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  1. #1
    Dragon206's Avatar
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    Default Illuminated reticle EP?



    My kit includes 3 EPs right now: 13mm, 17mm and 23mm. I normally use the 23mm for the alignment procedure (it's an Axiom, and the 82 degrees AFOV is great).

    I find it quite hard to center perfectly in the EP the stars I use for the goto alignment, which is not a big problem for visual observation, but I guess that when the time will come to start doing accurate polar alignments for astrophotography it will be frustrating.

    A few days ago I used the live view feature of my camera, connected to my laptop, to have a grid superimposed on the image, which allowed me to carry out a precise alignment. The fact is that having to connect camera and computer just for the alignment is time consuming.

    When I got the telescope I didn't consider an illuminated reticle EP, but I think I should buy one.
    I own a Celestron 925 HD. I found two intersting EPs:
    - Orion 12.5mm Illuminated Plossl
    - Orion 20mm Illuminated Centering Eyepiece.
    They are both in an acceptable price range. The first one would give me a pretty high magnification (about 185x - so I guess that drifting of a star can be spotted earlier) but with a limited AFOV (I think it's 40 degrees), while the second EP has a 70 degree FOV.

    There is also the Meade 12mm MA Astrometric EP, which is much cheaper than the Celestron EP, but has 50 degree AFOV and a pretty high mag.

    Any suggestions about a good EP I can consider?
    Last edited by Dragon206; 05-09-2011 at 05:38 AM.
    Dragon206 - Stefano
    Scope: Celestron CGEM EdgeHD 925, Tecnosky APO 80/480
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  2. #2
    jimt's Avatar
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    Default

    Unless you plan on doing drift alignments any time soon, you dont really need one right now. The easiest way to center your alignment stars is to get your star somewhere near the center of view then switch to your shortest eyepiece. Defocus it to the point it fills up the eyepiece then it is very easy to center. This works great for visual. Try it and see how it works for you.

    Clear skies
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    Now where did I put that clear sky button!

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    BobDob (05-10-2011),Dragon206 (05-09-2011),Joe Lalumia (05-09-2011),kwalker (05-09-2011)

  4. #3
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    Default

    I purchased the Orion 12.5 eyepiece a few weeks back and have used it a couple of times for more precise alignments when getting ready to do photography, but for visual my answer was to align my green laser pointer so that when viewed thru my 25mm eyepiece it looks centered, then I just place each alignment star in the end of the laser beam, that seems to work well enough for visual. As far as drift alignment goes I haven't done it with the EP, instead I used my camera and some instructions Gordon (ghswen) has in the downloads section.

    Just some more things to ponder...
    Kevin AD5VG
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  5. #4
    Joe Lalumia's Avatar
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    Default

    Jim is 100% correct-- I have a 12.5mm illuminated eyepiece. Now ask me how many times I have ever used it to align the telescope. probably 2 times. (However I do use it to train the drives)

    Regardless of what you hear on the internet-- rough centering the alignment stars is all that is needed for visual alignment.

    Astrophotography requires an accurate drift alignment-- or the All Star feature alignment in some Celestron scopes. (not needed for visual)

    Clear skies!
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  7. #5
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    Default

    I use the Orion 20mm illuminated eyepiece but its a bit on the bright side and for the most I don't turn on the ill reticle.
    I never thought about defocussing
    the All star alignment procedure on the mount is very accurate but you still need the crosshairs.....or maybe the defocus trick.(thanks Jim)
    Ken

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  8. #6
    Dragon206's Avatar
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    Default

    Good suggestions here!
    I didn't think about defocusing the star, I'll try that for sure!

    It's pretty hard for me to stay up until late during the week and the sky here is completely dark at 10.30PM, so I sometimes setup the telescope simply to learn how to use it and to practice the setup and the alignment. The all star polar alignment is an amazing feature BTW (I tried to take a picture before and after: before I got star trails after 30s, after it took more than 2 minutes - it wasn't a perfect alignment because I just wanted to try that utility), but it was still pretty hard to judge when the star was exactly centered.
    For visual observation, accuracy was pretty good with just a rough polar alignment (w/o all star polar alignment).

    Considering the suggestions, I think I won't buy that eyepiece, at least in the near future.

    I want to learn how to perform the drift alignment, so that when the time will come I won't spend half of the night to align the scope. Is the ASPA so accurate that the drift alignment is no longer required or is it better to do it anyway?
    Dragon206 - Stefano
    Scope: Celestron CGEM EdgeHD 925, Tecnosky APO 80/480
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    Default

    Even with the all star alignment you'll still need to do a drift if you are going to do AP. Here are some before/after images of my drift attempts on my CG5 mount:

    Azimuth after all-star alignment:


    Azimuth after all-star and drift alignment:


    Altitude after all-star:


    Altitude after all-star and drift:


    These were six minute runs with the CCD drift method - three minutes one way, three minutes reversed to make the angles. If I bumped it up to five minutes each way I'd probably get the alignment tweaked in even better but for what I'm currently doing it's OK.
    Kevin AD5VG
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