Interferometry Tests

[garymck (Gary)]

Haven't seen this link before:
http://fidgor.narod.ru/Observers/test.html

Moscow Astro Society optics lab, apparently very reliable "take no prisoners" tests.

Horrifying results even allowing for the fact that the scope sample may represent unhappy owners...

Gary

[casstony]

There's a bit of variety there Gary; which tests in particular do you find horrifying?

Strehl ~ 0.9 is ok in a cheaper instrument. I wouldn't be happy paying Tak prices for 0.9 strehl though.

[garymck (Gary)]

Have a look at the Skywatcher Newt tests, a couple of good ones and a heap of horrifying ones - down to one wave accuracy..... Not sure I'd buy a mass produce scope any more...

The sample may be skewed though, as those who are happy may not bother to have them tested.

How about a TOA 150 that is barely 1/4 wave?

cheers
Gary

[casstony]

Originally Posted by garymck

Have a look at the Skywatcher Newt tests, a couple of good ones and a heap of horrifying ones - cheers
Gary

I didn't see the categories below the refractors, maybe for the best

It's a little disconcerting that they'd let such poor mirrors go to retail.

[Wavytone]

Many interesting things in that lot.

First the Meade/Celestron SCT results consistently in the range strehl 0.7...0.9; makes a mockery of some of the claims over at Cloudynights.

Secondly there’s a TS 130/910 APO at at 0.957 yet another at 0.77... ok it’s only a sample of 2 but consistency could be a problem... good ones and bad ones...

But check out all the maks from Intes/Intes-Micro... all well above 0.9 and one at 0.97.

And lastly the camera lenses ... including an old MTO 10/1000 telephoto (0.4)

[Stefan Buda]

Interesting.
The only premium astrograph I could find on their list was an ODK16, which was so bad that it was impossible to put a figure on it.

[Atmos (Colin)]

With the vast array of newtonians in that list, I do wonder how many had poor results purely from the secondary mirror?

You hear a lot about how consistently the 8-12” primaries are these days due to producing tens of thousands of them.

[Merlin66 (Ken)]

Interesting that the SW ED80's come through pretty well, Strehl 0.97

[DarkArts]

Originally Posted by Merlin66

Interesting that the SW ED80's come through pretty well, Strehl 0.97

Yes, I noticed that, too. (... as he looks admiringly at his own gold tube ED80 sitting in the corner ...)

[DarkArts]

Originally Posted by Wavytone

First the Meade/Celestron SCT results consistently in the range strehl 0.7...0.9; makes a mockery of some of the claims over at Cloudynights.

That was a tad concerning, and I looked very closely at the Celestrons. On the other hand, my grey tube C14 gives me the best planetary views I've yet seen at the eyepiece. Maybe I have a good example, or maybe I just need to look through a few good scopes for comparison?

[bojan]

I have Rubinar10/1000..
After "relaxing" the main mirror, it was much better performer (it suffered from astigmatism, induced by primary mounting ring and silicone rubber). Not sure about numerical improvement, of course.

[Wavytone]

Hi Bojan, Many years ago I had an MTO 10/100, very heavy with a two-element Maksutov corrector that must have had the best part of 40mm solid glass up front.

Like yours the primary mirror retaining ring had been screwed up by some Russian gorilla and after releasing that it was optically much improved, but still quite inferior to the little Meade 4” f/10 SCT I had at the time.

When I’m home later this week I’ll try to make a Foucault-gram of the Santel and compare with the interferogram that came with it. It’s strehl is supposed to be 0.965 so will be interesting to see.

[LewisM]

Santel tests TERRIBLY: http://fidgor.narod.ru/Observers/Test/test_280.html

Really...terrible. Sell yours Wavy...to me

[billdan (Bill)]

Originally Posted by Stefan Buda

Interesting.
The only premium astrograph I could find on their list was an ODK16, which was so bad that it was impossible to put a figure on it.

Not surprising when you read some of the horror stories on Cloudy nights about their bad quality control.

[Wavytone]

Lewis you will have a very long wait