Marked Primary

[ubique]

In preparation for moving the primary up the OTA of my vintage TAL1, I have removed the primary. I notice that there are some very, very fine scratches on the mirror. I presume this will have some effect on viewing though I am unsure how much. I did see another post (somewhere) where a member said he had a chip on his primary; he was told to paint it black. As my problem is with VV fine scratch marks I would imagine there would be no real impact on viewing quality. Yes or no?

[Rusty Strings]

That was me with chipped primary. There has been quite a few threads concerning marks on mirrors and the general consensus is that the primary can stand a fair amount of marks without affecting the view.

[AndyH]

If they're very fine, it'll be no problem at all. Tal mirrors have very robust coatings. I've got one that is 16 years old and looks like new!!

Andy.

ps: with the mirror out of the tube, it would be a good time to put a centre spot or one of those ring binder, sticky backed, doughnut protectors in the centre of it. This will help when collimating the mirror. One way to get the exact centre is to measure the width of the mirror and with a one of those school compasses/pencil things, draw out the circle in paper or card. Cut it out with scissors and poke the hole a wee bit bigger. Place it over the mirror and with a soft tipped pen, mark the mirror, through the hole. Makes placing the sticky backed doughnut so much easier.

[ubique]

Does the hole reinforcer stay on the primary all the time?

[AndyH]

It does indeed.

Andy.

ps: Aha....hole reinforcer..........that's what's they're called. Couldn't for the life of me, remember !!

[ubique]

It does indeed.

Andy.

ps: Aha....hole reinforcer..........that's what's they're called. Couldn't for the life of me, remember !!

At last, I've contributed something!

[GazOC]

Painting a chip black is good advice but don't do it on the scratches. I doubt the fine scratches with have any noticeable affect of the views you will get.

[Astro_Baby]

Take a look here fpor how to centre spot Cleaning the Telescope Mirrors