Crayfordjon
Inventor
Reged: 06/17/09
Posts: 372
Loc: UK
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Another night shot of a porch light at 55m, see much color?
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Crayfordjon
Inventor
Reged: 06/17/09
Posts: 372
Loc: UK
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I have been all through the OSLO analysis two years ago,and it belies what you actually see. What we are doing with OSLO is examining a tree, the Hypochromat looks at the forest! We have a newly born infant here folks, noisy smelly and I keeps you up at nights, what do we do? we train it love it and develop it into an upstanding adult that will stand apart from all others. So we must do for the Hypo. I think that what I have done is to do to telescope optics what Dobson did to telscope mountings, He built scopes out of tea chests with a flare for genius, and look at Dobs today, so I have put up a discovery for all to exploit that will hopefully follow in Dobsons footsteps. Remember the parameters of the Hypo, and keep to them, it is a low power high field angle scope, the power should not be pushed beyond X40, and it works beautifully at X25 to X30, no more. This is a scope that teenagers can build as a school project and aspiring refractors owners can make. The scope will work well for deep sky observations with and without filters, we look at fuzzies and star clusters with the Hypo, not planetary detail, and lastly, have you guys tried the scope with filters, the performance is top notch, and is a candidate for the imagers usage. So start building Hypos and stop analysing them, and evaluate the scope by looking through it for its quality!
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Andy Taylor
twistin' by the pool
Reged: 09/24/08
Posts: 437
Loc: t=0 UK
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I'm not convinced. Sorry John.
Now we are talking about special order low dispersion glass and two acromats. The price is going up as we speak.
This is going to be a massive 10ft long beastie requiring a rigid tube and a hefty (expensive) mount...
All this for 40x max...?
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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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Crayfordjon
Inventor
Reged: 06/17/09
Posts: 372
Loc: UK
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Andy, I mentioned earlier that the system has to be folded using two 6 wave flats..yes that is good enuff!. My own five inch F:40 is 30 inches long in a box tube. Breakdown is: first the focal length is cut in half by the placement of the red lens, then the remaing distance is folded three times using two flats, easy to collimate with a laser and masks during construction, the system is very forgiving where collimation errors are concerned... give it a chance now!
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Crayfordjon
Inventor
Reged: 06/17/09
Posts: 372
Loc: UK
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Andy again, I agree with you concerning the glass, I would not use it, but it would be useful to try an OSLO analysis.
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Crayfordjon
Inventor
Reged: 06/17/09
Posts: 372
Loc: UK
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Andy, be my guest! I am interested too.
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Crayfordjon
Inventor
Reged: 06/17/09
Posts: 372
Loc: UK
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Last images for this thread. taken with: Helium interference filter @ 589nm, and green acrylic filter.
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Crayfordjon
Inventor
Reged: 06/17/09
Posts: 372
Loc: UK
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Ditto.
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Crayfordjon
Inventor
Reged: 06/17/09
Posts: 372
Loc: UK
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Comments about image quality, the scope is pointed through an unopenable double glazed window, this has taken the edge off the crispness.
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Crayfordjon
Inventor
Reged: 06/17/09
Posts: 372
Loc: UK
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Some of you perhaps are wondering about the long space between the OG and the Reductions lens, and I have made some mention of this previously, but I will elaborate on this now for those ATM's who would like to build one for fun. I fold my Hypo's three times using low grade flats: around one to six wavelegths of Helium light, these are easy to make, in fact it is sufficient to grind two plates together turn and turn about and polish, and as long as the spherometer does not register a sagitta they will be good enough, no need to test even, I have done this and it works! there is no degradation of the image. The OG is a similar case , after grinding and polishing there is again no need to figure. It is these attributes that allow the Hypo to be made by a fairly unskilled ATM. The attached diagram tells it all for folding, and no you will not need a tube about ten feet long, the scope is cut down to a meter for the box tube ( around 40 inches) the tail piece holds the reduction lens and focuser etc and sticks out a few inches more as a tube from the back of the box tube. This is pretty compact for a low power six inch refractor! Collimation: The optics can be lined up during construction using a pen or pointer laser, aviable for a few $'s for you. I attach n masks over the flats with a two mm hole at the exact center; if the flats are already alumized, this will also protect the coating but if the flats are uncoated I use a reflex camera mirror taped on with carpet tape for each, with a central ring inked on to the mirrors to locate the centers. I mount the laser in the OG cell with a diapragm locating the laser centrally on the optical axis, from this setup the flats can be built into the scope accurately.
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Crayfordjon
Inventor
Reged: 06/17/09
Posts: 372
Loc: UK
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Erratum,on diagram, D/2 should read F/2= 3000mm.
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Crayfordjon
Inventor
Reged: 06/17/09
Posts: 372
Loc: UK
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Well folks it looks as if this thread is over, thanks for taking an interest, I was pleasantly surprised that it got such a good response, I hope some of you try it and not analyse it: "Think outside the box." Aufwedersehen.
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starquake
member
Reged: 02/02/08
Posts: 172
Loc: Nádasdladány
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Hmm, the concept is not bad but I'm not an optician to judge if it will have many optical aberrations or not. Why I write is, because I just found out that the layout reminds me of the Yolo-telescopes, except that those are reflectors. But apart from the front lense the Yolo layout is very much the same (of course the primary is not flat in the Yolo, but is a very complex shape to avoid aberrations, that is a pain to grind).
Most spectrographs also look very similar to this layout, where the reason for such a solution is to make the spectrograph shorter, so it will not stress the focuser that much.
I'm happy that I'm not the only one who dares to try something that's not mainstream. 
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"At night astronomers agree." /Matthew Prior/
"Astronomers, like burglars and jazz musicians, operate best at night." /Miles Kington/
10x50, 114x900, 300x1500
My astronomical sketches: Graphite Galaxy
Don't take my words too seriously, I might be wrong. And sorry for my English.
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grendel
sage
Reged: 04/12/09
Posts: 243
Loc: Canterbury, Kent, UK
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I will certainly give it a go sometime, maybe with a f27 lens from surplusshed.
grendel
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omnivorr
member
Reged: 04/09/09
Posts: 27
Loc: horsetrailer (Downunder)
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I'm no optician, but I can see the basic idea of this system, I think... at f/40 the rays are "close" to parallel where they arrive at the reduction 'lens', and that lens has an opposite abberation to that the primary has induced in those rays.. thus nulling that abberation..
at least sofar as some CA is concerned..
I gather that f/40 in the primary objective is essential, otherwise a different kind of reduction 'lens' would be needed..... (what would 'abberate' equally opposite to that tempting f/27 SurplusShed lens???)
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tim53
Pooh-Bah
Reged: 12/17/04
Posts: 1446
Loc: Highland Park, CA
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It still sounds to me like something on the lines of a 17th-century singlet with a focal reducer added.
-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"
Edited by tim53 (06/30/09 10:18 AM)
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Ed Jones
Pooh-Bah
Reged: 04/06/04
Posts: 1415
Loc: Sin-sin-atti
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Of course we'll analyze it. If you are using a 7X50 objective lens then you are vignetting a lot , even on axis making it closer to a 4 inch aperture working at f/60. I had to move the binocular lens farther back to get full aperture. I tried a number of different achromats from Newport, OptoSigma and Thor Labs but the color error was huge running between 8 to 15 waves of error. I don't see anything to recommend, a really poor performing 4 inch.
Far better in a 4 inch would be to buy f/10 or f/20 mirrors from Surplus Shed and a couple of lenses to make one of several unobstructed designs to get a color free, unvignetted high power scope in a smaller package. You might have to touch up the mirrors but it's very little work.
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Ed Jones
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Crayfordjon
Inventor
Reged: 06/17/09
Posts: 372
Loc: UK
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Hi Ed Jones you are right I cannot fault your argument. I am airing a novel approach that could be improved upon if people played around with it not minding that everything is not 1/200wave accurate. I will point out once more, a point that everyone is ignoring at the moment, although I have stressed it, and that is, it is a very good filter scope. Start thinking on those lines.
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Crayfordjon
Inventor
Reged: 06/17/09
Posts: 372
Loc: UK
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Tim in a way it is, the early guys were inventing the telescope, and a number of solutions were tried, although I am unaware of the scope you have decribed,maybe the guy who experimented with it saw the correction it gave too, but the power was too low,And in those days they wanted as much power that could be obtained to see the brand new frontier. Nowdays it does not matter if a scope is dedicated to low power, we are spoilt for choice.
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Crayfordjon
Inventor
Reged: 06/17/09
Posts: 372
Loc: UK
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omnivorr, Hi. F:27 is the bottom limit, the big problem with the scope is the lateral chromatic aberration caused by the outside edge of the lens where the prism effect is greatest, you have to cut the angle between the back surface and the curved front of the objective lens to a minimum, and this means at least F:40, more than this and the scope becomes inpractical, however I amd getting reasonable results at F:23. so your lens should be OK..just.
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