A parabolic mirror and a flat diagonal
The primary mirror is ground to a paraboloid, the shape that brings parallel starlight to a single point. A flat secondary mirror, tilted at 45°, sits on a four-vane spider near the top of the tube and sends the light out the side. The vanes cause the four-pointed spikes on bright stars in Newtonian photographs.
Newtonians come on three kinds of mount: Dobsonian rocker boxes for visual use, equatorial mounts for tracking and imaging, and small altitude-azimuth mounts for beginner models.
Fast Newtonians trade a larger obstruction for wide, bright imaging fields
Imaging Newtonians run f/4 to f/5 with large secondary mirrors to cover a camera sensor fully; visual ones run f/5 to f/8 with smaller secondaries for higher contrast on planets. All fast Newtonians show coma, stars drawn into small comet shapes toward the edge of the field, which a coma corrector lens removes.
| Telescope | Aperture | Focal length | Ratio | Obstruction | Resolves | Widest field | Max power |
|---|---|---|---|---|---|---|---|
| StarSense Explorer DX 130AZ | 130 mm | 650 mm | f/5.0 | 33% | 0.9" | 2.4° | 260x |
| Quattro 150P | 150 mm | 600 mm | f/4.0 | 37% | 0.8" | 4.4° | 300x |
| Quattro 200P | 203 mm | 800 mm | f/3.9 | 34% | 0.6" | 3.3° | 350x |
| Quattro 250P | 254 mm | 1,000 mm | f/3.9 | 32% | 0.5" | 2.6° | 350x |
| Quattro 300P | 305 mm | 1,200 mm | f/3.9 | 33% | 0.4" | 2.2° | 350x |
Obstruction figures are approximate, as a share of the aperture's diameter. Widest true field uses the largest eyepiece the focuser takes: a 46 mm field stop for 2-inch focusers, 27 mm for 1.25-inch. Highest useful power is 2x per millimeter of aperture, capped at 350x by the air.
Current Newtonians from Sky-Watcher and Celestron
Sky-Watcher's Quattro line, made by Synta in China, dominates imaging Newtonians in the US; Celestron sells beginner Newtonians with phone-guided pointing.
| Model | Maker | Aperture | Ratio | US price | Notes |
|---|---|---|---|---|---|
| StarSense Explorer LT 114AZ | Celestron | 114 mm | f/8 | sold out | Entry-level; phone-guided |
| StarSense Explorer DX 130AZ | Celestron | 130 mm | f/5 | $500 | Phone-guided; alt-azimuth mount |
| Quattro 150P | Sky-Watcher | 150 mm | f/4 | $665 | Tube only; imaging |
| Quattro 200P | Sky-Watcher | 203 mm | f/4 | $925 | Tube only; imaging |
| Quattro 250P | Sky-Watcher | 254 mm | f/4 | $1,325 | Tube only; imaging |
| Quattro 300P | Sky-Watcher | 305 mm | f/4 | $1,995 | Tube only; needs a heavy mount |
Prices are from US dealers in November 2026; tariffs on Chinese-made optics raised most prices in 2025.
Best for fast deep-sky imaging and big-aperture visual observing
Newtonians give the most aperture per dollar on an equatorial mount and are fast enough to image nebulae and galaxies in short exposures. Their costs are collimation, which must be checked often, an open tube that lets in dust and dew, and a large central obstruction that softens planetary contrast slightly. A Quattro 200P weighs about 20 lb and needs a mount rated for 30 lb or more, such as a Sky-Watcher EQ6-R or a ZWO AM5.