Author Topic: Is this collimation off?  (Read 617 times)

Mayur Wilson

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Is this collimation off?
« on: December 24, 2017, 12:44:43 AM »
I can find the center spot directly inside the ring by adjusting the primary knobs (easy enough), but it is not directly over the spot where the spider veins could hypothetically intersect (were it not for the secondary mirror and housing).  It looks like the centre spot is away.  I am aware that the larger secondary and primary circles aren't supposed to be concentric in a Newtonian (and they are not), but would be the centre spot supposed to be off the point where the spider veins could seep?  Thank you for any input!

-DougAttached Thumbnails



Niro Hardy

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Re: Is this collimation off?
« Reply #1 on: December 24, 2017, 08:53:56 AM »
I can not tell from the pictures, but I wonder if your secondary demands adjusting to be centered in the focuser.  I make that adjustment before fixing the primary.  And before I do that I make sure that the focuser is pointing straight through the tube.  It took me some time to have this much figured out.  Adjusting the primary is the easiest part of the whole thing.  I also put some effort into making sure the secondary was pointing straight at the focuser.  This one is somewhat catchy, becaue I do not know how you can tell with much accuracy, since teh centre appears to stay put as you look through the focuser and rotate the secondary.  I ended up placing the UTA on the ground under a ceiling lamp, then hung a plumb line from the center of the lamp to the center of the secondary, and corrected the secondary to shine the light from the lamp onto the focuser.  I've never seen something like this published, I simply made it up, and I wonder if there is a better solution, other than simply eyeballing it.  I'm somewhat new to this, so I'm also posting so I can see what more seasoned people have to say about this.

fefeldarsro

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Re: Is this collimation off?
« Reply #2 on: December 30, 2017, 04:52:22 AM »
i think you can get a laser collimator for $20 these days.
I went to youtubehttps://www.youtube....?v=pqrA8zIwFlU

Frky Sherman

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Re: Is this collimation off?
« Reply #3 on: December 30, 2017, 10:13:00 AM »
Oh you are for so much fun, happy reading!:

http://www.skyandtel...ctor-telescope/

http://www.cloudynig...escope-v4-r2599

Can't tell either from the pics, difficult to guess without a center spot.

For visual use you this is all I use:
http://www.scopestuff.com/ss_coll2.htm

If you just use your scope casually to look at the moon just do your best eyeballing the procedure w/o an eyepiece...

Precise collimation is for imagers or if you plan to observe things like double stars, nebulae, etc.

dustsungline

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Re: Is this collimation off?
« Reply #4 on: December 31, 2017, 09:27:44 AM »
Quote
I can get the center spot directly inside the ring by adjusting the primary knobs (easy enough), but it is not directly over the spot where the spider veins would hypothetically intersect (were it not for the secondary mirror and housing). It appears that the center spot is off. I know that the larger secondary and primary circles are not supposed to be concentric in a Newtonian (and they're not), but is the center spot supposed to be so far off the point where the spider veins would intersect? Thanks for any input!

-Doug


Please disregard center spot alignment with the spider veins, as this is not needed for even good collimation. The spider veins are irrelevant, though they do offer a tempting reference point. A good cheshire/sight tube combo tool (one with cross hairs) is what you need. Collimation is not the bear that many folks think it is, it just requires the proper tools and a bit of time playing around with them to understand the relationships of your collimation signatures. It is difficult to tell from your photos, but if you are only doing visual observing, your present collimation may be close enough for casual planetary viewing.

HOWEVER, if you are OCD about collimation, as many are, get a good set of collimation tools, read up about the procedure and understand about all the nuances involved for acquiring that "perfect" collimation signature... and then enjoy the fruits of your labor!

Best regards and clear DARK skies!

CB