Flats and Darks for wide field imaging?

[dugnsuz (Doug)]

Hi all,

"Flats and Darks for wide field imaging?"

Right now, I'm using a DSLR camera on an EQ mount to take widefield exposures. I take a number of 20-30 sec exps at ISO200 or 400 and stack in Registax to produce a final image.
My question is, would these images benefit from either Dark and Flat field subtraction with Registax, or perhaps just Dark field subtraction only???
Cheers
Doug

[iceman (Mike)]

I would think all images would benefit from darks and flats, it just depends how much work you want to go to.

If you're got vignetting or dust motes, the flats will help. If you're getting a lot of noise, the darks will help.

If they look ok as they are, then be happy you don't have to go to the extra trouble

[gbeal]

I am lazy, but of late have come round to doing darks, especially with exposures getting up around the 10 minutes mark (un-cooled/un-modded 20D). So yes darks are essential for this length. With 30 sec shots maybe not, try one with and one without.
With the wide field stuff though, I reckon a decent flat is as or more important, from a vignetting point of view. Again, try it. Let us know too please.

[RB (Andrew)]

Doug I agree with Mike and Gary.
Like Gary said for short exposure widefields it's more important to get those flats applied.
If you go the extra mile and apply both you will be rewarded with superior results, it's up to you how much you're willing to put into it.

Let us know how you go.

Cheers

[JohnH]

What they said - flats are required, for short exposures like this you might use the in camera NR - wastes some light gathering time but less processing to do later...

[JohnG (John)]

Don't forget in addition to your Lights, Darks and Flats, you should also take a Bias frame as well, this removes any bias or fixed offset signal which is the low level charge to the CCD or sensor, taken by covering the lens and exposing for the shortest time available on your camera.

Cheers

JohnG

[Striker (Tony)]

Depends on how fussy you want to be.

But if you want the best results you need to take Flats, Darks and Bias frames in that order of priority...flats being the most important.

Darks will be a higher on the list with longer exposures and high ISO settings.

[dugnsuz (Doug)]

Thanks all
Cheers
Doug

[dugnsuz (Doug)]

Tried taking a few sunset flats tonight without success.
Way too overexposed.
What settings do others use for flats?
? RAW format, ? lowest ISO setting, ? How long do you expose for.
? Do you convert to greyscale?
I need help
I want to get some idea before the new moon
Cheers
Doug