jmoore
Carpal Tunnel
Reged: 10/01/03
Posts: 1959
Loc: Beaufort, NC
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I've selected a design! Mine will look something like this in the end. I mean, colors will be diff't, and probably the Dob mount will differ, but as far as the general scope design, this is what I'm going with.
A tube would look cooler than the box, but the box will be much easier for me to design/build, a materials (plywood) will probably be cheaper, and in the end, the scope will look that much funkier, which is good by me.
To refresh your memory, this will be a 150mm f/15 scope. It will use one elliptical mirror to fold the light path roughly in half, and the 2" diagonal will serve as the second mirror.
cheers,
jeff
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Hardin 12"
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jmoore
Carpal Tunnel
Reged: 10/01/03
Posts: 1959
Loc: Beaufort, NC
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Here's the initial blueprint. This doesn't show the 2" diagonal at top. Credit to a friend of mine who drafted the design.
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Tom L
Reged: 01/07/04
Posts: 29817
Loc: Sunny Oregon
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Excellent! Can't wait to watch this baby unfold! (pun intended  )
Jeff, please edit your initial image and keep the image size to 800x600. Also, we try to keep file size around 60K-100K.
This is a flat mirror? Where will you get it?
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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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rboe
Numbfinger
Reged: 03/16/02
Posts: 39760
Loc: Phx, AZ
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Hmmm, if you made the back part straight vs. slanted like a fast back you could make room for a bit of storage - put your finder gear in there while in storage. Have fewer angles to cut too.
I'm not a big fan of folded optics but I'm very intrigued by them.
F15, wow! Wide angle eye pieces would be a bit of a waste there! Ortho's would be killers though.
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Ron
NS11GPS
Pronto
16" dob
15X70 Obies
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jack savard
sage
Reged: 05/26/04
Posts: 476
Loc: quebec canada
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( 150mm f/15 scope. )
where do you find this kind of lens ,at what price,it shoud be expensive;
why F=15 for planetary ,I suppused
(one elliptical mirror to fold the light )
why this kind or mirror if you used a flat this not work and what is the focal of the eliptic
(he 2" diagonal )
this is curious to me it look very large or to much large
but if you already have it it is ok but look not uptimised
can you specify the angle of both mirror for info
also maybe it is and expiriment to try
I used sometime lens from photocopier,they are ordinary lens whit flat mirror immedialy in the backand like this it work like parabolic mirror whit very wide angle of view
if you place mirror in the back of you 150mm lens and after used the technic of haft way secondary at 15 degree you have a fold but very short
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nobody made it I AM INTEREST
46,49 N 71,14 O Québec canada 2\L100 2\D100 0\S100
Edited by Tom L (01/11/05 04:23 PM)
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Jim Svetlikov
Carpal Tunnel
Reged: 10/06/03
Posts: 2033
Loc: Crescent Beach
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Wow Jeff, I'm impressed - good luck, buddy!
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It is better to build a boy than try to mend a man.
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erik
telescope surgeon
Reged: 01/30/04
Posts: 24019
Loc: Hawaii 19 N lat -155 Long.
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that'll be the talk of the star party, jeff! good luck with it! 
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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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Hey, pretty cool! I've never even seen a folded scope before - this would never have occurred to me. It just amazes how many different ways there are to build a telescope. Looks very portable & I would think great on planets. Good luck!
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jmoore
Carpal Tunnel
Reged: 10/01/03
Posts: 1959
Loc: Beaufort, NC
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thanks for the enthusiasm, all. (Tom, I hope my image is small enough now).
To answer some questions:
lens and flat mirror - already acquired a few months ago - got an amazing deal on Astromart; $550 for about $1200-$1500 worth of optics. Lens is an unused f/15 doublet, probably from D&G (would make it worth $1000) but can't confirm this, and oversized flat mirror (in perfect shape) is 1/20 wave...worth $600.
Ron, I'm amused by your storage ideas. Maybe an insulated compartment for my dinner and coffee, too.
f/15...yep...2250mm focal length. None too good for wide-fields, but no matter; this will be my planetary specialist; false color ought to be negligible at this f/ratio. 12mm and 9mm orthos ought to be right at home in it.
Sure, I'd just assume NOT have a folded scope, but then again, there's no other way to accomodate such focal length in a relatively portable REFRACTOR package. This scope will be about 4' long...similar to an 8" f/6 Newtonian. No problem! The only other way to have a relatively portable 6" refractor is to do it with an APO, but ummm, I'm not willing to spend 2 years salary for one (we grad students don't make much $$). The high-quality flat mirror ought to be invisible.
I'm gonna start making the secondary mirror holder very soon; perhaps this weekend.
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Hardin 12"
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Bill McHale
professor emeritus
Reged: 11/07/04
Posts: 573
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Sorry for jumping in so late here. Just some general thoughts.
1. There are alot of advantages to having a long focal length that most people don't consider these days.
* Simple eyepiece designs will work really well; Orthos will work great, but even Kellners or RKEs will provide excellent performance (So if you see a set of RKEs at a good price, they would probably be worth it).
* While it won't provide huge fields of view, you could pick up realtively cheap wide field eyepieces (like the Konig 40 mm that University Optics sells) and still get over a degree field of view out of it. When it comes down to it, there really are only a handful of objects in the sky that demand wider fields of view than that.
* Depth of focus will be great on this scope; it will make critical focus on planets easier.
* Chromatic abberation while not negligable will be well controlled... and later maybe you can get a Chromacorr for it.
--
Bill
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Bill
186,000 MPS, its not just a good idea, its the law.
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Tom L
Reged: 01/07/04
Posts: 29817
Loc: Sunny Oregon
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Jeff, I went searching for this thread today, wondering if you ever got it off the ground?
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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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jdownie
professor emeritus
Reged: 02/24/06
Posts: 738
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Any report?
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ATM project - a terrible waste of good Pyrex.
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AV in CMH
sage
Reged: 11/07/05
Posts: 315
Loc: Columbus Ohio
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Could something like this be of interest?
The up side is that the focuser stays in place!
Regards,
Anthony
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jdownie
professor emeritus
Reged: 02/24/06
Posts: 738
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For examples of this design, see Kelly Jons' version at Stellafane, 2005.
Folded refractor
Or Jeff Morgan's offering...
Another folded refractor
John
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ATM project - a terrible waste of good Pyrex.
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Jeff Morgan
Carpal Tunnel
Reged: 09/28/03
Posts: 1535
Loc: Prescott, AZ
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Quote:
Could something like this be of interest?
The up side is that the focuser stays in place!
Regards,
Anthony
It's been done. Yes, ergonomics are killer, and only two reflections are used, minimizing light loss and giving non-reversed images that match your star chart. It looked something like this:
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Jeff Morgan
Prescott, AZ
Wile E. Coyote School of Telescope Making
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