Reviving this thread from last year. Read through a bit, and it is entirely too positive. There must be something about this scope (besides mirror shift) that needs improvement... time to raise some stink.
One of the things I've been stymied by is the inability to see any fringes on the supplied diagonal's mirror using a contact flat. The reflectivity is so high, the fringes are invisible. This means that I can't test the mirror surface flatness against a reference, and am left to using more subjective methods.
A couple days ago I was doing some daytime terrestrial viewing of objects on nearby power poles. One of the experiments was to check out the relative difference in sharpness and contrast between the 7 diagonals I have on hand; 2 prisms and 5 mirrors. I did this using the 180 Mak at high magnifications (300X and 400X) and swapping in the various diagonals, making note of the features on a small white ceramic fixture with black logo and print on it, against the background of the textured power pole and behind it, the blue sky. (We have plenty of clear blue sky during the day; the clouds roll in early evening...)
Both prisms won the test, with two of the mirrors not far behind. The loser was the diagonal supplied with the Mak. Despite its high reflectivity, its contrast and sharpness was worse than the others at these high mags. Not horrible, but noticeable.
Having just finished remounting the secondary of my SW350 dob with excellent results, it seemed prudent to look at how the mirror is mounted in this diagonal. I had taken a quick peek a few months ago and it looked like it was siliconed in place with the usual three dabs. But on closer inspection, I see that's not the case. See the pic below.
The mount consists of three rubber standoffs (aka feet or bump-ons) about 3/8" in diameter, stuck to the mirror with 2-sided tape. These then are glued (with red silicone, I presume, but who knows?) to the diagonal's back plate.
Maybe it's not as bad as it could be because of the 3-point mount. But I have yet to see a mirror perform well when 2-sided tape is used to secure it in any way.
So this project will be to remove the rubber feet, remount it properly, and do the test again. Based on past results, I am betting it will bring the performance of this diagonal right up there with the best of the mirrored ones.