Essential Astronomy Accessories 2026

The Moon through a telescope is bright. Painfully, squint-inducingly bright — especially through a 6" or 8" scope near full Moon. An ND 0.9 filter cuts the light by about 87%, bringing the glare down to a comfortable level and actually revealing more surface detail because your eye isn't being overwhelmed.

It screws onto the barrel of any standard 1.25" eyepiece. Put it on, point at the Moon, and suddenly you can see craters, mountain ranges, and rilles without feeling like you're staring at a car headlight. At £11, this is the most cost-effective accessory in astronomy — and almost certainly the first one you'll wish you'd bought sooner.

The Telrad is the single most popular finder upgrade in amateur astronomy, and it's been in production largely unchanged since the 1970s — because it works. It projects three concentric red circles (0.5°, 2°, and 4° diameter) onto a tilted glass screen. You look through it with both eyes open and see the circles overlaid on the real sky, making it trivially easy to point your telescope at the right patch of sky.

Most beginner telescopes come with a small optical finderscope or a basic red-dot finder. The Telrad is better than both because the circles give you a sense of scale — the 4° circle is roughly the width of your fist at arm's length, and many star atlases are designed with Telrad circles in mind. Star-hopping from a known star to a faint target becomes a matter of "move two Telrad circles east and one north."

It attaches to the telescope tube with an adhesive base (included) and runs on two AA batteries that last months. The brightness is adjustable — use the dimmest setting that's visible to preserve your night vision.

If you own a Newtonian reflector (Heritage 130P, Heritage 150P, Skyliner 200P, or similar), your mirrors need to be aligned — collimated — for the telescope to produce sharp images. Transport, temperature changes, and the odd bump can knock them slightly out of alignment. A miscollimated scope shows bloated, asymmetric stars and soft planetary detail.

The Rigel Aline is the simplest collimation tool: a plastic cap with a precisely centred peephole and crosshairs. You slot it into the focuser, look through the hole, and check whether the reflections of your primary mirror, secondary mirror, and the crosshairs are all concentric. If they're not, you adjust the mirror screws until they are. The whole process takes 2–3 minutes once you've done it a few times.

At £6, there is no reason not to own one. First Light Optics themselves say "every Newtonian owner should have one."

The fixed ND 0.9 Moon filter (#1 on this list) is perfectly good for most lunar observing. But a variable polarising filter gives you continuous control — rotate the two polarising layers against each other and you can dial the transmission from roughly 1% to 40%. This means you can match the filter to the Moon's phase: a thin crescent needs barely any filtering, while a near-full Moon wants heavy attenuation.

It also works on bright planets. Venus, in particular, benefits from some attenuation — it's so bright it can overwhelm detail in a telescope. Jupiter at opposition can also be slightly too bright in larger scopes.

The Astro Essentials version fits 1.25" eyepieces and has a knurled ring for easy adjustment in the dark. It's £13 more than the fixed filter but considerably more flexible.

The UK's maritime climate means one thing for Schmidt-Cassegrain owners: dew. On a typical clear night, moisture condenses on your corrector plate within 30 to 60 minutes. Once it fogs, observing is over unless you have a heater or a hairdryer.

This is the official Celestron dew shield, designed specifically for C6 (150mm) and C8 (200mm) OTA tubes — including the hugely popular NexStar 6SE. It's not a generic universal shield. It fits perfectly, stays secure, and extends beyond the corrector plate to create a protective zone that delays dew formation significantly.

The shield also acts as a light blocker, reducing stray light from streetlamps and neighbors' security lights — a bonus benefit that improves contrast on deep-sky targets and planets. For all-night observing, combine with a dew heater strip (£40–£60). Shield alone extends sessions by 2–3×. Shield + heater = problem solved.

The #23A is the essential Mars filter. It blocks blue and green wavelengths and transmits red and orange, which makes the reddish desert regions of Mars punch dramatically brighter while darkening the blue-grey polar hazes and sky features. Dark surface markings like Syrtis Major and Sinus Meridiani, which blend into an orange haze in unfiltered views, snap into clear contrast. If you observe Mars and have 100mm+ aperture, this is the most impactful £9 you can spend.

On Jupiter, it enhances contrast in the equatorial belts — the NEB and SEB become more distinct against the lighter zones. Less transformative than on Mars, but a worthwhile secondary use. At ~25% transmission it requires at least 100mm aperture; smaller telescopes will find the image too dim.

The #21 orange filter is the best all-round planetary filter for beginners — it enhances contrast on Mars, Jupiter, and Saturn without the aggressive light cut of a full red filter. At ~46% transmission it works from 80mm aperture upwards, which means it's suitable for virtually any telescope in this guide. Where the red filter is the Mars specialist, the orange is the Jupiter and "everything" choice — the equatorial belts become noticeably crisper, the Great Red Spot appears warmer and better defined, and Saturn's globe picks up some subtle band detail.

If you're buying your first colour filter and aren't sure where to start, this is it. It delivers a meaningful improvement on Jupiter (the most-observed planet in the UK sky) without darkening the image enough to cause problems on smaller scopes.

The #82A is the classic Venus filter and the recommended companion to the orange or red filters. At 73% transmission it barely dims the image at all — it just cools down the overpowering white glare of Venus, making the crescent or gibbous phase much more comfortable to observe and occasional cloud detail more accessible. Ask any experienced planetary observer for a Venus filter recommendation and the #82A is the near-universal answer.

On Mars it works the opposite way to the red filter — enhancing the bright polar ice caps and atmospheric hazes that the red filter suppresses. On Jupiter it makes the Great Red Spot marginally more distinct against the lighter Equatorial Zone. At 73% transmission, it works with any telescope from 60mm upwards.

If you're imaging planets and wondering why your captures don't look as sharp as the best images you've seen online, the answer is almost certainly atmospheric dispersion. Earth's atmosphere acts like a prism — it bends different wavelengths of light by different amounts, smearing red, green, and blue channel images into slightly different positions on your sensor. At UK latitudes, where Saturn never gets above 25° altitude and Jupiter peaks at around 40°, the effect is significant and will noticeably blur fine detail even on good seeing nights.

The ZWO ADC inserts between your telescope focuser and camera and corrects this by passing the light through two adjustable prisms that introduce equal and opposite dispersion. Once dialled in, colour fringing disappears and the image sharpens dramatically — particularly in the blue channel, where dispersion is strongest. This is an imaging-only accessory and the consensus best upgrade for UK planetary imagers.