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Stargazing Telescope not Magnifying.

  1. Dec 25, 2008 #1
    Im a Physics student at UNC-Charlotte. I just got my first telescope and I already have a problem. I can pinpoint a star and see it but it looks the same size as it does to the naked eye. I changed eyepieces and everything. Still just a tiny little dot.

    Does anyone know what could be wrong with it?
     
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  3. Dec 25, 2008 #2

    russ_watters

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    Stars (except the sun) are much too distant to see as anything more than pinpoints even in the biggest telescopes. I'd start with Venus - it's the brightest thing in the western sky right now, just after sunset.
     
  4. Dec 25, 2008 #3
    Venus is the first thing I tried to look at. Everything I got in view was the same size.
    Venus was the same size as every other star.
     
  5. Dec 25, 2008 #4

    Vanadium 50

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    Let's try the moon. That should be obvious whether you are magnifying or not. (And I suspect you are)

    Venus will not be very large in a small scope. What a scope will let you do more easily is to notice the phase of Venus. If it's focused, you should be able to see that Venus is not exactly round. I'm not 100% sure what the phase of Venus is now - I think it is gibbous, which means it will look round but lopsided.

    A quick calculation tells me the size of the disk of Venus is somewhere around 12 arc-seconds. The moon is about 2000 arc-seconds across, so you would need a substantial magnification for Venus in the scope to have a disk as large as a naked-eye moon.
     
  6. Dec 25, 2008 #5
    Thats my plan. Sadly, the moon is not visible now. I will have to wait a few days.
     
  7. Dec 25, 2008 #6
    Give us some details about your telescope such as objective and eyepiece focal length.
     
  8. Dec 25, 2008 #7
    Its a Brand New Celestron 130 SLT. I start out using the 25mm eyepiece and then I moved up to 12.5 and 9mm but they all gave me the same view, just a little dot.
     
  9. Dec 25, 2008 #8
    as stated earlier, I tried viewing Venus at about 6:15 ET. This thing is supposed to show venus up close and personal. Like viewing gases and different color variations. Not just a little bright spec. I went all the way to the 4mm which is the strongest in my set and there was no difference from the 25mm.
     
  10. Dec 26, 2008 #9
    I am guessing that maybe you don't have it pointed at Venus. As Russ said stars will be points of light no matter the magnification.

    Try a surface object such as a distant building. It will be upside down (unless you have an erector lens) but will confirm magnification.
     
  11. Dec 26, 2008 #10

    russ_watters

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    Well, it could still just be a problem of expectations. Viewing through the atmosphere (Venus is low in the sky), the resolution isn't going to be very good and you won't be able to see any surface (cloud) detail.

    Venus is 20 arcsec in diameter right now and the resolution you might get on a clear and calm night is about 1 arcsec - like a photo that's only 20 pixels across. Your setup, with a 4mm eyepiece, works out to about 162x magnification, which is good for what you are doing, though if they gave you a Barlow, I'd use that with the 9mm (or bigger) to get a wider field of view that is easier on your eyes.

    I'm still not convinced you were looking at the right object, though - I see your scope has GoTo - were you using that to aim it or did you aim it manually? Identify Venus with your naked eye and make sure you really do have it in the field of view (at low magnification). Align your finderscope during the day to make sure it is aligned with the scope. Venus should be so bright in your scope at low magnification that it almost hurts your eyes.

    Attached is a photo of what it should look like through the 4mm eyepiece right now.
     

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  12. Dec 26, 2008 #11

    russ_watters

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    One of the problems with people's first scopes is they they have no idea what to expect and so the expectations are filled-in by advertising or by newspaper photos taken by the Hubble or other spacecraft. Sadly, the reality is not so good.

    Your telescope has a good focal ratio (low number = bright) so you should next try a few nebulae and star clusters. Suggestions (in order of importance/difficulty):
    The Pleiades (M45) - east after sunset
    The Orion Nebula (M42) - east after sunset
    (those you can see with the naked eye - these you can't, so make sure the telescope is aligned well:)
    Pegasus globular cluster (M15): west after sunset
    Ring Nebula (M57): west, just after sunset


    Saturn rises at 11 and is high enough to see around midnight. Including the rings, it is twice the apparent diameter of Venus and you should be able to see at least one bright moon, perhaps more. The rings are almost edge-on this year, though, so you won't see much of them until the spring.
     
  13. Dec 26, 2008 #12

    Vanadium 50

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    Russ, where is Jupiter now? The Galilean moons were one of the first things I could see that wasn't visible with the naked eye, and I certainly enjoyed that. The other nice thing about them is that they visibly move from night to night. (Although figuring out which one is which isn't always simple.)
     
  14. Dec 26, 2008 #13
    This is a nice website with a real time star/planet chart. You can customize it to your location.

    www.heavens-above.com

    Jupiter sets in the southwest soon after sunset.
     
    Last edited: Dec 26, 2008
  15. Dec 26, 2008 #14
    Thanks for the tips guys. Im sure it is something that Im just ignorant to right now. I will try just looking at a far building and hopefully the moon will be visible tonight! Thanks Again.
     
  16. Dec 26, 2008 #15

    russ_watters

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    Unfortunately, it's about the worst time for Jupiter: it disappears into the evening twilight and will pass behind the sun next month. It's a good four more months until it starts to get back into a decent position to view, late at night.
     
  17. Dec 26, 2008 #16

    russ_watters

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    If you have a clear view of the western horizon, you may catch a sliver of it just after sunset Sunday night. After that, it'll slowly climb higher in the western sky at sunset. I encourage you to watch it a few nights in a row to see how it changes from night to night. The edge of the shadowed region is where you see the most detail.
     
  18. Dec 29, 2008 #17

    Vanadium 50

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    Did you try it tonight?
     
  19. Jan 1, 2009 #18
    Thank goodness for this thread. I also have a new Celestron 130 and was surprised stars weren't magnified. I'm glad to find out it's just my newbie misconceptions. I've just moved to Tucson, and the clear skies were my main motivation for getting into astronomy. I'll be looking forward to my first view of the moon in a few days.
     
  20. Jan 1, 2009 #19

    HallsofIvy

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    You should be aware that the primary purpose of an astronomical telescope is light gathering, not magnification. All light that falls on the primary (mirror or lens) is focused into your eye and so the light gathering power is proportional the square of the radius of the primary.

    The magnification depends on the focal length of the primary divided by the focal length of the secondary lens. Typically, because the radius of the primary is fixed, you need a secondary with a shorter focal length to increase the magnification. Of course, that makes it harder to focus.

    The "resolving power" of a telescope is proportional to the radius of the primary. If two points on, say, the moon, are within the resolving power, you will not be able to tell them apart no matter how much you try to magnify. Stars are so far away they are well within the resolving power of any telescope. No matter how much you try to magnify a star it will look like a point of light. (Actually, since no telescope is perfect, a star will show as a small "blur", the better the telescope, the smaller the blur. Increasing the magnification will just enlarge the blur. Except to see star fields, like star clusters, there is no reason to use high magnification to look at stars.)

    Looking at planets or the moon is a good reason to use high magnification (short focal length secondary lens) but, as I said, it becomes harder to focus and there is no point in magnifying beyond the resolving power of the telescope.

    By the way, the fact that stars are points and planets are disks is the reason stars "twinkle" and planets don't. When I first was told that stars "twinkle" because of the atmosphere, that made no sense to me at all. After all, the entire atmosphere is between the earth and both stars and planets- and planets don't "twinkle"!

    But stars are "points of light". Any slight tremble in the atmosphere will affect the light and make it "twinkle". Planets are not. Even with the naked eye, though we don't see it clearly, planets are "disks". A change in a tiny part of the atmosphere won't affect any but a small portion of that disk so we do not see an appreciable change in the brightness.
     
    Last edited: Jan 2, 2009
  21. Jan 2, 2009 #20
    Its all good now! The moon finally came out and I got some great views of it!
     
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