Exposure Calculator

The exposure time calculator is a Java 1.0 applet.

If you have any problems, please contact Phase 1 Support with your browser and OS combination and any error messages you encounter.

To use the calculator, simply enter the apparent magnitude of your target, along with the desired signal-to-noise ratio. Then select the filter and binning. you require and press the "Do Calculation button". In general you should use 2x2 binning for RATCam and IO.

The minimum exposure time is set to one second. We have not yet determined the minimum reliable exposure time for the shutter to allow 1% photometry, however it could be as much as 10 seconds.

Any risk of saturation is indicated by a minus sign preceding the calculated exposure time. This can occur with bright objects (where there is little that can be done except possibly defocusing or not binning), or faint objects where the SNR requested is too high (where splitting the exposure into multiple readouts will provide a solution).

This calculator covers only RATCam, and IO:O. For RISE, use r' band in the calculator. For details of other instruments' sensitivity, see their respective instrument pages.