I'm really enjoying the use of binocular telescopes and have recently started using some higher magnifications just for grins. These are being used in a light polluted driveway.
The little 80mm asymmetrical will do 67X well, the 127mm asymmetrical has been up to 117X so far. Last night I was out with the RB-66 at 275X. Saturn, Jupiter and the Double Double were very cool. All this is with cheap eyepieces so I'll soon be looking for some good options in the 3-4mm range. I've got a BH 24-8 zoom with 2.25 Barlow and the smartest thing might just be to pick up a second. If you know some good pairs please recommend them.
My next build was going to be another asymmetrical using two 102ED F/7.5 objectives but after last night I may go to a 10" F/6 reflector bino and then later do an 80mm ED or APO as a companion. The 80mm would have the portability and be great for widefield and might occasionally let me get up near 200X. It is going to have to really handy though to push the RB-66 out of the line up. Going from 31X at 2.1 degrees to 275X is nothing to complain about.
I have no optical experience and do pretty much everything by intuition, trial and error with strong emphasis on the third component. I'd be happy to benefit from the knowledge of those with pertinent experience, theoretical or practical.
The only way I have found so far to merge the image in a binocular telescope is to have the two individual fields of view be asymmetrical. For example once I've aligned the scopes to merge the image Polaris appears about 10' right of center in left tube's FOV and about 10' left of center in the right tube's FOV. This seems to be reasonably consistent in the three binoscopes I have access to. This is accomplished in each scope by slightly converging the physical axis of two individually collimated tubes. I just point the two tubes in slightly. Using this method I've been able to achieve comfortable merging from 13X up to 275X so far.
The result is often, but not always, an apparent field stop that looks like the old TV rendition of someone looking through binoculars, a figure 8 on its side, sometimes wider, sometimes narrower. It works but if there is a way to improve my optical train I'm all ears.
Initially I thought I just need to get Polaris centered in both tubes and stick my eyes to the eyepieces to see a merged image. For most people this probably is all there is to it. The more I thought about it though it occurred to me that to get a star in the same place in the two fields of view and have the small degree of convergence of the two lines of sight I seem to need would require the eyepieces to be separated by some huge distance. Even a small fraction of a degree at near infinity is a long distance. So a permanent fix may not be in the cards. Easy adjustability and an elongated field stop may be the best solution. I'm hoping someone can tell me I'm wrong, not a new experience for me.
I don't think this would be an issue for most people. I suspect I have optical or neural issue. My wife would definitely go with some form of brain defect but in my defense my right eye has always been significantly weaker. I notice I tend to rotate or tilt my head so the stronger left eye is forward and/or higher. Every thing I see includes the left side of my nose. At any rate I struggle with merging. I've recently read a little about adult strabismus, whether real or quackery I can not say. Back in my non politically correct youth they just told me I had lazy eye which seemed of a piece with the rest of me.
I do want to say even if there is no better solution the results I get now are still wonderful.
Thanks in advance for any thoughts and for any eyepiece recommendations.