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William Ultra-Cat 131 Petzval Apochromat 131/648 mm

Name: William Ultra-Cat 131 Petzval Apochromat 131/648 mm
Brand: William Optics
SKU: CAT130
Price: 6608 EUR

The Ultra-Cat 131 is a high-performance 131 mm apochromatic refractor, designed for astrophotographers who demand exceptional clarity and true color accuracy.

Focal ratio f/4.9

Optical design according to Petzval with integrated corrector (five elements in total)

Temperature-stable lens cell

Clear and sharp image even when using a medium format sensor

William Optics Internal Focus Design (WIFD)

Rotator and tilt flange included

Patented multifunctional handle

Connection on camera side: M68, M54, M48

Bahtinov mask included

Manufacturer: William Optics

Product number: CAT130

EUR 6.608,00

incl. 19 % VAT (DE)

The VAT indicated refers to that applicable in Germany. After logging in, the VAT amount is adjusted to the applicable VAT of the stored delivery country. Therefore, the final price may vary accordingly.

excl. 13.95 € shipping costs (DE)

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Product expected to be available from 20.06.2026

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William Ultra-Cat 131 Petzval Apochromat 131/648 mm

The Ultra-Cat 131 is a high-performance 131 mm apochromatic refractor, designed for astrophotographers who demand exceptional clarity and true color accuracy.

Focal ratio f/4.9

Optical design according to Petzval with integrated corrector (five elements in total)

Temperature-stable lens cell

Clear and sharp image even when using a medium format sensor

William Optics Internal Focus Design (WIFD)

Rotator and tilt flange included

Patented multifunctional handle

Connection on camera side: M68, M54, M48

Bahtinov mask included

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Technical data..
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William Ultra-Cat 131 Petzval Apochromat 131/648 mm

The apochromatic 131 mm refractor was developed for demanding astrophotographers. It offers 5-element Petzval optics with special low-dispersion ED optical glass and a fast focal ratio of f/4.9. Together with the focal length of 648 mm, this makes it the ideal universal telescope.

The UltraCat astrograph at a glance

The advanced 5-element Petzval design eliminates field curvature and delivers sharp images without additional flattener.

60 mm large Image Circle: Fully supports Medium Format and Full Frame cameras, APS-C and M4/3 sensors.

Fast f/4.8 Optics: Superior light-gathering capability, enabling deep-sky imaging with shorter exposure times.

The patented WIFD focuser (WIFD: William Internal Focuser Design) is integrated into the tube. This special design allows precise focusing and avoids tilting, even with heavy cameras. The focuser is EAF-compatible.

Temperature-stable lens cells minimize thermal expansion and contraction and ensure perfect optical alignment in any environment.

On the camera side, the tube is equipped with a rotator and a tilt flange. The former allows the camera to be rotated for perfect alignment of the sensor to the subject, the latter allows the camera sensor to be aligned exactly parallel to the image plane, thus avoiding build errors.

Patented Bahtinov Mask for Focusing: Built-in focusing aid ensures pinpoint star sharpness with ease.

Premium Build & Ergonomic Design: Lightweight yet robust construction with a sleek anodized finish.

Patented handle bar design for enhanced portability and ease of use.

The patented handle allows stable mounting of accessories.

Lens Type:	5-Element Advanced Petzval, triplet and two single elements
Lens Elements:	Super ED Glass x2, ED Glass x1, Lanthanum Glass x1, X-Element x1
Focal Length:	648 mm
Aperture:	131 mm
Focal Ratio:	f/4.9
Image Circle:	60 mm
Focuser:	WIFD R&P focuser, compatible with EAF
Focuser Travel:	20 mm
Adapter Included:	Sensor Tilt Xterminator and Rotator as well as camera adapters to M68, M54 and M48
T-Mount Support:	Canon EF and RF, Nikon F and Z, Sony E, Pentax K, MFT (M4/3), FUJI X
Camera Format:	Medium format (44 mm x 33 mm), full frame, APS-C, M4/3
Mount Connection:	Losmandy-style dovetail plate
Dew shield diameter:	186 mm
Tube Length:	650.0 mm - 785.5 mm
OTA Weight:	9.95 kg / 21.94 lbs

Tube with tube rings and dovetail bar

Manufacturer / Importeur:	Teleskop-Service Ransburg GmnH
Street:	Von-Myra-Str. 8
ZIP / City:	85599 Parsdorf
Country:	Germany
Telefon number:	+49 89 99228750
Email:	info@teleskop-service.de
Website:	www.teleskop-express.de