Hey Michael: Do you have lock-knobs on the collimation bolts? Is the primary rattling around in it's cell? I know a "loose" fit is recommended, but there are ways to restrain a mirror without introducing mechanical stress, not in the literature. None of my solid-tube Newtonains need collimation every time they are used. Unless I disassemble them, only a tweak about twice a year is typically required- even after hauling them repeatedly over those darned Utah back roads. Of course, these tubes are either aluminum or fiberglass, not cardboard. My old 10" cardboard Dob with commercial cell did require frequent collimation. And I use a padded transportation cradle for the OTA now. "Something special up my sleeve" is my trademark... ;o) --- Michael Carnes <MichaelCarnes@earthlink.net> wrote:
Hey Chuck, For whatever it's worth, my 10" F/4.5 sonotube dob needs collimation every time I go out (probably has something to do with gravel roads and long drives). I'm sure that your mechanical work on your new scope will be considerably better than my Frankenscope, but unless you've got something special up your sleeve I'll bet you've still got to turn those knobs. Wonder if you could do something with DC motors and worm gears. Then you could stay at the eyepiece.
MC
On Jul 24, 2006, at 10:49 AM, Chuck Hards wrote:
Yes, actually. The first time I used it on my f/5.6 Newtonian was with Rich Tenney at the Lakeside site some years ago.
Even this method is not accurate enough for precision collimation with very fast optical systems. At f/4.5, collimation must be within a fraction of a milimeter. Even projecting a grid leaves too much room for subjective (or perceptive, really) interpretation. Repeating the procedure could probably average-out any residual errors. But even if it worked without a star-test tweak the first time, it still takes time that I don't want to spend at every set-up.
It occured to me that one could possibly use a video feed at the eyepiece, and watch a screen while tweaking the collimation screws- if the camera were sensitive enough to detect the diffraction rings, which isn't likely.
But here again, I don't want to HAVE to adjust collimation every time I set-up. I'll check it each time, but only want to adjust it if necessary. Assembling a telescope every time means at least a minor adjustment for precision collimation with a large reflector. At this point, there is probably no way to convince me of a necessity for a truss-tube design at this aperture.
Thanks, Kurt.
--- Canopus56 <canopus56@yahoo.com> wrote:
Are you familiar with holographic laser collimation?
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