You told me a refractor can only do 30x/inch at best. Now that tells me,
you don't know what the hell you talking about.
50x/inch rule is for compound telescopes, a good refractor able to do twice
as much. My TV Pronto 70mm f/6.8, on a good seeing night can hold 250-300x
magnification on planets, using TVs 5x barlow, that's 100x/ inch. My old 3"
f/15 Edscorp performed even better. That's why some people love those f/15
achromatic refractors, cost and performance. I was on a star party, one guy
had 8" f/15 refractor, it was huge, but he had the longest line at the
scope.
Resolving power is another question, larger aperture can resolve more. But,
still there is a limitation of seeing and atmospheric distortion. You may
say theoretically an 8" or 10" SCT can resolve 1/2 arc-second or less, but
you'll find very few days to achieve that, be cause the seeing, upper
atmosphere turbulence etc....
Told you, go read Suitor's book on optical theory JPL guy.
I worked for Loral Space company 12 years and others before, you don't
impress me.
JS


"David Nakamoto" wrote in message
news:zp2Ld.7590$RI.6871@trnddc06...
This is tiresome. You spout arbitrary assertions without giving the
facts, other than some short sentences about your experience, to back them
up. You're obviously a troll. On my kill list from now on.

As for the others that might be reading this, I think it's safe to say
that most professional astronomers do not own their own equipment.
They're into research, which requires very large permanently mounted
telescopes. A few do use equipment amateurs use, but this is the
exception rather than the rule. The few I personally know, mostly from
JPL, own a wide variety of telescopes, because other factors come into
play, just as they do for any amateur astronomer, because when they use
their own instruments, professionals become amateurs, for reasons I laid
out above.

As for the arbitrary assertion that I own an 80mm f/5 Syntha, totally
wrong, but then since none of your statements are based on fact Szaki, why
should anything you state about me be based on fact?

Go away little man. I'll be willing to bet that I've been an amateur
astronomer longer than you've been on this earth, with strong ties to a
lot of people with a lot of experience that I find both enlightening and
entertaining, unlike you.
--
Sincerely,
--- Dave
----------------------------------------------------------------------
It don't mean a thing
unless it has that certain "je ne sais quoi"
Duke Ellington
----------------------------------------------------------------------

"Szaki" wrote in message
...


And I own a short focal ratio refractor, so I know something from
personal experience,

*I can imagine, you own one those 80mm f/5 Chines achromat, great
experience in refractor county. Good luck guy!
You can suck on your Mak. If it would be that good, every ones choice
would be a 5-6" Mak, but most pro astronomers go out and spend 3-5
thousand for 4-5 APO refractor.

if you're going to tout that out as your badge of authority. And one
thing I would not do, which you do, is to think that a refractor is a
refractor is a refractor. Focal ratio and objective design DOES MATTER,
but I doubt you understand this, given your responses to my messages.

Whatever experience you think you have, it's clear to me you need a lot
more before you can make cogent and fact-backed statements. That, and
read the messages your responding to more carefully.



I owned all those scopes, but I don't give up my refractor. After
owning many telescopes, I settled to C102F APO refractor (most used),
4" Mak( MTO-11CA 10/1000 Telephoto Lens) for portability and a Ultima
C-11 OTA for DSO's. They all fit on my EQ mount or the GiroII for
alt/az movement.
All these telescopes are very portable and easy to store, I know the
pros and cons of these scopes also.
My 4" Mak don't even come close to my TV Pronto I use to own. I heard
good things about the Orion80ED.

So have I, but the fact remains that those reports I've gotten from
observers who I know to have lots of experience evaluating telescopes of
various designs and makes have said it was good for a two-element short
focal length refractor, meaning it will perform within the expectations
of such a telescope, and NOT like a longer focal ratio one, or a
three-element one, or an expensive one, et al.


One has to use barlows for short focus length refractors, to get higher
magnification, that's all. I hate to use a Mak for terrestrially, long
focus length, narrow field. Yak!!!!

But the Mak will deliver 2.4 times the magnification for the same
eyepiece, so it is also capable of delivering higher magnification,
important for planetary viewing. And in any case, I don't think that,
given what I've heard and seen of the Orion 80ED at star parties, that
you can push it much past 30x per inch of aperture, so your objection
that this is the "limit" on the Mak (something I also disagree on, from
collective experience) is moot.

*Hey, guy get lost, I can't tell, you don't know what **** you talking
about.
30x /inch on an 80mm or 3"+ ED refractor would be only 90 x power. A
cheap achromat can do better than that. My 60mm Tasco outperforms that.
You should have your examined first.

And the original poster asked specifically for planets and the Moon.
Why drag terrestrial viewing when it was not specified?

*It was not specified, but when buy a small portable scope there's all
ways time to use for that. He's not going to look it only the Moon 24
hours, 7 days a week.

In this case, the Mak is an
instrument he should consider, given that for a given eyepiece it will
deliver more magnification,
*I'll eat my hat, if you can do 600x magnification with your 5" Chines
Mak. Get real guy!
Stop reading the Orion catalogs.

less color dispersion, and potentially sharper views, if the
contrast isn't too bad.

*Bull ****. That's why they advertising the Mak-Newt, "refractor like
images", he? I did look through a 6" Mak-Newt, my friend had one, it's
close but not quite. Mak-Newt has 19% CO.
Why don't you read Suitor's book some times,than come back and argue.

JS




--
Sincerely,
--- Dave
----------------------------------------------------------------------
It don't mean a thing
unless it has that certain "je ne sais quoi"
Duke Ellington
----------------------------------------------------------------------


"David Nakamoto" wrote in message
news:i6UKd.1078$UB6.973@trnddc01...
Szaki, you're thoughtless in your answers, as simple math will show.

We're talking about an f/7.5 system in the 80ED, which you would have
known if you took the time to visit the Orion website, and thought
anything about giving correct answers instead of "showing off", and
doing research before writing anything down. This means the focal
length is 600mm. Since "focal length of telescope" / "magnification"
= "focal length eyepiece", 600 / 250 = 2.4 mm. Even if such an
eyepiece exists, it also means you're pushing 80x per inch aperture in
a two element 80 mm telescope, only possible with the best optics
(which the Orion is not), long telescope focal ratios, and under
absolutely steady nights.

And your comparison is not correct either. You're comparing a 3-inch
f/15 refractor to a 3-inch f/7.5 refractor (the Orion ED). No matter
what you do, you cannot achieve as much magnification through the same
eyepieces from the latter as through the former. As anyone who knows
optics knows, figuring and testing long focal ratio systems is easier
than short focal ratio systems (steepness of curves as well as tighter
requirements on the figure of the curves for the short focal ratio
systems are two reasons). I have no doubt that a 3-inch f/15
refractor, if properly made would outperform a similarly sized Mak
(127 mm aperture and f/12 focal ratio) but we're not comparing such a
Mak to an f/15 instrument, but a much shorter focal ratio instrument.
Color dispersion is greater in such systems and affects performance,
while the Mak is more immune to such effects.
--
Sincerely,
--- Dave
----------------------------------------------------------------------
It don't mean a thing
unless it has that certain "je ne sais quoi"
Duke Ellington
----------------------------------------------------------------------

"Szaki" wrote in message
...

"David Nakamoto" wrote in message
news:wqQKd.403$zb.85@trnddc07...
While I agree with other posters about the optical properties of the
refractor, there are two things that you should also keep in mind.
First, the Mak you mentioned is capable of over 2.5x the
magnification of the refractor you mentioned due to its focal
length,

That's a bull! Orion 80ED should do 250x or more any day, so 2.5x the
Mak127 magnificatain, as you suggesting, would put it over 600x.
Never happened!Hahahaha!
I owned 6" Intes-Mak-Cass, much finer and more expensive OTA than the
Orion 127 Mak, but it had to have excelent seeing to perform. My 3"
f/15 Edscorp refractor regularly out perfomed the 6" Mak when the
seeing was not there.
Mak has a larger central obstruction (37%) than an SCT has, so one
has to deal with large, multable diffrection rings around stars or
the moons of Jupiter.
Person who used to refractor images, would puke.
Julius