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The Glorious Orion and Rosette Nebulae


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Well, after posting about my rather feeble attempt at M31 using a spotting 'scope, I've now acquired a proper astronomical 'scope and I've been keenly awaiting the arrival of Orion so that I could have a try at imaging the glorious M42. Being so bright, it represented a rather easier challenge than many.

This is with a Fuji X-T1 through an Altair 102mm f/7 Super ED, all mounted on a humble Nexstar 6/8SE mount, 19 January 2016. About 100 x 15s subs, 1600ASA, stacked in DSS and processed in Star Tools. I took about 100 darks and 60 bias frames (no flats), but I forgot to do these at the time so they were done early the following morning, after leaving the camera out to cool in the still frosty morning. Given that this is my first proper DSO image and that I'm still trying to figure out how both DSS and ST work, I'm pretty pleased with the outcome. Even with a 15 second exposure the core is blown out, so it'd be nice to get some more data with shorter exposure. Also some banding is visible if I push the processing a bit to bring out more nebulosity than shown here, which I guess might be to do with not taking the darks at the time of the original exposure?

I then moved a little to the east and had a go at the Rosette nebula. As above, but 130 x 10s subs. I think it needs rather more data though.

Incidentally, I posted this on the "No EQ Challenge" thread earlier today, and can't see it in my All Content list. As it's an old thread I'm wondering if the new site has picked it up yet. Or maybe I just haven't configured the site settings properly!

Ian

Edit. Please note that these objects were re-imaged in Dec 2016/Jan2017 and can be seen on pp 91 & 95 of the 'No EQ Challenge' thread, or else as a 'Winter Favourite' on the Deep Sky Imaging forum.

Rosette ST fits1 v2.jpg

M42 STprocess v1a.jpg

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Thanks everyone for your comments.

22 minutes ago, wxsatuser said:

Nice one.

The Fuji seems to see quite a bit in the red dept.

Yes I wondered about that, but have no way of knowing what the response actually is.

15 minutes ago, wimvb said:

...M42 isn't at all that easy, in my opinion. The more you try to get out of it, the harder it gets. You managed very well.

Well, it was an assumption founded in my inexperience :icon_biggrin:. I think the result owes more to beginner's luck than anything else.

Ian

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46 minutes ago, The Admiral said:

Thanks everyone for your comments.

Yes I wondered about that, but have no way of knowing what the response actually is.

Well, it was an assumption founded in my inexperience :icon_biggrin:. I think the result owes more to beginner's luck than anything else.

Ian

For 15secs it looks quite good, would be interesting to see something longer.

Been meaning to try my X M1 as it has the same sensor.

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1 hour ago, wxsatuser said:

For 15secs it looks quite good, would be interesting to see something longer.

Been meaning to try my X M1 as it has the same sensor.

Yes, but I  took over a hundred of 'em! I think Deep Sky Stacker ended up stacking something like 78 frames in the end. Using longer sub lengths is problematic with an Alt-Az mount due to field rotation, apart from the general imprecision of such mounts. In any event, even with 15 seconds it looks as though the core has overexposed.

The X-Trans sensor presents a bit of a problem in that it isn't a Bayer array. Although DSS uses DCRaw to decode the RAWs, and the latest version of DCRaw claims to decode the Fuji X-T1 RAFs, I couldn't get DSS to work properly with them. In the end I used Adobe DNG converter to convert the RAFs to DNGs and load those into DSS instead. If you do that, make sure that you set the compatibility to 'Camera Raw 6.6 or later'.

The other feature of the X-Trans sensor is that there is a lower proportion of red and blue pixels, and I was getting an odd colour bias out of DSS. In the end I configured the RAW settings to: Brightness=4, Red scale=0.8, and Blue scale=1.11. A neutral grey image appears grey on the screen with those, and it seems to work. I don't understand how to arrive at those settings from a theoretical standpoint though.

Ian

Edit. Actually, having just looked at a single frame in my RAW converter, the core itself doesn't look overexposed, though I wouldn't want to increase it by much. The Trapezium stars are actually visible in a single frame, so I really need to hone my Star Tools skills to bring them out!

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Very nice photos for first attempt. Before I started guiding, I was typically working from 30-45 second subs (and like you, lots of them!) and then working the processing software hard. 

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6 hours ago, The Admiral said:

Yes, but I  took over a hundred of 'em! I think Deep Sky Stacker ended up stacking something like 78 frames in the end. Using longer sub lengths is problematic with an Alt-Az mount due to field rotation, apart from the general imprecision of such mounts. In any event, even with 15 seconds it looks as though the core has overexposed.

The X-Trans sensor presents a bit of a problem in that it isn't a Bayer array. Although DSS uses DCRaw to decode the RAWs, and the latest version of DCRaw claims to decode the Fuji X-T1 RAFs, I couldn't get DSS to work properly with them. In the end I used Adobe DNG converter to convert the RAFs to DNGs and load those into DSS instead. If you do that, make sure that you set the compatibility to 'Camera Raw 6.6 or later'.

The other feature of the X-Trans sensor is that there is a lower proportion of red and blue pixels, and I was getting an odd colour bias out of DSS. In the end I configured the RAW settings to: Brightness=4, Red scale=0.8, and Blue scale=1.11. A neutral grey image appears grey on the screen with those, and it seems to work. I don't understand how to arrive at those settings from a theoretical standpoint though.

Ian

Edit. Actually, having just looked at a single frame in my RAW converter, the core itself doesn't look overexposed, though I wouldn't want to increase it by much. The Trapezium stars are actually visible in a single frame, so I really need to hone my Star Tools skills to bring them out!

You might have stacked 78 but the red still has to be there.
No doubt your stacking is averaging so does'nt make the red any brighter.
I know M42 is bright but 15secs on a f/7 scope is quite impressive.

As to DSS or any other software decoder, who knows if dcraw has been implemented
correctly for RAFs, most likely not seeing so many problems with it.

 

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  • 4 weeks later...
On 25/01/2016 at 18:03, wxsatuser said:

Nice one.

The Fuji seems to see quite a bit in the red dept.

I've come across this web site (http://kolarivision.com/articles/internal-cut-filter-transmission/) where the spectral transmissions of the IR-cut filters of various sensors is plotted. For the Fuji XPro-1, which has the same sensor as in the X-T1, and presumably has the same IR-cut filter, the transmission at 656nm is about 45%. Most Canons are of the order of 30%. So yes, it does look as thought the red response is good, assuming that the sensor responses to that wavelength are the same.

The UV transmission is a little poorer though.

Ian

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That's very kind of you to say so Alexxx, but I can't help feeling that beginner's luck has a large part to play here. I'm still feeling my way with exposure times etc, and have just embarked on seeing if I can make Pixinsight work. It's one thing to follow on-line tutorials, but when the beast decides to throw wobblies it's difficult to know how to get around them. The one good thing about Pixinsight is that it takes the Fuji RAFs without complaining. I've got 44 days left to see if I can tame it, or it tame me!

I'm also on a bit of a mission to make astrophotography accessible with a limited investment, both financially and with time.

Ian

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