As of this writing there are separate HTML forms for point sources, extended sources, point source with background light, and extended targets with background light. Examples of completed HTML forms and results are shown in Sample SNR Calculations . Note that clicking on any colored text on the HTML form will give a description of that item. YES, and warnings about saturation, if appropriate.
Results are typically accurate to a few percent.
While observers should familiarize themselves with the material below, most will find the ETC program faster and easier to use for actual calculations.