Secondary mirror support

I've discovered that the main problem with XT10 collimation is alignment of
the secondary mirror. With the laser collimator in place, I lightly tapped
on the spider vanes and watched in dismay as the red dot walked its way out
of the center dot on the primary and _half way_ across the 5" radius!!!

I want a new secondary holder (waahhh!).

--
-Stephen Paul

With the laser collimator in place, I lightly tapped
on the spider vanes and watched in dismay as the red dot walked its way out
of the center dot on the primary and _half way_ across the 5" radius!!!

I want a new secondary holder (waahhh!).

--
-Stephen Paul

Which XT-10 secondary support do you have, the newer 4 vane or the older 3 rod
support? I find my XT-8 with the 3 rod support is quite sensitive and normally
needs repositioning before viewing, however it does seem to stay in place
during the evening.

My OPT Starhunter 10 has the newer 4 vane support and I have found it to be
very stable. I took it on a 2000+ mile trip across the southwest, taking it in
and out of the motorhome every night, banging it around and it never needed
recollimation.

I think the problem with those rod supports on the older scopes is that the
secondary holder can easily rotate about one of the rods and the other two rods
can switch modes. This is similar to a bicycle wheel, the secondary being the
hub. But bicycle wheels stablize the end to end rotation of the hub by having
spokes at each end of the hub, not just one set in the center. This is really
the flaw in the rod design.

I think my making sure everything is tensioned and all jam nuts tight, one can
improve the stiffness.

Best wishes

jon

"Jon Isaacs" wrote in message
...
With the laser collimator in place, I lightly tapped
on the spider vanes and watched in dismay as the red dot walked its way
out
of the center dot on the primary and _half way_ across the 5" radius!!!


Which XT-10 secondary support do you have, the newer 4 vane or the older 3
rod
support? I find my XT-8 with the 3 rod support is quite sensitive and
normally
needs repositioning before viewing, however it does seem to stay in place
during the evening.

Yep. It's the GS model, which has the rods. I'm just glad I finally figured
this out. As may be evidenced in the saa archives, I've been a little
frustrated with collimation on this scope a couple of times. (I don't mind
tweaking the primary however many times it takes duringa session, but
futzing with the secondary is just too time consuming).


I think my making sure everything is tensioned and all jam nuts tight, one
can
improve the stiffness.

Thanks for the support and advice. I have to admit that I loosened all of
this up once a long time ago to understand shifting the secondary. Serves me
right. ;-)

-Stephen