The Dutch Observatory

International Space Station – Sun transit.  Tonight at 18:45:09 the ISS did transit the Sun.  The Center line was about 2 miles from my house, and because of the marginal seeing conditions and the cloud coverage I decided to give it a shot from my normal observing location.  Since I made my first full disk white light image this morning, I decided to give that another try.  With the ISS being 31″ arc seconds in diameter at a distance of 884 km, I figured I should be able to make out the shape of the ISS at this magnification.

I got tired of waiting for Solar or Lunar transits of the ISS, so I tried a direct image again like I used to do in 2008-2010. This was the first time without an Alt/Az mount with the C11 on the EQ6. A lot more challenging, but I managed to get a half decent frame. The pass was on the west side of my location, so the main solar panels stayed in the shadow. Never the less I am happy with the result.

The cloudy skies gave way and provided the opportunity to image the ISS again.  We chose a location off RT11 a few miles south of Charlie Elliott at the intersection with Henderson Mills Rd.  This time we used the SolarMax40 and mounted the camera perpendicular to the vertical axis to get an image that would let us beter understand the information provided in Clasky’s forecasts. Here the image made again by the Frank and Theo Team.

We had the opportunity again to image an ISS-Sun transit last Saturday.  Marie Lott, Frank Garner and I met in Mansfield to  image the event.  After a “pep-talk” Marie decided to setup her scope and she was rewarded with her first ISS-Sun Transit image.  I gave the DMK31 a try after I was able to recess the mount ring by about 2mm and the camera seemed to come in focus.  However, it turned out that my PC was acting up with producing irregular transfers from the camera to the PC, resulting in only 5 frames with the ISS.  The beauty of AR1121 however made up for this hickup.

Imaging Jupiter has been a challenge for me lately.  The seeing has been really bad so I have not taken much time to process the data I captured.  I might get back to that in a while when things slow down.  In the meantime I’ve been busy with outreach programs and keeping track of ISS transits.  Today we had a Sun transit at 12:45 P.M.  Frank and I went out to capture this and Art Zorka from Atlanta came out to see how we do this.  The forecast was for 31% cloud coverage, so we were prepared to miss the event.  However, the sky was clear during most of the setup, but shortly before the pass a cloud moved in…… and out.  Two minutes before the pass, I ran a test run on my camera and believe I captured another satelite transit the sun.  Than the cloud moved in and out and on the way out the transit happened.  The image shows partly clouds covering the sun while the ISS came through.

Today Frank and I tried for another ISS transit on the center line just at the other side of Hard Labor Creek Park.  We missed the Moon transit earlier this week, because of a storm that came through an hour before.  The sun was active with several sunspots, so we wanted to get these also in the image.  The image sequence was started a minute before the transit and stopped 15 seconds after the transit completed.  The transit accross the sun took 1.25 seconds. The ISS was at a distance of 696 km (435 miles).  At 26.6 Arc Seconds, the diameter of the ISS was 1/72 of that of the sun.  The images show also the active sunspots 1102, 1105 and 1109 at the Western limb of the sun.

In order to be better prepared for ISS transit imaging, I prepared this overlay image composed of images made at different times with differend optical components, increasing your chances of actually capturing the transit rather than missing it.  The ISS will move accross the face of the object in a certain direction, indicated as the time of on a clock with 6 o’clock being pointing STRAIGHT DOWN at the horizon, and  3 and 9 o’clock in paralell to the horizon.  So imagine your object how it is tilted at the time of imaging in regard to the horizon. (Will move from tilted  left when it rises, straight up when it passes the Meridian and tilted right when it sets. Knowing how the Sun or the Moon are tilted and knowing the travel direction of the ISS, you can determine where the ISS will travel accross the Sun  or Moon.  The image shows the approx. size of capture with the components I used.  In all three images I used prime focus, and a DMK21AU04.AS with a 640×480 resolution, so in the composite, two of the images are reduced in size to show relationships.  Image (!) shows the size captured with a Stellarvue SV80S with focal lenght of 750mm.  Image (2) shows the same refractor but with an Antares focal reducer screwed in the nose piece of the camera, and in Image (3) I used the same Antares focal reducer/camera, but with a Celestron C11.  As you can see, unless you are on the center line of the transit, you will need to research where the ISS will transit.

Following capturing the Sun’s transit of the ISS, we set out to capture a Moon transit.  The opportunity came on Tuesday evening at 11 minutes past midnight.  It would be an inferior transit with the ISS and moon being at an elevation of 10.6 degrees above the horizon.  In addition, at 1295 km., the ISS was three times further away than in our solar transit image.  I spend a lot of time planning and following the changes in ISS’ orbit in the days leading up to the event.  I also need to mention the help Clevis Jones gave us  with this.  Also studying the moon map to see if there was a prefered area wich we might want to try to include in the image.  I nailed it down to three possible sites and Frank Garner got us permission to setup at Mr. & Mrs Edwards property in Social Circle.  The cloud forecast was very iffy.  (See the the time-laps movie on YouTube.  The clouds finally broke five minutes before the event, and five minutes after, the moon sank behind the trees……  Here a composite image of the pass as I captured it, and an animation at approx 1/3 speed.  At the time the moon was 10.6 degrees above the horizon, the ISS at 1295 km. was three times as far from us as in our Solar transit pass from July 30st. and the seeing and transparency was terrible at this elevation.  All three of us captured the transit.  Regardless of how the images came out, this first attempt of a moon crossing was a fantastic event for all of us and a great thrill.  Thanks again to the Edwards for allowing us to be in their front pasture until long after midnight!!  

And here the YouTube movie of the transit.

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It has been coming a long time.  An image of the ISS transitting our Sun.  The last attempt this past Monday failed because of last minute confusion about the time.  Today Frank Garner and I set out to capture this afternoon’s Sun transit of the ISS on its 67033 orbit since its launch on November 20, 1998.  The distance to the ISS was 405 kilometers.  The angular size of the satellite was 47.2″, which makes it 1/40th of the diameter of the Sun.  The ISS came close to Sunspot AR1092 and some nice solare proms are visible also.  We almost missed this pass as an object passed accross the field of view about 20 seconds prior to the ISS, which we first thought was an early pass.  We stuck to our imaging plan and caught the right pass on time. It also appears that the transfer between the camera and my laptop was quite busy, since it skipped a few images in the sequence.