Narrowest 393.37 ever by Apollo Lasky

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Re: Narrowest 393.37 ever by Apollo Lasky

Post by bart1805 » Thu Oct 11, 2018 8:16 pm

Found this information about a UV-Barlow lens.
https://www.astrosystems.nl/uv-barlow-

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Re: Narrowest 393.37 ever by Apollo Lasky

Post by TheSkyBurner » Wed Oct 17, 2018 1:41 am

bart1805 wrote:
Thu Oct 11, 2018 8:16 pm
Found this information about a UV-Barlow lens.
https://www.astrosystems.nl/uv-barlow-
Very nice, too bad it costs $800 to build it. :(

Uv lenses are not cheap.

I did happen to figure out a solution as well, and mine costs 1/10th as much and works with all telescopes. Not just that one sct..

(i just re-read that document, and the guy made an entirely new corrector lens for his sct. So that barlow will be questionable for comparative sct results..)

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Re: Narrowest 393.37 ever by Apollo Lasky

Post by krakatoa1883 » Wed Oct 17, 2018 11:49 am

As a starting point it would be enough to use a barlow fully transparent to the UV. At slow focal ratios even a single long focal lens would work fine
20151021.jpg
20151021.jpg (11.89 KiB) Viewed 339 times
while for fast f/ratios a singlet would not be enough due to increasing spherical aberration. Of course if one needs a telecentric system things become more complicated anyway.
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Re: Narrowest 393.37 ever by Apollo Lasky

Post by marktownley » Wed Oct 17, 2018 12:38 pm

Good point Raf. What lens is that one you used?
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Re: Narrowest 393.37 ever by Apollo Lasky

Post by krakatoa1883 » Wed Oct 17, 2018 2:30 pm

This one from Edmund Optics

https://www.edmundoptics.eu/p/25mm-dia- ... lens/8568/

it was just an experiment but gone very successful. One can obtain even better results by a plano-concave (instead of a double-concave) lens provided with a UV-AR coating that covers 250 to 425nm, the price difference is small and worth the extra money.

Lenses can then be easily mounted in T threaded barrels

https://www.edmundoptics.eu/p/25254mm-d ... unt/10576/
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Re: Narrowest 393.37 ever by Apollo Lasky

Post by marktownley » Wed Oct 17, 2018 7:18 pm

Very interesting Raf, which is the plano concave lens you tried?
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Re: Narrowest 393.37 ever by Apollo Lasky

Post by krakatoa1883 » Thu Oct 18, 2018 7:08 am

This is the page

https://www.edmundoptics.eu/p/250mm-dia ... lens/8557/

look under Technical Images in that same page for further information on how the lens works.

Choose the focal length based on the amplification you wish to obtain, ideal would be a long f.l. lens (say 100 mm) as this helps to contain aberrations, however if you have to amplify much (3x - 4x) a long f.l. would lead to a cumbersome (very long) optical train. The slower the scope the better the performance, no good with my newtonian at f/5, for example, much better at f/10 or slower.
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Re: Narrowest 393.37 ever by Apollo Lasky

Post by highfnum » Mon Oct 29, 2018 3:11 am

very interesting!

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Re: Narrowest 393.37 ever by Apollo Lasky

Post by highfnum » Tue Oct 30, 2018 4:35 pm

i sent email to chroma
no response

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Re: Narrowest 393.37 ever by Apollo Lasky

Post by highfnum » Sun Nov 04, 2018 7:30 pm

sent e-mail over a week never got an answer back

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Re: Narrowest 393.37 ever by Apollo Lasky

Post by TheSkyBurner » Sun Nov 04, 2018 8:01 pm

highfnum wrote:
Sun Nov 04, 2018 7:30 pm
sent e-mail over a week never got an answer back
they wont respond, because I canceled the project. Sorry!

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