International Space Station Solar Transit

The International Space Station transits the Sun passing by sunspot group AR2585. I made my monthly check for ISS transits near Austin this morning. There was a good possibility in just four hours with the sun shining brightly outside. After a quick lunch, Mary and I tossed the camera and scope in the car and headed north. Lots of clouds had moved in and we decided to head north-west to Briggs, Texas rather than north-east to Round Rock. We arrived in Briggs with about 15 minutes to spare with about 50% cloud cover. I took measure of the motion of the clouds and picked a spot to set up. Within seconds of the transit the sun was behind a cloud, but I finally have images of the ISS!

Questar 3.5 telescope with a Sony a6300 shooting 30 fps 4k video at prime focus from Briggs, Texas. Exposure 1/320 sec at ISO 200. 2016-09-04 19:15 UT. UHD 4k video frames deconvolved in Lynkeos, then composited and exposure adjusted in Photoshop.

Overall the ISS is roughly the size of a football field. It was about 300 miles away when these images were taken. Seeing conditions were not very good. Wind gusts were blowing hard enough to shake the scope a bit. This stack of the best 5 images shows some detail including the 8 long solar panel arrays along side the main modules.

The original 4k video, slowed down to half speed (in case you blink) is on Vimeo: ISS Solar Transit 4k Video

The following data is from ISS Transit Finder:

Sunday 2016-09-04 14:15:48.01 • Solar transit
ISS angular size: 61.34″; distance: 450.44 km
Angular separation: 1.3′; azimuth: 206.1°; altitude: 63.7°
Center line distance: 0.16 km; visibility path width: 4.57 km
Transit duration: 0.57 s; transit chord length: 31.6′
R.A.: 10h 56m; Dec: +06° 47′; parallactic angle: -21.8°
ISS velocity: 55.8 ′/s (angular); 7.31 km/s (transverse)
ISS velocity: 1.11 km/s (radial); 7.39 km/s (total);
Direction of motion relative to zenith: 110.0°
Sun angular size: 31.7′; 31.0 times larger than the ISS

ISS Transit Finder can make calculations up to seven weeks in advance. The ISS makes small orbital adjustments. It is best to recheck the ground track a few days before and a few hours before to get the most accurate estimate.

Content created: 2016-09-04




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