Sky-Watcher Esprit 100 EDX Super APO Triplet f/5.5 Telescope

The Esprit 100EDX: A 100 mm f/5.5 Super APO for Imaging

Sky-Watcher designs the Esprit EDX series primarily for astro-imagers, and says they are also fine telescopes for visual observation. The manual describes no visual color fringing even on bright objects.

Esprit 100EDX Optical Design: A 100 mm Air-Spaced FPL-53 Triplet

The objective is a three-element, air-spaced lens with one Ohara FPL-53 ED element.

Each air-to-glass lens surface carries Sky-Watcher's Metallic High-Transmission Coatings (MHTC), and the optical system is knife-edge baffled.

Visual Observing

Accessories needing 185 mm of back focus or less from the end of the focuser tube, with the 2-inch adapter, can be used.

The telescope is supplied without eyepiece, star diagonal and finderscope. The finderscope can be removed from its shoe during an observation if it gets in the way.

The Optional Flattener: 40 mm Image Circle, 69.8 mm Back Focus

The dedicated Esprit 100 field flattener is sold separately. The manual gives a 40 mm image circle with a full-frame corrected focal plane, and says no universal flattener will match it, as it is designed for this telescope only.

The distance from the flattener's last lens to the sensor should be exactly 69.8 mm. For a DSLR, the flattener, an extender tube and an enlarged 48mm T-ring (matched to your camera, may not be included) give that 69.8 mm.

The 3-inch Focuser: 11:1 Dual-Speed Rack and Pinion Precision

The 3-inch CNC-machined rack and pinion linear power focuser has 11:1 dual-speed fine focusing. To focus, unlock the lever below the focuser, turn the knobs until the image is nearly sharp, then use the 1:11 knob. Lock the lever if a heavy load is attached.

The back end dispenses with the previous model's capstan wheel so the focuser rotates more easily. To rotate the focuser body, remove all accessories, fully retract the drawtube, loosen the screw, rotate the body and lock the screw. A rotatable adaptor on the drawtube also helps frame your images. An indexed scale on the drawtube shows the focus position for each accessory; fine tuning is still advised.

Mechanical Build: A 7.36 kg OTA with D-Style Plate and Case

The optical tube assembly weighs 7.36 kg (16.2 lb) and has a length of 565 mm with its non-retractable dew shield. It comes with CNC-machined aluminum tube rings with a carrying handle and a 75 mm D-style (Losmandy) dovetail bar.

A Sky-Watcher finderscope mounting shoe is fitted, and a foam-lined aluminum carrying case is included.

Imaging Train Connections: M74, M66, and M48 Thread Standards

The focuser drawtube ends in an M74 x 1 male thread, for the optional dedicated field flattener.

When setting up an imaging train, the connection standards are as follows:

• DSLR Cameras: The optional flattener connects to an extender tube, which in turn connects to an enlarged 48mm T-ring (may not be included) that matches your camera model. A Canon EOS camera adapter is included in the box.
• Astronomy Cameras: For CCD or CMOS cameras, the manual specifies the need for a custom adapter ring. This ring needs a female M66x1 thread to fit the flattener's exit, with a length that gives the 69.8 mm distance to the sensor.
• Front Accessories: Removing the dew shield exposes a male M107x1 thread on the objective lens cell, which the manual notes can be used for attaching accessories like filters.

Mounting the 7.36 kg Optical Tube

The optical tube weighs 7.36 kg (16.2 lb) and is 565 mm long. It mounts with a 75 mm D-style (Losmandy) dovetail bar, so it needs a D-style saddle.

Care and Transport for the 565 mm OTA

The Esprit 100EDX comes in a foam-lined aluminum carrying case.

First Night: Cool-Down, Focus and Solar Safety

Before you begin observing or imaging, your telescope needs time to acclimate to the outdoor air temperature. The manual says it needs at least 20 minutes to cool to outside conditions, and longer if there is a big temperature difference, to avoid tube currents.

To achieve focus, first ensure the focuser's locking lever is unlocked. Use the coarse focus knob to bring an object nearly into focus, then use the 1:11 fine-focus knob. Once focus is set, you can lock the lever to secure the drawtube, which is recommended when a heavy imaging train is attached.