Revisiting the Draco Triplet: NGC 5981, NGC 5982, & NGC 5985
Date: June 23, 2021
The Draco Triplet, consisting of NGC 5981, NGC 5982, and NGC 5985. (click image for high resolution via Astrobin.com)
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The Draco Trio consists of a close grouping of three very different looking galaxies, found in the constellation Draco.
The Spiral galaxy towards the lower right is NGC 5985. Located 140 Million light-years away, this galaxy measures 246,000 light-years across. For comparison, our Milky Way is 185,000 Light years in diameter.
Next up the chain is the fuzzy elliptical galaxy NGC 5982. This galaxy is 130 Million Light Years away and was discovered by Sir William Hershel in 1788. The luminosity of this galaxy comes from very old stars, and the core of the galaxy contains a supermassive black hole.
Finally, we have NGC 5981, which is a spiral galaxy seen edge-on. Located 112 Million Light years away, it is slightly closer than the other two galaxies. If you zoom in on the image you can see a prominent line of dust towards one side.
These galaxies are part of a larger group of galaxies known as the NGC 5982 Cluster.
Annotated image of the framing - done with Pixinsight ImageSolve and AnnotateImage Scripts.
IAU/Sky & Telescope Constellation Map for Draco - Messier 16 indicated with the yellow arrow.
My first Attempt at the Draco Triad in 2019.
Frankly, these are galaxies are pretty small and the grouping does not have a great visual impact when seen at this scale. So why bother shooting them?
Well - there are a couple of reasons.
First, these galaxies are pretty far away compared to some - and just to capture some photons that left when Earth was in the Cretaceous Period - when triceratops walked the Earth and Pterosaurs flew in its skies - yeah - that's kind of cool.
Another reason is that when these were taken, due to the time of year and what can be seen through my tree tunnels - there weren't a lot of other targets available - so why not? In fact, I shot this same target almost one year ago - almost to the day. So this is a kind of test to see if I am improving in my technique.
Finally - these are small galaxies and pulling out detail with my scope will be a challenge. How much detail can I resolve? How much can more can advanced image processing reveal? I spent a lot of time doing deconvolution processing to restore detail lost through the optical system - and I was able to pull out more detail than I thought possible.
Anyhow - here is my most recent attempt at this.
Compared with the first image made in 2019, this latest image is a significant improvement. So why are we seeing this difference? The same scope was used, but this time the camera is a ZWO ASI160MM-Pro mono camera. This camera does have a higher resolution, and the integration was longer as well, by a factor of about two. Finally, I have a lot more experience with the processing side of things and I worked very hard to pull out every bit of detail that was there. You can see much more detail in the spiral galaxy and in the dust lane in the edge-on galaxy. FInal the color is vastly improved.
Wikipedia Entry: NGC 5982
Web Society: Draco Triplet
Light Frames
These were taken over the nights of June 16 & 17
58 x 120 seconds, bin 1x1 @ -15C, unity gain, ZWO Gen II L Filter
38 x 120 seconds, bin 1x1 @ -15C, unity gain, ZWO Gen II R Filter
38 x 120 seconds, bin 1x1 @ -15C, unity gain, ZWO Gen II G Filter
38 x 120 seconds, bin 1x1 @ -15C, unity gain, ZWO Gen II B Filter
Total of 5.7 hours
Cal Frames
40 Dark exposures
25 Flat Darks
Flat frames taken each night of shooting, and used to calibrate that night’s Light frames
30 L Flats
30 R Flats
30 G Flats
40 B Flats
Scope: William Optics 132mm f/7.0 FLT APO
Guide Scope: Sharpstar 61EDPHII
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: Polemaster camera
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.