Author Topic: M31 reprocessed  (Read 85 times)

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JohnH

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M31 reprocessed
« on: Nov 20, 2020, 18:33:32 »


This is a reprocessed version of M31, all data gathered on 3rd November.

ASI1600MM Pro.
Sharpstar 15028 HNT

LHaRGB

As an experiment I have thrown Pixinsight at it. To me, I am astonished by the amount of detail I have captured even though it is still fairly noisy and I suspect that some of the nebulosity is processing artefact.

To be fair:

1) There was a 95% illuminated Moon about 60 degrees away from M31,
2) there was a lot of blotching in the background which I have struggled to get rid of, and
2) I still do not really know what I am doing!

However, I do like to think I am getting better.

John

NoelC

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Re: M31 reprocessed
« Reply #1 on: Nov 25, 2020, 10:24:19 »
Excellent scale and a huge amount of detail there John.
Very well done getting to grips with PI (something I've not managed).

Speaking as a non-expert; I suspect the sharpening has overcooked some of the stars making them a bit hollow, and there is a distinct fabric texture around the M32 and a sort of curdled look to some of the nebulosity as if it's been over sharpened. Is it possible to back off the deconvolution a few notches?

But the detail and colour you've captured makes a very pleasing image.  Well done.
Noel
Synta mount, a bunch of telescopes and a shed (on wheels).

Roberto

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Re: M31 reprocessed
« Reply #2 on: Nov 25, 2020, 11:31:14 »
Looking very good John!  The dust lanes you have managed to extract look amazing  8)

Roberto

JohnH

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Re: M31 reprocessed
« Reply #3 on: Nov 26, 2020, 10:03:07 »
Noel and Roberto, thanks for the encouragement.

I really did throw the Pixinsight equivalent of the kitchen sink at the image to see what could be done and so I am not surprised it looks a bit overdone.

From further reading I suspect that I have been taken in by the "Focal Ratio Myth". I had been working on the basis that f2.8 meant that I needed less time per channel but it really means more but shorter exposures. So my L filter was 100 x 20 second exposures and benefited enormously when turned into a "Superluminance" by adding 30 x 40 second reds, 20 x 90 second greens, 20 x 120 second blues and 10 x 300 second Ha. However, the colour filter frames should have been a much longer total exposure.

Also, the exposure times of the colour frames was arbitrary. I have now taken the transmission curves of the filters and the Qe curve of the camera and done a back of the envelope approximation which suggests that the overall transmission across the wavelength range of the RGB filters is consistent.

It is all part of the learning curve.

John

Carole

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Re: M31 reprocessed
« Reply #4 on: Nov 26, 2020, 11:19:03 »
Now that is looking great, well done. 
Also well done for mastering Pixinsight.

Carole