Please help me interpret this ISS transit....

[JB80]

Hi all,

Basically I was checking calsky and discovered that the ISS is going to cross the Sun next weekend very close to home but I have a few questions.

The main one being is how close do I have to be to these coords to still capture the transit?

I mean this one come very close to home, the location on the map is about 3.5km away from me so will I have to go to the location or will I be able to see it from my yard?

And I suppose the second question until I can think of some more is related to the time, calsky shows the local time I believe so 11:24am is my time?(sounds obvious but I want to double check it's not UT or something).

What is the best most accurate clock I can go by?

I wouldn't think the PCs clock is that accurate but it should give me some chance if I'm working on looking 5 minutes either side.

11h42m20.77s

Crosses the disk of Sun. Separation=0.257° Position Angle=25.0°, Position angle vertex=46.9°. Transit duration=0.28s

Angular diameter=41.7" size=109.0m x 73.0m x 27.5m

Satellite at Azimuth=143.6° SE Altitude= 36.1° Distance=663.6 km

In a clock-face concept, the satellite will seem to move toward 7:26

Angular Velocity=29.0'/s

Centerline, closest point →Map: Longitude= 4°31'53"E Latitude=+50°54'51" (WGS84) Distance=3.59 km Azimuth= 25.0° NNE Path direction=114.9° ESE ground speed=7.965 km/s width=8.8 km max. duration=1.1 s

Orbit source: NASA predicted orbit

Then again this is the forecast for the weather so it may all be in vain anyway.

[JB80]

Just checking and two weeks later there is another cross in front of the moon which is just over 4kms away which would be nice to catch too.

[Steve Ward]

Hi ,

The shadow width is 8.8km for this pass so you need to be as close as you can to the centreline to give yourself a fighting chance. . . http://www.calsky.co...0231&mainbody=0

Scroll down for the map and zoom in to pick a spot.

The times indicated in the boxes are local time as far as I'm aware , it was spot on for my shot last week .

The closer you can get the closer the ISS will be to the center of the disc.

Happy hunting.

Steve.

[JB80]

Thanks for the reply Steve,

I haven't seen that page before.

I was going to ask about the width, what exactly does that mean? That you have a 4.4km grace either side of the line?

I can probably make it fairly close to the line but that then will most likely rule out any imaging.

[Steve Ward]

Hi Jarrod ,

If you're at 4.3km you'll see the satellite just clip the limb , but if you're right on the centre line you should see it track across the centre of the disc.

The transit duration time is for a centreline pass , so this will be reduced the further off line you are .

If you can get to image it I would recommend the challenge as visually you'll be lucky to catch it , when I made my lucky capture last week I was watching the screen really carefully but still missed it by eye.

Steve.

[JB80]

Thanks again for the clarification.

That is what I was thinking but I wasn't sure, problem is my laptop is in bad need of a replacement battery so I normally run it off the mains but home is at about 3.5kms away from the centreline so I may be lucky to catch some of it. Hopefully the weather will play ball too.

The lunar one on the 28th may be an option too.

[Steve Ward]

Your battery should last the duration , it crosses the disc in at longest 1.1 seconds , allowing a couple of minutes each side makes 4 mins ,

Practice setting up a few times and make a checklist and you'll be fine on the day , even if the battery only lasts 30 mins . You'll only be running SharpCap or similar .

Alternatively try and find a kindly soul with a socket spare for an hour . . .

Steve.