What is the sharpest <300mm focal lenght telescope/lens ? Generic equipment discussions · Luka Poropat · ... · 40 · 1738 · 9

Luka Poropat:

Karl Theberge:
but I am quite familiar with rude poeple and you, my dear, do not invite to discussion at all.

My intention wasn't to be rude, but to ensure accuracy in our discussion. Precision matters in technical matters like this. If there's a mistake, it's important to correct it for the sake of clarity and understanding.

Dan:
Sharpness is just one consideration. The Rokinon 135 has a good reputation for sharpness, but many copies suffer from other optical issues, ones that can’t even be patched up with AI or even by adjusting the iris.

Luka Poropat:
Can we consider a Sigma 105 F/1,4 ART in this lineup ?
There are few people here that use it with various cameras and various apertures, from fully wide open to F2.8 where most deem it optically perfect.

• Redcat 51 - I bought this awhile back and it's a solid performer. The illumination drop in the corners looks to be 60-70% though judging from the flats, but there's very little astigmatism I can find.
• Rokinon 135 - I haven't actually tested this one on the full frame sensor, but performed ok on the 2600mc. I say "ok" because I had to stop it down to ~F4 before I could get decent stars in the edges of the aps-c. That said, it's lightweight and it's well supported in the accessory community (designing new rings for each of these gets painful eventually)
• Sigma 105 f1.4 ART DG HSM - I tried this beast on a recommendation. There's a lot to like about the lens. It pours light in @F1.4 and almost completely covered the full frame sensor in 10s Lum exposures. Unfortunately I had to stop it down past F4 to control the astigmatism. I ended up returning this one, maybe it was a bad copy?
• Zeiss Milvus 135 F2 - Having been dissappointed on the Sigma, I found a great deal on this lens. Going off reputation, you'd think it was the holy grail or something. The Zeiss's are at least nice that they have mostly manual focus and aperture control (the sigma was a little annoying to adjust aperture). I tested this and it was actually really good. Full out, the illumination was solid across the frame. at F2 there were certainly artifacts, but the at F4 they were gone completely except in one corner. (and there it was minimal). The most difficult part of this lens was mounting it. I had to get little jacksony pollock in order to provider a sturdy hold for it since the outer shell of the body moves while focusing. Tilt and backfocus definitely need adjusting though, so i'm still battling through that since most of the adapters seem to expect it'll be fine and don't leave room for adjusters.
• Nikkor 300mm F2.8 ED VR I - I bought this one recently. It's slightly older (~2009). It's huge and at 300mm, the field is a bit narrower. That said, it performed pretty well over the whole field once I got to F4.5.
• Nikkor 180 f2.8 ED - yet to try

• Focal length 130-230ish
• larger first element (~85mm +)
• can produce astimatism free (or close) stars across a full frame at <F4
• costs less than $2k
• ideally allows for connecting with some means of backfocus and tilt correction (most adapters make this challenging)

Dave Erickson:
Plenty of logical errors here... Check your units...