Sky-Watcher Skymax 127 Maksutov-Cassegrain OTA

Product Overview

The Skymax 127 is a 127 mm Maksutov-Cassegrain optical tube working at 1540 mm of focal length and f/12.1. The folded Maksutov path puts that focal length into a tube 15 inches long and 5.75 inches across, weighing 9.7 pounds - roughly a five-inch aperture with the reach of a scope three times its length.

This listing is the optical tube assembly. It is not the Skymax 127 AZ-GTi, which is the same optics sold as a bundle with Sky-Watcher's motorised AZ-GTi mount and tripod. Here you get the tube, a 2-inch visual train and a V-style dovetail plate; the mount and tripod are separate choices - which is the point for buyers who already own a mount and want the optics on their own terms.

Who It's For

This is a good match if you have outgrown a small refractor on planetary detail and want more aperture without moving to a long tube or an open Newtonian. The step from 102 mm to 127 mm is a 55% increase in collecting area, and at 1540 mm the image scale on Jupiter, Saturn and lunar features is noticeably larger.

It also fits observers who want a 2-inch visual train. Unlike the 102, the Skymax 127 ships with a 2-inch star diagonal and a 2-inch 28 mm eyepiece, so wide-field eyepieces work at their full field stop and the low-power end of the range opens up considerably for a scope of this focal length.

If you own a mount in the AZ-GTi, AZ5, EQM-35 or HEQ5 class, the 9.7 pound tube is a comfortable load and this is a straightforward way to add long focal length to a kit you already have.

Key Features & Design

• 127 mm Maksutov-Cassegrain at 1540 mm f/12.1: long focal length folded into a 15 inch tube, which is where the planetary contrast comes from.
• Borosilicate mirrors with Radiant Aluminum Quartz (RAQ) coatings: Sky-Watcher publishes 94% reflectivity for these coatings.
• Full-aperture meniscus corrector with MHTC coating: the corrector seals the tube and carries Sky-Watcher's Metallic High-Transmission Coatings.
• 2-inch visual train: supplied with a 2-inch star diagonal and a 2-inch 28 mm eyepiece, so 2-inch wide-field eyepieces reach their full field.
• Sealed optical tube: the closed design holds collimation and keeps dust off the mirrors, so there is nothing to align before observing.
• V-style dovetail plate fitted: mates directly with Vixen-style saddles across small alt-azimuth and equatorial mounts.
• Included per Sky-Watcher's product page: a 2-inch 28 mm eyepiece, a finderscope, a V-style dovetail and a 2-inch diagonal.
• Glossy black diamond metal-flake finish on the aluminium tube.

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 at the back, reflects forward to a secondary spot aluminised directly onto the inner face of the meniscus, and returns through a central hole in the primary to the eyepiece. That three-bounce fold is how 1540 mm of focal length lives inside a 15 inch tube.

The design's advantage on planets follows from its geometry. The secondary is a coating on the corrector rather than a mirror on a spider, so there is no support structure in the light path and no diffraction spikes; the central obstruction is small relative to a Schmidt-Cassegrain of similar aperture. Sky-Watcher describes Maksutovs as generally regarded as producing a sharper image than Schmidt-Cassegrains, and this is the mechanism behind that. The meniscus is also spherical and therefore easier to figure accurately than an aspheric corrector, and being full aperture it seals the tube against dust and internal air currents.

The Skymax Series product sheet lists a 2-inch dual-speed Crayford-style focuser with a 1.25 inch adapter for the 127 mm column, giving fine control at the magnifications this focal length reaches.

At f/12.1 the cone is long and slow. That produces high contrast and a well-corrected central field at high power, with a correspondingly narrow field of view - the reason this is a Moon, planets and double stars instrument rather than a wide-field one.

Recommended Uses

• Planetary observing: 127 mm of aperture at 1540 mm resolves belt structure on Jupiter, the Cassini division on Saturn and surface albedo on Mars.
• Lunar observing: high image scale on crater floors, rilles and the terminator.
• Double stars: a sealed, thermally stable tube and long focal length suit close pairs.
• Lunar and planetary imaging: a planetary camera at native focal length gives large image scale without a Barlow.
• Globular clusters and planetary nebulae: the extra aperture over the 102 puts these within comfortable reach at moderate power.
• Terrestrial and long-range spotting with an erecting diagonal.

Compatibility and Accessory Notes

The tube is supplied on a V-style (Vixen-format) dovetail plate, which is the saddle standard on the AZ-GTi, AZ5, Star Adventurer GTi, EQM-35 and HEQ5 heads. At 9.7 pounds it sits comfortably within the payload of any of those with room for a diagonal and eyepiece on top.

The visual train is 2-inch, and the supplied diagonal accepts 2-inch eyepieces directly. A 1.25 inch adapter is listed with the focuser, so the existing 1.25-inch eyepieces and filters in your case work without buying anything.

For imaging, a planetary camera goes into the diagonal or straight into the visual back. Because focus is achieved inside the tube rather than through a limited drawtube travel, the scope tolerates accessories of varying optical depth without spacer arithmetic. If you have a specific camera or a T-thread connection in mind, send us the model and we will confirm the adapter.

If you would rather have this scope with a mount and tripod as one package, the Skymax 127 AZ-GTi bundle is the version to look at, and we stock it separately.

Good to Know Before You Order

• This is the optical tube assembly, not a complete telescope package. The eyepiece, diagonal, finder and dovetail are included; no mount and no tripod. The Skymax 127 AZ-GTi bundle is the mounted version, sold as its own product.
• Focal ratio is f/12.1. Long and slow: excellent contrast at high power, a narrow field for large deep-sky objects, and a slow proposition for long-exposure deep-sky imaging.
• Sky-Watcher publishes tube weight as 9.7 pounds. Shipping weight is higher once accessories and packaging are added.
• The finder specification differs between Sky-Watcher's two publications. Their product page lists a 6x30 finderscope for the Skymax 127; their Skymax Series product sheet lists a 9x50 straight-through finder for the 127mm column. We confirm which finder is in the carton before shipping, and will tell you which one your unit has if you ask.
• Maksutovs need cooldown. The sealed tube and thick corrector equalise with ambient temperature more slowly than an open tube, and at 127 mm that takes longer than it does on the 102. The sharpest views come once the optics have settled.
• No carrying case is listed for this model in Sky-Watcher's published accessory list, unlike the Skymax 102.
• Free shipping applies to this item per Sky-Watcher's listing.

Frequently Asked Questions

Is it difficult to set up?

No. The tube is sealed and collimated at the factory, so there is no mirror alignment to perform when it arrives or later. Setup is: dovetail into the mount saddle, clamp, diagonal and eyepiece into the back, aim with the finder. At 9.7 pounds it is a comfortable one-handed lift onto a saddle. Cooldown is the only part that takes time, and it runs while you set up everything else.

How is this different from the Skymax 127 AZ-GTi we also sell?

Same optical tube. The AZ-GTi version adds Sky-Watcher's motorised, app-controlled AZ-GTi mount head and a tripod. This listing is the tube alone, for people who already have a mount.

Is the step up from the Skymax 102 worth it?

127 mm gathers about 55% more light than 102 mm, and the focal length goes from 1300 mm to 1540 mm. The other real difference is the visual train: the 127 comes with a 2-inch diagonal and a 2-inch 28 mm eyepiece where the 102 is 1.25-inch throughout. The trade is weight - 9.7 pounds against 4.6.

What mount does it need?

Anything with a Vixen-style saddle carrying 9.7 pounds plus accessories - AZ-GTi, AZ5, EQM-35, HEQ5 and similar. Tell us what you own and we will confirm the fit.

Can I photograph with it?

Lunar and planetary imaging works well at 1540 mm with a planetary camera. At f/12.1 long-exposure deep-sky imaging is slow, so this is not the tube people choose for nebulae and galaxies.

Bottom Line

A sealed 127 mm Maksutov-Cassegrain optical tube delivering 1540 mm of focal length in a 15 inch, 9.7 pound package, supplied with a 2-inch star diagonal, a 2-inch 28 mm eyepiece, a finderscope and a V-style dovetail. It is the tube-only version of the Skymax 127 - pair it with a mount you already own, or send us your setup and we will match one to it.