What have i done wrong please.

[MARS1960]

I hope someone can help so this doesn't happen again.

It is Auriga (IC405 region) a quick stretch in PS and left it there because half the image is awful, those stars on the right seem ok, those on the left are huge in comparison.

It was taken with a modded canon 600D with a CLS clip in LP filter and a 40mm f2.8 on my CGEM, sub length was 3mins unguided.

The left side of the image is awful but i can't think why.

Thanks for any help.

 

[Shibby]

It looks like the sensor is not fully orthogonal with your lens. Hard to say what has caused this, though. Has the lens taken a knock? Was it not connected properly? (I suspect the camera wouldn't accept the lens if so). Only thing I can suggest is stopping down a bit to give yourself a more forgiving DOF and hopefully keep everything in focus.

[wimvb]

Is this a single sub, or a stacked image? If the latter, I would examine the single subs. If single subs are ok, it must be the stacking that is causing problems.

If this is a single exposure, it seems to me that your optics isn't aligned properly, as @Shibby suggested. Try imaging with another lens.

[MARS1960]

Thanks for the help guys. @wimvb I have checked single subs and they are the same, i'll try another lens tonight.  @Shibby i'll also try at f4.5 and see if it improves at all.

Cheers.

[ollypenrice]

Focus using a star located at the intersection of the 1/3 lines. (Lines parallel with the chip sides and a third of the way to the opposite side.) These intersections will give you the best average focus across the chip. It does look like tilt, I must say.

Olly

[100percent]

I'm a novice, any thought whether it is due to presence of bright stars in FOV, an effect of pixel 'well overflow' / blooming spilling onto the adjacent pixels? Option try reducing exposure time to prevent 'well overflow', increase the number of images to stack to compensate? Is anti - blooming not a feature of your sensor / camera?

Keith

[MARS1960]

Thanks guys, i had a real close look at my 40mm yesterday and there is some very slight play in the lens within the outer tube, it's tiny but it's there so i think it is tilt.

I had wobbled it about a bit and last night did a few subs on heart/soul region, the problem is still there but not as bad, probably due to my wobbling.

@100percent, i haven't had this problem before even with 15min subs using the 600D with a 70-300 lens i had, i guess it has to be that pesky 40mm i bought on ebay .

Single sub from last night, ISO800 240sec.