IC1848 Soul Nebula

IC1848 Soul Nebula; 4-tile mosaic captured at HCH, Colorado Springs, CO with ASI2400MC on Big Bertha

Fun facts

Westerhout 5 (Sharpless 2-199, LBN 667, Soul Nebula) is an emission nebula located in Cassiopeia. Several small open clusters are embedded in the nebula: CR 34, 632, and 634 (in the head) and IC 1848 (in the body). The object is more commonly called by the cluster designation IC 1848.

W5, a radio source within the nebula, spans an area of sky equivalent to four full moons and is about 6,500 light-years away in the constellation Cassiopeia. Like other massive star-forming regions, such as Orion and Carina, W5 contains large cavities that were carved out by radiation and winds from the region’s most massive stars. According to the theory of triggered star formation, the carving out of these cavities pushes gas together, causing it to ignite into successive generations of new stars.

This complex is the eastern neighbor of IC1805 (Heart Nebula) and the two are often mentioned together as the “Heart and Soul”.

Other Catalog Designations: Westerhout 4,Sh2-199, LBN 667 – Cluster is IC 1848
Subtype: HII region, Cluster associated with nebulosity
Magnitude: 6.5
Distance from Earth: 7500 light years
Apparent Size: 2°30’ x 75’
Constellation: Cassiopeia

{ Target information derived from: https://en.wikipedia.org/wiki/Westerhout_5 and Stellarium }

Capture Notes

With this target, I finally figured out the proper back focus for the TS-RCFLAT2 field flattener!  In almost two weeks of back and forth email with Marc Fischer from Teleskop Service, he kept telling me I needed 109mm of back focus for the FF to properly correct the coma.  Further, he kept telling me the M54M-M48F 21L connector was 21mm of that distance.  I was completely bewildered, because for over a week I was measuring the M54M-M48F 21L connector as 220mm (180mm if I deleted the length of the female threads).  I couldn’t for the life of me figure out how I was going to get the proper back focus when the connector that came with the camera was already double what I needed.  Saturday morning, after a good night’s sleep on Friday night, I found and read a great article by Agena Astro on back focus that talked about both the back focus of the telescope (the debacle with the extension tubes I’d just been through) and the back focus for optical accessories, like a field flattener.  (That article is: A Primer on Back Focus in Astronomy at: https://agenaastro.com/articles/miscellaneous/a-primer-on-back-focus-in-astronomy).  The light began to dawn!  For over a week, I was doing the conversation from cm to mm wrong!  Thinking the 109mm was 1.09cm or about half an inch, instead of the proper 10.9cm or about 3.5 inches!  All I can say is that I’m simultaneously embarrassed (how many math classes have I taken throughout the course of my high school and college years?) and relieved.  With this “new math” I had to add length to the equation, rather than subtracting!  AND I had the 2” tubes in house (because Paul had mistakenly ordered me a 2” long, 2” diameter tube when we were searching for the BB extension tubes – I needed that, the M54M-M48F 21L and the M48F 16.5L connector that also came with the camera (the distance inside the camera to the sensor is 17.5mm) – so all that put together was 89.7mm.  Darn near close enough to the needed 91.5mm to give it a try.  What I saw in the first subframe (even in the focusing frames) was a beautifully coma-free star field from corner to corner of the image!

But there’s always something!  One problem solved and one persists.  Again, I continued to have issues around the meridian.  Spoiler alert: I did end up solving that issue, but not during this imaging session…


Polar alignment: QHYCCD camera (controlled by Polemaster)
Imaging: (Big Bertha) Orion 8″ f/8 Ritchey-Chretien Astrograph Telescope, ZWO ASI2400MC imaging camera, Teleskop Services TS-Optics 2″ 1.0x Flattener and Field Corrector for Ritchey-Chrétien Telescopes (TS-RCFLAT2), 89.7mm of connector tubes between camera and TS-RCFLAT2 for proper back-focus (M54M-M48F 21L, 2” M48F, M48F 16.5L), Optolong LeXtreme light pollution filter
Mount: SkyWatcher EQ6‑R PRO Synscan mount (controlled by ASCOM driver)
Autoguider: Orion 60mm Multi-Use Guide Scope, Orion StarShoot AutoGuider Pro Mono Astrophotography Camera (controlled by PHD2)
All equipment controlled by HP Probook running Sequence Generator Pro v3.2.0.660.

Capture & processing notes

Sequence plan: Gain: 158, Temp: -0°C, offset=30, 4-tile mosaic. 

Tile1: 30x5min; Captured 7Oct2023, 2000MDT – 2234MDT; Exposure time: 2:30hrs
Tile2: 29x5min; Captured 7Oct, 2238MDT – 8Oct, 0108MDT; Exposure time: 2:25hrs
Tile3: 30x5min; Captured 8Oct2023, 0117MDT – 0327MDT; Exposure time: 2:30hrs (with imaging gap 8Oct2023, 0230MDT – 0332MDT due to mount issues around meridian)
Tile4: 18x5min; Captured 8Oct2023, 0442MDT – 0615MDT; Exposure time: 1:30hrs

Capture: Captured 7Oct2023, 2000MDT – 8Oct2023, 0615MDT.  Total exposure time (4-tiles): 8:55hrs.
Shooting location: HCH, Colorado Springs, Colorado
Processing: This image is 8:55 hours of data captured with SGP, in four tiles.  Individual tiles stacked in APP (HaOIII Color), then stitched together as a mosaic.  Star removal with Starnet++. Processed in LR/PS.