Got a beginners' question? No matter how elementary, our friendly forum community and magazine writers will answer it.


Postby Premacy10 » Sun Mar 27, 2016 3:38 pm

Hi all

I owned my last telescope as a child some 40 yrs ago and was keen to get back into the hobby.

New to the forum having owned a telescope for a couple of cloudy months.

I have just purchased a laser collimator. Watching the videos on line the primary mirrors appear to have a centre circle donut to align the laser. My 130 does not appear to have this donut.

Is this normal for cheaper telescopes and do you have any tips to collimate or is it with the naked eye to align to the middle of the mirror.

Any help would be greatfully appreciated as I have seen Jupiter and its moons and 2 fuzzy brown rings on the planet but feel I am not getting the correct focus.


Posts: 7
Joined: Sun Mar 27, 2016 2:06 am


Postby Gfamily2 » Sun Mar 27, 2016 5:56 pm

Hi Tony
Welcome to the forum.
I centre marked my own first telescope and it's relatively straightforward.
Here's some instructions that show you what to do...

Basically, you remove the mirror in its mount and cut out a circle of paper the same size with a hole in the centre.

Carefully place the circle over the mirror and use the hole to put a small dot on the mirror with a fine permanent marker.

Then get a reinforcing ring from an office supplies place and carefully position it so that it is accurately positioned with the dot at its centre.

Press firmly in place with the rubber end of a pencil - and remount the mirror.

Sounds daunting, but it should be straightforward. If you have a local astronomical society, you'll probably find someone there who has done it themselves and will be able to help.

The site above seems to suggest that you need to remove the mirror from the mount, but that's not necessarily needed. I didn't need to do that with mine.

Just remember that the mirror coating is on the surface and is easily damaged, so avoid anything touching it or rubbing across the surface with any force. Don't touch it with your fingers as the grease will mark the mirror and will be almost impossible to remove.
Scopes: Meade 8" SCT, Skywatcher 127mm Mak, Raffle winner of SW ST80
For imaging: Pentax K5, Asda webcam, Star Adventurer (new toy)
For companionship: Mid Cheshire Astronomical Group.
(Not a moderator)
Posts: 522
Joined: Thu Jun 25, 2015 10:38 pm

Return to Ask a silly (astronomy) question

Who is online

Users browsing this forum: No registered users and 0 guests