DSLR vertical banding. Temperature?

[big bedroom]

I've noticed over the last week or so my images have vertical banding appearing. This is a stack of 9x4 min subs taken with my Canon 450d, overstretched to show it better.

I've never noticed it before but it has been getting warmer recently and wondered if this was the cause. If so is there a sort of max ambient temperature for doing long exposures with a DSLR? Is there a way of fixing it in processing? Or is it just a case of CCD for summer and DSLR for winter!

[Psychobilly]

Are you shooting and using bias frames in the calibration/stacking process?

[big bedroom]

I've never used bias frames, will they help? That image didn't have any darks but another one I tried last week using darks was showing the same banding.

[jambouk]

http://stargazerslounge.com/topic/242207-vertical-bands-and-noise/?fromsearch=1

[Psychobilly]

When stacking in DSS  most of the time I will only use Lights,Flats and Bias...

I shoot my bias in  Tv mode with the shutter speed set to the shortest possible duration (1/8000s on my cameras) at the same ISO setting as the lights  making sure no light can enter the camera I tend to shoot 30-40...

Peter..

[big bedroom]

I'll try restacking with bias frames and see what happens. Thanks for the advice.

[big bedroom]

http://stargazerslounge.com/topic/242207-vertical-bands-and-noise/?fromsearch=1

Thanks for the link jambouk, interesting reading. Processing not my strongest point either!

[big bedroom]

I had another go, this time using 30 bias frames when stacking. It's much better, thanks for the advice.

Still overstretched, it was only 35 mins worth of subs, but definitely helped with the banding.

[Psychobilly]

Result  - It's ok for such a short stack