Paul M

I enjoyed both films because I like escapism. At least now, if called upon, I think I could manage to get home in a Soyuz lifeboat "Gravity" did absolutely flout the laws of physics. Whereas with "Interstellar", well, you just don't know what you don't know. It would be a physical impossibility for me to fly off through some black hole and return to find my daughter is 50 years older than me. But only because I don't have a daughter!

This tracker here might help: http://www.isstracker.com/ The circle round the ISS icon represents the horizon of visibility. So in theory, ignoring the observers local limitations, anyone on the ground within that circle should have ISS above their horizon. I just had a look at tonight's late evening pass with SkySafari and it tells me that when ISS is about 15 deg above my west horizon its' just under 1200km distant yet at 5 deg elevation it's 1800km distant! Which puts it way off over the Atlantic.

ISS is a great one to watch for this effect. Take last nights high pass, potentially visible from horizon to horizon. When it first appears in the west it seems almost stationary. Most of it's movement is towards you (radial). As it gets closer more of it's motion is across your line of sight (angular). When overhead or "abeam" (ISS never goes overhead up here) all its motion is angular. You see the full effect of it's 17000 miles per hour orbital velocity. As it recedes everything is in reverse. Until eventually it's almost stationary as it fades on your easterly horizon. The change in apparent speed is smooth and steady. Nothing to do with flight dynamics or anything. It's entirely a visual perspective effect. Should an object change its apparent speed abruptly or change it's path in any way it is almost certainly within the atmosphere under powered flight. The only orbital parameter that the space shuttle could change significantly whilst in orbit was it's altitude (and thus its orbital period). To rendezvous with ISS the shuttle had to be launched in a fairly narrow window as ISS's orbital plane passed overhead. The shuttle was then effectively fired at it like a bullet. All the directional adjustments to ensure correct orbital insertion were done with the engines while in the atmosphere. Once in orbit all the shuttle had to do, and could do, was play catch up and dock. Then to come home, it would turn blunt end forwards and fire its thrusters in the direction of travel to "de-orbit" . Again, no significant directional control was possible until back in the atmosphere when aerodynamics came into play and the wings did all the work. These limitations (on any orbiting craft) are why the crew of Space Shuttle Columbia could not take refuge on ISS even if they had been aware of the damaged wing on that fateful mission. That flight was not in ISS's orbital plane and there was no way of getting there.

Here is my contribution: Another 250 PDS, seen here at it's unboxing ceremony in my back yard. Taken at local midnight. The light pollution casts shadows round here And here is Ye Olde Fullerscop. 6.25in I still have a great fondness of this old girl. She's got charterer! I know, that Mk III mount is in a sorry state. I don't suppose I'll ever get round to fettling it. It lives outside under a tarp in the Cumbrian countryside but that's not how it got in that state Anyway, it still holds the scope very securely.

I remember thumbing through old and borrowed copies of Sky & Telescope as a boy and drooling over the Questar adverts. Never have got close to owning one but if I did I think it would live in a display cabinet in the lounge. Arguably the most attractive optical instrument in the world...

I don't think there is any need to use a telescope to capture images or video. It would be very useful to see some straight forward, wide angle, real time video that simply shows the object traversing the sky. That will help everyone decide on the nature of the object. My best guess would still be aircraft landing lights, although you would normally only see those while an aircraft approaches. I get them a lot round here. Aircraft arriving into crowded UK airspace from their Atlantic crossings or while transiting the airspace around Manchester Airport occasionally switch on their landing lights while still at altitude as an extra aid to being seen and being safe. The lights can be bright enough to overpower any coloured navigation lights and even anti-collision strobes. But they usually disappear as the aircraft passes overhead or abeam. The fact that you see the object quite frequently would imply that it's maybe not as exotic as it might seem. Is the path a geodesic? Is there some directional change? Does it always rise and set in the same part of the sky? Video would help answer those questions. A "fresh pair of eyes" as we call it round here