Atik 460EX help

[GothAstronomer]

Hi there,
This is my first time on this forum. I have recently purchased an Atik 460EX, and have begun to image with it, having been used to using my friend's Atik 314L+. I have noticed on all the images I have so far processed a very strange effect in the background of the images when zoomed in a bit- I can't really describe it, its not exactly grainy but more crunchy, I have never experienced it before. I am obviously doing something wrong in my processing, but am not sure what! It appears in all my images, including simple stacks stretched but otherwise untouched, as well as fully processed images, and noise reduction only seems to make it worse! The effect is there in narrowband and colour images- I have attached an image as an example, it does have to be zoomed in to show the problem. I have tried adding dark frames, but haven't got around to flats yet. It appears without a moon, and through both colour and narrowband filters. Any advice would be most appreciated!
Zoe

[jcm]

Hi Zoe,

A bit of additional info might be helpful.

1. Scope - type, diameter, F ratio
2. Is your posted image a single frame or a stacked image.
3. Length of exposure.

Accurate focus? did you check this before imaging?

Does this effect show up in the FITS or TIFF files or is it just in the JPEG as
the poster below suggested.

John

[chrisjbaileyuk]

Hi Zoe

The only thing I can see in there is classic jpg 8x8 pixel block artefacts. These become very obvious as jpg quality decreases. Avoid jpg's as long as possible and use a jpg quality as high as possible when you do.

Chris

ps nice flaming star Ha by the way!