Centre spoting primary mirror

[REG78]

Hi all just got a skywatcher 130-900f mirror doesn't seem to be centre spotd what the best & easiest way to do this & why do they not com centre spotd when bought new for the user any ideas

[Dave In Vermont]

Here's a paper by Gary Seronik, a well-known writer on telescopes and their optics:

http://www.garyseronik.com/?q=node/168

And, if you prefer, a youTube on the subject:

 

 

Hope these help!

Dave

 

[Knighty2112]

I used a small drop of correction fluid to mark the centre of my mirror that also wasn't marked, and then a pen mark on this to mark the very centre of the mirror also. Works OK for me. 

[REG78]

Cheers Dave much app