Hi, I’m new here, and pretty new to telescopes. I’ve got a problem most people would probably like to have:
I have access to two Dobsonians (14” and 16”, I think) at mcArthur Burney Falls State Park, and I plan to give stargazing presentations with them. They both appear to work fine, and there are also eyepieces (27mm, 17mm, 7.4mm) and a moon filter.
The 16”er has a Telrad sight with red circles that work, the Telrad for the 14” makes no circles, even though I’ve changed batteries.
Problem: I’m failing the simple task of seeing through the Telstar and training the scope on Jupiter! If I understand it right, the Telrad is mounted with its mirror end facing the same direction as the scope, and the viewing end closer to the telescope supports. When I have my eye next to the tube near the viewing end, so that I can see jupiter through the glass, I don’t see a hint of red circles. But if I position myself looking at the Telrad in the same orientation as the ordinary eyepiece, I see very powerful red circles, that I can control with the little handle , as expected.
Am I in the wrong position? Is it possible that the telrads 45 degree mirror is defective (I doubt it, it was used for years)? Is there a simple explanation? Is this user error (as I suspect), or could there be an actual technical problem?
Welcome to the world of public outreach ;-) (I'm an Interpretation Ranger at Whiskeytown and do all their astronomy work).
The telrad should be mounted on the secondary with the glass to the back of the unit.
Like this ->
If it's mounted this way and you're looking through the glass along the long axis of the telescope then you should see the circles superimposed over the sky. You can adjust the brightness of the circles with the lever on the side.
If everything is set up this way and you have fresh batteries in the unit then they should work fine (you may have to align then to the telescopes). If they don't then I'd recommend getting a new unit. They run around $50 per unit.
Beyond that, it sounds like you've got a pretty good setup for showing folks the night sky. Let us know when you're going to do your program and if I can swing my schedule, I'd love to come on up and see it.