Gary Fuchs
scholastic sledgehammer
Reged: 05/22/06
Posts: 867
Loc: Easton, PA, USA
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John - Would these be the articles:
Volume 117 (2007)
Wise, P. & Wall, J.
- The retrofocally corrected apochromatic dialyte refracting telescope
Volume 112 (2002)
Wall, J.
- Building a 30-inch refractor
Gary
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rwiederrich
Goldfinger
Reged: 11/17/05
Posts: 8305
Loc: Bremerton Washington
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Quote:
Hi Rob,I had better clear the air, Crayfordjon is my web page alias actually I am John Wall inventor of the Crayford focuser, named for the town of my birth ( like the Springfield mounting).
Well hello John Wall..inventer of the Crayford focuser. 
Your new refractor concept looks interesting for sure.
So I can get a nice piece of float glass and grind a shallow convexed polished curve on one side(inside)leaving the outer surface flat and polished..and then figure the focal length(preferable long) insert a 50mm binoc objective in the light path and shuzam!
It sounds too simple to be even remotely possible.
Got any images of one of these set up so we can evaluate the train....?
Rob(Interested)
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www.goldmtobservingcenter.com
A great place for amateur astronomers, and ATM's to come and enjoy their hobby.
http://tech.groups.yahoo.com/group/HomemadeRefractorTelescopes/ My homemade refractor group.
www.vimeo.com/6014031
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DAVIDG
Carpal Tunnel
Reged: 12/02/04
Posts: 1985
Loc: Hockessin, De
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Here is the spot diagram from my OSLO file showing the center spot. The small black circle is the airy disk.
- Dave
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Homemade 'scopes 8"f/7,6" f/5", 6"f/4, 4.25" Schief. 60mm Coronagraph,60mm H-alpha system, 4.25" White-light Solar Newtonian,solar spectroscope, 4.5" f/16 Schupmann Medial refractor, 14 Stellafane awards 7 in optics
Engineering = Taking what you have and making what you need.
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Dick Parker
sage
Reged: 08/17/07
Posts: 247
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Dave -
I put your numbers in to my OSLO last night and got the same spots. Plus lots of coma off axis. (Thought I did something wrong.)
Dick Parker
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rwiederrich
Goldfinger
Reged: 11/17/05
Posts: 8305
Loc: Bremerton Washington
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Quote:
Here is the spot diagram from my OSLO file showing the center spot. The small black circle is the airy disk.
- Dave
Yikes!
Looks like spherical prismatisism....
I'm assuming that's not good.... 
Rob
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www.goldmtobservingcenter.com
A great place for amateur astronomers, and ATM's to come and enjoy their hobby.
http://tech.groups.yahoo.com/group/HomemadeRefractorTelescopes/ My homemade refractor group.
www.vimeo.com/6014031
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Crayfordjon
Inventor
Reged: 06/17/09
Posts: 368
Loc: UK
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Gary from John Wall. yes they are the two seminal papers I published a couple of years ago, they are the result of many years of patient on off research into dialytes and retrofocal dialytes, which resemble a Schupmann but are trictly not so, as a Schup uses a mangin mirror making it a catadioptric refractor, as my conception uses all refracting optics it more resembles an over corected terrestrial scope. The investigations finally resulted in me realising a great ambition, that is, to build a very large refractor. The objective lens is a single plano convex made from Chance Pilkinghton float glass 25mm thick which I purchased from a builders merchant, edge ground for £250 (Sterling),float glass has very good optical properties, and is BK7. Optical test with a twenty two inch mirror I was making at the time showed only one slight striation in the corner of the disc. The design was taken up by Peter Wise who refined it into the Zerochromat.
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Crayfordjon
Inventor
Reged: 06/17/09
Posts: 368
Loc: UK
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Yeah it is badly corrected as your OSLO diagrams predict, but the system is new and highly experimental, I make no claims at all that it will replace an apo objective, there is coma and colour in the system but this is an order of magnitude smaller than that for a singlet having the same aperture and F:ratio as the hypo. The coma can be corrected by redesigning the reducing lens as these tend to be comatic anyway, most of the color is lateral chromatic ab' however computor ray traces are just that, the thing is to make one and look through it!!!, you see brilliantly lit and crisp images which are slighly marred by a little color fringing, if you can put up with that then it is a very good cheap refractor for beginners. The challenge is for the ATM community to do this and develop it into a serious scope. The hypo will make a first class deep sky imager's refractor using filters, eg O111 forbidden line of oxygen. I have been using the hypo with a cheap red acrylic filter and the image definition is perfect, and very bright.
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Crayfordjon
Inventor
Reged: 06/17/09
Posts: 368
Loc: UK
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Rob ( interested),Hi, yes it is a simple plano convex, flat on one side, and curved on the side facing the object, that is, the front surface. Get hold of a bino OG 7X50, but if you can a 10X60 and stick it half way down the tube on a test stand, it would be helpful to use a flat to fold the long focal length in half, this need not be 20th wave,but commercial grade 6 waves will do nicely. The back focus will now be slightly less than the f/l of the bino OG. It is as simple as that. John.
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Crayfordjon
Inventor
Reged: 06/17/09
Posts: 368
Loc: UK
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I have two optical line diagrams of the system which I have been trying to send since I opened the thread but they are being sytematically rejected ( yes I have compressed them), sorry about that folks John Wall.
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Crayfordjon
Inventor
Reged: 06/17/09
Posts: 368
Loc: UK
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diagram of the Hypochromat.
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Crayfordjon
Inventor
Reged: 06/17/09
Posts: 368
Loc: UK
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Diagram showing the comparison of disoersions of the Hypo against a singlet lens of the same focal ratio.
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Crayfordjon
Inventor
Reged: 06/17/09
Posts: 368
Loc: UK
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This is an image of a television antenna at a distance of 55meters, about X40, taken with a 5inch hypo
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Crayfordjon
Inventor
Reged: 06/17/09
Posts: 368
Loc: UK
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Sorry about the blooper, here it is again.
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Crayfordjon
Inventor
Reged: 06/17/09
Posts: 368
Loc: UK
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I had computor problems all solved now, the diagrams and piccie will clarify the system and show the actual image quality.
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Crayfordjon
Inventor
Reged: 06/17/09
Posts: 368
Loc: UK
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This image taken with a five inch Hypo at night of a porch light, dist 55m. Note: I use terrestrial objects to test optics, I get more information about aberrations and field distortions etc,than by imaging stars.
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Crayfordjon
Inventor
Reged: 06/17/09
Posts: 368
Loc: UK
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Ignore this, but it is an image taken through a singlet lens having the same aperture and F:no as the five inch Hypo., note the considerable CA.I'm having problems again!!
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Crayfordjon
Inventor
Reged: 06/17/09
Posts: 368
Loc: UK
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OK then go with the flow!! This image is the same as the last only taken with the five inch hypo,Same F/L same F: No Note Difference!
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Crayfordjon
Inventor
Reged: 06/17/09
Posts: 368
Loc: UK
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The out of focus blur to the left is not the scope but the camera was hand held and tilted.
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Crayfordjon
Inventor
Reged: 06/17/09
Posts: 368
Loc: UK
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The out of focus blur to the left is not the scope but the camera was hand held and tilted.
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Andy Taylor
twistin' by the pool
Reged: 09/24/08
Posts: 431
Loc: t=0 UK
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OK,
It's a bit slow this afternoon so I had a rummage in the parts bin...
My first find is a 41/2 inch .25 diopter used to achieve close focus with motion picture lenses. (plano convex) 
Focal length is 2000mm. I make this F19 ish. Sooo - if I only use the center 50mm I get my F40.
Next find is a 25mm dia x 180mm focal length achromat.
Using vee blocks and blue tack I then set it up with the achromat at 1000mm from the objective.
I used a movie camera eyepiece (about 35mm focal length) and focussed up on my sharpness indicator chart at about 45 feet away...
Yes it works!
Considering that collimation was rough at best the image was very bright, sharp and clean. CA looked minimal.
I will bring in some astro eyepieces next week and try to rig up something more accurate.
I also need to find a larger diameter achromat.
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Equipment list of shame:
A strange heap of assorted junk that when thrown together and dragged out into the dark shows me the wonders of the universe...
And then dews up...
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