Question regarding what I'm seeing

I'm kind of befuddled on this, and would like some opinions. First, a question regarding Jupiter. In all my eyepieces, I'm noticing that Jupiter just isn't sharp. Seeing aside, even on mediocre nights I can still get a sharp low power view, but it mushes in and out, and when it seems just at that sweet spot, there is almost a double image around part of the limb. Now, when I look at the Moon or deep sky stuff, I don't see it, but ever since my rebuild I just can't get it good enough.

I rechecked and adjusted (thinking that was it) the spider, centering it. I'm using the Collimation Handbook, btw. My focuser is square and the secondary centered in each axis. I use a laser collimator to center the secondary, then a Cheshire for the primary. Even so, I'm not quite happy. Does anyone have any ideas?

Also, I have started using a pair of 16 t5 nags I just picked up off astromart. I'm noticing on bright objects, when racked out of focus, there are dark marks like some ink blot test. The images rotate with the eyepieces, so it's not the Denk. When I focus in, they disappear, and all is well. But I'm disturbed by them, b/c I don't remember seeing them in my old pair of 16's. Is this normal?

Thanks,

Guy

Guy Earle said:

I'm kind of befuddled on this, and would like some opinions. First, a question regarding Jupiter. In all my eyepieces, I'm noticing that Jupiter just isn't sharp. Seeing aside, even on mediocre nights I can still get a sharp low power view, but it mushes in and out, and when it seems just at that sweet spot, there is almost a double image around part of the limb. Now, when I look at the Moon or deep sky stuff, I don't see it, but ever since my rebuild I just can't get it good enough.

I rechecked and adjusted (thinking that was it) the spider, centering it. I'm using the Collimation Handbook, btw. My focuser is square and the secondary centered in each axis. I use a laser collimator to center the secondary, then a Cheshire for the primary. Even so, I'm not quite happy. Does anyone have any ideas?

Also, I have started using a pair of 16 t5 nags I just picked up off astromart. I'm noticing on bright objects, when racked out of focus, there are dark marks like some ink blot test. The images rotate with the eyepieces, so it's not the Denk. When I focus in, they disappear, and all is well. But I'm disturbed by them, b/c I don't remember seeing them in my old pair of 16's. Is this normal?

Thanks,

Guy

If you're using binoviewers your binos could be out of collimation. Your testing of the SCOPE should be done with a single eyepiece. When that is spiffy if there are other problems that would be the binoviewer. Binoviewers and binoculars can go out of collimation and the results lead to noticeable deterioration of performance.

The black stuff sounds like your eyepieces need to be cleaned. When you are out of focus you see it and it is blurred out when you are in-focus. Try Purosol and kim wipes or unscented high quality kleenex.

A blower is nice.

regards
greg n

I rechecked and adjusted (thinking that was it) the spider, centering it. I'm using the Collimation Handbook, btw. My focuser is square and the secondary centered in each axis. I use a laser collimator to center the secondary, then a Cheshire for the primary. Even so, I'm not quite happy. Does anyone have any ideas?

Guy: I don't know if you have resolved this or not... So, if you have, great...

If you haven't here a couple of thoughts... As Greg said, binoviewers and/or seeing... Definitely two possibilities. You can resolve the binoviewer question simply by removing it and looking with one eye.

It is also possible that your scope is out of collimation. An out of collimation scope will give that double image... Maybe the center spot is slightly off, it doesn't take much, at F/5 collimation tolerances are less than a mm..

Also, since your a using a laser, it is also possible that the laser itself is out of collimation. I am generally quite happy with Asian optics but the Asian made collimators seem to have collimation problems of their own.

For setting the tilt on the primary, I would suggest using the barlowed laser technique rather than the cheshire, at least that what works for me with my fast Newtonians.

Since this is a new configuration for your scope, it is worth checking to see if the collimation shifts as you move the scope from horizontal to vertical.

Anyway, hope you have already solved this problem and are getting great views.

Jon