What's Going On with these Flat Frames

Optolong L-Ultimate Optolong UV/IR cut Acquisition Calibration Deep Sky
9 replies•237 views
Jerry Gerber avatar
Jerry Gerber avatar
These images below are flat frames taken with the Wanderer Astro Flip-Flat at a remote site, using a ZWO ASI2600MC color camera.  They seem to work fine when I calibrate my lights with them, but they do not look like the flat frames I generate at home in the morning after imaging (sky flats at home).    Anyone know why they look they way they do and if I need to be concerned, what do I do?

Flat frame with UV/IR cut filter:



With L-Ultimate narrowband filter:





With Askar Ha-Oiii filter:



With Askar Sii-Oiii filter:



Thanks for any feedback!
andrea tasselli avatar
andrea tasselli avatar
I hope you take them at night, not during daylight. Otherwise is typical with some flat panels. Whether they are still do their job properly is hard to say as you'd be shooting with a far lower background brightness at your dark site I expect and you can get away with less then pristine correction that would otherwise be in the case in significant LP settings.
Jerry Gerber avatar
Jerry Gerber avatar
andrea tasselli:
I hope you take them at night, not during daylight. Otherwise is typical with some flat panels. Whether they are still do their job properly is hard to say as you'd be shooting with a far lower background brightness at your dark site I expect and you can get away with less then pristine correction that would otherwise be in the case in significant LP settings.

Yeah, I take them at night as soon as I am finished capturing the last sub for the evening.
Quinn Groessl avatar
Quinn Groessl avatar
If they properly calibrate your lights, don’t worry about it. That’s the rule I’ve always lived by for flats.
Well Written
Tony Gondola avatar
Tony Gondola avatar
….if you are having flat panel issues you can always do sky flats and do away with an extra bit of hardware. It's the easiest way to make flats anyway, no panels, no t-shirts, just a clear blue sky. For that matter, a brightly illuminated wall indoors works well too.
Helpful Concise
Rostokko avatar
Rostokko avatar
Those seem fairly normal flats for dual-band filters…
Willem Jan Drijfhout avatar
Willem Jan Drijfhout avatar
Look pretty normal. So how do your flats look like that you take at home?
Jerry Gerber avatar
Jerry Gerber avatar
....if you are having flat panel issues you can always do sky flats and do away with an extra bit of hardware. It's the easiest way to make flats anyway, no panels, no t-shirts, just a clear blue sky. For that matter, a brightly illuminated wall indoors works well too.

Not really possible when the scope is 900 miles away.
Jerry Gerber avatar
Jerry Gerber avatar
Willem Jan Drijfhout:
Look pretty normal. So how do your flats look like that you take at home?

The flats I take at home (same camera and scope) don't have the multi color areas that the remote flats have.   Is this because of the difference between sky flats and LED flats?

Here's a flat from my backyard, using same camera and filter:



As you can see, the coloration is much more subdued.  Perhaps the sky flats are dimmer as I use 3 t-shirts over the lens.   There's also the normal vignetting that I don't see  as much in the remote LED flats.
Engaging
Willem Jan Drijfhout avatar
Willem Jan Drijfhout avatar
Don’t see anything particularly strange. Any differences can be well attributed to the different light-sources. And the resulting differences in stretching will also make for some differences in how these images look like.
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