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  Prime focus CCD imaging at f/3.3

At least two observers are needed for a prime focus CCD run at f/3.3, since one person must ride in the cage to change filters and acquire guide stars. With the doublet corrector, the scale is 16.4"/mm, giving a pixel size of 0.391"/pixel with the TEK CCD (6.67' field of view, or FOV).

Both the triplet corrector and the doublet corrector are available for CCD imaging (see Table 7.1), however unless you are bringing a CCD larger than 92mm diagonally, there is no need for the larger field of the doublet.

The rest of the AAO's CCD's can be used at f/3.3 (RCA: 0.49"/pixel , FOV=4.1'x2.6'; GEC: 0.36"/pixel, FOV=3.4'x2.3'; Thomson:  0.310"/pixel, FOV=5.28'), however they offer no advantages over the TEK, being either smaller, or having poorer quantun efficiency.

The CCD filter wheels are rotated manually. Three wheels are available:

  1. A six position wheel &endash; holds up to six filters,  either 50mm square or 2.25 inch diameter, and up to 11mm thick. This is the standard wheel used with the standard set of UBVRI broad-band filters.
  2. A three position wheel &endash; holds up to three filters, up to 75mm in diameter, and up to 11mm thick.
  3. A three position wheel &endash; holds up to three filters, up to 83mm in diameter, and up to 11mm thick.

A blank slide is also available for holding a single filter, which can be up to 160mm in diameter. It is possible to change quickly between the blank slide, and one of the filter wheels &endash; but not between two wheels. Smaller filters will need specific adaptors. The  minimum diameter is ??mm to avoid vignetting the TEK chip

Exposure times can be estimated from the typical count rates given in Appendix B. As a guide, a five minute exposure with the TEK CCD in 1.5"  seeing reaches a limiting magnitude (5 sigma detection) of B=25.0, V=24.4,  R=24.1, I=22.9

The AAO CCD Imaging Manual provides many more details on Prime Focus imaging.



This Page Last updated: Mar 5, 1996, by Chris Tinney.