John Jarosz
I'm being watched...
Reged: 04/25/04
Posts: 2193
Loc: Chicago area, IL
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Does anyone use a curved secondary support like I have drawn? I'm wondering how suseptible it is to vibration, how long it takes the vibrations to damp out, etc. Any thoughts on this design are welcome.
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6" F4.6(w/Paracorr) GEM reflector, 8" F11 Dall Relay Scope
6" F5 RFT Refractor, Garrett Gemini 20x80 LW
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MMICKELS
Aluminum Knight
Reged: 01/20/04
Posts: 25192
Loc: The Land of Shake and Bake
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Protostar is selling a similar spider. I haven't heard anything bad about it. Theirs is more of a half circle than the "U" shape you have drawn though.
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Mark
"The only thing wrong with immortality is that it tends to go on forever."
Herb Caen
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John Jarosz
I'm being watched...
Reged: 04/25/04
Posts: 2193
Loc: Chicago area, IL
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Yeah, Thanks. I'm thinking about using this type design. I just have a feeling that the mirror may vibrate for a short time after the tube is bumped, or after you adjust focus. I like the physical design, I'm just concerned about vibration. The Protostar website says it's usable up to fairly large tubes (15" dia), but I'd like to hear from anyone that has actually used this.
John
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6" F4.6(w/Paracorr) GEM reflector, 8" F11 Dall Relay Scope
6" F5 RFT Refractor, Garrett Gemini 20x80 LW
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erik
telescope surgeon
Reged: 01/30/04
Posts: 24019
Loc: Hawaii 19 N lat -155 Long.
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i've had some vibration problems even in my 3 vane curved spider. in fact, hans from 1800destiny is sending me thicker 1/8" vanes for that reason. i can't imagine the protostar vanes NOT having vibration problems with a heavy secondary. have you seen the curved vane design that orion optics uses on a couple of their newts? it's a design with two circular vanes, one on each side of the secondary mount. i would think that something like that would offer the best balance between stability and the least overall diffraction. i don't know if anyone sells that type of spider aftermarket, but for a big heavy secondary, that design or the thick destiny spider would probably be the most vibration free...
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-Erik Wilcox
Homebuilt 16" Truss Dob
SV 80mm ED Nighthawk NG on M1 ALT/AZ
Nikon Prostaff 65mm spotter on Trekpod
Konusvue 20x80 binos/Peterson pipemount
Orion 10x50 binos
Homebuilt 80mm f/5 refractor
Mirador 60mm f/12 1960's refractor
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Tom L
Reged: 01/07/04
Posts: 29817
Loc: Sunny Oregon
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Brian actually talks about damping time with his curved spider design, and one of the reasons he does not recommend it above 15" I.D. of your tube. Call Brian at Protostar. He will take your call.
I am 50% curved, 50% 3-vane for my final spider design. either way it will be from Protostar.
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Tom 
Tele Vue 102mm f/8.6 on an EzTouch
Vixen 80mm f/5 A80SSWT on a grab-n-go mount
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John Jarosz
I'm being watched...
Reged: 04/25/04
Posts: 2193
Loc: Chicago area, IL
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Well, I doubt he'd take my call as I was going to build it myself and he'd realize I was just picking his brain....... Well, he'd take my call, then there would be the awkward silence when he'd realize what I was doing...........
John
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6" F4.6(w/Paracorr) GEM reflector, 8" F11 Dall Relay Scope
6" F5 RFT Refractor, Garrett Gemini 20x80 LW
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MMICKELS
Aluminum Knight
Reged: 01/20/04
Posts: 25192
Loc: The Land of Shake and Bake
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John, you might be suprised. Brian is a stand up guy who will help regardless IMHO. I think if you make the vanes higher it would help. (so if the vanes are 1/32 x 1" or 1 1/4")
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Mark
"The only thing wrong with immortality is that it tends to go on forever."
Herb Caen
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John Jarosz
I'm being watched...
Reged: 04/25/04
Posts: 2193
Loc: Chicago area, IL
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Mark, what do mean "make the vanes higher" ?
John
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6" F4.6(w/Paracorr) GEM reflector, 8" F11 Dall Relay Scope
6" F5 RFT Refractor, Garrett Gemini 20x80 LW
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Tom L
Reged: 01/07/04
Posts: 29817
Loc: Sunny Oregon
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Hmmm. that reaction never entered my mind. Most astro folks are more than willing to help an ATM'er.
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Tom
Tele Vue 102mm f/8.6 on an EzTouch
Vixen 80mm f/5 A80SSWT on a grab-n-go mount
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Anonymous
Unregistered
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Erik,
Are those vibration problems on the 8" or the 15"? I've been thinking of using this spider and am curious whether the 1/16" vanes would be sufficiently stable for a 10".
Thanks,
Doug
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MMICKELS
Aluminum Knight
Reged: 01/20/04
Posts: 25192
Loc: The Land of Shake and Bake
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Quote:
Mark, what do mean "make the vanes higher" ?
John
John I mean wider, but not thicker. So a 1/32 thick vane that is 1" wide vane would be more stable than the same thickness at 3/4".
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Mark
"The only thing wrong with immortality is that it tends to go on forever."
Herb Caen
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gazerjim
Postmaster
Reged: 02/12/04
Posts: 7728
Loc: About where I thought I was......
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I've talked with Bryan at Protostar a couple of times and found him to be indeed a stand up kind of guy who takes a genuine interest in mechanical and optical excellence. IMHO his secondary mounts are by far the best designs available.
You might also check out Royce's spider design at http://www.rfroyce.com/spidrunq.htm
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Jim Fisher
If you're not part of the solution, you're part of the precipitate.
Henry J. Tillman
Edited by gazerjim (01/12/05 05:06 AM)
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Brian Reed
Vendor (Round Table Platforms)
Reged: 10/29/04
Posts: 376
Loc: North East Illinois
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Here is a spider I made from some 11/4" wide pallet banding. I highly recommend this material. It is very ridged once anchored and is only .039 thick. It supports a 2.1 inch secondary inside a 12" tube. Vibration dampens out in about 1 second, the same as a three-vane spider I used to have.
If you have good smooth motion in your scope, vibration should not be any problem. This area is often overlooked.
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Brian
10-F5.6
8-F7
http://www.roundtableplatforms.com
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John Jarosz
I'm being watched...
Reged: 04/25/04
Posts: 2193
Loc: Chicago area, IL
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I'm thinking you're right. The support is now made from 1" x .020 spring stock material. The vibration characteristics will probably be improved by going to .040 thick or so.. If your .039 material works in a 12", then I should have no problems in a 6". The whole scope is going to get dismantled so I can do some paint, tube flocking, etc. I'll make the change then. But I'm only going to do that after I can star test the whole thing. If I believe the forecasters were going to get some clear skies in 2006, so I may have to wait awhile.
Thanks for your thoughts.
John
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6" F4.6(w/Paracorr) GEM reflector, 8" F11 Dall Relay Scope
6" F5 RFT Refractor, Garrett Gemini 20x80 LW
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erik
telescope surgeon
Reged: 01/30/04
Posts: 24019
Loc: Hawaii 19 N lat -155 Long.
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Quote:
Erik,
Are those vibration problems on the 8" or the 15"? I've been thinking of using this spider and am curious whether the 1/16" vanes would be sufficiently stable for a 10".
Thanks,
Doug
the spider works exceptionally well with the 8". it's the 16" that has a vibration due to the 1/16" vanes. with the 10", i don't think you'll have any problems, and if you did, hans from 1800destiny is a great guy, and he'll help with it. you may want to PM jeff (ACE). he has a destiny spider in his xt10. i think he's pretty happy with it. as long as there's tension against the vanes, i don't think you'll have a problem. just make sure that the I.D. measurements are perfect when you order, so that he ships you the right size. i think part of the problem with my 16", is that he shipped me one that was slightly undersized (i did give him the correct measurement though, 18" I.D.), so there's not enough tension against the vanes. it slides easily inside the 16" ota, while the 8" had to be compressed a bit to fit. so i asked hans to ship me thicker vanes that are 1/2" longer, and he's working on that now. i guess with a big scope, there are more issues, but like i said, he's an easy guy to work with, so i don't think you'll have any problems with the 10"... 
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-Erik Wilcox
Homebuilt 16" Truss Dob
SV 80mm ED Nighthawk NG on M1 ALT/AZ
Nikon Prostaff 65mm spotter on Trekpod
Konusvue 20x80 binos/Peterson pipemount
Orion 10x50 binos
Homebuilt 80mm f/5 refractor
Mirador 60mm f/12 1960's refractor
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Anonymous
Unregistered
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Thanks Erik! This is great info, I didn't realized you had two of them! This is the best looking solution so far particularly given the constraints imposed by my short cage. BTW, how do you like the adjustment method on the destinys? I just realized I'm not even sure how that works on this spider... allen wrench screws like the protostars?
Congrats on the 16mmT5 BTW (saw your other post) It's one of my fav's
Doug
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Jeff Morgan
Carpal Tunnel
Reged: 09/28/03
Posts: 1532
Loc: Prescott, AZ
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Quote:
You might also check out Royce's spider design at http://www.rfroyce.com/spidrunq.htm
That looks tempting, cheap, and easily reversible. Think I will put it in the project queue.
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Jeff Morgan
Prescott, AZ
Wile E. Coyote School of Telescope Making
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erik
telescope surgeon
Reged: 01/30/04
Posts: 24019
Loc: Hawaii 19 N lat -155 Long.
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Quote:
Thanks Erik! This is great info, I didn't realized you had two of them! This is the best looking solution so far particularly given the constraints imposed by my short cage. BTW, how do you like the adjustment method on the destinys? I just realized I'm not even sure how that works on this spider... allen wrench screws like the protostars?
Congrats on the 16mmT5 BTW (saw your other post) It's one of my fav's
Doug
thanks doug! hopefully, i'm going to get out to a dark site on friday night to test the nag out. as far as the destiny spider adjustment, they have 3 phillips head screws and a center bolt with a tension spring adjustment. i like the way it works, it's really easy to do while looking in the eyepiece, unlike some other spiders i've seen. good luck with your project!
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-Erik Wilcox
Homebuilt 16" Truss Dob
SV 80mm ED Nighthawk NG on M1 ALT/AZ
Nikon Prostaff 65mm spotter on Trekpod
Konusvue 20x80 binos/Peterson pipemount
Orion 10x50 binos
Homebuilt 80mm f/5 refractor
Mirador 60mm f/12 1960's refractor
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Anonymous
Unregistered
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Quote:
hopefully, i'm going to get out to a dark site on friday night to test the nag out.
Hope the weather clears up!
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erik
telescope surgeon
Reged: 01/30/04
Posts: 24019
Loc: Hawaii 19 N lat -155 Long.
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me too! it was originally supposed to be clear, but it's not looking so good now. maybe coyote lake is far enough south that it'll be clear...
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-Erik Wilcox
Homebuilt 16" Truss Dob
SV 80mm ED Nighthawk NG on M1 ALT/AZ
Nikon Prostaff 65mm spotter on Trekpod
Konusvue 20x80 binos/Peterson pipemount
Orion 10x50 binos
Homebuilt 80mm f/5 refractor
Mirador 60mm f/12 1960's refractor
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