Hawklord

OK brian I think I understand.

So you could find the best exposure time for your flats inside the house one night.

Then every imaging night just take a set before packing up but at that exposure time you set whilest in the house?

Thanks

Michael

That's pretty much what I did for the larger scope. Just had to remember not to alter the focus or orientation at all. For the refractor it's a bit easier since I can use the laptop screen outside before packing up.

I'm assuming that as long as the image train is the same, that each new flat can be the same exposure as used before, with just a cursory check at the intensity level.

Cheers

Brilliant. Thanks

Hi All,

When I recently first started RGB imaging on my VC200L with flat field calibration I guessed at the exposure length for the flats. I thought that as long as they looked a bit like the ones that I had seen others using then they would be OK! However when I switched to using the refractor and calibrating with new flats they were not up to the job with vignetting in the resulting stack remaining.

Camera is the Sbig ST8300M

So, my questions are these, and apologies if the answers are obvious:

I’m told I need to aim for an ADU value of ~20,000 for my flats, is this the peak intensity (of the central portion say) or the average across the whole frame?

On loading my flats onto CCDSoft and Nebulosity it gives one an intensity (or I) value for the pixel the cursor is on (and in the case of Nebulosity, the local area and average also). Is this the same as ADU?

So can I use these programmes to tell me whether I've got the exposure about right?

All advice welcome.

Cheers

Bardo,

Thats a really nice image for your first shot . Shouldn't take too long to get back into the swing of things once the bug bites hard again.....and it will!

Cheers

Okay, so maybe Comet Holmes isn't a DSO? Here's one of M13 instead with a rather old Zeiss 300mm lens.

Comet Holmes. VC200L. EOS300D