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Re: Just Received A Telescope And Was Wondering ??

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Posted by matt berger/">matt berger on January 17, 1999 20:20:53 UTC

: I hate to break it to you, but Tasco is not a very good brand for a telescope. If you really want a good one for a good price, get a Dobsonian Newtonian from a company like Celestron, Meade, or Orion (there are many other good companies, but those are the biggies). Now, assuming that you are aren't about to go out and spend another several hundred dollars, lets start with what you have. I'm not quite sure about the D=144, but I would guess that means diamater. Measure the frong of your telescope, if the D means diamater than the telescope should have a diamater (also called aperture) of 144mm, or about 6 inches. One question, is this telescope a reflector (does is have a mirror on the bottom and a the focuser on the side), or is a refractor (big lens in the front, focuser on the back of the telescope)? The F almost surely means focal length, or F.L., this is simply the measure of how far the light travels inside the telescope after being bent by the first optical surface before striking the eyepiece. Focal length is important in two ways, which I'll explain later. So F=900 means the light travels 900mm after striking the first optical surface. The "two small lenses" are undoubtably eyepieces. These are what you place in the focuser to make the light your telescope collects seeable by the human eye. The numbers on the eyepieces are the focal length of the eyepieces, and this is important, because along with the focal length of the telescope this determines your magnifaction. To figure out your telescope's power, take the 900mm and devide it by the focal length of your eyepiece, say you use the 20mm. This would give you 45x, things would appear 45 times bigger than they would to the naked eye. You can use this simple formula on any telescope: telescope's focal legnth devided by eyepiece's focal length equals the magnifaction. The more eyepieces you have the better, because you then have a wider range of magnifications to use. You have 45x and 225x, which is not a very good range. The final item you mentioned is a barlow lens, a very handy thing if they are good quality. On a Tasco, I personally wouldn't recommend using it. But here is what it does, it effectively doubles the number of eyepieces you have by either (depending on which way you look at it) doubling the focal length of your telescope or halfing the focal length of an eyepiece. Thus with the barlow, your 20mm eyepiece now becomes a 10mm giving you 90x instead of 45x, and the 4mm will become a 2mm giving you 550x instead of 225x. As to what you can see, well first off let me ask you this, how stable is the telescope's mount? Does it wobble around when you move the scope or stay pretty solid? If it wobbles, you could have a lot of trouble with it, but you can help this by hanging 2 liter soda bottles filled with sand evenly spaced around your scope (say three). This will help. Also, I'm assuming this a tripod you have and not a cabinet mount, so is one axis (direction of movement) angled up some or does one merely move the telescope in an azimuth (back and forth, right and left), and one move it in elevation (up and down)? Assuming the mount is fairly stable, then you can probably see the planets fairly well. Jupiter with show you its four main moons shuttling back and forth night to night, with some cloud belts visible on the planet its self and perhaps some detail within them (such as the Great no so currently Red Spot). Saturn will show its rings, and you might see Cassini's division with good seeing (a steady atmosphere). When looking I wouldn't recommend using the barlow with the 4mm eyepiece, in other words don't go much over 200x. Every telescope has a limiting practical magnification, which is a factor of the quality of the optics, aperture, and how steady the atmosphere is. Anything higher and most of the time what you see will be too dim and fuzzy to really show and anything. However you have to know where in the hell these things are, to put it simply if you are in the northern hemisphere, then Jupiter will be dominating the south-eastern sky as night falls, big and bright, the brightest "star" in that part of the sky. Saturn is less obvious, down to the lower left, but shows its self as a bright golden star which should he well up not to long after dusk. To find other stuff, such as nebulas and galaxies and so forth, you will have to get a star atlas and planisphere. A planisphere is a disk shaped thing that you set to your date and time, then you stand facing a certain direction and compare what you see in the sky to the stars and constellations on the planisphere and with that you can find your way around the sky. The star atlas is a more detailed, showing stars down to the very limit of what your naked eye can see (and often beyond that) but they oftne plot the constellations and show you where deep sky objects are (galaxies, nebulas, star clusters, a deep sky object is simply someting beyond our solar system). I am going to point you to a couple of websites now, in hope that you do go there and learn more. The first is http://www.skypub.com/backyard/backyard.shtml which is Sky and Telescope's (an astronomy magazine) excellent guide to getting started in astronomy. They have advice on everything from buying telescopes to what to look at and so forth. The second is www.oriontel.com, this is Orion Telescope center, a company. They too have an good guide for starting out in astronomy, but also I highly recommend that you go into their online catolog or request a free paper catolog and get the "Seasonal Star Charts" star atlas which also includes a planisphere on the front. A very handy thing, I've had mine for years and it is literally falling apart from use. It's about $20. I hope all this helps you out, and feel free to email be back with whatever other questions you might have. I am a fountain of information on this subject.

: Clear Skies, : Paul Rest

: : : I have just been given a telescope and having no idea whatsoever if it is a good one I though I would call on the experts and ask. : : The telescope I have is a Tasco 302012 : : It has some other numbers on it that have no meaning to me but they are D=144mm F=900mm. : : It also has two small lenses and a thing called a Barlow lens x2. The lenses have the following H20mm and SR4mm. If someone could let me know wether a) this is an okay telescope and also b) what I might be able to see using it. ie planets, stars etc. And finally (sorry lot of questions) is what is a good software package that will tell me where to point it and what I am looking at. : : Once again I thanks for any and all help that you guys (and gals) could give me. : : Bill Carr

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