

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.

[rat156]

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

[Peter Ward]

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

[AlexN]

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.

[Bassnut]

Other than whats been said, I dont bother with the Dec setting, although I understand it helps a bit if you enter that.

[AlexN]

Well I'll give it a go Fred, and I'll have a read on correcting backlash in the EQ6..

[gbeal]

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

[Dennis]

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

[Dennis]

Here is the ST7 orientation from the ST7 User Manual.

Cheers

Dennis