3 replies to this topic

[Keith Bentley]

I have the Stellarvue SVX102T, 2600mm, 7x36 EFW and Antlia LRGBSHO filters. When I shoot flats, whether sky or panel I get this pattern on Red, SII, and Ha. I see nothing on the filters that would explain this. Nothing I try fixes this. This is the Red. It doesn't calibrate properly. G, B, and OII are fine.

 

Edited by Keith Bentley, 21 May 2025 - 11:49 AM.

[kathyastro]

It could be the scope hardware (such as the focuser tube) vignetting the light cone.  If so, this pattern is good, because the lights will have the same pattern and the flats will allow it to be corrected.

 

It could be a problem in the light source, except that sky flats wouldn't give you the same pattern in that case.

 

Since it only happens with the red filter, that is your culprit.  Is it the same size as the other filters?  Is it the same brand?  Is it installed backwards?

Edited by kathyastro, 21 May 2025 - 12:01 PM.

[Wjeremy 15]

Are you certain all the filters don't show a similar pattern? Sometimes the auto stretch looks a bit different for each filter but if you manually stretch you'll find a similar pattern.

When you say it doesn't calibrate properly, does that mean you are getting strange gradients in the R S and H, and not in the others?

[Keith Bentley]

I'll have to do more experimenting when I have a good night. Accu weather doesn't look good tonight.