Astronomy calculators

Enter your latitude, target position, camera frame size, and blur tolerance to estimate the maximum sub-exposure before alt-az field rotation smears the sensor corner.

Enter your final focal length, focal ratio, sensor size, and filter spacing to estimate the clear aperture needed before a filter clips the converging light cone.

Enter your telescope, camera, and seeing conditions to see the image scale, sampling status, field of view, and focal-length range that puts the setup near 2 to 3 samples per limiting detail.

Use a measured test frame or a known electron rate to size sub-exposures that keep camera read noise small without ignoring tracking and full-well limits.

Enter the labeled factor and rated spacing for an ordinary Barlow lens, then add or remove spacing to estimate the real magnification. The calculator also works backward from a target factor to the extension you would need.

Enter the recorded sensor dimensions, resolution, lens, and target position to estimate a fixed-tripod exposure that limits star movement to your chosen number of pixels. The result also shows why the 500 and NPF rules can be more generous.

Enter the primary mirror, focal length, secondary-to-focal-plane distance, and target field to size a Newtonian diagonal and check a candidate secondary.

Time a star drifting across your eyepiece field, enter its declination, and get a measured true field rather than an estimate from catalog specifications. Three timings also show whether the result is repeatable enough to trust.

Enter the telescope, eyepiece, and observing conditions to estimate the faintest star you can detect. The result also searches practical modeled magnifications to suggest an eyepiece focal length for the deepest stellar limit.