Monocular listings are unusually full of meaningless specification claims - 40x zoom, night vision, military grade. Five checks cut through all of it, and the first one does most of the work.
Check 1: compute the exit pupil
Objective divided by magnification. This single calculation tells you whether the monocular is a daylight tool or something you can use at legal light.
- Under 3 mm (a 10x25 at 2.5 mm, a 12x25 at 2.08 mm): daylight only. Fine if that is what you want.
- 3 to 4 mm (an 8x25 at 3.13 mm): daylight and bright overcast.
- Above 4 mm (an 8x36 at 4.5 mm, a 10x42 at 4.2 mm): usable near legal light.
If you intend to use it at dawn or dusk and the arithmetic gives you under 4 mm, stop - you have your answer and the rest of the comparison does not matter. Why exit pupil works this way.
Check 2: published eye relief
More important on a monocular than a binocular, because you tend to use one quickly and from awkward positions - braced on a tree, one-handed, leaning. Generous eye relief means you get the full field without precise positioning.
Vortex publishes 18.0 mm for the Solo R/T 8x36 and 14.5 mm for the Solo 10x25 (both verified 2026-10-05). That is a meaningful difference in how forgiving the two are in practice.
Check 3: is the magnification claim real
Ignore anything advertising a zoom range, and ignore anything above about 12x. A monocular claiming 10-30x zoom at $40 is not an optical instrument. High magnification in a small body means a tiny exit pupil and an image you cannot hold still - a 20x40 monocular computes to 2.0 mm of exit pupil and is unusable handheld.
The useful range for a hunting monocular is 8x to 10x. Above that you need support, and if you are carrying support you should be carrying a better optic.
Check 4: sealing and build
- Nitrogen or argon purged and O-ring sealed. Without it, internal fogging is a matter of when. This is cheap and near-universal on anything worth buying.
- A real warranty. Vortex VIP is unconditional and transferable even on a $79 monocular, which is genuinely unusual at that price.
- Rubber armor. A monocular lives loose in a pocket and gets knocked around more than a cased binocular does.
Check 5: what are you actually buying it for
This is the honest check and it saves people money. Three good answers and one bad one:
| Why you want one | What to buy | Note |
|---|---|---|
| A pocket backup | A 10x25 at about $79 | Accept that it is a daylight tool |
| Quick one-handed checks from a stand | An 8x36 at about $149 | 4.5 mm exit pupil and long eye relief |
| Finding animals in the dark | A thermal unit, 256 or 320 sensor | Check your state laws first |
| To replace binoculars and save money | Binoculars | This is the mistake. Why |
Three monoculars against the five checks
Price as of October 5, 2026. #ad How we earn
Vortex Solo R/T 8x36
A 4.5 mm exit pupil, 18 mm of eye relief and an MRAD ranging reticle in a unit that weighs a third of a binocular.
| Magnification | 8x |
|---|---|
| Objective lens | 36 mm |
| Eye relief | 18.0mm |
| Field of view | 393' @ 1000 yds |
| Angular field of view | 7.5º |
| Close focus | 16.4' |
| Weight | 9.7 oz. |
| Length | 4.9" |
| Exit pupil (computed) | 4.5 mm |
| Twilight factor (computed) | 17 |
Specs verified 2026-10-05 from Vortex's published specification. Exit pupil and twilight factor are computed, not quoted.
What it does well
- R/T ranging reticle estimates distance without batteries
- 18.0 mm eye relief, verified in Vortex's published specs
- Half the bulk of binoculars
Where it gives ground
- One eye tires faster than two over a long sit
- No depth perception, which matters in cover
Skip it if
You glass for more than a few minutes at a time.
How this score breaks down
- Low-light performance (weight 4)7.5
- Size and weight (weight 4)8.5
- Optical quality per dollar (weight 4)9.0
- Eye relief (weight 2)9.5
- Build and sealing (weight 2)9.0
Weights and definitions are published on how we review. These are editorial judgments from published specs and documented consensus, not test results.
The only unit in our picks that clears the exit pupil filter and has generous published eye relief.
Price as of October 5, 2026. #ad How we earn
Bushnell Legend 10x42 Monocular
A 42 mm objective gives a 4.2 mm exit pupil, which is the only way a monocular stays usable at legal light.
| Magnification | 10x |
|---|---|
| Objective lens | 42 mm |
| Exit pupil (computed) | 4.2 mm |
| Twilight factor (computed) | 20.5 |
Magnification and objective are the manufacturer's own model designation; exit pupil and twilight factor are computed from them. We could not machine-read Bushnell's spec page, so the remaining published figures are not listed rather than guessed.
What it does well
- 4.2 mm exit pupil matches a 10x42 binocular
- ED Prime glass
- Still far smaller than binoculars
Where it gives ground
- Bulky for a monocular - most of a binocular's volume
- One-eyed viewing at 10x is tiring
Skip it if
Size is the reason you want a monocular at all.
How this score breaks down
- Low-light performance (weight 4)8.5
- Size and weight (weight 4)6.0
- Optical quality per dollar (weight 4)8.5
- Eye relief (weight 2)7.0
- Build and sealing (weight 2)8.0
Weights and definitions are published on how we review. These are editorial judgments from published specs and documented consensus, not test results.
A reminder that the two things you want from a monocular - light and compactness - pull against each other.
Price as of October 5, 2026. #ad How we earn
Vortex Solo 10x25
A 2.5 mm exit pupil says this is a daylight optic, and at $79 and a few ounces that is exactly the job it is for.
| Magnification | 10x |
|---|---|
| Objective lens | 25 mm |
| Eye relief | 14.5mm |
| Field of view | 315' @ 1000 yds |
| Angular field of view | 6.0º |
| Close focus | 16.4' |
| Weight | 5.6 oz. |
| Length | 4.4" |
| Exit pupil (computed) | 2.5 mm |
| Twilight factor (computed) | 15.8 |
Specs verified 2026-10-05 from Vortex's published specification. Exit pupil and twilight factor are computed, not quoted.
What it does well
- Small enough to live in a bino harness pocket
- 10x in a unit you forget you are carrying
- VIP warranty
Where it gives ground
- 2.5 mm exit pupil is dim at dawn and dusk
- Narrow field makes scanning slow
Skip it if
This would be your only optic. Buy binoculars.
How this score breaks down
- Low-light performance (weight 4)5.0
- Size and weight (weight 4)9.5
- Optical quality per dollar (weight 4)9.0
- Eye relief (weight 2)7.0
- Build and sealing (weight 2)9.0
Weights and definitions are published on how we review. These are editorial judgments from published specs and documented consensus, not test results.
Fails the low-light check and is still a good purchase if you know what you are buying.
Questions people actually ask
What should I look for in a hunting monocular?
Are zoom monoculars any good?
What magnification monocular is best for hunting?
Is a $79 monocular worth buying?
Sources
- Vortex Solo R/T 8x36 published specifications - read 2026-10-05
- Vortex Solo 10x25 published specifications - read 2026-10-05