Greetings all, I've just joined this group. I live in Chester, England and have an 8.5-inch f/5 Newtonian built in this country in 1988 by a now defunct firm...
I am not the moderator, but I will say welcome aboard anyway. I have my 8 inch mirror out of the cell at present hoping to send it off for re-aluminizing...
Sounds like you have a nice instrument, and use it frequently. I'm older and lazier now, so I don't observe as often as I want. That 8.5" will outperform what...
Thanks Wayne. Yes, the main difference I've noticed with the plate glass mirrors is that the images are awful for the first 1 - 2 hours after taking the ...
That's my experience also. I had a 10" with a plate glass mirror. Unfortunately, in those days, I rarely had the time to set up and let the thing cool...
Greetings all, I wonder if anyone can help me with a spot of advice. Recently I've been getting 'triple' images from my 8.5" f/5 Newtonian. I've had the ...
What eyepieces were you using? What altitude above the horizon were the objects in question? How cold was it and much thermal stabilization tim did you allow? ...
I should have stated that I began observations within about half an hour of setting the instrument up outside (tube assembly had been in a heated room). The...
Try rotating the eyepiece in the focuser to see if the image defects rotate with the eyepiece or stay stationary. What brand of Kellner and Ortho? -Chris...
Thanks Chris. The triple images always retain the same orientation, no matter what the position of the eyepiece. However, they are slightly different inside...
Okay, given everything you have said, I think I would be looking at possibly upgrading the 3-point suspension mirror cell to a 9-point cell. Hopefully other...
Thanks Chris. I feared you might say that! The flat is supported on a single strut across the entire diameter of the tube. If you are using ... Good idea. I...
... I guess we're assuming the axial collimation is good. Trilobal images, I usually suspect astigmatism (even if the symmetry is different inside and outside...
Vic, Thanks for your response. You may have hit on something here:- I've also seen cemented ... This telescope does indeed have a cemented flat. When the...
Vic, ... What is "axial" collimation? Is just the collimation of the mirrors? Could poor collimation produce overlapping images of the kind I describe? In...
Guys, Had the original post simply stated that he was getting multiple overlapping images at best focus, I might have been with you on some sort of stress or ...
You've made some very good observations Wayne. I'm certainly not an expert in these matters, but I have messed with Newtonians for about 40 years. In my own...
Wayne, Larry and all, It's certainly a puzzle for me, too! I'm very grateful to all who have contributed their views for the care and interest you've all...
... Axial collimation is correct when both the focuser axis and the primary mirror axis are collimated and coincident. (The other aspect of Newtonian...
... At f/5, remember to use a Cheshire or Barlowed laser to get the best primary mirror axial collimation. Even a perfectly collimated simple point source...
... I have seen failed coatings (on a diagonal) that delivered multiple images, but they weren't multi-colored. I'm not saying that they couldn't be, and the...
Mirror dudes (and dudettes): Sharing a tidbit of information: Yahoo is now using something called "Web Beacons" to track Yahoo Group users around the net and...
Need help deciding on next telescope. Started with ETX 90, graduated to a C6. Now want to try imaging. The dreaded word, collimation rears its ugly head when I...
Collimation isn't a big deal really. Sort of just getting used to whatever scope you decide to buy. What kind of astrophotography are you looking to do? ...
Ease of collimation varies between different designs. As a rule, however, it is not difficult, especially after you've been through the process once or twice....
Would like to try ccd and digital. Digi first to get the hang of it. Limited budget around 1500 for scope and imager. Would like honest opinions of Celestron...
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