Observation by Mike Greenhill-Hooper: Rosette nebula in SHO

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Mike Greenhill-Hooper


Mike Greenhill-Hooper


2022 Feb 08 - 21:00


2022 Feb 12 - 13:37



  • 770 f/7 ED TS Photoline refractor, 0.8 field flatenner on NEQ6 mount
  • Image camera: ASI294MM Pro; guide camera ASI224MC on 328mm piggy-backed refractor
  • Imaging, goto and dithering managed via APT / EQMOD; guiding via PHD2

15x180s exposures for each of three filters: ZWO H-alpha, SII, Astronomik OIII. Camera gain 121, offset 10


Miradoux, S.W. France

Target name



Rosette nebula in SHO

About this image

First attempt at 3-colour narrowband imaging with the mono CMOS camera. Moon was ~50% illuminated and caused significant light gradients, nearly swamping the OII and SII images.  In addition 45 minutes imaging for each filter is not sufficient. Applied Hubble palette convention - assigning H-alpha, OIII and SII images to green, blue and red, respectively.  Calibrated images with darks (at -15C, same as imaging temperature), and flat and dark flats taken for each filter (indoors in dark room with light panel and T-shirts added to further reduce intensity to ensure ADU was at mid-point of 32k).  All calibrations, stacking, colour image combining and post processing performed using Affinity Photo - a one-stop tool that I find so versatile.

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