gregj888
sage
Reged: 03/26/06
Posts: 212
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Rob, the Houghton was a fun project.
It's been around a while. It won an award at Table Mt. in 1996. As near as I can tell it was either the first or second to see star light (and I suspect second, OSP Aug. 1995). I haven't used it as much as I would like (work, family et. al).
Lenses are 3/4" BK-7 and still need AR coating. There is a little bit of astigmatism that I need to get to the bottom of but it's only detectable in a star test.
The tube is 10" Al irrigation pipe (~1/16" wall) and the mount is welded Al. The tube is baffled and flocked. The mount has one of Mel's controllers on it and will also take one I designed. Focuser is removable and replacable with a camera mount.
It gets an interesting response from those using it. The flat focal plane give a sensation of looking at a picture. They don't know why it looks different, but can tell it does. Stars are points to the edge, but only the astro-nuts notice that.
I would be glad to answer specific questions...
Greg
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rwiederrich
Goldfinger
Reged: 11/17/05
Posts: 6190
Loc: Bremerton Washington
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Quote:
Rob,
The design was presented by A. L. Woods in the old TM magazine. The Stellefane folks have it in their library.
Optically it's a 6" ellipse, 3.5" convex and 3.5" concave. The 3.5" mirrors are a little small for my hands and to help with edge issues I used 4" blanks for the secondary and tertiary.
The file's to big for CN-
http://www.eclipse-t.com/tri_plot.bmp
http://www.eclipse-t.com/2.bmp
Case is recycled closet door skins (3/16 ply), focuser is home brew crawford.
Optically it seems to be defraction limited but that's still under test. The close pair in double-double split cleanly with about as much space between them as the airy disks are in diameter. It's a real hit at the local star parties.
Greg
Fantastic Greg.
I'd love to look through that one fer sure...
It did look like it was made from door skins. Great use of material.
Rob 
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www.goldmtobservingcenter.com
Providing a great place for amateur astronomers, and ATM's to come and enjoy their hobby.
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rwiederrich
Goldfinger
Reged: 11/17/05
Posts: 6190
Loc: Bremerton Washington
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Quote:
Rob, the Houghton was a fun project.
It's been around a while. It won an award at Table Mt. in 1996. As near as I can tell it was either the first or second to see star light (and I suspect second, OSP Aug. 1995). I haven't used it as much as I would like (work, family et. al).
Lenses are 3/4" BK-7 and still need AR coating. There is a little bit of astigmatism that I need to get to the bottom of but it's only detectable in a star test.
The tube is 10" Al irrigation pipe (~1/16" wall) and the mount is welded Al. The tube is baffled and flocked. The mount has one of Mel's controllers on it and will also take one I designed. Focuser is removable and replacable with a camera mount.
It gets an interesting response from those using it. The flat focal plane give a sensation of looking at a picture. They don't know why it looks different, but can tell it does. Stars are points to the edge, but only the astro-nuts notice that.
I would be glad to answer specific questions...
Greg
Greg, first did you go to TMSP this year?
Next, Do you have some drawings of the design.
And building techniques?
I don't mean to appear ignorant, but what is the actual difference with this design?
Rob 
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www.goldmtobservingcenter.com
Providing a great place for amateur astronomers, and ATM's to come and enjoy their hobby.
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rsvignesh
super member
Reged: 05/04/06
Posts: 119
Loc: Nashua, NH
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Jason,
I am intrigued how did you make the stand your sphere rides on? Can you give me some tips. I posted a separate question for this in this forum. So, maybe you can reply there as I do not want to hijack this thread.
Everyone, cool scopes out here. I admire your work.
Vignesh
Quote:
And here it is on my adapter I fitted on top of a Meade field tripod...
I got a new ball and I used some fleck paint inspired by Ron Ravneberg (hey Ron!! good to see you here on cloudynights!)
Jason
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gregj888
sage
Reged: 03/26/06
Posts: 212
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Rob, I had planned to go to Table but didn't make it, work got in the way. I'm in Portland, Bremmerton isn't to far. The guys in the Seattle club built several Tri's to this design in the 90s.
I have the L-Houghton design buried on an old drive somewhere. It's pretty close the the Rutten/Van Venrooij design. The Lurie uses matched curves on the 2 lens set (double concave and double convex) for easy construction; each lens acts as the tool for the other. You can adjust final SA with lens separation. Think of it as a Schmidt Newtonian with a doublet lens instead of the Schmidt corrector. It also out performs the SN by a large factor (much smaller spot sizes @ 1/5 or better and no coma)
The lens is zero power but produces SA equal and opposite that of the spherical primary, thus canceling it out. Since the primary is a sphere (no axis) there is no coma but some residual astigmatism (with my normal caveat- "if properly made"). The design (caveat) give a 1" diffraction limited focal area and film resolution over 2" dia. The focal plane is for all intents is flat.
The design scales well. I wouldn't be afraid to try a 20" as far as construction. I wouldn't go beyond 10" to 12" for other reasons (better designs for the material budget) unless there was a real specific need. IMHO a CAT beyond 14" to 16" needs a special purpose.
Greg
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Chuck Fellows
sage
Reged: 08/21/05
Posts: 450
Loc: Cave Creek, Arizona
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Quote:
Chuck
Made them, blanks came from Newport. BTW, BK-7 is easy and fast to work. You can save a lot of cash by ordering the blanks "plano-plano fine ground" as you work all 4 sides anyway.
Greg
Greg, I don't understand the term plano-plano. Were the blanks fine ground to radius on all 4 sides?
Thx...
Chuck
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16" Truss DOB Swayze Mirror
7.1" Custom Mak Newt
Tools, Lots and Lots of Tools!
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gregj888
sage
Reged: 03/26/06
Posts: 212
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Chuck,
They are just coursely ground flat on both sides. Since there is no finishing (fine grinding and polishing to spec.) the blanks are a lot cheaper. They are just plane blanks without curves; that's just the lingo to specify it.
Greg
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dawsonian2000
member
Reged: 07/26/06
Posts: 78
Loc: Riverview, FL, USA
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10" f/5.6 Fork Mounted Newtonian Reflector. Check out its step-by-step construction process at http://www.vega-sky-center.com/index_sao.html . I will be finishing and uploading the final pages of its construction process to our website soon.
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Clear Skies, Forever!
Mel Dawson
The Vega Sky Center
10" (250mm) F/5.65 Fork Mounted Newtonian Reflector
3.5" (90mm) F/11.1 "Vixen-Spec Modified" Konus GEM Refractor
3.1" (80mm) F/6 Super ED APO Triplet Refractor
4.5" (114mm) F/8 Cosmos (Grampus) GEM Newtonian
2.4" (60mm) F/16.7 Tasco 7te-5 Refractor
2.4" (60mm) F/15 Jason Discoverer 313 Refractor
http://www.vega-sky-center.com
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Chriske
Kijkerbouw Urania
Reged: 08/15/04
Posts: 2027
Loc: Boechout, Belgium
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Chris
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Ed Jones
Pooh-Bah
Reged: 04/06/04
Posts: 1098
Loc: Sin-sin-atti
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Nothing beats observing from a nice warm location especially since it will down in the single digits in the next couple of nights so.
Flat fed 10 inch Herschellian with an indoor eyepiece location.
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Ed Jones
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waynet
professor emeritus
Reged: 04/20/05
Posts: 632
Loc: Oklahoma, USA
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Hi Ed,
This is a brilliant design. Do you have any trouble with condensation on the optics, or with the wide range of temperatures along the scope?
wayne
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Chriske
Kijkerbouw Urania
Reged: 08/15/04
Posts: 2027
Loc: Boechout, Belgium
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Ed, is this the same setup as Oscar Knabs' scope. I think he made about the same scope a few decades ago.
Nice scope btw, but if it were mine, I would add a coffeetabel somewhere nearby the eyepiece to make observing even more enjoyable.. 
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Chris
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eric moerman
super member
Reged: 11/08/03
Posts: 236
Loc: belgium
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12,5"F7 newton
Edited by eric moerman (02/04/07 06:14 AM)
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Chriske
Kijkerbouw Urania
Reged: 08/15/04
Posts: 2027
Loc: Boechout, Belgium
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No vibrationproblems with a Newt that long in a forkmount Eric..?
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Chris
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eric moerman
super member
Reged: 11/08/03
Posts: 236
Loc: belgium
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Hi Chris,
just a litle bith but i know where it comes from,i just need to fix it 
The biggest problem i have now is the tube flexing at the connection points.Its already a litle bith old the tube so it became a litle "sloppy".
im bussy rebuilding a tube ad will be more carefull to these points.
Second problem is that the round disc where the fork arms atached to and the base plate are still flexing a litle bith because of the weight.
The problem is from the bearing that is inside the base plate,i will replace it with a conical bearing and also the one on the other end of the polar axel so i can take tha play away.
Buth im already pretty happy the way it is now,i can easely use high mag.and focus it,yesterday we even used it to make some webcam images and it worked pretty good.
Its first time i build a real mount so im stil learning.
eric
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Anonymous
Unregistered
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Quote:
Oscar Knabs' scope
I don't mean to hijack, if that's what I am doing, but I would love to see more detail on Ed's indoor/outdoor scope, and this Knab scope that was referenced.
It is -20 where I live this morning.
Thanks
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Ed Jones
Pooh-Bah
Reged: 04/06/04
Posts: 1098
Loc: Sin-sin-atti
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Wayne,
The primary is in a closed box in the yard in the yard and I sometimes got condensation from being closed. I've run electric out to it now to run some resistors on the mirror to stop that. I don't have a problem with dew until I take the optics inside and forget to cover them.
Chris,
Well I use a flat and so did Oscar knab but that's the only similarity. His was a refractor and mine is a corrected Herschelian with no OTA. Here is more info on it: http://home.isoc.net/%7Eejones/
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Ed Jones
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Art Bianconi
Post Laureate
Reged: 03/06/06
Posts: 4659
Loc: Delaware River Valley, New Jer...
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Chris, what Eric didn't say was that the fork is all metal sheet and was completely glued up using industrial adhesives!
As I recall he was going to fill the fork with low density closed cell foam to strengthen it and dampen vibrations.
Erik kept CN fans abreast of it's construction with a highly detailed and much appreciated string. It's back there somewhere.
Art
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Chriske
Kijkerbouw Urania
Reged: 08/15/04
Posts: 2027
Loc: Boechout, Belgium
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Quote:
Chris, what Eric didn't say was that the fork is all metal sheet and was completely glued up using industrial adhesives!
As I recall he was going to fill the fork with low density closed cell foam to strengthen it and dampen vibrations.
Erik kept CN fans abreast of it's construction with a highly detailed and much appreciated string. It's back there somewhere.
Art
I know.
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Chris
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Chriske
Kijkerbouw Urania
Reged: 08/15/04
Posts: 2027
Loc: Boechout, Belgium
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Quote:
Quote:
Oscar Knabs' scope
I don't mean to hijack, if that's what I am doing, but I would love to see more detail on Ed's indoor/outdoor scope, and this Knab scope that was referenced.
Thanks
Me to, how about it Ed.... 
Could you open a new thread on your 'indoorscope'..?
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Chris
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