Telescope Reviews: How close is Canon IS image to mounted view?

That's the method I've been using. BTW, I found it impossible to hold the IS button down and attempt to refocus the right diopter. with my left hand.

Last night I viewed Saturn. I compared the 15x50 to my 15x70 Ultra.

I mounted the 15x70 Ultra and could see the points of the rings sticking out both ends. I handheld the Ultras and Saturn was swimming around rapidly and I could no longer hold it steady enough to see the points.

I mounted the Canon 15x50. Without IS turned on I could barely see what I thought were the points of the rings sticking out. With IS turned on I could not see the points sticking out and the disk grew to be slightly misshapen.

With the 15x50 off the tripod, when I turned IS on, it would settle the rapid movement to a slow easy to follow sway. But the image was no better. Saturn looked slightly out of focus and I could not improve it by refocusing the main focus dial.

So I tested these two with/without tripod on a resolution chart. I suspected readings were probably a step low all the way around since these are not in bright light. That's normal for lower light level. FWIW, the best reading I've ever achieved with the Ultra was one half step lower, 5.8 arcsec (84 apparent). The finest readings I've ever achieved with mounted regular 15x70s was 6.5 arcsec, with the Nikon SE 12x50 7.0 arcsec (84 apparent). Lower apparent readings are better.

Obie Ultra 15x70
mounted 6.2 arcsec (93 apparent)
handheld 8.7 arcsec

Canon 15x50 IS
mounted 6.9 arcsec (104 apparent)
handheld 9.8 arcsec
handheld w/IS 7.8 arcsec

FWIW, I tried handheld first and could not focus either binocular fine enough on the moving target to do this test. I needed to rest the binocular on the banister to get decent focus. Also I tried several of these readings several times, so these are the best readings I got, I had some worse readings.

Comments on above. Without a doubt the IS engaged is causing the lines to blur. It's still better than the 15x70 handheld, but not as good as the Canon mounted and not near as good as the Ultra mounted.

The Ultra handheld could not be held steady enough to see as fine a detail, but the image quality was better. The lines that I could see were sharp and dark. The lines I saw in the IS were fuzzy bblurred and grey.

If all you ever compare is the handheld difference in the images, my guess is that you will be so wowed by the difference in the images swimming (or not swimming with IS), that only few would be looking for the finest detail to see which really has finer image quality. The target size I'm seeing finest details on ranges from 10mm to 7mm at a distance of 100 yds. 10mm was the poorest reading. So, comparing the quality of images requires the observer to see a 7-8mm target at 100 yds and the lines are about 2mm thick. That's much smaller than Saturn in the test above.

edz