January 2009 - Utah-Astronomy - mailman.xmission.com

Re: [Utah-astronomy] Stellar color perceptions
by zaurak＠digis.net 13 Jan '09

13 Jan '09

Lets also not forget the color correction of various lenses. With my f5, I am hesitant to describe lilac or bluish tint, filters help but there is a big difference compared to apcohromatic refractors. I know what you will say, get a reflector or cassegrain. Seeing airy disks is very pleasurable and makes the acohromat very worhtwhile Brightness also is factor, ie the brighter the object the more purple halo you have. An apodizing mask is also helpful. I think Kirk is correct that society in general has gotten color illiterate. I have found some pretty profound differences in the way Webb, Smyth, and Haas describe the colors this indicates to me that perception does vary among very experienced observers. I do find myself agreeing with Smyth and Webb more than Haas. Perhaps as Chuck said the difference between male and female. Erik --- kimharch(a)cut.net wrote: From: "Kim" <kimharch(a)cut.net> To: "'Utah Astronomy'" <utah-astronomy(a)mailman.xmission.com> Subject: [Utah-astronomy] Stellar color perceptions Date: Thu, 1 Jan 2009 23:02:00 -0700 Chuck et. al.: >From my first days of serious telescopic observing I've been interested in stellar colors and the descriptions of them given by early observers, such as those cited previously. (My favorite description is "pale lilac" but I don't recall the observer who coined that color for a binary companion star.) Color theory, as you know, is very different for direct light sources than for reflected (pigmented) color sources. Theatrical lighting, for example, requires a different skill and color understanding than the traditional skills taught in art (and in my case, architecture) schools. I learned a lot about color descriptions from stamp collecting, and I'm still looking for a star colored "carmine" or "vermillion". I think, though, that I've seen "periwinkle" and "indigo". I've concluded that color descriptions by others are very subjective and unreliable. The main thing is to trust your own observations - and enjoy. Interesting thread. Thanks. Kim -----Original Message----- From: utah-astronomy-bounces(a)mailman.xmission.com [mailto:utah-astronomy-bounces@mailman.xmission.com] On Behalf Of Chuck Hards Sent: Thursday, January 01, 2009 8:15 PM To: Utah Astronomy Subject: Re: [Utah-astronomy] A snack in Gemini before bedtime I don't think the "color illiteracy" theory holds in my case, at least. I trained as an artist for years in school and made my living at it for a few years. My descriptive color pallate is easily up to the task. As I alluded, I'm pretty sure the differences I see personally are due to biology. At my place of employment, color is very important to our customers. They specify certain colors as key to their branding and use calibrated Pantone numbers to help their vendors get it right. Even then, some of us see their supplied samples as a match to different shades in the Pantone book- not always the specific color they say it is. Color perception as a function of biology is clearly at work here- and even when one discounts the obvious, textbook examples of "colorblindness". I also think that some of the differences may be due to those 19th-century observers using refractors that were optimized for different wavelengths than modern refractors. Too, in my observing heyday I used reflectors exclusively. There is also the possibility that atmospheric composition (from man-made pollutants) is absorbing certain wavelengths in a subtle way that is different from 100+ years ago. Tough call. Color, tint... it's such a fleetingly subtle thing with astronomical targets, to begin with. No virus found in this outgoing message. Checked by AVG. Version: 7.5.552 / Virus Database: 270.10.1/1870 - Release Date: 12/31/2008 8:44 AM _______________________________________________ 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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Satellite to decay over Utah tonight?
by Patrick Wiggins 13 Jan '09

13 Jan '09

I received this from CalSky. Satellites which could de-orbit close to your site. Tuesday 13 January 2009 Rise(invis.) 23h35m35s az:212.5° SSW Culmination 23h38m44s az:301.8° WNW h:79.3° distance: 162.2km, height above Earth: 160.7km Set (invis.) 23h41m56s az: 31.2° NNE

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Re: [Utah-astronomy] Comet Lulin seen with Binos
by Jay Eads 11 Jan '09

11 Jan '09

Some other links: A map of where the comet is through 3/7 http://www.aerith.net/comet/catalog/2007N3/2007N3.html NASA's page on the comet: http://ssd.jpl.nasa.gov/sbdb.cgi?orb=1;sstr=2007+N3 Next time I get out after this week I'll have to take a look for it. On 2009-01-10 18:56, Jim Gibson wrote: > > Hi all, > Coming up next month we should get a look at comet C/2007 N3 (Lulin) peaking at 4th mag on 24 Feb. > > See: http://cometography.com/lcomets/2007n3.html for details and history. > > jg > > > >

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Re: [Utah-astronomy] Tri-color samples
by Wayne Sumner 09 Jan '09

09 Jan '09

I'd like a kit, please. Thanks, Wayne A. Sumner Math/Physics/Astronomy/Engineering Boy's Tennis Coach Northridge High School Davis School District (801) 402-8610 >>> Patrick Wiggins <paw(a)wirelessbeehive.com> 01/08/09 6:29 PM >>> I spent some time collimating my scope last night after which I took a few test shots of M-1 which just happened to be transiting. Knowing there are some folks here on the list getting into astroimaging I made images for a "kit" that could help folks get a feel for what's involved in making color images. The kit contains: 1-Raw exposure with clear filter 1-Raw exposure with green filter 1-Raw exposure with blue filter 1-Raw exposure with red filter 1-Master dark to be used to reduce all of the raw images 1-Master clear flat for reducing the raw clear 1-Master green flat for reducing the raw green 1-Master blue flat for reducing the raw blue 1-Master red flat for reducing the raw red The master dark was made by shooting and median combining 15 darks. The master flats were made by shooting and median combining 15 each flats shot through the clear, green, blue and red filters. I should note that using the kit will not get you "Tyler like" images. Though the final image should look pretty good the main purpose of the kit is to show folks what's involved in making "real" color images (I say "real" as opposed to the one-shot cameras which, like color film, sometimes produce questionable colors). Let me know if you'd like a kit and I'll email it out. Clear skies! patrick _______________________________________________ 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] Moon Crater Schiller
by zaurak＠digis.net 08 Jan '09

08 Jan '09

One of the few advantages of cold weather observing, a short cool down period for your optics. --- jimgibson00(a)yahoo.com wrote: From: Jim Gibson <jimgibson00(a)yahoo.com> To: Utah Astronomy <utah-astronomy(a)mailman.xmission.com> Subject: [Utah-astronomy] Moon Crater Schiller Date: Wed, 7 Jan 2009 16:47:31 -0800 (PST) I was just checking out the moon while my optics cooled. Thought I might check out a few doubles tonight which is about all I can do with the moon the way it is. I was cursing the Southern Highlands when I notices this long looking crater south of Tycho a ways. I thought it was actually round but only looked oval because of it’s location. Turns out that it is the crater Schiller; 71 km wide and 179 km long. Interesting since over 90% of the creators are more round than oval. I am guessing that the impact that created Schiller must have been quite oblique. No spray visible though like there is on Tycho. Well, gotta go. My doubles are waiting. jg _______________________________________________ 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] 13.1 inch Coulter Carcass, free
by zaurak＠digis.net 08 Jan '09

08 Jan '09

Chuck, Well, at least some of best magnifications have a 4-5 mm exit pupil. In the big picture a shrinking exit pupil is not the worse thing about getting old. I would agree that in smaller apatures f5 or f6 is better, mainly to avoid crouching too much at the eyepiece, to reduce effects to the aging process that causes. Age and infirmity also seem to reduce the size of telescopes, the professionally figured f4, I observed with was well done and had minimal coma with Naglers. I would say if you plan to use a coma corrector place your focuser with that in mind when you build your dobson. I have been less affected by shrinking exit pupil, one of the few bright spots in my aging process. I am due to see the ophthalmologists though, it has been about 5 years since my last visit. I am more like 6 mm, my 7x42 binocs still work well for me, as for my refractor, at widest fields I do have to move my eye around to see full view. I will have bring my exit pupil gauge to a few star parties. I remember passing it around at the Sun Tunnels one evening, a few years ago, and a lot of people were around the 5 mm range. BTW, I would not want to forget Jerry Footes' ATM escapades, although he is closer to the professional side now. I also think, it is telling that Riverside is now called the "Astronomy Expo" and not the "Telescope Makers Conference". Erik --- chuck.hards(a)gmail.com wrote: From: "Chuck Hards" <chuck.hards(a)gmail.com> To: "Utah Astronomy" <utah-astronomy(a)mailman.xmission.com> Subject: Re: [Utah-astronomy] 13.1 inch Coulter Carcass, free Date: Thu, 8 Jan 2009 11:05:29 -0700 Erik, I understand what you are saying completely. The disadvantage of getting old is a shrinking exit pupil. Mine never gets larger than about 5.5mm anymore, even in absolute darkness. I have trouble with wide-field eypieces; the "kidney bean" effect sometimes blacks-out large portions of the field of view. 80 degrees is about the max I can use comfortably, and only if the eye-relief is decent. The exit angle of the light cone can't be too steep or the eyepiece is just a paperweight to me. There is no substitute for youth! There comes a point in life where age or infirmity requires certain trade-offs at the eyepiece. Those trade-offs are what allow us to continue to use a telescope, in may instances. I'm building a 17.5" f/4.5 because of the exact reasons listed. I won't need a ladder to reach the eyepiece when pointed at the zenith. My balance is terrible in the dark, and I don't want to haul a ladder around with me. When I was 18, I wouldn't think twice about scrambling up a tall ladder in the dark. Now, no way! But at the same time, I'm not going to stand on a soapbox and say that my f/4.5 yields imagery as good as an f/8 just to feel better about my choice...and I've seen the mirror on the test-stand. It has an excellent figure. F/4.5 is a compromise. If I had my 'druthers, it would have been f/5.5. But...no ladders- I'm not 7 feet tall, and I own a coma corrector optimized for that exact mirror. I'm not condemning fast mirrors, they have their place. The discussion started with the idea of a beginner grinding their own first mirror. An f/4 is a tough hurdle right out of the gate, and a beginner isn't likely to start with a 16" or larger. And a long-focus mirror will ALWAYS give a higher quality image given the same eyepiece. A 16" f/4 with a decent figure will give good planetary views because of the resolving power of a 16" mirror. Aperture will win over a large coma-free field. That planetary disk is occupying the sweet spot of the focal plane, most of the time. But a long-focus 16" would definitely give a better planetary image, especially if the planet gets away from the center of the field. And, you can use longer-focal-length eyepieces to achieve the same magnification (read: easier to use). Yes, some beginners have tackled large, fast mirrors as a first effort- some right here on this list- but it's not typical, and they had excellent instruction along the way. So, I restate: To each, his or her own. My reasons are probably not the same as others. On Thu, Jan 8, 2009 at 10:11 AM, <zaurak(a)digis.net> wrote: > The main advantage of f4 over f5 would be bigger exit pupil for same > eyepiece. > > _______________________________________________ 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] 13.1 inch Coulter Carcass, free
by zaurak＠digis.net 08 Jan '09

08 Jan '09

Hi Chuck The ladder at SPOC for the Ealing is good choice and takes up half the bay. I doubt there are to many portable ladders that are, Brent Watson had a tall ladder I think we where fortunate that there was no accidents. I remember his encouragement for people to look at bright objects with both eyes atop the ladder. Many struggled getting down ladder afterward. Yes, Chuck I am sure that your F5 gives good views, when you get into larger scopes, 16" and above, the eyepiece starts to get high of the ground. Bob pointed out how his 16 f 4.5 could be used without ladder. You do have get more expensive eyepieces and coma is present at edges and most objects do not require wide field. My f5 refractor also works well on deep sky and also has some coma at edges. The main advantage of f4 over f5 would be bigger exit pupil for same eyepiece. Yes, if you are going to figure your own mirror you are better off with f5 or f6, but if you are going to purchase a bigger commercially figured mirror consider faster than f5. There are well done fast mirrors available. SLAS gave an our John Dobson figured 18" f7 0r 8 to the Ogden Club because we had a hard time storing it and getting someone to use it. Perhaps we would not have had the problem at f5, but it would still be about 18" taller than an f4 My primary concern has been my own use ( I find myself unable to use most scopes I have not tailored to my own use), seems to me, the more convenient the scope is for yourself that it will also be convenient to others. Seems most oldtimers have sore necks and backs. Erik --- chuck.hards(a)gmail.com wrote: From: "Chuck Hards" <chuck.hards(a)gmail.com> To: "Utah Astronomy" <utah-astronomy(a)mailman.xmission.com> Subject: Re: [Utah-astronomy] 13.1 inch Coulter Carcass, free Date: Wed, 7 Jan 2009 17:53:04 -0700 The wrong ladder in the dark can definitely be hazardous, but that's not exactly a problem with a long-focus telescope; it's the wrong choice of ladder. The right choice might not be easily transported, or even easily used at the eyepiece, so that's one of those choices people make. I think the original context of the question was short focal-length mirrors as a first effort at mirror grinding. They do take more work and can be more difficult to figure, but it's not out of reach of the average person, given the proper guidance. If, however, one is purchasing a commercially-made mirror, all the caveats of fabrication can be ignored. I don't agree that deep-sky observing is better at f/4, as a blanket statement. My little RFT is an f/5 and the coma is noticeably less than otherwise identical telescopes I built at f/4, yet the field isn't much smaller using the same eyepiece. I also don't weigh my equipment choices against their fit at a public star party. I'm kind of selfish with my astro-time- my personal enjoyment is my prime motivation. I'll blow-off being "star-party correct" in a heartbeat if I feel I can get some kind of advantage by doing so. On nights when I'm specifically doing the public outreach job, then convenience and safety will trump imagery out of necessity. The telescope must be designed for it's intended use. One person's trade-off list will probably not correspond one-for-one with someone elses. On Wed, Jan 7, 2009 at 1:59 PM, <zaurak(a)digis.net> wrote: > The narrow steps on a ladder can take a toll on your feet in the course of > a night. The classic dobson is long focal length, but there are many > companies that do a good job on fast optics in the 4f range. Deep sky > observing is better with f 4's. > > Tall ladders seem a liability for public star parties. > > > _______________________________________________ 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] Utah-Astronomy Digest, Vol 71, Issue 17
by zaurak＠digis.net 08 Jan '09

08 Jan '09

I love looking at Planetaries with the Grim, 10 power for inch with that is 320x but many are better at higher mag. --- chuck.hards(a)gmail.com wrote: From: "Chuck Hards" <chuck.hards(a)gmail.com> To: "Utah Astronomy" <utah-astronomy(a)mailman.xmission.com> Subject: Re: [Utah-astronomy] Utah-Astronomy Digest, Vol 71, Issue 17 Date: Wed, 7 Jan 2009 18:07:34 -0700 That's a good rule-of-thumb. A couple of exceptions are those tiny, blue planetaries and very distant globulars. But 10X/inch is good for 90% of the faint fuzzies. You can bump it up a bit with smaller apertures, to help increase contrast. On Wed, Jan 7, 2009 at 2:03 PM, <zaurak(a)digis.net> wrote: > > I have always felt 10 power per inch is ideal magnification for most > deepsky objects. > > _______________________________________________ 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] Utah-Astronomy Digest, Vol 71, Issue 18
by zaurak＠digis.net 08 Jan '09

08 Jan '09

Chuck and Bruce Grim are some of those hardcore oldtimers. The 32" Grim is truly an ATM project. I built 3 or 4 and stopped, I have the astro equipment that I need and can afford. Perhaps I will build one similar to Bob's someday. I think that the hobby has become profitable for vendors and there are many excellent scopes ready to buy, I think this is why ATMing has waned a little, at least among SLAS. I think this list attests that the photographic aspect of hobby has not suffered. I remember the 90's at Riverside when amateurs present their ATM projects that become commercial projects shortly there after. The Obsession is a prime example. Erik --- chuck.hards(a)gmail.com wrote: From: "Chuck Hards" <chuck.hards(a)gmail.com> To: "Utah Astronomy" <utah-astronomy(a)mailman.xmission.com> Subject: Re: [Utah-astronomy] Utah-Astronomy Digest, Vol 71, Issue 18 Date: Wed, 7 Jan 2009 18:00:41 -0700 There are more hard-core ATM's alive today than at any time in history. They are a smaller percentage of all amateur astronomers, however, and tend to be more high-end than they were a generation or two ago. Most are engineers and professionals in other fields. Most work independently. ATMing as the standard entree into the hobby is an anachronism, for the reason Bob noted. Those are the ones he and Erik are remembering. On Wed, Jan 7, 2009 at 3:21 PM, Robert Taylor <robtaylor3661(a)comcast.net>wrote: > I think cheap telescopes with good optics has taken it's toll on telescope > making. > > Bob > > > Message: 4 > Date: Wed, 7 Jan 2009 12:53:56 -0800 > From: <zaurak(a)digis.net> > Subject: Re: [Utah-astronomy] 13.1 inch Coulter Carcass, free > To: "Utah Astronomy" <utah-astronomy(a)mailman.xmission.com> > Message-ID: <20090107125356.A97D6D63(a)resin09.mta.everyone.net> > Content-Type: text/plain; charset="UTF-8" > > dinosaur carcass to boot. Seriously SLAS used to have a good number of > people building telescopes. What happened to that? I wonder if Amateur > Telescope Making is on the decline. > > Erik > > _______________________________________________ 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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Gallery - More from Ken
by Patrick Wiggins 08 Jan '09

08 Jan '09

I just got off the phone with SLAS Webmeister Ken (I'm glad he works the same hours I do). He said there's still a goodly bit of work to be done but he hopes to have something up and running in time to demo it at this month's SLAS board meeting. I asked him about such things as backups and reliability. He says he makes multiple backups and that his drives are rated for 1 million hours of continuous use. patrick

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