{"product_id":"farpoint-adjustable-bahtinov-mask-5-5-to-8-5-otas","title":"Farpoint Adjustable Bahtinov Focus Mask — 5.5\" to 8.5\" OTAs","description":"\u003c!--FPSEO|v1|20260522|111111111110000010--\u003e\n\u003cp style=\"margin: 1.2em 0; padding: 0.8em 1.1em; background: #f0f4f8; border-left: 4px solid #2c3e50; border-radius: 4px; font-size: 0.95em; line-height: 1.45;\"\u003e\u003cstrong\u003eNot sure this is the right mask for your telescope?\u003c\/strong\u003e Use our \u003ca href=\"\/pages\/focus-mask-finder\"\u003e\u003cstrong\u003eFocus Mask Finder\u003c\/strong\u003e\u003c\/a\u003e — match your scope to the right Standard, Tri-Bahtinov, or Hyperstar\/RASA mask.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eAdjustable Bahtinov focus mask for OTAs from 5.5\" to 8.5\" front aperture.\u003c\/strong\u003e Sets onto the front of your telescope, gives you perfect focus in seconds, and lifts off cleanly when you're done. The adjustable peg system fits any scope in this aperture range — including OTAs we don't make a custom-fit mask for. Made in our own shop in the USA — American materials, American machinery, by Americans.\u003c\/p\u003e\n\n\u003cp\u003e\u003cem\u003eFits any OTA with a front aperture diameter from 5.5\" to 8.5\" — 6\" refractors, small Newtonians, 8\" SCTs, and any scope in this size range we don't offer as a custom-fit.\u003c\/em\u003e\u003c\/p\u003e\n\n\u003ch2\u003eWhy a Farpoint adjustable Bahtinov\u003c\/h2\u003e\n\u003cul\u003e\n  \u003cli\u003e\n\u003cstrong\u003eUniversal fit, 5.5\" to 8.5\".\u003c\/strong\u003e The adjustable peg system seats securely on any OTA in this aperture range, including brands and models we don't make a custom-fit mask for.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eMade in the USA.\u003c\/strong\u003e Designed and manufactured in our own shop with American materials, American machinery, and American workmanship.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eIndestructible ABS plastic.\u003c\/strong\u003e Won't crack, warp, or shatter like aluminum or acrylic alternatives. Built to last decades.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003e15+ year track record.\u003c\/strong\u003e Farpoint has been making focus masks longer than nearly anyone in the hobby.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch2\u003eWhat's in the box\u003c\/h2\u003e\n\u003cul\u003e\n  \u003cli\u003e1× Farpoint Adjustable Bahtinov Mask\u003c\/li\u003e\n  \u003cli\u003eAdjustable peg system for 5.5\" to 8.5\" OTA range\u003c\/li\u003e\n  \u003cli\u003eInstructions for use\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch2\u003eHow a Bahtinov mask works\u003c\/h2\u003e\n\u003cp\u003ePlace the mask over the front of your telescope and aim at a fairly bright star. Take a short exposure. You'll see three diffraction spikes — two angled spikes forming an X, plus a third central spike that's offset to one side or the other when the scope is out of focus. As you adjust the focuser, the central spike moves across the X. When it lands perfectly centered and symmetrical, you've hit optimum focus. Lift the mask off and start shooting.\u003c\/p\u003e\n\n\u003cp style=\"text-align: center;\"\u003e\n  \u003cimg src=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0567\/6639\/8617\/files\/bmaskanimation.gif?v=1778193011\" alt=\"Animated GIF showing a star coming into focus through a Bahtinov mask\" width=\"256\" height=\"256\" style=\"display: block; margin: 0 auto;\"\u003e\n  \u003cbr\u003e\u003cem\u003eA star coming into focus through a Bahtinov mask\u003c\/em\u003e\n\u003c\/p\u003e\n\n\u003ch2\u003eFree software for precise focus measurement\u003c\/h2\u003e\n\u003cp\u003eIf you want machine-precise focus instead of eyeballing the spike pattern, free open-source software can analyze the diffraction image automatically:\u003c\/p\u003e\n\u003cul\u003e\n  \u003cli\u003e\n\u003cstrong\u003eBahtinov-Collimator\u003c\/strong\u003e — a Windows tool that quantifies focus error directly from your image. \u003ca href=\"https:\/\/github.com\/insertnamehere1\/Bahtinov-Collimator\" rel=\"noopener\" target=\"_blank\"\u003eAvailable on GitHub\u003c\/a\u003e.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eAPT (Astro Photography Tool)\u003c\/strong\u003e — Bahtinov mask analysis is built into APT's image-capture workflow.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003cp style=\"text-align: center;\"\u003e\n  \u003cimg src=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0567\/6639\/8617\/files\/Collimation.jpg?v=1737820356\" alt=\"Screenshot of Bahtinov-Collimator software analyzing a star image\" width=\"551\" height=\"408\" style=\"display: block; margin: 0 auto; max-width: 100%; height: auto;\"\u003e\n  \u003cbr\u003e\u003cem\u003eBahtinov-Collimator analyzing a star image for precise focus measurement\u003c\/em\u003e\n\u003c\/p\u003e\n\n\u003ch2\u003eWant collimation help too? Step up to the Adjustable Tri-Bahtinov\u003c\/h2\u003e\n\u003cp\u003eThe \u003cstrong\u003eTri-Bahtinov\u003c\/strong\u003e mask uses three different grid patterns to reveal both focus AND collimation errors in a single exposure — same adjustable peg system, more capability. \u003ca href=\"\/products\/farpoint-adjustable-tri-bahtinov-mask-5-5-to-8-5-otas\"\u003eSee the Adjustable Tri-Bahtinov for 5.5\" to 8.5\" OTAs →\u003c\/a\u003e\u003c\/p\u003e\n\n\u003ch2\u003eRelated guides\u003c\/h2\u003e\n\u003cul\u003e\n  \u003cli\u003e\n\u003ca href=\"\/pages\/focus-masks\"\u003eFocus Masks Buyer's Guide\u003c\/a\u003e — material comparison, custom-fit vs adjustable, choosing the right type\u003c\/li\u003e\n  \u003cli\u003e\n\u003ca href=\"\/pages\/telescope-collimation-guide\"\u003eTelescope Collimation Guide\u003c\/a\u003e — full walkthrough on collimating your scope\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003cp style=\"text-align: center;\"\u003e\n  \u003cimg src=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0567\/6639\/8617\/files\/DiffSpike.jpg?v=1737826264\" alt=\"Diffraction spike pattern at perfect focus through a Bahtinov mask\" style=\"display: block; margin: 0 auto; max-width: 100%; height: auto;\"\u003e\n  \u003cbr\u003e\u003cem\u003eThe unmistakable diffraction spike pattern at perfect focus\u003c\/em\u003e\n\u003c\/p\u003e","brand":"Farpoint","offers":[{"title":"Default Title","offer_id":40161496891545,"sku":"FP402","price":25.0,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0567\/6639\/8617\/products\/FP400-1-e1611108937848_a48b6be9-c180-43ec-9236-7776032d823f.jpg?v=1775145659","url":"https:\/\/farpointastro.com\/products\/farpoint-adjustable-bahtinov-mask-5-5-to-8-5-otas","provider":"FarpointAstro","version":"1.0","type":"link"}