Long focal lens: can a newton telescope be used as an optic for a thermal imager?
A newton telescope is a very simple reflective telescope, with a parabolic (spherical sometimes)
primary mirror and a flat secondary that bends light laterally. Mirrors are shaped in glass,
and covered by a thin reflective aluminium surface. Sometimes this surface is covered by
another protective and optically transparent layer, but overall it should reflect long wavelenght
IR pretty well.
This is my hand as seen trough the telescope by the E4:
But to use the scope as a lens, I should remove the lens on the E4, is it possible to remove the
lens just unscrewing it? I didnt try yet because I'm afraid to expose the sensor to dust.
An alternative to direct sensor projection, is the "ocular projection" method, it is needed an
"ocular", that is a lens of focal lenght way shorter than telescope, in this case the camera can
be used with it's own lens mounted, just like a small photocamera put near the ocular.
The big difference is that the "ocular" must be an IR lens. I hope I can make more tests on this.
If it works, it will be relativlely easy to build a tele lens for cheap.
More to come...Update:
I made a quick and dirty test with an ebay 50mmFL lens as "ocular" for my telescope (1m FL),
just to see if I can obtain a sort of image, total magnification will be around 20x (1000mm/50mm).
images are messy, there is a street going from low right corner of the image, to top left,
and cars passing, one in the first image and two in the second.
The camera was hand held, and the 50mm lens was about distance 50mm from E4 lens front.
Cars were about 600mt away.
The field seem to be be about 2°30', about what I was expecting.
Removing E4 lens should give much cleaner images
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