Explore Scientific AR152 152mm f/6.5 Air-Spaced Doublet Refractor (OTA)

Product Overview

The Explore Scientific AR152 is a 152mm (6-inch) air-spaced crown-and-flint achromatic doublet refractor with a native focal length of 988mm at f/6.5. It is the largest aperture in the AR Series, and at this focal ratio it is built around wide, bright, low-power views rather than long-focus planetary work.

It is sold as an optical tube assembly with its accessory package — a 2-inch dual-speed focuser, a one-piece 2-inch dielectric diagonal, an 8x50 finderscope on the Hybrid 2N1 base, and a cradle ring set with a 45mm V-block dovetail. No mount and no eyepieces are included.

Who It's For

• Visual deep-sky observers: 152mm of aperture at f/6.5 gathers roughly 470x the light of the naked eye, with a stated limiting magnitude of 13.4 and 0.77 arcsec resolution.
• Wide-field observers: at 988mm with a 2-inch focuser, large open clusters, the Veil and the Andromeda halo fit in a single field in a way a long-focus instrument cannot manage.
• Outreach and public star parties: the accessory package is specified for heavy handling, and a refractor needs no collimation between events.
• Observers moving up in aperture who want a refractor's contrast and zero-maintenance optics rather than a reflector's. This is a good match if you already have a mount rated well above 23 lb and want the largest achromat that mount will carry.

Key Features & Design

• 152mm air-spaced doublet: crown-and-flint achromat, air-spaced rather than cemented.
• 988mm focal length, f/6.5: a fast focal ratio for a 6-inch refractor, which is what keeps the tube and the true field manageable.
• 2″ dual-speed focuser: coarse and fine control on the same knob for setting focus at high power.
• One-piece 2″ diagonal with 99% dielectric coatings: included, not an upsell.
• Hybrid 2N1 finder scope base: takes both finder-shoe standards, with an 8x50 non-illuminated straight-through finderscope and quick-release bracket supplied.
• Cradle ring set with 45mm wide V-block dovetail, similar to the Vixen dovetail standard.
• Published weight 23 lb (10.7 kg) for the tube assembly, and 41″ (1041mm) long with the dew shield extended.

Optical Design

An air-spaced achromatic doublet brings two wavelengths to a common focus using a crown element and a flint element separated by an air gap. The air gap gives the designer two extra optical surfaces to work with compared to a cemented doublet, and it removes the cement layer as a thermal and optical variable in a large lens — which matters more at 152mm than at 80mm.

An achromat is not an apochromat, and the difference is visible on the brightest targets: Venus, Jupiter, Sirius and the limb of the Moon will show some colour fringing at high power, which is inherent to two-element crown-and-flint designs rather than a defect in this one. On extended deep-sky objects, star clusters and low-power sweeping it is not a factor, and that is the observing this focal ratio is built for. Observers who want to reduce it at high power typically add a fringe-killer or minus-violet filter; if you want the colour gone entirely rather than reduced, an ED or apochromatic triplet is the design to look at, and we stock those.

The 41-inch tube with the dew shield out, at 23 lb bare, is a substantial optical tube. The 45mm V-block dovetail spreads that load across the cradle rings rather than concentrating it at a single saddle point.

Recommended Uses

• Low and medium-power visual observing of open clusters, nebulae and the brighter galaxies.
• Lunar and planetary observing at moderate magnification.
• Double-star work, where 0.77 arcsec resolution is the governing figure.
• Public outreach and educational sessions.
• Wide-field and solar-system astrophotography on a suitably rated equatorial mount.

Compatibility and Accessory Notes

• Mount: not included. The published tube weight is 23 lb before the diagonal, finder and eyepiece, so the loaded tube sits higher. For visual use a mount rated at 30 lb or more is the sensible starting point; for imaging, more again.
• Dovetail: the 45mm wide V-block fits Vixen-style saddles. A saddle that takes both Vixen and Losmandy plates will accept it.
• Eyepieces: none included. The 2-inch focuser and diagonal take both 2-inch and, with the supplied adapter, 1.25-inch eyepieces. At 988mm, a 30mm eyepiece gives 33x and a 9mm gives 110x.
• Finder: the Hybrid 2N1 base accepts finder shoes of both common patterns, so an illuminated or right-angle finder can replace the supplied 8x50 without changing the base.
• Filters: the 2-inch diagonal accepts 2-inch threaded filters. A minus-violet or fringe-killer filter is the usual pairing for high-power lunar and planetary work with a fast achromat.
• Imaging: a field flattener is needed for anything approaching a flat field across an APS-C sensor. Explore Scientific does not publish a corrected image circle for this tube, so we do not quote one — send us your camera and we will confirm what fits.

Good to Know Before You Order

• This is an optical tube assembly, not a complete telescope. A mount and tripod are needed to use it, and so is at least one eyepiece. We can put a package together if it is easier — just ask.
• It is a 23 lb, 41-inch tube. That is a two-hands instrument to carry and mount, and it wants a mount with real capacity underneath it. Worth accounting for if you set up and tear down each session.
• Achromatic, not apochromatic. Some colour on the brightest objects at high power comes with the design. A minus-violet filter reduces it, and at the low and medium powers this focal ratio is built for it is not the limiting factor.
• Dew shield length is included in the 41-inch figure. Check it against your case or vehicle before ordering if transport is a consideration.
• Explore Scientific publishes no corrected image circle or backfocus figure for this tube, so those rows are absent from the specifications rather than estimated. If you are planning an imaging train, send us the camera and flattener you have in mind and we will work out the spacing with you.

Frequently Asked Questions

Is it difficult to set up?

The telescope itself is straightforward — a refractor needs no collimation, so it is ready as soon as it is on the mount. The work is in the handling: at 23 lb and 41 inches it takes two hands to lift onto a saddle, and it is easier with the mount already levelled and balanced.

What mount do I need?

One rated comfortably above the loaded tube weight. 23 lb bare becomes more once the diagonal, finder and a 2-inch eyepiece are on it, so 30 lb of rated visual capacity is a reasonable floor. Tell us what you have and we will tell you honestly whether it will carry this.

Does it come with eyepieces?

No. The 2-inch diagonal, 8x50 finder and cradle rings are included; eyepieces are chosen separately.

Will I see colour fringing?

On Venus, Jupiter, Sirius and the lunar limb at high magnification, yes — that is what an achromatic doublet does. On clusters, nebulae and galaxies at the low to medium powers this scope is built for, it is not something you notice.

Can I image with it?

For the Moon, planets and wide-field work on a properly rated equatorial mount, yes. For deep-sky imaging it needs a field flattener, and the achromatic design will record more colour around bright stars than an ED or apochromatic tube would.

How does it compare to the AR102 and AR127?

Same optical design and same f/6.5 focal ratio, scaled up. The AR152 gathers the most light and resolves the finest detail of the three, at 23 lb against the smaller tubes' lighter weights. Aperture and portability trade directly against each other across the series.

Bottom Line

In short: a 152mm f/6.5 air-spaced achromat supplied as a tube assembly with a 2-inch dual-speed focuser, dielectric diagonal, 8x50 finder and Vixen-style dovetail — a wide-field, low-maintenance six inches of aperture that needs a mount rated well above its 23 lb. If you are matching it to a mount you already own, send us the model and we will confirm the fit before you order.