CTB1 - Finally …
CTB1 - Phase 3.6 - G116.9+0.2 - Nickname validated by NASA : Medulla Nebula because it looks like a brain.
Phase2
Phase1
A challenge, again, another one that stimulated me to be better at what I’m doing.
I’ll try to give an insight about what triggered me on this particular object.
Mr Abell, in the early 60s, found out a planetary nebula and he put it into his catalog with the number 85. Few years later, some other scientists contradicted this discovery … that’s not a planetary nebula, that’s a Supernova remnant. Abell agreed on that and so Abell 85 became CTB1, the first object to a new catalog named based on Caltech Observatory : CTB. Another catalog … a bit annoying … there are so many, way too many to my point of view … We have Messier, Abell, SH2, LBN, LDN, NGC/IC, Barnard, Melotte, Caldwell, WR, etc … and let’s not forget the nicknames ! i.e. Heart and Soul Nebulas, Veil Nebula … and I was trying to figure if these catalogs were cross-checked … I’m using some software to understand where the Deep Space Objects are located. And I discovered that Abell 85 was pointing nowhere it should be. Maybe the embedded catalog into this software was not up-to-date with the right coordinates … I don’t know.
I’m using N.I.N.A. software to drive my telescopes, and guess what ? There is no CTB1 object in there … I went on the Simbad portal (University of Strasbourg), and found out the coordinates of CTB1. I’ve put these into N.I.N.A. , and tried to slew my telescope to CTB1 … that was a failure … not centered at all.
There is another thing about this supernova remnant … it is extremely faint … I caught the Flying Dragon, it was very faint … this CTB1 object is fainter … so good luck to figure if you are centered on this object. Even a shot exposed at 5 minutes will not give you any hint … Sounds like a challenge to me !!! I want to catch it so bad …
Let’s face it, I’m still a rookie … my maximum exposure on pictures was 60 seconds when I saw for the first time CTB1 on astrobin , and I knew I needed more (I always need more from myself …). But for that, I needed to step up on my skills … so it took me quite two years to feel I would be ready for it.
Let’s not talk about the weather and the clear skies … it’s depressing … I waited for clear skies patiently.
Oh, by the way, here’s a cool fact : CTB1 is very faint, incredibly faint … but if it would be visible at naked eye … it would be as big as the Moon in the sky !!! So I needed a wide field telescope. I’m back on my Celestron with the Hyperstar, 520mm focal. I was looking at the astrophotographers who caught CTB1, and they were between 20 and 40 hours of shooting to get it properly … that’s how faint this object is …
Some weeks ago, I figured that N.I.N.A. has CTB1 into its catalog, but under the name SNR G116.9+02 … yeah … another catalog but to be fair I understand SNR (SuperNova Remnant) better than CTB1. (A glimpse here about this SNR catalog : https://www.mrao.cam.ac.uk/surveys/snrs/snrs.names.html )
I’m back at top of the hill, dark sky and no perturbation … Let’s shoot with the filter catching Ha (Red) and OIII (Blue-Green). On my first night (29th of July), I shot 18 valid pictures of 300seconds each. That was phase 1. I got a lot of issues with my guide system, and I lost about 15-20% of my shots. I felt good to get a bit of OIII gases … it was promising with additional shots I guessed.
The second night ( 5th of August), same thing, some guiding issues but I got quite a lot of new data : 43 pictures. That was phase 2.
I was pretty sure it could have been the final shots for this object, but I felt the need to use my other filter (Sulfure and Oxygen, S2O3)
The third night (10th of August), I’ve shot 12 pictures with my S203 filter … no guiding errors !! But I wasn’t really happy about it … I was then thinking of shooting again with the HaO3 filter.
The fourth night (it sounds a bit like a Star Wars Jedi …), the 12th of August, back to my guiding errors (I need to work on it, I’ve pushed the guiding polling to 1.5 seconds instead of 1 but it didn’t change that much the number of errors), but I’ve shot a lot : 34 valid pictures. It was the peak for Perseides and I caught some of them.
About the stacking process of these shots, I decided to discard the S2O3 as I didn’t like them. Maybe I’ll have a look at them later. So the final result (phase 3.6) is about 95 shots, 300 seconds each, and then it is about quite 8 hours of exposure in total on the final picture.
Pixinsight is a powerful tool for treating all these data, but the downside of using a Hyperstar telescope is to get wayyyyyyyyy too many stars : 22000+ stars caught. And these stars were hiding the beauty of this object. I found a setup on a star mask that deleted about 20% of them so we can see better CTB1.
Maybe you’ve noticed I’ve shot only 8 hours versus the 20-40 hours from my fellow astrophotographers … it is a small math problem I explained on a previous post. The speed of catching light (photons) is based on a ratio between the focal length and your telescope mirror diameter (F/D). The smaller this ratio is, the faster your telescope is. My setup with the Hyperstar has a F/D at 2.2 while most telescopes have a F/D between 5 and 7. Let’s do the math : if you shoot 40 hours with a telescope at F/D 5, you only need to shoot 40:((5/2.2)squared) so 7 hours and 44minutes with a Hyperstar at F/D 2.2… yep, that’s how fast Hyperstar is. Though, Hyperstar is not a panacea. It has downsides such as :
It is very difficult to make calibration frames (flats, biases and darks) because the camera is placed in front of the telescope, where the light is coming in … (difficult to put a cap on it)
You can’t use filter wheel because it is too large and it would hide a big piece of the entry for the light. There are some camera with filter wheel integrated but I’m not even sure it would work fine.
So you have to change manually your filter and it is a delicate process because you don’t want to jeopardize your telescope alignment.
… and other stuff but still it is a great piece for astrophotography.
Some lessons/reminders from these four sessions :
I got issues on my celestial north alignement … on my third night, I figured that my tripod legs were not locked firmly so my setup was vibrating … seriously I’m ashamed I forgot about this step …
When I got these alignement issues, I tried the 3 stars alignment from N.I.N.A. … it wasn’t my best experience. Using my Polemaster is way better (when the tripod is locked and stable …)
I also figured that my guiding scope was trembling … the screws fixing it became loose …
I’m now comfortable shooting at 300 seconds exposure … my next move will be 600 seconds per shot for a special target … fainter than CTB1 !!
Exifs : Celestron C9 + Hyperstar / PegasusAstro Nyx-101 / PlayerOne Poseidon C Pro cooled at -10°C / Askar D1 HaOIII filter / Guiding System Askar 135mm scope with PlayerOne Ceres C
95 lights 300 seconds each (almost 8 hours exposure for final picture)
20 biases - 20 darks - 50 flats
Stacked with Pixinsight (WBPP)- Post-Treatment with Pixinsight with a minimum of processes (5!).
