Re: Inexpensive Telescope Design Revealed

bratislav3162@xxxxxxxxxxx wrote:
> SCT plates are made in thousands by simple vacuum method. And they
> are making them rather well these days - can't see how can anyone
> improve on that price wise.

I thought it was still true that only a small handful of companies make
them - basically, Celestron and Meade. Bausch and Lomb still makes
other types of telescope, but was driven out of the SCT segment.

And, thus, while we are seeing inexpensive Maksutov-Cassegrain
telescopes from China, we are _not_ seeing SCTs from there. Presumably
even they are afraid of being sued for invading the trade secrets of
Celestron and Meade - or, at least, without access to trade secrets,
making such plates is still difficult.

But if one has light from a basically uncorrected spherical primary
going to a secondary, while this can be done - Ralph W. Field's
telescope, or the Pressman-Camichel - either one has to have a large
central obstruction, or a primary mirror with a high f-ratio (and hence
a long telescope), because aberrations become too wild near the focus.

Still, I did indeed use an optical design program to optimize the
design as given; although it wasn't exactly what I was seeking, I
thought it worthwhile.

John Savard

.

Relevant Pages

  • Re: LX200R
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    (sci.astro.amateur)
  • Re: 14" verses 12"
    ... 127-mm Orion/Syntha Mak. ... Orion Maks are certainly the best bang for the buck for that type of telescope ... 8-inch SCT nearby. ... Maksutov but it was not capable to hold water. ...
    (sci.astro.amateur)
  • Re: 14" verses 12"
    ... Well, I assumed that the original poster was talking about the same telescope, ... and so the central obstruction should scale from 12 to 14 ... I also agree with the 8-inch SCT, and would add that the Orion 150mm Maksutov is ... I think it is okay if you compare apertures within the same coating ...
    (sci.astro.amateur)
  • Re: 14" verses 12"
    ... A friend of mine compared the views against his 8-inch ... SCT, and said the 127mm version gave sharper and more contrasty views, enabling ... Maksutov but it was not capable to hold water. ... I agree if the original poster is after a telescope for planetary ...
    (sci.astro.amateur)
  • Re: 14" verses 12"
    ... A friend of mine compared the views against his 8-inch ... SCT, and said the 127mm version gave sharper and more contrasty views, enabling ... Maksutov but it was not capable to hold water. ... I agree if the original poster is after a telescope for planetary ...
    (sci.astro.amateur)