Light Leak in Skywatcher Evostar 80ED

[graemlourens]

Hey guys.

Just received my new Atik 460EX today.

First thing i did is try out read noise and darks.

At the darks i nearly had a heart attack, very strange gradient and i could even see dust specs.

I tried various combinations, and when i changed the filter slot in the EFW2 i noticed a different gradient - then it hit me.

So played around some more until i found out that the focuser tube has a light leak!

I guess its never noticed if you're making darks in the 'dark' but in normal light it made around 1000 difference in pixel value.

Just wanted to shout that out to you guys.

Not that anybody makes a dark library with a light leak on the ed80.

Maybe this is even normal? (the ed80 is not a highend scope)

Regards, Graem

[Uranium235]

Do your darks in a dark place (I use the cellar).... but with a 460, I dont think you should be using darks anyway (they will just introduce noise) - just use sigma clipping when you stack to get rid of the hot pixels.

[graemlourens]

Thx, i have now started making a dark library, but with camera detached from scope, and sealed with lid, no light leak possible at all like that.

As its cloudy currently i'm investing time in anything i can so building up dark & bias library is a good pass-time. When have first light with the cam, will compare processing with & without darks to see if they actually negatiely affect the stretch possibilities.

With dithering i guess hot pixels will also already be history.

Can't wait to get out with this amazing cam!

Regards, Graem

[ollypenrice]

All my Atiks have come with a metal screw on cover for the chip window. Use this to make your darks library. Doing darks on the scope is a bad idea because the cameras are ultra sensitive and will record any light that they detect, ruining the darks.

Olly

[graemlourens]

Jep Olly, i also found that to be the obvious & best solution.

I must say this camera is absolutely stunning in terms of noise. Stacking even just 10 subs (without dithering) removes the majority of noise, amazing.