There seems to be a lack of agreement between surveying and astronomy on the name of the angle and the definition (see appendices). Therefore, I suggest this convention. Assume that the observer is able to distinguish Ralph from Norton. If the orientation is, e.g.: n n R n | \ | / | \ n--------R | R---------n / | \ | / | \ | / R R n R then the vertex angle is: 0 45 90 180 270 330 and the observer should report a vertex angle between 0 and 359.99 degrees. I.e., the vertex angle (see appendix) of Norton with respect to Ralph. If the observer cannot distinguish Ralph from Norton, then the angle reported should be a vertex angle, determined in the same way, between 0 and 179.99 degrees. Modelled after PPAS, I suggest this format: Walter I. Nissen, Jr., CDP, email@example.com, 55 Barrett RD #808, Berea, OH 44017-1657, USA, 216-243-4980, -81d 51.823', 41d 22.413', 256m yy-lllpp yy-mm-dd hh:mm:ss.ss NN d->d al v.a UML m1 sp RN mag apur Comments 96- 29 ? 96-07-11 4:43 WN N->S 50 140?LML 6 xx 7x35 steady angle 96- 29 ? 96-07-12 3:35 WN N->S 65 45?LML xx 11x80 TiPS 96- 29 ? 96-07-12 3:38 WN N->S 40 45?LML xx 11x80 TiPS 96- 29 ? 96-07-16 2:39:30 WN N->S 40 0 V 5 xx 11x80 TiPS 96- 29 ? 96-07-16 2:40:30 WN N->S 30 0 V xx 11x80 TiPS 96- 29 ? 96-07-21 2:18:52.08 WN N->S 57 150 LML xx 11x80 TiPS 96- 29 ? 96-07-21 2:24:39.53 WN N->S 14 175 LML xx 11x80 TiPS 96- 29 ? 96-07-23 1:50:00 WN N->S 58 sp? 11x80 TiPS 96- 29 ? 96-07-23 1:51:30 WN N->S 46 10 UML xx 11x80 TiPS 96- 29 ? 96-07-23 1:53:30 WN N->S 28 5 UML xx 11x80 TiPS The pp is the piece number in the COSPAR ID (apparently no agreement yet) UTC data and time are given (give local time and zone also if your clocks are not set to UTC, or if you have any doubt about the conversion) NN is the observer's initials (from PPAS) al is the altitude, if the al's you provide don't suggest the maximum you are encouraged to provide a record to give the max altitude d->d is the direction of motion v.a is the vertex angle (norton above = 0, norton left = 90, etc.) UML is Upper Mass Leading, Lower Mass Leading or Vertical m1 is total visual magnitude sp is blank if no sparkles are observed, sp if 1-5 are observed, SP if more than 5 are observed RN is blank if the orientation could not be observed, xx if Ralph could not be distinguished from Norton, and RN if it could. mag is image magnification apur is aperature in mm Comments are encouraged to run into paragraphs if you have things to say Do we need left->right also? Azimuth also? Anything else? The dashes(-) in the date and the colons(:) in the time are an unnecessary affectation. Cheers. Walter Nissen firstname.lastname@example.org --- David Dunham writes: ... vertex angle in occultation predictions ... is measured like position angle, but 0 is the local vertical direction, rather than north. Hence, 0 deg. is up, 90 is to the left, 180 is down, and 270 is to the right. -- In http://www.auslig.gov.au/geodesy/astro/definiti.htm - size 8K we find this: AUSTRALIAN SURVEYING & LAND INFORMATION GROUP Scrivener Building, Dunlop Court, Fern Hill Park, Bruce ACT 2617 PO Box 2 Belconnen ACT 2616 Phone: +61 6 201 4201 Fax: +61 6 201 4366 COMMONWEALTH OF AUSTRALIA 1995 Zenith Distance The zenith distance is a vertical angle measured from directly overhead, down to the required point. An ideal horizon has a zenith distance of 90 degrees. Vertical angle The Vertical angle is the angle measured in a vertical plane, from the horizon to the required point. Directly overhead would have a vertical angle of 90 degrees.