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cmosdes
2002-Jun-01, 11:23 PM
I was just given what looks to be a very old telescope, but it looks to be in great shape. It came in a nice solid wooden carrying case with all the pieces, but no instructions on use and setup. I'm hoping some people here can give me some clues on how to make the best use of it, or tell me if it has any usefulness at all. I'd really like to be able to see the rings of Saturn, at the very least.

First, on the scope itself is written:

SEARS DISCOVERER model 46333
Equitorial Refractor
F = 900mm D = 60mm

The F and D appear to be the focal length and diameter of the scope.

There are several lenses which come with the scope, marked as follows:

Ke22mm
6x30mm
SR4mm
HM9mm

It also has something called a Barlow Lense. A quick web search indicates this might be inserted to increase image size or magnification. I'm not sure about this, though.

There is also somehing called an "erecting prism" which I'm not sure how it works, but the name implies it just flips the images 180 degrees.

There are also a "moon" and "sun" filters, which screw into the bottom of the eye pieces. The moon filter puts a green hue on everything, and the sun filter makes everything too dark to see anything. Obviously I have no intention of pointing the scope at the sun, filter or no, but I was wondering what these are intended to do.

So, my questions are:
1) What would be a guess as to what I could resolve with this scope?

2) What are the different eye pieces designes to be use for?

3) How do I make best use of the barlow lense and erecting prism?

4) How do I best use the moon and sun filters?

Thanks to everyone for any and all advice!

ljbrs
2002-Jun-02, 12:23 AM
cmosdes:

I am not a great fan of department store telescopes (my first telescope was one). HOWEVER, DO NOT USE THE SUN FILTER WHICH SCREWS INTO THE EYEPIECE. YOU MOST PROBABLY WOULD GO BLIND FROM SUCH USE.

The only reason I answered this was to warn you about the use of sun filters over the EYEPIECE. NEVER. EVER.

I will let the telescope pros discuss the other topics with you.

ljbrs

_________________
*Nothing is more damaging to a new truth than an old error.* Goethe

<font size=-1>[ This Message was edited by: ljbrs on 2002-06-01 20:26 ]</font>

ljbrs
2002-Jun-02, 12:25 AM
cmosdes:

Oh yes, it might help for you to visit an astronomy club. The amateur astronomers could give you good advice about telescopes.

ljbrs /phpBB/images/smiles/icon_smile.gif /phpBB/images/smiles/icon_confused.gif

_________________
*Nothing is more damaging to a new truth than an old error.* Goethe

<font size=-1>[ This Message was edited by: ljbrs on 2002-06-01 20:26 ]</font>

JimB
2002-Jun-02, 12:28 AM
This sounds like a traditional beginner's scope. The wood box sounds interesting cause everything nowadays is in cardboard.
You are correct in all your guesses. The diameter of 60mm is pretty small, a typical first scope. With that much aperture you should get great detail out terrestrial viewing and the moon. Seeing the rings of Sarturn and cloud belts of Jupiter is possible, IF the mount is steady enough. You don't describe the mount so you may need an adapter to put it on a camera tripod. Not too bad a way to use it. The focal length is just like with camera lens (if you're familiar with them), 50mm is considered about 1x (or 1 power). This scope is 900mm, so the magnification the scope body gives by itself is about 18x. But adding an eyepiece can greatly increase the power of the scope. To figure this you divide the F of the telescope by the F of the eyepiece, so:
22mm Kellner = 41x
9mm Huygens = 100x
4mm Ramsden = 225x
and most Barlows are doublers and would double the power of each eyepiece.
BUT, the aperture is so small that most of the magnification these give are wasted. A general rule is 1x per mm of aperture (for average nights) or as much as 2x per mm (on very clear nights with very stable air and a stable mount). So this small scope should perform well up to 60x and occasionally up to 120x. Very common in the past and still today to include eyepieces you can never use which leads to lots of frustration. Stick with the 22mm and the Barlow for most of your observing and the 9mm on occasion. Saturn's rings need about 75x to 90x to show up well.

RE:
1) See above.

2) See above. All the eyepieces are similar in quality, it's their magnification that will make them "good" or "bad". The 6x30 should be a finderscope that mounts to the side of the telescope. "6" is the magnification and "30" is its aperture in mm. The idea is to line up the finder and the low power eyepiece in the scope on something a mile away or more. Then use the finder (very low power) to locate the object you want to view, use the low power 22mm to frame the object and then drop in the Barlow or other eyepiece for a close-up view.

3) You take out the eyepiece, drop in the Barlow, and then place the eyepiece in the Barlow -- very simple. The erecting prism is for daytime viewing of wildlife and nature.

4) If the sun filter is small (meant to be screwed into the bottom of the eyepieces) THROW IT AWAY! These are very dangerous. The only safe sun filter is attached in front of the main lens to block out the energy before magnification. These little ones have a history of melting or cracking and destroying eyes. The moon filter is very useful. The moon is so bright that it can be washed out in a magnified view. So you screw in the filter and get better contrast and can look for hours trying to describe all the features you see.

Clear Skys,

Tim Thompson
2002-Jun-02, 12:35 AM
As you have guessed, 60mm is the telescope aperature, and 900mm to focal length, which makes it an f/15 focal ratio, pretty much standard.

1) What would be a guess as to what I could resolve with this scope?

Well, the rings of Saturn certainly will be easily visible. Long f-ratio refractors are particularly good for planets. This is the smaller of the most common sizes for a refractor, 60 & 80 mm.

2) What are the different eye pieces designs to be use for? 3) How do I make best use of the barlow lense and erecting prism?

The eyepiece number is its focal length, if I am not mistaken. The larger the number (i.e., the longer the focal length), the wider the field of view & the smaller the magnifying power. The 22mm (41 power) & 30mm (30 power) eyepieces should work well on that telescope. But I would think the 9mm (100 power) & 4mm (225 power) eyepieces are useless, as the telescope is really too small to support such high magnification (especially without a clock drive). Likewise, the Barlow is not likely to be useful. The erector prism is for looking at earth bound things, so you aren't weirded out by seeing everything upside down. However, for astronmomy, upside down & rightside up don't make much difference. I would say don't bother, unless you want to look at trees & birds, or in windows.

4) How do I best use the moon and sun filters?

You don't use the sun filter at all. Telescopes were packaged that way when I was a kid, but the fully concentrated light of the sun can break or melt the filter. When that happens, the fully concentrated light from the sun will break or melt your eyeball, and you can sue Sears. A proper sun filter goes over the front end of the telescope, where it gets the sun before it is concentrated by the 60mm lens. Sometimes another special filter can sit at the eyepiece end, behind a filter over the front. As for the moon filter, try it. The worst the moon can do is steal your night vision. Probably best for viewing when a substantial fraction of the moon is illuminated.

The best thing you can do, in my opinion, is to find a local amateur astronomy club. You can search the Sky & Telescope club directory (http://skyandtelescope.com/resources/organizations/) and find the amateur club or society that is most convenient for you. The best way to get help learning about your telescope is to set it up with people who can show you face to face, hands-on, what to do & how to do it best. That's a lot better than trying it by WWW remote control.

cmosdes
2002-Jun-03, 06:06 PM
Thanks to everyone that responded! We (my bro and I) took the telescope to a local hilltop and pointed it towards what I was sure was Jupiter and Venus. The spotting scope was useless, but I did manage to find the two planets anyway.

I can't say I was impressed with what I saw. Even with the highest magnification (4mm lense), these didn't appear to be all that impressive, but I'm certain that was my inability to make out what I was seeing and partially the scope. It was not very steady and not clear at all. Worse, it would rotate through the viewing area in less than a minute, making it difficult to keep it focused.

I do plan to contact the local astronomy club and hook up with them and maybe get a few more pointers. It might be onto a bigger and better scope after that. In the meantime, I'll wait for a full moon to see what I can see with this scope.

Tim Thompson
2002-Jun-03, 07:41 PM
Better to look at the moon when it's not full. Just concentrate on viewing the "terminator", the boundary between night & day on the moon. Remember, you are looking "down" (relative to the moon) onto the surface, with long sunset (or sunrise) shadows. You will see a lot more detail, and spiffy things like the peaks of mountains lit by the sun, when the rest of the mountain is still in shadow.


Shallow Sky (http://www.shallowsky.com)

ljbrs
2002-Jun-04, 12:58 AM
See! I told you so! There are a lot of very knowledgeable people at this site. They gave you some very good advice. I would not worry about the fact that you cannot get images like larger telescopes. But when you are looking through your telescope, you are viewing the real thing LIVE! Just being able to find the various interesting objects in the night sky is quite an accomplishment, and those with such knowledge are invariable at the tops in the ranking of amateur astronomers in their amateur astronomy clubs.

Incidentally, you can treat this site (Bad Astronomy) as a kind of astronomy club, because so many of the people who post here are extremely knowledgeable about astrononomy. If they are not correct, the ones who are knowledgeable will let them know (gently, of course) Nastiness is banned at Bad Astronomy, because it is bad behavior. Bad Astronomy is not ad hominem heaven!

So have fun with the scope. Join an astronomy club so that you can sample the various scopes belonging to the members. That will help you when it comes time to buy one for yourself.

I have a small catadioptric telescope. I also like using hand-held binoculars, because they permit me to move and quickly observe different parts of the sky. Portability is an asset.

So learn to enjoy your small PORTABLE scope. Find out what it is best for observing and be satisfied with learning how to survey the night sky.

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ljbrs
2002-Jun-04, 08:34 PM
Incidentally, I just love looking through the telescopic monsters belonging to the guys in my wonderful astronomy club. We have regular open houses for the public before and after the new moon (best time for viewing, if skies are clear).

I do not have to drag the beasts around to set them up, and while I do not get the privilege of operating my own scope in such a situation, most of the guys in my club let me try their scopes out for myself. If you find the right club, you will find the members willing and eager to let you use their monster scopes. They like to show them off.

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