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D7200 DSLR Crescent Venus, ISS, Saturn

Posted: 3 August 2015

As mentioned in my Daytime Venus report from Sunday, 2 August, 2015, the sky clouded up during the morning. The forecast for Sunday day and night had been for clear skies, but our monsoon weather had other ideas. My last chance for imaging the ISS during an excellent pass would be Sunday evening, having missed one excellent and two good passes over the last few nights due to clouds. Fortunately, sky conditions improved during the late afternoon.

Open: Sunday, 2 August 2015, 1804 MST
Temperature: 106°F
Session: 852
Conditions: Mostly clear (at start)

First I synced the observatory clock to WWV. 1811 MST: viewed Venus, 83X. Then set up for prime focus + 2X PowerMate imaging using the D7200 DSLR. This is a stack of 957 frames (15 seconds of HD video, 1.3X crop factor, 60 frames per second), 1/400sec, ISO 400, showing the crescent phase of Venus:


Unfortunately, Venus was a little blurred out by thin clouds and its low altitude.

This is how Venus appeared on the DSLR Live View screen (zoomed):


1827 MST: resumed observing Venus, 166X. I also updated the TLE for the evening's excellent pass of the International Space Station (ISS). The pass would occur about 20 minutes after sunset. 1837 MST: viewed Jupiter, faintly visible at 83X. No cloud belts were visible due to the low contrast view against a bright sky. 1856 MST: Jupiter's North and South Equatorial Belts were now visible, 83X. 1907 MST: returned to Venus, which would be my initial focus test object for the upcoming ISS pass.

1905 MST: mounted the D7200 DSLR at prime focus + 2X PowerMate, used Venus to focus, locked the telescope focus, and checked the Antares 7x50 Illuminated Crosshairs Finderscope alignment. Unfortunately, increasing clouds were coming in from the south and west. And there were now thin clouds in much of the sky. 1925 MST: sunset. Decided to slew to the star Antares and try a focus test with the Bahtinov Mask. That worked and I made a slight adjustment in the focus. I was now ready for the ISS pass, which would begin behind a tree and against a still bright twilight sky. As I was waiting for the pass to begin my iPod playlist had begun playing music from the movie "The Right Stuff". That was appropriate. When the pass began the ISS was not visible so I began tracking on time. Unfortunately, by the time I picked up the ISS about 2 minutes later the pointing was too low by about 15°. I had to manually slew the telescope to catch up with the ISS and center it in the finderscope. I finally got it centered as it neared mid-pass. Since the AutoStar tracking calculations were so far off for this pass, tracking was horrible. I did a 7m56s, 1.3X crop factor, 60fps, 1/1600sec, ISO 5000, HD video recording. After the pass was over I slewed to Saturn and discovered that the focus had shifted somewhat. Argh. So, with the combination of imprecise focus, poor tracking, and thin clouds, I managed to get only one (sort of) reasonable image of the ISS:


By the way, I have updated my article on Satellite Tracking tips.

1957 MST: decided to image Saturn. Thicker clouds were near the planet. This is a stack of 936 HD video frames, 1.3X, 60fps, prime focus + 2X PowerMate, upscaled 200%, taken through thin clouds:


2004 MST: removed the camera and viewed Saturn, 166X. The moons Titan, Tethys, Rhea, and Dione were visible.

2014 MST: the clouds in the south were now increasing. Satellite images showed more clouds coming from the south. 2017 MST: final looks at Saturn, 166X and 83X. Then viewed M57 (Ring Nebula), 83X.

2021 MST: the sky was lighting up from distance lightning reflecting off the clouds. Decided to end the session.

Close: Sunday, 2 August 2015, 2036 MST
Temperature: 82°F
Session Length: 02h 32m
Conditions: thin clouds in most of the sky

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