M106 Galaxy in Canes Venatici

The bright beautiful spiral galaxy at the center of this photograph is Messier 106. Located near the handle of the Plough (also known as the Saucepan and the Big Dipper), it is about 80 000 light-years across and 23.5 million light-years away. As is typical in spiral galaxies, there are dark dust lanes, young blue star clusters and pinkish star forming regions distributed along the spiral arms, and a bright nucleus of older yellowish stars at the centre.

IAU and Sky & Telescope magazine (Roger Sinnott & Rick Fienberg)

NGC 4217, another prominent spiral galaxy, is also framed in the wider of the two views above, positioned below and to the right of M106, and viewed nearly edge-on. It is estimated to be about 60 million light-years away. Actually, there are several other less prominent galaxies also visible, as annotated below.

Annotated view around M106 (86.4 × 58.8 arcmin).

Technical problems

I have found I need to refocus rather frequently recently, roughly every hour. Probably part of this is due to the large temperature swings (roughly 10 degrees Celcius) we are having over night at the moment. For this amount of cooling, my aluminium telescope tube contracts by about 0.2 mm, which seems to be significant in terms of focus.

I also believe my push-fit field flattener may be slipping. I actually binned one whole night of subs on M106 because as I began to process them, I noticed several brighter stars had pronounced and elongated halos. When I investigated, I found the flattener assembly had slipped and was slightly not perpendicular to the optical axis. I pushed it together again, firmly tightened the thumbscrews, tried again on another night, and gathered the data that produced the images above. The issue is not entirely resolved, but is at least far less prominent. I now need to investigate whether my Revelation Adjustable Field Flattener can accept a screw-fit adapter instead.


  • 80× 300-s light frames (Gain 900), 6 h 40 min total exposure time
  • Full use of calibration frames (darks, flats and dark flats)


  • Explore Scientific ED 102 mm Apo f/7 refractor
  • Sky-Watcher EQ6-R PRO SynScan GOTO equatorial mount
  • Altair Hypercam 294C PRO colour fan-cooled camera
  • Altair quad-band one-shot colour (OSC) 2″ filter
  • Revelation Adjustable Field Flattener
  • Altair 60mm guide scope
  • Altair GPCAM2 AR0130 mono guide camera


  • Sharpcap
  • PHD2
  • DeepSkyStacker
  • Photoshop
  • Gradient XTerminator

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