Author Topic: 11mm Delite - lots of scatter and ghosting  (Read 33 times)

sanddotshanpens

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11mm Delite - lots of scatter and ghosting
« on: December 31, 2017, 09:04:16 PM »
So, a while back I purchased an 11mm Delite to fill a magnification gap in my collection. I bought it primarily for observing the planets and Jupiter. My initial first light impressions were positive, but until this morning I've, not really been able to give it a fair test on the planets due to seeing conditions and terrible mirror shift.

Prior to this morning, I noticed that every time I observed jupiter, there was a lot of scatter - and what seemed like an obvious ghost reflection from my eyeball. I chalked it up turbulent seeing and my diagonal being meh, and didn't worry about it that much since there wasn't enough detail to really do a planetary comparison with.

Well this morning I had good seeing and a brand new Feather Touch crayford to resolve fine focusing issues, so I decided to take it for another spin and do a comparison with other eyepieces in my collection.
On axis, it is very sharp, but I observed a tremendous glow around the planet + a ghost glow which I think is reflection from my eye. When I placed Jupiter just outside the field of view, the whole field lit up with a very obvious glow. Thinking it was my 2" diagonal, I switched it out for my stock 1.25" diagonal that came with the scope. The cheaper diagonal definitely made things worse, so I figured maybe my 2" diagonal wasn't so swift either.
To eliminate the diagonal as a source of scatter, I placed the eyepiece directly in the back of the scope with no diagonal and repeated the tests. Same problem as in the 2" diagonal, meaning the source was the eyepiece.

For comparison, I did the same tests with my 12mm Nagler Type II, new 17mm ES 92, and 20mm Plossl + Barlow.

None of those showed nearly as much scatter as the 11mm, and none showed any sort of eyeball reflection ghosting (or whatever it was I was seeing).

The overall sharpness and contrast with the barlow + plossl was definitely worse than the Delite alone, but the 12mm Nagler Type II had noticeably better contrast, and the 17mm ES 92 also had better contrast and sharpness (though being lower power, not surprised the sharpness was better).

Here's a simulation of what the view looked like in the 11mm Delite. The offset glowing ball seemed to move when my eye/head moved, but was also somewhat dependent on where Jupiter was in the field (which is also to be expected I suppose).

This is a simulation of what it looked like with jupiter in the field:

And just outside of the field:
Based on this mornings observations, I'd have to say the 11mm is a dud for planetary viewing. Will be doing more tests as the skies permit, but a bit disappointed with it for the time being.