Telescope Reviews: "The Wall Hypochromatic Refractor"

Most articles on CN are fairly harmless regarding content and accuracy, some are pretty good, some are awful (but still mostly harmless). Your article does get my hair up. Puttering about in the lab by the garden window doing "research", that's nice, right up to the point you start trying to claim some "new optical principle". It's clear to me you don't know much optical theory because if you did you'd know there aren't any hidden rooms holding optical treasures, waiting to be discovered by positioning a couple of lenses. It's all in the theory, it's all been done, or not, if there is clearly no merit to the idea.

You keep claiming it works, I believe you. I believe it works just like an ancient singlet telescope - why would the ancients have taken the trouble to devise them in the first place if it didn't work? However, the attempt to stake your place in optical history, I suppose that's human nature. It is also human nature that it's the point you will be called out - I'm calling you out now to prove your claim.

You say you have a hypothesis but I would say you've skipped over it to some observations and right on to a conclusion upon which you get a "new principle" named after you by the BAA, whoever they are. Aside from the hypothesis where is your theory and derivations that describe and prove your claims? Your "experimental proof" would be laughed at in any scientific review.

I made the statement yesterday that this system is nothing more than a folded and telecompressed singlet telescope. I absolutely stand by this statement. The system you describe has absolutely the same transverse color aberration relative to the Airy disc, and therefore the same wavefront color aberration as the singlet alone. There is no "suppression of color". There is no practical improvement over the singlet used alone, unless you consider folding and a faster f-number improvements. But folding and telecompressing aren't new.

The basis of your claim is the large decrease in longitudinal CA but you have interpreted this decrease in the longitudinal CA incorrectly. In this design the longitudinal CA does varies to the square of the reduction ratio, just as you have seen in your experiments. But that's just geometry, work it through and you will see. The important thing is the transverse aberration varies in direct proportion with the reduction ratio, as does the Airy disc diameter. What that means is the color wavefront error is exactly the same no matter what the reduction ratio is.

Just to get a reality check I ran a design on Zemax to get some numbers.

Singlet BK7, 125mm aperture, 5000mm efl, F40

"reduction" lens - paraxial lens f=200

I ran two designs. one with just the singlet, and one with the singlet and the reduction lens spaced (about 3800mm) to produce a efl of 760mm (F/6.08). This is a reduction ratio of about 6.5

The different of the C-F focus is 77.4mm for the singlet alone (5000mm/v-number) = 77.4mm

The difference of the C-F focus is 1.82mm for the reduced system. This is a reduction of 42.5. The square root of 42.5 is 6.5

The OPD (wavefront) plot for each system is identical, about 10 waves of D (~6um).

The transverse aberration does scale with the reduction ratio but so does the Airy disc.

F40 singlet
Airy radius 28.7um
Blue radius 685um 24X
Red radius 295um 10X

F6.08
Airy radius 4.4um
Blue radius 105um 24X
Red radius 44um 10X

Yesterday I stated the fact that an achromat only possesses optical power in this system. Just to forestall the question about the paraxial lens I replaced the paraxial lens with a nominal binocular achromat objective - BK7/F4 50mm diameter and 200mm efl. The results are essentially identical to the paraxial version.

Rehashing your observations and stating you see what you see and therefore you are right regardless of what your critics say is worthless. Let us see some theory and math. If you have such confidence submit your "design" paper to a refereed journal such as The Journal of Applied Optics, they would be incredibly interested in a "new optical principle" I'm sure.

Incidently, I have no reputation on CN I know of that I need to protect. I've published in refereed journals - not an easy or pleasant endeavor - and I'm regularly grilled in design reviews by people who have little sympathy for my feelings. That's the life of this "delicate Pro".