Celestron FirstScope (21024): A Simple Tabletop Telescope for First-Time Stargazers

The Celestron FirstScope, model 21024, is a small tabletop telescope designed to be about as simple as a telescope can be. This page combines two earlier posts on this site about the same model into one guide with the specifications checked against Celestron’s listing.

A telescope with a story

The FirstScope was named an official product of the International Year of Astronomy 2009, a worldwide celebration organised by the International Astronomical Union and UNESCO to mark 400 years since Galileo first turned a telescope to the sky in 1609. As a tribute, the tube is printed with the names of famous astronomers and scientists. Later versions have come in special designs, including a Moon-themed edition.

What it is

The FirstScope is a Newtonian reflector: a curved mirror at the bottom of the tube gathers light and a small flat mirror sends it to the eyepiece near the top. It sits on a small Dobsonian-style base, a simple swivel mount you push in the direction you want to look. There are no gears, slow-motion controls or setup steps: put it on a stable table, point it and focus.

Verified specifications

From Celestron’s product page and spec sheet:

• Optical design: Newtonian reflector with spherical primary mirror
• Aperture: 76 mm (3 in)
• Focal length: 300 mm; focal ratio f/3.95
• Eyepieces: 20 mm (15x) and 4 mm (75x)
• Highest/lowest useful magnification: 180x / 11x
• Limiting stellar magnitude: about 11.9
• Light-gathering power: about 118 times the human eye
• Total kit weight: about 1.95 kg (4.3 lb)
• Mount: manual tabletop Dobsonian

The basic kit does not include a finderscope, Barlow or diagonal. Celestron sells a separate FirstScope Accessory Kit that adds a 5×24 finderscope, a Moon filter and two extra eyepieces giving 24x and 50x, so check what’s in the box.

What you can see

Expect bright, wide views of:

• The Moon: craters, mountain ranges and dark plains even at 15x. This is the FirstScope’s showpiece.
• Jupiter’s four largest moons as points of light beside the planet.
• Saturn’s rings as a small but recognisable shape at 75x on a steady night.
• Venus’s phases.
• Star clusters such as the Pleiades, the Beehive in Cancer and the Double Cluster in Perseus, which fit nicely in the wide field.
• The Orion Nebula and Andromeda Galaxy as faint glows from a dark site.

The 4 mm eyepiece gives 75x, but because it is a very short focal length, it can be hard to look through and shows a dim, small image. A mid-range eyepiece, such as the 50x eyepiece in Celestron’s accessory kit, is often more comfortable for planets.

Tips for better views

• Use a sturdy surface. A garden table, a low wall or an upturned crate at a comfortable height works better than holding it on your lap.
• Aim by sighting along the tube. Without a finder, line up the tube with your target, then start with the 20 mm eyepiece to find it. Some owners add an inexpensive red-dot finder.
• Give it time to cool. Place it outside 15 to 20 minutes before observing.
• Check collimation. Fast (low focal ratio) reflectors are sensitive to mirror alignment. If images look blurry even when focused, consult Celestron’s manual.
• Observe the Moon when it’s not full. Craters look most dramatic near the terminator, the line between day and night, during crescent and quarter phases.

Looking after it

The FirstScope’s open tube means dust can settle on the mirror over time. Store it with the dust cap on, somewhere dry, and avoid touching the mirror. A little dust has almost no effect on the view, so resist the urge to clean it often. If cleaning is ever needed, follow Celestron’s instructions rather than wiping the mirror with a cloth, which can scratch the coating. Bring the telescope indoors in its cap after a dewy night and let it dry naturally before packing it away.

Who it suits

The FirstScope suits young children (with adult supervision), families and anyone who wants a no-fuss introduction to the night sky. It’s also handy as a grab-and-go scope or a gift. If you want more detail on planets or faint deep-sky objects, a larger reflector or a refractor on a tripod will show more, but the FirstScope is a fun, unintimidating way to begin.

Safety note

Never point the telescope at the Sun. Supervise children when it is outside during daylight hours.