{"id":33894,"date":"2025-11-15T14:00:58","date_gmt":"2025-11-15T13:00:58","guid":{"rendered":"https:\/\/www.telescoop.nl\/?post_type=product&p=33894"},"modified":"2026-03-04T16:59:29","modified_gmt":"2026-03-04T15:59:29","slug":"william-optics-zenithstar-81-559-apo-wifd-red-ota","status":"publish","type":"product","link":"https:\/\/staging.telescoop.nl\/en\/william-optics-zenithstar-81-559-apo-wifd-red-ota\/","title":{"rendered":"William Optics ZenithStar 81\/559 APO WIFD Red OTA"},"content":{"rendered":"

William Optics AP 81\/559 81 - Compact power for sharp images<\/strong><\/h3>\n\n\n\n

The William Optics AP 81\/559 81<\/strong> is a lightweight and compact apochromatic refractor. It is ideal for astrophotography and wide-angle shots of star fields. You easily mount it on a lightweight camera mount such as the Star Adventurer or Star Tracker. Within minutes you are ready to photograph or observe.<\/p>\n\n\n\n

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\"William<\/figure>\n<\/figure>\n\n\n\n

Razor-sharp and color-corrected<\/strong><\/h3>\n\n\n\n

The doublet lens with FPL-53 ED glass provides bright and natural colors. Together with an optional flattener, stars and objects remain sharp to the corners. This allows you to take beautiful shots of nebulae, stars and the Moon without distortion.<\/p>\n\n\n\n

Internal focusing system (WIFD)<\/strong><\/h3>\n\n\n\n

The Internal Focus Design (WIFD) lets you focus accurately without turning on the outside. You can even use heavy, cooled cameras without vignetting. The integrated scale shows you exactly where the focus is. Compatible with the ZWO EAF for automatic focusing.<\/p>\n\n\n\n

\n
\"William<\/figure>\n<\/figure>\n\n\n\n

Compact and travel-friendly<\/strong><\/h3>\n\n\n\n

Despite the 81 mm aperture, the telescope is light and compact. You can easily take it with you as hand luggage. Aluminum tube, sturdy tube rings and a practical carrying handle ensure stability and easy mounting of a viewfinder or tracking scope.<\/p>\n\n\n\n

Versatile and adaptable<\/strong><\/h3>\n\n\n\n

The ZS81 is suitable for astrophotography, planets and the Moon. Thanks to William Optics' extensive accessory system, you can expand it as you wish. You get excellent optics, ease of use and a competitive price.<\/p>\n\n\n\n

Specifications<\/strong><\/h3>\n\n\n\n

Optics<\/strong><\/h4>\n\n\n\n
Feature<\/th>Description<\/th><\/tr><\/thead>
Type<\/td>Refractor<\/td><\/tr>
Design<\/td>Apochromat<\/td><\/tr>
Lens Design<\/td>Doublet<\/td><\/tr>
Aperture (mm)<\/td>81<\/td><\/tr>
Focal length (mm)<\/td>559<\/td><\/tr>
Aperture ratio (f\/)<\/td>6,9<\/td><\/tr>
Resolution<\/td>1,70\u2033<\/td><\/tr>
Limit value (mag)<\/td>11,3<\/td><\/tr>
Light output<\/td>130\u00d7<\/td><\/tr>
Max. useful magnification<\/td>162\u00d7<\/td><\/tr>
Corrected field of view (mm)<\/td>45<\/td><\/tr>
Tube length (mm)<\/td>607<\/td><\/tr>
Transport length (mm)<\/td>526<\/td><\/tr>
Tube weight (kg)<\/td>3,5<\/td><\/tr>
Glass material<\/td>OHARA FPL-53<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n

Focuser<\/strong><\/h4>\n\n\n\n
Feature<\/th>Description<\/th><\/tr><\/thead>
Design<\/td>Internal (WIFD)<\/td><\/tr>
Ocular connection<\/td>2\u2033<\/td><\/tr>
Reduction<\/td>1:10 finesse<\/td><\/tr>
Camera connection<\/td>M63<\/td><\/tr>
Free opening (mm)<\/td>64<\/td><\/tr>
Rotatable<\/td>Yes<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n

Mount<\/strong><\/h4>\n\n\n\n
Feature<\/th>Description<\/th><\/tr><\/thead>
Design<\/td>OTA<\/td><\/tr>
Type of mount<\/td>Without mount<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n

Included accessories<\/strong><\/h4>\n\n\n\n
Section<\/th>Description<\/th><\/tr><\/thead>
Handle<\/td>Yes<\/td><\/tr>
Transport bag<\/td>Yes<\/td><\/tr>
Tube Rings<\/td>Yes<\/td><\/tr>
Dovetail<\/td>Arca-Swiss & Vixen-Style<\/td><\/tr>
Dew cap<\/td>Yes<\/td><\/tr>
Focusing aid<\/td>Bahtinov Mask<\/td><\/tr>
Miscellaneous<\/td>Adapters M92\/M63<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n

General<\/strong><\/h4>\n\n\n\n
Feature<\/th>Description<\/th><\/tr><\/thead>
Series<\/td>ZenithStar<\/td><\/tr>
Color<\/td>Red<\/td><\/tr>
Application<\/td>Astrophotography, Moon & Planets, Nebulae & galaxies<\/td><\/tr>
Recommended for<\/td>Advanced<\/td><\/tr>
Observatory use<\/td>No<\/td><\/tr><\/tbody><\/table><\/figure>","protected":false},"excerpt":{"rendered":"

William Optics AP 81\/559 81 comes with a WIFD internal focuser, tube rings, Arca-Swiss & Vixen-style dovetail, handle, Bahtinov mask, adapters and a soft carrying case. \u00a0<\/p>","protected":false},"featured_media":97382,"comment_status":"open","ping_status":"closed","template":"","meta":{"_acf_changed":false},"product_brand":[643],"product_cat":[51,567],"product_tag":[],"class_list":["post-33894","product","type-product","status-publish","has-post-thumbnail","product_brand-william-optics","product_cat-telescopen","product_cat-refractors","first","instock","taxable","shipping-taxable","purchasable","product-type-simple"],"bundled_by":[],"bundle_stock_status":"instock","bundle_stock_quantity":null,"bundle_virtual":false,"bundle_layout":"","bundle_add_to_cart_form_location":"","bundle_editable_in_cart":false,"bundle_sold_individually_context":"","bundle_item_grouping":"","bundle_min_size":"","bundle_max_size":"","bundle_price":[],"bundled_items":[],"bundle_sell_ids":[],"acf":[],"jetpack_sharing_enabled":true,"jetpack-related-posts":[{"id":33886,"url":"https:\/\/staging.telescoop.nl\/en\/william-optics-zenithstar-81-559-apo-wifd-goud-ota\/","url_meta":{"origin":33894,"position":0},"title":"William 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