Canon EOS R8 and My Questar Restomod

After a good amount of foot dragging, I finally obtained an M42-to-RF lens mount adapter to pair my Canon EOS R8 with my 1962 Questar restomod.

To be sure, my Canon EOS M200 has served me very well over the four years I’ve owned it, and I will continue to use it for certain applications. But the fact of the matter is that it is a more basic model in Canon’s mirrorless camera offerings. Its cropped sensor simply doesn’t have the low-light performance that my R8’s full-frame sensor has. I was keen to be able to attach it to my Questar, which photographically operates at f/16 and which requires a camera with all the low-light capabilities it can get.

One thing that the little M200 still has going for it is its small size and lightness. It doesn’t exert a ton of downward force when it’s attached to the back of my Questar. I immediately found that the heavier R8 does have a little more pull. Although it’s not bad, I do have to engage the altitude brake knob, which I never had to do when I used my M200 with the scope.

My first target was the backyard hummingbird feeder. Today’s weather is a bit hazy, and my mid- to late afternoon sunlight wasn’t all that great. Still, I managed to get a halfway decent shot of an Anna’s hummingbird perched at our feeder at a distance of about 30 feet:

Here’s a 100% crop of that same image:

As always, the Questar does a fantastic job with resolving whatever it’s pointed at. Since my light was awful, and since late afternoon heat was probably causing a fair amount of image-blurring convection, I’m going to reserve judgment on how well my R8 controlled higher ISO noise. At first glance, it doesn’t look like it did a bad job.

All this while, I had been using a camera with a cropped sensor with my Questar. One advantage of doing so is that it reduces the amount of vignetting in an image. A wide-field Questar will come close to illuminating the entire frame of a cropped sensor, but it will not with a full-frame one. Curious to know how bad that vignetting was, I pointed the scope straight up into the sky and shot this image:

Even in spite of my Questar having had a wide-field conversion done to it by its original owner in the mid-1960s (see this page for more information on the wide-field construction), images made with a full-frame sensor have significant vignetting. You can crop out that vignetting, but doing so will reduce the number of pixels in an image and will ultimately reduce resolution for a given enlargement. But I’ll still benefit from my R8 sensor’s low-light performance. As times goes on, I’m curious to see how well that compromise shakes out.

One thing my Canon EOS M200 still has going for it is the way it packs in more pixels into the Questar’s area of illumination. For bright objects like the Moon, that works well. I imagine I'll continue to use my M200 for lunar astrophotography.