Sky-Watcher Skymax 180 Maksutov-Cassegrain OTA

Product Overview

The Skymax 180 is a 180 mm Maksutov-Cassegrain optical tube with 2700 mm of focal length at f/15. The folded Maksutov light path puts that focal length into a tube about 56 cm long and 22 cm across (22 inches by 8.625 inches), weighing about 8.6 kg (Sky-Watcher publishes 19 pounds). A refractor with the same focal length would be close to three metres long.

This listing is the optical tube assembly. It ships with a 2-inch 28 mm eyepiece, a 2-inch star diagonal, a 9x50 straight-through finderscope and a V-style dovetail; the mount and tripod are chosen separately. That leaves you free to put it on a mount you already own, or one chosen to suit it.

Who It's For

This is a good match if planetary, lunar and double-star detail is what you observe most, and you want more aperture and focal length than a 127 mm or 150 mm Maksutov gives you without moving to an open-tube design that needs collimating. Seven inches of aperture resolves finer detail than the smaller Skymax tubes, and 2700 mm of native focal length means high magnification arrives with ordinary eyepieces rather than a Barlow.

It also suits planetary imagers. At f/15 and 2700 mm, a planetary camera sits at a large image scale straight out of the focuser, which is the range high-resolution lunar and planetary work is done at.

It also works well if you observe from a backyard or an observatory pier and want one serious high-power instrument with no mirror alignment to maintain.

Key Features & Design

• 180 mm Maksutov-Cassegrain at 2700 mm, f/15: seven inches of aperture and a long native focal length in a 22 inch (approx. 56 cm) tube.
• Borosilicate mirrors with Radiant Aluminum Quartz (RAQ) coatings: Sky-Watcher publishes 94% reflectivity for these coatings on the primary and secondary.
• Full-aperture meniscus corrector with MHTC coating: the corrector seals the tube and carries Sky-Watcher's Metallic High-Transmission Coatings; Sky-Watcher's price list describes the optics as fully multi-coated.
• 2-inch dual-speed Crayford-style focuser: listed on Sky-Watcher's Skymax Series product sheet, with a 1.25-inch adapter for smaller accessories.
• 2-inch visual train included: a 2-inch star diagonal and a 2-inch 28 mm eyepiece (an LET eyepiece per Sky-Watcher's price list), giving 96x with the supplied eyepiece.
• 9x50 straight-through finderscope: a magnifying finder rather than a red dot, which helps when star-hopping at a focal length this long.
• V-style dovetail: fits Vixen-format saddles; Sky-Watcher's product sheet lists the mounting hardware for this aperture as V-style with mounting rings.
• Sealed optical tube: the closed design keeps dust off the mirrors and holds alignment, so there is nothing to collimate before a session.
• Aluminium tube with a glossy black diamond metal-flake finish.

Optical / Mechanical Design

A Maksutov-Cassegrain begins with a thick, full-aperture meniscus lens at the front of the tube. Light passes through it to a borosilicate primary mirror at the rear, reflects forward to a secondary spot aluminised onto the inner face of the meniscus, and returns through a central hole in the primary to the focuser. That fold is how 2700 mm of focal length fits in a 22 inch tube.

The design's reputation for sharp planetary images follows from that layout. The secondary is a coating on the corrector rather than a separate mirror on a spider, so there are no support vanes in the light path and no diffraction spikes. The meniscus surfaces are spherical, which allows them to be figured to a high standard, and the corrector reduces chromatic aberration while sealing the tube against dust and internal air currents. Sky-Watcher notes that Maksutovs are generally regarded as producing a sharper image than Schmidt-Cassegrains.

Sky-Watcher's product sheet lists a 2-inch dual-speed Crayford-style focuser on the Skymax 180. At f/15 the depth of focus is generous, but at 96x and above the point of best focus is still a small adjustment, and the fine-speed knob makes it easy to settle on without shaking the image at 2700 mm.

The f/15 focal ratio defines what the tube does best: a long, slow light cone gives high contrast and a well-corrected field at high magnification, with a correspondingly narrow field of view. It is a resolution instrument for small, bright targets rather than a wide-field scope.

Recommended Uses

• High-resolution planetary observing: 180 mm of aperture at 2700 mm on the cloud belts and festoons of Jupiter, the ring divisions of Saturn and surface markings on Mars near opposition.
• Lunar observing: rilles, domes, crater terracing and the terminator at high image scale.
• Lunar and planetary imaging: f/15 at native focal length gives a large image scale with a planetary camera, without adding a Barlow for most sensors.
• Double stars: the aperture and long focal length suit close and unequal pairs.
• Globular clusters and planetary nebulae: small, bright deep-sky objects that respond to aperture and magnification.
• Long-range terrestrial observing with an erecting diagonal.

Compatibility and Accessory Notes

The tube mounts on a V-style (Vixen-format) dovetail. At 19 pounds (about 8.6 kg) before the diagonal and eyepiece are added, and with 22 inches of tube length out front of the saddle, an HEQ5-class equatorial, an AZ-EQ5 or a heavier mount is the usual pairing for steady high-power views and tracked planetary imaging. Tell us which mount you have and we will confirm the fit and headroom with you.

The visual train is 2-inch. The supplied diagonal takes 2-inch eyepieces directly, and the focuser's 1.25-inch adapter means the 1.25-inch eyepieces and filters you already own work without extra purchases. With the supplied 28 mm eyepiece the magnification is 96x; shorter eyepieces scale from there (a 10 mm gives 270x).

For imaging, a 1.25-inch nosepiece planetary camera goes into the diagonal or the 1.25-inch adapter at the focuser. If you are planning a specific camera, a filter wheel or a T-thread connection, send us the model and we will work out the adapters you need.

Good to Know Before You Order

• This is the optical tube assembly. Eyepiece, diagonal, finderscope and dovetail are included; the mount and tripod are not. We can help you match a mount to it.
• Focal ratio is f/15, focal length 2700 mm. That is ideal for the Moon, planets and double stars and gives a narrow field: the lowest-power view with the supplied 28 mm eyepiece is 96x. Large nebulae and wide star fields are better served by a shorter, faster telescope.
• Sky-Watcher publishes the tube weight as 19 pounds (about 8.6 kg), with a tube 22 inches long and 8.625 inches in diameter. That is worth allowing for in your mount's payload once the diagonal, eyepiece and any camera are attached.
• Long-exposure deep-sky imaging is slow at f/15. The tube is suited to high-frame-rate lunar and planetary imaging rather than nebula and galaxy imaging.
• Maksutovs need time to cool. A 180 mm meniscus and sealed tube reach outdoor temperature more slowly than an open-tube telescope; the sharpest planetary views come once the optics have settled, so setting the tube outside early in the evening pays off.

Frequently Asked Questions

Is it difficult to set up?

No. The tube is sealed and aligned at the factory, so there is no collimation to perform. Setup is sliding the dovetail into your mount's saddle, balancing the tube, fitting the diagonal and eyepiece, and aligning the finderscope once in daylight. The main thing that takes time is cooldown, which happens while you set up the rest.

What is it best used for?

Lunar, planetary and double-star observing, and high-resolution lunar and planetary imaging. Its 2700 mm focal length and f/15 ratio are chosen for detail on small, bright targets.

What mount does it need?

A mount with a Vixen-style (V-format) saddle that comfortably carries 19 pounds plus diagonal, eyepiece and any camera. HEQ5-class equatorials, the AZ-EQ5 and heavier mounts are the usual choices. Tell us what you own and we will confirm it.

Can I photograph with it?

Yes, for the Moon and planets: a planetary camera at 2700 mm captures a large image scale, and the Crayford-style focuser holds the camera securely. For long-exposure deep-sky imaging, f/15 makes exposures long, so a faster telescope is the better tool for nebulae and galaxies.

How does it compare with the Skymax 150?

The Skymax 180 has 30 mm more aperture and 2700 mm of focal length versus 1800 mm, so it resolves finer detail and reaches higher magnification with the same eyepiece. It is also larger and heavier: 22 inches and 19 pounds against 17.5 inches and 14 pounds, so it calls for a sturdier mount.

Do I need to buy anything else to start observing?

A mount and tripod. The tube comes with a 28 mm eyepiece, diagonal and finderscope; a shorter eyepiece in the 10-15 mm range is the usual first addition for planetary magnification.

Bottom Line

A sealed 180 mm Maksutov-Cassegrain optical tube with 2700 mm of focal length at f/15, in a 22 inch, 19 pound package with a 2-inch dual-speed Crayford-style focuser, 2-inch diagonal, 28 mm eyepiece, 9x50 finderscope and V-style dovetail. Pair it with an HEQ5-class mount or heavier and it is ready for high-resolution lunar, planetary and double-star work - and we are happy to help you choose that mount.