Observing
The planets are the objects a city observer can see as well as anyone. They are bright, they are small, and what limits them is the steadiness of the atmosphere rather than the darkness of the sky — which changes what is worth buying for them.
Detail scales with aperture, and on planets that is exactly the currency. A larger tube resolves finer features on the same night — until the atmosphere becomes the limit, which it usually does.
A folded telescope at f/11 or f/14 gives high magnification with ordinary eyepieces and generally carries a smaller central obstruction, which helps contrast on low-contrast detail.
Detail appears in flashes as the air steadies. Ten minutes at the eyepiece shows considerably more than one minute, and no purchase substitutes for it.
They raise the contrast of features that differ in colour from their surroundings. The effect is genuine, modest, and more useful in a large aperture than a small one.
8-inch Schmidt-Cassegrain · computerised GoTo fork
An eight-inch Schmidt-Cassegrain on a single-arm computerised fork mount, with a 40 000-object database and the maker’s SkyAlign alignment routine.
Best for: An observer who wants serious aperture that still fits in a car boot
≈ $1499 / £1500 / €1537
2x Barlow · achromatic · fully coated · metal body
A 2x achromatic Barlow lens in a full metal body, fully coated, described in four words per bullet.
Best for: Doubling the range of an existing eyepiece set at minimum cost
≈ £17 / €18
Six 1.25 in colour filters · #21 and #25 named
A six-filter 1.25 in colour set for planetary observing, with the maker naming #21 orange and #25 red and describing what each brings out.
Best for: A planetary observer with a telescope large enough to spend the light
≈ £57 / €63
12 mm focal length · 60° apparent field · six elements
A six-element fully multi-coated eyepiece of 12 mm focal length with a 60-degree apparent field, a twist-up eyecup and a knurled rubber grip.
Best for: The eyepiece that stays on the planets, used with gloves on a cold night
≈ $93 / £88 / €106
4 MP sensor · 2 in display · clamps over eyepieces 38–73 mm
A Wi-Fi electronic eyepiece with its own two-inch screen and battery, clamping over eyepieces from 38 to 73 mm, recording 2K video to a card of up to 256 GB.
Best for: Screen-sharing a view in the field, with no laptop and no phone required
≈ €66
As much as the air allows, up to roughly twice the aperture in millimetres. On most nights the atmosphere stops it well short, and pushing past that point enlarges the blur rather than the detail.
Very little. A planet is thousands of times brighter than the sky glow, so the contrast that a city sky destroys is contrast the planets never depended on.
Because a camera records hundreds of frames and the best are kept. The atmosphere steadies for fractions of a second, and stacking captures those moments where the eye cannot hold them.
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.
Telescopes and mounts are discounted over and over through the year — hardest of all in the weeks before Christmas, which is exactly when most of them are bought — and a struck-through figure on its own says nothing whatever about what the same model was charged at four weeks ago. UniverTrack keeps a week-by-week record for each retailer, so a discount is measured against a figure somebody genuinely paid instead of one invented for the sale — and it says when the moment to buy has genuinely arrived.
