Anyone good with Newtonian mirrors to help? (Somerset area)

[a6400]

Hi,

I've purchased a second hand Explore Scientific 16" telescope, already managed to do some mods to it etc.

I've also imported Catseye collimation tools from USA, together with a new marker spot and a template for attaching it properly.

Just cleaned the mirror twice and went on to try to attach the centre marker, and here issues arise.

 

I cut out the template and when putting it on top of the mirror, it doesn't seem even. I have hard time telling anymore if the mirror isn't completely round and if the

current marker spot is dead centre.

I need to get that new sticker marker in the centre and it has to be spot on since it's a F4.5 scope, so low error tolerance here.

It's also recommended to remove current marker spot, but I think it's etched and might be impossible to do.

 

I wonder if anyone here has experience with this kind of stuff and could help me with this? I don't mind paying for it.

I'm not good at this stuff and don't trust my shaky hands enough. 😂

I've started a thread on CN also: https://www.cloudynights.com/topic/908268-confused-with-the-catseye-template-for-adding-centre-marker-spot/

 

I'm located near Bristol but don't mind driving a longer way, or perhaps there is some companies nearby dealing with mirrors?

Thanks!

Edited January 26 by a6400

[Mr Spock]

Easiest way to mark the centre is like this. 

Draw around your mirror. Then get a compass or similar set to the radius and draw three lines with it. The centre of those is the centre of your mirror. You can make a hole there in the paper and mark the mirror with a pen.

[bosun21]

Or you can lay your mirror on a sheet of white paper and draw around the outline of the mirror. Cut out the circle and fold it over on itself twice. Where the creases converge is the centre of your mirror. Poke a pinhole through it, place on the mirror and mark the mirror through the pinhole 

[dweller25]

1 hour ago, bosun21 said:

Or you can lay your mirror on a sheet of white paper and draw around the outline of the mirror. Cut out the circle and fold it over on itself twice. Where the creases converge is the centre of your mirror. Poke a pinhole through it, place on the mirror and mark the mirror through the pinhole 

Yup,  exactly what I have done 👍

[Zermelo]

Or bisect any two chords

[Captain Scarlet]

Before any of that, check the mirror blank itself is actually circular. If it’s not, you’ll have problems whatever you try.

Edited January 26 by Captain Scarlet

[michael8554]

"It's also recommended to remove current marker spot, but I think it's etched and might be impossible to do."

Any reason to doubt that one is in the correct position ?

Just stick the new one on top.

Michael

[Astrobits]

If the original mirror has not been replaced then I expect that it is round. If you feel the need for extra help then bring it down to me. I'm in Highbridge, about 7-8 miles from you. PM me for my contact details.

Nigel

[a6400]

12 hours ago, Astrobits said:

If the original mirror has not been replaced then I expect that it is round. If you feel the need for extra help then bring it down to me. I'm in Highbridge, about 7-8 miles from you. PM me for my contact details.

Nigel

I've placed the sticker on top of current marker although I think it's a little bit off, but I guess I will live with it.

https://imgur.com/a/BgDJkqJ

Thanks a lot for your offer!

Edited January 27 by a6400