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| Catseye video clip for XLK http://webstertelescopes.com/forum/viewtopic.php?f=7&t=590 |
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| Author: | jonW [ Wed Mar 16, 2011 4:58 am ] |
| Post subject: | Catseye video clip for XLK |
Just found this video demonstrating how to use the XLK autocollimator with hotspot: http://www.catseyecollimation.com/cegallry.html#xlkvideo There are two alternative approaches to using the XLK as explained in the video. 1) CDP method: also detailed here: http://www.catseyecollimation.com/XLK-HotSpot-R1.pdf You intentionally decollimate the primary mirror to make the relevant hotspot reflections easier to see. Then collimate the secondary with XLK using central pupil, followed by setting the primary with Cheshire. This method is not re-iterative. Do this once and you're set. 2) re-iterative method Also detailed here: http://www.cloudynights.com/ubbthreads/showflat.php/Cat/0/Number/3532750/page/0/view/collapsed/sb/7/o/all/fpart/10/vc/1#3635872 (look at the 4th post on this web page, written by the inventor of the hotspot) This method uses a different set of hotspot reflections which are easier to visualise than those in method 1). Set the secondary using XLK in off-set pupil. Then set the primary with cheshire. The downside of this method is, although the relevant reflections are easier to see, it requires multiple iterations to achieve perfect collimation. What I would like to know, is what do people recommend as to the better method with a Webster telescope ?? Personally I have always used the one where you dont intentially decollimate the primary, but I cant say I've been 100% successfull to date. I also find the laser and barlowed laser methods less hassle. Also how do people illuminate the hotspot ?? I notice Catseye now sell a narrow beam red LED flashlight. Would you attach this to one of the trusses near the mirror box ?? |
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| Author: | Eric [ Thu Mar 17, 2011 3:55 pm ] |
| Post subject: | Re: Catseye video clip for XLK |
That is a great video. As far as what method is "better" on our scopes, either one will work just fine. Your choice would probably depend on if you had assistance, how large your scope was, and how familiar you are collimating telescopes. If you set your scope 1/2 way through it's motions (45 degrees in ALT) and that means you need a ladder to look into the autocollimator, then using the fine adjustments on the secondary would be easier. That way you are making your adjustments while looking, rather than going back and forth and checking your work. I have to admit that I cheat and first collimate with the Glatter BLUG, then double check with the Catseye. 95% of the time it is perfect and requires no further attention. The best advice I can give is to practice on a rainy day. No rush before sunset, no one distracting you with questions about your scope, just relax and experiment. Get it collimated, then mess it up and do it again. 5-10 times and you will be a master. While looking through the autocollimator, press (rather than turn) the 4 knobs on the secondary and watch how the center spots stack and unstack. The main thing is to relax and practice. Once you have the hang of collimation, it will take you less than one minute to complete. Anyone who comes out to our shops always gets a collimation run through. It is 100x easier when someone just shows you how to do it, rather than reading 20 pages of theory. |
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