More detail notes for imagers on these two ISS passes close to Saturn. I. Friday night For the Friday night pass, the Sun 12 degs below the horizon near astronomical twilight but the pass, when seen from the Salt Lake Valley floor, is about 2.2 degrees from Saturn. This pass is suitable for wide-field photography. Of the two nights, the long range forecast is less favorable for Friday vs. Sunday night, but this opportunity occurs near astronomical twilight while the Sunday night opportunity occurs just 10 minutes after civil sunset. CalSky shows 2008-04-11 21h05m10s ISS Appears 21h00m19s 3.0mag az:305.4° NW horizon Culmination 21h05m10s -4.5mag az:217.5° SW h:82.2° distance: 343.9km height above Earth: 342.2km elevation of sun: -12° Disappears 21h06m52s -3.2mag az:131.3° SE h:21.7° My notes: Passes 2.2 degrees east RA sweep from Saturn. ISS path target at: JE102706+125713 Saturn at: JE101826.5+122937.3 RA sweep from Saturn to ISS path target is: +000840.00+002736.0 at a CCW PA about 260 II. Sunday night The Sunday night pass occurs when the Sun is only 2 degrees below the horizon or about 10 minutes after civil sun. This raises the question of whether 0.4 mag Saturn will be visible to the naked eye and complicates telescopic targeting and imaging. However, the ISS passes within 1 deg of Saturn and with a short-drive to Emigration Canyon or along I-80 you can be directly on the centerline of the ground track for an image that will run directly over Saturn. This potential occulation image of Saturn makes the pass a tempting photo opportunity even though the pass is close after Sunset. Pre-testing locating and imaging of Saturn 10 minutes after sunset between now and Sunday may be a good idea to determine if imaging a pass of Saturn is practical. 10 minutes after sunset, the -4.4 mag ISS should be visible without problems. Even if Saturn is not a practical imaging target, the -4.4 mag ISS will pass about 11 degs from the -10 magnitude near first quarter Moon on a CCW PA of 225. This also may be a good op for taking a fish-eye lens ultra wide angle image of the Moon and the ISS. CalSky shows - 2008-04-13 20h13m02s ISS Appears 20h08m10s 2.5mag az:306.0° NW horizon Culmination 20h13m02s -4.4mag az: 37.0° NE h:89.5° distance: 340.7km height above Earth: 342.0km elevation of sun: -2° Disappears 20h17m25s -1.3mag az:127.4° SE h:2.0° 20h13m38.43s ISS Close to Saturn. Separation=0.978° Position Angle=51.7° Angular diameter=43.0" size=73.0m x 44.5m x 27.5m Satellite at Azimuth=126.3° SE Altitude= 51.1° Distance=430.4 km Magnitude=-4.3mag My notes: For an on transit-line ground-track image opportunity, promising public space setups in Salt Lake County include: I-80 Along I-80 at the East Canyon off-ramp. The transit line passes about at the guard station to the East Canyon Dam complex. The guard station has a separate off-ramp about 1 mile west of the East Canyon off-ramp on the westbound (to SLC) side of the freeway. Either setup: a) at the East Canyon exit off-ramp in the UDOT maintenance station parking lot. b) at the East Dam complex off-ramp 1 mile west of the East canyon exit. Both locations are between 1000-1500 ft either east of west of the ground track center line. The UDOT maintenance parking lot is more shielded from freeway noise and lights. Emigration Canyon The transit line is between Skycrest Lane and the turn-off to the Emigration Oaks subdivision (the Pink Garage). (Skycrest Lane is about 2 miles north of Camp Kostopolus.) Setup anywhere in the public turnouts about 1/2 mile north of Camp Kostopolus but south of the Pink Garage should put you within 2000-1000 feet of the centerline. A fire station is under construction next to the Pink Garage. That also might be a potential setup location. - Kurt __________________________________________________ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com