The Ranger and the Pronto Are No More

--
To reach me directly, remove the Z, if one appears in my e-mail address...
"Jon Isaacs" wrote in message
...
What are you feeding them?

Roland Christen

I think Alan's Hummers are fuelling up for the trip across the Gulf of
Mexico.
This is supposed to make them extra fiesty.

According to what I have read, they fly non-stop from
Louisana-Alabama-Florida
coast across the Gulf of Mexico to the Yucatan. Its about 500 miles and
they
do it in around 20 hours or so. They leave with a full load of fat at
about 5
grams body weight and land at about 3 grams and hungry. In the spring
the make
the reverse flight.

I figure you probably knew all this but I just wanted to get in a Plug
for the
Video/DVD: G

Hooked on Hummeringbirds

My little Costa's stay right here year around, and will eat from a feeder
while I'm holding it... Being eye to eye at a distance of a few inches is
a common occurrence around here... They follow me back and forth while
I'm mowing the yard. They're fearless... My Anna's stay year round, too,
but while they will come quite close, they aren't quite as amazing as the
Costa's when it comes to close encounters...

Jan
Near Phoenix, AZ

"Jon Isaacs" wrote in message

Both Thomas Back and Roland Christen seem to feel that Abbe's definition
has
out lived its usefulness.

Gotta love the guys who hang their hat on Abbe. If you have to die with the
best toys to win, then there's got to be rules!

I like what I've seen Roland do recently: quantify color correction relative
to a familiar optical system. Seems to be more informative way of
expressing a scopes location in a continuum.

Ed T.

"Mike Fitterman" wrote in message

The OA4 is still the best deal out there. Far better than what Orion is
offering and I haven't even looked through it!

Mike, we're happy you're happy. Really. Lets move on.

Ed T.

I believe Dan has said that the 9" OA is around 20lbs.

Mike.

"Ratboy99" wrote in message
...
Actually, the 9" OA weighs a lot less than an 8" TMB (it's a lot longer
though ;-)

The TEC 8" is said to weigh in at under 50 lbs (this is including a 9 lb
counterweight to put the center of balance at the center of the tube).
rat
~( );

email: remove 'et' from .com(et) in above email address

"Alan French" wrote in message
.. .
"Mike Fitterman" wrote in message
news:miURc.10766$gd1.9660@trndny05...
I have the ED80 and yes, I've looked in the slightly smaller version of
the
OA4. The OA design is a phenominal scope. Jon mentioned in a later
post
that I sold my 6.5" which I did. I'm getting another OA from DGM. I'm
not
sure what's so bad about that one Jon? The design is really a great
design
for the aperature size. Neither of you have looked through the OA, I've
at
least looked though siblings of both designs.

Mike,

You seem very good at making assumptions. Dan has brought an OA to The
Conjunction some years, and I have indeed had a chance to look though an
OA4. There was also an OA 6.5 (or something around that aperture) at a
couple of local star parties.

I think you may have been around when I had my 6.5 last year at the
Conjunction. I brought my 16" scope this year (no planets to really look
at), poked through some holes briefly before packing up at 11pm on Friday.


Even though I have looked though an OA4, I have not spent a lot of time
with
one, nor have I had a chance to compare one to a 4" APO, so I am hardly
going to express my opinion about how the two compare. I do have a good
idea what a phenomenal 4" scope can do, since we have had one here for
many
years, but I am hardly going to pass judgment on two telescopes that were
not tested side by side.

I'm not asking you too. I'm passing judgement :-) I was merely pointing
out that the OA 4" is a better bargain. It's cheaper, about the same focal
length, and has no color issues.


I will say that, based on looking through a lot of scopes at a lot of
conventions, the differences between well executed scopes of different
designs having the same aperture are generally rather subtle (allowing a
little for central obstruction), and there are no telescopes that
magically
overcome the limitations of their aperture.

And somehow people seem to think that I've said that OA's magically overcome
their aperature. I make big light of the fact that the OA beats a bigger
scope on some particular detail, but that doesn't mean it beats bigger scope
on all details. Trust me, I don't think that. I do think they are
excellent for their aperture and that unobstructed views make a huge
difference (at least to my eyes) to obstructed ones. Especially when they
are within 2 inches or so of aperature. Most of the big differences I've
seen with the OA is around seeing conditions (rarely do we get great seeing
conditions) and this is where unobstructed "smallish" aperture exceeds
bigger aperature on medium to high power viewing.


Clear skies, Alan

Alan, there was one other comment you made about collimation. The
collimation on the OAs in many ways is easier. It's different than the
standard newt, but once you get the trick, it's fast and holds collimation
much better than standard newts due to the fixed secondary. I've gone
months without the scope needing collimation. Everything you've learned
about collimation of a standard newt, you can pretty much throw out the
window with this design. On the other hand, you can use tools much more
effectively in the standard newt.

Mike.

I believe Dan has said that the 9" OA is around 20lbs.

Mike.

No mention on the website of a tube being offered with the 9". But at 20 lbs
inclusive, that would, of course be very light. It must have a very thin
mirror, light weight cell, spider and focuser in a featherweight tube.

OTOH, at 20lbs for a 9"er, it doesn't sound especially robust either, but what
do I know? I've never seen one. How is the mirror cell configured to keep the
mirror from flexing?

At 82" long and 14" in diameter (suggested tube size from the web site), it
still wouldn't quite fit in the back of my pick-up. (Compacted length of the
refractor is 66", diameter is, well, around 9"...

But, really, more interesting to me, is that I still haven't been able to
figure out why you are so enthusiastic about derailing refractor threads with
comments regarding the OA Newt design, especially considering that each time
you do, you invariably attract to yourself abuse for hijacking the thread.

I'm surprised that Dan hasn't told you to leave well enough alone by now. I
myself question whether you are helping or hurting his cause. I can't imagine
that all this could be having the desired effect. But who knows, maybe any
press is good press, eh?

I freely admit that I've never looked through a DGM scope, but I don't really
have to in order to know that such an instrument is still a mirror system, and
not a refractor.

The matter remains apples and oranges in more respects than the two ideas have
in common.

The air still has to pass twice through a Newt (and I'm not knocking Newts, I
own three of them).

And they still use mirrors at the bottom of tubes that have to cool down before
they stop affecting image steadiness, regardless of how big the tube is (the
light still enters from above the mirror).

They still use light scattering, thin metal films. This does have an effect on
contrast compared to a strictly refractive system.

The objective still sits near the ground when observing, making it subject to
any heat that may be rising from the ground.

This has nothing to do with the size of the tube, if the back is open, air is
going to pass in front of the mirror at some point.

The observer's (ostensibly warm) head is still positioned at the top of the
tube, near where the light enters the instrument.

This body heat still has the potential to enter the light path and disturb
images.

The cutout mirror still has coma, inherently.

Thus, without a doubt, there remain significant obstacles to the optimum
performance of the OA Newt design, that are not overcome simply by making the
design "off axis" in order to circumvent a CO.

And true, many of these issues can be addressed quite well, if not even
overcome, but it still doesn't make a Newt a refractor.

I'm not saying it is not a fine design, either. I like all kinds of telescopes.
I just think it is kind of weird you keep popping in here and doing that thing
that you do.

The big apo on the other hand, has its own issues; it costs a fortune, takes
forever to get, still has to have smooth well corrected and well coated optics
in order to "do its thing", typically requires a quite substantial mount, and
did I say it costs a lot? There is really no way to justify the expense except
to hope that over time it retains its value (at least at the moment I figure it
is still beating the stock market).

Anyway, nice going around with you on it all again, see you next time.
rat
~( );

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Oh man! Now the Birders are invading the SAA forum! Two days ago it was the
other way around. You guys better stay the heck away from
alt.rv.pop-up-trailers.



Rich,

A friend once commented - "If hummingbirds were the size of small dogs, it
wouldn't be safe to be outdoors."

Clear skies, Alan



rat
~( );

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I should put a scope on them - they are so close anyway that I've never
considered it, but I'll wager they are beauties through a scope.

Clear skies, Alan

I set up my Swarovski 65 (don't you have the same one?) from time to time to
check out the hummers in my back yard. Pretty nice way to observe them
actually, bugs at 100 feet, too, for that matter.

Which reminds me! I set the Traveler up to look at the gibbous Moon through the
branches of a tree about two hundred feet away the other night.

Right there between the branches, and backlit by the Moon, was this huge spider
hanging out on his web, such a cool sight.

I grabbed my camera, but the Moon had moved by the time I got back.

It was pretty surreal, that spider had no clue that he was being
surreptitiously observed in the dark from such a great distance.

The image was simply fantastic.

Thanks, Roland!
rat
~( );

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"Alan French" wrote in message
.. .
"Stephen Paul" wrote in message
...

"Alan French" wrote in message
. ..

You haven't seen the Orion 100mm f/9 ED. You haven't looked though
an
OA4.
Somehow, though, you know which is better. You must be doing
Psychic
Telescope Reviews, and I'll give them the credibility they deserve.

I have seen a couple of the OAs, but have not had an opportunity to
really
check one out. The one that showed up at our public Star Parties was
never
collimated. I once had a big interest in various off-axis
reflectors -
Schiefs and Tri-Schiefs - but after seeing a bunch decided they had
nothing
to offer over a good, well made Newt, and Newts are easier to
collimate.

Do I detect the pot calling the kettle black?

In what fashion? I said I have never had an opportunity to really check
out
an OA, and my only comment was that the one at our star party was not
collimated. That was obvious to several folks who looked through it. I
don't see that I offered any opinion on how they performed - and I won't
unless I get a chance to use one extensively and compare it to another
quality 4".

As to my comments on other off-axis reflectors, I have actually seen and
tried a bunch of these over the years, and compared them to Newtonians of
similar aperture set up near by. The designs got a lot of good press, and
I
was quite tempted to make one, but I have always been a fan of seeing a
scope in person before taking the plunge to make or buy. A bit different,
I
would say, than making a guess about two telescopes I had never seen
(including one, I believe, that no one has seen).


In the context of the conversation, it was so easy to infer that the OA was
one of the off-axis designs which you deferred to a standard newtonian, as
to seem implied.

Sorry if I mis-read.

FWIW, I've seen the planets through a 4" apo, and I wasn't overly impressed.
To me, a 4" scope that doesn't do super low power is pointless. If someone
gave me a 100ED OTA or an OA4, I'd sell it on Astromart and buy a decent 4"
F5 achromat and a UniStar Light Deluxe with D&S Compact tripod.

That said, there has never been a better argument for the existence of the
OA4, than a market demand for a $999 100mm F9 ED refractor. If people are
really interested in a 100mm F9 with color correct performance for $999,
then the OA4 at F10.5 on a Dob mount isn't at all an unreasonable
alternative on a cost/performance basis.

Stephen