Observation by Graham Roberts: Messier 51

Uploaded by

Paul Downing, FRAS


Graham Roberts


2020 Apr 01 - 22:00


2020 Jun 16 - 13:48


The Whirlpool Galaxy (M51)

Planetarium overlay


Canes Venatici

Field centre

RA: 13h29m
Dec: +47°11'
Position angle: -103°57'

Field size

1°05' × 0°53'

  • William Optics GT81 + Focal Reducer FL 382mm f4.72
  • ZWO ASI1600mm Pro camera

L x 95 R x 62 G x58 B x 66 Ha x 46 = 327 x 180 sec


Redhill, Surrey, UK


Messier 51

About this image

It was a great pleasure to image M51 over no less than seven nights in March and April this Spring which, combined with last year’s data, resulted in over 16 hours integration time, substantially longer than any previous image I’ve compiled before.  Moreover, the quality of seeing also benefitted SNR and guiding quality, thus achieving RMS errors of at least 0.80 arc seconds or better.  I did encounter some plate solving issues and had to resort to manual framing on a few nights but fortunately DSS software dealt with alignment OK and the final image is all I could have hoped for.  Naturally the interaction of the two galaxies is the signature feature of this image but it is the improvement in general colour, detail and addition of Ha-subs highlighting regions of new star formation, that have been most transformative in portraying these objects in all their glory.

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