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A 5-inch f/2 astrograph that gathers deep-sky data in a fraction of the time
Why we like the HAC125DX:
- Very fast: at f/2 it collects light about six times faster than an f/4.9 astrograph of the same focal length, such as the RedCat 51. A night of short exposures goes a long way.
- Small and light: 125mm of aperture in a tube 15.7" (398mm) long that weighs 8.4lb (3.8kg), so a mid-size mount like the EQ-AL55i Pro or Wave 100i carries it easily.
- Easier focusing than the original HAC125: a helical focuser at the back moves the primary mirror, so the camera stays put while you focus.
- Worth knowing: it's made for small sensors. Sky-Watcher rates the image circle at 16mm, but we've found the sharp part of the field is smaller: cameras with a full 16mm diagonal, such as the ASI533, need some cropping for pinpoint corner stars, and IMX585 cameras need a little less. It's an imaging-only telescope, with no eyepiece option.
The Sky-Watcher HAC125DX Minigraph is a 125mm f/2 Honders Advanced Catadioptric astrograph for wide-field deep-sky imaging with a small astronomy camera. Light passes through a corrector lens, reflects off a Mangin primary mirror and comes to focus at the front of the tube, where the camera attaches with the included 1.25" or M42 adapter. It's for imagers who want fast results from a light-polluted backyard or a quick trip to a dark site, without a heavy mount.
Key specs: 125mm aperture · 250mm focal length, f/2 · 16mm image circle · Mangin primary with RAQ coatings (94% reflectivity) · rear primary-mirror helical focuser · 1.25" and M42 × 0.75 camera adapters · 15.7" (398mm) long · 8.4lb (3.8kg)
The HAC125DX is on display in our Denver store, so you can see it in person before you buy.
What you can image
- Emission nebulae: the Orion Nebula and Running Man, the Lagoon and Trifid Nebulae (M8 and M20), the Eagle Nebula (M16) and the Rosette Nebula fill a good part of the frame.
- Faint, large targets: the speed of f/2 helps with dim objects like the Pacman Nebula, the Elephant's Trunk in IC 1396 and sections of the Veil Nebula.
- Galaxies: the Andromeda Galaxy's core and its companions, the Triangulum Galaxy (M33), and Bode's and the Cigar Galaxies (M81 and M82) together.
- Star clusters: the Pleiades with their dust, and the Double Cluster.
With an IMX585 camera (11.2 × 6.3mm sensor) the field is about 2.6° × 1.4° at 2.4 arcseconds per pixel. With an IMX533 camera (11.3 × 11.3mm) it's about 2.6° × 2.6° at 3.1 arcseconds per pixel, before cropping.
How it works
The HAC design puts the focal point in front of the optics. Thread the 1.25" or M42 × 0.75 adapter onto your camera and attach it at the front of the tube, then turn the green focus knob at the back to move the primary mirror until stars are sharp. The primary mirror cell can be collimated, and clamshell rings with a Vixen-style (V) dovetail fit most mounts.
At f/2, exposures of 30 to 60 seconds go a long way, so many imagers skip autoguiding on a well-aligned mount. Focus is critical at this speed, so check it as the temperature drops during the night.
What to add for the best results
- A small astronomy camera (required): the ZWO ASI585MC Pro (cooled) or ASI585MC (uncooled) sit comfortably inside the image circle. The ASI533MC Pro gives a square frame but needs some corner cropping.
- A mount (required): the Sky-Watcher EQ-AL55i Pro carries 22lb, and the Wave 100i carries 22lb with no counterweight. Both leave room for the camera and accessories.
- ZWO ASIAIR Plus 256GB: runs the camera, plate solving and your imaging plan from your phone.
- Celestron PowerTank Lithium Pro: 12V power for the mount and a cooled camera in the field.
HAC125DX vs. a small refractor astrograph
| HAC125DX | William Optics RedCat 51 III | |
|---|---|---|
| Design | Catadioptric (corrector lens + Mangin mirror) | Petzval refractor |
| Aperture | 125mm | 51mm |
| Focal length | 250mm (f/2) | 250mm (f/4.9) |
| Relative exposure time | 1x | About 6x longer |
| Camera position | Front of the tube | Rear focuser |
| Visual use | No | Yes, with a diagonal |
| Best for | Small-sensor cameras and short exposures under bright skies | A lighter setup that also works for visual observing |
See all Sky-Watcher telescopes.
What's in the box
- Sky-Watcher HAC125DX optical tube with rear helical focuser
- Clamshell rings with Vixen-style (V) dovetail
- Dew shield
- 1.25" camera adapter
- M42 × 0.75 (T2) camera adapter
The camera, mount, finder and power supply are sold separately.
Sky-Watcher HAC125DX FAQ
Is the HAC125DX good for beginners?
It's a good second step. The speed makes short exposures work and forgives small tracking errors, but you'll need to be comfortable with a mount, a camera and critical focus. If you're just starting, we're happy to walk you through a complete setup.
Which camera works best?
A camera with a sensor diagonal well under 16mm, such as the IMX585-based ASI585MC Pro. Larger 16mm sensors like the ASI533MC Pro work with some cropping. APS-C and full-frame cameras are too large.
Can I use it for visual observing?
No. The focal point sits at the front of the tube, made for a camera. For visual use, pick a refractor or SCT.
Do I need to autoguide?
Often not. At f/2, exposures of under a minute collect plenty of signal, and a well-polar-aligned mount can usually hold that. Guiding still helps for longer exposures with narrowband filters.
What mount do I need?
The tube weighs 8.4lb (3.8kg). Add a camera, cables and dew control and you're at about 11 to 13lb, so a mount rated for 20lb or more, like the EQ-AL55i Pro or Wave 100i, is a good match.
Can I see one before I buy?
Yes. The HAC125DX is on display in our Denver store. Stop by and we'll show you how the camera mounts and how the focuser works.
Specifications
| Optics | |
|---|---|
| Design | Honders Advanced Catadioptric (HAC) |
| Aperture | 125mm |
| Focal length | 250mm (f/2) |
| Image circle | 16mm |
| Primary mirror | Mangin, borosilicate; Radiant Aluminum Quartz (RAQ) coating, 94% reflectivity |
| Corrector coating | HTMC |
| Central obstruction | 53mm |
| Optical quality | Diffraction limited (1/4 wave) |
| Mechanical | |
| Focuser | Rear primary-mirror helical, single speed |
| Collimation | Adjustable primary mirror cell |
| Camera connection | 1.25" barrel; 1.25" and M42 × 0.75 adapters included |
| Mounting | Clamshell rings with Vixen-style (V) dovetail; two finder brackets |
| Physical | |
| Tube length | 398mm (15.7 in) |
| Tube diameter | 6.3 in |
| Weight | 3.8kg (8.4lb) |
| Model / SKU | Sky-Watcher HAC125DX (S11250) |