Refractors bend light through lenses, reflectors bounce it off mirrors, and catadioptrics combine both to fold a long light path into a short tube. Every design does the same job: gather starlight and bring it to a focus, where an eyepiece magnifies the image for your eye. Watch the gold photons below to follow the light.
Light passes through a large front objective lens that bends (refracts) it to a focus near the back of the tube; the eyepiece then magnifies that image. Sealed tube, no central obstruction → crisp, high-contrast views of the Moon, planets and double stars. Drawback: big lenses are heavy and costly, so apertures stay modest.
At Woodlands Galaxy: the rooftop Takahashi Sky 90 — a 90 mm f/5.6 fluorite apochromatic refractor for wide-field public views and astrophotography.
Light travels down the open tube to a concave primary mirror, reflects back up the tube and is turned 90° by a small flat secondary mirror out to an eyepiece on the side. Mirrors are cheap per centimetre of aperture — the best light-gathering for the money. Often carried on a simple Dobsonian mount. Needs occasional mirror alignment (collimation).
At Woodlands Galaxy: the observatory's main instrument is a 30 cm (12") reflector in the level-6 dome — a mirror telescope of this family (exact sub-design to confirm on site).
Light bounces off a concave primary, forward to a small convex secondary that stretches the focal length and sends it back through a hole in the primary to an eyepiece behind the tube. The folded path packs a very long focal length (= high magnification) into a manageable tube — ideal for planets, the lunar terminator and tight double stars.
Shown for reference. The Andromeda dome's 30 cm reflector may use a folded two-mirror design like this — its exact optics aren't publicly documented, so confirm on site.
A Cassegrain with a thin Schmidt corrector plate sealing the front: the lens fixes the mirror's edge distortion (spherical aberration), giving sharp stars across the field in a stubby, sealed, travel-friendly tube. The workhorse of public astronomy — long focal length, compact body, easy to motorise for GoTo tracking.
Shown for reference — Schmidt-Cassegrains are common at public observatories, but aren't part of Woodlands Galaxy's confirmed fleet (30 cm dome reflector + Takahashi Sky 90 refractors).
The SCT's cousin: a thick, deeply curved meniscus lens corrects the mirror, and the secondary is usually just an aluminised spot on the corrector's inner surface — nothing to align, ever. Very long focal ratios (f/12–f/15) give razor-sharp, high-contrast Moon and planet views in a tiny sealed tube. Trade-offs: the thick glass takes a while to cool to night air, and large apertures get heavy, so most Maks are 90–180 mm (the classic Sky-Watcher/Celestron "Mak" spotting and planetary scopes).
Shown for reference — a compact Maksutov makes an ideal grab-and-go planetary scope, though it isn't part of Woodlands Galaxy's confirmed fleet.
Earth spins at 15° per hour, so every object drifts westward; at 200× it crosses the eyepiece in under a minute. A mount's job is to point the telescope and keep it pointed. There are two families: alt-azimuth mounts move up-down and left-right like a camera tripod, while equatorial mounts have one axis tilted parallel to Earth's axis so a single slow motor cancels the spin. Singapore twist: at latitude 1.3°N the celestial pole sits right on the northern horizon, so equatorial mounts here are tilted almost flat.
The computer slews to any of 40 000 objects, then drives both axes at constantly changing rates to hold it centred. Fast setup, no polar alignment, ideal for public queues. Weakness: the field slowly rotates in the eyepiece, so long-exposure DSO photos need an equatorial wedge or derotator.
Common at public observatories for fast, queue-friendly GoTo. Whether the Andromeda dome uses a computerised mount of this type isn't publicly documented — confirm on site.
Alt-azimuth at its simplest: a plywood rocker box on a swivel base. No motors — you nudge the tube by hand every ~30 seconds at high power as the sky drifts past. What it gives up in tracking it repays in aperture: the cheapest way to carry a big Newtonian, and newcomers learn the sky fastest on one.
Shown for reference — simple, big-aperture manual scopes; not part of Woodlands Galaxy's confirmed fleet.
The polar axis is tilted to run parallel to Earth's axis; one motor turning at sidereal rate (15°/hr) exactly cancels Earth's spin, so the object and the field orientation stay locked — which is why every serious DSO-imaging rig sits on one. A counterweight balances the scope, and the mount must "meridian flip" as targets cross due south.
Usage: deep-sky astrophotography; the design behind most hobbyist imaging setups.
A rectangular yoke rides on a polar axis carried by two massive piers, with the telescope swinging on pivots inside the frame. Same one-motor sidereal tracking as a GEM but with no counterweights and rock-solid stability — the classic way to mount a big observatory reflector. Its one blind spot, the celestial pole itself, doesn't matter in Singapore where the pole hugs the horizon.
Shown for reference — the English yoke is a classic mount for a domed observatory telescope. The Andromeda dome's mount type isn't publicly documented; confirm on site.
Both mount types can keep a deep-sky object centred: the equatorial does it with one axis turning smoothly at sidereal rate, while an alt-az GoTo computer recalculates altitude and azimuth every second. The difference shows up in the camera: on an alt-az mount the field slowly rotates around the target, smearing stars in long exposures. That's why long-exposure imaging favours an equatorial mount (or a field de-rotator), while alt-az GoTo scopes are ideal for visual queues — for which field rotation is invisible.
| Common eyepiece | Magnification |
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Rule of thumb: beyond ~2× the aperture in millimetres the image just gets bigger and blurrier — Singapore's steamy seeing often caps sharp views around 150–250× even on the 30 cm reflector. An exit pupil above ~7 mm wastes light (wider than a dark-adapted pupil).