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  1. #1
    gus1911's Avatar
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    Default Do Not Use Polaris As An Alignment Star. Why?



    I know not to use Polaris as an alignment star, but I can't find a good reason why not. Last evening, because of time of night and trees and houses, I found it convenient to use Polaris as my 2nd alignment star. I have the Orion 10" GoTo. The software had some serious problems.

    I started with Altair, then selected Polaris as my 2nd star. On the first attempt, the scope just locked up as it approached Polaris. I shut down and started over from the beginning. Same procedure as the first attempt, but when slewing to Polaris the scope stopped nowhere near Polaris - not even close.

    Gave up and chose Vega for the 2nd star, even though it was much too close to Altair - not recommended. It aligned fine and I found M31 easily.

    Why all the problems with Polaris? Is it Polaris or a software glitch?

  2. #2
    wyomingrob's Avatar
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    Default Re: Do Not Use Polaris As An Alignment Star. Why?

    Polaris is used to "polar align" the scope.
    A lot of software used in goto's recommend not to use it as an alignment star for that reason.
    Actually, Polaris is not "true North". It is actually about 2 degrees from it.
    I use the "Kochab Clock" method of polar alignment, it's much more accurate.
    You can easily find it on the web, and it takes much longer to read it, than to do it.
    Also, try to find stars for alignment that are about 90 degrees apart, and not on the same "plane" of the sky.
    That way the goto can "calculate" any errors in level.
    That's the methods I use, and they work well for me.

    Hope this helps.
    Rob C. members/wyomingrob-albums-my-get-away-picture63422-cheyenne-20130326-00534.jpg

  3. #3
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    Default Re: Do Not Use Polaris As An Alignment Star. Why?

    i find aligning very difficult and a hit or miss, collimating is a snap
    i don't know if it's the nature of the beast or if i'm just too green

  4. #4
    fmhill's Avatar
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    Default Re: Do Not Use Polaris As An Alignment Star. Why?

    Quote Originally Posted by gus1911 View Post
    I know not to use Polaris as an alignment star, but I can't find a good reason why not. Last evening, because of time of night and trees and houses, I found it convenient to use Polaris as my 2nd alignment star. I have the Orion 10" GoTo. The software had some serious problems.

    I started with Altair, then selected Polaris as my 2nd star. On the first attempt, the scope just locked up as it approached Polaris. I shut down and started over from the beginning. Same procedure as the first attempt, but when slewing to Polaris the scope stopped nowhere near Polaris - not even close.

    Gave up and chose Vega for the 2nd star, even though it was much too close to Altair - not recommended. It aligned fine and I found M31 easily.

    Why all the problems with Polaris? Is it Polaris or a software glitch?
    No, Its Polaris location being 0.8 degrees from the Celestial pole... Polaris ia better classified as an aid to polar alignments, its use as an alignment star is fraught with problems as 0.8 degrees is too far from the celestial pole as Polar alignments should be closer than 15 arcminutes (0.15 degrees). And when doing a star alignment, a mount's angular resolution is poorest when pointed close to the celestial pole. Good alignment stars are those closest to the celestial equator as the degree angle is spread over a greater width than when close to the pole meaning greater pointing accuracy can be resolved with stars near the equator...
    Thanks, Mitch - K1FH
    And sidekick Shadow, the precocious one
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    I made my first star trail image in 1949 and have collected too much gear to list ever since...

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  5. #5
    gus1911's Avatar
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    Default Re: Do Not Use Polaris As An Alignment Star. Why?

    Thanks guys for the responses. I've been aligning fine for over a year now just using magnetic north, but I've never before had the scope "choke" during alignment. Glad to know it's Polaris and not software problems.

  6. #6
    Opticell's Avatar
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    Default Re: Do Not Use Polaris As An Alignment Star. Why?

    Great information guys. I can sure use this in my future alignments, haven't had a chance to commit this errror yet, but would have on the 13th when looking for alignment #2, luckily Spica showed up in the early 9:20pm sky before Polaris did.
    Cheers, Mike
    Orion XT12i ... Tal Russian Newtonian 8" F4.9 w/60lb pillar EQ mount ... Celestron Nexstar 102GT 4"
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  7. #7
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    Default Re: Do Not Use Polaris As An Alignment Star. Why?

    Looked up in Star Walk so if I want to use Polaris to set up the equitorial, this image shows the Polaris rotates a nice circle inside the Telrad 2º reticle as shown in the picture.
    2013-08-17 09.43.24.jpg
    Cheers, Mike
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  8. #8
    Bob327's Avatar
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    Default Re: Do Not Use Polaris As An Alignment Star. Why?

    There should be absolutely positively NO PROBLEM with aligning an ORION GOTO Dob using POLARIS as one of your alignment stars...

    Why... simple because it is an Alt/Azm mount NOT a EQUATORIAL mount...

    I use POLARIS as my first alignment star on every single Azm/Azm mounted GOTO scope I own (or have aligned) .. BUT I sure do not use it to align any GEM mounted scope...

    Bob G
    CPC1100 housed in a slotted domed observatory (Exploradome) 4 and 5 inch refractors for use from the lawn, a 8" Sct (NS 8i) for star parties...
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    Retired, also have 2 other hobbies
    1. tinker with older Corvettes (6 in garage)
    2. make a heck of a lot of sawdust in my wood shop.

  9. #9
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    Default Re: Do Not Use Polaris As An Alignment Star. Why?

    I use polaris all the time on my nexstar altaz goto and it seems to work good? but dont use it on a GEM mount if i am understanding this correct??
    Brett
    Scopes: ES ED80 f/6, Celestron 130SLT f/5, Orion 120mm f/8.3 refractor, Orion ST80 f/5, Orion Observers 70mm f/10 and 60mm f/15, Meade Starfinder 8" f6
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  10. #10
    sxinias's Avatar
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    Default Re: Do Not Use Polaris As An Alignment Star. Why?

    The 10 inch Orion DOB is an azimuth mount. Polaris is an excellent star to use for alignment with an azimuth goto mount. You should have no difficulty using it. Azimuth mounts will have difficulty using a star near the zenith for alignment.

    Equatorial goto mounts can not use Polaris as an alignment star.
    SXINIAS

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