|Aug18-03, 02:04 PM||#1|
Mars Watch: Where is the Red Planet Now?
|Aug19-03, 07:41 AM||#2|
I've been keeping my eye on mars, watching it through my telescopes. Even now, at only moderate magnification, I can make out the glow on the edge of the disk of the polar ice caps. It's going to be great. They say at only 75x magnification it will look as big as the moon does to the naked eye!
Even for those who don't know anything about astronomy, it is very easy to find. In the Northern Hemisphere, watch the path that the moon has been following (across the Southern sky) and it will be near that (except that it will rise before the moon does) and look like a bright orange star rising over the East horizon of North America at about 10:30 (slightly earlier each night). Until the moon rises it will be the brightest thing in the night sky.
|Aug20-03, 03:16 AM||#3|
I've been having a look at it
every night the past couple weeks
just with the naked eye. It is
as bright as Venus usually is but
has the faint reddish tint.
Considering what Artman said it
sounds like it might be a worth-
while investment to get a tele-
|Aug20-03, 10:21 AM||#4|
Mars Watch: Where is the Red Planet Now?
If you think you are more than mildly interested, don't buy a "trash scope." The type sold in department stores for less than $100.00 with aperatures of 60mm for refractors and 80mm for reflectors and .965" eyepieces. These scopes claim high magnification, (which they cannot resolve), are cheap, difficult to focus, have poor finderscopes, sometimes plastic optics, very little eye relief in the eyepieces and are generally not a very good investment.
The most important thing is aperture. This is what determines how much you will be able to see, how much light your scope can gather.
For a first telescope that can grow with you, I recommend either a 80mm or 90mm refractor f5 for star patterns, f8 or higher for planets and the moon.
Or a 114mm or 150mm Dobsonian or equatorial mount reflector. These are generally about f6 to f8 and are good for all around viewing.
The 114mm Dob. is probably the ideal first scope. It can resolve up to 273x magnification and can show several galaxies and all of the Messier Objects and can be purchased from a decent manufacturer for about $200.00.
I also recommend a red dot finder, 1.25" eyepieces in at least two sizes (25mm and 10mm are decent) and a good 2x or 3x Barlow (the barlow doubles or triples the magnification of any eyepiece).
Sorry about the lengthy response, but a lot of people get really frustrated with astronomy because of poor equipment, when for a few bucks more they can get a decent starter scope that they can enjoy for years.
Here are the names of some of the less expensive, high quality scope manufacturers: Orion, Celestron, and Meade.
|Aug21-03, 12:31 AM||#5|
Thanks for the rundown. Info like
this is PhysicsForums at its best.
I was actually thinking along the
lines that any old telescope would
be better than the naked eye so
it is good that you warned me this
woudn't be the case.
I'm definitly not into it enough
to spend $200. for the minmum
good one. Armed with your info,
though, I might do some looking
for a used one. I get the urge
to peer up now and then when some-
thing like this is going on. Last
time it was a lunar eclipse that
made me wish I had a telescope.
|Aug21-03, 08:40 AM||#6|
There is an inexpensive alternative. Build one yourself. Dobsonian mounted telescopes can be made for less than $100.00 fairly easily. Ebay has cheap mirrors for telescopes. You can get a 4.5" (114mm) telescope mirror for about $10 plus shipping. This price is about 1/4 of the price you find elsewhere, the catch is that these are 1/4 wave and that should be the total for the entire optical system, so you need a high quality secondary mirror, 1/10 wave or better, and decent eyepieces. Add another $10-$15 for a 1.5" secondary mirror (Orion sells these in 1/10 wave or better) and buy some hardware for the mirror cell, and diagonal, pickup some eyepieces from Surplus Shed and you can have a decent telescope for less than $100 and a few hours time.
There are sites all over the internet that show instructions for building one.
You could build a 70mm refractor (not too bad, better than the department store 60mm models) using a 70mm objective lens, a 1.25" focuser and 1.25" star diagonal and a couple of eyepieces for about as little as $60.00 from Surplus Shed (great surplus internet store, lots of great deals on optics and cheap shipping).
Check them out here: http://www.surplusshed.com/
Let me know if this sounds interesting to you I can help you find more infomation on the process.
I've built two reflectors, a 6" (150mm) and a 4.5" (114mm) and a copier scope (only 60mm, but with a short focal length so it is much better than a trash scope) that I threw together for only about $40. (The copier scope is excellent for it's size at star viewing because it has such a short focal length, but is not great for the moon or planets. Good travel scope though as it is only about 12" long and attaches to a photo tripod).
|Aug22-03, 07:11 PM||#7|
Thanks for the idea and the leads
to sources. It may come to that.
Actually what I have in mind is
to keep my eye open at the big
weekend swap meet (or flea market
as they may call them where you
live) for something in the range
of what you reccomended as decent.
I went today and a guy had a
scope he was asking $40.00 for.
He said it was $150.00 brand
new so I figure it actually cost
him $100.00. I could probably
have talked him down to $30.00
but thanks to you, I realized it
wasn't a decent scope.
I will just keep going and be on
the lookout. It is quite a large
swap meet and is held every week-
end. I've frequently noticed
telescopes there. It's a common
thing to be able to buy stuff in
decent shape for a quarter of the original price.
What is a Dobsonian mount, by the way?
|Aug25-03, 10:03 AM||#8|
A department store scope for $30.00 is okay if the optics are decent, coated and not plastic and If the scope uses 1.25" eyepieces. You can make minor changes for a few dollars that make a scope that cheap usable. Swap meets are a great place to check for telescopes.
Here is a great site to check out if you do want to go with the swap meet find:
A dobsonian mount is a box that sits on the ground on a swiveling base, is open on the back so the scope can swing into it and has semi circles cut into the top to hold the scope cradle rocker arms. It follows the altitude changes with the rocker arms and follows the azimuth (horizontal) changes with the swiveling base. They are cheap and easy to build. I built one yesterday in about two hours for about $10.00 for my 6" scope.
|Aug25-03, 08:43 PM||#9|
Wait-shouldnt this be in the Astronomy forum?
|Aug27-03, 01:22 PM||#10|
|Aug27-03, 02:30 PM||#11|
I searched the Dobsonian mount
and found a gazillion plans. I
have all the woodworking machines
a guy could ask for and this
is not a difficult thing to make.
That being the case I became at-
tracted to the larger scopes. It
is not more work to build a ten
inch, just more material.
People seem to refer to the lenses
(mirrors) in inches but you gave
You speak of 1/4 and 1/10 wave
mirrors. This refers to quality
of light gathering?
There was an excellent Meade for
sale at the swap meet on Sunday
but when I started looking at it
the guy told me it was already
sold. I'm thinking that the middle
of a much advertized celestial
event is not the best time to shop
for used telescopes.
|Aug27-03, 03:33 PM||#12|
I think you're right about having trouble buying a used scope right now.
The 1/4 wave, 1/10 wave and diffraction limited refers to the ability to resolve the gathered image.
If you're a woodworker, then building is definitely, a great option. The large scopes (10" and bigger) have great light gathering capability, however, there are a few drawbacks to consider they are bulky to transport, hard to store, difficult to collimate, don't work as well as you might think during poor seeing conditions (they have to look through a larger column of air then smaller scopes), and require a commitment to setting up ahead of time to use (long cool down period and just take longer to set up), and the mirrors are very expensive or require many hours of labor to make by hand (although they say this is very rewarding process, I've never done it).
But if your interest is in what they call the "faint fuzzys" (the galaxy's and nebulas) then a large scope can show you details during periods of good seeing that you will never get from a small scope.
A good compromise size is an 8" or 10" Dobsonian.
zoobyshoe, you have aperture fever (the disease that makes you long for bigger aperture scopes) and you haven't even bought a telescope yet!
A good pair of binoculars (8x50, 7x35) is a good astronomy starting point as well. You would be surprized at the number of stars that show up that you didn't even know were there. Globular clusters are great in Binoculars. Super Nova hunters use binoculars all the time. They aren't too good for planets though.
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