My $50 refractor, and a request for assistance
The tube of my 8" f6 Cave takes up the majority of the usable space in the back seat of my Dakota extended cab, which has been fine for shorter trips with our camper, but my wife isn't willing to put up with that for the duration of our upcoming 2 week trip to Baja over Christmas. So I set out to make an inexpensive refractor that would take up less space, and accomplished it for $50. But a serendipitous afterthought led to an upgrade that is adding another $200 to the total investment. I ordered a 80x900 objective with plastic cell from Surplus Shed for $30, and a 1 1/4" focuser for $10, and kept my expectations low. I don't understand how "surplus" can be back-ordered, but a delay in getting the focuser caused me to wait two weeks for my order. Meanwhile, while on the prowl at the U Property Distribution center, looking for a cheap microscope for a customer in Idaho, I bought (for myself) a Zeiss stereo microscope for $100. The binocular head on it has a striking family resemblance with the Tele-Vue Bino-Vue as described in the Sept. 2002 S&T, and costing $1,050. When the objective and focuser arrived, I invested another $8 in 3" black plastic pipe and fittings at Home Depot, and $2 for black felt at Michael's, for a total of $50. I already had a star diagonal and eyepieces, and used some CDs for the glare stops. I've cobbled together a couple of small refractors before, but this is actually the first one with a real focuser, rather than just a "push-pull" on the eyepiece, so I'm quite the neophyte ATM. Recent cloudiness has prevented much evaluation of the lens, but "star" testing on tiny Christmas lights at about 150 yards shows spherical aberration. I know some of you (Chuck?) are good at, and seem to enjoy, optical evaluation, so if there is any interest is learning what you get for $30, let's meet. And this is where I can use some help. Over the Thanksgiving holidays, I machined a brass 1 1/4" adapter to allow use of the 45 degree angled bino-head. Initial use with microscope eyepieces showed promise, so yesterday I machined 2 adapters to allow use of 1 1/4" eyepieces. I have an eclectic collection of eyepieces, most of which are 50 years old and came with the 1954 Cave, so I don't know how eyepieces with wider views and/or greater eye relief (I wear glasses) will work in this possibly vignetted RubeGoldbergScope. Does anyone with a more recent collection of eyepieces care to help me make a selection? And perhaps try the bino-viewer on a better scope (it takes a lot of inward focus movement). Buying pairs of eyepieces can quickly blow my budget, so I may initially have to settle for only one focal length, too. The $50 Orion Expanse (66 degree) sound attractive at this point, but I'd hate to throw away $100. I could make 2 more telescopes for that money! ;-) Thanks, Bob Grant 273-0369
Bob, I have some lenses if you are willing to turn the housings on the lathe. Might even have some PVC chunks to use for them. The least expensive way to outfit a bino-viewer. I broke my right hand nine days ago and had surgery to install tiny steel screws. Won't have the use of the hand for a few more weeks. I'm envious of your atm industry! Send me your address off-line and I'll drop the lenses in the mail. Think I have 2 focal lengths/designs. One is a 22mm Plossl (symm.) and the other is a 10mm 3-element design using modern glass. I've made several small refractors, some more sucessful than others. All were fun to design, build, and use. C. __________________________________ Do you Yahoo!? Free Pop-Up Blocker - Get it now http://companion.yahoo.com/
Chuck - Thanks for the lenses! I machined the housings for the 22mm eyepieces tonight using the PVC chunks. By turning the barrels to fit the .912" microscope standard, I was able to reduce the weight (the bino head is already pretty heavy), and shortening the length of the light path projection out of the bino head might make it easier to use on other scopes. The two eyepieces work very well in my scope! I don't know if the supplementary lenses within the bino head cause any magnification multiplier factor, but if not, 22mm should give a 41x image. What a wonderful view of the Moon with two eyes! The air was noticeably calmer tonight than last night, so when I aimed it at the Orion nebula, I could make out 3 of the Trapezium stars. (I got the same result with my 1 1/4" 22mm eyepiece, used conventionally thru the star diagonal. But with my 16mm, 56x, I was able to see all 4 stars.) I think I will benefit from some eyecups to shield the moonlight, and an astigmatism in my left eye prevents it from coming to a true focus without my glasses. As an additional bonus, these two eyepieces give a better view in my microscope, too, than the original ones do. This is my first real refractor. Boy, it's nice to be able to observe while sitting down. I probably won't be able to make the 10mm eyepieces for a couple days. Do they go together with the convex surfaces facing each other, like the symmetrical ones? I am very pleased. This is turning into one of my most successful projects. Bob Grant ----- Original Message ----- From: "Chuck Hards" <chuckhards@yahoo.com> To: "Utah Astronomy" <utah-astronomy@mailman.xmission.com> Sent: Monday, December 01, 2003 11:09 PM Subject: Re: [Utah-astronomy] My $50 refractor, and a request for assistance
Bob, I have some lenses if you are willing to turn the housings on the lathe. Might even have some PVC chunks to use for them. The least expensive way to outfit a bino-viewer. I broke my right hand nine days ago and had surgery to install tiny steel screws. Won't have the use of the hand for a few more weeks. I'm envious of your atm industry! Send me your address off-line and I'll drop the lenses in the mail. Think I have 2 focal lengths/designs. One is a 22mm Plossl (symm.) and the other is a 10mm 3-element design using modern glass.
I've made several small refractors, some more sucessful than others. All were fun to design, build, and use.
C.
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--- Marilyn Smith <bob-marilyn@worldnet.att.net> wrote:
Do they go together with the convex surfaces facing each other, like the symmetrical ones?
Hi Bob: Yes, the convex surfaces face each other. I think that the doublet is supposed to be closest to the eye. Great report, glad I could help. C. __________________________________ Do you Yahoo!? Free Pop-Up Blocker - Get it now http://companion.yahoo.com/
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