M101 – The Pinwheel Galaxy – The Power of Processing

Last week, on Tuesday evening, there was a rare clear night that coincided with a moonless sky. The forecast was good with no cloud expected until 5am so I thought I would grab my chance and get the kit out for a session of astrophotography.

I got everything set up in the back garden and pointed the scope towards the handle of The Saucepan, Plough, Great Bear, Ursa Major – whatever you want to call it, and the very faint Pinwheel Galaxy or M101.


M40_M97_M108_M109_Finder_Chart

Star Chart from FreeStarCharts.com


The galaxy probably is a bit faint with my skies and equipment, but the night was favourable, so I thought, ‘why the hell not?”

Well, as it turns out, because the forecast was wrong and the clouds came in several hours ahead of schedule, cutting short what I had hoped to be 3 to 4 hours of imaging. In the end I only got 16 subs of 420 seconds each to a total of just under two hours. Overall, not long enough to get all the detail out of the galaxy, but enough to have a go at getting a final image.

I also didn’t take any DARK subs as I was running out of time and getting a little cold, so it was calibrated with just LIGHTS, FLATS and BIAS sub frames. I was hopeful that, as I was dithering the plan, the need for darks would be diminished. The use of DARK frames seem fairly well debated anyway, so I wasn’t too worried.

Anyway, the next day, I stuck the images through Deep Sky Stacker as usual and put the resulting frame into PhotoShop for processing. I am still not sure I fully know what I am doing in Photoshop and still struggle to get the colour right in my images, so was happy that I got the galaxy, but not too happy with the resulting image which was rather purple. I was struggling in Photoshop to get colour out of the image without introducing too much noise.


M101 - 8th February 2016 - PS

M101 – 8th February 2016 – 16 x 420s LIGHTS. Stacked in DSS with 30xFLATS and 30xBIAS frames. Processed in Photoshop

Despite that, the image is not too bad for something that is 20 million-odd light years away and a damn site better than my first effort from last year which I think may have been deleted somewhere along the line… or at least is on some back-up drive in a dark, dusty cupboard somewhere.

The focus seems good and there is some detail in the galaxy, so not too disappointed. But not 100% happy with the colour.

So I gave it another go, bit the bullet and had a crack at it with PIXINSIGHT which I am currently trialing to see how I get on with it. It has a reputation for having a MASSIVE learning curve but, then again, astrophotography isn’t exactly a walk in the park.

Anyway, I followed some tutorials at Harry’s Astroshed and reprocessed the sames sub-frames to come up with a different final image. At this point I can heartily recommend Harry’s tutorials. There clearly is a steep learning curve with PIXINSIGHT, but they certainly seem to be a good place to start.


M101 - 8th February 2016 - Pixinsight

M101 – 8th February 2016 – 16 x 420s LIGHTS. Registered and stacked in PIXINSIGHT with 30xFLATS and 30xBIAS frames. Processed in PIXINISIGHT.

 

Both images are from the same set of LIGHT frames, but have slightly different crops, so the first looks slightly bigger than the second – but they are from exactly the same source. Unfortunately, because of the size of the DSLR sensor, the images are heavily cropped which does increase the visibility of noise in the image, PIXINSIGHT has done a good job of minimising this – as it is a lot less noisy than my first try.

To me, it is clear that the second image has much better colour balance and is, overall, a more pleasing image and probably not far off the best I could hope with a relatively small number of subs.

PIXINSIGHT is clearly a much more powerful (and dedicated) astrophotography processing tool than PhotoShop and I like what I have seen so far. That’s not to say I couldn’t achieve the same in Photoshop but PIXINSIGHT just seemed to make more sense. I feel that I learned more about Star Masks in 6 minutes of tutorial with Harry than I have learned in the last year – so I am looking forward to good things going forward!

Hope you like the photos, and if you have any thoughts on PIXINSIGHT or capturing/processing M101, please feel free to share them below!

Cheers!

 

M101 Data Table (courtesy of Free Star Charts)

Messier 101
NGC 5457
Name Pinwheel Galaxy
Object Type Spiral galaxy
Classification SAB (rs) cd
Constellation Ursa Major
Distance (kly) 22,000
Apparent Mag. 7.9
RA (J2000) 14h 03m 12s
DEC (J2000) 54d 20m 55s
Apparent Size (arcmins) 28.8 x 26.9
Radius (light years) 90,000
Number of Stars 1 Trillion
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Posted on March 12, 2016, in Astronomy, Astrophotography, Uncategorized and tagged , , , , , . Bookmark the permalink. Leave a comment.

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