William Optics RedCat 71 APO — image 1
William Optics

William Optics RedCat 71 APO

No longer sold

The bigger sibling to the cult-favorite RedCat 51: a 71mm f/4.9 Petzval astrograph that delivers a flat, fast, full-frame field in a jewel-like package built for grab-and-shoot wide-field imaging.

88/ 100
Polaris Score
#1 of 7 wide-field imaging refractor
See the breakdown ↓
Aperture
71mm
Focal Length
348mm
Focal Ratio
f/4.9
Mount Type
None (OTA only)
Optical Design
Petzval Astrograph
Weight
2.5 kg
Try in simulator →
No longer sold

Discontinued by the manufacturer (per Agena Astro). We keep the page for reference — see current alternatives below.

See alternatives ↓
What it's built forOpen these in the simulator →

This telescope was built for the camera.

A fast f/4.9 astrograph designed to throw a wide, flat, well-corrected field onto a sensor. It is an optical tube first — give it a tracking mount and a camera and it rewards long exposures, not eyepieces.

f/4.9 — built to imageNeeds a tracking mount
The view people remember

The Orion Nebula, wings unfolded.

The four stars of the Trapezium sit inside folded sheets of glowing gas — the closest stellar nursery to us, bright enough to show real structure even from the suburbs.

See Orion Nebula through this telescope →
01What it's good at

What it's best at — and the trade-offs.

The four-element Petzval design bakes the flattener into the tube, so stars stay round to the corners of a full-frame sensor with nothing to add
Best at
✓The four-element Petzval design bakes the flattener into the tube, so stars stay round to the corners of a full-frame sensor with nothing to add
✓348mm at f/4.9 frames large nebulae and the Milky Way beautifully while collecting light fast for short, clean exposures
✓A weight of about 2.5kg lets it ride comfortably on lightweight star trackers, so the whole rig stays truly portable
✓William Optics build quality is exceptional: a rotator, Bahtinov mask cover and locking helical focuser come as part of the package
Trade-offs
!It is a dedicated astrograph, so visual use is possible but beside the point
!348mm is short, so small targets stay small in the frame
!As an OTA it needs a tracking mount, camera and often a guide scope to produce results
!The premium build commands a premium price for the aperture
02In plain English

What These Numbers Mean

71mm · f/4.9 · 348mm FL
Aperture
71 mm
Just under three inches, gathering about 94 percent more light than the RedCat 51. That halves the integration time for the same result while keeping the same wide-field character.
Focal length
348 mm
Wide but with more scale than the RedCat 51. Large nebulae still fit an APS-C frame while smaller targets such as the Rosette or the Heart hold usable detail.
Focal ratio
f/4.9
Fast, so exposures stay short and total integration times stay reasonable even under suburban skies with a dual-band filter. Guiding demands remain light at this focal length.
Optical design
Petzval astrograph
The field flattening is built into the optical design, so full-frame corners stay clean with nothing added to the imaging train. No spacing to calculate is one less source of elongated corner stars.
Weight
2.5 kg tube
About 5.5 lb, still within star tracker limits with a light camera and easy for any small equatorial. It remains a travel-first telescope.
Mount
OTA only
No mount included. At 348 mm a tracker or entry equatorial with basic guiding is enough to get round stars, which keeps the entry cost modest.
03The Polaris Score

How it scores, and why.

88/100 · #1 of 7 wide-field imaging refractor
88/ 100
William Optics RedCat 71 APO
#1 of 7 wide-field imaging refractor
Performance
90
Ease of use
80
Portability
90
Upgrade potential
75

Polaris weighs optical capability, how easy the scope is to live with, how portable it is, and how far it takes you before you outgrow it — not list price or brand.

04Who it's for

An honest fit check.

Astrophotographers who want a portable, grab-and-shoot wide-field apo with corners handled
Buy it if you
✓Astrophotographers who want a portable, grab-and-shoot wide-field apo with corners handled
✓Imagers on star trackers and small mounts where weight is critical
✓People framing large deep-sky regions that a longer scope would crop
Look elsewhere if you
!Visual observers, since this is an imaging tube first with a narrow visual use case
!Anyone chasing small galaxies or planets that need long focal length
!Buyers who need a complete scope, since it is an OTA needing a tracking mount and camera
05Build your rig

What to buy next — and where it leads.

7 pieces of gear, ordered by what changes the view most
Recommended upgrades
No fogging on long sessions★ Top pickPegasus Astro Multi-Channel Dew Controller

Keeps the front optics dew-free across a full imaging night

Make nebulae popOptolong OIII Filter 2″

Isolates emission nebulae for high-contrast wide-field imaging under light pollution

Observe all night, no AA batteriesCelestron PowerTank Lithium

Runs the tracker, camera and dew heater away from mains power

Imaging path
Better tracking & light imagingSky-Watcher HEQ5 Pro SynScan GoTo Mount✓ Compatible

Commonly paired with this telescope

Portable astrophotographyZWO AM5N Harmonic Equatorial Mount✓ Compatible

Start capturing images of the Moon and planets

A versatile upgradeSky-Watcher Star Adventurer GTi GoTo EQ Mount Kit✓ Compatible

Commonly paired with this telescope

Start imagingZWO ASI533MC Pro

Start capturing images of the Moon and planets

Wide-field deep-sky imaging
Excellent, flat field
Lunar & planetary
Small image scale
Visual use
Possible, but an imaging tube
06The numbers

Full specifications.

6 measured and stated values
Optics
Optical DesignPetzval Astrograph
Aperture71mm
Focal Length348mm
Focal Ratiof/4.9
Mount & drive
Mount TypeNone (OTA only)
Physical
Weight2.5 kg
07Alternatives

For a different goal, start here.

3 alternatives, each mapped to the goal it wins at
Smaller and cheaper

William Optics RedCat 51

The 51mm original for the widest fields and the lightest, most travel-friendly rig

→
Similar reach

Askar FRA400C Quintuplet APO Refractor

A 72mm f/5.6 quintuplet at a similar focal length if you want more elements for less money

→
Budget option

Sky-Watcher Evostar 72ED

A 72mm ED doublet plus flattener if you want to spend far less and do not mind matching optics

→
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Orion SkyQuest XT12 Dobsonian
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SVBony SV555 54mm f/4.5 APO
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