Accessories
Most telescopes arrive with one or two eyepieces of uneven quality. Three well-chosen eyepieces, a low, a medium and a high power, cover nearly everything. Work out the magnifications in your own telescope before buying, and cross out any that repeat.
The longest focal length, 20 to 25 mm, gives the widest view and is used every evening to find and center. A wide apparent field helps: SVBONY’s 20 mm 66° shows 1.7 times the sky of a Plössl and publishes 16 mm of eye relief.
The one that stays in the focuser most of the night, around 10 to 12 mm. Celestron’s X-Cel LX 12 mm gives 60 degrees, six elements and 16 mm of eye relief.
The shortest, used when the air is steady: about 6 mm on a 650 to 900 mm telescope. The Omni 6 mm is an inexpensive Plössl; its eye relief is short.
A 2x Barlow doubles every eyepiece you own and keeps their eye relief. A 12 mm in a Barlow gives the power of a 6 mm, more comfortably. Check that it does not duplicate an eyepiece you already have.
An 8 to 24 mm zoom such as Alstar’s, with 40 to 60 degrees and 15 to 18 mm of eye relief, covers the medium and high range in one barrel.
List the magnifications each eyepiece gives in your telescope, Barlow included, and cross out the repeats.
The longest stated focal length: it gives the widest field and locates the target.
The one that stays fitted most of the evening, between the two extremes.
The shortest stated focal length, usable only when the sky allows.
| The role | Stated focal length | When it serves |
|---|---|---|
| Finding | The longest | Every evening |
| Observing | Intermediate | Most of the time |
| Detail | The shortest | Only on good nights |
| Duplicating | Too close together | Never |
Eyepieces mostly suffer from the eyelash that touches the lens and from the dust that settles in an open box. Their glass is small, so every clumsy wipe counts for more than on a tube.
This site publishes stated specifications and validates no accessory for the Sun.
20 mm (0.79 in) · 66° apparent field · 16 mm (0.63 in) eye relief · fully multi-coated · edge-blackened
SVBONY's 20 mm 66-degree eyepiece: a multi-group, fully multi-coated wide-angle with edge-blackened optics and 16 mm of eye relief that lets eyeglass wearers see the whole field.
Best for: The low-power eyepiece that stays in the focuser: wide, long-relief, usable with glasses
≈ $37
12 mm (0.47 in) · 60° apparent field · six elements · 16 mm eye relief · fully multi-coated
Celestron's X-Cel LX 12 mm: a six-element, fully multi-coated eyepiece with a 60-degree field, 16 mm of eye relief, blackened lens edges, a twist-up eyecup and a treaded rubber grip.
Best for: The eyepiece that stays on the planets, used with glasses or gloves on a cold night
≈ $93
6 mm (0.24 in) Plössl · 50° apparent field · four elements · blackened lens edges · anodized aluminum
Celestron's Omni 6 mm: a four-element Plössl with a 50-degree field, multi-layer coatings, blackened lens edges, an anodized aluminum barrel with a filter thread and a fold-down rubber eyecup.
Best for: Planetary detail on a medium-focal-length telescope, from a maker with a US warranty
≈ $32
2x Barlow · 1.25 in · fully multi-coated with blackened edges · keeps eye relief · 2-year US warranty
Celestron's Omni 2x: a 1.25-inch Barlow with fully multi-coated optics and blackened lens edges, which doubles each eyepiece's power while keeping its eye relief.
Best for: A first Barlow for an existing 1.25-inch eyepiece set
≈ $35
8–24 mm stepless zoom · 40° to 60° apparent field · 15–18 mm eye relief · 7 elements in 4 groups · all-metal · 1.25 in
Alstar's 8-24 mm stepless zoom: a 7-element, 4-group multi-coated eyepiece with a 40 to 60-degree field, 15 to 18 mm of eye relief, blackened lens edges, a foldable eyecup, an all-metal body and a 1.25-inch filter thread.
Best for: An eyeglass wearer who wants one eyepiece instead of four, with eye relief published at every setting
≈ $66
Divide the telescope's focal length by the eyepiece's. A 650 mm telescope with a 20 mm eyepiece gives 33x; with a 6 mm, 108x.
It can replace two or three fixed eyepieces. The field narrows at the long end, but a good zoom with 15 to 18 mm of eye relief is comfortable everywhere.
Look for about 16 mm of eye relief. Short Plössls have very little; wide-angle designs like the X-Cel LX or SVBONY 66° publish 16 mm.
For observing: The low-power eyepiece that stays in the focuser: wide, long-relief, usable with glasses
Where it is strong: 66° field and 16 mm eye relief, both published
Where it is weak: Element count not published
For observing: The eyepiece that stays on the planets, used with glasses or gloves on a cold night
Where it is strong: 16 mm of eye relief at 12 mm focal length: comfortable with glasses
Where it is weak: About three times the price of a 12 mm Plössl
For observing: Planetary detail on a medium-focal-length telescope, from a maker with a US warranty
Where it is strong: Blackened lens edges and multi-layer coatings, stated
Where it is weak: Short eye relief, as with any 6 mm Plössl
For observing: A first Barlow for an existing 1.25-inch eyepiece set
Where it is strong: Fully multi-coated with blackened lens edges, at $35
Where it is weak: Element count not published
For observing: An eyeglass wearer who wants one eyepiece instead of four, with eye relief published at every setting
Where it is strong: Field, eye relief and optical layout all published
Where it is weak: 40° at the long end is narrow
$16 – $24
6 models
$24 – $66
7 models
$90 – $396
6 models
Model against model, where the comparison is already published.
The models above are taken from the catalog of this site. Specifications are the ones the maker publishes and the ones on the Amazon page; prices are the Keepa reading for the date shown, and both change. Ranking uses declared specifications, the weight of stated strengths against stated limits, and price. Nothing here has been pointed at the sky by us, and the page makes no such claim.
Last checked on
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.
