The Ranger and the Pronto Are No More

"Jon Isaacs" wrote in message
...
Ya, a couple of thoughts for sure that hold no water. For one thing, I
didn't say anything about achromats.
I said "APO-like".

As far as I can see, there are no "APO" like refractors in the TV-76
class.
The competitors here seem to be all achromats by one name or another.

The main thing is that it might be hairbrained for you to buy such a scope
because it might not suit your needs, but there are many folks who can
benefit
from owning a nice fast small APO. While they may not be wealthy by any
means,
by sacrificing something less important to them, they may well find the
money
to buy such a scope.

Jon


The TV 76 is NOT an APO. At best it is a semi-apo. If it is an APO, I would
like to see the
test results for 3 color correction at the correct wavelengths in accordance
with the Abbe definition.

ED glass is 'APO-like' for lack of a better word.

"MikeThomas" wrote in message
news:UjRRc.51453$yT2.51199@clgrps13...

The TV 76 is NOT an APO. At best it is a semi-apo. If it is an APO, I
would
like to see the
test results for 3 color correction at the correct wavelengths in
accordance
with the Abbe definition.

ED glass is 'APO-like' for lack of a better word.

The TV 76 is NOT an APO. At best it is a semi-apo. If it is an APO, I
would
like to see the
test results for 3 color correction at the correct wavelengths in
accordance
with the Abbe definition.

ED glass is 'APO-like' for lack of a better word.

Mike,

If you want to use the Abbe definition, what production scope do you know of
that fits it?

The Abbe definition, according to Baker (Planetary Telescopes, James G.
Baker, in Applied Optics, Vol 2, No 2 [February 1963], page 116) -

"Abbe introduced the term 'apochromatic' to describe an objective corrected
parfocally for three widely separated wavelengths and corrected for
spherical aberration and coma for two widely separated wavelengths."

I believe the second part is somewhat problematic with modern glasses.

Clear skies, Alan

BTW, do you know the variation of focus across the spectrum for the TV-76?

The TV 76 is NOT an APO. At best it is a semi-apo. If it is an APO, I would
like to see the
test results for 3 color correction at the correct wavelengths in accordance
with the Abbe definition.


TeleVue claims this scope is an APO doublet, reviews seem to support this
claim.

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

http://voltaire.csun.edu/roland/musing.html

Anyway, lots of good reasons to own a TV-76. Personally its more money that I
am willing to spend right now, but thats because I'm just too cheap....

Jon

"Stephen Paul" wrote in message
...


The main reason I know of to get an ED refractor, is to have both wide
fields, and high power out of the same scope. For wide fields of view, the
achromat 102mm F5's and F6's are good enough for us lowly amateurs. If
they
can't get it down to near 600mm, then it seems like a waste of effort. At
near 900mm, I'd rather have a DGM Optics OA4, or a similar performing
standard newt on Dob mount with no color whatsoever at any power.


The OA4 is still the best deal out there. Far better than what Orion is
offering and I haven't even looked through it! The OA4 dob mounted is less
than $1000. It's going to cost you $1500+ to fully outfit the Orion scope.
Your done with OA for under $1000. Not only that, absolutely no color,
unobstructed views that will knock your socks off. And I've actually only
looked through a 92mm scope not even the full 4" OA!

Mike.

"Mike Fitterman" wrote in message
newsxSRc.10611$gd1.488@trndny05...
The OA4 is still the best deal out there. Far better than what Orion is
offering and I haven't even looked through it! The OA4 dob mounted is
less
than $1000. It's going to cost you $1500+ to fully outfit the Orion
scope.
Your done with OA for under $1000. Not only that, absolutely no color,
unobstructed views that will knock your socks off. And I've actually only
looked through a 92mm scope not even the full 4" OA!

Mike,

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.

Clear skies, Alan

Anyway, lots of good reasons to own a TV-76. Personally its more money that
I
am willing to spend right now, but thats because I'm just too cheap....

I agree, and I own a 76. I also own a C5 and an XT-8, but those scopes
languish in their cases during the nighttime hours. The 76 is the only scope I
take out at night on the rare occasion that I do so. To my eyes, it's color
free. I do not have any special equipment to back that up, all I can do is
tell you what my eyes are telling me. No color. I don't care about any
definitions, I don't care about test results for correct wavelengths. All I
care about is that this scope, visually, gives me no color except that which is
naturally there. Some people are so focused on test results and measuring the
slightest flaws in scopes and splitting hairs that they seem to forget that the
number one purpose of a scope is to look through it. A friend of mine was
selling a set of filters and he got an email from someone asking for the
spectral data on the filters. If someone is that concerned with the strict
tolerances for their purposes, they should buy NEW. How many of you have
rigorously tested every aspect of your optics using Suiter's and other
techniques? I have never placed a Ronchi grid in front of my optics. I know
what my eye sees, and for this amateur, that is all that matters.

On the other hand, if rigorous testing of optics floats your boat, I will
enthusiastically cheerlead your decision. Saying that the TV-76 is "AT BEST, a
semi-apo" (whatever the heck that means) is insane. Get one and just look
through it. Don't bring any fancy instruments, just use your eyes.
Technically, an achromat is not an achromat.

Sticking my 2 drachmas in,

Mark
The Catman
^..^

www.geocities.com/mark_rosengarten
Owner/Coordinator of the Neko Ultraportable Solar Observatory
Fun WITH The Sun for Everyone!

"Stephen Paul" wrote in message ...

I find it amusing that you mention the name Tasco, and everyone groans, but
you mention Synta, and nobody flinches.

That's because nobody I know buys directly from Synta, but from other
companies that import these telescopes and package them with
accessories of widely varying quality. Needless to say, Tasco has
done a ****-poor job with their packages, which are aimed primarily at
beginners. For comparison, Orion does a much better job, and they
even attempt to educate their customers on what they can reasonably
expect from their telescopes.

Experienced amateur astronomers might be able to do things like buying
a discounted Tasco just for the Synta OTA and chucking the junky
accessories, but for most people, that's all they have when they buy
the telescope. Sure, Galileo might have accomplished much with even
worse equipment, but not everyone is Galileo. And if he were alive
today, shopping for an entry-level telescope, I doubt that he would
say "Dimentichi Orion, portimi un Tasco!" ;-)

The only Tasco I ever owned, came
from Synta. Go figure. Synta builds okay stuff, but not great.

At least they build OK stuff. What has Tasco done to deserve anything
but contempt?


- Robert Cook

Jon,

Thanks. Mike seems to let his enthusiasm get in the way of common sense.
Sue found me this great quote by Mark Twain - You can not depend on your
eyes when your imagination is out of focus. I've used it from time to time.

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.

The first 60 columns will be coming out in book form, but we don't know
when. Sue wrote the introduction some time ago.

No, I have not seen that video, but I will consider it. Sue and our friend
Jim made a trip to a used book store in Saratoga Springs the other day so
Sue could get a copy of "Star Clusters" by Shapley. She also picked up a
copy of "Hummingbirds (My Tiny Treasures)" by Arnette Heidcamp. It is
pretty interesting and has some nice photos. I had one hummer make a wrong
turn when I opened the sliding glass door and wind up in the dining room.
He had a few words for me when I cupped him between my hands and carried him
outside.

The young hummers have grown up and there is a lot of aerobatics out back
these days. They sure expend a lot of energy deciding who gets to eat.

Clear skies, Alan

"Jon Isaacs" 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.

Clear skies, Alan

Well said.

That pair, Mike Fitterman and Stephen Paul play this tag game
complimenting
those OA Newtonian scopes. The other day Mike was selling his big one at
auction on Astromart and he referred to it as an APO once again.

The other day I was wondering if Sue was going to compile her column into
a
guide...

Have you seen the Video, "Hooked on Hummingbirds." I order a copy the
other
day, it came on Saturday, pretty nice piece of work..

Best wishes

jon

At least they build OK stuff. What has Tasco done to deserve anything
but contempt?


- Robert Cook

I think Tasco has become a trademark for Department Store Telescope with all
that implies. Those 60mm jobs are actually workable, there is another whole
tier below those, 40mm scopes with plastic objectives, Toy Store Telescopes.
As a one time enthusiastic garage saler, I have seen more a few TSTs.

jon

At least they build OK stuff. What has Tasco done to deserve anything
but contempt?


Hi:

They've done some things. Not many, but some. The good, old 11TR "Red Tube" 4.5
inch Newtonian was OK, servicable, and did a stand-up job on the deep sky under
the (very) dark skies of North Arkansas for me back in the early 70s while I
was saving up for something better.

The refractors they imported (Tasco, of course, has never built a thing) were
often pretty decent up through the 70s, with the 4" they sold (a few of) in the
60s being quite respectable indeed. Some of the objectives, even on the el
cheapo 60mm jobs, were amazingly good...of course you could only tell if you
ditched the (always) deadly Huygens and Ramsdens that came with the scopes.

The 10x50 binocs they were selling in AF BXes back in the 70s were sometimes
outstanding. I still miss the pair that my brother dropped from the balcony to
the arena floor at a ZZ Top concert (my fault for letting the silly little guy
borrow them ;-)). Brought 'em home in a bag sigh.

No, Tasco were never top of the line by any stretch, but the thing that made
them _really_ notorious was the way they bottom-lined the scopes to death with
the coming of the 80s. While the 60s and 70s Tascos were often bearable, the
80s ones truly were rancid.


Peace,
Rod Mollise
Author of _Choosing and Using a Schmidt Cassegrain Telescope_
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