Hi all, Having captured six transits in the last few months , all on video , I am finding that the track can be slightly "south" of the line predicted.Not critical , unless you happen to have positioned yourself on the northern edge of the ground corridor , and are using a small FOV. I put this down to the fact that keps are usually a couple of days old .The reason I say this is that when I did the Lunar Transit , the keps had only been updated within hours , and that one was right on the button . I'm using Tom's alert system as an initial heads up , then switching to CalSky to decide where I need to be. All positioning is done using a Garmin GPS , with timings set to GPS synchronisation , and a radio controlled timepiece.Before leaving for the location I make a detailed drawing of the predicted path from CalSky , checking also any sunspot activity details on Spaceweather .com . Whenever possible I try to position myself so that the station will pass between or near to an active group. Tom , I think your visual pass yesterday was a high elevation one and I agree how big the station seems during these transits....in excess of 10" or so. Once everything is set up , and the camera is running , all you can do is wait , and hope :O) With half a dozen transits in the bag , I'm tempted now to try and move up to a higher magnification , as I did on June 24th , but when it comes to the crunch , I'd rather get the whole thing on film , than risk just one or two frames. Perhaps the best way forward would be to get a second scope lined up , one with small FOV , the other full disk. If anyone is interested in testing out the accuracy of Tom's predictions , or CalSky , and comparing them to actual results , you should be able to save my animations from the Satcom site http://www.satcom.freeserve.co.uk/isstrans.htm * ,to disk , then run them in Windows fax viewer . That way they can be magnified to full size.The last one , from the 29th , is particularly handy for this purpose as the pass takes a couple of seconds and runs between to sunspots. Again a little south of the predicted track. I think we have to congratulate both Tom , for his alert service and Arnold for CalSky.....without these programmes we would not be getting the chance to see these magnificant events ! Best wishes, John. * If any problems are encounterered , email me and I'll send a full size animation direct. ----- Original Message ----- From: "Thomas Fly" <thomasfly@j2ee-consultants.com> To: "SeeSat-L" <SeeSat-L@satobs.org> Sent: Sunday, August 31, 2003 5:33 AM Subject: ISS Transit prediction problems? > Hi Willie, > > Somebody else (from the UK) had a similar complaint- he was using "The Starry > Night Backyard." I checked with CalSKY, however, which confirmed the > prediction. I also checked this prediction with CalSKY, and again it confirms > the transit- see the attached CalSKY HTML file. > > The point about the azimuth being wrong seems to be valid- that's what you get > for not living in the Northern hemisphere! (Maybe it should be 123 degrees west > from south?) > > By chance, I observed my first ISS solar transit today!!! It was touch & go, as > big clouds gobbled up the sun twice, while I was setting up. I'd taken along an > ancient Radio Shack "Time Cube" (that receives the U.S. government atomic time > broadcasts), as my cue to click my Kodak DC290 in 2 fps burst mode, only to > realize that the road I was parked along went to a local water treatment plant, > and had a high-voltage power line that drowned out WWV for 100 feet to either > side! I projected a 5" diameter image of the sun onto a slide projector screen, > which gusts of wind conveniently knocked into my camera tripod & telescope a > couple times... > > At some point, I stuck my head inside the car to read (after my pupils had > dilated enough) that it was now 1:06 PM (transit predicted at 1:07:00), and as I > got back, I thought I saw a speck go across the sun... but a few seconds later, > an upside-down T went zipping across, startling me for a number of reasons, > including how large it appeared to be! > > While I was on my predicted (roughly 48 hours in advance) centerline- > iss-transit.sourceforge.net/transits/matches-1p.txt - the transit was about 1/4 > of a solar radius to the southwest, implying that the centerline actually was > about 0.3 miles to the southwest. Curiously, yesterday evening CalSKY had > indicated that the centerline was about 0.25 miles northeast of my prediction. > (Roland Stalder used CalSKY to fine-tune his aiming, which was exceptionally > well-centered, despite the relatively small field-of-view of his movie... just > good luck?) > > You can sign up for ISS fly-over alerts (either "all" or "visible only") at > liftoff.msfc.nasa.gov/RealTime/JPass/PassGenerator > > You can also make use of > spaceflight.nasa.gov/realdata/sightings/SSapplications/Post/JavaSSOP/JavaSSO P.ht > ml When I enter 33.9375 S, 18.4736 E, it indicates a "solar separation" of 0.3 > degrees at 16:00:40 (and an azimuth of 303 degrees east from north, which would > be 123 degrees west from south :) > > When I click on "SkyTrack," it gives me a "NASA SkyWatch" applet that shows the > ISS nailing the sun, while Venus looks on. > > And after all of that, I believe I see your problem- the times given are your > local time, not UT! > > Cheers, > Tom > > > ----- Original Message ----- > From: "Willie Koorts" > To: "ISS Transit" <iss-transit@j2ee-consultants.com> > Cc: "Greg Roberts" > Sent: Saturday, August 30, 2003 10:26 AM > Subject: ISS Transit prediction problems > > > Hi Tom > > Thanks for the regular alerts. Unfortunately, I have not had the > opportunity to try any since they happened almost always on inconvenient > times for me. > > The last one you sent again is due in Cape Town while I'm doing standby > duty at our observatory outstation in Sutherland. I sent the data to a > friend who found some problems with your predictions. > > Attached are his findings. Could you please investigate? > > Thanks > Willie > > > ---------- Forwarded message ---------- > Date: Sat, 30 Aug 2003 08:20:43 +0200 > From: Greg Roberts > To: Willie Koorts > Subject: Fw: ISS Solar transit > > I checked the ISS transit alert- something is wrong-- if time is 16hr UT the > sun cant have an azimuth of 123 degrees - it must be 360-123= 237 and even > that doesn't look right as I don't think the suns that far south yet...am I > reading the prediction wrong - see its for Monday 1st Sept. > > Cheers > Greg > > > ---------- Forwarded message ---------- > Date: Sat, 30 Aug 2003 10:10:21 +0200 > From: Greg Roberts > To: Willie Koorts > Subject: Re: Fw: ISS Solar transit > > Hi > > I've done a check with GUIDE - and element set dated Aug 29. ISS is nowhere > near the sun- in fact well below the horizon. The position of the sun at > 16h00m38s UT is azimuth 283.18 deg, elevation 4.65 degrees so something > wrong somewhere - hope I haven't made a mistake but it definitely looks like > the prediction supplied is garbage :-)) > > Cheers > Greg > > > > ----------------------------------------------------------------- > To unsubscribe from SeeSat-L, send a message with 'unsubscribe' > in the SUBJECT to SeeSat-L-request@satobs.org > List archived at http://www.satobs.org/seesat/seesatindex.html > > > ----------------------------------------------------------------- To unsubscribe from SeeSat-L, send a message with 'unsubscribe' in the SUBJECT to SeeSat-L-request@satobs.org List archived at http://www.satobs.org/seesat/seesatindex.html
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