Celestron Star Diagnal

[valleyman]

Is there a proven sure way to colimate a Star diagnal. Mine has a loose prism. Anything viewed with it moves out of view when the diagnal is rotated 180 degrees.

Or is it just hit and miss to get the prism set correctly.

[John]

Is there a proven sure way to colimate a Star diagnal. Mine has a loose prism. Anything viewed with it moves out of view when the diagnal is rotated 180 degrees.

Or is it just hit and miss to get the prism set correctly.

Most diagonals have mirrors rather than prisms. I used to have a Celestron prism diagonal and I seem to recall 2 small grub screws in the side of the diagonal body are used to hold the prism in place - you can see one of them in this picture:

http://www.365astronomy.com/images/94115-A_diagonalstar125_large.gif

You could see if those are loose.

Otherwise you might want to think about getting a new diagonal - they are not too expensive and its a pity to compromise the views for the sake of a decent diagonal.

[NGC 1502]

Hi Pat, perhaps, after trying post #2, you could try dismantling, & see if the mirror or

prism is loose on its seating. Most of these diagonals are quite simple in construction.

If its a recent purchase, then just return it ?

The mirror/prism could be refixed with a dab or two of silicon sealant. But of course,

any dismantling could make things worse, but if it is u/s then you have nothing to lose.

Regards, Ed.

[valleyman]

Have stripped it down Ed, it is on a pivot and the only thing that keeps it level is a flat spring under the back plate. Will test my adjustment next time I see a star. If it is still way out...will get a new one.

[NGC 1502]

Hi Pat, sorry, not seen that type, with a spring holding the prism, but sounds like a

bit of tinkering could sort it maybe ? Perhaps its doable in daylight, viewing a distant

object, at fairly high power, & rotating it to check, as your original post.

Good luck ! Ed.

[John S]

Ive not seen this type, the only one Ive seen have grub screws on the side of the diagonal the same as binoculars which also have bonding inside on the prism corners to stop it moving sideways.

Perhaps its possible to pack around the prism to stop it moving.