Astrosystems 24"/Ostahowski mirror

[jetstream]

Here are a few pictures of my new telescope. It works very well. Thankfully Randy (owner Astrosystems) is an observer and many many great features are built into this scope such as the truss ring and the unconventional mirror cell (its not closed) that works superbly. This scope is easy to move in AZ at the zenith and offers ultra fast settling time. Collimation holds scarily well- note the very thick ply uprights where the spider is bolted to... and the truss ring has locating features built in.

Any questions ask away!

[jetstream]

It started to drizzle, so in the scope went- I'll post some side view complete pictures soon.

[FenlandPaul]

Wow! All these beautiful new dobs in here over the last few days!! 

Looking great Gerry - video tour of it requested!!

[Stu]

Looks fabulous Gerry. You can tell it's a big scope when it has four wheels on it! 👍👍

[Piero]

Stunning telescope! I look forward to reading more and more about it. 

The design looks great. Worth the waiting time!

[John]

Lovely - comes with a matching bench as well !

Looking forward to reports on how this one does under the stars Gerry (the scope rather than the bench !)

[Mark at Beaufort]

What a fantastic looking scope Gerry. We look forward to some great reports over the coming season. 

[scarp15]

Looks brilliant Gerry, the attention to detail, quality of workmanship, exemplary. For comparison, it would perhaps be interesting to see of a picture of this alongside your 15"dob (and maybe even 10").

[jetstream]

37 minutes ago, scarp15 said:

Looks brilliant Gerry, the attention to detail, quality of workmanship, exemplary. For comparison, it would perhaps be interesting to see of a picture of this alongside your 15"dob (and maybe even 10").

Sure!

I'll set them up once the sky clears.

[Littleguy80]

Congratulations Gerry. Looks superb. I hope you enjoy many great nights with it. Fingers crossed for Einstein’s cross  

[jetstream]

1 minute ago, Littleguy80 said:

Congratulations Gerry. Looks superb. I hope you enjoy many great nights with it. Fingers crossed for Einstein’s cross  

Thanks Neil, I'll need luck for Einsteins Cross...

Maybe a 40" dob would work?

[Littleguy80]

10 minutes ago, jetstream said:

Thanks Neil, I'll need luck for Einsteins Cross...

Maybe a 40" dob would work?

Haha maybe Santa will bring you one  

[mapstar]

Wow

Proper beauty Gerry and looks great. When will first light be? Look forward to reading how it compares with the 15" and how nice that mirror is? 

We're all waiting for the nights to draw in to get back to the deep sky stuff. 

Exciting times ahead 😉

[niallk]

Beautiful! Big congrats you are going to have some seriously fun times with that scope + your dark skies!

I didnt get what you mean about the 'not closed' mirror cell - any chance of a pic please?

(Yeah... i just want to see more pics so had to invent a question!!  )

[Paz]

That's a big scope! I'd be interested to know the focal ratio, and also the weight of the mirror box. I've picked up a 16" box in the past which must be a lot lighter but even that was tough.

[jetstream]

8 hours ago, niallk said:

I didnt get what you mean about the 'not closed' mirror cell - any chance of a pic please?

Thanks Niall, the mirror cell looks like there is little ventilation, but there is... it is calculated out I believe and the 15" with similar design can hold over 700x on lunar when seeing is excellent. The front on these are open. Very, very little stray light affects this scope. If I take it down again and with the mirror out I'll post pictures, for now I just want to observe lol!

Edited June 25, 2019 by jetstream

[jetstream]

3 hours ago, Paz said:

That's a big scope! I'd be interested to know the focal ratio, and also the weight of the mirror box. I've picked up a 16" box in the past which must be a lot lighter but even that was tough.

I easily lift my 15" Astrosystems box, mirror and all. The 24" goes 220lbs or so with the cell, bearings, mirror box and 80lb mirror. I can lift it all once off the rocker but need help if on it- we just did that to adjust the encoder pivot. Thankfully a friend happened by for a coffee.

The mirror is f4.1 at 2499mm fl.

[jetstream]

Here is the 15 f4.8" and 24" f4.1 for size comparison..

 

[Paul73]

That is what they call “a noticeable increase in aperture!”.

A lovely pair.

 

[niallk]

Beautiful looking instruments

[Piero]

6 hours ago, jetstream said:

Here is the 15 f4.8" and 24" f4.1 for size comparison..

 

Stunning scopes! Both!

[michael.h.f.wilkinson]

Amazing scopes, both of them.  Just have to mop up some drool from my keyboard

[jetstream]

As I report on how my new scope works it might be useful for members to see what spec mirror this is. It goes a true 1/6 PV with high strehl and is smooth (important). The secondary is a very high spec Antares, not sure where that paperwork went.

Ostahowski is a maker who's numbers I believe, Mr Nicols would be another.

I think its important to know that the interferogram is one of many tests that good opticians use- and that the others are important as well. The debate over smoothness can rage on among some, but for me it is an absolute requirement that the mirror is smooth- AFTER COATING as well as (obviously) before.

When asking for a mirror I am flexible as far as f ratio and thickness- this 2" thick 24" was exponentially easier to get the figure right than the thin examples and I'll deal with the equalization issue, so far so good!

 

 

[Piero]

Nice data, Gerry. The MTF is almost perfect.

My mirror didn't come with an interferometer test as John Nichol doesn't give you one. It's a PV 1/8 guaranteed and I trust his words, particularly given the fact that I haven't found one single negative comment about his mirrors, instead only very very positive statements.

It's made of Suprax and is 1.46" (37mm) thick. I didn't want something too thick due to the increase in cooling time, nor too thin as this can be more demanding on the mirror cell. It is also easier to make, also considering that is an F6. David Lukehurst and I decided to make three holes behind the mirror to increase air circulation. A fan was also installed, if cooling time is still too long or temperature changes occur. 

[jetstream]

Great choice!

Suprax is excellent, the jury is out on quartz for a variety of reasons. I just had a long chat yesterday about glass with someone in the know.. my 15" is Zerodur if I remember. As long as we use good glass, with no residual strain alls well.

We must trust the optician and he/she must have pride in there work. Your specs increased the chance of great specs hugely Piero and I believe your mirror spec might be understated. The real interferometer data is from pictures- I've seen my 15"'s and am told if the lines are straight alls well. That simple.

I don't blame top opticians for not providing interferometer data- it is hard to accurately replicate by others possibly and only promotes "armchair" discussion. For me the real test is under the stars and one simple thing seems to be apparent in good optical system and that is the snap focus. We keep in mind that eyepieces affect this too but you and I have narrowed down some EP's that have great snap themselves. ie ZZ, Docter.

I will be surprised if your new scope isn't a top tier performer. f6 is just so nice..