I have a particular interest in satellite transits across the solar/lunar surfaces due to the opportunity they present
the lucky observer to discern greater physical detail and structure as a result of their silhouette against the bright
background of the sun and/or moon; the ability to restrict the satellite's location in the daytime or evening sky to an
area measuring 0.5°x0.5° with little or no effort; it permits for the bypassing of satellite tracking which itself is a
challenge due the very short period transits are visible during a particular overhead pass; and the difficulty in
obtaining accurate and timely orbital elements and TLE's. As this "search and identify" project has literally become a
DAILY ritual, I expect this web page to be updated constantly with more and more images of the very unique phenomena of
satellite transits across the solar and/or lunar disks.
Note: The capture of a solar transit by the International Space Station was an incessant chase
for 3-4 years and until July 28, 2005 when the ISS (with
STS-114)
was finally captured transiting against the Sun and which included the space shuttle Discovery. Approximately nine months
later, the ISS was also caught transiting the rising moon (click
here) albeit at a very low altitude. My best ISS transit
captures occurred in
2018 and
2023
when the ISS was at a range of 441.6 km and 551.4 km away, respectively,
when transiting the Sun whereas in 2010 I was able to also capture the ISS during the day transiting
Jupiter
at a range of 439.5 km as well as
Mars
at a range of 565.9 km.
With the launch of the Chinese Space Station Tiangong-1 module in 2011 and the Tiangong-2 module in 2016, a new challenge
presented itself and where a small number of transit opportunities have presented themselves involving both the Sun and Moon.
However, orbital maneuvers and the weather play a vital role with such events and, regrettably, they proved repeatedly
to be prohibitive stumbling blocks. However, on Aug 29th, 2023 everything seemingly came together thanks to a stable orbit,
favourable weather conditions and the very good altitude of Sun which finally permitted for the pursuit and successful
capture of the Tiangong Space Station transiting the Sun for a mere 0.69 seconds and as illustrated below.
The Chinese Space Station Tiangong ("Sky Palace") represents China's most recent entry into space and follows the Tiangong-1 and
Tiangong-2 modules. It is approximately one-third the size of the ISS (by volume) and has a permanent crew of three astronauts but
can accomodate up to six astronauts during missions involving crew rollovers. It has a current mass of 96,000 kg and measures 55.6
meters in length and 39.0 meters across with plans to expand the station from the three existing modules to a total of six modules
in the future with the fourth module ("Xuntian") tentatively scheduled for launch in 2024.
Note: For a complete set of images captured so far involving satellite transits of both the Sun and Moon,
click here.
Satellite(s): Tiangong USSPACECOM Cat No: 48274 (Tianhe) Physical Dimensions: 55.6 x 39.0 m Orbit / Inclination: 381 x 390 km, 41.47° Range (Image): 541 km Angular Diameter: 6.87" Pass Details (ISS):
Launch Date (UTC):
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Date: Aug 29, 2023 16:01:40 UT+3 Location: Athens, Greece Equipment: AP 160 f/7.5 StarFire EDF AP 2x Convertible Barlow AP 1200GTO/CP3 GEM Canon EOS 6D Mark I Baader BCF2 Filter Baader UV/IR-Cut filter Baader ND-5 (full-aperture) Exposures: 3 x 1/4000 sec ISO 2000 RAW Image Format Custom White Balance Manual Mode Continuous Servo Mode Software: Digital Photo Pro V4.6.30.0 Photoshop CS6 Processing: RAW to TIFF (16-bit conv) Brightness/Contrast Unsharp Masking Resampling JPG Compression |