Editorial Policy

Updated 17 October 2026. A 25 mm eyepiece in a 1200 mm telescope is 48x on every page that uses that pair.

If a draft and the formula disagree, the formula stays. The sentence changes.

Magnification is telescope focal length divided by eyepiece focal length. A 2x Barlow turns 48x into 96x.

The useful ceiling is about 50 times the aperture in inches. An 8 in mirror is 203 mm, so the line is 400x.

Exit pupil is aperture in mm divided by magnification. At 48x that 203 mm mirror gives about 4.2 mm.

Under 0.5 mm the view goes dim. Over 7 mm the beam overfills a 7 mm pupil.

Minimum useful power is aperture in mm divided by 7. On 203 mm that floor is 29x.

True field is apparent field divided by magnification. A 52 degree eyepiece at 48x covers about 1.1 degrees. The Moon is about 0.5 degrees across.

Dawes limit is 116 divided by aperture in mm. For 203 mm the figure is about 0.57 arcseconds.

Each formula is also in the HTML, so a dead script still shows the worked line. Sources sit on How we research.

Model rows come from the maker's own spec page. Copy the date. Aperture, focal length, focal ratio, weight, and focuser size are copied from it.

A 10 mm eyepiece in a 700 mm tube gives 70x. On a 70 mm lens the ceiling is about 140x, and 70x stays under it.

We draft with AI assistance. An editor then checks every number before the page goes live.

The check has two doors. A calculated figure must match the formula. A model figure must match the spec page, on the date we opened it.

A number with no formula and no spec page comes out. Units stay fixed. Aperture is 203 mm (8 in). Focal length stays in mm.

Found a figure that fights its source? Email [email protected] with the page URL and the line.

You can audit a line in one step. Divide 1200 by 25. You should get 48. If your sheet says 1300 mm, divide 1300 by 25 and expect 52.

We aim to reply within 14 days. A confirmed error is replaced, and the updated date on the page moves with it.

The correction note keeps three items: the old figure, the new figure, and the source. A 96x that should have been 48x is recorded as that pair.

Gear is grouped by a measured spec. Aperture, focal length, focal ratio, weight, and focuser size are the keys.

A 1.25 in eyepiece and a 2 in eyepiece do not share a row. A 2 in eyepiece needs a 2 in focuser. An adapter only goes the other way: a 1.25 in eyepiece in a 2 in focuser.

A page does not print a price. It does not print a star rating. It does not crown a single winner for every reader.

You match the row to the job. A 1200 mm tube and a 10 mm eyepiece are 120x. That is the fact the row has to carry.

Weight is a spec, in pounds or kilograms. The page copies the maker's figure for that model.

How those rows meet Amazon links is on the affiliate disclosure. The spec line does not change when a link is present.

A sky photo is a public-domain file, or it is an SVG drawn for the page. We do not invent a view and call it the telescope.

A drawn field carries the visible label Simulated view. You can read that label on the figure.

A public-domain file keeps its credit in the caption. A lunar frame from Apollo 11 is 1969, credited to NASA, public domain.

A Saturn frame from Voyager 2 uses the 1981 flyby, credited to NASA/JPL, public domain.

That credit is a source line. It sits in its own block. Product links stay in other blocks, so the credit is not asked to bless a product.

Alt text describes the picture. The number lives in the SVG or the table, where you can read it as a figure.