The main attraction would be things like the Veil nebula in Cygnus. That would be wonderful I expect with binoculars. It might make more sense to put filters on the OB 15x70s for that. I have the 22 and 14mm XL eyepieces, and their 1.25 inch tubes aren't as long as those of the Pentax eyepieces. So it's possible one of those might work. The 14mm is probably the more likely of the two. I'll try that.
It was a miserable evening to observe. lol So hazy I couldn't make out the keystone in Hercules, which I can usually see easily. As predicted, the Double Double is fully resolved with the 5mm XWs, thought the E1 components are still challenging due to the magnitude difference between them. Also 112x is definitely the highest magnification that is manageable with the current mount configuration. We'll see if the 117B is a little more steady. A much more substantial mount is needed to use higher magnifications with these instruments.
The OB 25x100 shows some CA on bright stars like Lyra where the 100XL-SD doesn't show any, but that is really the significant difference between the views. And the CA exhibited by the 25x100 is not objectionable for deep sky observing. It's well constrolled. I'll spend more time doing side by sides on a better night, but the Deluxe is remarkably fun to observe with. Really an unbeatable value at $470 USD.
Neither instrument exhibits tails or other conspicuous artifacts. With the 25x100 eye position is more critical than with the 100XL but it is still comfortable for me with or without glasses. And a single set of the Pentax XWs cost about $100 USD more, which makes the performance of the 25x100 even more impressive. The Pentax XWs are hands down the most comfortable eyepieces I have ever used.
I didn't get the TV-101 out, but the stars in either binocular aren't as needle sharp. They are sharp enough though to provide excellent views.
Rho Hercules was beyond what I could muster this evening -- near the zenith in a murky sky so I skipped it. But 70 Oph was a fine sight -- well resolved with a blazing warm white primary and a deep amber companion. Definitely makes my list of outstanding BT double stars.
When I was tracking down 70 Oph I wandered too far east and came across the open cluster NGC 6633 on the border between Ophiuchus and Serpens Cauda -- an enjoyable object even through all the murky soup. Viewed it with the 100XL-SD and Pentax 20mmXWs, which provided a nicely sized field for the cluster.
Edited by Fiske, 14 July 2021 - 09:13 AM.