Subject:
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Re: (not quite) Looking at Mars
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Newsgroups:
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lugnet.space
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Date:
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Sun, 17 Aug 2003 01:37:02 GMT
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Viewed:
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446 times
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"Tony Alexander" <tw0nst3r@startrek.net> wrote in message
news:HJp93G.1HqI@lugnet.com...
> Greetings, fellow .Spacers!
<much snipping>
First some basics: a telescope's maximum magnification power is limited by
the diameter of the objective lense (the bigger lens--the side you don't
look through). This diameter is also referred to as the aperture. For the
typical department store scope, the objective is 60mm or about 2.36 inches
(you said 50mm, but it's probably 60). The rule of thumb is 50x per inch of
aperture, so your scope will max out at about 120x. Yes, it says 300--it's
wrong. You can get 300x, but it will be dark and fuzzy and impossible to
focus and the slightest breeze will wobble the scope so much that you won't
be able to see what you're looking at. Besides that, the atmosphere also
plays a roll in things. Some nights (most for me), there's just too much
movement in the atmosphere and no matter what you look at, it looks blurry
unless you stick with the lower powers (under 100x).
Magnification = Focal length of scope divided by focal length of eyepiece.
I have a similar little scope and it's focal length is 700mm. So assuming
your scope is the same as mine, using your lenses, you can get:
700/20 = 35x
700/12.5 = 56x
and 700/6 = 117x
And also, since you have a 3x barlow, you can also get:
3*35 = 105x
3*56 = 168x
and 3*117 = 351x
Those last two will be way to fuzzy, dark, and wobbly to use, but you can
play with them if you want.
> * First, how the heck do you aim one of these things accurately at a • little
> dot in the sky and keep it still long enough to see anything?
Your scope should have a smaller finder scope mounted to it. If not, lotsa
luck to ya. ;) You can try aiming with the lowest power lens (the 20mm)
and then try to swap in the higher power one, but that would be a pain.
Anyway, assuming you've got a finder scope mounted to it, find something
that's not moving like a lamp and center it in the main scope viewer (be
careful--stars don't look like they're moving, but at high magnification,
they definitely are--that's why I suggest a non-sky object like a lamp
post). Then use the little screws on the finder scope to adjust it so that
the lamp is centered there too. Now your finder will agree with your main
tube. To see Mars, just center it in the finder scope's crosshairs and it
should also be centered in the main scope.
> * When I use the different lenses, I think that the lower the number • the
> higher the magnification. Is this right, or is it the other way around? • I wear
> glasses; should I take them off to focus an image in? Are the focus • settings
> similar for each different lens, or will I need to exend the lens tube • farther
> and farther for each lens? Should I move the actual telescope tube • itself, and
> refrain from touching the lens tube?
I don't wear glasses, but I'm pretty sure unless you have a very strong
perscription that you don't need to wear them. If you're lucky, your
eyepieces are "parfocal" which means you shouldn't have to change the focus
while changing eyepieces, but don't count on them being parfocal.
> * Do I need a special camera adapter to take pictures of any images • I'm
> lucky enough to get? I understand that the images are upside down and
> flip-flopped, but believe that to be correctable with image-editing • software (or
> a very expensive (IMHO) correcting lens.
> Please share your experiences and advice with this poor lost • skywatching
> soul. Any help you can provide will be much appreciated. Thanks!!!
Yes, you'll need an adapter. Yes, things will be upside down, but it
doesn't much matter. If you saw a picture of mars, would you know whether
or not it was upside down? ;)
-- Tom
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Message is in Reply To:
 | | (not quite) Looking at Mars
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| Greetings, fellow .Spacers! A few years ago I went to Target and bought a little telescope from the toy section: a Discovery Channel telescope, 300 power, 50 mm; I forget the actual manufacturer's name, but it was a real telescope company, and this (...) (21 years ago, 16-Aug-03, to lugnet.space)
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