Care
A reflector whose mirrors are not aligned will not bring a star to a point at any magnification, and no eyepiece will fix it. Collimation is the adjustment that aligns them, and the tools divide cleanly by what question they answer.
Two mirrors and a focuser. The secondary has to sit centred under the focuser and point at the primary; the primary has to send the beam back up the axis. Both are adjusted with screws, usually three.
A laser collimator that is itself out of alignment in its barrel will confidently point the telescope wrong. Where a listing states that the collimator can be adjusted in its own housing, this site reports it — it is the difference between a tool that can be trusted and one that has to be checked.
After transport, after a collapsible tube is extended, and whenever a defocused star looks lopsided. A well-made Newtonian holds its alignment for weeks in a fixed setup and loses it in a car boot.
A soft image is blamed on collimation far more often than it deserves. A diffraction mask makes the point of focus unambiguous, and it costs less than any collimator on this shelf.
1.25 in laser · adjustable housing · 212 g
A 1.25 in laser collimator in an adjustable aluminium housing, with a roughened surface for reading the return beam, published at 212 g.
Best for: Collimating a Newtonian in the dark without a second person or a second tool
≈ £75 / €75
1.25 in with 2 in adapter · triplet lens · seven brightness levels
A metal collimator supplied with a 2 in adapter so it fits both focuser sizes, with a triplet lens and seven brightness settings.
Best for: An observer with both a 1.25 in and a 2 in focuser who wants one collimator for both
≈ £35 / €36
635–655 nm · under 5 mW · seven brightness levels · CR2032
A metal-bodied laser collimator with seven brightness steps, a published wavelength band and output figure, and three sealed adjustment ports for trueing the tool itself.
Best for: A Newtonian owner who wants a laser they can check and correct themselves
≈ $26 / £32
Tube outside diameter 175–220 mm · 2 mm acrylic · three-post mount
A laser-cut reinforced acrylic Bahtinov mask that clamps to tubes of 175 to 220 mm outside diameter with three silicone-sleeved metal posts.
Best for: Focusing an imaging session precisely, on a tube whose outside diameter has been measured
≈ $21 / £18 / €26
Metal body · four reticle patterns · hex-key adjustment
A metal red dot finder offering a dot, a circle with dot, a crosshair and a cross with circle, adjusted on both axes with a hex key.
Best for: Replacing the flimsy red dot finder supplied with a telescope
≈ £74 / €83
Defocus a bright star slightly at high magnification. The rings should be concentric; if the pattern is lopsided, the mirrors are out of alignment.
A sighting tube shows whether the secondary is centred under the focuser; a laser shows where the beam lands on the primary and returns. They answer different halves of the same question, which is why several observers own both.
No. It is a focusing aid: its diffraction pattern makes the exact point of focus visible. It is on this list because focus and collimation are the two things blamed for a soft image, and only one of them is adjusted with screws.
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.
