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Trouble locating objects in the sky
Last post 10-15-2008 04:35 PM by WannaB. 6 replies.
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  • 10-13-2008 08:51 AM

    Trouble locating objects in the sky

    Hello

    I have a 10" Dob and everytime I point it towards the sky to locate any object (such as a star), I am toally lost. I can see the constellations with my naked eye and with a help of a star atlas, but when the scope is pointed towards that object, I am not sure what I am looking at. I can see many stars but dont know how to name them when I am looking via my telescope.

    Can someone shed some light and help me?

    Thanks again! 

     

  • 10-13-2008 10:12 AM In reply to

    Re: Trouble locating objects in the sky

    Your telescope is showing you only a very tiny part of what you see naked-eye.

    With the typical 10-inch dob (like the ones from GSO, Orion, Skywatcher, Celestron, Zhumell, etc.) and a 20mm eyepiece, you are most likely seeing a patch of sky a little more than 1 degree in diameter.

    So, you must adjust your expectations from the atlas page accordingly. Most atlases have a grid that shows the sky divided into sections of 5 or 10 degrees. Look at the divisions on your atlas pages to determine the size of a constellation in degrees, then estimate the field of view of your eyepiece accordingly.

    You can measure the field of view of an eyepiece in a particular telescope by timing the passage of a star across the center of the field of view. The Earth rotates at 15 degrees per hour, which is 1/4 degree per minute.

    Choose a star near the celestial equator (such as Altair early in the evening this time of year, or any of the bright stars of Orion when it rises later in the night). Adjust your telescope's aim to allow the star to drift across the field of view, then time it with a watch or stopwatch. Make several tries and average them.

    Compare your time to 1/4 degree per minute to get the field of view in degrees. For example, if the star drifts across the diameter of the field of view in 30 seconds, your field of view is about 1/8th degree, etc.

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  • 10-13-2008 12:10 PM In reply to

    • tkerr
    • Joined on 01-02-2004
    • Coastal North Carolina USA.
    • Posts 8,690

    Re: Trouble locating objects in the sky

    ChicagoNewB:

    Hello

    I have a 10" Dob and everytime I point it towards the sky to locate any object (such as a star), I am toally lost. I can see the constellations with my naked eye and with a help of a star atlas, but when the scope is pointed towards that object, I am not sure what I am looking at. I can see many stars but dont know how to name them when I am looking via my telescope.

    Can someone shed some light and help me?

    Thanks again! 

     

    Let me try to add a little to what Jeff has already told you. 
    When you look at the sky with the naked eye, if you're under very dark skies, you might be seeing stars as dim as mag 6, maybe a little dimmer.  When you look at stars through a 10" telescope you're are seeing stars dimmer than mag 14. Many more stars than you would ever see with the naked eye all within a much smaller field of view.  
    living in or near a large urban light polluted area such as Chicago these magnitudes will be significantly reduced to only the brightest stars.

    If you are unsure what you are aiming the telescope at or looking at then first you need to make sure the telescope is actually aimed in the same area of the sky you were looking at with the naked eye.  You need to make sure you finder scope and telescope are aligning on the same thing.  Best to do that during the day time with the telescope aimed at a distant object. 
    Find something like the insulator on a telephone pole about 1000 yards or more from your position.  Center the telescope on it first then adjust the finder scope until it too is centered on the same spot.
    At night when you aim the telescope at an area of the sky you will know it is aimed at the same are you were looking at with the naked eye.   Use your star atlas or planetarium software to help identify objects.   
    Most deep sky objects are dim and colorless. You need to allow your eyes a little time to adjust at the eyepiece. Objects vary greatly in both size and or brightness. Some are obvious and easy to see while others will require you to use little tricks like averted vision to see them better.
    Other tricks you can try to help you see objects better through the eyepiece are a hood over your head and EP/focuser to block intrusion of stray periphery light between your eye and the eyepiece.  An eye patch to cover your other eye so you don't have to strain it to keep it closed. Strain on the other eye also places strain on the eye your are using to see through the eyepiece.  When you can relax the other eye you can see through the other better.

    With time comes experience, be patient you will learn how to locate and identify the different objects. You will learn how to observe and actually view objects easier.  Take your time on the eyepiece allowing your eye to adjust and absorb the light coming through to your eye. 

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    Have A Nice __________
    Tim Kerr
    Healthy mind - healthy body - healthy earth.
    Ad astra
    Ad eundum quo nemo ante iit
    Jacksonville, NC.

    Equipment:
    Orion XT10 Classic, Celestron C6 R-GT w/updated CG5 GT mount, C80ED
    Canon EOS 350D, Meade DSI II Color CCD, Phillips SPC900NC WebCam
  • 10-13-2008 03:36 PM In reply to

    Re: Trouble locating objects in the sky

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  • 10-15-2008 10:31 AM In reply to

    Re: Trouble locating objects in the sky

    I've cut my time at least in half by using one of these:

    http://www.telescope.com/control/product/~category_id=finder_scopes/~pcategory=accessories/~product_id=07228

    That little guy I linked to is zero power, so you can see a huge portion of the sky and sometimes entire constellations AND it doesn't have a lens, so what you see is correctly oriented. It also projects a red dot to dial your scope in very close.

    The trouble I had was (like mentioned) the telescope's FOV is so small compared to the atlas or astronomy program. To add to frustration, what you see in the scope is backwards and/or upside-down,

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  • 10-15-2008 11:16 AM In reply to

    • tkerr
    • Joined on 01-02-2004
    • Coastal North Carolina USA.
    • Posts 8,690

    Re: Trouble locating objects in the sky

    Here's very popular one>> Telrad 1:1 zero magnification reflex sight

    You can find charts and planetarium programs that will work with this one.

    Signature
    Have A Nice __________
    Tim Kerr
    Healthy mind - healthy body - healthy earth.
    Ad astra
    Ad eundum quo nemo ante iit
    Jacksonville, NC.

    Equipment:
    Orion XT10 Classic, Celestron C6 R-GT w/updated CG5 GT mount, C80ED
    Canon EOS 350D, Meade DSI II Color CCD, Phillips SPC900NC WebCam
  • 10-15-2008 04:35 PM In reply to

    • WannaB
    • Joined on 04-30-2008
    • Mindenmines, MO
    • Posts 497

    Re: Trouble locating objects in the sky

    tkerr:

    Here's very popular one>> Telrad 1:1 zero magnification reflex sight

    You can find charts and planetarium programs that will work with this one.

    MOST DEFINITELY!!!

    One of the best, if not THE best, accessory a beginner should have.  I'm relatively new to this myself and I can't tell you what a difference my Telrad made.

    I need a t-shirt that has a picture of a Telrad and the words, "Got Telrad".  Stupid, I know.  But you see it for virtually everything else!  

    Signature
    Equipment: (not nearly enough)

    Orion XT8 Classic Dob
    Orion Shorty-Plus 2x 3-element Barlow
    Telrad finder
    couple of Plossl's(10mm & 25mm)
    Nikon 10 X 50 binos
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