Hemisphere:  Northern  ·  Constellation: Gemini (Gem)  ·  Contains:  NGC 2395
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Sh2-274 - Abell 21 - Medusa Nebula, 


            Volker Gutsmann
Sh2-274 - Abell 21 - Medusa Nebula
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Sh2-274 - Abell 21 - Medusa Nebula

Technical card

Imaging telescopes or lenses: 8 Inch f4 Carbon Newton

Imaging cameras: ZWO ASI 2600 MM Pro

Mounts: Skywatcher EQ 6 Syn Scan

Software: Pleiades PixInsight  ·  N.I.N.A.  ·  Lightroom 5

Filters: Baader Filtersatz LRGBC + Schmalband H-alpha/O-III/S-II, 36 mm

Accessory: Lacerta GPU Comacorrector

Dates:March 2, 2021

Baader H Alpha H Alpha 7nm: 28x300" (gain: 100.00) bin 1x1
Baader OIII 8.5nm OIII 8.5nm: 37x300" (gain: 100.00) bin 1x1
Baader RGB 36mm: 60x60" (gain: 100.00)

Integration: 6.4 hours

Avg. Moon age: 18.25 days

Avg. Moon phase: 86.89%

Bortle Dark-Sky Scale: 6.00

Basic astrometry details

Astrometry.net job: 4275739

RA center: 7h 28' 51"

DEC center: +13° 16' 48"

Pixel scale: 1.351 arcsec/pixel

Orientation: 125.880 degrees

Field radius: 0.685 degrees

Resolution: 3000x2079

Locations: Backyard, Langenfeld, NRW, Germany

Data source: Traveller


This is a bicolor of the Medusa Nebula aka Sh2-274, plus star color by RGB. This is also my first image with my new ASI 2600MMPro. I think that I will be quite happy with this new camera. The 16bit ADC, increased full well capacity and efficiency seem to make it a better camera than the 1600 which was already a really good camera. I am eager to explore more ...

Workflow has changed recently as I have found the star less approach to cause some artefacts that I did not like. Now I work on the original narrowband images and use Starnet only to obtain a good star mask. Star color is blended in a later stage - still experimenting here.

I hope for a few more clear nights soon ...



Sky plot

Sky plot


Sh2-274 - Abell 21 - Medusa Nebula, 


            Volker Gutsmann

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