Wednesday, 24th Apr 2019

Category Archive: Astronomy: tips and tricks

Jun 18 2007

Calculating the actual f/ ratio of a picture


Every telescope or telephoto lens has its “magic” f/number: that is, the ratio between its focal length and aperture. Although we don’t go deeper into the matter as it’s not within the scope of this article, it’s worth mentioning that the higher the f/ratio, the longer the exposure time required to yield a given picture density (i.e.…

Jun 18 2007

Maximum Movie Length For Planetary Imaging


All wonderful hi-res planetary images currently taken by many amateur astronomers worldwide are all based on the same technique, i.e. selecting and aligning a lot of single frames from a single movie (typically an AVI file), which are then stacked and processed to yield the final result.…