Re: 100mm f/8 or 130mm f/6
- --- In firstname.lastname@example.org, "W. Gondella" <strehl985@c...> > I
wonder how stopping a 152 down to 100mm would improve the 152? I
wonder what it would
> do to the strehl intensity? Tom, have you ever done anyexperimentation and testing in
> this regard? This would imply a telescope starting with (I'mguessing) on average, a .975
> strehl, then stopped down from f/ 7.9 to f/ 12! A 100mm f/12 TMB!And I would think it
> would HAVE TO improve the wavefront to *some* degree!!! :) Youare limiting the area
> (and errors within) to a much smaller degree (only 43.28% of theoriginal surface). This
> might (totally guessing again) bring a .975 scope up to .98 or(dare I say :) .985 strehl?
>Most interesting question, Wayne, especially the last one. The way
> Could we tell the difference? Tom, what say you?
I understand it is that Strehl greater than 0.95, it would be
extremely difficult if not impossible for the eyeball to see any
difference, would it not?
----- Original Message -----
From: "leonard_bel" <ngc7789@...>
Sent: Monday, December 08, 2003 2:00 PM
Subject: [tmboptical] Re: 100mm f/8 or 130mm f/6
> Wayne ,
> In your well educated eyes the XL is now first generation ,
> kind of old in the eyepiece development market now days.
WG: Perhaps. But so are a lot of my own eyepieces. Most of my Naglers are 1st
generation (in fact, some of the first made), as are some of my other wide-fields and
plossls. In fact, I have military surplus, very long Rini eyepieces, and a lot of other
ones, including an Ortho (no name) I bought ($5.00?) at a swap meet. I judge (and keep)
an eyepiece based solely on what it delivers to my eye. I may keep an old surplus
eyepiece but pass on a shiny new "Type 7" with 11 elements (you get the idea). I don't
discriminate based on price, looks, or name.
> Some people among us cannot ever hope to purchase a top of
> the line scope much less a lot of fancy eyepieces to go with it.
WG: I think everyone has within their reach the possibility of owning at least one good
quality telescope, if they shop around. And I do not find an unbreakable correlation
between the fanciness of an eyepiece and the quality of the views it delivers. Lots of
money and lots of elements WILL get you a super wide, sharp AFOV, but, surely the
super-mono is based on a very old design--- nothing truly "fancy" about them, and yet they
have knocked over some of the very best eyepieces out there. I have a 2-inch Kellner
(60mm) which I have stunned people with. I crank it up to a 15mm (4X Powermate) in my C14
and after they say, "Wow!" looking at craters on the Moon, I tell them they just looked
through a Kellner! :) Good eyepieces come in all sizes and shapes. And it depends on
what you expect out of them and how you use them (and for what).
> very long time observer (over 40 years)I know never owned anything
> other than a run of the mill scope and some decent kellners and
> ortho's but viewed more and saw more than most people ever will. And
> after looking through AP scopes ,TV's etc. still enjoyed his equipment .
> But he did know how to collimate and take care of his scope.
WG: Good point, Leonard. While it doesn't hurt to have good equipment, the ultimate tool
is the OBSERVER himself (or herself). No amount of money spent can make up for raw,
native observing skill. I see more and more people today getting into this hobby and
going right out first thing and buying the most expensive stuff available, just because
they can afford it. Maybe it is because there is (IMO) more equipment, better quality and
greater affordability, than ever before? I just read where a guy bought his first
refractor, and it was a state-of-the-art apochromat (non-TMB). I read where some people
have only been in the hobby for a couple of years (or less?) and own lots of scopes or
even several A-P's, Questars, Zambuto mirrors, and the like. My first six or so scopes
(when I was much younger :) were cheap Tascos, Astroscans, and the like! I started out
with many a Huygens, Ramsden and Kellner-type eyepieces! So I wonder when people now jump
into the hobby and buy ultra high-end stuff right off the bat whether they ever really
know and fully appreciate what they truly have?