{"product_id":"takahashi-toa-150b-0-99x-toa-645-field-flattener","title":"Takahashi TOA-150B 0.99x TOA-645 Field Flattener","description":"\u003ch3\u003e\u003cstrong\u003eProduct Overview\u003c\/strong\u003e\u003c\/h3\u003e\u003cp\u003eThe TOA-645 Field Flattener 150 Set is Takahashi's dedicated flattener kit for the TOA-150B refractor, built for high-resolution medium-format imaging. It holds the telescope's own 1100mm f\/7.3 essentially unchanged — 1085mm at f\/7.2 — while flattening the field across a Φ60mm image circle, large enough for today's full-frame and medium-format sensors.\u003c\/p\u003e\u003ch3\u003e\u003cstrong\u003eWho It's For\u003c\/strong\u003e\u003c\/h3\u003e\u003cp\u003eThis flattener suits TOA-150B owners shooting with large-format cameras — full-frame CMOS or medium-format backs — who need corner-to-corner sharpness across a wide sensor rather than a reduced focal length. Takahashi's own figures put the RMS spot diameter at 1 micron on-axis and 5 microns at the full 60mm diameter.\u003c\/p\u003e\u003ch3\u003e\u003cstrong\u003eKey Features \u0026amp; Design\u003c\/strong\u003e\u003c\/h3\u003e\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eTwo-element flattener:\u003c\/strong\u003e two fully multi-coated elements in two groups, purpose-built for digital sensors rather than adapted from a film-era design.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eΦ60mm corrected image circle:\u003c\/strong\u003e covers full-frame and medium-format sensors with minimal fall-off.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eNear-native focal length:\u003c\/strong\u003e 1085mm at f\/7.2 keeps the TOA-150B's own field of view essentially intact.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eBundled CA35 (50.8) ring:\u003c\/strong\u003e included in this kit, matched to the TOA-150B's mount so the flattener installs as a complete system.\u003c\/li\u003e\n\u003c\/ul\u003e\u003ch3\u003e\u003cstrong\u003eOptical \/ Mechanical Design\u003c\/strong\u003e\u003c\/h3\u003e\u003cp\u003eThe flattener threads to the TOA-150B's 50.8 Adapter on an M72x1 male-to-female interface and outputs to the included CA35 ring on an M54x0.75 female thread. Total kit weight is 330g. The corrected back focus is 56.2mm measured from the CA35 ring — the figure to build the rest of your imaging train from. See the \u003ca href=\"\/pages\/takahashi-back-focus-guide\"\u003eTakahashi Back Focus Guide\u003c\/a\u003e for the full spacing chain.\u003c\/p\u003e\u003ch3\u003e\u003cstrong\u003eRecommended Uses\u003c\/strong\u003e\u003c\/h3\u003e\u003cp\u003eHigh-resolution deep-sky imaging with full-frame or medium-format cameras on the TOA-150B; wide-field mosaicless framing of large nebulae and galaxy fields where the full Φ60mm circle is put to use; observatory and long-exposure narrowband work where field flatness across the whole sensor matters.\u003c\/p\u003e\u003ch3\u003e\u003cstrong\u003eCompatibility and Accessory Notes\u003c\/strong\u003e\u003c\/h3\u003e\u003ctable\u003e\n\u003ctr\u003e\n\u003cth\u003eTelescope\u003c\/th\u003e\n\u003cth\u003eResulting focal length\u003c\/th\u003e\n\u003cth\u003eResulting focal ratio\u003c\/th\u003e\n\u003cth\u003eImage circle\u003c\/th\u003e\n\u003cth\u003eBack focus\u003c\/th\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eTOA-150B (this kit, TKA32587S)\u003c\/td\u003e\n\u003ctd\u003e1085mm\u003c\/td\u003e\n\u003ctd\u003ef\/7.2\u003c\/td\u003e\n\u003ctd\u003eΦ60mm\u003c\/td\u003e\n\u003ctd\u003e56.2mm\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eTOA-130NS \/ TOA-130NFB\u003c\/td\u003e\n\u003ctd\u003e990mm\u003c\/td\u003e\n\u003ctd\u003ef\/7.6\u003c\/td\u003e\n\u003ctd\u003eΦ60mm\u003c\/td\u003e\n\u003ctd\u003e56.2mm\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/table\u003e\u003cp\u003eTOA-130NS and TOA-130NFB owners use the sibling kit, the TOA-645 Flattener 130 Set (TKA31587S), which bundles the same flattener with a CA Ring 130 sized for that telescope's mount instead of this kit's CA35 ring — we stock this listing for the TOA-150B specifically. The optical element itself is common to both kits.\u003c\/p\u003e\u003ch3\u003e\u003cstrong\u003eGood to Know Before You Order\u003c\/strong\u003e\u003c\/h3\u003e\u003cp\u003e\u003cstrong\u003eSold as a complete kit:\u003c\/strong\u003e the CA35 ring is bundled with this flattener, so there's nothing separate to source to reach the 56.2mm back focus figure.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eBuilt for the TOA-150B:\u003c\/strong\u003e if you own a TOA-130NS or TOA-130NFB instead, the matching kit is the TOA-645 Flattener 130 Set — get in touch and we'll point you to the right one.\u003c\/p\u003e\u003ch3\u003e\u003cstrong\u003eFrequently Asked Questions\u003c\/strong\u003e\u003c\/h3\u003e\u003cp\u003e\u003cstrong\u003eIs it difficult to set up?\u003c\/strong\u003e\u003c\/p\u003e\u003cp\u003eNo — it threads onto the TOA-150B's 50.8 Adapter and outputs directly to the included CA35 ring, which sets the 56.2mm back focus for you.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eWhat is it best used for?\u003c\/strong\u003e\u003c\/p\u003e\u003cp\u003eHigh-resolution astrophotography on the TOA-150B with full-frame or medium-format sensors, where a flat Φ60mm image circle matters more than a shorter focal length.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eDoes it reduce the focal length?\u003c\/strong\u003e\u003c\/p\u003e\u003cp\u003eBarely — at 0.99x it holds the TOA-150B close to its native 1100mm f\/7.3, landing at 1085mm f\/7.2. It flattens the field rather than speeding up the system.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eWhat's the difference between this and the TOA-35 Reducer?\u003c\/strong\u003e\u003c\/p\u003e\u003cp\u003eThis flattener keeps the focal length essentially native while widening the corrected circle to Φ60mm. The TOA-35 Reducer instead cuts the focal length to f\/5.2 for a faster, narrower-circle system — the two serve different imaging goals on the same telescope.\u003c\/p\u003e\u003ch3\u003e\u003cstrong\u003eBottom Line\u003c\/strong\u003e\u003c\/h3\u003e\u003cp\u003eA complete TOA-150B flattener kit that holds the telescope near its native 1100mm focal length at f\/7.2 while flattening a Φ60mm image circle for full-frame and medium-format imaging, with the matched CA35 ring included.\u003c\/p\u003e","brand":"Takahashi","offers":[{"title":"Default Title","offer_id":54047109415023,"sku":"TAK-TKA32587S","price":264.55,"currency_code":"CAD","in_stock":false}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/files\/tka32587s-1_3.jpg?v=1786913942","url":"https:\/\/ontariotelescope.com\/products\/takahashi-toa-150b-0-99x-toa-645-field-flattener","provider":"Ontario Telescope and Accessories","version":"1.0","type":"link"}