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B Pointing and using a Dobsonian

  1. Apr 25, 2016 #1

    sophiecentaur

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    My last question on the Astronomy Forum was answered perfectly. Let's try another one.
    I just bought a (s/h) Sky Watcher 200mm dobsonian and have already been stunned by seeing Jupiter with its coloured bands and its moons in brief holes in the danged cloud.
    But it is not easy to point it because the finder scope is inconveniently low down and requires some muscular control to lean over with my face against the barrel and neck twisted to the side in order to sight through the scope. I can cope with the position of the main eyepiece fine so is the answer to use a right angled finder scope? Alternatively, I have seen red dot finders. But they surely need you to look along the barrel again, which is what I am trying to avoid.
    Or how about I make a platform in the garden to raise up the base of the Dobs to a reasonable height. It could double as a seat on sunny afternoons. What is standard practice?
    I also have a question about eyepieces. I am fussy about camera lenses so I guess I could have to spend a lot to get a significant improvement on the kit eyepieces (25mm and 10mm). Is there a break point price between toys and useful lenses here?
     
  2. jcsd
  3. Apr 26, 2016 #2

    jedishrfu

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    You could consider a GOTO attachment as used on this telescope:

    http://www.telescope.com/Gift-Cente...-Dobsonian-Telescope/c/7/sc/1767/p/102019.uts

    and let the computer tell you where to aim.

    http://www.telescope.com/Orion-SynS...Controller/p/7947.uts?keyword=goto controller

    Your dobsonian mount needs some tracking hardware added so that the controller knows when you've moved the scope into position.

    I have one of the 8" Orion reflectors with the dobsonian hardware but never bothered to get the goto attachment as I tended to just poke around and see what I could see without knowing what I really saw.
     
  4. Apr 26, 2016 #3
    I think the simplest next step would be, as you propose, a right angle finder positioned to suit you. I am left eye dominant and have had to rearrange finders to suit my preference.

    Regards Andrew
     
  5. Apr 26, 2016 #4

    phyzguy

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    I second the right-angled eyepiece solution. On my 13" Dobsonian I had a 3" Newtonian for a finder, so you were looking in perpendicular to the main telescope barrel, and it worked great.
     
  6. Apr 26, 2016 #5

    sophiecentaur

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    Yep. Sounds lovely but it's Champagne appetite on a Beer income, I'm afraid. The Dob cost me about $200 (GBP equivalent). I plan to move up to GoTo when I have justified it and feel i could afford it. (The family must eat and little Jimmy needs new shoes - sob sob)

    That may well be my approach - initially at least. :smile:

    Cheers guys. Those were the answers I was looking for. I shall order a right angled job when I have finished chatting on PF.
     
  7. Apr 26, 2016 #6
    Another option is to get a red dot sight or a telrad. It actually useful for most larger dobs even if you have a good right angle finder as a first pointing tool.
     
  8. Apr 27, 2016 #7

    davenn

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    A good useable finder is still needed with a GOTO mount .... it's needed to align the stars whilst doing the star alignment so that the controller knows where it is pointing during setup. After that, the scope will point to wherever you tell the controller to go


    Dave
     
  9. Apr 27, 2016 #8

    jedishrfu

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    Davenn brought up a good point on the GOTO attachment, you'll have to pay roundtrip airline tickets for him to come and set your scope up.

    Its a one time fee unless of course you move your scope regularly and then it can become quite expensive.

    Always trying to be helpful.
     
  10. Apr 27, 2016 #9

    davenn

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    sounds like a plan!! I can go for that ... currently in South Africa, not so far to fly as from my Sydney, Australia home :wink::smile:

    hahaha this is true !! :smile:

    my Celestron CPC925 is a GOTO scope.
    When I go out to one of my dark sites and set up, usually do a 3 star alignment ( 3 bright stars are picked spanning a decent part of the sky)
    firstly I manually move the scope to the first star and align it in the finder eyepiece, then through the scope
    tighten the 2 axis clutches then tell the controller that this is star 1
    Then the controller up/ down and left /right arrows are used to move to move the scope to star 2 ( one of my choosing)
    again align it in the finder and main scope eyepiece then tell the controller this is star 2
    and that's repeater again for star 3. ... all done in 5 minutes and then the scope has a 30 sec think about it
    confirms the stars from its database can comes back with the message that alignment is confirmed .... it knows where it is
    after that it will happily track on what ever object is chosen

    Dave
     
    Last edited: Apr 27, 2016
  11. Apr 27, 2016 #10

    jedishrfu

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    Someday there'll be an app for that.

    Wait, there is I think:

    https://www.telescope.com/content.jsp?pageName=StarSeek

    Not sure if you still have to do the scope alignment but it seems if the iphone or ipad is automatically aligned then it would be possible to tie the scope in too.
     
  12. Apr 27, 2016 #11

    davenn

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    cool, that looks interesting ... thanks for the link :smile:
     
  13. Apr 27, 2016 #12

    Chronos

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    A right angle finder gets my vote. It was my first add on when I obtained my 10" Schmidt-Newt. Trying to peer through that inline finder requires the dexterity of a gymnast
     
  14. Apr 27, 2016 #13

    sophiecentaur

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    I have just ordered a right angle finder scope and look forward to an unchecked neck! The finder cost a big chunk of what I paid for the Dobs!
    It could be fun, Dave but I would probably rather spend the money on some posh optics and continue our beautiful (low cost) friendship via PF.
    Enjoy your time in SA.
     
  15. Apr 28, 2016 #14

    davenn

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    good stuff :smile:

    I can go with that :smile:


    D
     
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