Center spotting the primary - Templates

[Apprentice]

So I gathered the courage to center spot my primary on my Astromaster 130 EQ. Got me the round paper enforcer stickers.

I saw some great tutorial on youtube, where the guy was using a template on acetate (I hope thats how the transparent sheet is called). I wanted to find the templates for download, which I would then try to print on in a local copy shop, but I had no luck.

The reason I want to use this template is because its premade and hopefuly I can actually print it on a transparent sheet.

Does anybody know where I could download the template. And if there is any other good tehnique for a newb like me besides using the acetate. A note though, I don't feel comfortable using tweezers and a cutout paper of the exact diameter.

[fozzybear]

if you have access to tracing paper and a compass then this might help using method to the "same diameter to your mirror" 1

https://www.wikihow.com/Find-the-Center-of-a-Circle

Edited May 13, 2020 by fozzybear

[DaveL59]

or exactly measure the mirror diameter and draw a square on the acetate of that dimension, then draw a diagonal across from each opposite corner and you have the centre.

Edited May 13, 2020 by DaveL59

[cletrac1922]

What is it that are trying to do

Check the collimination on your Astromaster 130

Since the scope is a Dob, on a EQ mount, then easier to use a laser colliminator

First align the secondary so that the dot of the laser colliminator, is on the dot on the primary

Do not loosen the center screw of the secondary mirror, as the entire mirror assembly can twist on you

Then slightly loosen off the locking screws on the primary, and adjust the primary until the red dot disappears center of the target on the colliminator 

Then tighten locking screws, ensuring primary does not move off center

John

 

[markse68]

6 hours ago, Apprentice said:

Does anybody know where I could download the template. And if there is any other good tehnique for a newb like me besides using the acetate. A note though, I don't feel comfortable using tweezers and a cutout paper of the exact diameter.

Hi Apprentice, I agree that using an acetate template is a really good way to apply your centre spot accurately. If you pm me the diameter of your mirror and centre spot I can draw it in cad and send it you as a pdf that you can print to scale. When I’ve done it before on the printer at work it’s pretty perfectly accurate but worth checking on a paper print first then scaling if necessary for the acetate. 

Mark

[Apprentice]

8 hours ago, cletrac1922 said:

What is it that are trying to do

Check the collimination on your Astromaster 130

Since the scope is a Dob, on a EQ mount, then easier to use a laser colliminator

First align the secondary so that the dot of the laser colliminator, is on the dot on the primary

Do not loosen the center screw of the secondary mirror, as the entire mirror assembly can twist on you

Then slightly loosen off the locking screws on the primary, and adjust the primary until the red dot disappears center of the target on the colliminator 

Then tighten locking screws, ensuring primary does not move off center

John

 

Hi John.

I am actually trying to center spot my primary mirror, so that can help me with colimation. I have a laser collimator, which obviously needs collimating itself. So I created a collimating cap from the dust cap that came with my scope.

 

6 hours ago, markse68 said:

Hi Apprentice, I agree that using an acetate template is a really good way to apply your centre spot accurately. If you pm me the diameter of your mirror and centre spot I can draw it in cad and send it you as a pdf that you can print to scale. When I’ve done it before on the printer at work it’s pretty perfectly accurate but worth checking on a paper print first then scaling if necessary for the acetate. 

Mark

Thanks Mark, that would be really helpful. I will PM you.

[cletrac1922]

After seeing response from Mark, realised what you trying to do

You can print it out on OHP film which can still get from stationary stores

I use the OHP film with my Cubs and Joeys, scout groups, when doing space badge, to make a planetsphere

John