Author Topic: M31 first processing  (Read 79 times)

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JohnH

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M31 first processing
« on: Nov 04, 2020, 15:24:23 »



Last night was my first try with autofocussing, it seems to be a lot better than I have been able to manage so far. There were other tweaks, I changed the separation between the reducer and the camera and added an Ha filter.

I do feel this is my best effort so far (but that isn't claiming a great deal!)

The Sharpstar 15028 is incredibly fast, this was one evening's data. I feel I overexposed the L frames at 20 seconds. I was too inconsistent with the RGB times and I have a lot to learn about guiding. This is the result of running the frames through APP on the preset values and then tinkering in Photoshop. I always just want to see what I have got. I will now have a more leisurely go with PI.

Info:
Sharpstar 15028 HNT on iOptron CEM 25P mount
Imaging camera: ZWO 1600 MM Pro, ZWO Mini Filter Wheel and Electronic Focusser.
ZWO miniguidescope with ASI 120mm

Lum: 20 seconds * 100
Red: 40 seconds * 30
Green: 90 seconds * 20
Blue: 120 seconds * 20
H Alpha: 300 seconds * 10

Temperature: -15
Gain: 143

John
« Last Edit: Nov 04, 2020, 19:24:47 by JohnH »

Carole

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Re: M31 first processing
« Reply #1 on: Nov 04, 2020, 21:43:38 »
That's come out pretty well, especially considering what stage you are in the learning process.
How fast is your Sharpstar?  i.e. what F ratio is it?

Guiding and coping with autofocus, you really are coming on.

Carole

JohnH

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Re: M31 first processing
« Reply #2 on: Nov 04, 2020, 23:13:10 »
The Sharpstar 15028 is f2.8 (150 mm aperture). That really makes focus critical which is why autofocus is such a help.

John

Carole

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Re: M31 first processing
« Reply #3 on: Nov 05, 2020, 09:13:56 »
I wonder whether you have darkened the sky background a bit too much and have lost some of the outer faint nebulosity, might be worth checking.

Carole

JohnH

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Re: M31 first processing
« Reply #4 on: Nov 05, 2020, 10:08:14 »
Thanks Carol.

I will settle down and do a proper processing run with PI soon.

I was interested to read your comments about reducers. I think someone tinkered with the telescope and moved the reducer backwards into the telescope before it was sold.

Unfortunately, the two pronged tool required to unscrew it was missing when I received it. This means I cannot remove it for the purpose of collimation (which the Google Translate manual suggests).

Also, I am not sure that the eyepiece holder is perfectly perpendicular to the reducer. I have a very pronounced dark arc on one side of all images (flats cure it but it does make imaging and deciding on exposure times more tricky).

John

NoelC

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Re: M31 first processing
« Reply #5 on: Nov 05, 2020, 13:55:41 »
John
Very nice, and a good target for that setup.
I see you are falling deep into the money pit!

I opened your image in ASTAP to take a quick look at the star diameters:

Which indicates there may be a collimation / focal plane issue (not that it's noticeable on the image).
Have you tried firing a laser down it?

Noel


Synta mount, a bunch of telescopes and a shed (on wheels).

JohnH

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Re: M31 first processing
« Reply #6 on: Nov 05, 2020, 16:25:23 »
Hi Noel,

Yes, if you mean a laser collimator.

Looking at out of focus stars collimation is not perfect although the laser hits the middle of the main mirror and returns centrally.

I think that I need to rotate the focuser and see what happens? If I look at a flat the brightest part is quite a way off centre.

Thanks,

John