20 inch f8 Chief Ed Jones designed and a 17 f9 Zanbuto Wide Band Chief Mike Jones designed .Both unobstructed telescopes .
"The White Zone is for loading or unloading of passengers only. No Astrophotography." Cosmic Acres! Greatest restoration challenge: Tulley and Sons 3" achromat on Altazimuth mount, circa ~late 1820s
Quote:There are a couple things that should be noted about the pics- both pertaining to edges. If you look close, you'll see an edge issue on the -LEFT- of the lens, right at the bevel. None can be seen on the -RIGHT-. A good way to make a quick test for gross edges without any testing.
Quote:Obviously, this shows the edge problem is on the concave back side of the lens, which is only pad polished. The convex front has been pitch polished for a couple hours, and no such artifact can be seen on the right; nor is it in a position to be affected by the TDE of the back side. Cool, huh?
Quote:Maybe if someone has doubts about the color correction in a refractor they have, this test could be used to make a rough check.
Quote:But I think this is falling on deaf ears.
Quote:Your first 2 quotes of mine pertain to the pic of the 8" meniscus lens. I guess you just don't see it. In a private communication with someone else recently, who is very knowledgeable about testing and paying attention to what they can see when using their eyes correctly, plainly understood full well with what I'm referring to
Quote:If you saw it for yourself instead of just the jpeg picture
Quote:paying attention to what they can see when using their eyes correctly
Quote:Your 3rd quote of mine referrs to the dot matrix that's set up about 35 yards away. I related how I made it. Try it for yourself, perhaps; and with a refractor or lens to reveal what I explained.
Quote:Now the reply to your 4th quote, first sentence is fine.
Quote: That's precisely the purpose of this scope. But I and I think others would appreciate you refraining from singling anyone out, and posting something that can be construed as criticism.
Quote:I am not to be credited for the basic idea of this design. John Wall (CRAYFORDJON) was the originator of it, and I'm simply trying to carry it to a next step, as it were; with a little improvement that could make it a legitimate acceptable adaptation of a refractor of largish aperture.
Quote:There is -NO- refractor that has absolutely -NO- color.
Quote:But there seems to be a -LOT- of folks in the refractor forum that says they are just fine, and they spend a lot of money on them. In essence you're telling them they made the wrong decision???
Quote:This is intended for low to medium powers, and hopefully bridge the gap between John's Hypo and a good achro, for a relatively modest outlay.
Quote:It might work just by making a smallish piece of PCV flint to go with a standard achro reduction lens, and to make a crown positive meniscus of full size.
Quote:And just my 2 cents, I wouldn't make a mirrored telescope with a piece of BK7 lens substrate. Can be done, but there are better choices.
Money can't buy happiness, but it sure makes living with misery a lot easier!