ISS Transits Sol 2/5/17

[Bruce D]

These events happen every so often- a week from tomorrow on Sunday February 5 at 3:50 PM the International Space Station will pass in front of the Sun as seen from my house. I plan to try to view this event and you are welcome to join me.

Why is this of interest? Well, even in a small telescope you can see a surprising amount of detail when looking at the ISS. The trouble is the little rascal is moving quickly and it's difficult to get your scope on it and have a steady enough view to actually see anything. In THIS case we have the advantage: we (theoretically) know exactly where the ISS will be at a specific time (it will appear to cross the disc of the sun at 3:50 PM) and we can aim our telescopes at the sun (repeat the "Astronomer's Mantra" WITH PROPER SOLAR FILTER) ahead of time and wait for the ISS to show up, at which point we will have a beautiful view of the ISS backlit by the sun. Also a great opportunity to image the ISS.

This particular event has a few advantages:

1) Often these transits happen during the week when many of us are working, this time it's on a Sunday. You'll be home in time for the superbowl!

2) These transits happen very quickly- since I've been following them for a few years now the vast majority of them have a transit duration of under 2 seconds. I saw (well, it was cloudy) one who's duration was just over 3 seconds. The duration of THIS event is over 4 seconds (if it were any longer we might need an intermission) so if you are looking in the eyepiece you'll have a slow count to 4 to view the ISS- plenty of time to get a good look.

3) Often these happen early morning or late afternoon when we are looking through lots of turbulent air, for this event the sun should be relatively high in the sky.

4) Often these happen a number of miles from my house, this time I'll either view it from my yard or a spot a mile from here... OK, so maybe that's only an advantage for ME-!

If you are interested in giving this a try send me an email or PM. -

Technical details follow...

Crosses the disk of Sun. Separation=0.114° Position Angle=305.4°, Position angle vertex=265.2°. Transit duration=4.10s
Angular diameter=20.1" size=109.0m x 73.0m x 27.5m
Satellite at Azimuth=236.7° WSW Altitude= 11.5° Distance=1376.8 km
In a clock-face concept, the satellite will seem to move toward 0:10
Angular Velocity=7.2'/s

[Pete]

Thanks so much for the heads-up Bruce. After jousting with CalSky for about 1/2 hour it appears the ISS is making a central solar pass over Wishing Star Observatory Sunday, 5 February 2017, 15h 49m 37.50s It's a 3.34 second transit according to CalSky for my position. And the ISS will be 24" in size.

Going to attempt imaging with the new planetcam.

Where are you getting your alert data from please? It seems to be more complete than anything I can find.

Pete

[Pete]

Oh crud! Just got real and realized that sunset's at 17:06. At 15:49:38 the sun's only 12° above the horizon and well below my treeline

Never observed an ISS transit and was looking forward to it.

Pete

[Bruce D]

Hi Pete- I guess I have not fully immersed myself in the winter experience yet- I was thinking at 3:50 PM the sun would be higher in the sky but no... I just looked out the window (3:51 now) and the sun is just barely clear of the trees. I will plan to move to a spot about a mile from my house that has a much lower horizon. Folks are welcome to join me.

I have several automated email alerts set up on CalSky, ISS transiting the sun/moon/planets is one of them. I'll forward the email alert to you.

By golly you are right, I hadn't followed the track down into RI but the centerline does go right by Wishing Star. I think several years ago I did my "takeaways and goesinta's" and estimated the footprint of the ISS's shadow extends about 8 miles to either side of the centerline. That is to say if you are on the centerline the ISS will appear to pass through the center of the sun's disc, 8 miles to either side and the ISS will just graze the sun's limb.

Here is the centerline plot:
http://www.calsky.com/?Transitline=&sho ... mainbody=0

[AstroGeek]

Not to be a downer, but the ISS is not "astronomy". The coolest thing I've derived from their 'mission' so far is that it's cool to look at when it passes overhead. Can you describe anything that they'e accomplished so far, without Googling it? They promised to have a remote scope on-board that amateurs could utilize from the ground. They changed their mind on that, so the ISS is dead to me. (see Skylab)

[Bruce D]

I think they realized the remote scope would not be practical- within 5 minutes they would have a waiting list years long...

Still, I think it's interesting to be able to see structural detail on an object orbiting 300+ miles up through a small telescope!

[Apollo XX]

Can you describe anything that they'e accomplished so far, without Googling it? (see Skylab)

Good question. As far as experiments go, no, I can't. But one significant thing does come to mind without doing any research - the long term effects of living in microgravity on the human body. I suspect that if we ever do get to the point where we actually launch a manned mission to Mars, this research will be invaluable. Just the evolvement of the whole living-in-space thing has been a pretty big accomplishment, I think.

You've made me curious though. I'm going to Google ISS experiments.

[Paul D]

I had always thought that ISS main mission was to do experiments for space travel and possible colonization of planets. I never thought it was going to have any astronomical applications. Isn't that why we have Hubble and the other space bound robotic missions?

But I do have to agree with Steve that the ISS isn't astronomy.

[Bruce D]

The Sunday forecast does not look promising...

[Apollo XX]

So the sun did mostly come out for the time period around this predicted transit, and I drove to a spot at least closer to the centerline and saw nada. Did you notice that the prediction changed dramatically in the days since the original post? Yesterday it was showing the line of visibility somewhere out over the Atlantic. Males me wonder if the ISS had done an orbit adjustment in the meantime.