Centre spot colour

[ultramol]

What is the best colour for a primary mirror centre spot to enable me to see it when collimating. I have a SW 200p wich has a black one but this just blends in with the secondry reflection and makes it very hard to see. I wear glasses if that makes any difference....Thanks in advance....Geoff

[JamesF]

I think most of the ones I've seen have been white.

James

[kalasinman]

I have a sort of metallized on that works quite well

[Charic]

You could hide the reflections by inserting some card / paper between the secondary and primary mirror. This reduces reflection errors whilst setting the secondary. As for a new centre spot, the paper ring binder strengtheners are more than suitable, slightly larger than the original spot, and often recommended to be blacked out using felt pen. You will need to see the spot at some stage when aligning the primary. A black spot/ring shows well using the Barlowed-Laser method when setting the primary mirror. Either colour, you just need to aim the scope at a bright source, a wall or sky in order to better see the ring.

HTH.

[ultramol]

Thanks very much for your replies. I am going to try a ringbinder in white and see how that goes...Regards   Geoff

[Thom]

I just added a dot in the centre of the primary with a blue Sharpie.

[Charic]

That might create an issue, as a dot is just too precise a mark, and obviously a lot harder to see. Let the folk here know how you get on with this method?

[Thom]

Oh, very well.  Its been in place for a couple of years.  I had to re-apply it after washing the primary as it's not as indelible as I was lead to believe.  I tend to colimate during the afternoon before I know I will be out for a session and my scope hangs on to collimation really well - only need to adjust it 3 or 4 times a year.

[Charic]

Thats seams reasonable.  Handle with care is my motto, I  tell that to  the Mrs,  just be careful around the scope?