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Schmidt-Cassegrain telescope as collimator?

ekeup

ekeup

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Will a Schmidt-Cassegrain (EDIT: incorrect, this is a refractor) telescope work 'well' as a collimator?
Should I remove the lens from the laser itself prior to installing in the telescope?

Schmidt-Cassegrain (EDIT: incorrect, this is a refractor telescope):
800px-Schmidt-Cassegrain-Telescope.svg.png


$20 telescope (from garage sale):
etx70at.jpg


I have a better telescope (also SCT), but don't really want to risk damaging it.
 
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steve001

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I6 people plus me have not replied with an answer. Maybe we don't know. I don't. How about this ? Experiment and you tell us the results.
 
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ekeup

ekeup

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steve001 said:
I6 people plus me have not replied with an answer. How about this ? Experiment and you tell us the results.
Click to expand...

Haven't built the laser yet, just doing research, also worried a bit about the beam reflecting off the secondary mirror back into the laser.
 
Bionic-Badger

Bionic-Badger

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No, I don't think so. That telescope is designed to collect a lot of light from a wide area and concentrate it in the center. Also the incoming rays of light are already parallel to the entrance, and then get focused down. Maybe you could use it as an expander, but I don't think it would serve you well to use that variety of telescope for such a small-scale system that is usually associated with hobby lasers.
 
ekeup

ekeup

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Well, I know telescopes do work as collimators...


I'm just trying to determine if an SCT would work, or would the reflection off the secondary be an issue.
 
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steve001

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Bionic-Badger said:
No, I don't think so. That telescope is designed to collect a lot of light from a wide area and concentrate it in the center. Also the incoming rays of light are already parallel to the entrance, and then get focused down. Maybe you could use it as an expander, but I don't think it would serve you well to use that variety of telescope for such a small-scale system that is usually associated with hobby lasers.
Click to expand...

If this would work as a beam expander. That's what they're asking
 
Cyparagon

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It should work as a beam expander provided you select the right objective at the eyepiece. The expanded beam will have a hole in the middle though.
 
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steve001

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ekeup said:
Haven't built the laser yet, just doing research, also worried a bit about the beam reflecting off the secondary mirror back into the laser.
Click to expand...

Here's what I know and suspect. Mirrors can be used as beam expanders. I think you'll need to include the eyepiece in your experimentation.
 
Benm

Benm

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There is no reason you cannot use this telescope as a beam expander indeed. One condition would be that your laser beam is narrower than the exit pupil of the telescope, otherwise a lot of laser power would never reach the exit aperture. I'm not sure about this particular model, but since telescopes are mostly built for work at night and laser output beams are often about 5mm diameter, this should be okay.

And as far as the lenses on the laser are concerned: keep them. You need the entire laser pointer to output a beam with as low a divergence as possible - so focus it to infinity if its and adjustable model, or don't mess with it if its not.
 
Ghostchrome

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The blue telescope that you posted is a small refractor. It should work good as a beam expander. I've actually have the same one, but never tried it.
 
ekeup

ekeup

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Ghostchrome said:
The blue telescope that you posted is a small refractor. It should work good as a beam expander. I've actually have the same one, but never tried it.
Click to expand...

I thought all ETX's were SCT design, I don't have it at my current location, and have never really used it, but at $20... I had to buy it :drool:

EDIT: my 'better' telescope is the ETX-125, which I plan on testing with my 5mw cheapo green laser... before I attempt to push 1.5-2watts of 445nm laser (jayrob maglite build) through the ETX-70 first... then MAYBE the ETX-125.
 
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scopeguy20

scopeguy20

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Most any telescope will, when you point the laser in at the eyepiece, (with it's focus on the stars), project a beam that will show at what point in the night sky the 'scope is pointed... I've tried several ;) -Glenn
 
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