Quote:
Originally Posted by Peter Ward
OK it's a 20"...but...does it have the following?
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- A 50kg instrument payload
It's debatable whether that is necessary, but easily achievable by simply putting the focuser on the spider.
- 100mm diameter instrument adapters
They quote M117mm thread pattern on the instrument flange.
- 90mm diameter fully corrected reducers and field correctors.
If you are using Alluna as your reference point, their corrector and reducer have usable fields of 65mm and 60mm respectively (not 90mm)
http://www.alluna-optics.com/product...corrector.html
The after market corrector and reducer from ASA have fields of 80 & 60mm.
http://www.astrosysteme.at/eng/correctors_rc.html
Under what circumstance is it necessary (or even desirable) to have a 90mm field?
- Zero image shift, servo controlled secondary focuser.
Simple, mount the secondary on an FLI PDF. Incidentally, strictly speaking there is no such thing as a zero shift focuser but there are several with tolerances which are adequate. (the PDF being one of them)
And forgive me if it comes across as unsporting, but I have to point out that the necessity of purchasing an aftermarket focuser because the manufacturer supplied unit is inadequate is not really indicative of engineering incompetence.... If that is not the case, tell me what function is served by the thing bolted to the back of your Riccardi Honders? (The Atlas focuser that is)
- Integrated touch-screen focus, environment and instrument rotator control
Why not automate these functions?
- Zerodur optics with a 98% strehl and 96% reflectivity.
GSO use quartz which is arguably better than Zerodur. They also quote 99% reflectivity in their coatings. The one thing I don't like about them is that they are dielectric so a complete pita to re-coat.
- Finite point analysis and machining to reduce dead weight by 80% or better
A better question would be; is the mechanical stiffness adequate? and is the weight of the ota manageable? When the majority of the ota is a carbon fibre truss, there is little extra dead weight to reduce. (I'm guessing your are quoting an Alluna brochure?)
Available as an aftermarket option.
Quote:
Originally Posted by Peter Ward
Large and elegantly engineered imaging telescopes up until now have not been cheap...hence, to use an automotive analogy, I'd very much like to see whether a Great Wall ute would seriously challenge the latest S-Class.
My money is still on the Benz.
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Well, if the task at hand was carrying a couple of 44 gallon drums across a freshly plowed paddock, my first choice would be a Toyota Hilux. The Great Wall would be somewhat down the list, but not nearly as far down the list as the Benz. Moral of the story: refinement is a wonderful thing, but gold plating a bucket doesn't help it carry water, it simply reduces the size and number of buckets that you might conceivably own.
best
c