Tele Vue 102iis - Manual (Page 7)

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2. Prime focus with SBIG STL series cameras
3. Prime focus with 35mm format SLRs in cameras with 55mm chip to T-Ring distance.
1. Prime focus for up to 10mm diagonal chips in
cameras with 55mm chip to T-Ring distance.
specifications are changed to 704mm and f/6.9 respectively with the use of the 0.8x field flattener/
focal reducer is used. It is the focal length of the telescope in combination with the diagonal dimension
of the CCD chip or film frame that will determine the amount of field your photograph will cover. The
shorter the focal length or larger the diagonal dimension, the greater the field that will be recorded.
The recommendations below and in the diagrams are specifically for SLR (digital or film) and the
SBIG 11000 cameras. If you have a different camera, you will need to determine the spacer necessary
to achieve the optimal distance from the end of the T-ring adapter to the your CCD chip. This spacer
will be added in front of the T-ring adapter.
To start, you need to know the distance from the chip to the faceplate of the camera. This should be
specified in the camera’s documentation; call your camera’s manufacturer if it is not. The equation is simply
2.2” - Chip to faceplate distance = additional spacer length required. There is enough tolerance in this value
that using the Imaging System spacers which bring you as close as possible will work fine.
Since there are tolerances in all manufactured parts, it may be necessary to vary the spacing
slightly from the nominally calculated value. Should your star images in the the four corners look slightly
elongated, try using the next smallest increment of threaded spacer with either the 0.040” (TLF-0040),
2mm (TLG-0080), or both inbetween the threaded spacers to fine tune the image.