The Heart finally has its Soul Nebula

I have been imaged the IC1848 Soul Nebula a few times in the past, but ended up with nothing worth sharing. Finally - after solving the back-focus issue I'd been having with my field flattener, I was able to capture a beautifully coma-free set of mosaic tiles to produce an image of the Soul Nebula, to join its soul-mate the Heart Nebula in the gallery!

IC1848 Soul Nebula

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

IC1848 Soul Nebula

Target 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, Soul Nebula.

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”.

Capture Notes:

I finally figured out the proper back focus for the TS-RCFLAT2 field flattener (needed to correct the curvature that causes coma (or the elongation of stars around the corners of the image, making them look like commas)!  In almost two weeks of back and forth email with Marc Fischer from Teleskop Service (the manufacturer of the field flattener), 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 (that came with the ASI2400MC to connect it to the rest of the imaging train (filter, field flattener, etc) 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:  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 had issues with losing imaging time around the meridian.  I won’t go into all the gory details – but that issue wasn’t solved for this image, but I have figured  it out, so stand by for the rest of that story…  

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, CO

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. 

The gallery entry, for the “rest of the story” is here: