Photography of two or more simultaneous Iridium Flares

hi folks,

following on Anthony's article in the most recent edition of Arcturus, there is a chance to photograph two very bright flares in the wee hours of April 20/21 within 20 seconds of each other (mags. -7 and -.

the prediction from the Heavens-Above.com website indicates that you need to be sited in a place called Newtown on the Kildare/Meath border (just west of Kilcock) at 02:44 (BST).

not sure if anyone wants to give it a bash or whether just to keep an eye out for similar scenarios at a more reasonable hour -- as we get closer to the Summer the number of flares visible in a period should increase as twilight persists.

a trio of flares is much rarer -- trios were easier to snare when the satellites were first launched and still being positioned into their regular orbits.

the above predictions could still change though if any of the satellites are moved or if the elements are updated in the next few days. It's best to check closer to the 20th/21st for the latest details.

best,

John Flannery,
SDAS

Mmmm, interesting... they would be almost on top of each other given the az/alt. I'm about 15km from the center and Heavens-Above predicts -4 mag from my location. Likely still viable from 30 or 40 kms from the center.

Pity my digi-camera will only do 15 seconds but 2 exposures super-imposed would probably do the trick.

Worth a go if the weathers good.

Thanks John,
Worth travelling a few miles for a dark sky if its clear.

there is a chance to photograph two very bright flares in the wee hours of April 20/21 within 20 seconds of each other (mags. -7 and -.

the prediction indicates that you need to be sited in a place called Newtown on the Kildare/Meath border (just west of Kilcock) at 02:44

the above predictions could still change though if any of the satellites are moved or if the elements are updated in the next few days. It's best to check closer to the 20th/21st for the latest details.

best,

John Flannery,
SDAS

Further to John's post for this rare event, here are some updated details for tonight: (hope it comes out ok - it would be handy to have a table function here! )

Date Time Mag Azimuth Distance to flare centre
20 Apr 21:13 -0 32° 348° (NNW) 31.9 km (W) Iridium 95
20 Apr 21:14 -4 33° 350° (N ) 11.2 km (E) Iridium 31
21 Apr 00:00 -1 26° 253° (WSW) 68.7 km (E) Iridium 61
21 Apr 00:09 -0 22° 255° (WSW) 85.6 km (W) Iridium 19
21 Apr 04:32 -1 52° 268° (W ) 36.7 km (W) Iridium 63

The Distance to flare values actually refers to a large base between the 2 points for the almost simultaneously occuring flares at 21:14hrs. These values are for an observer in Tullamore. Therefore, the first can be seen32km West of Tullamore, and the second 11 km East - thats a broad base, but both should be seen within and around this baseline.

Azimuth: This is the direction of a celestial object, measured clockwise around the observer's horizon from north. So an object due north has an azimuth of 0°, one due east 90°, south 180° and west 270°. Azimuth and altitude are usually used together to give the direction of an object in the topocentric coordinate system.
Altitude: The angle of a celestial object measured upwards from the observer's horizon. Thus, an object on the horizon has an altitude of 0° and one directly overhead has an altitude of 90°. Negative values for the altitude mean that the object is below the horizon. Altitude is usually used together with azimuth to give the direction of an object in the topocentric coordinate system.



Might be a good opportunity for film photographers to try photographing the Iridium streaks by leaving the shutter open on e.g a 2 minute exposure. There will be very little star trailing in this time frame, and the flares should be bright enough to come out on the film.

Now for the weather...

Cheers,

Seanie.

hi Sean,

very interesting . . . your predictions for Tullamore show two mid-evening flares very closely spaced in time which are different to the ones I dug out for Newtown (early am). As you said, I don't think the weather will cooperate tonight unfortunately.

I wonder is there some way to do a scan of many points on a virtual map using the Iridium orbital elements and identify forthcoming interesting flare events for all of Ireland? The differences in your predictions and the ones for near Kilcock show how localised the flares can actually be.

John

I wonder is there some way to do a scan of many points on a virtual map using the Iridium orbital elements and identify forthcoming interesting flare events for all of Ireland?

It sounds theoretically possible...

Iridium TLE's are at celestrak.com/NORAD/elements/iridium.txt if anyone understands the prediction maths!

Cheers,
~Al