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    RhetoricCamel's Avatar
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    Default DEC Setting circle is off?



    What is one to do if the DEC setting circle is off? I haven't been outside to try it due to cloud coverage. Just doing some tests in the house and it seems my scope is aimed a couple degrees to the right (when looking at it from the back) when the DEC is right on 90. I would think that if it's lined up with 90 the scope would run with the EQ mount. Everything seems to be even until the scope is attached.

    I don't know how else to word it so hopefully this is good enough. If not maybe I'll try a couple pictures to see if it shows what I'm trying to ask.
    ----- Mike -----
    Omni XLT 150, Astromaster 114EQ, Celestron FirstScope 70mm EQ Refractor, Canon 350D, Canon SX210
    32mm, 25mm, 12.5mm, 6mm, 4mm, 2x Barlow

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  2. #2
    KathyNS's Avatar
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    Default

    When the scope is (exactly) parallel to the polar axis, the declination setting circle should read 90 degrees. On most mounts there will be some provision for adjusting it if it is out: typically it is held by a set screw or just by friction.

    While the above method is accurate to a degree or so, it is difficult to know whether the scope is exactly parallel to the polar axis. A more accurate method is to "tumble" the mount. This is somewhat hardware dependent - on my old C-90 with its single fork mount, I have to remove the finder scope to do it. It might not work on some mounts at all.

    Rotate the RA axis so that the telescope is on the east side of the polar axis. Point it at an object on the north horizon. Note the Declination reading. Now rotate the mount 180 degrees in RA so that the scope is on the west side of the polar axis. Again point the scope at the same object on the north horizon. Note the Declination reading. If the two readings are the same, the Declination circle is set properly. If the readings are different, move the setting circle by half the difference. Repeat until you get no difference in the two readings.

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    Newtonian Astrograph; ATIK 383L+; EFW2 filter wheel; Astrodon Ha,LRGB filters; KWIQ/QHY5 guide scope; Planetary AP: Celestron C-11; ZWO ASI120MC; Portable: Celestron C-8 on
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  4. #3
    cawilliams1983's Avatar
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    Default

    My EQ-1 head does the same thing. I believe it actually reads close to 85 or something. I've not had a chance to use it with a telescope yet but, if I don't send it back to Orion, I'll just subtract that much from the dec coordinates I want to view.
    Corey

    Meade DS 2114
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    SkyQuest XT10 Dob, Zhumell EP kit, Orion Min-EQ Tabletop mount to be used with wife's Canon 350D

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  5. #4
    RhetoricCamel's Avatar
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    Default

    @KeithBC - I figured that the setting circle should read 90 with the scope parallel to the polar axis, but it's off about 5 degrees to the right (when looking at it head on). The little needle that points at the setting circle has two little screws in it. I was thinking of loosening them and adjusting it to 90 with the scope parallel to the polar axis. The only reason I say that the DEC circle itself is right is because it's straight on with polar axis.
    Thanks for the help I will give it a try next clear night when I have a view north.

    @cawilliams1983 - I thought about just subtracting the amount but I know I'll either forget or add it instead of subtract. If I can't adjust the needle or the setting circle like Keith suggested then I will most likely have to resort to this method.
    ----- Mike -----
    Omni XLT 150, Astromaster 114EQ, Celestron FirstScope 70mm EQ Refractor, Canon 350D, Canon SX210
    32mm, 25mm, 12.5mm, 6mm, 4mm, 2x Barlow

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