Re: [ATM] Banishing the diagonal

[Andy Saulietis <iss@pvtnetworks.net>]

Don Clement writes:


> > You are right of course. I completely forgot the heat factor and,
> > that consideration is not likely to go away unless there's a
> > major breakthrough in technology.
> >
>
>I see no reason why the cooled ccd detector has to generate heat in the
>optical path. One method might be to insulate the detector ( vacuum?) and
>carry the heat generated by a thermoelectric cooling device  away using a
>liquid in insulated  tubing. Or use remote cooling with the cooled liquid
>piped to the ccd in insulated tubing.

There's also heat transfer pipes..these move heat by
enclosing a volatile liquid (freon?) in a closed insulated tube..
heat moves by rapid convection to the cold end which
can be actively or passively cooled/radiated away.
Similar technology is used in sodium-cooled valves in
car engines, but at much highter temps than for a CCD.

Re using relay lenses to minimize secondary size..a couple
of decades ago I built a relay system for a 10"f4.5 that
both amplified the image and moved it to a location
outside the OTA with the focuser near the primary mirror
end. An enlarging lens (the kind used in photo enlargers)
was used to relay the image several feet at 4x mag, with
2 diagonal mirrors. It was OK for planetary /lunar use
and comfortable to use (like a refractor) but had waaay too much
scatter from all the additional surfaces, and extraneous color
from the enlarger lens.




Andy Saulietis
ISS Enterprises
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