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Precise Polar Alignment

Discussion in 'General Astronomy Chat' started by Zigarro, Jan 27, 2017.

Precise Polar Alignment

Started by Zigarro on Jan 27, 2017 at 4:29 AM

5 Replies 1349 Views 1 Likes

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  1. Zigarro

    Zigarro Well-Known Member

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    Zigarro, Jan 27, 2017
    #1
    This won't be news to you experienced hands but there are some of us who may have EQs that have no GoTo or polar scope, and want to do long exposure astrophotography. I came across this process in an article in Sky & Telescope titled, "Accurate Polar Alignment" by Alan MacRobert, dated July 17, 2006. MacRobert describes a process known as the Declination Drift Method. The claim is that this is even more accurate than using a polar scope! Anyone heard of this and have ideas on it's value?
     
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  2. Ed D

    Ed D Well-Known Member

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    Ed D, Feb 1, 2017
    #2
    I have used this method to do polar alignment. I have a crosshair eyepiece, this one from Antares, that I use to make alignment a bit easier. One evening I wanted to see just how accurate I could do the alignment, manually tweaking the motor speed on my CG-4. I went inside to eat dinner and came back outside almost an hour later. The star was still perfectly centered as I had left it.

    I know it's easier to use modern computer drives, but, like you, I don't have one and don't want one. My CG-4 with a simple 9V RA motor works for me, and I know I can set it up to perfection if I want to.

    I'm thinking of getting into planetary imaging, and if I do I'm using my setup.

    Ed D
     
  3. Ed D

    Ed D Well-Known Member

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    Ed D, Feb 1, 2017
    #3
    I haven't done it in a while, but if I remember correctly, what I do is turn off the motor and watch the star drift through the FOV. Once I tweak the mount so the star travels along the crosshair without drifting from one side to the other I know I'm done.

    Ed D
     
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  4. tripod tipper

    tripod tipper Well-Known Member

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    tripod tipper, Feb 5, 2017
    #4
    Hey Zigarro, good hearing from you again! Sorry I just came out of hibernation and saw my shadow but the good news is, I saw gees flying over Toledo Ohio last week, now dusting off the scope for future viewing.

    Thanks for posting the article on declination. My first set up of my EQ with the clock drive was very much the same way as described, after patience and several adjustments I found absolute tracking possible. This is a very good topic for the beginner and those who choose to expand their passion of the stars.

    Dennis
     
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  5. Zigarro

    Zigarro Well-Known Member

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    Zigarro, Feb 5, 2017
    #5
    Thanks Dennis. I was wondering where you'd been. I was prematurely curious about drift alignment since I'm nowhere ready to dive into astrophotography but it sounds like it is very precise, if time consuming. I still plan to polar align using a visual on Polaris but in order to level my EQ2-mount, I picked up one of these on Ebay for $3;
    http://www.ebay.com/itm/60mm-Large-...981616?hash=item25cde2c830:g:8AIAAOSwux5YT3lf
    Mine shipped on a slow boat from China and if I'd realized how long it would take, I'd have paid this "US shipper" his $8.50! It's about 66mm dia. but I just lay it on the accs'y tray and it works fine.
     
  6. tripod tipper

    tripod tipper Well-Known Member

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    tripod tipper, Feb 6, 2017
    #6
    You are right about bubble levels, their cheep and convenient to use. Though the initial set up of an EQ mount may seem a bit difficult at first for the beginner, it gets easier every time you do it, and a bubble level is a great help to your success which makes it more accurate and simple to the EQ tracking. I as you also do, set mine on the tripod tray, essential when you are in the field where the ground is usually uneven, definitely gets you within the range of adjustments.

    Dennis
     
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