Explore Scientific 72° ED Series 6.5mm Waterproof Eyepiece

Product Overview

The Explore Scientific 72° ED Series 6.5mm is a short focal length waterproof eyepiece with a 1.25-inch barrel, built around extra-low-dispersion glass. At 6.5mm it is a high-magnification eyepiece: in a 988mm refractor it gives 152x, in a 1500mm Maksutov 231x.

The 72° apparent field sits between the 68° Series and the 82° Series — wide enough that an object at high power stays in view noticeably longer than it would in a 52° eyepiece, without the outer-field demands of a 100° design.

Who It's For

• Lunar and planetary observers: 6.5mm is a working high-power focal length in most apertures, and ED glass is aimed squarely at the colour and contrast that planetary detail depends on.
• Double-star observers needing magnification without a field so narrow that the pair drifts out between looks.
• Undriven and Dobsonian users: the wider apparent field buys drift time at high power on an unguided mount.
• Eyeglass wearers: Explore Scientific specifies generous eye relief for the series, which is the usual constraint at this focal length.

Key Features & Design

• Extra-low-dispersion (ED) glass: reduces chromatic aberration within the eyepiece itself, which shows as cleaner colour separation and higher contrast on planetary detail.
• 72° apparent field of view: more immersive than the 52° and 62° Series, and easier on the outer field than the 82° and 100° designs.
• 1.25″ barrel: fits any standard 1.25-inch focuser or diagonal directly.
• Waterproof construction, consistent with the sealed housings used across the Explore Scientific waterproof eyepiece range.
• Generous eye relief for the focal length, which keeps extended sessions comfortable and makes observing with glasses on practical.

Recommended Uses

• High-power lunar and planetary observing.
• Splitting double stars.
• Compact deep-sky targets — planetary nebulae and globular cluster cores.
• High-power observing on an undriven mount, where apparent field translates directly into time on target.

Compatibility and Accessory Notes

• Fits any 1.25-inch focuser or diagonal. In a 2-inch focuser it needs a 2-inch to 1.25-inch adapter.
• Magnification: telescope focal length ÷ 6.5. A 1200mm SCT gives 185x; a 750mm Newtonian gives 115x.
• Filters: takes standard 1.25-inch threaded filters.
• Within the series: the 72° ED Series runs 6.5mm, 8.5mm, 11.5mm, 15mm, 20mm, 25mm, 30mm and 40mm, so a matched set holds the same apparent field and eye position across focal lengths.

Good to Know Before You Order

• 6.5mm is a high-power eyepiece, and seeing governs it. On a steady night in a 6-inch or larger telescope it will show what the aperture can do; on a turbulent night a longer focal length will show more. That is atmosphere, not optics.
• Explore Scientific does not currently publish a full specification table for this series. Eye relief, field stop diameter, element count and weight are not given on their product page, so those rows are absent below rather than estimated. If you need a specific figure before ordering, ask us and we will put the question to our Explore Scientific rep.
• It is a visual eyepiece. Eyepiece-projection imaging is possible with an adapter, but the design target is the eye.

Frequently Asked Questions

Is it difficult to set up?

No — it drops into any 1.25-inch focuser or diagonal and is ready immediately. Nothing to assemble or adjust.

What magnification will I get?

Divide your telescope's focal length in millimetres by 6.5. A 1000mm telescope gives 154x.

What does the ED glass actually change?

Extra-low-dispersion glass brings wavelengths closer to a common focus inside the eyepiece, so colour edges on bright targets are cleaner and fine planetary contrast holds up better than in a standard-glass design of the same field.

How does it compare to the 82° Series at the same focal length?

The 82° gives a wider, more immersive field; the 72° ED is built around glass type and eye relief instead. Which one suits you depends on whether you value field width or comfort and colour correction more — tell us what you observe and we will give you a straight answer.

Can I use it with glasses on?

Explore Scientific specifies generous eye relief for this series, which is what makes that practical. They do not publish the figure in millimetres, so we are not going to quote one — if it is the deciding factor for you, ask and we will confirm it with our rep first.

Bottom Line

In short: a 6.5mm ED-glass eyepiece with a 72° field and a 1.25-inch barrel — high magnification with more field and more eye relief than a short-focal-length eyepiece usually offers. If you are filling out a focal-length set for a particular telescope, send us its aperture and focal length and we will map out which of the series make sense.