{"id":2942,"date":"2020-06-22T08:10:11","date_gmt":"2020-06-22T12:10:11","guid":{"rendered":"http:\/\/www.apex-telescope.org\/ns\/?page_id=2942"},"modified":"2025-07-10T10:46:50","modified_gmt":"2025-07-10T14:46:50","slug":"observing-time-calculators","status":"publish","type":"page","link":"https:\/\/www.apex-telescope.org\/ns\/observing\/observing-time-calculators\/","title":{"rendered":"Observing time calculators"},"content":{"rendered":"\n
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If you would like to apply for APEX time<\/a> you need to estimate how much you need to complete your project. For that you can use our observing time calculators (OTC). They consider the noise performance of the instrumentation<\/a> in place as well as other relevant parameters like the atmospheric transmission for a given source elevation and conditions of precipitable water vapour. They also assume some overhead time used for pointing, calibrations and antenna slewing. These overheads are computed considering statistics on real observations at the telescope.<\/p>\n<\/div>\n\n\n\n

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There are two modes of operation. You can enter the noise level you want to achieve your scientific goal and then calculate the time you need. But you can also specify some time on source and get the noise you will get.<\/p>\n\n\n\n

Make sure you choose realistic parameters<\/strong> for your estimate. Being too optimistic or too pessimistic can reduce your chances to get your proposal approved by the Telescope Allocation Committee. Some bad examples are for instance assuming that your target source is always at its maximum elevation on sky, or choosing pwv conditions not suited for the frequency that you will be observing.<\/p>\n\n\n\n

Make sure that you refer in your proposal to the version of the observing time calculator that you used for your estimates. You can find this information in each of the corresponding pages, on the upper part.<\/p>\n\n\n\n

Remember that in order to design your observing strategy, you can use some of the tools we have prepared, like the on-the-fly simulator<\/a>, or the instrument setup tool<\/a>, to optimise your tuning frequency as a function of instrument and atmospheric transmission.<\/p>\n\n\n\n

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Heterodyne instruments<\/h3>\n\n\n\n

Depending on the observing strategy you will be using, you must choose the time estimator for ON\/OFF observations (valid for beam- and position-switching observations), or for on-the-fly mapping. <\/p>\n\n\n\n

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