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ildi
2003-Nov-19, 02:46 PM
Hoping someone can recommend as I dont know anything about telescopes. Would like to buy hubby one for Christmas. Nothing too expensive but nothing too cheap either. What is the difference between a reflector telescope and a telescope? I was looking at some on the home shopping channel

Any suggestions at all appreciated! Thanks.

gkiser
2003-Nov-19, 03:53 PM
Hi ildi. I believe the biggest thing to consider is the apperature of the telescope. That just means how big of a light bucket you want. Basically, the apperature is the size of the opening that the light will pass through. Obviously the bigger the opening the more detail you can see and thus the higher you can magnify the image.

There are 3 kinds of telescopes; (1) Refractor; (2) Reflector; (3) Schmidt-Cassigrain.

REFRACTORS: A refractor is the kind most people imagine, you point one end up at what you want to look at and look through the other end. Light passes through lenses and is "refracted," thus the name. If apperature is what you are after, these are the most expensive per inch of apperature. I would never recommend buying a Wal-Mart brand one of these. They boast of high magnification, but the fact is that high magnification is not the only thing to consider. If you gather little light (small apperature) then it doesn't matter how much you magnify it, it will still be fuzzy. A good rule of thumb is you can magnify things to about 50x for every inch of apperature. So if the refractor says it is a 2" apperature, then 100x is about as much magnification as you can use and still get a good image. So their boast of 400x magnification! is just a sales gimmick. Since light bends as it passes through glass (refraction), then these telescopes should have corrective lenses on them. I think this is mainly what makes them more expensive.

REFLECTORS: A reflector is the one that Isaac Newton basically invented. It is rather odd to the first-time telescope buyer. Imagine a cylindrical tube that is open at one end. At the other end down inside it is a concave mirror. You point the open end at what you want to see; light passes into the tube and reflects off the concave mirror which focuses the light (because it is curved) on a smaller mirror (called secondary mirror) that is suspended in the middle of the tube back up near the open end. This secondary mirror reflects the light to the side of the tube where there is a hole and your eyepiece lens. Thus you are not looking through one end like the refractor, instead you are looking directly through the SIDE of the tube that is pointed up at what you want to see. These telescopes are the least expensive per inch of apperature! They make great first telescopes because you can get rather large ones for cheap prices. I would recommend a reflector as a first-time buyer.

SCHMIDT-CASSIGRAINS: These are really compound telescopes in that they have mirrors that reflect and lenses that refract. They basically use the advantages of both reflectors and refractors. They are very compact (small) but usually expensive. They are usually for the more experienced and are best suited for astrophotography.

Each of the above telescopes can come on 1 of 2 styles of mounts; (1) Alt-Azimuth; (2) Equatorial.

ALT-AZIMUTH: This stands for Altitude-Azimuth. If you don't know what that means; well, if you are standing outside facing say, the moon and point to the horizon; when you raise your finger straight up, that is altitude. The horizon would be at 0 degrees; directly overhead would be 90 degrees. Lets say you are now pointing north. The amount you have to swing your arm around to the right away from north in order to point to something on the horizon is azimuth. If you are first pointing north, then 90 degrees azimuth would be directly to your right; or east. Therefore an alt-azimuth mount is simply a mount for the telescope that allows this simple up/down, right/left motion. These are the simplest mounts; require no "setup" time and are generally very sturdy and cheap. For a first-time user, I would definitely recommend one of these. As you may already know or can imagine, objects in the night sky move. So if you are looking at them through a telescope that is fixed, then things that you view in the telescope drift out of view unless you can move the telescope along with the object. This motion is, of course, caused mainly by the rotation of the earth. The DISADVANTAGE of alt-azimuth is that you have to move the telescope in two directions (up/down and right/left) to follow a moving image you are looking at.

EQUATORIAL: This mount is kinda strange to the first-time telescope buyer. It is especially designed to follow objects in the sky by only having to move one axis (right/left). In order to do this however, it has to be set at an angle that, believe it or not, directly corresponds to the geographical latitude you are observing from. In other words, it requires "setup" time. (Most people use the North Star to set their equatorial mount up; because, whether you know it or not, the North Star generally stays in the same place in the sky and all the other objects appear to rotate around it. It is like a the center of the pinwheel which is the sky). The advantage to this kind of mount is that you can get a motor that would move the right/left axis with exactly the speed of the rotation of the earth. Or if you don't have a motor to drive it, then you would manually only have to move the telescope in one direction instead of two like the alt-azimuth. This is great for astro-photography because in order to photograph objects in space it sometimes requires long exposure times for the camera, and the object would paint a line on the film unless the telescope moved along with the rotation of the earth. Get it? The disadvantages are of course that it requires setup time everytime you use it and it is generally more expensive and not as sturdy as the alt-azimuth (easily bumped and vibrates).

My recommendations: A Newtonian reflector on an alt-azimuth (or sometimes called a Dobsonian) mount.

Specifically, Orion and Meade make many telescopes starting at about $200 all the way up to over $1000. You can go to their websites and find excellent deals.

My first telescope was a 4" Newtonian reflector on an equatorial mount. I didn't like having to set it up every time I wanted to use it. I sold it and bought a 10" reflector on a Dobsonian mount. I still have this one! It is great. I use it quite often.

One other important thing. In order to get different magnifications for you telescope you have to buy an assortment of eyepieces. These can be rather expensive no matter where you get them. Most telescopes come with ONE eyepiece. You have to buy more to get more magnification options. Basically the way you figure out what to by is a simple formula. The focal length of the telescope divided by the focal length of the eyepiece is the magnification. For example if the telescope's stated focal length is 1000mm and the eyepiece you are using is 25mm, then 1000/25 = 40x is the magnification. So to get higher magnification I must by smaller focal length eyepieces. For the same telescope if I bought a 10mm eyepiece then; 1000/10 = 100x magnification.

Another point I would like to share. Some people THINK they are interested in astronomy and telescopes because they have been inspired by the colorful pictures they have seen. These color pictures of nebulas and planets are kinda deceptive. When you look at them with your telescope you will not see the colors as vivid. In fact it is very difficult to discern ANY colors at all. For this reason I actually started my astronomy hobby by buying some big apperature binoculars especially for night sky observing. These were very cheap compared to a telescope and with them I learned my way around the stars and the interesting things to observe. So, you might want to consider buying some binoculars first before actually throwing down the cash for a telescope. Just an idea.

I know this is a lot to absorb, but I wish I had had someone to explain this stuff to me when I was looking for my first telescope!

Hope this helps!

Greg

Menikmati
2003-Nov-19, 06:26 PM
Hi Ildi,

I have been looking for telescopes for about 2 weeks now and I think I have narrowed down to an Orion skymaster xt8 (http://www.telescope.com/shopping/product/detailmain.jsp?itemID=14855&itemType=PRODUCT&iMainCat=4&iSubCat=8&iProductID=14855) its a very nice scope with the adition to upgrade to the intelliscope. Also I have learned a lot about telescopes from this website http://stargazer.isys.ca/f8deluxe.html I hope this helps. Also these websites were refered to me by Dave Mistky so don't give me full credit. I wish I was your husband and getting a telescope for christmas :P. Good luck

ildi
2003-Nov-20, 03:14 PM
Thanks so much for all this useful info. I am definitely confused but maybe the binoculars are the way to go. Which would you recommend? Also, do you recommend the Starry Night Pro Plus software? Is that to be used with a telescope or is it just for browsing for interest? Thanks again, good luck to all with your Xmas shopping!

Menikmati
2003-Nov-20, 04:43 PM
ildi I have a question, is your husband familiar with the night's sky? The reason I ask is because if this is new to him then you may want to get him a nice pair of binoculars to get familar with the all the objects in the sky and then get a telescope. If you decide on binoculars make sure you get at least 7x50's, I have a pair of 8x40's and they work pretty well. The first number is the magnifaction and the second number is the peripheral vision.

DippyHippy
2003-Nov-21, 01:40 AM
I recommend the Starry Night Pro software but please please please make sure you have more than the minimum system requirements before you buy it... if you don't have enough memory on your video card, it will crash constantly.

That said, it's a beautiful program but if you're quite new to astronomy, you might want to consider Starry Night Enthusiast or Astronomy Plus instead - both are available from the main Starry Night (http://www.starrynight.com) site.

BobbyD
2003-Nov-21, 03:04 AM
Grab yourself a copy of the latest Orion telescope catalog!It includes several mini-lessons to explain differences in telescopes,eyepieces,and other equipment!!I own an Orion StarMax 127mm...which is a 5"f/12 maksutov-cassegrain.I love it and it gives GREAT images of the Moon and planets.Oh yes, it doesn't do too badly on the brighter deep sky objects. It's simple and has a back to basics quality;none of this confusing computerized stuff that tries to do everything but observe for you.The 'old school' way to observe...find everything yourself,helps you learn your way around the sky!! And you can't beat this...prices are just right!!

ORSkywatcher
2003-Nov-22, 09:31 AM
Ildi,

While there are tremendious values available in telescopes today, I am loth to recommend one to you over the 'net. I'm the president of my local astronomy club.and I strongly recomend that you locate your local astronomy club and attend some "Star Parties" . Star Parties are get togethers to view the night sky. Usually you will find several differant types of telescopes as well as differant apatures (sizes). Also people love to share their hobby. They will be a big sorce of information about using his new gift.

Look through them and use them and you will begin to get a feel for what you like. Computer controled "goto" scopes will trak and find almost anything you want to view, however some (especially inexpensive models) can be a challenge to set up and align.
Dobsonian reflectors offer great value for the money. Lots of apature per dollar, but they often lack traking or goto functions.

How does your husband intend to use his scope? The moon and planets? Nebulas, star clusters,or galaxies? Does he want to be able to use it to view terestial objects as well? Will it only be used in the backyard or would you like to take and put it in the car and go to a dark sky site away from the skyglow of the city? I know this is an alot to consider but you are planing to buy an expensive piece of equipment that will bring years of enjoyment if you find the right one.

Stay away from department/discount store scopes that quote how powerful their magnification is. Apature is much more important. The larger the apature the more light you collect. Telescopes are light buckets. The wider the buckets opening the more light it can catch. Find one that uses 1.25" eyepieces at hte least. The ones with .965 eyepieces tend to be bottom feeders with low quality optics. Prices can range from $150-200 dollars to several thousands. Once you decide on whitch scope you want make sure to include a visit to your local astronomy club's meetings. A scope can be a daugnting experience to set up your self. I fumbled around with my first scope for months until I found the local club. A little help from them and I was hooked for life. Prior to that I was ready to put it away in a closet as I was constantly frustrated with it.

Good luck and clear skies.

Mike
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