Fun facts
CTB1 was discovered in 1955 by George Abell on the Palomar survey plates, thinking it was a planetary nebula based on its shape. In 1960 Robert W. Wilson (who later won the Nobel Prize with Arno Penzias for discovering the cosmic background radiation) and J. G. Bolton properly cataloged it as part of an early radio telescope survey. This list was known as CalTech observatory list B, hence the CTB designation. In 1966, Abell included it in his catalog of planetary nebulae (not to be confused with his catalog of galaxy clusters) with the note, “it may be a supernova remnant,” as it was already thought to be an SNR based on its radio signal. Further research in 1971 showed that CTB1 is, instead, a supernova remnant 10000 light-years away from us with a diameter of about 100 light years. Thus, CTB1 is probably the proper designation for this object, even though Abell was actually the discoverer.
Distance: 10,000 light years
Diameter: 100 light year
Constellation: Cassiopeia
Designations: CTB1, PN A66 85, Abell 85
{From https://digitalstars.wordpress.com/2022/10/22/ctb1-abell-85-the-garlic-nebula/ https://skyandtelescope.org/online-gallery/garlic-nebula/ and Stellarium}
Capture & Processing Notes
Capture & Processing Notes (Re-framed sequence captured on 24 October 2024): This is the second imaging session at HCH to verify the reframing of CTB1 Garlic Nebula prior to imaging in dark skies. (The capture notes from the first session on 21 October are shown below for historical sake, but the image above is the re-framed version with data captured during the 24 October 2024 session.
Changes made during the 24Oct2024 session from the 21Oct2024 imaging session:
- Turned off the auto meridian flip
- Changed the EAF step size to 150 (throughout the BB/BZ equipment profiles)
Everything worked very well and the new framing (and settings) is what I will use going forward for this DSO.
This is also an illustration of “I’ve never processed the same image the same way twice!” This is essentially the same data. The big difference in the processing was starting with the STARLESS 30% stretch stacked image (vs. 20% stretch). The rest of the processing steps were pretty much identical. Another processing experiment I’d like to run on these data are to use a Hubble pallet processing – some of the images I’ve seen have done that which renders the head of garlic a shade of yellow – thus having people recognize it as a head of garlic and not a brain/brain stem! That will likely not come for awhile – there are many more pressing things on my list of things to do, including first and foremost planning and packing for next weekend’s (hopefully) dark skies trip!
Capture & Processing Notes (Original sequence framing captured on 21 October 2024): This capture was an SGP Framing & Mosaic Tool test. I’d added this DSO to my list to capture starting in October 2024, but when I planned the sequence in SGP I couldn’t see the nebula in the star field that came up at its location. I built a sequence as best I could, guessing at where the garlic head-shaped nebula was located. But I didn’t want to spend precious dark skies time capturing the area around/near or just a portion of the DSO. So, I deferred the target from my October plan until I could validate the framing during an imaging session from the front patio. That opportunity came during a few clear nights in late October (with a lot of moonlight…but that’s what the LeXtreme filter is for!).
I assembled Big Bertha (still in her case from the October dark skies trip) and set up to image on Monday night, 21 October. This was my only objective, so I imaged throughout the full night (which are getting longer!).
During the collection, everything worked smoothly at the beginning of the sequence. It was a little before 2000 when I was up and operating, collecting data on the first subframe. I sat outside and watched a couple of subframe’s collection – hoping that I would get an indication that I had the DSO in the frame…no such luck…nothing was visible in the subframes except the star field. So, I talked myself into just letting it run throughout the night – it’s only bits, it’s from the front patio, no-harm no-foul if there’s nothing but stars in the end.
I did experience one slight technical glitch… I came out to execute the meridian flip at about 2300MDT and discovered that the telescope had already flipped on its own at some point before my SGP-directed 20 minutes past the meridian (when I came out there was ~ 6 minutes to go before that point). I let it complete the subframe that it was collecting, and as expected, I got the warning: :”The next subframe’s time is longer than the time to the flip – would you like to execute the meridian flip now?” I thought…sure, why not, let’s see what it does! What it did was lock up the laptop (with another “do you want to pause before the meridian flip” warning hidden behind the main window that was precluding me from executing any commands in SGP). I finally decided to use the ASCOM driver to send the telescope to its parking position, disconnect the equipment, reboot the laptop, recycle the power on all the equipment, and restart the sequence. When I did that (thankfully) it reacquired the DSO on the correct side of the pier and went on its merry way of collecting data flawlessly the rest of the night (including the autofocuser working well!)
I’m going to have to investigate the SGP log to see what I can figure out, or ask the question to their technical support that I pay for with my annual subscription about the auto-meridian flip function. OR, just turn it off – since I always come out and supervise anyway… (which may be my short term solution!)
When I stacked the subframes, I was pleased to see the garlic head-shaped nebula in the frame! Albeit, not centered correctly. But with a little tweaking of the framing I should be all set for imaging this DSO during our upcoming (fingers crossed Mother Nature cooperates) November dark skies trip over the Halloween weekend. This is definitely a target that I want to image in dark skies. Although there’s not a lot of information or other’s images of it – it is an intriguing object worth some dedicated dark skies time to bring out the richness of its colors and features.
Sequence Plan (24Oct2024): Gain: 158, Temp: -0°C, offset=30. 118x300sec. Total: 590 minutes (9:50hrs). Captured 24Oct2024, 1916MDT – 25Oct2024, 06:02MDT.
Sequence Plan (21Oct2024): Gain: 158, Temp: -0°C, offset=30. 105x300sec. Total: 525 minutes (8:45hrs). Captured 21Oct2024, 1947MDT – 22Oct2024, 05:50MDT.
Processing: Captured in SGP, stacked in APP (HaOIII Color), star removal with Starnet++, processing with LR/PS
Equipment
Equipment: All equipment controlled by HP Probook running Sequence Generator Pro v4.4.1.1441.
- Imaging (ASI2400-BB-FF): ZWO ASI2400MC imaging camera on (Big Bertha) Orion 8″ f/8 Ritchey-Chretien Astrograph Telescope, Teleskop Service (TS) 2.5” Rack and Pinon Focuser M90, Teleskop Service Flattener 1.0x for RC Telescopes (TS-RCFLAT2), Optolong L-Extreme LP filter
- Autofocuser: ZWO EAF Electronic Automatic Focuser (EAF-5V-STD)
- Mount: Rainbow Astro RST-300 (controlled by iHubo ASCOM driver)
- Polar alignment: QHYCCD camera (controlled by Polemaster for polar alignment)
- Autoguiding: Orion 60mm Multi-Use Guide Scope with Orion StarShoot AutoGuider Pro Mono Astrophotography Camera (controlled by PHD2)
Summary
Captured: 24 October 2024. Total: 118x300seconds; 590 minutes (9:50hrs)
Shooting location: HCH, Colorado Springs, CO
Equipment: Big Bertha on Rainbow Astro RST-300
Processing summary: Captured in SGP, stacked in APP (HaOIII Color), star removal with Starnet++, processing with LR/PS