Erik, the problem with the binoviewer in daylight isn't one of comfort. Yesterday was on the cool side and quite pleasureable. I wear a brimmed had when observing the sun, and have been known to set up in the shadow of a building when the geometry works out. The difficulty with a binoviewer in daylight is that the pupils of your eyes are as small as they ever get. Combine that with long eye relief of a low-power eyepiece and a small exit pupil from high power (thanks to the relay Barlows) and a small objective aperture, and you have two very small "sweet spots" that you have to align perfectly in order to use the binoviewer. The net result is a pair of very small virtual images floating far from the eyepieces, that have to align perfectly with a pair of small eyeball openings. Inter-occular spacing must be dead-on, and your head placement must be dead-on. A shift of only a millimeter or two means you lose one or both sides of the image. Can you hold your head still within a millimeter for 10 to 30 seconds? I find it VERY difficult if not impossible, outdoors perched on a chair. A sun shade won't affect this problem much, if any. Your pupils will still be very small and most folks don't have the body control of a Hindu yoga master. Using large aperture will help. That will increase the size of the final exit pupil, so even if the observer's pupils are completey contracted, there is more "wiggle room" for head positioning. That's why at SPOC, I'd rather use a binoviewer on the Andy scope for public viewing, than on a PST or double-stack. And a double-stack image is inherently dimmer than the PST in the first place. In a binoviewer it would be even dimmer. Unless your solar imaging system provides a large exit pupil, binoviewers are much easier to use at night, when your entrance pupil is open 5 to 7mm. Head placement is not as critical, by a long shot. On Sun, Mar 31, 2013 at 9:01 AM, <erikhansen@thebluezone.net> wrote:
I've always found a big sun shield to be essential for pleasurable sun viewing.
Here's the pic of the PST/binoviewer setup, on my small GEM:
http://i260.photobucket.com/albums/ii24/JethroTull1958/ATM/PSTampbinoviewer0...
It was pretty neat seeing the sun in H-a with both eyes, a first for me.