Astro Testing the Canon 77D

I wanted to test the ISO capabilities of my Canon 77D with my new cut-down tracker.
I spent a cold hour out on the ranges, having waited a couple of weeks for a clear night...
All images were taken on the 77D, with Sigma 10-20mm lens, set at 10mm, f4.0, manual focus.
Here are the results:

ISO6400, 8sec (100% crop)

This base shot shows the noise clearly at ISO6400

ISO400, 8sec (Underexposed by 4 stops,
then exposure corrected in Lightroom)

At ISO400, underexposed by 4 stops (the same 8sec shutter), we can bring back the exposure in Lightroom. You can clearly see the noise level is similar to the ISO6400 shot, maybe slightly worse

ISO400, 2mins (Untracked)

The decrease to ISO400 and increase in shutter speed to 2mins (4 stops or x8) gives the "correct" exposure for ISO400. There is considerably less noise, but at this long shutter speed, you can clearly see the stars trailing due to the rotation of the Earth

ISO400, 2mins (Tracked)

By taking the same shot again, but on a tracker, we get the benefit of less noise and a "correct" exposure without star trailing

ISO200, 4mins (Tracked, full shot)

The full sky shot at ISO200, 4mins. The sky has little noise. There is some movement in the starts as my tracker wasn't set up exactly pointing to the North star. You can see the movement in the ground/horizon as the camera moves over the 4min exposure.

This means that for a tracked shot, a separate foreground shot will be needed to blend in after.

For anyone interested, I built my barn door tracker based on the plans at this site.

I then cut it down to a smaller (half length) size to make it easier to transport. The only adjustment needed is the screw has to be turned a full rotation every 2 minutes instead of every 1 minute. Seems to work quite well and far cheaper than a "proper" star tracker.

My cut-down (half size) barn door tracker

---- BONUS SECTION ----

I also tried to get some tracked pics of the Orion nebula, using my Sigma 300mm lens and the tracker. This is a composite of 20x shots taken at ISO6400, f4.0, 8sec. I used the Sequator app to do the stacking.

Here's a "real" shot from the internet (left) and mine (right). Not quite as good, but at least I've captured it!