M42 -- with multiple personality disorder

[brajoh]

Like everyone, its nice to have the drought gone but there's no stars in the sky! This was the only night out I managed in november or december. (Did get to see the conjunction through the clouds for about 30 secs naked eye though!).

So one chance: M42 because its easy and less likely to lose the night due technical problems. Also wanted to test how sharp my C8 is (selling a lot of my gear and wondering if it should go).

Was a bit hesitant to post as M42 is so photographed its smile must be aching, but looking through the posts there is an incredible variety. My problem (probably artificial) is how do you people who post such great pictures choose which one to put up.

I have put up 5 out of the same data: 2 look like leggo in colouring, but at least they are colourful, contrasty and sharp looking. Don't really like them though -- too colourful, too artificial. (But I'd love to be able to bring out the bowl appearance like some of you do and I just don't seem to be able to make it jump out as 3 dimensional)
I like the starless one although it was only an intermediate step in processing. The recombined one looks more honest.
And I guess I like the one labelled beautiful most but it doesn't seem to have impact.

Any comments?
John B

23x5mins at 120x -5deg + 27x1sec at 120x -5deg
ZWO 294 MC OSC/Lum only
1200mm (C8 with 0.6FR)
HEQ5Pro
0.9x0.6deg
AAPP 0.79
Backyard Grafton, 15/11/2020

[strongmanmike]

With the crappy weather these days, it is just nice to get an image :thumbsup:

I think for the lovely colour, dynamic range and depth, No2 is my pick :thumbsup:

However, the stars look like they are suffering from coma, possibly a little astigmatism and I suspect they may have suffered at the star removal and replacement step..?

Looking less closely, it looks like a great image of M42, well done :)

Mike

[Andy01]

+1 what Mike said - sort out the stars and you'll have a great image! :)

[brajoh]

Thanks for the comments Mike.
There is drift and coma +/- astigmatism (chromatic aberration? - less severe colour in the flatter pictures) — I had the HEQ5 overloaded by weight so there was some drift, and the focal reducer certainly adds artefact (see bright star extreme right esp in the less contrasty pictures). There are also black dots in the centre of some stars — the more processing the more problems overall.

I have previously only used the C8+FR with ZWO178 (small chip small pixels) so three times the gain, 3 times the lack of sharpness (generally disappointing) cw the 4/3 chip. I tried collimating before these shots but couldnt improve it with the seeing that night (in fact didnt change it). So I was pretty surprised how much detail there was — but bigger chip, more problems in the periphery.

There's always that temptation to want other equipment and (mainly for the sake of less difference in focal point with from blue to Ha that reflecting surfaces) I was thinking about changing to a newt (but wonder how much colour problems come out of the coma corrector and would I be any better off). But got an NEQpro at Christmas so will see what I can gain with more stability and balance being less critical before I consider that.

I notice you people seem to prefer chucking out compromised shots over more exposure and weighted preprocessing. I might look at redoing it with only the round stars if there are enough in the series.

Anyway, thanks for the comments.

John B

[Peter Ward]

Telescope time is precious and while it’s hard to throw away data, better to get things like focus, tracking, collimation and camera tilt sorted…
as these are things you can control…as opposed to the weather and seeing…hence I'd suggest fixing each of them before starting any new imaging sessions.

I take the GIGO approach to my data: Garbage In Garbage Out. No amount of processing can fix vanilla data…
so unless I’ve captured ET phoning home…I toss it out.

M42 has a massive dynamic range, and is hard to do well.
Do some research..have a look at a few benchmark M42’s on the web, for a colour reference look at Malin’s AAO image. (the blue is subtle)
Accurate colour can be difficult to assess, but if you read in the image
data it's M42 with SII OIII Ha NII plus an alphabetical soup of more exotic filters,
then the colour is likely not accurate/natural. (assuming that is what you want to depict)

Exacting astrophotography while not easy, can be very rewarding when it all comes together so stick with it. :thumbsup:

[brajoh]

:)
thanks for the advice. Got to agree that the best way of getting a good photo is good negatives.
I'll certainly have a look at the Malin photo. I looked through the last couple of months posts on IIS before posting. Your comments on colour relate to what I originally posted about choosing a processing path or result so I appreciate the input.

I've uploaded two in response to the coloured stars comments, one reprocessing the old data and one with just the 9 best tracked pictures and no star processing -- yes the colour is symmetrical and worse laterally so as well as tracking there must be some astigmatism/abberation. (And yes, the noise is more of a problem with only 9 shots).

I've come out of visual Am. Astro. (as I imagine all AP's do) and so a bit of green in the orion nebula is a thrill, a bit of blue tinge to it even moreso. (And green stars just the opposite feeling!)
(Floaters got bad in the eyes so I'm swatting flies that aren't there are cursing their getting in the way of visual detail).
I'm still at the stage of "Wow, I couldn't see that with the Dob!" and a shot of something like Sh 2-27 where I can see the invisible is even more exciting.

Until very recently I've done mainly narrowband because my refractor and C8+FR both have fairly bad chromatic problems (blue is awfully dispersed on the meade) so although HOO looks far and away best colours to me, realistic colour has been/is a fiction to me.

My immediate problems are 1) balance affecting tracking (my HEQ5 seems sticky so balancing doesn't seem sensitive and it can certainly affect the tracking). 2) focussing -- my C8 and my original series MEADE 480 refractor are both so old they neither have 10:1 reductions so although I use FWHM (or whatever the abbreviation is) for focussing the mechanics are jumpy and coarse. A replacement planetary gear ($160 cheapest I can find so might as well buy a GSO focuser if I could find one that fits the meade) is enticing but maybe just holding out for a new scope when the pressure builds up (NEQ6 for christmas was necessary before could consider a newt). Leaning towards short focal length helps but I would love to get M1 and go back to Thors Helmet and a few others ...

Anyway thanks for the comments!
john b