Bode’s Galaxy

As I noted in my post on my most recent M33 image, I’ve long admired many of the starburst galaxy images I’ve seen with continuum subtracted nebulosity data. M33 was my first go at it, and I thought I might give it a try on M81 and M82 as a mosaic. To remind myself how to accomplish the processing, I went ahead and tried my hand at processing M81 on its own since I will be collecting the RGB data for M82 tonight. I collected the narrowband data a few weeks ago (under a full moon… but it was the first time we had clear skies in a month!), and finally had the chance to collect the RGB data last night since the skies were clear and the moon is mostly done for this phase. M81 and M82 are toward Denver’s light dome, so even though I crossed my fingers and hoped for it, I didn’t really capture any of the faint IFN in the region. As with before, I still found continuum subtraction to be challenging, especially so with this target since all of the nebulosity is small (about the size of a star, which StarNet typically will remove, making the subtraction processing a bit more challenging).

Also of note, for the RGB data in this image, I finally made the switch to an Off-Axis Guiding solution: the Antlia OAG with Filter Drawer. I chose it because of the larger prism for my 174mm guide camera, built in filter drawer, and it’s plug and play ability to fit into the standard 55mm back focus dimension (it’s 37.5mm thick, so It works with cameras that have a 17.5 or 6.5mm + 11mm spacer amount of back focus to the sensor, like all ASI cameras). It took a little bit of fiddling but I was able to quickly find some stars and get it working. I must say, it was quite an improvement over the separate guide scope solution! Stars were much more round all night, and there was less (non-dither related) target drift throughout the night.

Overall, I think the image turned out great. Keep an eye out for an individual version of M82 and then a combined mosaic of M81 and M82. The mosaic may look a little bit different since I will probably reprocess both M81 and M82 from scratch for the mosaic.