Needle and M13

Ebay has finally yielded some new tougher bolts and replacement battery for my mount so I couldn’t resist the lure of some clear skies on Sunday night. Given that it was a school night and it didn’t get dark enough until after 11, I thought I’d try and do it Roger-style with shorter exposures on my little ZWO camera (sadly I didn’t have any double glazing facing the right way for this).

As well as borrowing Roger’s approach I also borrowed one of his recent targets as I’m quite taken by the Needle Galaxy at the minute, along with M13.

Needle is a stack of 35x 20 second exposures. I had gain at 500 for this and it was very noisy and I had to process it to within an inch of it’s life to get something out of it.

M13 is a stack of 80x 7 second exposures- the same gain, but the shorter exposure/more subs seemed to help, and in comparison it fell out of the camera and processed itself (OK- I exaggerate).

Started imaging at 11:15 and done and dusted and in bed an hour later! Hopefully will get another go at this on a darker night and with more time to play…

4 Responses

  1. So, you had to process it a lot!
    So – – – !
    Still looks pretty good to me.
    Mine was 20 X 20 sec exposures, but you have to remember that the noise only goes down as the square root of the exposure time. Therefore to halve the noise I would have needed 80 X 20 sec. Diminishing returns starts to set in and Image rotation starts to become a problem then on my alt-az mount, although R5 or Deep Sky Stacker will cope with rotation.
    Which scope were you using?

    1. Cheers Roger. I was on an EQ mount, so I can go further with exposure times, although we’re getting LED streetlights on our road so it’s starting to washout a bit (the subs were bright blue to start with!! Although it could be the sky wasn’t properly dark).

      The scope is a 130mm f5 so it’s quite quick. I do like the technique- you get results much more quickly, and with a bright target like M13 it’s all there on screen whilst you’re doing it.

      1. Mine is 200mm f/10, but with the focal reducer it becomes f/5 also. So your exposure for the “Needle” is getting on for twice mine.
        Can’t remember what exposure for M13 this was:
        It wouldn’t have been very long, as I didn’t use Sharpcap those days and each exposure was done manually. It WAS 3 years ago!
        I notice I took 2 separate exposures though so you could see the core without it washing out.

        1. That’s a nice Saturn in that link!

          Yes- I’m quite a fan of Sharpcap- easy to use, but lots of features. Keep meaning to try the live stacking, as that seems a great idea in principle.

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