Should my darks look like this?

[Sammyb]

Hello all - I tried taking darks for the first time the other night and they turned out like this....

I was using an Atik Titan colour camera, on a 200P Skywatcher Newtonian - placed the cover over the end of the optical tube and took 30 secs exposures.

When I add these in DSS and proces along with the lights I get an error saying only one frame will be stacked (doesn't happen when I leave out the darks).

I would have thought the "darks" should be darker!

Any help would be appreciated.

Sam

[IvanT]

I've only taken darks with my 1000d DSLR, same ISO and duration as lights (in manual mode) and my darks are black except for the odd hot pixel. Is there light getting somewhere, scope cover, camera fixing?

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[Sammyb]

Thanks for the quick reply.

I can't imagine there was light getting in. The cover was fully on the end of the tube. Its very confusing.

Sam

[IvanT]

Maybe try taking the OTA out of the loop and just cover the camera with its own cover and see if they come out the same?

Also was that the master dark you posted or a single dark? If it was the master are the individual darks black. If they are then it has to be down to the stacking I'd guess.

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[carastro]

My darks look black and it's only after stretching the master dark that I get any sort of mottling effect. Is this exactly how it came out of the camera?

carole

[RobH]

As has been said already, darks should be black with a few hot pixels.

Rob

[Stephen]

Have you tried a different USB cable? I thought I had a knackered Lu070M but turns out the cable was particularly nasty .....

[Sammyb]

Thanks for all the suggestions.

The image I showed was of a single sub.

I found there was a "auto stretch" check box ticked. So I unticked that and moved a few sliders and that way I got a black image with a few hot pixels.

Only problem now is when I tried to use these darks in DSS it made the output look terrible! The histogram was bizarre and I have trouble getting the image to look like it should.

Cheers,

Sam

[Bizibilder]

I would retake the darks - make sure they are at roughly the same temperature as your lights were taken at - you may have to wait for the cool of the evening to do it.

[IvanT]

Might be obvious but you have loaded them into DSS as darks as opposed to lights, flats, bias haven't you? Select all the darks in DSS, right click and select to register as darks. I only mention it as I've in the past loaded all the raws from my camera and missed one during the right click reflag.

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[mark7331]

I always take my darks with the camera cover on and never in the OTA because I've found that light does get in. Take them on a cloudy evening when you can't image.

[ollypenrice]

Ditto. Using a CCD with sealed electric filterwheel and a totally sealed looking lens cap (Takahashi) my darks done outside are not right. (It is very bright where I live, it must be said.) I do them with the screw-on camera chip cover at the right exposure length and temperature in, for paranoia's sake, a dark room!

I looked in disbelief at my outside darks because I was sure there could be no light leaks. But there were.

Olly