red stripes on photos

[graham.hobart (Graham stevens)]

greetings (again)
Last week I took some lights consisting of about 40 x 3 minutes then finished off with two x 10 minutes on the same galaxy- the EXIF was about 24'c.
After calibrating with darks,flats.flat darks I have some thick red lines going top to bottom on the pics.
I din't dither these.
It was an unmodded DSLR.
? cause
Graham

[Poita (Peter)]

Can you post one of the unprocessed images?

[graham.hobart (Graham stevens)]

I can when I get home from work- they appear as feint thick red columns which get more obvious when you stretch the data.
The darks were done at the same time.
It was a very hot night so I wondered whether this was not helping.
Cheers
Graham

[rcheshire (Rowland)]

Graham. Can you try with bias only, then bias and dark, or bias and flat. No need to stack the lot, just a few subs. If you still have red lines, leave out the bias.

This should narrow down the offending calibration frame. Unlikely to be your lights.

[graham.hobart (Graham stevens)]

Thats a good idea- will try that when I get home from work- I might jsut do darks first- shorter then add the two long 10 minute dars, then add flats etc
I wonder whether 10 minutes at iso 400 at 24'c was just too noisy for the camera?

[graham.hobart (Graham stevens)]

This is just the lights with the darks (including the longer darks)

[CapturingTheNight (Greg)]

Hi Graham,
It looks like sensor noise due to the high ambient temp to me. I only ever get those same vertical lines during summer. Never when it's cold. Not sure how best to eliminate it (apart from cooling). I generally make sure I have enough data to improve the signal to noise ratio so I don't need to stretch the image to far.
Cheers
Greg

[irwjager (Ivo)]

Graham, if you get horizontal or vertical lines/banding due to read noise, try using the 'Band' module in StarTools. It works best on linear data (e.g. before the 'real' stretching). To visualise the banding, use the screen stretch functionality.

Hope that helps...

Cheers,

[rcheshire (Rowland)]

Hi Graham. I suspect too, that high ambient temp is the cause. Perhaps more darks under these conditions, of the same duration as the lights to create an effective master. The rest of the image is otherwise ok except for the dark noise. Take a pile more bias frames too, under these conditions.

How is that cooling system coming on?

Cheers

Rowland.

[graham.hobart (Graham stevens)]

There were the same number of darks as light frames taken on after the other. I suspect thermal noise too as I have just looked at my data from Tuesday night when it was between 15-13'c and I can see any stripes.
Cooler mod is too heavy for my little scope so I am back to drawing board with it!
Cheers
Graham
IVO - thanks for tip will re do with 'banding tool'

[Oscar in Bin (John)]

Graham, I have been having banding issues with my unmodified Nikon. Very bad on the night when it was Tshirts still at 3am!
I went back to some earlier light frames taken on cooler nights and stretched them very hard - sure enough found the same bands but much less noticeable. These better images were not an issue when stacked with the dark frames but the hot night images were unacceptable.
Radical fix - have ordered a CCD and will relegate the DSLR to widefield short exposure tripod images and imaging to create videos.

[mswhin63 (Malcolm)]

Hi Graeme, I too am having banding issues as well. Mine though seems to be sue to electronics hum interference as they appear to regular in the image. I tried gradient removal to no avail so am trying to see what I can do electrically for the next round. I may give Startools a go.

[rcheshire (Rowland)]

Hi Graham. Calibration should take care of the banding, which seems to be confined to adjacent edges - perhaps shift register/electronics localised heating. The rest of the image looks OK. Cropping seems the only alternative.