Astromania · Eyepiece
Astromania Planetary 4mm
Sharpen your planetary views without sharpening your budget with this capable 4mm eyepiece
Price updated Apr 18, 2026
Performance Scores
Overview
The Astromania Planetary 4mm is a short focal length eyepiece built for observers who want to push magnification on planets and the Moon. Paired with a typical telescope, this eyepiece delivers high magnification views where surface detail matters most. Saturn's cloud bands, Jupiter's Great Red Spot, and lunar craters are where this eyepiece earns its place in your kit. The 58 degree apparent field of view is a practical choice at this focal length, giving you enough sky to track a planet as it drifts across the field without feeling cramped.
Eye relief of around 16mm is genuinely comfortable for extended observing sessions, including for those who wear glasses. Five lens elements in three groups, combined with fully multi-coated surfaces, help maintain contrast and reduce scatter, which matters considerably when you are trying to distinguish subtle planetary detail. At $49.99, this eyepiece sits in a competitive price bracket. The blackened lens edges and internally treated barrel are thoughtful touches that cut down on stray light, a real concern at high magnification.
It accepts standard 1.25 inch filters directly, which is useful for planetary work. Rated 4.5 out of 5 across over 200 reviews, it has a solid track record among amateur observers.
At a Glance
4mm
Focal Length
Specifications
Key Features
- 4mm focal length delivers high magnification, well suited for planetary and lunar observation
- 58 degree apparent field of view gives comfortable visual context even at high power
- 16mm eye relief works well for extended sessions and accommodates eyeglass wearers
- Fully multi-coated 5 element, 3 group optical design supports good contrast and low scatter
- Blackened lens edges and treated internal barrel reduce stray light at high magnification
- Standard 1.25 inch barrel accepts filters directly, adding flexibility for planetary work
- Priced under $50 with strong user ratings, offering reliable performance for the cost
Customer Reviews
214 reviews
I bought this EP on an advertised Clearance over inventory sale for $30 dollars and wow its a keeper, great quality and excellent performance even for its regular price of $60. Yes these are copies of the Original Tomas Black Planetary EP's and there is all kinds of scuttle but going around the inte...
i had no idea who Astromania was but the specs of the eyepiece made me curious. they looked very similar to the Celestion X-cels which ive owned before and really liked but half the cost. i wanted an eyepiece with a twist cup and larger field than standard so this seemed to be what i was looking for...
I'll start with the eyepiece for those who are interested in my thoughts on it. I reassembled the eyepiece after removing it from it's box (see photo) and waited for dark. Given I received an obviously returned item I don't know if it has any defects or not with regards to visuals. Viewing Saturn an...