April 2008 - Utah-Astronomy - mailman.xmission.com

Re: [Utah-astronomy] Laser collimator
by Canopus56 21 Apr '08

21 Apr '08

Chuck wrote: > Kurt, Bryan Greer (Protostar) may have the > secondary holder you are looking for. > http://www.fpi-protostar.com/ That looks like a good upgrade for a secondary. I'm really focused (there's that pun again) on trying to find a spring loaded knob that I can adapt instead of having three spring loaded Allen bolts in the secondary mirror. I'm finding that when hauling around the Newt, it's the secondary mirror that is getting jolted out of alignment by the potholes, not the primary mirror. Rather than having to futz with Allen wrenches during a twilight setup, I'd really like to end up with somekind of quickly adjustable knob. I haven't been able to find any small knob with a bolt long enough to reach through the secondary mirror holder body and reach the pyrex assembly. > I must add that when I use a laser for > collimation, I still base my final, critical > adjustments (if needed) with a star-test- > now there's a dirty word for you. I've been > recommending Dick Suiter's book for years > (Star-testing Astronomical Telescopes) > and still do. Suiter's book is an all-time classic - definitely worth anyone having on their bookshelf. You gotta know how to star test, if only for the entertainment value of seeing spooky quantum mechanics nanometer-sized diffraction rings in your eyepiece. -:) But going back to the setup time thing - the high-end laser collimator will get you there faster, you can get nearly perfect collimation on the couch at home in a comfortable lighted environment before leaving for the field and only have to tweak the final adjustment when the scope is field mounted. For me, it's a time and enjoyment thing. Minimize the time getting the scope really aligned and collimated and spend more time at the eyepiece. - Kurt ____________________________________________________________________________________ Be a better friend, newshound, and know-it-all with Yahoo! Mobile. Try it now. http://mobile.yahoo.com/;_ylt=Ahu06i62sR8HDtDypao8Wcj9tAcJ

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Re: [Utah-astronomy] Laser collimator
by Canopus56 21 Apr '08

21 Apr '08

I wrote: > For me, it's a time and enjoyment thing. Minimize > the time getting the scope really aligned and > collimated and spend more time at the eyepiece. P.S. - Which is why this thread probably ought to be under "Re: [Utah-astronomy] Pondering permanent piers" or "Why I gave up nightly collimating altogether and just mounted the darn thing once." - Kurt ____________________________________________________________________________________ Be a better friend, newshound, and know-it-all with Yahoo! Mobile. Try it now. http://mobile.yahoo.com/;_ylt=Ahu06i62sR8HDtDypao8Wcj9tAcJ

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Re: [Utah-astronomy] Laser collimator
by Canopus56 21 Apr '08

21 Apr '08

Dan wrote in another thread: > Chuck Hards brought up one in that lasers > themselves need to be in collimation to be > of value. A common reply to this problem is > to "buy a really expensive one" and that > will solve the problem. A better approach is > to set the laser in a pair of v blocks on > a sturdy table, aim it at a wall that's the > focal length of your telescope away from the > laser, roll the laser around in the v > blocks and measure the radius of the circle > the dot traces on the wall, if it's more > than millimeter the laser is defective. Absolutely. The low-end collimators that I bought and have see, like this $60 Zhumell model were worthless even with bench alignment. http://www.opticsplanet.net/zhumell-laser-collimator.html The tool would not hold an alignment. Even by the time you do get the laser aligned, the battery runs down. Then you have to pull the laser to replace the battery - which means unscrewing the three laser alignment screws. So, you are back to square one. Or worse, the battery runs down such that it looks okay on the bench, but when you get to the field, it dims while you are collimating the scope. Then when you put the collimator into a 1 1/4" adapter, it isn't machined to the right diameter. The result is for a low-end collimator - and here's the acid test - as you rotate the aligned laser collimator in the focuser adapter through 360 degrees - the laser dot does not trace a 50mm circle on your primary mirror. With the Glatter style lasers - which are admittedly are much more expensive - come well machined and with rubber corking to center the collimator in the focuser adapter. The result is that the collimator consistently traces a 0-1mm oval in the center of the primary. (The balance of the movement error is in my mid-range Moonlight focuser and 1 1/4" focuser adapter.) The battery pulls out the back without effecting collimator alignment. My recommendation for not trying to save by going with the low-end collimator is simply time. With a high-end collimator on a fast-Newt, I can consistently maintain and set right-on collimation in under five minutes. No mess, no fuss, no questions. Based on my experience, going with the low end collimator to lower expense is just not worth the time lost to futzing with a poor tool. > The subject tends to generate a lot of heat and > smoke with very little illumination when it > comes up on Internet discussion groups. Definitely want to avoid that here. - Kurt ____________________________________________________________________________________ Be a better friend, newshound, and know-it-all with Yahoo! Mobile. Try it now. http://mobile.yahoo.com/;_ylt=Ahu06i62sR8HDtDypao8Wcj9tAcJ

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laser collimation of newtonians
by daniel turner 21 Apr '08

21 Apr '08

Laser Collimation of Newtonians The subject tends to generate a lot of heat and smoke with very little illumination when it comes up on Internet discussion groups. This is because people start with different basic assumptions and then tend to talk past each other in what appears to be total disagreement. A few years ago a long running thread on the BIGDOB discussion group displayed an amazing array of debating tactics. The final "winner" would appear to be the one who posted the last message in the thread. Of course with two or more participants with plenty of time on their hands, the debate could go on forever. All this debate accomplished was to scare amateur astronomers into buying expensive refractors that lack collimation screws alltogether. Added to this is the emergence of people with a commercial interest in the debate. Howe Glatter is gentleman who lets his product reputation speak for itself, but other vendors lurk on discussion groups and flame anyone who offers an adverse opinion of their product. This is not exactly First Amendment behavior. Don Colton's lecture was good up to a point, but he had a lot of ground to cover in a short time and so he had to limit debate and gloss over some points. Chuck Hards brought up one in that lasers themselves need to be in collimation to be of value. A common reply to this problem is to "buy a really expensive one" and that will solve the problem. A better approach is to set the laser in a pair of v blocks on a sturdy table, aim it at a wall that's the focal length of your telescope away from the laser, roll the laser around in the v blocks and measure the radius of the circle the dot traces on the wall, if it's more than millimeter the laser is defective. If you bought it that way you should return it. My own collimation method comes from having used Newtonians before the center spot or the laser were invented. I'll save that for another post. DT ____________________________________________________________________________________ Be a better friend, newshound, and know-it-all with Yahoo! Mobile. Try it now. http://mobile.yahoo.com/;_ylt=Ahu06i62sR8HDtDypao8Wcj9tAcJ

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Laser collimator
by Chuck Hards 21 Apr '08

21 Apr '08

Can anyone remember the Sky & Telescope issue that contained Nils Olof Carlin's article on using a Barlow lens with a laser collimator? I have been unsuccessful searching on the S&T Website. Don Colton, you explored this further, IIRC, yes? If someone can cite the issue, I will look it up in my own library. TIA!

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Pondering permanent piers
by Patrick Wiggins 20 Apr '08

20 Apr '08

Joe asked me for tips for purchasing a pier on which to mount his scope in his yard. My thoughts follow but I'm sure the ATMs here will have even better ideas so I'll ask questions for the ATMs along with my thoughts. +++++ I'm pretty sure piers are available commercially but I've always favored home built models. I guess one extreme would be "Patrick's Pompous Pier Project", pictures of which can be seen in image numbers 108 to 138 at: http://users.wirelessbeehive.com/~paw/PATRICKW03.HTML Obviously "normal" people don't need to go to that extreme. :) For most applications a concrete filled steel pipe cemented into the ground ought to work. I like steel for smaller piers, BTW, because it's easy to weld a flat steel plate to the top and onto which a wedge can be bolted. What diameter and wall thickness for the pipe? I like a thick wall. The steel part of my current pier is 1/2" thick. Diameter? Better too big than too small. Perhaps about the width of the base of the wedge? How deep to bury the pier into the ground? Better too deep than too shallow. FWIW, my first pier (for a C-8 in a ground level observatory) stood one meter above ground but went 1.5 meter into the ground. Fill the pipe? And, if so, with what? Some leave it empty. I used concrete in my first and current piers and sand in my second pier (which was made from 3 oil drums welded end-to-end). Ok, those are my thoughts. Now let's hear from the ATMs. Cheers, patrick

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Need help next Friday (April 25) with elementary school star party in Orem
by Richard Tenney 18 Apr '08

18 Apr '08

First off, I want to apologize to any who came to help with the girl scout star party last week and found the gate locked! I had no idea the leaders there would do that! Anyway, it was a success (thanks to those that beat the gate closing and/or waited for someone to come unlock it). I have another star party coming up next Friday the 25th at Orchard Elementary school in Orem, 1035 N. 800 E. Any that can help out with this please RSVP. Thanks again for your help! Call me if you have questions (I probably don't have the answers yet!) 801~380~3331 /Rich ____________________________________________________________________________________ Be a better friend, newshound, and know-it-all with Yahoo! Mobile. Try it now. http://mobile.yahoo.com/;_ylt=Ahu06i62sR8HDtDypao8Wcj9tAcJ

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See what happens after Joe retired :)
by Patrick Wiggins 18 Apr '08

18 Apr '08

Boy, ace science writer Joe hasn't even been retired a week and already international science related journalism is falling apart. Never would have happened if Joe was still on the job. So, Joe, do you feel guilty enough to go back to work? NASA Statement on Student Asteroid Calculations: http://www.nasa.gov/home/hqnews/2008/apr/ HQ_08103_student_asteroid_calculations.html And some background: http://cosmos4u.blogspot.com/2008/04/apophis-risk-not-increased- science-fair.html The folks on the minor planet mailing list are having a lot of fun with this. Grins, patrick

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Natural Satellites Ephemeride Server
by Patrick Wiggins 17 Apr '08

17 Apr '08

Handy service for those who will want to watch 2009's mutual events of the satellites of Jupiter (especially if you own a Clark refractor...) http://www.sai.msu.ru/neb/nss/nsszph5he.htm Those using the service in N. Utah who would like data returned for their area may enter observatory code "718". patrick

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Re: [Utah-astronomy] SLAS Presentations at Tuesday meeting
by Canopus56 17 Apr '08

17 Apr '08

Joe, I believe Eric is talking about Patrick's Solar System Ambassador news. These would go directly to your email from Patrick and have a title in the form: "News dd MMM yyyy". - Kurt ____________________________________________________________________________________ Be a better friend, newshound, and know-it-all with Yahoo! Mobile. Try it now. http://mobile.yahoo.com/;_ylt=Ahu06i62sR8HDtDypao8Wcj9tAcJ

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