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Imaging with mono CCD and filters


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Hi,

Tonight's the night - all filters have arrived, extensions and filter wheel connected. Predicted clear - lets hope!

I'm going to image M27, as thats my comparison between DSLR and CCD. 

Now, would people suggest binning the RGB 2x2? Or starting off at 1x1 for all LRGB? 

What length of exposure is a worthwhile starting point ? 

I hope to be able to get guided 5 minute subs for luminance. If i get 5 minute luminance subs, what length should my 2x2 colour subs be? A quarter the length because its 4x as sensitive? I was never any good at maths...

I know as many as possible is always best, but if i aim for an hours luminance and 20 minutes each of RGB is that a good start?

So thats 12 x 5 minute luminance at 1x1... each colour = 20 x 75 sec at 2x2?

Cheers

Joe

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With my Atik 314L+ I rarely go longer than 3 minutes lately. If the camera has low read noise and dark current is nearly not a problem with good cooling then shorter exposures won't suffer while tracking errors or satellites won't be much of a problem.

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According to Olly it's a folly to bin RGB  :grin: perhaps he'll spot this and insert his 2p worth, having said that I still do it.

Dave

You can bin the RGB ( provided that the imaging scale is up to it )  but then you need unbinned Lum. If the RGB is not binned and with long enough exposure you maybe able to do away with LUM. There is a technique of getting the Synth Lum out of unbinned RGB but I for the love of god can not remember how to it.

A.G

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You can't decide on binning or not binning till you know the pixel scale and if binned is giving I.77" p/p then go for it. If there is any doubt about the seeing or guiding then I'd bin the L as well since 1.77" is a respectable resolution anyway. (It's about what I get from the TEC140/Atik 11000 unbinned, for instance.)

I would make your subs as long as the skyglow will allow. That's a matter of experimenting. There is a lot of faint stuff around M27 which will respond to the longest subs possible.

If you don't use Lum you miss out on the whole point of LRGB which is the speed brought to the table by the L filter which captures all colours at once. On my rigs I find it about 4x faster than synthetic lum from RGB though simple theory would put it more like 3x faster. Even so...

Olly

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