Hi Dave (et al.), I am a developer of a satellite viewing program (SatSpy for Windows) and I thought I might try to address some of your issues. I am a software developer with over 16 years of experience, 10 of which were spent developing tracking software for NORAD, the US Space Command and other agencies. I can only speak for myself and my software, so let me describe how I approached some of these design issues: First: Visual Magnitudes SatSpy uses two different approaches to providing visual magnitudes. In version 2.0, I added a estimated visual magnitude mode, using data and formula provided by Ted Molczan, that computes the magnitude at each point in a pass. If you want to know which bright passes will occur in a particular evening, you can open a window showing all of the passes sorted by estimated visual magnitude. SatSpy retains a second mode (from v1.0) that uses empirical magnitudes that I gathered from various sources, including my own observations. This mode is primarily useful for estimating the relative brightness of different sats rather than particular passes. Second: The question "what can I see tonight?" SatSpy lets you answer this question in a couple ways. First, you can open a Viewing Opportunities window. This shows all passes over a period from 10 minutes to 10 days. The passes are shown as time lines (similar to a Gantt chart) so that you see at a glance what is going over and when. Furthermore, the passes are color coded (green=best, yellow=marginal, red=poor). You have the option to define what is a good pass and what is not (defaults are provided). You also can filter out daytime and shadow passes. You can set your time period to start at specific local times, such as the start of nautical or astronomical twilight. Once you have opened the window, you can click on any of the passes to bring up supplementary windows including Skytraces (projection of the pass against your local sky), groundtraces and 3D Orbit Views. The other approach is the Multiple Skytrace window which shows all passes for a period of time up to 45 minutes. This time the pass are shown as projections against your local sky. The passes are color coded, to show when portions of the pass are sunlit and in the earth's shadow. All of the same filters apply to this window as well. Once you have figured out the answer to what you can see tonight, you can open a Single Skytrace window for each pass. From here, you can attach time and magnitude labels for any step in the ephemeris. This will show you exactly when the satellite passes near a particular sky feature and the estimated brightness at each step. Third: Automation All of the filters,etc. described above can be predefined and stored in your initialization file. When you want to know what is up tonight, you perform the following steps: 1) load your elsets, 2) specify the time period of interest, 3) open a Viewing Opportunities window, 4) pick the passes you want, 5) print skytraces for those passes and 6) go watch the satellites. In closing, I apologize to any who may be offended by my long description of a particular program. However, if you would like to try it for yourself, you can download a copy from http://www.usa.net/acappella/satspy/satspy.htm. BTW, I also post an elset file (elsets.zip) that contains over 1100 of my favorite elsets. This is updated weekly from elsets found at the JPL site (Ted Molczan's file) and the Celestial Archives (tle.new, visual.tle and weather.tle). Cheers, Dave. At 11:47 AM 12/14/96 +0000, you wrote: >>I am wondering why, with all of the satellite-prediction software >>we have today, it is still necessary to ask this question, especially >>since magnitude estimates can be found in Ted Molczan's elements >>file. Why doesn't one of these programs simply run through the >>elements list, calculate a predicted magnitude, and if it shows >>up brighter than a predicted magnitude, print it out? So far as >>I know, only QUICKSAT does something close to this. However, it >>uses its own file of predicted magnitudes which are actually >>'greatest ever' brightness rather than 'expected' brightness, >>which results in a lot of predicted passes that are not seen. >>Is there some other software package that gives this information? > >No! You are not alone. I have been lurking on this list for a couple of >months, a satellite newbie trying to get into this exciting field. Until >your post I assumed I was being stupid. For the novice at any rate, it seems >frustratingly difficult to get simple information. > >What a newbie wants to know (and perhaps an oldbie also?) is "what can I see >tonight?" not "hmmm...I have a sudden inexplicable urge to look at Cosmos >1741 r - I wonder when it's visible?". > >For me, the satellite software approach cannot take off (sorry) until all >current element sets are easily and transparently available to the user from >a definitive source. So the approach I use is to print the marvellous page at > >http://www.physics.ox.ac.uk/sat/pred/London/predall > >(I live in London). But even here the information is ordered *by satellite* >not by event, so I have to scan through the list looking for the right >day/time, checking to see if the elevation is great enough, and if the pass >is sunlit (it took me a while to get to grips with that stuff, but I can >read it now). Then I have a satellite number, but, frustratingly, not a >satellite name (I find it hard to "bond" with the small integers). > >May I briefly describe my fantasy satellite software? I cannot see why *any* >user input is required after starting the application. Assuming that I have >already configured my location and UTC-offset, and that the application >comes with nice default "sight quality" cutoff values (eg for >magnitude/elevation/visibility-time), then I want to immediately see a >summary list of forthcoming time-ordered events, each event having a single >local date/time and a satellite name. If I press one button I want expanded >information (the more detailed location/visibility data). > >The list that I see can be "filtered" according to various criteria. For >example, one set of buttons will let me increment/decrement each of the >"sight quality" values, in each case refreshing the list in order to reflect >the new criteria. Other filters could be established by the user (eg >favourite satellites, flashing satellites). I'm sure the knowledgeable ones >here can identify the important filters. > >(I feel sure that if "Bill" were into satellites it would be done this way <g>). > >My comments are intended to be constructive criticisms, I hope no-one is >offended by my presumption. Although I am a satellite neophyte, I earn my >living as a software developer. The currently available software is >fantastic in terms of speed and accuracy, but does make certain assumptions >about the level of technical skill and motivation of its users. > >glad to have "broken cover" > >regards > >Dave Ziemann > > >