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

Colbert on secret patches :)
by Patrick Wiggins 23 Apr '08

23 Apr '08

Colbert on secret patches: http://www.comedycentral.com/colbertreport/videos.jhtml?videoId=165020 Enjoy, patrick

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Re: [Utah-astronomy] Collimation of a Dobsonian
by erikhansen＠TheBlueZone.net 23 Apr '08

23 Apr '08

>Reaburn, For "rough" collimation you basically want to be able to see entire primary through secondary with secondary "centered" in the focuser. I did receive notice that Don will leading a collimation workshop at the "Gravel Pit". Stars will appear very "fuzzy" and planet images would also suffer, if not collimated well, so I would recommend learning the procedure. I remember an individual seeing "galaxies" everywhere they looked. The Star Test is relatively easy particularly if you have an accomplice. Erik This discussion of collimation has been fascinating! I've owned my 10" > Odyssey Dobsonian for almost 20 years, and I have never collimated it, > unless I did so when I first got it (which I definitely cannot remember). > Indeed, I'm sure I wouldn't know how to begin - even after reading all of > these wonderful posts. > > If my scope is "off," I'm too much of a rank amateur to know the > difference. I use my scope to look at planets, the moon, an occasional > comet, and various Messier objects and easy double stars. Mostly, I use > it to dazzle my family or some school, church or scout group. Since my > limited knowledge is slightly greater than theirs (or my misinformation is > beyond their detection) they think I'm a great astronomer - as often as > not they call me an "astrologer." > > So, I read Chuck Hards' posting: "But if you are mainly observing deep-sky > objects at low to medium powers with wide-field eyepieces, collimation can > be off by a surprising amount with no noticeable effects on the imagery," > and I figure I can probably go another 20 years without worrying about > collimation. > > But then, in that same entry he said: "A fast system (say, f/4) of long > effective focal length (i.e., large aperture), used for imaging at high > power or planetary viewing or very close double star splitting, should be > collimated very precisely," and I wonder if any of that applies to me, and > if I should think about collimation. Unfortunately, I don't even know the > f/ value of my scope. (It's a red tube about 4 ft. long with a 10" > diameter mirror. Does that help?) I do look at planets (especially > Jupiter, Saturn, Venus and Mars), but usually not with my high-power > lense. I haven't noticed any difficulty in getting a crisp image by > fine-tuning the focuser, so I don't know if my views would improve with > collimation or not. > > Any advice from any of you REAL experts to an admitted rank amateur like > me? > > To give you an idea of my lack of sophistication, when I first got my > scope, I couldn't even figure out how to focus it. Patrick Wiggins took > the time to patiently explain how to extend the focussing tube. Duh! > Patrick, you're the greatest! > > Raeburn G. Kennard > 12082 Joey Park Place > Draper, UT 84120 > (801) 321-4867 > rkennard(a)kmclaw.com > > > > > _______________________________________________ > Utah-Astronomy mailing list > Utah-Astronomy(a)mailman.xmission.com > http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy > Visit the Photo Gallery: http://gallery.utahastronomy.com > Visit the Wiki: http://www.utahastronomy.com >

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Re: [Utah-astronomy] Non-Laser Collimation
by Dunn, Dave 23 Apr '08

23 Apr '08

Yes, I use a Chesire sometimes. It is usually used to check on the accuracy of the laser. It is also a great way to check the centering of the secondary. On some telescopes this is hard to do with the laser and grid. The grid is sometimes too small to cover the seondary or with all the lines coming at you while you are checking, you can't see the lines on the secondary. My first collimator was a 35mm film canister with a hole drilled in it. OAS still uses the film canister on BOB. Dave ----- Original Message ----- From: utah-astronomy-bounces(a)mailman.xmission.com <utah-astronomy-bounces(a)mailman.xmission.com> To: Utah Astronomy <utah-astronomy(a)mailman.xmission.com> Sent: Tue Apr 22 18:44:53 2008 Subject: Re: [Utah-astronomy] Non-Laser Collimation > Anyone use the "old fashioned" Chesire Eyepiece Erik > I've set up and collimated my truss tube dobsonian > over 150 times. When you do the same thing many times > you start to find short cuts. Somewhere I began > collimating by just studying the view through the > focuser. It's not as not as simple minded as it > sounds, there is a skill to finding the null point and > there is a major pitfall to avoid. > > First an overview of the picture you see. Start by > racking the focuser out and placing your eye near the > top. This places you close to the focal plain and > shows you the view that the eyepiece sees. > > 1. The first ring in is the bottom of the focuser > tube. (the top is too close to be seen) > 2. The second ring is the secondary. > 3. The third ring in is the edge of the primary > mirror. > 4. The fourth ring way inside of the other three is > the image of the secondary in the primary mirror. > 5. The fifth ring is the image of the top of the > focuser tube reflected twice in the secondary and once > in the primary. > 6. Lastly, floating inside is the image of the > centering ring on the surface of the primary. > > You make the first three rings concentric(1,2,3) in > order to collimate the secondary. But to do this > accurately you need to be sure your eye is centered in > the focuser tube. You can check this by looking at > your eye and centering it in ring number 5. Nulling > the primary mirror requires just bringing the > centering ring (6) over you eye while both are > centered in the image of the focus tube (5). It's not > hard with practice to achieve millimeter accuracy at > this nulling point. > > You notice I didn't try to center 4 inside of 3 or 5 > inside of 4, That's because the Newtonian offset > resides here and it is impossible to get them all > centered due to the geometry of the bent optical path. > I've known people who've tried and failed to get > "everything centered". You don't need to and you > can't even if you tried. > > At some point I heard about the collimation cap that > Orion ships with their Newtonians. I made one and > it's just a two inch white disk with a 2 mm hole in > the center. This device simplifies the nulling > procedure by automatically centering your eye in the > top of the focuser tube. Place the cap in the top of > the focuser and look through the 2mm hole, null the > primary by moving the centering disk(6) over the image > of the 2mm hole. This makes it easier to do in the > dark, just shine a red led light up the focuser tube > so the 2mm hole can be seen against the white disk. > The final trick is learning to center your eye in the > 2mm hole; watching the diffraction effects around the > edge of the hole does this. > > I've used the cap method on a mirror as fast as f/4 > and my results matched that of a nulling laser. I > still use the eyeball only method whenever I can just > because it's so convenient. Both these methods fair > well against the star test which I'll cover in another > post. > > DT > > > ____________________________________________________________________________________ > Be a better friend, newshound, and > know-it-all with Yahoo! Mobile. Try it now. > http://mobile.yahoo.com/;_ylt=Ahu06i62sR8HDtDypao8Wcj9tAcJ > > _______________________________________________ > Utah-Astronomy mailing list > Utah-Astronomy(a)mailman.xmission.com > http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy > Visit the Photo Gallery: http://gallery.utahastronomy.com > Visit the Wiki: http://www.utahastronomy.com > _______________________________________________ Utah-Astronomy mailing list Utah-Astronomy(a)mailman.xmission.com http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy Visit the Photo Gallery: http://gallery.utahastronomy.com Visit the Wiki: http://www.utahastronomy.com

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Off-topic: Disappointing our fathers
by Chuck Hards 23 Apr '08

23 Apr '08

Darth Vader: "Obi Wan never told you what happened to your father." Luke: "He told me enough! He told me you killed him!" Darth Vader: "No! I am your father!" Luke: "No, it's not true! It's impossible." Darth Vader: "Search your feelings; you know it to be true." Luke: "NO!" Darth Vader: "Yes, it is true and you know what else? You know that brass droid of yours?" Luke: "Threepio?" Darth Vader: "Yes, Threepio, I built him when I was seven years old." Luke: "No." Darth Vader: "Seven years old! And what have you done? Look at yourself, no hand, no job, and couldn't even levitate your own ship out of the swamp." Luke: "I destroyed your precious Death Star!" Darth Vader: "When you were 20! When I was 10, I single-handedly destroyed a Trade Federation Droid Control ship!" Luke: "Well, it's not my fault." Darth Vader: "Oh, here we go. 'Poor me, my father never gave me what I wanted for my birthday, boo hoo, my daddy's the Dark Lord of the Sith .. waahhh wahhh!'" Luke: "Shut up." Darth Vader: "You're a slacker! By the time I was your age, I had exterminated the Jedi knights!" Luke: "I used to race my T-16 through Beggar's Canyon!" Darth Vader: "Oh, for the love of the Emperor, 10 years old, winner of the Boonta Eve Open. Only human to ever fly a Pod Racer, right here baby! Luke looks down the shaft. Takes a step toward it. Darth Vader: "I was wrong. You're not my kid. I don't know whose you are, but you sure ain't mine." Luke takes a step off the platform, hesitates, then plunges down the shaft. Darth Vader looks after him. Darth Vader: "And get a haircut!"

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Seeking audio podcasts
by Patrick Wiggins 22 Apr '08

22 Apr '08

I just got one of those new iPod Nanos (audio only) so I could listen to podcasts during my daily workouts. Trolling the web for podcasts I've come across Science Friday and This Week In Science (I prefer the former to the latter) and continue to look for more. Any thought here on where I could find some quality audio podcasts? Many thanks, patrick BTW, I also finally replaced my trusty old G3 PowerBook with one of the new MacBooks. While I've kept most of my old Macs (someday I'll bring my MacPlus to a SLAS meeting <grin>) I'd like to get rid of the old G3. Still works great but only on AC (battery is dead). Thinking I might give it to someone in return for a donation to SPOC. Any takers?

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Re: [Utah-astronomy] Laser collimator
by Canopus56 22 Apr '08

22 Apr '08

Chuck wrote: > Kurt, it seems to me that you can't use the Blug > on a closed-tube Newtonian, since you can't > see it. Am I off the mark here? As others have noted, the blug can be pointed down tube as shown here - http://www.greatredspot.com/1037161-1037161-BlugImage.jpg or the blug can be pointed up tube on a closed Newt, as shown here on my scope - Blug with light cone http://gallery.utahastronomy.com/main.php?g2_itemId=11118 Comparing the preceding image and the following image, illustrates what I mean by a clear unambiguous signal of collimation on a fast Newt - Blug without light cone http://gallery.utahastronomy.com/main.php?g2_itemId=11121 The point of collimation is to get a truncated cone of light centered up focuser. In a fast Newt, it is possible to center the reflection of the primary mirror circle mark on the laser collimator - as nearly shown in the image labeled "Blug without light cone" and as illustrated in Carlin's 2003 article. In the "Blug without light cone" image, collimation is not co-planar between the secondary and the primary. Only the center point of the secondary is collimated with the primary. In the image labeled "Blug with light cone", the light cone coming off the primary is now unambiguously travelling up the focuser tube. The secondary and primary are collimated "holographically" in Nils Olaf Carlin's terms or as I like to call it - they are co-planar collimated instead of co-point collimated. The adjustment differences between the two images is quiet small - again an effect probably limited to a fast Newt. There was no detectable visual difference in the alignment staring down the open focuser tube or by using a Cheshire between the two images. The adjustment difference between the two images was only a two or three of twists on two knobs on the primary mirror. Between the two collimations, there was a detectable difference in image brightness but not in resolution (based on rough planetary tests that I did last season). But another primary benefit - again probably limited to GEM-GOTO mounted fast-Newts - is there is a visually detectable pointing accuracy difference between the two settings. The image labeled "Blug without light cone" actually points several arcminutes to one side of the position of the scope's polar axis. This may be a case of a better tool being more sensitive to alignment errors that really have no corresponding improvement in visually preceived details. In that case, it's extra work without a gain as compared to collimating with a Chesire, cap or with the eyeball down the tube. Whether high-end laser collimation makes any difference on other scopes, like an SCT - which are inherently more optically centered than a Newt - I couldn't say from experience. I don't own an SCT, although Glatter's instructions explain how to align an SCT using his laser collimator. IMHO the main benefit is being able to collimate a fast Newt quickly and accurately without any fuss. It really was worth it - to me - to shell out the $190 in extra gear as compared to the no-cost method of punching a nail hole in a used film canister. But again, that's me and not everyone's cup-o-tea or price point. I've lived both methods and both collimation approaches are equally valid. The whole collimation-alignment routine makes me think it would have been better to go with an SCT as opposed to the Newt that I ended up selecting. - Kurt P.S. - As Don noted, it is natural to be concerned about the blug falling out of the focuser and ruining the mirror. Mine is pretty secure, but I still generally collimate with the tube horizontal to be on the safe side. I don't really worry about the blug falling out. Up thread there was a link to a new design that incorporates the blug target into the laser collimator. No danger of anything falling on to the mirror with that design. ____________________________________________________________________________________ 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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Cloudy Nights to Webcast NEAF 2008
by Canopus56 22 Apr '08

22 Apr '08

With the weather pattern being what it is this year, there may be more time of some indoor astronomy. Cloudy Nights announced that it is going to webcast some of the speaker presentations from NEAF 2008 - the Northeast Astronomy Forum and Telescope Show on April 26-27 (this Friday and Saturday): NEAF homepage http://www.rocklandastronomy.com/neaf.htm CloudyNights announcement - specific webcast times to be announced later http://www.cloudynights.com/item.php?item_id=1782 - 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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Non-Laser Collimation
by daniel turner 22 Apr '08

22 Apr '08

I've set up and collimated my truss tube dobsonian over 150 times. When you do the same thing many times you start to find short cuts. Somewhere I began collimating by just studying the view through the focuser. It's not as not as simple minded as it sounds, there is a skill to finding the null point and there is a major pitfall to avoid. First an overview of the picture you see. Start by racking the focuser out and placing your eye near the top. This places you close to the focal plain and shows you the view that the eyepiece sees. 1. The first ring in is the bottom of the focuser tube. (the top is too close to be seen) 2. The second ring is the secondary. 3. The third ring in is the edge of the primary mirror. 4. The fourth ring way inside of the other three is the image of the secondary in the primary mirror. 5. The fifth ring is the image of the top of the focuser tube reflected twice in the secondary and once in the primary. 6. Lastly, floating inside is the image of the centering ring on the surface of the primary. You make the first three rings concentric(1,2,3) in order to collimate the secondary. But to do this accurately you need to be sure your eye is centered in the focuser tube. You can check this by looking at your eye and centering it in ring number 5. Nulling the primary mirror requires just bringing the centering ring (6) over you eye while both are centered in the image of the focus tube (5). It's not hard with practice to achieve millimeter accuracy at this nulling point. You notice I didn't try to center 4 inside of 3 or 5 inside of 4, That's because the Newtonian offset resides here and it is impossible to get them all centered due to the geometry of the bent optical path. I've known people who've tried and failed to get "everything centered". You don't need to and you can't even if you tried. At some point I heard about the collimation cap that Orion ships with their Newtonians. I made one and it's just a two inch white disk with a 2 mm hole in the center. This device simplifies the nulling procedure by automatically centering your eye in the top of the focuser tube. Place the cap in the top of the focuser and look through the 2mm hole, null the primary by moving the centering disk(6) over the image of the 2mm hole. This makes it easier to do in the dark, just shine a red led light up the focuser tube so the 2mm hole can be seen against the white disk. The final trick is learning to center your eye in the 2mm hole; watching the diffraction effects around the edge of the hole does this. I've used the cap method on a mirror as fast as f/4 and my results matched that of a nulling laser. I still use the eyeball only method whenever I can just because it's so convenient. Both these methods fair well against the star test which I'll cover in 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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Re: [Utah-astronomy] Laser collimator
by Canopus56 22 Apr '08

22 Apr '08

In addition to Glatter's collimator, I also recommend Glatter's blug, if you are collimating a fast Newt. It greatly simplifies the laser collimation process for planar holographic alignment. http://www.greatredspot.com/collimator.htm The 2003 S&T article is good, but dated. Carlin and the collimator makers have moved on from what Carlin wrote there. Although I am tempermentally anti-gear, this is one of few times I recommend shelling out the bucks for the current high-end Glatter collimator and blug, if you own a fast Newt. Spending a couple of hundred on the collimator and blug is justified. It saves endless hours of headaches down the road and improves pointing accuracy for target acquistion. The cheaper laser collimators are not machined well-enough to accurately collimate a fast Newt. Design-wise, Glatter collimator designs also have a larger the battery segregated from the laser. Every time you change the battery on a low-end laser colliminator, the collimator tool itself goes out of the alignment. For Newts, the holographic or planar collimator changes the workflow focus (no pun intended) away from collimation adjustments at the primary mirror towards making most of the adjustments to the secondary with only a final fine-tune tweak on primary mirror knobs. - Kurt P.S. - If anyone knows an upgrade for a secondary mirror holder, please let me know. I'd like to get away from Allen wrenches and screwdrivers towards a secondary mirror holder that is rock solid and adjusts with some kind of locking knobs. There was an interesting advanced secondary mirror holder design in the April or May S&T. Blug review (not favorable) http://www.cloudynights.com/item.php?item_id=1480 ____________________________________________________________________________________ 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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Orem school star party has been canceled.
by Richard Tenney 22 Apr '08

22 Apr '08

All, I was just informed by the principal that the star party planned for Friday has been canceled (too many other conflicts). Thanks to those who have offered help anyway! Clear skies, /Rich --- marina P <mandaloolu(a)hotmail.com> wrote: > > I want to come and I can help. What time is it at?> > From: slworthington(a)msn.com> To: > uvaa(a)mailman.xmission.com> Date: Mon, 21 Apr 2008 > 16:20:19 +0100> Subject: Re: [UVAA] Need help next > Friday (April 25) with elementary school star party > in Orem> > > I can help on Friday. I will bring my > Meade LX90.> > --Scott> Date: Fri, 18 Apr 2008 > 15:58:23 -0700> From: retenney(a)yahoo.com> To: > uvaa(a)mailman.xmission.com; > utah-astronomy(a)mailman.xmission.com> Subject: [UVAA] > Need help next Friday (April 25) with elementary > school star party in Orem> > 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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