Takahashi TPL-25 Plossl Eyepiece

Product Overview

The TPL-25 is a 25 mm Plossl eyepiece from Takahashi's TPL series, the line that replaced the company's earlier Abbe and LE eyepieces. It gives a 48° apparent field with 18 mm of eye relief, from four elements in two groups — the classic Plossl configuration, built in high-refraction, low-dispersion glass that Takahashi states cuts center-field chromatic aberration to roughly half the level of the Abbe series.

At 25 mm it sits toward the lower-power, wider-true-field end of the TPL range — a comfortable eyepiece for framing a broader area of sky rather than pushing magnification.

Who It's For

This is a good match if you want a general-purpose, lower-power eyepiece for open clusters, star fields and wider lunar views, with a comfortable 18 mm of eye relief. The 48° field is the traditional Plossl width — narrower than a modern wide-field design, and correspondingly simpler and less expensive to produce well.

It is a visual eyepiece. Imaging trains connect a camera directly and do not use one.

Key Features & Design

• 25 mm focal length: lower power and a wider true field on most Takahashi telescopes — see Compatibility for real figures.
• 48° apparent field: the traditional Plossl field width, sharp across the center with mild softening toward the edge.
• 18 mm eye relief: comfortable eye position, including for many glasses wearers.
• 4 elements in 2 groups: the symmetric Plossl configuration.
• High-refraction, low-dispersion glass: tightens center-field chromatic correction relative to Takahashi's earlier Abbe and LE eyepieces.
• Multi-coated optics: 99% visible-light transmission with a matte barrel finish to control stray light.

Optical Design

The Plossl design pairs two achromatic doublets symmetrically around the field stop — four elements in two groups, one of the longest-serving eyepiece formulas in production because it delivers a sharp, high-contrast image at reasonable cost. Takahashi's TPL series builds it in higher-refraction, lower-dispersion glass than the company's earlier Abbe and LE lines, which measurably tightens chromatic correction at the center of the field.

Takahashi describes the TPL series as sharp from the center out to roughly the halfway point of the 48° field, with mild star distortion toward the corners — typical of the Plossl form at this field width. Takahashi states that pairing the series with the 2x Ortho Barlow clearly improves flatfieldness, with the combination approaching full-field correction.

Recommended Uses

• Open clusters and star fields at low-to-moderate power with a wide true field for the focal length.
• Lunar observing where a fuller view of the disc is wanted rather than crater-level detail.
• Double star sweeping and general low-power visual observing.
• A comfortable eyepiece for extended sessions, given the 18 mm eye relief.
• Paired with the 2x Ortho Barlow for a flatter field at roughly double the power.

Compatibility and Accessory Notes

• Magnification: divide your telescope's focal length by 25. An FS-60CB at 355 mm gives about 14x; an FC-100DZ at 800 mm gives about 32x; a Mewlon 210 at 2415 mm gives about 97x.
• Barrel: 31.7 mm — a standard 1.25-inch fit for Takahashi and most third-party diagonals and focusers.
• Diagonal: in a refractor you will normally use it behind a star diagonal. The Takahashi 1.25-inch prism diagonal is a direct pairing.
• 2x Ortho Barlow: Takahashi publishes that flatfieldness across the TPL series clearly improves when used through the 2x Ortho Barlow, at roughly double this eyepiece's magnification.
• Back focus: for adapter and spacing questions across your imaging or visual train, see the Takahashi Back Focus Guide.

Good to Know Before You Order

• 48° is a traditional field, not an ultra-wide one. An 82° or 100° eyepiece gives a more immersive view; the TPL trades that width for a simpler design that still delivers a sharp center field.
• Magnification depends on your telescope. The same 25 mm gives about 14x on a short 60 mm refractor and 97x on a Mewlon 210 — send us your telescope model and we will confirm where it lands in your eyepiece set.
• It is a visual eyepiece. Camera trains connect directly to the telescope or its corrector.
• 140 g is light — it will not register in most focuser-balance calculations.

Frequently Asked Questions

Is it difficult to set up?

No — it drops into a 1.25-inch diagonal or focuser and you focus. Nothing to assemble or adjust.

What magnification will I get?

Your telescope's focal length divided by 25. Send us your telescope model and we will work out where it fits alongside the eyepieces you already own.

How does it compare to Takahashi's older Abbe and LE eyepieces?

The TPL series uses higher-refraction, lower-dispersion glass, cutting center-field chromatic aberration to roughly half the Abbe level and about two-thirds of the LE level.

Is it good for deep-sky observing?

Yes — at 25 mm it gives one of the wider true fields in the TPL range, well suited to open clusters and star fields rather than high-power planetary detail.

Can I use it with glasses?

18 mm of eye relief is comfortable for most glasses wearers.

Will it work with a Barlow?

Yes — the 2x Ortho Barlow doubles the magnification and, per Takahashi, improves the TPL series' flatfieldness at the same time.

Is it parfocal with other Takahashi eyepieces?

You'll need to refocus when switching between eyepiece families.

Bottom Line

In short: a 25 mm Plossl eyepiece with a 48° field and 18 mm of eye relief, built from four elements in two groups with glass chosen to keep the center field free of chromatic aberration. It suits low-power cluster and star-field viewing, and flattens out further when paired with Takahashi's 2x Ortho Barlow.