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Total 4 reviews
3.8 out of 5 stars
Losmandy Polar Alignment Scope
I find this accessory to work as advertised. I do deep sky imaging with a 900mm 6 scope and the polar alignment I get with this product in about 3 minutes is all I need. Although you can use 3 stars for alignment in the reticle, I just align polaris and the 2nd, star and get good results. It does require some adjustment to get the best results, but out of the box it was pretty close.
There are only two advantages to this accessory but they are very significant. One, it threads directly into the Losmandy mount. Two, the star patterns on the reticle allow the user to roughly align the polar scope by observing the position of Cassiopeia and the Big Dipper. This is a plus over the Celestron clock system that I used to use because I always got confused as to which side of the clock Polaris was supposed to be. The fine alignment is done with the alignment using secondary stars very near Polaris which, unfortunately, are sufficiently dim to be wiped out by pollution in my usual viewing area (more on this below).
There are two improvements that could be made. One that is imperative is that there be a means to attenuate the brightness of the illuminator. Where the north sky is heavily light polluted, as in any place immediately south of a major metropolitan area, the illuminator brilliance does not allow the eye to adjust and view dim stars used for final alignment of the reticle. I recommend that the maker investigate the circuit that Telrad uses for attenuation and blinking.
Another improvement would be a diagonal. An accomplished Yoga would have no problem with the contortions necessary for sighting especially when the height of the assembly is minimized for rigidity. However, old guys with pinched nerves really find it a pain in the neck, so to speak, to crawl under the tripod and squeeze the dickens out of their already herniated C5-C6 cervical disk.
Faster than a speeding Drift-Align
This accessory, which incorporates a nicely etched reticle, can get one reasonably close to polar alignment in a few minutes, with practice.
It must be calibrated first by rotating it against a fixed object (or bright star like Polaris) in order to check the reticles centering. It is a bit fussy to work with, as the 3 stars that you align with in the reticle are hard to place correctly due to the wandering (precession) that occurs. Theres a 10 year gaps in the etched lines that you place these stars in, so one has to do a little guesswork. Scale is not quite large enough to permit pinpoint accuracy.
The construction is adequate. The fit can be sloppy in the polar barrel of the mount, and is subject to wandering. Can be overcome by shimming w/brass or teflon tape. Tightening down on mount barrel is hard to get just right.
Polar Alignment is far better with it than without it, and there are no higher quality polar scopes to be found anywhere at any price. Good enough setup to autoguide on with reasonable care.
Polar Scope good. Illuminator bad!
The good news is that the Losmandy Polar Scope works reasonably well for aligning the mount for visual use. For astrophotography you should still consider drift-aligning, or if available, using your mounts polar alignment utilities. The bad news is the whole arrangement around the reticle illuminator. The issues are the LED device that screws into the polar scope, and the complete lack of a dimmer. The threaded hole to accept the illuminator LED is smaller than what you would normally find on a guiding eyepiece or illuminated finder scope, and the thin wires from the LED to the power pack do not seem to bode well for the illuminators longevity. (Although the LED and wires do seem to be able to stay in a stationary relative position, as one screws the illuminator into the polar scope.) The brightness of the illuminated reticle makes it difficult to see the second and third alignment stars. It would be preferable to see something like the ubiquitous Celestron variable brightness, button-cell illuminator (http://www.buytelescopes.com/product.asp?t=&pid=560&m=) but with a head that can rotate 90-degrees, so it can be left in the polar scope. (The polar scope rotates with the RA axis as the mount moves, so something like the Celestron illuminator might hit the mount - depending on your observing latitude.) One other note: I have a newer GM-8 mount and have not experienced any of the binding problems that you may have heard of in the past.