Re: [Utah-astronomy] 13.1 inch Coulter Carcass, free
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. Erik --- jimgibson00@yahoo.com wrote: From: Jim Gibson <jimgibson00@yahoo.com> To: Utah Astronomy <utah-astronomy@mailman.xmission.com> Subject: Re: [Utah-astronomy] 13.1 inch Coulter Carcass, free Date: Wed, 7 Jan 2009 10:04:09 -0800 (PST) When I took the class from Brent Watson he wanted all of us (about 5 or 6 in the class) to make f8 or better scopes. Brent loved long bugger scopes and rightfully so I would say. Someone more qualified than I can tell you all the benefits of a long scope beside increased contras and increased power, but I recall there a lot of benefits…oh yeah collimation is easier too. Most everyone in our class wanted to make short (fast) scopes mainly because nobody wanted to use a ladders. I went with an f7 (the longest focal length in class) so with a 12.5” mirror which would be 87.5” focal length plus some extra I believe my sono tube was about 96” long. How do you get 96" in the car you ask? Can you get 48” in your car? I could deal with 48” so I cut the sono tube down so I had 2 48” sections. I still had sono tube left over because if I remember right it was about 12’ long when I bought it. From the extra piece I cut a 1 foot section then slit it down length wise, took some extra material out till I could get it to fit inside one of the 48” sections forming a sleeve. I went to the hardware store and got some of those clampy thingys like on a metal tool box and put 3 of them on to fasten the 2 scope pieces together. It worked great! I have a ladder and a step stool with long hold onto bars, but a lot of the time I use nothing or the step stool. Yeah, right now I would need the ladder to see M31. I love the way my scope performs. I have never been sorry about going f7, but sometimes I do think I should have listened to Brent and gone f8. Chuck Hards or someone can tell you stories about Brent fastening his like f10 to the top of his car and having it come off the tope while heading down the freeway…hehe. The mirror was just fine. Brent had a couple of 12.5” f12 or something scopes in his hanger where we took the class. The good old days. jg --- On Wed, 1/7/09, Tyler Allred <tylerallred@earthlink.net> wrote: From: Tyler Allred <tylerallred@earthlink.net> Subject: Re: [Utah-astronomy] 13.1 inch Coulter Carcass, free To: "'Utah Astronomy'" <utah-astronomy@mailman.xmission.com> Date: Wednesday, January 7, 2009, 10:17 AM Warning--- Please don't take this toungue-in-cheek comment the wrong way. WOW! Who would have thought that an offer of a "dismembered carcass" would generate so much discussion? I love this list! :) Tyler _____________________________________________ _______________________________________________ Utah-Astronomy mailing list Utah-Astronomy@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@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
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@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.
participants (2)
-
Chuck Hards -
zaurak＠digis.net