Many astro-imagers already have a premium focuser being used on another scope that they would like to use for imaging, or they have a preference for one particular focuser manufacturer over another.
Rather than pre-installing a focuser of Astro-Tech’s choosing, and to give you the most flexibility in choosing your own focuser for imaging, the 10” carbon fiber tube Astro-Tech #AT10RCF, and the 12” Astro-Tech AT12RC, are provided as optical tubes only, without focuser. This allows you to choose your own focuser, depending on your brand preference.
In addition, when using a base model Astro-Tech #AT10RC metal tube 10" Ritchey-Chrétien astrograph, the weight of very heavy equipment trains (camera, plus filter wheel, plus temperature-compensated electric focuser, etc.) may cause even the scope’s standard equipment linear Crayford focuser drawtube to tilt slightly when fully extended, affecting the focus.
In such cases, a highly recommended optional focuser that you may already have is the Feather Touch 3” #FTF3015B-A rack and pinion focuser from Starlight Instruments. It provides a more rigid imaging equipment connection and premium focusing precision and ease. However, the standard #FTF3015B-A comes with a 109mm threaded collar for attachment to a refractor, however, which will have to be replaced with this 117mm x 1mm pitch Feather Touch adapter to connect it to the 10” and 12” Astro-Tech R-Cs. This #M117x1 adapter ring threads onto the rear cell of the 10” and 12” Astro-Tech R-Cs. The #FTF3015B-A focuser (without its 109mm adapter) in turn slips into this #M117x1 adapter and is held in place by three large brass Delrin-tipped retaining knobs.
Only focusers with a maximum 1.5” drawtube travel, such as the Feather Touch #FTF3015B-A, and this adapter, are recommended for use with the Astro-Tech 10” and 12” Ritchey-Chrétiens. For brands of focusers other than Feather Touch, such as MoonLite, contact the focuser manufacturer for an adapter to fit the 117mm x 1mm port on the rear of the scope.
If you don’t already have the Feather Touch #FTF3015B-A focuser, it and this 117mm adapter are available in a package (#FT-3015) at a price that saves you over the cost of buying the focuser and adapter separately.