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Classic, not catadioptric, Cassegrains


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I think the Tak Mewlon is a Dall-Kirkham Cassegrain. I can't be certain without looking it up but I think the figure on the mirrors is a parabolic primary, hyperbolic secondary, but I stand to be corrected on that if I'm wrong (corrected! - that's funny!!). I don't think its possible to create an all spherical Cassegrain without the use of a corrector of some kind.

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1 hour ago, mikeDnight said:

I think the Tak Mewlon is a Dall-Kirkham Cassegrain. I can't be certain without looking it up but I think the figure on the mirrors is a parabolic primary, hyperbolic secondary, but I stand to be corrected on that if I'm wrong (corrected! - that's funny!!). I don't think its possible to create an all spherical Cassegrain without the use of a corrector of some kind.

Dall-Kirkham's use an Elliptical primary and a spherical secondary https://en.wikipedia.org/wiki/Reflecting_telescope#Dall–Kirkham

They do need correctors though by the seems of things.

If 25585 is looking for "classic cassegrains" I would imagine a Ritchey Chretien would be what they are looking for, though they have some serious ££££ attached to them.

https://www.teleskop-express.de/shop/product_info.php/language/en/info/p6882_TS-10-inch-f-8-Ritchey-Chr-tien-Astrograph---carbon-truss-tube.html

Only 2'500 euro!:crybaby2:

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1 minute ago, Peter Drew said:

I have four 12"  Cassegrain telescopes in my "collection". 2 Dall-Kirkhams, 1 Dall-Kirkham-Dall and 1 classical. Neither has or needs any corrector for visual use.  :icon_biggrin:

So you use them with nasmyth focus or cassegrain focus for visual use? I've always though nasmyth focus would be very convenient (the eyepiece never has to move vertically in relation to the observer, or in any fashion if the telescope moves on a rotating plate, though that's probably a bit high end)

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5 minutes ago, 25585 said:

What is the Vixen VMC200L, as it has no plate or lens?

The Vixen website says:

"The Vixen VMC200L Reflector Telescope is a unique 200mm 8 inch catadioptric optical system. It incorporates a primary mirror and a meniscus corrector just before a secondary mirror. By doing so, light is corrected twice on the optical path. The end result is that spherical aberration and field curvature are corrected to a high degree of optical performance"

So it has a corrector in front of the secondary :) Not sure if the design has a name, though I'd imagine not since it seems quite exotic.

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7 minutes ago, pipnina said:

The Vixen website says:

"The Vixen VMC200L Reflector Telescope is a unique 200mm 8 inch catadioptric optical system. It incorporates a primary mirror and a meniscus corrector just before a secondary mirror. By doing so, light is corrected twice on the optical path. The end result is that spherical aberration and field curvature are corrected to a high degree of optical performance"

So it has a corrector in front of the secondary :) Not sure if the design has a name, though I'd imagine not since it seems quite exotic.

Hidden in the secondary mirror cel by the look of this

 

vmc200l_diagram.jpg

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3 hours ago, SteveWolves said:

There is the Takahashi cn212

There was a 2nd hand one of those scopes on Rother Valley Optics site, a few months back. Looked devine and a decent price for a Tak, if i remember correctly?

 

Andy

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48 minutes ago, dweller25 said:

I think it wad for sale for close to £3000

They were asking that. I saw the scope at the International Astronomy Show last Autumn. Quite impressive but it had been well used and showed some signs of wear and tear. My guess is that they accepted a lower offer eventually - it was up for sale fore quite a few months.

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1 hour ago, John said:

They were asking that. I saw the scope at the International Astronomy Show last Autumn. Quite impressive but it had been well used and showed some signs of wear and tear. My guess is that they accepted a lower offer eventually - it was up for sale fore quite a few months.

I considered buying it but it seemed quite pricey as it was very well used and due to age the mirrors may have needed re-coating in the near future. A brand new Tak Mewlon 210 was cheaper too. Ultimately I decided to settle with my refractors.

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