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M13 - longer or shorter subs?


earth titan
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I'm trying to get as much of the core detail as I can with M13. I think it's the most enigmatic object in the night sky!

So what's the opinion? Shorter subs to get the detail or longer?

The image last night was 200 second subs. What do people think?

This is the luminance only.

post-6511-0-41580800-1368390076_thumb.jp

Edited by earth titan
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I read in this or was it last months sky at night magazine a feature for imaging M13.They said to capture the core and outer stars you need to do two sets of subs longer ones for the outer stars and the other set at a shorter exposure to capture the core stars.The length of time for the exposures will depend upon your set up then use a layer based editor to combine them.I have never done this myself but I think next time I will give it a go.I recently did M13 at 180secs with the atik 314L+ and ed80 with reducer

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I had a bit of a trawl through a couple of weeks ago on exactly that question. Peter Shah's M13 was the sort of look I was after and he shot up to 10min subs in a much faster scope than me, so I figured I could run to at least 10min without blowing the colour. I shot RGB only, no L but 10min subs per colour at f/5. Imonitored the max pixel value and didn't get anything over 60k, so I think I could have gone longer still. It's not as good as Peter's but I am quite happy with how it turned out http://stargazerslounge.com/topic/185317-m13-rgb/

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Yes, you definitely need quite short exposures to avoid burning out the brighter stars. I find I need of the order of a minute or so with my 314L+ at f5.3 depending on the actual star brightness. I check the ADU value of the brightest star in Artemis Capture and adjust exposure to get this just under 65535, the white limit. And I agree that with many DSOs you really need two sets of subs per filter to cover the dynamic range involved. I find I'm doing this more and more as I get experience - there is so much to learn and I've still got a long way to go.

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