Re: spotting scope question-specific


"nicebrid" wrote

http://www.telescope.com/shopping/product/detailmain.jsp?itemID=109402&itemType=PRODUCT&iMainCat=4&iSubCat=13&iProductID=109402

It's a "semi-APO" with a 2" focuser, and it's short and light. You can
hook
up a camera to it, and if shooting 35mm the field would cover the entire
piece of film. This system with tripod costs $550, and you can get just
the
optical tube for $400. Oh, and you can use it for astronomy, too! :-)

If you don't like it, Orion has a liberal return policy.


Howard looks interesting.

Thank you. A lot of people have said that about me.

This is where I must admit I don't know enough to understand what is what.
It is a lack of
knowledge/understanding. There is a word for what I have and that word is
ingnorance.

You have to start learning SOMEwhere -- "and that somewhere.... is here...."
(apologies to Dean Martin, Nat King Cole, and others...)

Here is what I do understand, take this orion scope as an example. The
info states "semi-apochromatic 80mm doublet lens of 480mm
focal length (f/6.0)" Ok I can work some of this out- 480mm focal length
that is F6.0 (an odd f-stop, not a big deal) requires a
front element of 80 mm. (480/6=80).
the doublet lens - is two elements in intimate contact, hey I did not mean
to to sound the way it could.

f/6 is not odd at all when it comes to telescopes. For a photographic lens,
yes, it's odd. Translation: for a scope like this, it's pretty "fast."
There are f/5 versions in 80mm, but they are more expensive, I believe. I
don't know what the Williams Optics scopes specs are, but I wouldn't dismiss
this Orion should you think f/6 is too slow.

I am lost on how to interpet "semi-apochromatic". I understand what an
apochromat is supposed to do. I gather I should not expect
an apochromat in this price range, I just don't know what to expect a
semi-apochromat to actually do. Is this like telling you
buddy that the blind date he is set up with is kinda pretty? Pretty is a
yes /no kind ofa thing, the same with apochromat glass,
right? it is or is not.

The blind date business is extremely subjective, whereas with telescopes it
is much more, uh, objective and can be TESTED with instruments. (OK,
ok.....) But seriously folks... you can count on a scope that is "semi-APO"
as being pretty damned good. It's not "near-perfect" as would be a true APO,
but it's close. A true APO will show a bright star with virtually NO color
fringing. An achromat will typically show quite a bit of color fringing
around bright objects (stars and planets) AND around BIRDS, too. A semi-APO
will show SOME color fringing, but greatly reduced from that of an achromat,
and views of birds, landscapes, stars, the moon, and planets will be MUCH
sharper.

I own Orion's 80mm f/5 achromat ($179) and their ED80mm f/7.5. (Now $499)
There is a world of difference between the two. I am VERY happy with the
ED80, and if the Orion Express was available at the time, I would have
looked seriously at that one because it is smaller and more versatile than
the ED80. The ED80 is fairly large and heavy by comparison. However, all
things being equal (mainly cost), it may be harder to make an f/6 as good as
an f/7.5. But these aren't exactly equal, so who knows.

IF the Express is as good as the ED80, I am sure you would be very happy
with the Express.

Being a astronomical tele I wonder about close focusing. They are rather
used to infinity as a distance.

Not true. First, read again that this is a spotting scope designed for
birding and astronomy. Refractors often have very long draw tubes that can
accommodate the need for close focusing.

This item is 13 pounds that is a bunch. This is not all that field
friendly, is it?

The tube itself is 5.5 lbs. That's not bad. The 13.8 lbs is for the scope
and the tripod and whatever else.. I carry a 7+ pound 4x5 camera on an 8
pound tripod/head -- it's not too bad, just somewhat awkward. You COULD get
a small, lightweight (2 lbs) spotter with built in eyepiece, or zoom
eyepiece (see Orion #9639, for example), but the quality is probably (I
don't know from experience) nowhere as good as the Orion Express.

Since the specs don't mention it, inert gas filled /sealed is not the case
here and I should probably not expect that in this price
range.

Air. :-) It's an air-spaced doublet. Three small pieces of foil separate
the two pieces of glass.

So what do the rest of the specs mean, how to interpet them is the
question.
Not up on eyepieces at all.
I found this and am working my way through it.

http://www.digibird.com/primerdir/notes.htm#apo

Thanks for the assistance

Any time. The last thing I'd want to see is you buying something you don't
like and is inappropriate for your needs.

Howard in Tucson


.

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