Starfield Optics Gear70Q 70mm f/5 Quad Petzval Astrograph

Product Overview

The Starfield Optics Gear70Q is a 70 mm f/5 quadruplet Petzval astrograph built for wide-field deep-sky imaging. At 350 mm focal length it holds large nebulae, open clusters and the bigger galaxies inside a single frame, and the four-element Petzval layout corrects the field inside the telescope rather than at the camera end. The corrected image circle is 44 mm, which covers a full-frame sensor, so there is no separate field flattener to buy, thread on, or space out.

The camera end is an M48 male thread, fed by a Camera Angle Adjuster that carries a female M54 thread and an included M54-to-M48 step-down adapter. Working distance from that M48 thread runs 41–61 mm — a 20 mm window rather than a single figure, which leaves room for a filter drawer or an off-axis guider alongside the camera. The Gear70Q is an imaging instrument: Starfield Optics does not intend the Gear series quads for visual observing.

Who It’s For

This is a good match if you photograph the sky rather than look through it, and you want the widest, flattest field you can get out of a small refractor.

• Deep-sky imagers working wide: 350 mm at f/5 is the range where the North America Nebula, the Pleiades and the Andromeda Galaxy sit comfortably inside the frame instead of running off the edges.
• Full-frame and APS-C shooters: the 44 mm corrected circle covers both, whether you are using a cooled astronomy camera or a DSLR or mirrorless body.
• Travel and grab-and-go rigs: a 70 mm f/5 tube is light enough for a small tracker-class or portable equatorial mount, and the supplied case is cut so the focus motor stays mounted between sessions.
• Anyone building their first serious astrograph: the Petzval design removes the flattener spacing exercise entirely, which is the step that most often costs a beginner their corner stars. The wide 41–61 mm working distance means an imaging train that is close is also correct.

Visual observers are the one group this is not built for — see Good to Know Before You Order below.

Key Features & Design

• 70 mm (2.8″) aperture at f/5: a fast focal ratio that shortens the exposure needed to reach faint nebulosity.
• 350 mm focal length: wide-field framing for large emission nebulae, open clusters and the nearer galaxies.
• Four-element quad Petzval design: field correction is built into the optical train, so no additional flattener is required for wide-field imaging.
• FPL-53 glass: the high-dispersion element that controls colour error and keeps bright stars free of violet fringing.
• Fully multi-coated optics: maximises transmission and holds down internal reflections around bright stars.
• 44 mm corrected image circle: full-frame coverage, edge to edge.
• 2.5″ dual-speed rack-and-pinion focuser: coarse and fine knobs, with the load capacity for a camera, filter wheel and off-axis guider together.
• Camera Angle Adjuster (CAA): rotates the sensor to your chosen framing angle without breaking the imaging train apart.
• Vixen-style dovetail plate and heavy-duty rings: mounts on the widest range of equatorial heads, with accessory holes on the rings and a finder-shoe dovetail on the carry handle.
• Fitted soft case: accessory cutouts inside, including one that lets the focus motor stay on the drawtube between sessions.

Optical & Mechanical Design

A Petzval is a refractor with its corrector built in. Where a conventional doublet or triplet astrograph puts two elements at the front and relies on a separately purchased flattener near the camera to straighten the field, the Gear70Q carries four elements in two groups — the objective at the front and a correcting group further down the tube. The field arrives at the sensor already flat. That is why the specification sheet lists a 44 mm corrected circle with no flattener named alongside it: the correction is not an accessory, and there is no second optic whose spacing you have to solve.

The practical consequence shows up in the working distance. On a flattener-based system the backfocus figure is a target you hit within a millimetre or so, and missing it shows as elongated corner stars. On the Gear70Q the usable range is 41–61 mm from the M48 output, which is wide enough that a camera, a filter drawer and an adapter or two can be stacked in any sensible order and still land inside it. FPL-53 handles the colour correction across that field, and the 2.5″ dual-speed rack-and-pinion focuser carries the resulting imaging train without the drawtube sag that costs sharpness on longer exposures. A tilt adjustment accessory is supplied with the Gear series for the rare case where the sensor plane needs squaring up after everything is threaded and focused.

Recommended Uses

• Wide-field deep-sky astrophotography: large emission and reflection nebulae, open clusters, and galaxies with generous apparent size.
• Mosaic panels: a flat 44 mm field makes adjacent panels stitch without corner mismatch.
• Narrowband imaging from light-polluted skies: f/5 keeps exposure times workable behind narrow filters.
• Portable and travel imaging: dark-sky trips, star parties, and backyard setups where the rig goes out and comes in each night.
• A second scope on a dual-rig mount: short enough and light enough to ride alongside a longer instrument.

Compatibility and Accessory Notes

• Camera thread: the final telescope-side output is M48 male. Most cooled astronomy cameras and DSLR/mirrorless T-adapters reach it directly or with a single M48 spacer.
• Rotator thread: the CAA presents a female M54 thread, and the M54-to-M48 step-down adapter comes in the box. An M54 imaging train can also be built directly off the CAA if you prefer the larger thread.
• Working distance: 41–61 mm measured from the M48 thread. Sensor-to-flange distances vary by camera, so if you would like a second pair of eyes on your train, send us your camera, filter drawer and adapter list and we will add it up with you.
• Field flattener: none needed, and none is offered for this model. The Petzval group does that job.
• Mounting: a Vixen-style dovetail plate is fitted to the supplied rings, which fits the standard saddle on the great majority of equatorial mounts. The rings carry accessory holes, and the handle has a finder-shoe dovetail for a guide scope or a polar scope.
• Guiding: at 350 mm a small guide scope is the usual approach — the Starfield 50 mm Guide Scope Gen II mounts to the finder shoe on the handle.
• Dew control: a heater strap sized to the dew shield paired with the Starfield four-channel dew controller keeps the objective clear on damp nights. The add-on selector on this page carries the matched strap; if you are ordering by phone we will size it for you.

Good to Know Before You Order

• This is an imaging telescope, not a visual one. Starfield Optics states that the Gear series quads are not intended for visual observing. There is no diagonal or eyepiece path in the design, and the M48 output goes to a camera.
• Focal length suits wide fields, not planets. At 350 mm the image scale is built for large deep-sky targets. Planetary and lunar close-ups are the province of much longer focal lengths.
• A camera adapter is still yours to supply. The M54-to-M48 step-down comes with the telescope; the spacer or T-adapter that matches your particular camera’s backfocus does not. Send us the camera model and we will tell you what it takes.
• A tracking mount is assumed. Deep-sky exposures at 350 mm need an equatorial or tracker-class mount; the telescope ships with the dovetail plate that attaches to one, not the mount itself.
• Shipping weight is 12 lb as published by Starfield Optics — that figure covers the telescope in its case with the supplied rings and plate, so the tube alone rides lighter on the mount than the number suggests.

Frequently Asked Questions

Is it difficult to set up?

No — this is one of the more forgiving imaging scopes to get right. The Petzval correction is internal, so there is no flattener to buy or space, and the working distance is a 41–61 mm range rather than a single target. Thread the camera to the M48 output, focus, and the corners come with it. If your train includes a filter drawer or off-axis guider, send us the parts list and we will confirm the stack lands in range before you order.

Do I need a field flattener?

No. The four-element Petzval design corrects the field internally, and Starfield Optics does not offer or require a flattener for this model.

Will it cover my full-frame camera?

Yes — the corrected image circle is 44 mm, which takes in the 43.3 mm diagonal of a full-frame sensor. APS-C and the smaller cooled astronomy sensors sit well inside it.

Can I use it visually with an eyepiece?

Starfield Optics does not intend the Gear series quads for visual observing. If visual is what you are after, the Starfield ED doublets are the range built for it, and we are happy to talk through the difference.

What cameras and threads does it take?

The telescope-side output is M48 male, reached through a CAA with a female M54 thread and the included M54-to-M48 adapter. Cooled astronomy cameras from the usual makers, and DSLR or mirrorless bodies on a T-adapter, all connect from there.

What else do I need to start imaging?

A tracking mount, a camera with the right spacer for its backfocus, and power. Guiding, filters and dew control are the usual next additions rather than requirements on night one.

How is it different from the Gear60Q?

The Gear70Q steps the aperture up from 60 mm to 70 mm and the focal length from 300 mm to 350 mm, both at f/5. The extra aperture gathers more light for the same exposure, and the longer focal length trades a little field width for image scale. Both share the quad Petzval layout and the M48 imaging interface.

When is it not the right choice?

For visual observing, for planetary and lunar high-resolution work, and for small targets that want a long focal length. For wide-field deep-sky imaging on any sensor up to full frame, it is squarely in its element.

Bottom Line

In short: a 70 mm f/5 quad Petzval astrograph at 350 mm focal length, with a 44 mm flat field that covers full frame and no flattener to buy or space. It connects at M48 with a generous 41–61 mm working distance, rides on a Vixen dovetail, and travels in a fitted case with the focus motor left in place — a wide-field imaging scope that asks for a tracking mount, a camera, and very little else.