# Calculating the Velocity of an object far far away

I saw a satellite the other day, it moved very fast through the night sky.

Now I know it took around 110 seconds for it to fully travel out of the night sky(out of my visual bounds assuming, that I'm observing from a flat area), how can I calculate an approximation of the velocity that this object was moving at?

Altitude is going to be a factor in this calculation so let's assume that the altitude is 40.000 feet just like an airplane. How would I go about solving this problem?

I also found this image which illustrates exactly what I'm trying to calculate: The Star in the illustration.

Any help is appreciated, Thanks.

• Anything in orbit that low would instantly burn up, so unless you were watching the last seconds of a satellite's life... Also, you should note the altitude in the diagram is astronomical altitude, not to be confused with the aviation altitude you talk about.
– user10851
Commented May 10, 2016 at 2:48
• i know, i also said "let's assume" Commented May 10, 2016 at 2:58

$$v = \varphi\cdot r/t$$
• All you can calculate is its angular speed, $\frac{\partial \theta}{\partial t}$, to determine its actual speed you need to know how far away the object is, given by $r \frac{\partial \theta}{\partial t}$.