Norm Folkers
journeyman
Reged: 03/26/08
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Re: Post your home made scope
[Re: droid]
#5673637 - 02/11/13 08:49 AM
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This is really an OTA and an equatorial mount merged together to allow observing at a fixed position.
The top of the "Y" fitting and the "T" fitting just below the eyepiece is the polar axis. It has a threaded bearing between these two fittings. A torq tube runs from this "T" fitting through the "Y" fitting and comes out to support a counterweight made from barbell weights. This is effectively the Dec axis counterweight.
The OTA begins at the eyepiece and proceeds a short distance to a small diagonal mirror that intercepts the light cone coming from a larger diagonal located inside the second "T" fitting. In between these two "T" fittings is the Dec axis bearing, again made from standard ABS fittings, just not tightened to the point where it would bind. The maximum rotation of this bearing (thread) is 180 deg so it changes the focal plane position position by 1/2 the distance from thread to the next. This happens only when moving from one object to the next when they are at different DECs. Next is the upper "T" fitting, it has the larger of the two diagonals installed inside. In my case it is a 4" (minor axis) to allow the maximum sized objective. The end of the "T" opposite the objective is simply a counterweight to balance the upper half of the OTA. This upper T has a threaded fitting that allows different sections of the upper OTA to be screwed into it. This allows having different sized and FL objectives to be screwed into it. The lenght of this part of the OTA is custom cut to allow the objective to place it's focal plane in the right position to allow an eyepiece to magnify the image formed there.
Those are the essentials. I believe Zeiss sold a similar design in the early 1960ies for over $18,000.00. Mine cost considerably less. 
This configuration allows sitting down as well as enclosing part of the scope in an enclosure to increase observing comfort.
It works for me.
Norm Folkers
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Dick Jacobson
scholastic sledgehammer
Reged: 12/22/06
Loc: Plymouth, Minnesota, USA
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Re: Post your home made scope
[Re: Norm Folkers]
#5673735 - 02/11/13 10:08 AM
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Very nicely done, Norm! Many years ago I became fascinated with the idea of a scope with a fixed eyepiece position. I put an 80mm refractor inside a 4" PVC pipe, with a pair of elliptical diagonals in front of the objective arranged so they would rotate and point anywhere in the sky. The refractor pointed down the polar axis. I got the contraption to work, but ran into an unexpected problem. It was nearly impossible to find anything with it since you couldn't sight along the tube (the tiny stub of a tube was way at the bottom near the ground). I tried to build a finder arrangement but it got hopelessly complicated. I called it my "Alphorn telescope".
Here is a link to an awesome, fully enclosed fixed position telescope built by a friend of mine. He is currently working on a larger version. See Tardis Telescope.
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gpelf
super member
Reged: 12/28/11
Loc: Kentucky
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Re: Post your home made scope
[Re: Dick Jacobson]
#5673752 - 02/11/13 10:12 AM
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That is just to "Cool", Anyone got a Extra porta-pottie 
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Norm Folkers
journeyman
Reged: 03/26/08
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Re: Post your home made scope
[Re: Dick Jacobson]
#5673924 - 02/11/13 11:57 AM
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Hi Dick,
I've seen that scope several times, once, I believe on the cover of a ATM magazine. It is an inspiration. I particularly like the idea of a warm bug free enclosure.
I solved my finder problem by using a green laser attached to the upper part of the OTA. I'm going to change that to be attached to the upper part of the outer "T" fitting. This will mean it does not have to be changed over to the alternate upper OTA each time. It will of course need some re-allignment with each switch. As with all thing ATM, the scope is never really "finished"; nor should it be.
If I could find a source for 6" ABS fittings I would consider building a larger one for use with a 6" objective. That would be an extra half magnitude or 44% more photons that a 5" can deliver. (Aperture rules!)
I hope it gives people ideas and can take this design to the next level, say with a clock drive good enough for visual use. Astrophotography would be the ultimate goal. But then I would not need to sit there at the eyepiece. But we already have lots of good designs that do that. This is for old style photons hitting the retina.
Clear skies... or cloudy, for us ATMers it does not matter that muck ;-)
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Norm Meyer
super member
Reged: 02/08/09
Loc: Warren, ME 04864
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Re: Post your home made scope
[Re: Norm Folkers]
#5674220 - 02/11/13 03:18 PM Attachment (87 downloads)
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Here is a picture of my largest scope to date. It's a 10" f5.3 one of my better mirrors I made. The mount is a knock
off of a commercially made mount. The base ring and 10"
setting circles are aluminum valve hand wheels I bought as scrap from work. Most of the parts are aluminum except
for the shafts which are drill rod, and the bearings which
are steel of course.
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Pinbout
Post Laureate
Reged: 02/22/10
Loc: Montclair
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Re: Post your home made scope
[Re: Norm Meyer]
#5674222 - 02/11/13 03:20 PM
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what size shafts are you using?
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Norm Meyer
super member
Reged: 02/08/09
Loc: Warren, ME 04864
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Re: Post your home made scope
[Re: Norm Meyer]
#5674224 - 02/11/13 03:20 PM Attachment (60 downloads)
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Here's a better shot of the base.
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rembert
journeyman
Reged: 11/23/09
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Re: Post your home made scope
[Re: Norm Meyer]
#5675439 - 02/12/13 09:25 AM Attachment (66 downloads)
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Here's my 9 inch F1800 mm refractor. After some fiddling with the distance between the two elements it performs well.
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BDC1974
member
Reged: 03/09/12
Loc: Miami, FL
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Re: Post your home made scope
[Re: Ed D]
#5675481 - 02/12/13 09:49 AM Attachment (50 downloads)
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This is my 'Little Dipper' project, about one week into making sawdust. The composite pic shows the primary end and my method of mirror attachment, as well as the 'tube' next to me for scale. I just lightly pressed together the poles and parts to see how it was coming along. Oh, in case you're wondering, it's going to be a 6" f/8 using the old Synta mirror from Mighty Mouse, pictured in my avatar.
Thanks to my friend Brian for inspiring me to build this scope. I'm really enjoying the project.
Ed D
Looking good Ed! Can't wait to give her a try on the next Everglades trip.
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droid
rocketman
Reged: 08/29/04
Loc: Conneaut, Ohio
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Re: Post your home made scope
[Re: rembert]
#5675482 - 02/12/13 09:50 AM
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9 inches, wow......f/5 or so???
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BDC1974
member
Reged: 03/09/12
Loc: Miami, FL
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Re: Post your home made scope
[Re: BDC1974]
#5675483 - 02/12/13 09:52 AM
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That's my baby which was coincidentally 9 months in the making. No previous wood working experience. Thanks to Ed for helping me work out secondary alignment issues.
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droid
rocketman
Reged: 08/29/04
Loc: Conneaut, Ohio
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Re: Post your home made scope
[Re: BDC1974]
#5675498 - 02/12/13 10:00 AM
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Beautiful, if she works as good as she looks....wow
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rembert
journeyman
Reged: 11/23/09
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Re: Post your home made scope
[Re: droid]
#5675514 - 02/12/13 10:10 AM
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No, slightly less than F/8, 1800 mm to be exact. Max. usable magnification is about 400-500 x, with a Fringe-killer.
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Don M
super member
Reged: 10/12/08
Loc: Roseau, Minnesota
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Re: Post your home made scope
[Re: droid]
#5675901 - 02/12/13 01:49 PM
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Hi - What a great place to hang out!! I really enjoy the science, engineering, humor, and a bit of philosophy from all over the world
- while having a cup of coffee!! I am old enough to view 'how we do this', as 'science fiction!' However, I am still searching for a
reliable antidote against aperture fever!! - binoculars, small scopes, medium scopes, finance, portable scopes, staying off the computer
- the tug is still there!!  Here are a couple of my ATM projects. I know that some of these photos are on other threads. 
CN Rocks! Don M (StarRocker)
The white scope is a 10 inch f/5.6
On my way to a school 'Star Party!'
10 inch f/4.5
Please don't 'bump me' lights!
'Look Mom - no tools!'
'Tough astronomer'(not me!) - that is snow in the back ground!
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mikey cee
Postmaster
Reged: 01/18/07
Loc: bellevue ne.
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Re: Post your home made scope
[Re: rembert]
#5675919 - 02/12/13 01:57 PM
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No, slightly less than F/8, 1800 mm to be exact. Max. usable magnification is about 400-500 x, with a Fringe-killer.
Who's lens did you use and is it coated?  Mike
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herrointment
Carpal Tunnel
Reged: 03/12/11
Loc: North of Hwy. 64
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Re: Post your home made scope
[Re: mikey cee]
#5676289 - 02/12/13 05:01 PM
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Don, your 10 inch F4.5 is my favorite ATM scope ever!
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rembert
journeyman
Reged: 11/23/09
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Re: Post your home made scope
[Re: mikey cee]
#5676317 - 02/12/13 05:16 PM Attachment (46 downloads)
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It's nicely coated. It's from Barride Optics. Here another photo from the lens in the scope, taken while I was testing it and was still without proper internal flocking and baffling.
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rembert
journeyman
Reged: 11/23/09
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Re: Post your home made scope
[Re: Don M]
#5676328 - 02/12/13 05:25 PM
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A reliable antidote against aperture fever is using a big scope under a light polluted sky. Also avoid acclimatisation of the thing al all costs.
But , that said, your ATM-work is impressive!!
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tim53
Postmaster
Reged: 12/17/04
Loc: Highland Park, CA
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Re: Post your home made scope
[Re: rembert]
#5676411 - 02/12/13 06:41 PM
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My 12.5" f/23 Classical Cassegrain when it was on my Springfield mount a while or two back. Fred Ley pic (I don't have any of my own for some reason!). I've since reconfigged the scope to a straight through Cassegrain and put it on my EM-500 mount.
-Tim.
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Pinbout
Post Laureate
Reged: 02/22/10
Loc: Montclair
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Re: Post your home made scope
[Re: Don M]
#5676623 - 02/12/13 09:28 PM
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Quote:
On my way to a school 'Star Party!'
Hey Don,
the only thing wrong with the trailer/scope is it's not hook up to a goldwing, instead of a vehicle with 4 wheels. 
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