M81, M82 – Bode’s Galaxies

I wanted to fit M81 and M82 in the same frame and it’s actually what I did the first night I had the 8″ RC out. However, I wasn’t entirely satisfied with my framing (I didn’t expect M81’s faint arms to be this large) so I ended up shooting them separately on the course of two nights. I had quite a bit more integration time on M82 which made the Signal/Noise ratios better than of M81 (a little bit more on this below). That resulted in a mosaic a little more challenging than it could have been.

Overall it’s about 8 hours of integration time. I stacked them separately using Entropy Weighted Average in DSS. Pininsight 1.7 was used to process the images (including creating the mosaic). Once more, what a great piece of software. I really, really recommend it.

Both nights were pretty calm. I expected a little more of January 18th but some technical difficulties with guiding prevented me from shooting NGC2359 as I originally wanted. But the weather forecast for next week isn’t nearly as bad as I thought and I may end up going to Anza next week-end…

As I said above, creating a mosaic of two images with different integration time made me realized the goodness of stacking. This is even more true for long exposures (I am mostly talking about 10mn exposures). I have about 25 10-minute subs on M82 and only 6 on M81. Considering the very faint nature of NGC2359, I guess I’ll mostly spend my time doing 10-minute exposures and I will need at least 4 hours if I want to keep my noise as low as it was with M82.

No more talking here’s my 2-pane mosaic of the Bode’s Galaxies: M81 and M82. Technical details listed below the picture.

  • Date: December 26th 2011 and January 18th 2012
  • Camera: Canon 500D Baader Modified and CP30T-EOS Cooled (Sensor maintained at 10 C – Exif temperature: 10 C)
  • ISO: 1600
  • Exposures: ~ 8 hours of integration time (2 pane mosaic and composites of 120 s, 300 s and 600 s subs)
  • Mount: Losmandy G11 Gemini 2
  • Imaging Telescope: AT8RC w/ AT2FF
  • Guiding Telescope: AT65EDQ w/ SSAG
  • Calibration: Darks, Flats
  • Stacking: DSS (Entropy Weighted Average)
  • Final blending/processing: PixInsight 1.7 and Adobe Photoshop CS5
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