March 2012 - Utah-Astronomy - mailman.xmission.com

Diffraction effects of secondaries and spiders (Was: solar filter)
by Chuck Hards 08 Mar '12

08 Mar '12

All of the curved vane commercial spiders I have seen use very thick vanes, as a way to eliminate vibration. They actually decrease the throughput to the primary over a straight-vaned spider and increases overall diffraction. As you point out, Mat, it's a personal aesthetic to not want to see spikes, but the telescope is in truth hobbled a bit when it comes to fine planetary detail and resolution, when using a thick-vaned curved spider. My 4.25" f/5 Newt has a home-made secondary holder that I've never really been happy with. I'll probably replace it with a single-stalk holder, or incorporate an optical window (I have a couple of surplus windows that I think originally were intended for Edmund Astroscans) I originally built my 6" f/8 Newt with a single-stalk secondary holder, a brass rod. It blocks no more light than a conventional 4-vane spider, and I only see two diffraction spikes, 180-degrees apart. That telescope has a 1.25" low-profile helical focuser but I am now upgrading to a 2" wyoroc Crayford. I have to replace the single-stalk secondary holder because it was attached via a mounting hole in the focuser that is going to disappear. I'm going to go with a conventional 4-vane spider and a spring-loaded home made secondary holder. I'll just have 4 dimmer spikes instead of two brighter ones. Everything I've ever built larger than 6" has always used a 4 vane spider. On Thu, Mar 8, 2012 at 8:53 AM, Hutchings, Mat (H USA) < mat.hutchings(a)siemens.com> wrote: > We made a curved vane spider which consisted of one ~170 degree vane to > which the secondary hub was mounted. The views were really great without > the spikes and I really liked it. However, that vane wiggled like Santa > Claus's belly any time the scope was touched. I worked, and worked to > improve the design and did make some strides, but it just didn't perform > well enough for me. > >

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Re: [Utah-astronomy] astro-tourism Review & Number of Traveller to this
by Rashidi 08 Mar '12

08 Mar '12

I need information about astro-tourism and number of visitors too. I couldn't foundarticle or Book aboute this, my thesis topic is astro-tourism in Iran. who could help me? Regards Tourism Management (B.A) & Tourism Management (M.A.)Allameh Tabatabai University Tehran, Iran Manager of the department of Tourism and Hospitality of Center for Technology Studies of Sharif University of Technology Tehran, Iran Office : +98 2166082092 Mobile : +98 917849 0749 Web : http://rashidi.mihanblog.com Email: Rashidi.tourism(a)yahoo.com

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ATM session report; sorry but it is long!
by Hutchings, Mat (H USA) 08 Mar '12

08 Mar '12

The ATM session on 3/3 was the most heavily one attended yet. Charlie, Jay, Jeff, Josh, Troy, Levi and Hayden all attended. Things got rolling with us testing Jeff's 10" mirror from his Orion dob. We tested it to be just better than 1/4 wave. There was a central hill, but it is hidden by the secondary. The surface looked reasonably smooth and there was no clear evidence of excessive zoniness. Jeff's plans are to eventually rework the mirror. At that time, and after the coatings are stripped off, we'll have a better look at the overall smoothness and polish. He then will decide to just touch up the figure or perhaps more fully polish it. After that test, Jeff showed up how to properly use the Catseye collimation tools. This was impressive to me. It certainly looks to be a very thorough way to collimate. Thanks Jeff for sharing! Jay brought plans to share for the best observing chair I have seen yet. He has posted the plans for that chair on this forum under the ATM heading. He plans to start building the chair during the next session, maybe before. Josh started polishing his 4" project. His 4" pitch lap was previously used on an 8" mirror so we first pressed the lap into contact with the 4" mirror. This took a fair amount of time since the lap originally had a ROC of 96" and the 4" mirror has a ROC of 32 inches. A couple of hot presses and it was making fairly good contact expect for the very center. Since mirrors almost always polish from the center out, I encouraged him to go ahead and start polishing and eventually the lap would fully conform and the center would then catch up. After a 15 minute stint, we checked it and sure enough, the center was not shiny, but from about 1.5 inches out it was. A Ronchi test showed that the mirror is spherical. Fortified by this good news, Josh was rededicated and started polishing again with Jeff and I taking a turn. After another hour or so, the center was now shiny and the Ronchi test showed a very nicely spherical mirror with no TDE. Good job, Josh on your first mirror! He just has more polishing ahead and then figuring. Troy and sons Levi and Hayden came by to start work on the mechanical part of their 8" dobsonian. We got the tube-cradle boards cut and partially glued and reinforced. Next step is to make the mirror cell and the rocker box. Fun stuff! Keep pushing glass! Mat

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Seeking suggestions for repairing the RH Dome
by jcarman6＠q.com 08 Mar '12

08 Mar '12

Gad, stop cluttering up the e-mail box Sandblast the dome to the bare metal, pound or round it up so it look like a dome. It looks like it's been hit by goliath with his club a number of times. Weld the seams, apply sealant and do whatever and repaint. Yes, I know this is a HUGE job. Maybe get bids from local companies. At least you will have something that looks like a real dome and will last for many years to come (and you keep the sentimentality) If you do patchwork, you will be doing it again and again, maybe even every year. Either that or dump it and get a new dome.

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In the news
by Steve Fisher 08 Mar '12

08 Mar '12

Do I sense an aurora watch approaching.http://www.ksl.com/index.php?sid=19492969&nid=1012&title=solar-…

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Fwd: Re: Seeking suggestions for repairing RH dome
by Larry Holmes 08 Mar '12

08 Mar '12

Thank you, Patrick. I was worried that it would look like I am tooting my horn, and that is not the case. 73, lh -------- Original Message -------- Subject: Re: [Utah-astronomy] Seeking suggestions for repairing RH dome Date: Tue, 6 Mar 2012 23:49:55 -0700 From: Patrick Wiggins <paw(a)wirelessbeehive.com> To: Larry Holmes <larry(a)kijoda.com> Hi Larry, Excellent thoughts. Please post them to Utah-Astronomy (or I can forward your post there if you like). patrick On 06 Mar 2012, at 23:32, Larry Holmes wrote: > On 3/5/2012 8:05 PM, Patrick Wiggins wrote:> The results of today's inspection of SPOC's Refractor House dome are not encouraging.> > Basically, water sprayed on the outside poured right through to the inside.> > Leaks everywhere and lots of them. > > 1. First of all, Patrick, is to decide just what you want to accomplish and how that end is to be achieved. > > 2. The next step is to determine the total square footage to be covered. This gives you a base to start from to estimate materials required, either by club members, or by a contractor. Any contractor worth his salt will double check the figures. > > 3. 90%+ of success of any job like this depends upon the degree of surface preparation. You could buy the most expensive material available, but if it is just slapped over the existing surface, it is due to fail prematurely. > > 4. In most cases, you are going to need a sand blast. It maybe only a "sweep blast", or the product used may call for "a white metal blast." It may need only a hand or power tool cleaning. The product used will determine the specific degree of cleaning required. One item, often overlooked, is a high pressure wash to remove not only surface contaminents, but more importantly, salt. If you just do a sand blast, any salt on the surface can just be driven into the surface profile left by the blast procedure. Then, if coated over, it leaves pockets which will eventually rust, leading to disbondment& again, early failure. There are additives to add to the wash water to aid in salt removal. > > 5. I might as well address a couple of theroems postulated in earlier postings: a) "You cannot bond fiberglass strips to metal" is hogwash, pure and simple, as is the notion epoxy will last just a year. The paints most used by such as KUCC, the salt plants around the Lake, water treatment plants, steel tanks for potable water (total immersion service), are epoxies. The other is the idea of depolymerization due to high summer heat. Once an epoxy cross- links, it will take temps on the order of fire to do that. Just look at UDOT's bridges--their spec calls for all surfaces not exposed to sunlight to be coated with epoxy. I know as I sold the coatings used by UDOT for some 10 years. The main downgrade to an epoxy for exterior coatings is that they are not UV restant and tend to fade in color rapidly. > > 6. My suggestion is to use a flexible, rubberized coating. Many could be applied by brush, roller, or spray. That would mean club members could apply if you are looking to save $$. But, if you want something on the order of a 50 year life (one posting states observatories are passe, so maybe you do not need that life, just perhaps 10 or 20 years). In that case, see #1). I totally agree with Dan. This needs to be done by a contractor. > > 7. You may question my bona fides. I have sold (and still do) industrial coatings for over 30 years. I have been a member of NACE (National Associan of Corrosion Engineers). SSPC (they set the standards of what constitutes a certain grade of surface preparation), PDCA. Sampe, as well as various other proffessional organizations. I still maintain a membership in WEUA, a fancy name for sewage plant operators. I am not, nor do I profess to be, an engineer. But, rust& corrosion is my business. I would be pleased to sit in on any committee, or what ever, to offer any help I can. This has been kinda wordy, but I had a lot to say, so I apologize for for the length. 73, lh

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New Astronomy Thread
by jcarman6＠q.com 07 Mar '12

07 Mar '12

Smiley faces back at y'all.

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New Astronomy thread
by jcarman6＠q.com 07 Mar '12

07 Mar '12

This thread is about astronomy, any. No mention of SPOC, the RH Dome, or SLAS is permitted. If someone mention the forbidden topics , a very wet raspberry will be delivered at the earliest opportunity. Apparently we are about to be hit, may an aurora visible in Utah be sure to follow: http://www.mycenturylink.com/news/read.php?rip_id=%3CD9TBON3G1%40news.ap.or…

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Re: [Utah-astronomy] Seeking suggestions for repairing RH dome (from Bruce)
by Patrick Wiggins 07 Mar '12

07 Mar '12

Bruce is not on Utah-Astronomy but sent me the following. Let's do as he says and hire a welder for the seams between the gores, around the door and the former slit. Then we can concentrate on the dome/roof interface. patrick Begin forwarded message: > From: "BRUCE GRIM" <bmargrim(a)msn.com> > Subject: Re: [Utah-astronomy] Seeking suggestions for repairing RH dome > Date: 07 March 2012 08:40:47 MST > To: "Patrick Wiggins" <paw(a)wirelessbeehive.com> > > Welding will work on the dome seams - we could tie a ladder to the dome and get a mountaineers belaying harness for the welder to tie him in safely. > > Better yet hire a pro-welder and rent a bucket truck. A pro could weld it in half the time (or less) than we would take. > > > ----- Original Message ----- > From: Patrick Wiggins > To: Utah Astronomy > Cc: (S) Grim Bruce > Sent: Wednesday, March 07, 2012 12:02 AM > Subject: Re: [Utah-astronomy] Seeking suggestions for repairing RH dome > > Welding! So simple I feel dumb for never having thought about that. > > I'm pretty sure the dome is made of thick enough steel that welding just might work and there's no way water is ever going to leak through a proper weld. > > Then, as was said before, all we'd have to worry about would be leaks where the dome joins the roof. > > I understand that Rodger Fry is already in talks with a company (as Kim suggested) that does commercial roofing. Certainly they could fix the leaks at the base of the dome. > > Plus I heard from Larry Holmes that he's been in the business of selling industrial coatings for over 30 years and he seemed fairly upbeat about the repairs. > > When I first saw how badly the dome is leaking I was really down thinking we might not be able to get it up and running again this season. But now things are not looking quite as dark. > > patrick > > > On 06 Mar 2012, at 19:57, Chuck Hards wrote: > > > On Tue, Mar 6, 2012 at 1:18 PM, Rob Ratkowski Photography < > > ratkwski(a)hawaii.rr.com> wrote: > > > >> I think you all have to decide how much $$ to be spent and how much of a > >> PITA factor it is. > > > > > > That was my first post on the subject. I'm glad to read that Kim is > > starting to think my way regarding welding. I've been thinking about it > > today, and it could probably be done in one long weekend. As one seam is > > sandblasted, the welder goes to work while another is prepped. Safe > > scaffolding is going to be biggest hurdle. > > > > Finally, a painter follows-up with primer and a couple of topcoats of good > > exterior grade paint. Patrick Wiggins paw(a)wirelessbeehive.com

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Re: [Utah-astronomy] useless facts
by sfisher01＠comcast.net 07 Mar '12

07 Mar '12

Never? ----- Original Message ----- From: "Spencer Ball" <spencer(a)spencerball.com> To: "Utah Astronomy" <utah-astronomy(a)mailman.xmission.com> Sent: Thursday, December 23, 2010 1:27:05 PM Subject: Re: [Utah-astronomy] useless facts We'll never see past the cosmic microwave background, much less see light from clear all the way around. Spencer Ball -----Original Message----- From: utah-astronomy-bounces(a)mailman.xmission.com [mailto:utah-astronomy-bounces@mailman.xmission.com] On Behalf Of sfisher01(a)comcast.net Sent: Thursday, December 23, 2010 1:12 PM To: utah-astronomy(a)mailman.xmission.com Subject: [Utah-astronomy] useless facts I read this on the usless facts gadget on my desktop. I'm not sure I understand it. Care to comment? A sunbeam setting out through space at the rate of 186,000 miles a second would go in a gigantic circle and return to its origins after about 200 billion years. _______________________________________________ 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://www.slas.us/gallery2/main.php 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://www.slas.us/gallery2/main.php Visit the Wiki: http://www.utahastronomy.com

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