M101 - The Pinwheel Galaxy: Things don't always work out!
Date: May 24, 2021
Cosgrove’s Cosmos Catalog ➤#0070
M101 - The Pinwheel Galaxy - the result of some heavy processing due to some compromised data. (click image for full resolution via Astrobin.com)
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About the Target
A little about M101- from Wikipedia:
“The Pinwheel Galaxy (also known as Messier 101, M101 or NGC 5457) is a face-on spiral galaxy 21 million light-years (6.4 megaparsecs) away from Earth in the constellation Ursa Major. It was discovered by Pierre Méchain in 1781 and was communicated that year to Charles Messier, who verified its position for inclusion in the Messier Catalogue as one of its final entries.
On February 28, 2006, NASA and the European Space Agency released a very detailed image of the Pinwheel Galaxy, which was the largest and most-detailed image of a galaxy by Hubble Space Telescope at the time. The image was composed of 51 individual exposures, plus some extra ground-based photos.
On August 24, 2011, a Type Ia supernova, SN 2011fe, was discovered in M101.”About the Project
The Annotated Image
Annotated image of M101 - The Pinwheel Galaxy - created with Pixinsight’s ImageSolver and AnnotateImage scripts.
The Location in the Sky
IAU/Sky & Telescope Constellation Chart for Ursa Major with M101 indicated by the yellow arrow.
About the Project
I first shot the Pinwheel Galaxy last year using my One-Shot-Color Camera. I wanted to try it again and see what I could get using a mono camera and L, R, G, B & Ha filters with a longer set of exposures.
So I recently imaged this target over the span of 5 nights, starting on May 13. I collected the normal LRGB filter data and I also collected some narrowband images through my Hydrogen-Alpha Filter. The equipment is pretty automated now so I could get things running and then try to sleep on the sofa - still keeping a general eye on things during the night.
At the same time, I was capturing this image, I was also capturing the data for the M63 image I shared in the past few days. So I have not had a chance to go through the data set for this image until yesterday. I really had high hopes for this image - but you don't always get what you hope for! I considered not even posting this image - but this is a journey and like any other trip - you have good days and you have bad days. I decided to show the bad with the good.
As part of the normal processing of Astro image, you take the time to look over all of the image data with software that acts like a blink comparator. Each image should look pretty much the same as others in a sequence unless a plane goes through the frame or a wondering cloud comes through, or something else goes wrong. The first thing I found was that I had many thin wandering clouds messing up a substantial number of frames that I had collected. These had to be culled. I lost over 5 hours of data and most of my Ha filter data due to this! Ouch.
Then I processed the data - doing calibrations and alignments and stacking operations. This takes hours and hours for my 12 core/24 thread Ryzen CPU to work through - at the end you can't wait to look at the resulting image masters! Then you can see what you actually got. And when I looked I found something called "Pattern Noise". You never want to see this - but - oh yes - I had it in this image. It looks like diagonal smears of rainbow colors….and this is VERY hard to fix after the fact. What causes this? The most common causes are flexure of the telescope mount (something loosens up?) or Failure to dither exposures. Dithering is a process where the scope changes its position slightly for every exposure. This moves the image around on the sensor a tiny bit and the stacking software lines everything back up in the end. This eliminates many sources of noise including pattern noise. It is possible that something in the setup failed during this exercise - thus causing the problem? I'm still not sure what happened here.
So now I have image artifacts and a LOT fewer data than I planned. OKAY…
Long story, short…. I used every processing trick in the book to salvage the data and the result is attached to this posting. It's….. OK - but to me, it’s a disappointing failure. At best it is a lackluster example of the Art (unlike my last image - that one came out *great*). Some have said that still came out alright, but all I see are the problems…
But here it is for your perusal.
You can see my Previous Effort for M101 HERE.
You can compare the two images side-by-side below (Click to zoom):
Messier 101 - 2020 version
Messier 101 - 2021 version
The initial version holds up pretty well - compared with the new - remember that the new one has data issues that held it back. I’ll have to try again next year to see if I can top these results.
More Information
Wikipedia: M101 Entry
Nasa: Hubble Image of M101
Jet Propulsion Labratory: Infrared Image of M101 from the Spritzer Telescope
Capture Details
Light Frames
A number of frames is after bad or questionable frames were culled (an many were regrettablyy removed):
76 x 120 seconds, bin 1x1 @ -15C, unity gain, ZWO Gen II L Filter
100 x 120 seconds, bin 1x1 @ -15C, unity gain, ZWO Gen II R Filter
96 x 120 seconds, bin 1x1 @ -15C, unity gain, ZWO Gen II G Filter
78 x 120 seconds, bin 1x1 @ -15C, unity gain, ZWO Gen II B Filter
Total of 11.6 hours
Cal Frames
100 Dark exposures
45 Flat Darks
40 L Flats
40 R Flats
40 G Flats
40 B Flats
Capture Hardware
Scope: Astrophysics 130mm Starfire F/8.35 APO refractor
Guide Scope: Televue 76mm Doublet
Camera: ZWO ASI1600mm-pro with ZWO Filter wheel with ZWO LRGB filter set,
and Astronomiks 6nm Narrowband filter set
Guide Camera: ZWO ASI290Mini
Focus Motor: Pegasus Astro Focus Cube 2
Camera Rotator: Pegasus Astro Falcon
Mount: Ioptron CEM60
Polar Alignment: IPolar camera
Software
Capture Software: PHD2 Guider, Sequence Generator Pro controller
Image Processing: Pixinsight, Photoshop - assisted by Coffee, extensive processing indecision and second-guessing, editor regret, and much swearing….. Given the problems on this image, more than the usual whining
I was very excited to get the ZWO ASI2600MM-Pro camera a while back. I ordered it when it was announced and then prepared to wait a long time to get it. When I did get it - I decided to put it onto the AP130 platform. That meant that I could move the ZWO ASI1600MM-Pro, along with its filter wheel over to my William Optics Platform. This now means that all of the platforms have been moved over to a mono camera and my ZWOASI924MC-Pro is now not in use.