Telescope Reviews: upgrading from 15x70

I am not sure whether this will help Nick, the OP, as this thread is a few months old by now, but I just received a pair of GO signature 15x70s (same as Ultras), and have had the Obie 20x80 Standards for quite a while now. So, this post is sort of a first impression of the 15x70s but also bit of comparison to the 20x80 as it relates to Nick's original question.

I got the 15x70s to fill the gap between my 12x50 Nikon AE's and the 20x80s. I wanted something with more reach than the Nikons, but more field of view and overall sharper optics than the Obie Standards. I wanted something with good contrast for cruising the MW and pulling out faint galaxies and nebulae. My BT-80/45s are the king of my driveway for this, but they are not the tool for quick looks or grab&go portability. So, I am hoping the 15x70s will deliver the contrast and quality of the BT80, at the lighter weight of the 20x80 standards.

I want to emphasize that this is a first impression 15x70s. These were just delivered yesterday. It has been mostly cloudy if not raining since they arrived. I was able to catch some terrestrial targets yesterday, and last night I got glimpses of the 1st Qtr moon, but I have yet to use the 15x70s on their intended targets (starfields and faint targets).

Concerning the fit and finish, the GO Sigs are excellent. Their weight is in the same ballpark as the Obie Stds, but GOs are waterproof and seem much more robust. The GO independent focusers are smooth but tight, compared with the center-focus Standards. Both have fold down eyecups; "up" or "down" on the GO Sigs, three positions on the Ob. Stds. The mounting bracket included with the GO Sigs is nice.

I set the two binoculars on tripods in the driveway and aimed them at a roof top a couple hundred yards away. Through the GO's, most of the shingles came through in very fine focus, and could discern several details of paint drips and such. The focus was only a little soft on edge. In the Ob Stds, the image scale seemed much bigger and was more comfortable. The field of view for me was only SLIGHTLY less in the 20x80s, due to the fact that I wear glasses and could not take in the whole view with the GO Sigs. This was the most disappointing aspect of the comparison. While the GO Sigs did have a wider field with sharp focus reaching closer to the edge, I had to take off my glasses to appreciate it. Neither of these binos is comparable in TFOV to the 12x50 AEs, as you would expect. For terrestrial use, I much preferred the Obies or Nikons. On the moon, the increased scale of the Obies also won out over the GO Sigs. Although there was a bit less CA in the GO Sigs, I did not find it irksome in either instrument. Again, the Ob Stds were much more comfortable to use.

I will update this impression as I get to use them under better nighttime conditions. But initially, I would say that the GO 15x70s are a better-built, sharper instrument, and the Obie Stds have a bigger scale and are much more comfortable to use with glasses. I know the OP mentioned he uses no glasses, but while wearing mine, the benefit of the somewhat larger and flatter TFOV was negated. My initial bias toward the Obies may be premature, but if the the 15x70s don't really show better contrast under dark skies, I will be hard pressed to keep them. That is a hard statement for me to make considering the overall high quality of these binos. Time will tell,

--Tad

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Orion XT8i, Vixen ED80Sf, Oberwerk BT-80/45
20x80 Oberwerk Std., 12x50 Nikon AE,
10x42 Celestron Regal LX, 8x40 Pentax PCF WP