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Dark Frames with a Filter Wheel

Tinker1947

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Tinker1947

Tinker1947

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Yes, I do. Actually, I've taped a piece of flocking material across and it seems to work really well (better than capping the scope which was my previous approach). It also means I can keep the dew/light shield on all the time as I don't need to cap off the secondary end of the scope.

Martin

This is how i may end up doing it, the spare cheap filter is to thick to use......

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davew

davew

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I've found that the best darks I can do are indoors, lights off and with the camera capped. I would suggest you try all three methods. Using a filter blank is surely the easiest and one of the few ways for remote imaging. Covering the end of the scope is great so long as the rest of the scope and camera are in a dark spot as they may well be in an Obsy.

I set up each time I image so am never in the dark !

I have seen photos of one American imager who wraps his camera in silver foil to keep out the light. Be careful you don't cover the vents !

Dave.

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ollypenrice

ollypenrice

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I always just do them at night in the closed-off observatory which is very dark. (There are plenty of non-imaging nights!)  I keep the dust cap on, but the mechanical shutter and body of my QSI camera seem pretty light-tight anyway. 

Adrian  

With a mechanical shutter you're fine, I think.

Olly

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Tinker1947

Tinker1947

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I don't do them on the scope. I do them with the camera out and the metal chip window cover screwed on. I always get slight light leakage if I do them any other way. Newts in particular will let light in from the bottom, too.

Olly

I run the 414EX at -15c will it make any difference using dark's i can do them on a cloudy night if there are required... 

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ollypenrice

ollypenrice

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I run the 414EX at -15c will it make any difference using dark's i can do them on a cloudy night if there are required... 

You can do your darks any time at the same temperature provided all light is excluded. On that chip do you need them? Possibly not. Dither should give you perfectly clean subs.

Olly

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Tinker1947

Tinker1947

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You can do your darks any time at the same temperature provided all light is excluded. On that chip do you need them? Possibly not. Dither should give you perfectly clean subs.

Olly

"Dither" This i'm not sure about, not seen it mentioned in the Atik software and i'm not that far into SGP if it has it.......i use PHD2 with a Lodestar/ST-80 if it's in there.......

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swag72

swag72

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I would always use darks - Or at the very least run a test to see if they give you cleaner subs. Here's my thinking....

My QSI690 (Sony chip) had a glow issue at long exposures. The way to get rid of it was to do darks.... which I did. Having always used Sony chipped cameras, where we always read that darks are unnecessary, I'd never taken them before.

I was very surprised to see that using them gave me a cleaner image with which to work. So I'd say for the sake of a nights work, they are worth taking, if only to experiment and see whether they do indeed make a difference. 

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Tinker1947

Tinker1947

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I would always use darks - Or at the very least run a test to see if they give you cleaner subs. Here's my thinking....

My QSI690 (Sony chip) had a glow issue at long exposures. The way to get rid of it was to do darks.... which I did. Having always used Sony chipped cameras, where we always read that darks are unnecessary, I'd never taken them before.

I was very surprised to see that using them gave me a cleaner image with which to work. So I'd say for the sake of a nights work, they are worth taking, if only to experiment and see whether they do indeed make a difference. t looks like rain this evening so i will

It looks like rain this evening so i will run off all the Sub times i have found useful for different types of images......

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johnrt

johnrt

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I only really use them for images taken in the summer when my camera can't get below -10. It's camera off OTA, screw in cap on in a dark place (the fridge is good during daylight hours :grin: ).

I have found they don't make any difference in the spring / autumn / winter when I can get my 460ex to cool to -20C.

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carastro

carastro

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Darks and Bias can be used for any filter, but you are supposed to take different flats for each filter, though you can get away with the same flats for each filter if the filters are dust free and you have a closed FW (i.e. no gaps for dust to get in).  Olly taught me this, though I have never really been quite brave enough to not take flats for each filter "just in case".

Carole 

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Tinker1947

Tinker1947

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I don't do them on the scope. I do them with the camera out and the metal chip window cover screwed on. I always get slight light leakage if I do them any other way. Newts in particular will let light in from the bottom, too.

Olly

Now i put the cap on, swung the newt round so the primary end pointed at a blank wall, no light on in the Obby, its dark, the only light is the PC Screen on night vision this is sideways to the Newt, still had a shadow on the longer dark files, got the CCD indoors set-up with a cover screwed in, 10 minute dark perfect when stretched....thank you....

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ollypenrice

ollypenrice

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Do darks flats and bias frames need to be taken for each filter or would they work fine without any filter?

Try it and see. I usually find I can get away with a luminance flat for all my filters. If this works for you, rejoice. If it doesn't, shoot flats per filter.

Olly

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ollypenrice

ollypenrice

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On the way to take flats, i have seen mentioned a flash gun with i assume a white cotton sheet over the front of the scope, is this a good way to do them......

Who can say? If they work they work. I can't even say what works for me, because sometimes they work and sometimes they don't. Flats are a lot of fun...

Olly

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swag72

swag72

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I think the key is to experiment with what works for you. People use all sorts of ways to take flats...... I just point my scope to my white obs wall with the roof closed and adjust the light by having the door open more or less..... As simple as that!

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