{"product_id":"william-optics-minicat-51-wifd","title":"William Optics MiniCat 51 WIFD f\/3.5","description":"\u003cul class=\"DAV-feature-list\"\u003e\n\u003cli\u003e51mm Aperture Diameter\u003c\/li\u003e\n\u003cli\u003e178mm Focal Length\u003c\/li\u003e\n\u003cli\u003ef\/3.5 Focal Ratio\u003c\/li\u003e\n\u003cli\u003e6-Element Petzval Optical Design\u003c\/li\u003e\n\u003cli\u003e43.2mm Full-Frame Image Circle\u003c\/li\u003e\n\u003cli\u003eWIFD Rack \u0026amp; Pinion Focuser\u003c\/li\u003e\n\u003cli\u003e1.67 kg OTA Weight\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003c!-- more --\u003e\n\u003cul class=\"tabs\"\u003e\n\u003cli class=\"active\"\u003eDescription\u003c\/li\u003e\n\u003cli\u003eFAQ\u003c\/li\u003e\n\u003cli\u003eSpecifications\u003c\/li\u003e\n\u003cli\u003eIn the Box\u003c\/li\u003e\n\u003cli\u003eWarranty\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003cul class=\"tabs-content\"\u003e\n\u003cli class=\"active\"\u003e\n\u003cdiv\u003e\n\u003cdiv class=\"DAV-bg-light\"\u003e\n\u003cdiv class=\"DAV-section-center\"\u003e\n\u003ch2\u003eWilliam Optics MiniCat 51 WIFD f\/3.5 Astrograph\u003c\/h2\u003e\n\u003cp\u003eThe William Optics MiniCat 51 WIFD combines an extremely fast f\/3.5 focal ratio with a 178mm focal length in a 6-element Petzval design engineered for wide-field astrophotography. Its optical train, featuring two Super ED glass elements, produces a flat 43.2mm image circle that fully illuminates full-frame sensors without requiring an additional flattener. Weighing just 1.67 kg, the MiniCat 51 delivers a portable, high-speed imaging platform ready for any location.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-bg-light\"\u003e\n\u003cdiv class=\"DAV-section\"\u003e\n\u003ch3\u003e6-Element f\/3.5 Petzval Optics: A 43.2mm Flat Field\u003c\/h3\u003e\n\u003cp\u003eThe MiniCat 51's optical system is built for one purpose: capturing immense swaths of the night sky with exceptional color correction and sharpness. The 6-element Petzval layout corrects for field curvature internally, meaning you get pinpoint stars across a 43.2mm image circle without the complexity of a separate flattener. Two Super ED elements minimize chromatic aberration, ensuring clean, high-contrast images of targets like the North American Nebula (NGC 7000) or the Andromeda Galaxy (M31).\u003c\/p\u003e\n\u003cp\u003eAt an aggressive f\/3.5 focal ratio, this astrograph gathers light significantly faster than typical f\/5 or f\/6 refractors. This allows you to collect more signal in less time, reducing the demands on your mount's tracking and enabling deeper images from a single night's session.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-bg-light\"\u003e\n\u003cdiv class=\"DAV-section\"\u003e\n\u003ch3\u003ePatented WIFD Focuser: 28mm of Tilt-Free Travel\u003c\/h3\u003e\n\u003cp\u003eWilliam Optics' patented Internal Focus Design (WIFD) is a robust rack-and-pinion mechanism built to handle modern imaging payloads without flexure or tilt. The entire focusing mechanism moves internally, providing 28mm of precise travel while maintaining perfect optical alignment. This design is critical for maintaining a flat field, as it prevents the drawtube sag that can compromise edge-of-field star shapes.\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eEAF Compatible:\u003c\/strong\u003e The focuser is designed for seamless integration with the ZWO EAF and other popular electronic focusers for automated, repeatable focusing.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eFlexible Back Spacing:\u003c\/strong\u003e With a working distance of 58mm to 30mm, you have ample room to incorporate filter wheels, off-axis guiders, and other accessories into your imaging train.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eIncluded Rotator \u0026amp; Tilt Adapter:\u003c\/strong\u003e The package includes a camera angle rotator and tilt adjuster, giving you full control over framing and sensor plane alignment right out of the box.\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-bg-light\"\u003e\n\u003cdiv class=\"DAV-section\"\u003e\n\u003ch3\u003eVixen \u0026amp; Arca-Swiss Mounting: 1.67 kg for Any Mount\u003c\/h3\u003e\n\u003cp\u003eEngineered for portability, the MiniCat 51 OTA weighs a mere 1.67 kg and has a compact 210mm tube length. This makes it an ideal match for lightweight star trackers and portable GoTo mounts, allowing you to build a powerful imaging rig that travels easily. The integrated dual-spec dovetail plate provides native compatibility with both traditional Vixen-style saddles and modern Arca-Swiss tripod heads, offering maximum flexibility for mounting.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-bg-light\"\u003e\n\u003cdiv class=\"DAV-section\"\u003e\n\u003ch3\u003eMiniCat 51 vs. RedCat 51: Focal Ratio and Focuser Design\u003c\/h3\u003e\n\u003cp\u003eWhile both astrographs share a 51mm aperture, the MiniCat 51 is a distinct instrument from its sibling, the RedCat 51. The choice between them depends on your specific imaging goals.\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eRedCat 51 Advantage:\u003c\/strong\u003e The RedCat 51's 250mm focal length (f\/4.9) provides slightly more image scale for smaller deep-sky objects. Its helical focuser is simple and robust for manual focusing.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eMiniCat 51 Advantage:\u003c\/strong\u003e The MiniCat 51 is significantly faster at f\/3.5 and offers a wider 178mm focal length, making it superior for capturing enormous nebulae and multi-panel mosaics. Its WIFD rack-and-pinion focuser is built from the ground up for EAF automation and heavier camera loads, eliminating the image shift that can occur with helical focusers during autofocus routines.\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eDoes the William Optics MiniCat 51 require a field flattener?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eNo, it does not. The \u003cstrong\u003e6-element Petzval optical design\u003c\/strong\u003e provides a natively flat field across its 43.2mm image circle. This simplifies your imaging train and ensures sharp stars edge-to-edge with full-frame cameras without any additional accessories.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eWhat is the back spacing of the MiniCat 51 WIFD?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eThe MiniCat 51 has a flexible back spacing range from \u003cstrong\u003e58mm to 30mm\u003c\/strong\u003e from the M48 thread. This provides ample room to accommodate various accessories like filter drawers, off-axis guiders, and different camera sensor depths while achieving perfect focus.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eCan the MiniCat 51 be used on a portable star tracker?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eAbsolutely. With an OTA weight of just \u003cstrong\u003e1.67 kg (3.68 lbs)\u003c\/strong\u003e, the MiniCat 51 is an ideal payload for most portable star trackers and small equatorial mounts. Its light weight and compact 210mm tube length make it a perfect choice for a grab-and-go wide-field imaging setup.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eHow would the MiniCat 51 frame a large target like the Rho Ophiuchi cloud complex?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eThe MiniCat 51's \u003cstrong\u003e178mm focal length\u003c\/strong\u003e is perfectly suited for immense targets like Rho Ophiuchi or the Orion Nebula (M42) region. Paired with a full-frame camera, you can capture the entire complex, including the colorful nebulosity around Antares, in a single frame, a task impossible for longer focal length telescopes.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eIs the WIFD focuser on the MiniCat 51 suitable for automated focusing?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eYes. The WIFD is a rack-and-pinion focuser specifically designed to be compatible with the \u003cstrong\u003eZWO EAF\u003c\/strong\u003e and other popular electronic autofocuser systems. Unlike helical focusers, the WIFD moves the optics internally without rotation, preventing image shift and ensuring the precise, repeatable results needed for automated imaging sessions.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eWhat cameras can I use with the MiniCat 51?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eThe MiniCat 51 supports a wide range of cameras, including \u003cstrong\u003eFull Frame, APS-C, and Micro Four Thirds\u003c\/strong\u003e formats. It ships with a standard M48 camera adapter, and separate T-mounts are available for Canon EF\/RF, Nikon F\/Z, Sony E, Pentax K, MFT, and Fuji X systems.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003ctable class=\"DAV-specifications\"\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd\u003eLens Type\u003c\/td\u003e\n\u003ctd\u003e6-Element Petzval\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eLens Elements\u003c\/td\u003e\n\u003ctd\u003eSuper ED Glass x2\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eDiameter\u003c\/td\u003e\n\u003ctd\u003e51 mm\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eFocal Length\u003c\/td\u003e\n\u003ctd\u003e178 mm\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eFocal Ratio\u003c\/td\u003e\n\u003ctd\u003ef\/3.5\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eImage Circle\u003c\/td\u003e\n\u003ctd\u003e43.2 mm\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eFocuser\u003c\/td\u003e\n\u003ctd\u003eWIFD Rack \u0026amp; Pinion Focuser (EAF Compatible)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eFocuser Travel\u003c\/td\u003e\n\u003ctd\u003e0-28 mm\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eBack Spacing\u003c\/td\u003e\n\u003ctd\u003e58-30mm\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eFlattener Required\u003c\/td\u003e\n\u003ctd\u003eNo\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eSupported T-Mounts\u003c\/td\u003e\n\u003ctd\u003eCanon EF, RF, Nikon F, Z, Sony E, Pentax K, MFT (M4\/3), FUJI X\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eSupported Camera Formats\u003c\/td\u003e\n\u003ctd\u003eFull Frame, APS-C, M4\/3\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eDovetail Type\u003c\/td\u003e\n\u003ctd\u003eVixen \u0026amp; Arca-Swiss Dual Plate\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eTube Length\u003c\/td\u003e\n\u003ctd\u003e210 mm\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eOTA Weight\u003c\/td\u003e\n\u003ctd\u003e1.67 kg \/ 3.68 lbs\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eTotal Weight\u003c\/td\u003e\n\u003ctd\u003e2.29 kg \/ 5.05 lbs\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/tbody\u003e\n\u003c\/table\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cul class=\"DAV-grid\"\u003e\n\u003cli class=\"DAV-grid-item\"\u003e\n\u003cdiv\u003e\n\u003cp class=\"DAV-item-title\"\u003eMiniCat 51 Main Tube\u003c\/p\u003e\n\u003cp class=\"DAV-item-subtitle\"\u003e× 1\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/li\u003e\n\u003cli class=\"DAV-grid-item\"\u003e\n\u003cdiv\u003e\n\u003cp class=\"DAV-item-title\"\u003eBahtinov Mask Focus Aid Cap\u003c\/p\u003e\n\u003cp class=\"DAV-item-subtitle\"\u003e× 1\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/li\u003e\n\u003cli class=\"DAV-grid-item\"\u003e\n\u003cdiv\u003e\n\u003cp class=\"DAV-item-title\"\u003eMounting Ring \u0026amp; Handle Bar\u003c\/p\u003e\n\u003cp class=\"DAV-item-subtitle\"\u003e× 1\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/li\u003e\n\u003cli class=\"DAV-grid-item\"\u003e\n\u003cdiv\u003e\n\u003cp class=\"DAV-item-title\"\u003eDual Vixen\/Arca-Swiss Plate\u003c\/p\u003e\n\u003cp class=\"DAV-item-subtitle\"\u003e× 1\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/li\u003e\n\u003cli class=\"DAV-grid-item\"\u003e\n\u003cdiv\u003e\n\u003cp class=\"DAV-item-title\"\u003eM48 Camera Adapter\u003c\/p\u003e\n\u003cp class=\"DAV-item-subtitle\"\u003e× 1\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/li\u003e\n\u003cli class=\"DAV-grid-item\"\u003e\n\u003cdiv\u003e\n\u003cp class=\"DAV-item-title\"\u003eTilt Adjuster \u0026amp; Rotator (M54 → M48)\u003c\/p\u003e\n\u003cp class=\"DAV-item-subtitle\"\u003e× 1\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/li\u003e\n\u003cli class=\"DAV-grid-item\"\u003e\n\u003cdiv\u003e\n\u003cp class=\"DAV-item-title\"\u003eAllen Key Set\u003c\/p\u003e\n\u003cp class=\"DAV-item-subtitle\"\u003e× 1\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/li\u003e\n\u003cli class=\"DAV-grid-item\"\u003e\n\u003cdiv\u003e\n\u003cp class=\"DAV-item-title\"\u003eSoft Padded Carry Case\u003c\/p\u003e\n\u003cp class=\"DAV-item-subtitle\"\u003e× 1\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003c\/li\u003e\n\n\u003cli\u003e\n\u003ca href=\"https:\/\/davidastro.com\/pages\/william-optics-warranty-policy\" rel=\"noopener\" target=\"_blank\"\u003eWilliam Optics 2-Year Warranty\u003c\/a\u003e\n\u003c\/li\u003e\n\u003c\/ul\u003e","brand":"William Optics","offers":[{"title":"Default Title","offer_id":49149195813149,"sku":"WO-T-C-MINI-RD","price":988.0,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0753\/5280\/1565\/files\/William-Optics-MiniCat-51-1.jpg?v=1726067423","url":"https:\/\/davidastro.com\/fr-us\/products\/william-optics-minicat-51-wifd","provider":"David Astro","version":"1.0","type":"link"}