Messier 20 - The Trifid Nebula - Mono Camera FIrst Light!
Date: July 17, 2020
Cosgrove’s Cosmos Catalog ➤#0042
Messier 20 - The Trifid Nebula that was created in LRGB. (click to enlarge)
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About the Target
Messier 20 is known by the common name “The Trifid Nebula” and by NGC 6514. It is a star-forming region in the constellation of Sagittarius and is located about 4100 light-years away. Here is what Wikipedia has to say:
It was discovered by Charles Messier on June 5, 1764. Its name means 'three-lobe'. The object is an unusual combination of an open cluster of stars, an emission nebula (a relatively dense, red-yellow portion), a reflection nebula (the mainly NNE blue portion), and a dark nebula (the apparent 'gaps' in the former that cause the trifurcated appearance also designated Barnard 85). Viewed through a small telescope, the Trifid Nebula is a bright and peculiar object and is thus a perennial favorite of amateur astronomers.
The Annotated Image
The annotated version of this image was created using Pixinsight’s Imagesolver and AnnotateImage scripts.
About the Project
M20 - The Triffid Nebula. I actually shared a shot of this object earlier this year, taken with my OSC (One-Shot-Color) camera and my main scope.
This is a first for me! After more than a year since I got the Astro-Physics telescope, it is finally ready to make images! It will also be my first time using a cooled mono camera and LRGB filters mounted on a wheel.
This scope has a longer focal length, so the scale of the image is larger than in my previous shot.
This one was taken on the 7-17-20, the same night as my Elephant's Trunk Nebula.
It is the result of 10 x120 second luminance images, and 8x120 second images for RGB filters. I had some difficulty processing this image but I have now sorted that out and this is my resulting output.
A mono camera is a lot more work. For example, files for this project top out at 12GB once you count all of the Dark, flats, and bias calibration files. But with a relatively small number of subs, you can get a great signal-to-noise ratio. One-shot-color cameras typically use an RGGB Bayer filter pattern. So every 2x2 block of pixels has 1 red, 1 blue, and 2 green pixels. On a mono camera, all 4 pixels are used for one color. So when you think about it, a one-shot-color camera has 25% of its pixels measuring R and B each, and 50% of its pixels measuring G. BUT - with the possible exception of a few planetary nebulae, there are almost NO green-colored objects on the night sky. So half your signal is kind of wasted. A mono camera is much more efficient. On the other hand - it's also kind of a pain in the butt and a lot more work. You really can't beat the convenience of an OSC! But with relatively few frames, this is a pretty respectable image if I do say so myself!
Location in the Sky
FreeStarChart.com Constellation Chart for Sagittarius, showing M20’s location indicated by a yellow arrow.
Capture Details
Light Frames
10 x 120 seconds L
8 x 120 seconds R
8 x 120 seconds G
8 x 120 seconds B
Total of 1.33 hours
7-28-21 note: I was so new at this at the time, I never recorded little details like camera binning or cooldown temps!
Cal Frames
not recorded
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 ZWO GeII 7nm Narrowband filter set
Guide Camera: ZWO ASI290Mini
Focus Motor: Pegasus Astro Focus Cube 2
Mount: Ioptron CEM60
Polar Alignment: Polemaster 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…..
Over the winter, I began to get things ready for the second platform. Clearly I had some work to do. I needed to determine what I was going to do for a camera, and I needed to determine what to do get the mount functioning at the precision needed.