Crayfordjon
Inventor
Reged: 06/17/09
Posts: 371
Loc: UK
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There is a new experimental refractor concept, it uses a very weak objective lens which is a single plano convex 100mm aperture imager of around F:40, this is not corrected for color, but if a small achromatic 7X50 binocular objective is placed half way along the focal length, the resultant F:6 image is very free of colour, the difference between the red and blue focus is only about 1mm, the color reduction is many more times than it should be, it can be reduced to 0.4mm by addition of a second lens. It is known as a "Wall Hypochromat", it is not a dialyte or a schup' as there is no flint lens in the system, the color is suppressed not corrected for. There is a little color left in the system and this can be ignored if you are not too fussy, it will make a superb RGB filter scope. The main thing it is very cheap, I have made a 5inch version.The system is in it's infancy and needs to be developed, how about it you ATM's out there. Ref to the Journal of The British Astronomical Association June 2009 vol  119 No3. Wanna know more, discuss it with me.
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John Kemp
journeyman
Reged: 03/09/09
Posts: 8
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Hi Crayfordjon - I was just about to email you to say that I think your suggestion of hypochromat is a better one than my arcane suggestion of elakhistochromat. You will no doubt have spotted that hypochromat(ic) already exists with another technical meaning, but this does not matter! Best wishes, John
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Crayfordjon
Inventor
Reged: 06/17/09
Posts: 371
Loc: UK
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Hi John, I am sorry not to use your beautiful description of the new system, but I felt that it would,be a bit of a mouthful,so after much brain damaging cogitation the option of Hypochromat seemed fairly apt, the 'Hypo' means below, "hence Below color" You have no doubt heard of Hyper chromatic effect where "hyper" means above, this is found in some systems where over correction happens, I found this on my research into dialyte systems where the blue and red foci are reversed. 
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Crayfordjon
Inventor
Reged: 06/17/09
Posts: 371
Loc: UK
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Post deleted by Crayfordjon
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Crayfordjon
Inventor
Reged: 06/17/09
Posts: 371
Loc: UK
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The system was called a Parachromat, the name has been changed
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robboski2004
member
Reged: 01/14/08
Posts: 21
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Quote:
There is a new experimental refractor concept, it uses a very weak objective lens which is a single plano convex 100mm aperture imager of around F:40, this is not corrected for color, but if a small achromatic 7X50 binocular objective is placed half way along the focal length, the resultant F:6 image is very free of colour, the difference between the red and blue focus is only about 1mm, the color reduction is many more times than it should be, it can be reduced to 0.4mm by addition of a second lens. It is known as a "Wall Hypochromat", it is not a dialyte or a schup' as there is no flint lens in the system, the color is suppressed not corrected for. There is a little color left in the system and this can be ignored if you are not too fussy, it will make a superb RGB filter scope. The main thing it is very cheap, I have made a 5inch version.The system is in it's infancy and needs to be developed, how about it you ATM's out there. Ref to the Journal of The British Astronomical Association June 2009 vol 119 No3. Wanna know more, discuss it with me.
Hello John,
could you supply the perscription for you lens design ?
when you mention there is no flint in the system.......
what type of glas makes up the second part of the bino
objective ??
also if the final focal ratio of you system is F6 then
colour error has to be less than 0.4mm to even be as good as
a standard achromat.
look forward to further details.
all the best
Ian Robinson.
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Crayfordjon
Inventor
Reged: 06/17/09
Posts: 371
Loc: UK
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Diagrams of the hypochromat principle
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Crayfordjon
Inventor
Reged: 06/17/09
Posts: 371
Loc: UK
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Yes Ian. The objective lens is BK7 but a low dispersion glass would be better. It is plano convex and need only be ground and polished, figuring is unescessary. It is F:40 for reduction of lateral chomatic aberration The bino achromat is just that, no special features 7X50 binos are OK but higher powers are obtained with focal length of 330mm Coliour is not so bad as calculation would predict, the images are brilliant lit and the resolution is that for the objective not the bino lens as so is the resolution. there is some edge color due to lateral CA, so the weak lens must be just that.I have seem worse secondary residual color in a commercial grade 5inch refractor! Make one and try it, you will be surprised.. easy! I fold my Hypos down to one third of half the focal length of the weak og. My current Hypo is only 32 inches long in spite of a focal length of 6000mm.
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Crayfordjon
Inventor
Reged: 06/17/09
Posts: 371
Loc: UK
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Further info Ian, The scope is unique in that it has an enormous depth of focus ranging from infinity to a spot of tape tacked to the front of the Objective, it will even focus on anything inside the objective lens, in this case the ob lens is out of play and only the reduction lens is doing the focusing, however there is a serious loss of aperture if the focus is on an object less than the focal length of the ob lens away. I fold the optics in three by using two flats, but the flats do not have to be high precision, within one wave is quite adequate, easy to make.
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GJJim
scholastic sledgehammer
Reged: 09/09/06
Posts: 907
Loc: Western CO
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Amazing - the objective doesn't have to be figured, and the EFL is 6 meters!
 
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tim53
Pooh-Bah
Reged: 12/17/04
Posts: 1440
Loc: Highland Park, CA
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I can't find anything on the internet about this design. Any pointers?
-Tim.
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"We`re just waiting looking skyward as the days come down.
Someone promised there`d be answers, if we stayed around."
-Orchestral Maneuvers in the Dark, "The Romance of the Telescope"
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George Kiger
member
Reged: 05/19/06
Posts: 29
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"it will even focus on anything inside the objective lens, in this case the ob lens is out of play and only the reduction lens is doing the focusing, however there is a serious loss of aperture if the focus is on an object less than the focal length of the ob lens away..."
I assume that focus can also be achieved past both the primary objective and the intermediate lenses, but in this case the aperture is reduced even further to the diameter of the observer's pupil!
Edited by George Kiger (06/24/09 01:30 PM)
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DAVIDG
Carpal Tunnel
Reged: 12/02/04
Posts: 1985
Loc: Hockessin, De
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I played around with OSLO EDU and setup the design as described, that being a 100mm x 4000mm plano convex lens as an objective and achromat place 2000mm from the objective. I used an Edmund A32-886 50mm achromat which has 150mm focal length. This is a typical binocular achromat. I found the color correction to be fairly good but the effective focal length of the system is only 278mm which is not close to 6 meters. I also found that the 50mm diameter lens would be too small in diameter when placed at 2000mm away from the objective. Maybe I'm not understanding the design correctly ?
- 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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DAVIDG
Carpal Tunnel
Reged: 12/02/04
Posts: 1985
Loc: Hockessin, De
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Here is the performance graphs.
- 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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rwiederrich
Goldfinger
Reged: 11/17/05
Posts: 8320
Loc: Bremerton Washington
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Quote:
Further info Ian, The scope is unique in that it has an enormous depth of focus ranging from infinity to a spot of tape tacked to the front of the Objective, it will even focus on anything inside the objective lens, in this case the ob lens is out of play and only the reduction lens is doing the focusing, however there is a serious loss of aperture if the focus is on an object less than the focal length of the ob lens away. I fold the optics in three by using two flats, but the flats do not have to be high precision, within one wave is quite adequate, easy to make.
Very interesting for sure. What if you wished to use a bit stronger plano convexed lens...and its focal length was shorter...will the system still work accoring to your descriptions?
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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nytecam
Postmaster
Reged: 08/20/05
Posts: 5748
Loc: London UK
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Hi CrayfordJon - your new scope got a mention a few weeks ago on this forum but thread got hijacked by a Schupmann fan  You're the best to describe - hope to see you maybe this Saturday at Greenwich for annual BAA ExMet 
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Nytecam 51N 0.1W
Meade 30cm LX200+ETX-70+e-finder+C8+Ha+CaK PSTs SBIG SGS+homebuilt spectrographs
Starlight SXVF_M9+Lodestar CCDs/Canon 300D DSLR/Fuji E550
My observatory build-ETX-70 imaging-my videos
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Crayfordjon
Inventor
Reged: 06/17/09
Posts: 371
Loc: UK
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Hi Tim 53, you will not find anything on the net because it is a brand new conception, and was published in the Journal of the British Astronomical association this year. I discovered the principle about two years ago and have been researching it since, this is it's first exposure to the ATM community.
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Crayfordjon
Inventor
Reged: 06/17/09
Posts: 371
Loc: UK
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Hi GJJJim, The objective lens is so weak that there would be difficulty figuring it, the Hypo system is very insensitive to errors of figure, but the upside is that only a very shallow sagitta is required on the front surface, easy peasy to make.
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Crayfordjon
Inventor
Reged: 06/17/09
Posts: 371
Loc: UK
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Hi George Kiger, yes you have hit the nail on the head, the aperture becomes very small when the system is focussed on any object a meter or so away.
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John Carruthers
Skiprat
Reged: 02/02/07
Posts: 2270
Loc: Kent, UK
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Hmm, I started a 150mm x 4m heliostat lens a couple of years ago, maybe I'll finish it and try your idea.
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Jc
ATM 10" F6.1, 1/25th wave spec (max wavefront error +/- 1/12.6 in zone 4 of 6, sodium light )
6" F7 spec
127mm F9.4 Refractor
10 x 50 bin
ETX80 (finder)
Canon 20D
PST
DSI 1
and a curious mind
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