M31 in 35 minutes with Altair 183M

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turfpit
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M31 in 35 minutes with Altair 183M

#1

Post by turfpit »

_M31-35x60s-g100-bl20.jpg
_M31-35x60s-g100-bl20.jpg (433.31 KiB) Viewed 2629 times
Altair Lightwave 66ED, Planostar 0.8x flattener/reducer, Celestron AVX mount, Altair 183M camera.
SharpCap + FITS Liberator + Nebulosity + GIMP 2.10
Focus with Bahtinov mask, unguided.

35x60s, gain=100, black level=20
35 lights, 30 darks, 30 flat, 30 bias

Session terminated by cloud bands and mist, so I processed what I had. This was first session with the camera, ideally I wanted to acquire 100 light frames and experiment with longer exposure.

I noticed some dropped frames, I think I need to increase the USB slider next time.

Dave
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Re: M31 in 35 minutes with Altair 183M

#2

Post by turfpit »

SharpCap Capture screen for above image..
capture-screen.png
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Re: M31 in 35 minutes with Altair 183M

#3

Post by admin »

Dave,

just to confirm, the lower screenshot shows a single unstretched sub? Nice example of how stacking and stretching brings out fantastic detail. What would be seen as a screenshot if you'd used the 'autostretch' button on the mini historgam I wonder?

cheers,

Robin
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Re: M31 in 35 minutes with Altair 183M

#4

Post by turfpit »

Robin

Yes that is an in-progress capture of a single 60s frame - progress at botton right is 20/40.

I can load up one of the frames later, stretch it and post back. It does clearly show M31 when stretched, that is how I ensure I am 'on target'. Mini histogram stretch is very useful. I can also post up what the final stack looks like.

This where it is very disconcerting for beginners because I don't have anything visible - I trust the histogram shape and LHS offset.

Dave
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Re: M31 in 35 minutes with Altair 183M

#5

Post by turfpit »

Robin
One of the M31 frames loaded into SharpCap using the Test Camera 1 (Deep Sky). Display Histogram stretch applied to show object of interest, M31, at the centre. Without the stretch, the capture display looks like the image above.

Dave
display-histogram-stretch-demo.JPG
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Re: M31 in 35 minutes with Altair 183M

#6

Post by admin »

Thanks Dave,

I'm actually rather pleased that the auto level stretch does a pretty good job on that sort of image :)

cheers,

Robin
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Re: M31 in 35 minutes with Altair 183M

#7

Post by turfpit »

Robin

Yes, that feature alone is worth the price of the software!

When setting up for the start of the capture, I turn the gain up to around 50%. That way, combined with the stretch, I can drop the exposure to much less than the the target (60s in this case). This allows minor positional adjustments with the hand controller, usually by being able to see a bright star and adjust using that. Adjustment with the controller at 60s would not really work.

I will capture this sequence as a set of screens next time I am imaging.

Dave
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