Feather Touch 90mm x 1mm pitch adapter to put Feather Touch Focuser on Astro-Tech AT8RC astrograph

When using an Astro-Tech #AT8RC 8" Ritchey-Chrétien astrograph, the weight of very heavy equipment trains (camera, plus filter wheel, plus temperature-compensated electric focuser, etc.) may cause the standard equipment Crayford focuser drawtube to tilt slightly when fully extended, affecting the focus.

In such rare cases, the standard Crayford focuser can be user-replaced by an optional Feather Touch #FT-1.5BC 2" focuser from Starlight Instruments for a more rigid imaging equipment connection. This 90mm x 1mm pitch Feather Touch adapter is needed to connect the #FT-1.5BC to the #AT8RC. The adapter threads onto the 90mm rear cell thread of the #AT8RC in place of the standard Crayford focuser. The Feather Touch #FT-1.5BC focuser slips into the adapter and is held in place by three hex-head setscrews in the adapter.

Only focusers with a maximum 1.5" drawtube travel, such as the Feather Touch #FT-1.5BC, are recommended with the Astro-Tech #AT8RC 8" Ritchey-Chrétien.

This adapter and the Feather Touch #FT-1.5BC focuser can also be used with the 6" #AT6RC Ritchey-Chrétien astrograph. However, the #AT6RC is primarily designed for use with lighter weight webcam/Deep Sky Imager-type camera/DSLR imagers, not with heavy long equipment train CCD imaging setups. These lighter weight imaging systems are unlikely to cause any focuser issues. The addition of a Feather Touch focuser and this adapter will add little to the performance of the #AT6RC, although significantly to the cost (about half the cost of the #AT6RC itself).