I have used a pair of Swaro 8.5x42 EL for stargazing (and general daytime use) for more than a year and did a bit of comparing with my older Pentax PCF WP II 10x50's. I found the brightness to be roughly equal between the two when viewing DSOs which I was quite pleased with given a 30% smaller aperture area compared to the 50's. The big difference was in the field of view, the sharpness all the way to the edge and the calm and stable image offered by the lower mag and lighter weight of the 42's. A great visual experience using the swaros but more for the image quality than the ability to go deep (compared to the 10x50). I did briefly try a pair of swaro 10x50 ELs that I took home from the store but ultimately swapped for the 8.5x42s. Tried them at dusk to view the treeline and for observing the moon and was astonished by the brightness of them. Unfortunately I didn't use them in darkness for proper stargazing so I can't say how they would compare, although my guess is they would be a significant step up in the ability to view DSOs. What put me off was the shaky image. Although not shakier than your usual 10x50s I just found that I valued the calmer and wider FOV of the 8.5x42s more and realised that as allround binos I would probably use the smaller and less heavy 42s more often. I do wish I had a chance to compare the larger swaros to my 42s during a proper stargazing session, must admit I am quite curious to see the difference.