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Contains:  Triangulum galaxy, M 33, NGC 598
Getting plate-solving status, please wait...
M33 Pinwheel Galaxy, 


            Barry Brook
M33 Pinwheel Galaxy

M33 Pinwheel Galaxy

Technical card

Resolution: 1516x1125

Dates:Sept. 17, 2014Sept. 22, 2014

Astronomik Ha 12nm 1.25'': 16x900" 3C bin 1x1
ZWO optical ZWO RGBL Filters: 142x100" 3C bin 1x1

Integration: 7.9 hours

Darks: ~70

Flats: ~100

Bias: ~500

Avg. Moon age: 25.68 days

Avg. Moon phase: 19.64%

Bortle Dark-Sky Scale: 7.00 job: 383609

RA center: 23.466 degrees

DEC center: 30.671 degrees

Orientation: -89.044 degrees

Field radius: 0.459 degrees


M33 is a classic northern hemisphere DSO. However, I thought I'd take a challenge and capture it low on the horizon from the south (it never rose above 22 degrees altitude). There was also substantial light pollution and a hazy atmosphere to peer through, and it was imaged through an achromat (at f/4), which meant that it was impossible to gather focused Luminance frames (so the Lum was synthetic, based on a weighted blend of the R, G and B channels and Ha data).

The overall result is not great (the R and B channels bloat badly with the achromat - this is really only good as a narrowband astrograph), but at least I can say I tried!

Ha = 16 x 900 sec
R = 48 x 100 sec
G = 44 x 114 sec
B = 47 x 92 sec

(RGB sub-length determined for optimal colour balance). Ha-R was used for the R chrominance channel. Post-processed using Startools.

For now, I think I'll keep the achromat for exclusively NB imaging!



Barry Brook
License: Attribution Creative Commons


  • M33 Pinwheel Galaxy, 


            Barry Brook
  • Final
    M33 Pinwheel Galaxy, 


            Barry Brook

Sky plot

Sky plot


M33 Pinwheel Galaxy, 


            Barry Brook