Celestron Inspire 100AZ vs AstroMaster 70AZ: Which Beginner Refractor Wins?

Quick Verdict

Spec Comparison

Optical Performance

How 100mm vs 70mm Aperture Affects What You See

The single biggest difference between these two telescopes is aperture. The Inspire 100AZ gathers 77 cm² of light — exactly double the 38 cm² of the AstroMaster 70AZ. In practical terms, this means:

• Lunar views: The Inspire shows finer crater detail and can handle higher magnification before the image breaks down. The AstroMaster shows the same craters but with less contrast at equivalent power.
• Planetary views: Jupiter's bands are more distinct in the Inspire. Saturn's rings show a cleaner separation. The AstroMaster is adequate but the image is noticeably dimmer at the same magnification.
• Chromatic aberration: Both are achromatic refractors and show purple fringing around bright objects. The Inspire's f/6.6 focal ratio shows slightly more false color than the AstroMaster's f/10 — a trade-off for the faster optics. A minus-violet filter helps both.
• Star test: Both show good factory collimation. The Inspire's larger 100mm objective naturally resolves fainter stars and splits tighter double stars than the 70mm.

The Inspire's optical advantage is real and visible. On the Moon at 100×, the Inspire reveals small craterlets and rilles that are ambiguous or invisible in the 70mm AstroMaster. On Jupiter, the difference is more subtle — both show the two main belts, but the Inspire also hints at the third belt on steady nights.

Mount and Build Quality

Both telescopes use similar alt-azimuth mounts with the same fundamental limitation: no slow-motion controls. This makes high-power observing fiddly, especially at 150× and above, where the slightest touch sends the image bouncing for 2–3 seconds.

The Inspire's mount is slightly heavier to support the larger optical tube, but the tripod legs are similar thin-gauge steel on both. Neither mount is adequate for serious high-power work without modification. A 5-pound sandbag on the accessory tray helps both significantly.

Build quality: The Inspire has a slightly better finish — the tube is glossy blue vs the AstroMaster's matte black. The Inspire's focuser is smoother and the dew shield slides forward for extra protection. Both use plastic rack-and-pinion focusers that work adequately at low-to-mid power but show some image shift at high magnification.

For detailed build analysis, see our Inspire 100AZ review and AstroMaster 70AZ review.

Moon Views Compared

The Moon is where both telescopes perform best, but the Inspire has a clear edge.

AstroMaster 70AZ at 70×: Copernicus is visible as a bright crater with a hint of terracing. The Apennine Mountains show as a bright ridge along the terminator. Plato is a smooth dark oval. The view is sharp and satisfying — enough to keep a beginner engaged for an entire evening.

Inspire 100AZ at 66×: Copernicus shows clear terraced walls. The Apennine Mountains resolve into individual peaks. Plato's floor reveals three tiny craterlets (a test of aperture and seeing). The Straight Wall is a thin but distinct dark line. The overall image is brighter and holds magnification better — at 130× (with the 2× Barlow), the Inspire reveals rilles and small craters that the AstroMaster cannot show at any power.

Verdict: The Inspire shows approximately 2× more lunar detail. The AstroMaster is still very good for its price — the Moon is the one target where a 70mm scope genuinely delivers.

Planet Views Compared

Jupiter (at 100×): Both telescopes show the two main equatorial belts. The Inspire shows them with more contrast and hints of the third belt (North Temperate Belt) on good nights. The Great Red Spot is a pale notch in both — detectable but not vivid. The four Galilean moons are easy in both.

Saturn (at 100×): Rings are clearly separated from the planet in both telescopes. The Inspire shows a slightly brighter image and cleaner ring separation. The Cassini Division is not visible in either — you need 114mm+ aperture for that. Titan is easy in both.

Mars (at opposition): Both show a small orange disk. The polar ice cap is detectable as a bright white patch in the Inspire; it is more subtle in the AstroMaster. Dark surface features are at the limit of visibility in the Inspire and generally not seen in the 70mm.

Verdict: The Inspire is noticeably better on planets, particularly on Jupiter where the extra aperture reveals fainter belt detail. The AstroMaster is adequate — it shows all the major features but with less contrast and at lower useful magnification.

Deep-Sky Performance

Neither telescope is optimized for deep-sky observing — their alt-az mounts and moderately long focal ratios make them planetary instruments first. But the Inspire's 2× light gathering advantage is noticeable on bright deep-sky targets.

• Orion Nebula (M42): Both show a faint gray-green patch. The Inspire shows more extension of the nebula wings and resolves the Trapezium stars more cleanly.
• Andromeda Galaxy (M31): Visible as an oval glow in both. The Inspire shows a brighter core and slightly more extension along the major axis.
• Globular clusters (M13): Both resolve outer stars. The Inspire resolves more stars and shows a brighter core.
• Ring Nebula (M57): Visible in both as a tiny donut at high power. The Inspire shows it slightly brighter.

Verdict: The Inspire is better on deep-sky, but neither replaces a 6-inch Dobsonian. If deep-sky is your priority, consider the Heritage 130P instead.

Accessories and Overall Value

The Inspire 100AZ includes a smartphone adapter — this is its single biggest value advantage over the AstroMaster. A good smartphone adapter typically costs $25–40 separately. The Inspire also comes with a 2× Barlow lens, giving you 26×, 66×, and 132× right out of the box.

The AstroMaster 70AZ includes a 20mm and 10mm eyepiece (35× and 70×). No Barlow, no smartphone adapter. The included accessories are functional but bare-bones. Most AstroMaster buyers will want to add a Barlow lens and a Moon filter within their first few sessions.

Value analysis: The Inspire costs more than the AstroMaster. You are paying for 2× the light gathering, the smartphone adapter, the 2× Barlow, and slightly better build quality. Whether this is worth it depends on your budget and goals. If you can afford the Inspire, the extra aperture will keep you satisfied longer. If budget is tight, the AstroMaster is still an excellent first telescope — and the money saved can buy a Barlow and a good eyepiece.

Our Pick — Inspire 100AZ for Best Views

Celestron Inspire 100AZ

The better telescope for buyers who can stretch their budget. 2× the light gathering, smartphone adapter included, Barlow included, sharper lunar and planetary views. The same mount limitations apply, but the optical upgrade is significant and immediately noticeable.

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Celestron AstroMaster 70AZ — Best Budget Alternative

If budget is the primary constraint, the AstroMaster 70AZ is still an excellent first telescope. Saturn's rings, Jupiter's moons, and stunning lunar detail are all on the menu. The money saved can buy a 2× Barlow and a 6mm eyepiece, closing the gap with the Inspire on planetary performance.

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