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Trapezium and Nebulosity


noah4x4
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There is nothing exception about an easy target like M42. However, most when chasing the nebulosity completely blow out the core. What I did here was reduce exposures to 8 seconds and increase Gain (108s total, Gain 400) using 8" Evolution (no wedge or guiding) with x6.3 FR and ASI294mc.  With modern CMOS cameras, you have greater exposure/gain combinations and lesser exposure length, but longer total integration time is the knack. My image has lost a little detail in cropping and reducing resolution to fit SGL image limits. But on my 4K UHD graphics display the Trapezium is clearly defined. Again, merely 108 seconds total integration time, not even two minutes. 

 

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Hi, I fear I am missing something here - I cannot see the 4 stars of the Trapezium. I can detect where they should be.  Have they been lost in the posting of the image?

Cheers,

Mike

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Here's my very first EAA capture, back in March 2014. Now that's what I call blown out! (also poorly focused).

425443445_M42copy.png.92cc4f3585ec44fc040ddcf743314f8d.png

I have mixed feeling about M42. We see so many images that some groan 'oh no, not another M42', but it is actually our closest major star-forming region and hence supremely interesting from an astrophysical point of view. I think a lot of people get their first scope around xmas time and start off on this most obvious object, then move on (in my case it was shortly after buying a second hand 80mm achromat at Astrofest).

I recently came back to M42 and found it absolutely fascinating to see the brown obscuring dust and the halo of pink around what looks like an oyster shell with the Trapezium stars in the middle. Way more interesting that the Horsehead 😉 

In terms of keeping the Trapezium stars and the nebulosity, I've found it crucial to use anything except linear stretch (arcsinh is good), and to either keep exposures short (5s say) or if doing live LRGB imaging, to take advantage of the fact that the B in particular, and to some extent the R and G are going to deliver quite tight Trapezium stars due to their reduced transmissivity relative to L. 

cheers

Martin

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To illustrate Martin's comments. The images below are all a stack of 6 x 2sec subs, using an ultrastar and a C11 and obviously a much smaller fov. The final image is the best I could do using a linear stretch without over doing the trapezium.  I probably should have used 1 sec subs. In a zoomed in version of the image below I can just make out component E (not posted).

Mike

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Another blowout but nice detail and colour none the less, Love the contrast in different colours. I hope you dont mind but it looks like the focus might need a slight tweak, just slight, having done this myself I know how challenging it can be to get it bang on.

Edited by oldfruit
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Great capture Roel and not really very blown out.

This thread got me looking back over my most recent capture and playing around with different stretches, and this is the best I can do. I should say that this is post-hoc as in not what I observed at the scope (probably), but it is possible to have observed this at the scope in the sense that it uses exactly the same tools as are available during a live session and no other processing!

In this case an arcsinh stretch gave the greatest amount of nebulosity while retaining the Trapezium stars. 

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More saturated views are of course possible but they don't alter the nebulosity/Trapezium question.

Martin

 

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Posted (edited)

As I said, I could clearly see the four primary stars of the Trapezium on my 4K UHD screen, but in reducing the file from 18Mb to fit SGL they have, sadly, become lost. Roel has done a far better job as in his posted image he has succeeded as I can clearly see the four stars AND the beautiful nebulosity.

No disrespect, but the other images in this thread clearly show the Trapezium and the core, but no nebulosity. They look more like the faint fuzzies you see in visual astronomy. Roel and Martin jpintly get my prize for what I think is one of the hardest challenges in EEAA. Capture Trapezium plus nebulosity. 

Edited by noah4x4
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