Hemisphere:  Northern  ·  Constellation: Auriga (Aur)
Getting plate-solving status, please wait...
Sh2 224 (Chef in Hat Nebula), 


            Ryan Haveson

Sh2 224 (Chef in Hat Nebula)

Getting plate-solving status, please wait...
Sh2 224 (Chef in Hat Nebula), 


            Ryan Haveson

Sh2 224 (Chef in Hat Nebula)

Technical card

Imaging telescopes or lenses: William Optics FLT 132

Imaging cameras: ZWO ASI294MM-Pro

Mounts: iOptron CEM 70

Guiding telescopes or lenses: William Optics 50mm Guidescope

Guiding cameras: ZWO ASI174mm Mini

Focal reducers: William Optics Reducer Flattener 68III

Software: PixInsight  ·  NINA

Filters: Astrodon 36mm Filter Set (3nm Sii/Oiii, 5nm Ha)  ·  Baader Planetarium LRGB 36mm

Dates:Jan. 6, 2021

Frames: 500x300"

Integration: 41.7 hours

Avg. Moon age: 22.24 days

Avg. Moon phase: 48.98%

Basic astrometry details

Astrometry.net job: 4189520

RA center: 5h 26' 48"

DEC center: +42° 56' 20"

Pixel scale: 1.431 arcsec/pixel

Orientation: 125.129 degrees

Field radius: 0.960 degrees

Resolution: 4011x2692

Data source: Backyard


This is Sh2 224. It does not have a common name, but I think it looks like a chef in a hat, so I call it Chef in Hat nebula. This was a very challenging target because there was so little signal. The 5 minute subs in Oii looked like no signal at all, and the signal in Ha from the target was about the same as the signal that I subtracted from my flats.

----- Notes about the Target -----
Here are some notes that I found from Waid Observatory (link):

Sh2-224 is a very faint supernova remnant located approximately 14,700 lightyears distant in the constellation Auriga. This unusual celestial object is also designated VRO 42.05.01

The nebula created by the supernova explosion is composed of two visual parts. It is postulated the supernova explosion created a bubble like structure. As the shockwave from the explosion progressed into a very low density region of the interstellar medium, a "wing" component was expelled.

Supernova explosions are the end stage of the natural life cycle of very large stars. Such events are responsible for the distribution of heavy elements into the interstellar medium where they are incorporated in the birth of new star systems. Without this phenomenon, planets, such as the Earth along with life as we know it, would not be possible.

-----Imaging Details-----
This was shot from my Bortle 8/9 backyard in Pasadena, CA. This was captured over the course of 2 weeks (there were other targets interspersed so I only had a few hours a night on it).

----- Integration Details -----
Ha (13.75h) - 119x300s at 200 gain + 46x300s at 300 gain*
Oiii (20h) - 247x300s at 300 gain
RGB (4h) (for star field) - 78 each of RGB @60s + 120 gain

*note about gain: I was experimenting with different gain settings and since this was a several day target I decided to keep them all. I integrated the subs by gain and then combined those integrated masters to the final master, weighting them by # exposures.

----- Things I learned -----
I started looking into doing a better job with background extraction (DBE/ABE) and tried some techniques with selecting background samples, etc. It seemed like my RGB backgrounds were easier to extract than the long exposure Ha and Oiii. So I used the ABE extracted R background from my RGB set and used it to extract the background on my Ha (and B for Oiii) and it worked pretty well. I just used PixelMath and did something like Ha - (0.48 * R_BACKGROUND). Since the background was not normalised to the Ha, I noodled around with the factor and ended up with 0.48, but that was just poking around at different values and seeing what it looked like.

I also tried a few different integration / weighting strategies and found that it was actually a very tiny bit better to include some poor FWHM measured images for the NB integrations than to exclude them. I guess b/c there is some signal there and since I am doing starnet on it anyway, the star bloatedness is less relevant.



  • Sh2 224 (Chef in Hat Nebula), 


            Ryan Haveson
  • Final
    Sh2 224 (Chef in Hat Nebula), 


            Ryan Haveson

Sky plot

Sky plot


Sh2 224 (Chef in Hat Nebula), 


            Ryan Haveson