February 2003 - Utah-Astronomy - mailman.xmission.com

Diffraction & curved spiders
by Chuck Hards 27 Feb '03

27 Feb '03

Dave, I used a curved spider on my 4.25" f/5 "Woodshop" scope. I didn't get quite enough curve in it, however, and bright objects have short, curved "horns", that dwindle-off into invisibility. This scope demonstrates a mid-point between straight spider vanes, with reinforced diffraction, and curved vanes, bent sharply enough to distribute diffraction effectively. I have an optical window for this scope, and have planned to retrofit it for years now (it's a long "to-do" list) but I'll keep it in it's current configuration and bring it to this year's Binopalooza if anyone wants to inspect it. Keeping conventional vanes as thin as possible helps reduce diffraction. Many ATMs have used thin wire as spider material, and claim huge reductions in diffraction spikes. C. __________________________________________________ Do you Yahoo!? Yahoo! Tax Center - forms, calculators, tips, more http://taxes.yahoo.com/

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RE: [Utah-astronomy] Goodwin Mask (short)
by David Dunn 27 Feb '03

27 Feb '03

One more comment. As I understand it, I still have diffraction with a curved spider. It is just that the diffraction is curved like the stars and planets. -----Original Message----- From: David Dunn [mailto:david.dunn@albertsons.com] Sent: Thursday, February 27, 2003 8:53 AM To: 'utah-astronomy(a)mailman.xmission.com' Subject: RE: [Utah-astronomy] Goodwin Mask (short) I have put curved spiders on three of the four telescopes I have built. I think that it is easier to build the curved spider than to built a vaned spider. I think that I understand the concept of the mask that sits on the mirror. How do you get it lined up on the mirror correctly? It would seem that if you didn't get it just right it wouldn't work. Dave -----Original Message----- From: David L Bennett [mailto:dlbennett@mac.com] Sent: Wednesday, February 26, 2003 11:10 PM To: utah-astronomy(a)mailman.xmission.com Subject: Re: [Utah-astronomy] Goodwin Mask (short) Brent/Bob, Is it possible that because the mask is, essentially, touching the mirror there is not the diffraction inherent with the spider and secondary obstruction? I mean, yes, there is a larger obstruction but isn't that obstruction basically diffraction free because of it's proximity to the mirrors surface? I would think that would be the only reason to place it upon the mirror as opposed to above the secondary mirror/spider where an aperture stop or apodizing mask normally would be placed. David Bennett On Wednesday, February 26, 2003, at 10:02 PM, Brent Watson wrote: > Bob, > > This is an interesting idea, but I don't see that it > would make the view any netter. The mask still acts > like the spider, and in fact is worse because it is > wider. It MAY get rid of the temperature effects > mentioned in the article. I would be scheptical about > it working, and would have to conduct several careful > tests to see if it made an improvement. > > Brent _______________________________________________ Utah-Astronomy mailing list Utah-Astronomy(a)mailman.xmission.com http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy _______________________________________________ Utah-Astronomy mailing list Utah-Astronomy(a)mailman.xmission.com http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy

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RE: [Utah-astronomy] Goodwin Mask (long)
by Kim Hyatt 27 Feb '03

27 Feb '03

It was precisely this phenomenon that allowed a Celestron Ultima 2000 belonging to Don Colton to split Eta Cor Bor (.8 arc second) where the 9" Clark could not. Both were being used at somewhere around 450x. -----Original Message----- From: Chuck Hards [mailto:chuckhards@yahoo.com] Sent: Thursday, February 27, 2003 8:51 AM To: utah-astronomy(a)mailman.xmission.com Subject: Re: [Utah-astronomy] Goodwin Mask (long) Because diffraction can be "channeled", sometimes telescopes with large central obstructions or widened spider vanes prove useful, especially if splitting close double stars. By moving energy from the central spot into the diffraction rings, the spot can be decreased in size and allow close companions to be seen, where in an unobstructed system, while the rings are weaker, the central spot is larger and overlaps the companion star. C. __________________________________________________ Do you Yahoo!? Yahoo! Tax Center - forms, calculators, tips, more http://taxes.yahoo.com/ _______________________________________________ Utah-Astronomy mailing list Utah-Astronomy(a)mailman.xmission.com http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy

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Follow-up On Search For Shuttle Columbia Debris In Southern Utah
by davidbuell＠attbi.com 26 Feb '03

26 Feb '03

Hello SLASers, After my brief presentation last nite at SLAS about the search for Columbia debris in Southern Utah, I promised to let you know if we received any more information about the object in the Civil Air Patrol photo #102. Following is a quote from a message we received today, 26 Feb, from Dean Cox, Emergency Management Director for Washington County. QUOTE Yesterday at 15:00 MST I revisited the site located by the CAP. The coordinates put us within 125 feet of the object, however the search was hampered by 1 foot of fresh fallen snow. After studying the photo, I started kicking at the snow and on the second or third swath I hit PAYDAY! As my foot exposed a piece of lightweight chrome colored metal, I anxiously brushed the snow from the metal object with my gloved hand, which revealed an edge which was burned and blued from heat. My heart raced! Amidst congratulatory backslaps, Pete Kuhlmann wretched the piece from its icy enclave and we were astounded to see a piece of bumper from an old Ford Mercury, which had been cut by an Oxy-Acetylene torch, out in the middle of no-where! The ground searchers probably had located the piece but because of its Ford logo and obviousnes didn't even bother to call it in. It was a great GPS exercise anyway! END QUOTE Although we may be disappointed that no debris were found that were verified as belonging to Columbia, I hope you found the details of the search efforts interesting. I very much enjoyed all the presentations given last nite. David C. Buell Technical Support Specialist Utah Department of Public Safety Division of Emergency Services and Homeland Security 1110 State Office Building PO Box 141710 Salt Lake City, Utah 84114-1710 Tel: 801-538-3632 FAX: 801-538-3772 E-mail: dbuell(a)utah.gov Web: http://des.utah.gov

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Foreground?
by David L Bennett 26 Feb '03

26 Feb '03

Foreground? Now THAT would be a trick. db > These anticrepuscular rays are amazing! Horseshoe Canyon is such a > wonderful place too. Thanks Dave, Dave > > In case anyone misses the pic go to: > > http://antwrp.gsfc.nasa.gov/apod/image/0302/antihorse_peterson.jpg > > and > > http://antwrp.gsfc.nasa.gov/apod/image/0302/antihorse_peterson_big.jpg > > I've got the larger version as my wallpaper right now...beautiful. > What stars are in the FOREGROUND do you think? I can't place them. > dlb > > > > On Wednesday, February 26, 2003, at 06:53 AM, David Dunn wrote: > >> There is a picture of something that was discussed on the list a few >> weeks >> ago on APOD today. They have a picture of Antirepuscular Rays over >> Horseshoe >> Canyon here in Utah. I know most of you probably look at APOD every >> day but >> I thought I would post the link for those that haven't been >> introduced to >> these pictures. >> >> http://antwrp.gsfc.nasa.gov/apod/astropix.html >> > > Dave

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APOD Today
by David Dunn 26 Feb '03

26 Feb '03

There is a picture of something that was discussed on the list a few weeks ago on APOD today. They have a picture of Antirepuscular Rays over Horseshoe Canyon here in Utah. I know most of you probably look at APOD every day but I thought I would post the link for those that haven't been introduced to these pictures. http://antwrp.gsfc.nasa.gov/apod/astropix.html Dave

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Fwd: News, 26 FEB 2003 (w/ fixed links)
by David L Bennett 26 Feb '03

26 Feb '03

I hope you don't mind Patrick...I fixed the +++++ problem with the links Begin forwarded message: From: Patrick Wiggins <paw(a)trilobyte.net> Date: Tue Feb 25, 2003 11:25:21 PM US/Mountain To: paw(a)trilobyte.net Subject: News, 26 FEB 2003 Reply-To: paw(a)trilobyte.net News, 26 FEB 2003 SPOC Training Update The Ealing introductory class for the evening of Saturday, 8 March is full. Two spots remain in the Friday, 7 March class. Those wishing to qualify for a key to the observatory need to first take an introductory class followed by an advanced class and final checkout. Additional introductory classes will be held throughout the observing season. +++++ Pioneer 10 Spacecraft Sends Last Signal After more than 30 years, it appears the venerable Pioneer 10 spacecraft has sent its last signal to Earth. http://www.nasa.gov/HP_news_03082.html +++++ More Moons Over Pluto? Pluto has only one known satellite - Charon - discovered in 1978 by American astronomer James Christy. Recently, astronomers have discovered that some large Kuiper Belt Objects also have large satellites. This suggests to the New Horizons mission team that Pluto might have other, as-yet undiscovered satellites. http://pluto.jhuapl.edu/022403.htm +++++ Genesis Hits Halfway Mark! Genesis has passed the midpoint of its record setting solar sample return mission. As of today, the Genesis spacecraft has logged 565 days in space and has only 562 days remaining until Earth return. http://www.genesismission.org/mission/statusupdate.html +++++ Flying With Nature's Own Fuel Hundreds of years ago, early discoverers used the Sun as a compass. Turns out the light of the Sun can do more than just guide us; it can actually propel us farther and faster into the vast realm of space than we've ever been able to go. http://www.jpl.nasa.gov/technology/features/solarsails.cfm +++++ NASA's Newest Seawinds Instrument Breezes Into Operation One of NASA's newest Earth-observing instruments, the SeaWinds scatterometer aboard Japan's Advanced Earth Observing Satellite 2 has successfully transmitted its first radar data to our home planet, generating its first high-quality images. http://www.jpl.nasa.gov/releases/2003/24.cfm +++++ The Cosmos 1 Update The development of the Cosmos 1 solar sail spacecraft is going well despite some delays with some of the spacecraft electronics. We are, however, waiting for problems to be resolved with our launch vehicle, the Volna. Until then, we are prisoners on Earth, trapped in our planet's gravity well. http://www.planetary.org/solarsail/Media.htm +++++ Green Light For World's Most Powerful Radio Observatory Dr. Rita Colwell, director of the U.S. National Science Foundation (NSF), and Dr. Catherine Cesarsky, director general of the European Southern Observatory (ESO), today signed a historic agreement jointly to construct and operate ALMA, the Atacama Large Millimeter Array, the world's largest and most powerful radio telescope operating at millimeter and sub-millimeter wavelengths. http://www.aoc.nrao.edu/epo/pr/2003/almasigning/ +++++ Fossil Plant and Insect Communities Key to Understanding Global Change Insect damage recorded in fossil plants and the types of plants present in the fossil record are helping researchers to understand how ecological communities recover from climate change and mass extinction events, according to a Penn State paleontologist and his colleagues. http://www.psu.edu/ur/2003/leafinsects.html +++++ OK, Our Next Caller Is... From Mars! It is midnight on 1 January 2004 and you want to send a greeting on your mobile phone to a friend. Sorry, the line is too busy, try again later. If you think you are alone with this problem, you are wrong. Space agencies have had to work out ingenious solutions to prevent similar 'engaged, call later' tones from happening on Mars. For the first time, there will be seven spacecraft on the Red Planet at the same time. Will they all be able to 'phone home'? http://sci.esa.int/content/news/index.cfm?aid=9&cid=32&oid=31426 +++++ A Most Surprising Observation "Quite by accident, we have made a most surprising observation," reports Don Pettit, the science officer of the International Space Station. It happened during his spare time on a Saturday morning last month. Pettit was preparing to make some weightless soap bubbles--just for fun--when he discovered a very curious property of water in space. http://science.nasa.gov/headlines/y2003/25feb_nosoap.htm?list726251 +++++ A Bit O' Humor Non-astronomical but topical... http://planet.state.ut.us/GASPRICES.JPG +++++ ************************************************** News is being sent to you because of your affiliation with an astronomy club in Utah or because you asked to be subscribed. To unsubscribe please send your request to paw(a)trilobyte.net. News Internet access provided by: Trilo BYTE, http://www.trilobyte.net. Check out my NASA Solar System Ambassador web site at: http://planet.state.ut.us For astronomy clubs in Utah see: http://planet.state.ut.us/utahclubs.html For the Utah Astronomy Listserve see: http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy ************************************************** -- Patrick Wiggins NASA Solar System Ambassador to Utah http://planet.state.ut.us 435.882.1209 (observatory) 801.918.9092 (cell)

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Apogee "lightweight" 20x80mm binos
by Chuck Hards 25 Feb '03

25 Feb '03

Has anyone picked-up the Apogee "lightweight" 20x80mm binos? These are the $129.95 model, not the $179.95 version. They look like the Obie/Bear/Galileo prism housing with a larger objective cone... How about the 25x100mm? Anyone take the plunge yet? Thanks C. __________________________________________________ Do you Yahoo!? Yahoo! Tax Center - forms, calculators, tips, more http://taxes.yahoo.com/

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test (please delete)
by David L Bennett 24 Feb '03

24 Feb '03

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RE: [Utah-astronomy] Mirrors
by David Dunn 23 Feb '03

23 Feb '03

I hadn't thought of the area of the mirror. I just ran the numbers. I could get my eyepiece down to about 60" using a 7.3" diagonal. That would leave 93.1% of the area of my mirror unobstructed. My secondary would be 132" from the primary. That will be real tempting since I use curved spiders anyway. I just didn't want to block all the light. Dave -----Original Message----- From: Chuck Hards [mailto:chuckhards@yahoo.com] Sent: Friday, February 21, 2003 1:58 PM To: utah-astronomy(a)mailman.xmission.com Subject: RE: [Utah-astronomy] Mirrors Dave, consider a modified Newtonian approach, where the diagonal is set at a much lower angle than 45-degrees. The light beam is shot back down the tube and exits at a grazing angle, basically as low on the tube as you want. A third mirror can then turn beam back out at a right angle to the tube. Once you get above 16" inches or so, the light loss of a secondary mirror becomes minimal in proportion to total area. The major advantage of an unobstructed system is a lack of diffraction artifacts, but unless you get the correction JUST RIGHT, the lack of diffraction spikes & better energy distribution in the diffraction rings won't offset the astigmatic images. And even the best unobstructed systems I've seen don't produce textbook-perfect spot diagrams. Also, typically the larger the unobstructed system, the more difficult the optical work, -AND- an absoulutely rigid tube assembly is mandatory. My 6 cents. C. --- David Dunn <david.dunn(a)albertsons.com> wrote: > I think that next year I will try making a 20" f/10. > I plan to fold the > optics and view from the ground. I am researching > this year to see how I can > correct for Astigmatism and Coma because I would > like to put the secondary > off axis. So far I think I will have the 20" ground > to f/10. I will use a > 10" secondary and f/8 and bring the light back down > to a diagonal to put the > light in my eyepiece. > > Dave > > -----Original Message----- > From: Brent Watson [mailto:brentjwatson@yahoo.com] > Sent: Friday, February 21, 2003 11:06 AM > To: utah-astronomy(a)mailman.xmission.com > Subject: Re: [Utah-astronomy] Mirrors > > > My 22 inch is f6.3. Only a couple of folks have > required oxygen. > > Brent > > --- Greg Taylor <astronomus_maximus(a)yahoo.com> > wrote: > > Imagine a 30" f/7... > > > > "Pass me that pressure suit willya?" > > > > "Sure thing; oh, and watch out for those > satellites, > > they come a little close. By the way, did you > > remember > > your parachute?" > > > > "Naw, I'd just burn up if I fell anyhow..." > > > > Cave made some sweet mirrors, so I've been told. > > You > > can probably get some nice high power views with > it > > too. > > > > Agreeing with what Chuck said, my 10 f/5.6 does a > > better job than it would if it were f/4.5, being > > mass > > produced and all. On a rare night of perfect > seeing > > last summer (very far from here), I was able to > push > > it to 580x without image degradation. I saw detail > > on > > Uranus! (Boy that dob driver comes in handy at > those > > high magnifications) > > > > > > --- David L Bennett <dlbennett(a)mac.com> wrote: > > > Don't forget considerations of field of view! > My > > > 10" f/5 Cave with a > > > 40mm Tele Vue Wide Field gives some very > > impressive > > > Milky Way shots ;) > > > > > > On Friday, February 21, 2003, at 09:58 AM, > Chuck > > > Hards wrote: > > > > > > > Everyone should, unless there is a specific > > reason > > > for > > > > going "short". Of course, legitimate reasons > > > include > > > > transportation and ergonomics. > > > > > > > > Brent's always been right-on in that > department! > > > :) > > > > > > > > C. > > > > > > > > > _______________________________________________ > > > Utah-Astronomy mailing list > > > Utah-Astronomy(a)mailman.xmission.com > > > > > > http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy > > > > __________________________________________________ > > Do you Yahoo!? > > Yahoo! Tax Center - forms, calculators, tips, more > > http://taxes.yahoo.com/ > > > > _______________________________________________ > > Utah-Astronomy mailing list > > Utah-Astronomy(a)mailman.xmission.com > > > http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy > > > __________________________________________________ > Do you Yahoo!? > Yahoo! Tax Center - forms, calculators, tips, more > http://taxes.yahoo.com/ > > _______________________________________________ > Utah-Astronomy mailing list > Utah-Astronomy(a)mailman.xmission.com > http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy > > _______________________________________________ > Utah-Astronomy mailing list > Utah-Astronomy(a)mailman.xmission.com > http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy __________________________________________________ Do you Yahoo!? Yahoo! Tax Center - forms, calculators, tips, more http://taxes.yahoo.com/ _______________________________________________ Utah-Astronomy mailing list Utah-Astronomy(a)mailman.xmission.com http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy

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