Astronomy binoculars
Two 10x50 porros from known makers: what actually differs?
Same magnification, same aperture, same 5 mm exit pupil, the classic geometry for the night sky. Neither listing publishes a field of view or a weight. What separates them is what each chooses to say about coatings, eyecups and mounting.
| Compared on | Action 10x50 | Jupiter 10x50 (65912) |
|---|---|---|
| Aperture | 50 mm (1.97 in) objectives | 50 mm (1.97 in) objectives |
| Magnification | 10x | 10x |
| Exit pupil | 5 mm (0.20 in) | 5 mm (0.20 in) |
| True field of view | Not published in the listing. | Not published in the listing. |
| Prism type and coatings | Porro prisms · multilayer-coated lenses | Porro prisms · multi-coated optical elements |
| Eye relief | Long eye relief design for eyeglass wearers, stated · turn-and-slide click-stop eyecups | Not published in the listing. |
| Tripod mounting | Tripod-ready, stated (adapter needed) | Optional Pentax TP-3 tripod adapter |
| Listed on amazon.com | Yes | Yes |
A tick means one listing published something the other did not, or published a better figure. It does not mean the product is better, and the column is not a score out of anything: a maker who says less loses lines here without losing a comparison. The two verdicts below are where the page is settled.
The one for glasses. Nikon states a long eye relief design and click-stop eyecups, which is what decides whether an eyeglass wearer sees the whole field. It was about $30 more on November 7, 2026, and Amazon’s item data puts it at the heavy end for a 10x50.
The one for the money. The same 10x50 geometry with multi-coated optics and a named tripod adapter, at about $99 sold by Amazon. Without an eye relief figure, eyeglass wearers should check before buying.
Fifty millimeters gathers enough light for clusters and the Milky Way, and the 5 mm exit pupil suits a dark-adapted eye. Ten times is about the most that can be held steady.
Yes, if you can. Both are tripod-adaptable, and a fixed binocular shows noticeably fainter stars than one held by hand.
Neither listing claims it. Nikon sells a waterproof Action EX separately; this is the plain Action.
10x · 50 mm (1.97 in) · porro prisms · multilayer-coated · long eye relief
Nikon's Action 10x50: a rubber-armored porro binocular with multilayer-coated lenses, turn-and-slide eyecups, long eye relief for glasses and a tripod-ready body.
Best for: Sweeping the Milky Way and open clusters, on a tripod or from a reclining chair
≈ $130
10x · 50 mm (1.97 in) · porro prisms · multi-coated · TP-3 tripod adapter optional
A 10x50 porro binocular from Pentax's Jupiter series, with multi-coated optics, a rubber-coated body and an optional TP-3 tripod adapter.
Best for: A first serious binocular for the sky, with a tripod adapter available when the arms tire
≈ $99
Any figure written into the body of this page was true on the day it was written. The amount shown next to each instrument is requested from the retailer as the page loads, and it is that amount, not the text, that stands.
