Getting started
Almost every disappointing first telescope fails for one of three reasons: it does not collect enough light, it will not hold still, or nothing else fits it. Magnification is not on that list, and it is the number most often printed on the box. These five are read against aperture, mount and eyepiece fitting, in that order.
Light-collecting area goes with the square of the aperture, so 130 mm gathers nearly twice what 90 mm does. It is the one specification that cannot be improved later, and it sets the ceiling on everything the instrument will ever show.
A tube that shakes for four seconds after every touch is unusable at high magnification, whatever its optics. This is why a tabletop Dobsonian on a solid table often outperforms a larger tube on a thin tripod — there is simply less to wobble.
A 1.25 in focuser opens the whole accessory catalogue: eyepieces, filters, diagonals, phone adapters. A non-standard fitting closes it. Of all three figures this is the cheapest to check and the most often overlooked.
Maximum magnification. It is a number any telescope can reach and almost none can use: beyond roughly twice the aperture in millimetres, the image grows without gaining detail. A listing that leads with it is describing a calculation, not an instrument.
130 mm parabolic mirror · 650 mm focal length
A 130/650 parabolic Newtonian on a wooden tabletop Dobsonian base, with a collapsible tube, a red dot finder and two eyepieces.
Best for: Somebody who wants a real 130 mm mirror that stores in a cupboard
≈ £264 / €273
70 mm aperture · 700 mm focal length
An achromatic 70/700 refractor on an alt-azimuth mount with an aluminium tripod, sold as a first adult instrument.
Best for: An adult or older teenager starting with the Moon and planets
≈ £94 / €90
130 mm parabolic mirror · 650 mm focal length
A 130/650 Newtonian with a parabolic primary on an EQ-320 mount, with a 1.25 in focuser, a tracking drive and an illuminated LED finder.
Best for: A first serious deep-sky instrument for somebody prepared to collimate it
≈ €409
76 mm aperture · 350 mm focal length
A 76/350 tabletop Dobsonian sold pre-assembled, with two eyepieces, a Barlow and a Moon filter.
Best for: A very compact first telescope for a child or a small flat
≈ £113 / €142
70 mm aperture · 400 mm focal length · from age 8
The BRESSER JUNIOR 70/400 in its backpack version, with three 24.5 mm eyepieces, a star diagonal, a 1.5x erecting lens, a tripod and a phone holder.
Best for: A child from about eight who will carry and set up the telescope without help
≈ £85 / €64
Enough to show the Moon’s craters, Jupiter’s moons and Saturn’s rings, which begins around 70 mm and improves steadily from there. What aperture cannot do is fix a shaking mount.
Because 1.25 in is the size almost every eyepiece, filter and diagonal uses. A telescope with a 24.5 mm fitting can only ever use what came in its box.
It has nothing to align and two axes that move the way a person looks around. The trade is that it does not track, so objects drift out of the field and have to be nudged back.
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.
