Hello List, Below is a report on a telescopic observation of the ISS I did today. The station made a 78° pass, the first since the arrival of the P6 truss. You can read the entire report with drawings at: http://www.astro.uu.nl/~bassa/astro/temp/iss.htm There are some things I noticed. First it struck me how easy it is to observe the actual shape of the station. I was able to distinct the solar arrays as separate and of course the orange color of it. Second, I didn't observe the solar arrays after culmination. I did observe them before culmination, but I lost the satellite because my telescope ran into the tripod leg while I was manually tracking the ISS. After I reaquired the satellite the orange color was gone and I wasn't able to see the solar arrays anymore, just the grey/white modules of the station. It does seem plausible to me that because of a change in the angle observer-station-sun caused the solar arrays to disappear. It is seen in several pictures taken from STS97 that the newly solar arrays appear orange in one picture and black in another, depending on the orientation of the station, observer and sun. What does amaze me is that I haven't heard from any reports mentioning a change in color of the station during a pass, while it seems so logical. To me it also seems pretty easy to model and predict how the color and brightness depend on time and place for any observer on Earth as long as one knows the reflection characteristics of these solar arrays. They shouldn't be to hard to deduce if enough observations are being made. Regards, Cees Bassa P.S. I would advice any person owning a telescope to take a telescopic look at the ISS. It really is very awesome to see something with a shape flying along the stars. It's not hard to track the station manually, though some practice is handy. REPORT: The first time I observed the station after the arrival of the new solar arrays was on December 18 when the Netherlands were favoured again with passes of the satellite. It struck me the station was that orange. I had read reports of other observers on it, but I hadn't expected it to be so easy to distinct. I observed it again on December 19. For December 20 a pass of 78° high was predicted. For an overhead pass of 90° the stations distance will be it's altitude of approximately 370 km. For a culmination altitude of 78° the distance will be some 380 km minimum. I had observed both the ISS and Mir through a telescope before, but I was never able to see any details except an elongated streak of light. So I expected nothing this time. I was pretty busy that evening so I didn't have much time to setup my telescope, which made it a bit difficult to obtain the station through the the telescope when I came over, but when I got it in the 40x magnifaction field I immediately saw the T-shapedness of the object. Looking more carefully while manually following and finding best focus I could spot the two orange solar arrays seperately with the station as a greyish-white streak extending from the within the arrays. They were elongated stripes as in the left drawing at the top of this document. It was difficult to keep up the stations motion when it got at high elevations above the horizon and I lost it when my focusing tube hit one of the tripods legs. I had to swing the telescope to the other side of the RA-axis and reaquire the station again. I found the station pretty fast, at an elevation of some 65°-70°. As seen throught the telescope it had decreased in brightness and the two orange solar panels were not visible any more. Probably because of the angle between the sun, the station and me now it has passed my local culmination point. One thing that noticed was that the stations color was more grey instead of the white color it had before culmination. I was able to follow the station until it entered the shadow where it disappeared, slowly decreasing in brightness, as expected. ----------------------------------------------------------------- Unsubscribe from SeeSat-L by sending a message with 'unsubscribe' in the SUBJECT to SeeSat-L-request@lists.satellite.eu.org http://www2.satellite.eu.org/seesat/seesatindex.html
This archive was generated by hypermail 2b29 : Wed Dec 20 2000 - 12:28:44 PST