Advertisement
If you have a new account but are having problems posting or verifying your account, please email us on hello@boards.ie for help. Thanks :)
Hello all! Please ensure that you are posting a new thread or question in the appropriate forum. The Feedback forum is overwhelmed with questions that are having to be moved elsewhere. If you need help to verify your account contact hello@boards.ie

Collimation Hell

Options
  • 10-01-2013 11:19am
    #1
    Myrddin
    Closed Accounts Posts: 33,733 ✭✭✭✭


    Folks,

    I've a cheapo Newtonian Reflector scope here {National Geographic NG76AZ}, something the little fella got for xmas there a few years ago. Watching Stargazing Live has reinvigorated my desire to get back into looking up at the stars/planets/moon etc, so I took the scope down and tried it out.

    Turns out from my reading that the scope is way outta calibration, & probably always has been when I think of it. Its very hard to focus on anything, the likes of the moon appear almost smudgey etc, do my interest in it wained after a while.

    I'm a total beginner, but I've been trying by best as collimating it & just can't get anywhere. Both the secondary mirror & primary mirror don't seem to be anywhere near where they should be. Does anyone offer a collimating service at all? :(


Comments

  • Options
    #2
    Nerro
    Registered Users Posts: 393 ✭✭Nerro


    Hi,
    I know the whole collimation thing sounds scarry but its actually aint and unfortunatelly for newtonians you have to do it pritty often.Its more or less like topping up oil for your car.You simply have to know how to do it...
    Do you have any tools?Like laser collimator or cheshire??i would strongly advise to get one if you dont, as they are cheap and really handy.
    Finally here is a nice guide that i found very usefull when i needed doing mine for the first time.
    http://www.astro-baby.com/collimation/astro%20babys%20collimation%20guide.htm
    Hope that helps.


  • Options
    #3
    Myrddin
    Closed Accounts Posts: 33,733 ✭✭✭✭Myrddin


    Nerro wrote: »
    Hi,
    I know the whole collimation thing sounds scarry but its actually aint and unfortunatelly for newtonians you have to do it pritty often.Its more or less like topping up oil for your car.You simply have to know how to do it...
    Do you have any tools?Like laser collimator or cheshire??i would strongly advise to get one if you dont, as they are cheap and really handy.
    Finally here is a nice guide that i found very usefull when i needed doing mine for the first time.
    http://www.astro-baby.com/collimation/astro%20babys%20collimation%20guide.htm
    Hope that helps.

    I don't have any collimating tools which certainly doesn't help. I'm not sure whether go spend money on calibration tools given the scope itself is such a basic & cheap one. How much would I be looking at to get adequate tools?

    I was reading that guide just before i posted this thread, it seems fairly comprehensive alright. I just can't seem to get anywhere at all, the primary mirror on my scope doesn't even have a central point mark & I'm a real goon when it comes to measuring for things like that :(


  • Options
    #4
    endacl
    Registered Users Posts: 22,249 ✭✭✭✭endacl


    EnterNow wrote: »

    I don't have any collimating tools which certainly doesn't help. I'm not sure whether go spend money on calibration tools given the scope itself is such a basic & cheap one. How much would I be looking at to get adequate tools?

    I was reading that guide just before i posted this thread, it seems fairly comprehensive alright. I just can't seem to get anywhere at all, the primary mirror on my scope doesn't even have a central point mark & I'm a real goon when it comes to measuring for things like that :(
    You can make your own collimator from an old 35mm film canister or similar. It's not hard. I don't have a link handy, but I'm sure if you google it, something will pop up. You'd be better off spending the price of a collimator on a half decent pair of binoculars at this stage, tbh.


  • Options
    #5
    Myrddin
    Closed Accounts Posts: 33,733 ✭✭✭✭Myrddin


    endacl wrote: »
    You can make your own collimator from an old 35mm film canister or similar. It's not hard. I don't have a link handy, but I'm sure if you google it, something will pop up. You'd be better off spending the price of a collimator on a half decent pair of binoculars at this stage, tbh.

    Yeah I've seen the old 35mm film canister trick, unfortunately I don't have one. I'd prob be better buying one, but like you say, I don't want to put good money after bad either.

    Not sure what to do, if I could get this scope even somewhat calibrated properly & see what the results look like I could then decide whether to move on from it or not


  • Options
    #6
    ZeRoY
    Registered Users Posts: 959 ✭✭✭ZeRoY


    EnterNow wrote: »
    I'm not sure whether go spend money on calibration tools given the scope itself is such a basic & cheap one

    This will be a problem, I tried myself on a cheap scope with a laser collimation tool and you can get it about right but noway perfect as the focuser is likely to be shifting as you focus, turn the eyepieces, etc ...

    I assume you are going to be using this just visually, no photograph, and so I would use Astrobaby guide and just do it by eye without tools....


  • Advertisement
  • Options
    #7
    Myrddin
    Closed Accounts Posts: 33,733 ✭✭✭✭Myrddin


    ZeRoY wrote: »
    This will be a problem, I tried myself on a cheap scope with a laser collimation tool and you can get it about right but noway perfect as the focuser is likely to be shifting as you focus, turn the eyepieces, etc ...

    I assume you are going to be using this just visually, no photograph, and so I would use Astrobaby guide and just do it by eye without tools....

    Definitely, its not a very sturdy setup...even turning the focusing wheel throws the scope off whatever it was pointed at.

    I'll read through that guide in its entirety, but you reckon its largely a waste buying proper toolage for a scope of this caliber yeah?


  • Options
    #8
    Nerro
    Registered Users Posts: 393 ✭✭Nerro


    EnterNow wrote: »

    I don't have any collimating tools which certainly doesn't help. I'm not sure whether go spend money on calibration tools given the scope itself is such a basic & cheap one. How much would I be looking at to get adequate tools?

    I was reading that guide just before i posted this thread, it seems fairly comprehensive alright. I just can't seem to get anywhere at all, the primary mirror on my scope doesn't even have a central point mark & I'm a real goon when it comes to measuring for things like that :(
    well new cheshire cost 40e second hand 23pounds with delivery
    http://www.astrobuysell.com/uk/propview.php?view=64157
    i recon you could find even cheaper on cloudy nights if you play your cards right with shipping from the states.
    Now where abouts do you live?I know there are quite a few events orginized here around Dublin where you could bring your scope and someone will show you how to do it properly.


  • Options
    #9
    Myrddin
    Closed Accounts Posts: 33,733 ✭✭✭✭Myrddin


    Nerro wrote: »
    well new cheshire cost 40e second hand 23pounds with delivery
    http://www.astrobuysell.com/uk/propview.php?view=64157
    i recon you could find even cheaper on cloudy nights if you play your cards right with shipping from the states.
    Now where abouts do you live?I know there are quite a few events orginized here around Dublin where you could bring your scope and someone will show you how to do it properly.

    Cheers for that man, will have a look. I'm based in Chapelizod, so near enough the Phoenix Park...


  • Options
    #10
    Myrddin
    Closed Accounts Posts: 33,733 ✭✭✭✭Myrddin


    Should the center mark on the primary mirror, be right in the middle of the reflected image of your eye on the secondary mirror? I read somewhere that secondary mirrors are sometimes purposely offset by the manufacturer...

    Here's a dreadful attempt at showing what I mean. The spider vanes don't seem anywhere near right. I have a piece of white card in the tube to show the secondary mirror better.

    2uhmzys.jpg

    Here it is with the white card removed

    2ezpo9c.jpg

    Its prob of no help though, hard to photo this kind of thing!


  • Options
    #11
    Nerro
    Registered Users Posts: 393 ✭✭Nerro


    well if you live in Dublin there is an event organized this saturday at sugar loaf (weather dependant) and i know there is another at sandymount beach (dont know the exact date).
    would strongly recomend to bring your gear over there before buying anything...


  • Advertisement
  • Options
    #12
    Nerro
    Registered Users Posts: 393 ✭✭Nerro


    EnterNow wrote: »
    Should the center mark on the primary mirror, be right in the middle of the reflected image of your eye on the secondary mirror? I read somewhere that secondary mirrors are sometimes purposely offset by the manufacturer...

    Here's a dreadful attempt at showing what I mean. The spider vanes don't seem anywhere near right. I have a piece of white card in the tube to show the secondary mirror better.

    2uhmzys.jpg

    Here it is with the white card removed

    2ezpo9c.jpg

    Its prob of no help though, hard to photo this kind of thing!
    well as far as i can see from the pictures your primary is way off...
    you should have a plastic cap to cover your focuser that should have come with your scope.Just drill a hole in the middle and follow that guide that i gave you...your primary should be a nice circle looking thru it.
    wouldnt worry about the offsets that are mentioned in the guide just try and put everything smack dead in the middle as you will only be doing observin.Another thing that you could do is measure your spider vanes as per guide.


  • Options
    #13
    Myrddin
    Closed Accounts Posts: 33,733 ✭✭✭✭Myrddin


    Nerro wrote: »
    well as far as i can see from the pictures your primary is way off...
    you should have a plastic cap to cover your focuser that should have come with your scope.Just drill a hole in the middle and follow that guide that i gave you...your primary should be a nice circle looking thru it.
    wouldnt worry about the offsets that are mentioned in the guide just try and put everything smack dead in the middle as you will only be doing observin.Another thing that you could do is measure your spider vanes as per guide.

    Yep found that cap, perfect! I'll drill a small hole in the center of it now.

    Cheers for the help so far :)


  • Options
    #14
    Myrddin
    Closed Accounts Posts: 33,733 ✭✭✭✭Myrddin


    Only prob with the guide though before I read it again, is that it states you must have a Cheshire collimater to allign the primary, which I don't have :( Will try & set everything as best I can by eye anyway, because as you said it'll only be for the most basic of observation.


  • Options
    #15
    Nerro
    Registered Users Posts: 393 ✭✭Nerro


    EnterNow wrote: »
    Only prob with the guide though before I read it again, is that it states you must have a Cheshire collimater to allign the primary, which I don't have :( Will try & set everything as best I can by eye anyway, because as you said it'll only be for the most basic of observation.
    sorry my bad...i wanted to say that that cap should be used for secondary...sorry about the confusion.as in your pictures yours is tilted (at least i think so).when you will be looking thru the hole in the cap you should see the miror as a circle rather then an oval.


  • Options
    #16
    ZeRoY
    Registered Users Posts: 959 ✭✭✭ZeRoY


    Here's my 6" Newt with Cheshire tool in ( the 4 blades visible ) after collimation using that guide. On 6" and smaller newt the dark part should be slightly off center - "oval" as per the diagram on top right in back of picture (thats my PC screen on the Collimation webpage)


  • Options
    #17
    Myrddin
    Closed Accounts Posts: 33,733 ✭✭✭✭Myrddin


    Just a quick thanks to all here who helped, I got it fairly well set up & just had my first look at Jupiter & three of its moons with my 10 year old soon. Amazing. The astronomy bug bites...hard!

    Now, to get back to 37 degrees Celsius again :p


Advertisement