AC­CU­RATE FIL­TER WHEEL

Sky at Night Magazine - - FIRST LIGHT -

The Atik One 6.0 has an in­te­grated fil­ter wheel with a carousel mounted on ax­ial nee­dle roller bear­ings. In­cor­po­rat­ing a fil­ter wheel into a CCD cam­era has some use­ful ad­van­tages. Ex­ter­nal fil­ter wheels add con­sid­er­ably to the back­fo­cus of the sys­tem, caus­ing spacing dif­fi­cul­ties when also us­ing fo­cal re­duc­ers, field flat­ten­ers or coma cor­rec­tors. The in­te­grated fil­ter wheel here only adds 14mm to the depth of the cam­era, giv­ing a to­tal back­fo­cus of 27mm. As most cor­rec­tors are de­signed for use with DSLR cam­eras – which have a to­tal back­fo­cus of nom­i­nally 55mm in­clud­ing their adap­tor rings – this leaves a gen­er­ous 28mm for the in­ser­tion of an off-axis guider as well, if re­quired. It also means you need fewer ca­bles, as the power and USB leads for the fil­ter wheel are shared with the cam­era.

The fil­ter wheel has five 1.25-inch slots and it is vi­tal that th­ese are cen­tred ac­cu­rately in front of the sen­sor as each fil­ter is cho­sen in turn. Dur­ing our bench testing, we found that the fil­ters were very ac­cu­rately po­si­tioned and re­peata­bil­ity was ex­cel­lent.

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