Satgen 18 by GM4IHJ 2 August 1989 Meteor Shower Maxima - Timings One serious difficulty facing the enthusiasts who communicate with one another by bouncing their signals off the ionized trails of meteors , is predicting just exactly when best results will occur. Meteor streams concentrate along the paths of old comets. Indeed most meteors are believed to be debris expelled from comets,which continues to follow along the orbital track of the comet, long after the comet has gone. Things which are fixed in space , like stars and meteor streams, keep Sidereal time, which differs from the Solar Mean time we use on the Earth by roughly one extra day every 365.25 Earth days.So meteor shower maxima shift their timing roughly 6 hours later each year, and then jump back one whole day ,once every 4th year or so when we add February 29th as an extra day. If this were all that happened it would not be too hard to calculate timings of maxima, but unfortunately the other members of the Solar system often perturb the streams. However, help is now at hand. Sky and Telescope magazine for August 89 has published on page 195 a neat little program which purports to sort out both the Sidereal time element and the perturbation element of the calculation. With the proviso that IHJ has not tested this program . Here are its predictions for 1989 and 1990 :- Shower 89 maxima 90 maxima Quadrantids Jan 3rd at 1800 ut Jan 4th at 0009 ut Lyrids April 22nd at 1226 ut April 22nd at 1850 ut Eta Aquarids May 5th at 0138 ut May 5th at 0815 ut Delta Aquarids July 28th at 0722 ut July 28th at 1313 ut Perseids August 12th at 1208 ut August 12th at 1826 ut Orionids October 21st at 1805 ut October 22nd at 0053 ut Taurids November 3rd at 0550 ut November 3rd at 1236 ut Leonids November 17th at 2112ut November 17th at 2241 ut Geminids December 13th at 2220ut December 14th at 0453 ut Some of the perturbation timings seem a little odd (Leonids ), and the Quadrantids timing given by the program is several hours later than my radio observations, but visual observation peaks, and radio peaks, often differ markedly.None the less, I hope ms enthusiasts find this info useful. Please do not write to me for the program. Get the magazine from your local library. Sundial Alignment of Geosats. I see one UK mag has proposed a dodge for lining up an Astra aerial by putting up a post and checking its shadow line at 1215 BST. Do not believe it. The Earth is actually in an eccentric orbit round the Sun , so the Sun line can vary by + or - 4 degs depending on time of year. Most Astra aerials have a 0.5 deg beam ! 73 de GM4IHJ @ GB7SNE