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Equipment Discussions >> Reflectors

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GOLGO13
Carpal Tunnel


Reged: 11/05/05

Loc: St. Louis area
Re: How to Collimate your Newtonian new [Re: CatseyeMan]
      #5399832 - 09/02/12 03:50 PM

Thanks CatseyeMan. That worked pretty good and was a bit less painful. I've been thinking about getting one of your site tubes. I have an old Tectron set which is 1.25. I feel it works OK, but I may get a 2 inch site tube for my 10 inch just to be sure. However, I rarely use 2 inch eyepieces...partially because I only have one and it's a cheap 30mm GSO.

Thanks again!


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Starman1
Vendor (EyepiecesEtc.com)
*****

Reged: 06/24/03

Loc: Los Angeles
Re: How to Collimate your Newtonian new [Re: GOLGO13]
      #5399919 - 09/02/12 05:06 PM

Quote:

Thanks CatseyeMan. That worked pretty good and was a bit less painful. I've been thinking about getting one of your site tubes. I have an old Tectron set which is 1.25. I feel it works OK, but I may get a 2 inch site tube for my 10 inch just to be sure. However, I rarely use 2 inch eyepieces...partially because I only have one and it's a cheap 30mm GSO.

Thanks again!



The accuracy of your collimation depends on having accurate tools and achieving accurate registration for those tools in you focuser.
Every intermediate step of registration introduces another source of error into the possibility of accurate alignment.

Hence, the use of a 2" tool in a 2" focuser has the plus and minus tolerances of the registration between two pieces--the tool and the focuser.

When you add a second, intermediary, piece, you introduce an extra variable in registration: Tool>>Adapter>>Focuser, where >> represents a possibility of registration errors.

You can test adapters (or simply get a Glatter Parallizer) for accuracy until you get an accurate one, or, much more simply, use 2" tools in 2" focusers and eliminate a source of error.

And I was only referring to registration errors. There is also the possibility, with an adapter, of central hole alignment error, in which case perfect registration still results in alignment errors.

Better to eschew the use of adapters altogether if you have the choice. Errors in registration, when an eyepiece is used, are tolerable to the eye. Errors in registration during collimation result in visible errors in collimation.


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GOLGO13
Carpal Tunnel


Reged: 11/05/05

Loc: St. Louis area
Re: How to Collimate your Newtonian new [Re: Starman1]
      #5400103 - 09/02/12 07:48 PM

I do have a 2 inch / 1.25 glatter laser (quite nice in my opinion). But my site tube is 1.25. So I'll probably pickup a 2 inch site tube at some point.

Do the Catseye cheshires work with the original donut hole center mark? Or do they need the triangle?


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Starman1
Vendor (EyepiecesEtc.com)
*****

Reged: 06/24/03

Loc: Los Angeles
Re: How to Collimate your Newtonian new [Re: GOLGO13]
      #5400163 - 09/02/12 08:44 PM

Quote:

I do have a 2 inch / 1.25 glatter laser (quite nice in my opinion). But my site tube is 1.25. So I'll probably pickup a 2 inch site tube at some point.

Do the Catseye cheshires work with the original donut hole center mark? Or do they need the triangle?



My last 12.5" f/5 scope had a 5/8" white reflective donut. In a cheshire, there was a small black annulus outside the donut (in between the white annulus of the cheshire and the smaller donut of the mirror) that made it very clear when the donut was centered--it was easy to detect when the black annulus was skinnier on one side than the other.


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Elric82
super member


Reged: 09/25/11

Loc: Richmond, Kentucky
Re: How to Collimate your Newtonian new [Re: Starman1]
      #5406441 - 09/06/12 12:09 PM

I've been reading in some of the archived posts where someone had loosened the center screw on there secondary mirror (z12) thinking this was how you adjust the tilt of the secondary itself. Now I know this is not so, but as i am awaiting my sight tube/Cheshire tools and Vics book, I was curious if this is how you adjust the secondary so that it is directly under the focuser? Can't wait to get my new tools and booklet for sure.


Thanks ahead of time


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okieav8rModerator
I'd rather be flying!
*****

Reged: 03/01/09

Loc: Oklahoma!
Re: How to Collimate your Newtonian new [Re: Elric82]
      #5406495 - 09/06/12 12:44 PM

Quote:

I've been reading in some of the archived posts where someone had loosened the center screw on there secondary mirror (z12) thinking this was how you adjust the tilt of the secondary itself. Now I know this is not so, but as i am awaiting my sight tube/Cheshire tools and Vics book, I was curious if this is how you adjust the secondary so that it is directly under the focuser? Can't wait to get my new tools and booklet for sure.


Thanks ahead of time




Yes it is. The tools you've ordered will help you do a good job of centering the secondary under the focuser.


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GOLGO13
Carpal Tunnel


Reged: 11/05/05

Loc: St. Louis area
Re: How to Collimate your Newtonian new [Re: Elric82]
      #5406712 - 09/06/12 02:53 PM

Elric,

You may want to leave your secondary alone unless you find it's not correct. If your getting a site tube it should show you if it's correct or not though.

But yes...the screw in the middle adjusts the secondary mirror places towards and away from the primary mirror. The three allen screws adjust the tilt of the secodary mirror.


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Elric82
super member


Reged: 09/25/11

Loc: Richmond, Kentucky
Re: How to Collimate your Newtonian new [Re: GOLGO13]
      #5407082 - 09/06/12 07:05 PM

Golgo13

Yea, I hope I don't have to mess with the secondary other than tilt, which is no problem. But, there's only so many clear nights !! I hate to mess with the GSO laser. I'm done with it. Its gonna be clear here tonight, but the batteries are prolly dead. That's why I ordered Mr. Flys tools. And Vics book. I thought I posted this a while ago, but I forgot to send I think ( I was at work). I wonder how long it takes to get the collimation tools? I'm getting ancy. I hope one day I can understand collimation like Vic and Jim. It doesn't seem to bad, as I wrather enjoy it.

Regards. Mike


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Starman1
Vendor (EyepiecesEtc.com)
*****

Reged: 06/24/03

Loc: Los Angeles
Re: How to Collimate your Newtonian new [Re: Elric82]
      #5407201 - 09/06/12 08:08 PM

Here is a link to use with your new tools:
http://www.cloudynights.com/item.php?item_id=2677


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CatseyeMan
Vendor (Cats Eye Collimation)
*****

Reged: 12/16/04

Loc: Madison, AL USA
Re: How to Collimate your Newtonian new [Re: Elric82]
      #5407365 - 09/06/12 10:01 PM

Quote:

... I wonder how long it takes to get the collimation tools? I'm getting ancy....



They will ship tomorrow and you should get them in Monday's mail.

Quote:

...I hope one day I can understand collimation like Vic and Jim...



We've all been where you are now. I've got a pretty strong hunch that come this time next month, you'll feel a lot more comfortable with collimation.


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Elric82
super member


Reged: 09/25/11

Loc: Richmond, Kentucky
Re: How to Collimate your Newtonian new [Re: CatseyeMan]
      #5407767 - 09/07/12 06:13 AM

Thanks Jim, I hope you're right

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Blaise
member
*****

Reged: 09/05/12

Loc: Austin, Texas
Re: How to Collimate your Newtonian new [Re: Elric82]
      #5415830 - 09/11/12 06:05 PM

Does anybody use blue loctite on the locking screws? I'm having problems with mine backing out after long trips in the car.

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Peter Trinidad
member
*****

Reged: 02/21/08

Loc: San Antonio, Texas
Re: How to Collimate your Newtonian new [Re: Vic Menard]
      #5519898 - 11/14/12 06:18 PM

Hi Vic:

I am having the hardest time trying to collimate a 3 inch, f/6 old red tube Edmund telescope which is from around the 1980's (about 18 inches long). There are several of them under the reflector section on cloudy nights.
The mirror is not adjustable and is set in one position with screws. The only mirror you can adjust by moving it left or right or by bending the metal stalk which is the secondary mirror. At the present time I am using a small, plastic eyepiece with a pinhole in the middle of it but at best adjusting the secondary the stars look like "seagulls" and the moon looks out of focus at best. Someone told me that if you cannot adjust the primary mirror that it would be very difficult to collimate.

What are your thoughts?

Peter


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sixela
Postmaster
*****

Reged: 12/23/04

Loc: Boechout, Belgium
Re: How to Collimate your Newtonian new [Re: Peter Trinidad]
      #5520931 - 11/15/12 10:31 AM

That is correct: if you can move only one mirror you can get rid of coma in the centre of the image or focal plane tilt but to eliminate both you need to be lucky...

I'd just determine where the focal plane is and use a Cheshire or collimation cap with its pupil close to that focal plane; centre the collimation cap pupil in the centre spot or make the centre spot concentric with the Cheshire ring. And live with the focal plane tilt...

If you don't have a centre spot either then it's even more difficult to do something sensible, really.


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Vic Menard
Post Laureate
*****

Reged: 07/21/04

Loc: Bradenton, FL
Re: How to Collimate your Newtonian new [Re: sixela]
      #5520948 - 11/15/12 10:42 AM

Hi Peter,
Without a closer look at the mechanicals, I have to agree with Sixela's suggestions.

The only other possibility I could think of was to look at the way the primary mirror is mounted in the OTA (I couldn't find a good picture online). If it's cemented in place, your options are much more invasive. But if it's mounted in place with a few screws it may be possible to widen the screw holes enough to provide a small amount of tilt adjustment to the mirror/cell assembly. That's the way my refractor lens is mounted and it has plenty of tilt adjustment...

Edited by Vic Menard (11/15/12 10:43 AM)


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redsun
member


Reged: 05/28/07

Loc: Missouri
Re: How to Collimate your Newtonian new [Re: Vic Menard]
      #5549252 - 12/01/12 06:58 PM

hey Vic i just replaced the 8" mirror on my orion reflector along with new spiders i have collamated it like i always do the when i insert a 25mm and try to focus an object 1/4 mile away it will not come in to focus. im not new to reflectors owend them since i was 18 now 55 lol i need held

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CatseyeMan
Vendor (Cats Eye Collimation)
*****

Reged: 12/16/04

Loc: Madison, AL USA
Re: How to Collimate your Newtonian new [Re: redsun]
      #5549348 - 12/01/12 08:17 PM

Quote:

hey Vic i just replaced the 8" mirror on my orion reflector along with new spiders i have collamated it like i always do the when i insert a 25mm and try to focus an object 1/4 mile away it will not come in to focus. im not new to reflectors owend them since i was 18 now 55 lol i need held




Jumping in, I suspect your new mirror has a shorter or longer focal length than the original which has put your 25mm out of focus range. If the image gets sharper racking the focuser in, loosen all 3 Primary collimation screws about 5 turns, recollimate the Primary and try again to focus. If the image gets sharper racking the focuser out, tighten all 3 collimation screws about 5 turns, recollimate the primary and try again to focus.


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Jason D
Postmaster
*****

Reged: 10/21/06

Loc: California
Re: How to Collimate your Newtonian new [Re: CatseyeMan]
      #5549369 - 12/01/12 08:34 PM

Tell us more about your mirror replacement. Did you take the focal length into account as Jim mentioned?

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hoa101
super member
*****

Reged: 02/04/12

Loc: Northern Virginia
Re: How to Collimate your Newtonian new [Re: Jason D]
      #5571308 - 12/14/12 06:38 PM

I had a quick question about the "carefully decollimated" procedure that may be answered somewhere already... just cannot find it.

Anyway, after we've aligned the center spot with the sight tube, and the axial alignment with the procedure, won't the diagonal mirror always end up with the center spot no longer perfectly centered in the crosshairs of the sight tube? Anytime you adjust the tilt of the diagonal, it seems like it will end up a touch off. Or at least it does whenever I try to collimate in this manner on my dob.

Hopefully somebody can set me straight. Thanks.


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Starman1
Vendor (EyepiecesEtc.com)
*****

Reged: 06/24/03

Loc: Los Angeles
Re: How to Collimate your Newtonian new [Re: hoa101]
      #5571340 - 12/14/12 07:00 PM

The alignment of crosshairs with center spot on primary makes sure the focuser axis is aligned with the optical axis.
When you use the cheshire, next, to center the primary's center marker in the dark center of the bright annulus in the cheshire (i.e. if you have a combination tool you ignore the crosshairs for this part), you align the optical axis of the primary with the optical axis from the focuser.

The CDP procedure is used if you have an autocollimator, and the tiny tweaks necessary to correct the secondary won't really throw the crosshairs of the sight tube out enough to misalign the crosshairs and center marker.
You only decollimate the primary when doing this procedure so you can see the two images from the secondary and stack them perfectly. THEN you re-collimate the primary to stack all 4 images.

If you don't have an autocollimator, CDP has no meaning. Then it's simply:
--align secondary until crosshairs and primary mark line up.
--align primary until center mark is in center of dark area in cheshire.


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