No correlation between the master dark and the target frame

[Cleon_Wells]

Tim, uncheck the small RGB colored box in the upper left corner of the STF panel. If this has a square around it the stretch is equal leaving you with a green image, 1 R, 1 B and 2 G pixels the Bayer Matrix, cfa. For a little info on this , http://www.stark-labs.com/craig/articles/assets/Debayering_API.pdf
Cleon

[astropixel]

Hi Tim.

Deliberate dithering strategies are adopted for a variety of reasons. Firstly dithering results in a given object being imaged onto different parts of the detector and hence helps with artifact detection and suppression as well as helping to compensate for flat-field effects.

Manual dithering with the mount hand controller, if automatic dithering is not available, greatly improves image quality. Banding reduction in particular. And as quoted from Cleon's excellent text all the above benefits. Image calibration and processing in PI produces better results with DSLR images that have been dithered - in my view.

Regards,

Rowland

[pfile]

i agree, dithering helps a great deal.

 you need to make sure your dithering direction is as perpendicular to the horizontal axis of the sensor as possible though. if the long axis of the camera happens to be aligned in RA and you do RA-only dithering, your banding's not going to go away...

[astropixel]

Thanks - yes, dither in RA and DEC..

[star gazer]

So I need to move the mount 1-2 pixels between each subframe.? Doesn't turbulence in the atmosphere effectively give me some dithering. I guess this to do tho properly it would have to be done with suitable guiding software? At the moment I have no guide scope or guide camera. I am just running unguided on my Mach1gto. Guiding kit is on my wish list, as is a proper ccd camera and scope upgrade, but before I part with any cash I want to understand the limitations of what I already have. At the moment I'm having great fun with my relatively modest (not including the Mach1) investment and the results are starting to come, thanks in no small part to you guys on this forum.

Tim

[astropixel]

Hi Tim. It's more a matter of shifting the image around the sensor - 5 or 10 pixels is OK. I give the hand controller buttons a 1 second push between images. The science of dithering with high end gear is one thing, whereas, we just want to avoid stacking the same pixels one on another, masking artifacts that would otherwise be difficult to remove.