Ten-inch Ritchey-Chretien Astrograph scope

Messier 81 (sometimes called “Bode’s Nebula”) is a terrific target for astrophotography! Not only is it a pretty good visual target for my stargazes, it is a grand spiral that is just great in photos and this object has a special place in my heart because even back when I was still figuring out the early stages of all this astrophotography stuff I had an early and unexpected success with this object; one of my first truly deep-sky images with the Ritchey-Chretien 2000mm scope.

This was back when I really didn’t know what I was doing completely and was still sketchy on the details of true polar alignment and guiding the telescope with the computer. Somehow I managed to pull out a tiny victory which was a big boost to my confidence and showed me what might be possible after I got things better under control.

This was the first decent, in-focus, reasonably long exposure shot of a deep sky object I had ever taken up to that point, which was February 12th, 2018.

The stars were round, you could see spiral arms; I was thrilled! Never mind that the core of the galaxy is completely blown out and the color sucks; this was gonna work! (eventually)… A little light at the end of this 12-million light-year-long tunnel!

So fast forward a few years and I have tried to improve on this image a number of times and made some progress for sure but it always felt like it came up “underwhelming” somehow.

I tried again in 2020 and used a wider field telescope this time because a shorter focal length scope is much easier to control on the mount even if it’s not zoomed in very much. I had two years more experience processing astrophotos in Photoshop and that makes a huge difference too. So on March 22, 2020 in the middle of the Covid-19 pandemic I shot this from the sidewalk in front of my condo:

Galaxies M81 & M82 with NGC 3077 “photobombing” on the left.

There’s some decent color there, spiral arms are well defined, M82 (upper right) has the characteristic red streamers because I was now using multiple layers of shots with various filters and layering them in the computer. Processing in Photoshop is a huge deal…

Observatory On

So after the observatory was built, the first scope I had up there was a wide-field telescope, the RASA eleven inch and I thought that being on a super steady pier, with the dark skies out there, taking long exposures with very fast optics I was going to get the shot of a lifetime! But sadly, as I started processing it I realized that this was not going to be “the one” which was disappointing. Disappointing enough that I stopped working on it, but this is what I had:

To be sure, there’s some things to like about this shot. First of all the fact that I took 300 minutes (5 hours!) of exposure time with a very fast optical system (more light to your camera, faster) gives some real density to the clouds of gas in the spiral arms. But in order to get that during processing, my stars started getting bloated and I discovered that even though this was shot with a color camera, there wasn’t much color there and this is probably because with the RASA scope design, the camera is at the front and if you want to change a filter you have to actually be there at the scope to manually slide the new one in, and I wasn’t.

Better Color from Monochrome

The color camera is a full-frame camera so the image was pretty large on the sensor but still, most of the shot was wasted around the object since the RASA is a wide-field scope by design.

Well, it’s springtime now and that means “Galaxy Season” so now that the observatory has been open a few months I thought I would put the 2000mm focal length Ritchey-Chretien scope up at the observatory until we get into the main part of summer and all the great Milky Way and nebula shots you can get.

So, after some careful mirror alignment with some new helper software, I decided to give M81 a solo shot closeup try.

I outfitted the scope with my 60-megapixel monochrome camera and the filter wheel so I could have my choice of seven different filters at the push of a button. The 2000mm focal length means that this setup has more than 3 times as much magnification as the previous one, so that’s better detail in the photo.

I decided not to press my luck with guiding so I only took 2-minute exposures totaling 2 hours of luminance, 40 minutes each of Red, Green, and Blue, and over an hour and a half of “hydrogen” light to try and get some good pink color in the star-forming regions in the spiral arms.

At long last here is what is probably my best astrophoto to date, and I’m really happy it was done with the Ritchey-Chretien which has been a real bugger to control up to this point.

Here is the final version of M81

Messier 81 taken from Sky Guy Observatory, March/April 2022 Click for a much larger image.

This was a great result and a joy to process in the computer.

The Deep Dive

When you are processing these images, quite often you have to zoom waaaay in to check on elements of image detail, aligning your Red/Green/Blue and other layers, evaluate noise, erase pesky “hot” pixels that ruin the beauty of the images and perform other cosmetic editing. While doing this you notice these really dim smudges of light that don’t look like stars.

When you are shooting galaxies, there are always some really faint fuzzy things in the background which are usually really, really far away so I like to get out a detailed galaxy map and see just exactly what might be lurking in one of my images. These are the tiniest smudges of light on the camera sensor but still, unmistakable if you know what you’re looking for. Here are some of them:

A new distance record!

This one is actually “shining through” M81 itself from the background.


I’ve got a number of galaxy shots planned for the next few months so check back every now and then!

Bill Gwynne
aka Bill The Sky Guy
Hilton Head, South Carolina