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Two eyed vs one eyed

Started by EdZ, 04/20/2003 01:55PM
Posted 04/20/2003 01:55PM Opening Post
Saturday night April 19, 8:00 to 11:30
Start night mag 4.5, by end of night mag 5.0* little dipper was vis
Darker skies towards SW, the area I was viewing.
Seeing sometimes wavering, most times still, crisp.

Last night I used the Fujinons 16 x 70s to do a left eye, right eye, both eyes test. Squinting closed I saw far less out of the other eye. Standing and leaning back I wavered a bit too much and again saw less. Finally, I went and got a lawn chair, set it under the UA Unimount Light. After I put a pillow behind my neck I had a nice comfortable seat, nice sturdy rig, settled in, little bumps damped in 2 seconds. Then I was able to concentrate on the task at hand.

Earlier I verified that M44 was rich in faint stars. I counted 80 stars in the region with my Oberwerk 20x80s and I counted 130* in the same region using my CR150 with a 27Pan. There were more than enough faint stars that I would not be able to reach the faintest magnitude stars in the area and be counting all there was to count. I found a stream of faint stars to the right of center from the NW to the SW of approx 20 of the faintest stars seen in the binocs. This was my test area.

When I first started, I wasn't being exact counting and I was convinced I was seeing all there was to see whether with two eyes or one eye. Finally, I recorded four or five successful counts with each eye and with two eyes. The counts varied with each attempt, but I always got counts of 14 or 15 in my right eye 15 or 16 in my left eye (my scope viewing eye) and 18 or 19 with both eyes.

Rather than close one eye in a squint, I covered my other eye with a thin black glove. The most notable difference is it was just so much easier to sit back and look with two eyes that everything popped into view and a few averted vision stars appeared in the two-eye viewing. There were a few stars in the sorrounding fileds that I did not see when I was standing. I was very clearly able to see better settled in the lawn-chair with all motion quieted down. The end result is I did see more in my test area with two-eye viewing. My results spread from a minimum difference of 16* to 18* all the way up to a maximum difference of 14* to 19*. The difference between the best reading with my scope eye to the best reading with two eyes of 16* to 19*, was an improvement of almost 20%.

In the past I never really accurately measured this. Regardless of what I thought in the past, this clearly indicates to me the degree of improvement with two-eye viewing. Certainly it will vary with the individual but this is at least an indication that it’s not just a marginal gain but more of a factorable increase.

Posted 04/21/2003 01:15PM #1

As you know there is a fair amount of controversy in respect to this subject as we have both read and participated in it on the "Binocular Astronomy" Yahoo Group. I do agree that binoculars will enhance the view of extended objects, that is not questioned. I can personally attest to how much brighter and even dimensional objects like M-27 or the Andromeda galaxy look in binoculars.

Perhaps the fact that I am amblyopic (lazy left eye, with patch on the good eye as a kid, exercises, etc.) is part of the problem. Today my distance vision is excellent in my right eye at 20/10, it is about 20/30 in the left eye. I do have problems fusing bright point sources such as Sirius and the brighter planets. I have no problem with the Moon, and with stars dimmer than 1st magnitude. However my suspicion is that this amblyopia could play a role in why I can perceive no increase in brightness of point sources when using binoculars in comparison to telescopes.

One advantage of this amblyopia is when I do observe thru a telescope, I do not have to squint or close the other eye. In effect I look thru a telescope with my good right eye, and just leave the weaker one open. This is not distracting to me and is probably an advantage while looking thru the telescope.

I compared my University Optics 80 mm f/6.25, fl. 500 mm telescope on a Gibraltar mount and utilizing a 26 mm TV plossl for 19.2x and also a 17 mm plossl for 29.4x with TV Everbright diagonal to my Miyauchi 20x77 binoculars on a Bogen tripod. A pair of Miyauchi 30x eyepieces was also used along with the stock 20x pair.

My target was an easily findable grouping of stars immediately east of the star Pollux in Gemini. Space does not permit a description of this group of stars. I will add a second post about that. Curiously I coud personally not see any improvement in two eyed viewing with the binoculars vs. using just my better eye in one half of the binoculars at a time, try as I might. There was a marked improvement in the visibility of these faint stars when I switched to the 30x eyepieces. The "visible now, not visible then" disappeared, while still faint, I could always see them.

After using the binoculars, I switched to the telescope and found that the faint stars were immediately and very clearly seen as sharp, well defined points at 19x. While 29x helped, it was not necessary. No averted vision here, moving away from them and then back and they were easily seen again. In fact the telescope found another faint star below the southernmost of the 8th magnitude stars. It was faint and distinct. Moving back to the binoculars this star was hard to see, but eventually I did. It kept fading in and out.

As always, your mileage may vary, but I personally can see no advantage in terms of pulling in fainter stars, with two-eyed observing. Extended objects are seen to advantage in binoculars.


Barry Simon