Celestron NexStar 127SLT: A Guide to This Compact Computerised Maksutov

The Celestron NexStar 127SLT pairs a compact 127 mm Maksutov-Cassegrain telescope with a computerised “GoTo” mount that can find and track thousands of objects. This page combines two earlier posts about the same telescope into one guide, with specifications checked against Celestron’s own listing.

What is a Maksutov-Cassegrain?

A Maksutov-Cassegrain (“Mak”) is a compound telescope. Light enters through a thick, curved glass corrector lens at the front, bounces off a curved main mirror at the back and is reflected again by a small mirrored spot on the corrector, then passes through a hole in the main mirror to the eyepiece. Folding the light path this way packs a long focal length into a short tube.

That long focal length gives high magnification with ordinary eyepieces and a narrow field of view, which makes Maks especially good for the Moon, planets and double stars. The sealed tube rarely needs alignment and keeps dust off the mirror.

Verified specifications

From Celestron’s product page:

• Optical design: Maksutov-Cassegrain
• Aperture: 127 mm (5 in)
• Focal length: 1500 mm; focal ratio f/12
• Eyepieces: 25 mm (60x) and 9 mm (167x), with a 1.25-inch star diagonal
• Finder: StarPointer red-dot finder
• Highest/lowest useful magnification: 300x / 18x
• Limiting stellar magnitude: about 13
• Light-gathering power: about 329 times the human eye
• Optical tube: 381 mm (15 in) long; about 3.95 kg (8.7 lb)
• Mount: computerised altitude-azimuth single fork arm; payload capacity 3.6 kg (8 lb)
• Tripod: adjustable stainless steel with accessory tray
• Database: more than 40,000 objects in the NexStar+ hand control
• Power: 8 AA batteries (not included) or a 12 V DC supply
• Two-year warranty when bought new

Celestron currently bundles Starry Night Special Edition software and access to its SkyPortal app; older kits included The SkyX First Light Edition.

How the GoTo mount works

After setting up the tripod and entering your location, date and time, you align the telescope on a few bright stars or planets. Celestron’s SkyAlign method lets you centre any three bright objects, even if you don’t know their names, and the hand control works out where it is pointing. Other options include Auto Two-Star, One-Star and Solar System Align (using the Moon or a bright planet).

Once aligned, you can choose an object from the menu and the mount slews to it, then tracks it as Earth turns. That saves a lot of time for beginners who are still learning the sky, and it keeps planets centred at high magnification.

Tips for good alignment: level the tripod, enter the date and time carefully (including daylight saving), and make sure the red-dot finder is lined up with the main telescope during the day.

What you can see

The 127SLT’s long focal length favours bright, compact targets:

• The Moon: crisp, high-contrast craters and rilles.
• Jupiter: cloud belts, the four Galilean moons and, on steady nights, the Great Red Spot.
• Saturn: rings and the Cassini Division, plus its largest moon, Titan.
• Mars near opposition: polar caps and dark surface markings on good nights.
• Double stars such as Albireo and Mizar-Alcor, and bright globular clusters like M13.

Because the field of view is narrow, very large objects such as the Pleiades or the whole Andromeda Galaxy won’t fit in the eyepiece, and faint galaxies appear dim through 127 mm of aperture.

Practical considerations

• Cool-down time. The thick corrector and closed tube take time to match outside temperatures. Set the telescope outside 30 to 45 minutes before observing for sharper views.
• Dew. The front corrector can fog up on humid nights. A dew shield helps.
• Power. Eight AA batteries drain fairly quickly on cold nights. Many owners use a rechargeable 12 V power pack.
• Payload. The SLT mount is rated for 8 lb, so heavy cameras or accessories may overload it.

Daytime use

With the included star diagonal, the 127SLT can be used for terrestrial viewing, though the image may be mirror-reversed left-to-right. An erect-image diagonal gives a fully correct view.

Who it suits

The NexStar 127SLT suits observers who want a portable, low-maintenance telescope focused on the Moon, planets and double stars, and who like the convenience of computerised finding and tracking. If your main interest is wide star fields or faint deep-sky objects, a larger reflector may suit you better.

Safety note

Never point the telescope at the Sun without a certified solar filter covering the front.