today I am finally going to write about my first experience watching ISS, the International Space Station. I have probably seen it before it is just that I did not realize that it is not an airplane.
ISS is a space station (biggest that humanity has) orbiting around 400 kilometers above the sea level. There is lot of interesting stuff about it but in this post, we are going to concern ourselves only with the very simple part, just seeing it.
Do not get too cocky. With naked eye, it will look like a bright star, around the magnitude of Venus at its best. It moves fast and even the best flights above your place will take maximum of about 6 minutes. From my experience, simple binoculars do not make much of a difference, though telescope could and I am yet to see how it will work out with good one, for example if I am able to track it.
Now it might not seem as much but remember, you are seeing the ISS, 150 billion $ project! The upside of it is that the station passes everyday above your place. It will always happen at sunset or sunrise, that is because the station must be sunlit but you have to be already in the shadow of Earth.
Most internet sites will recommend you the NASA webpage but it is horribly done and I will rather link to this one: http://iss.astroviewer.net/observation.php
In the case you are the type of person who uses smart phone, you can also download some app like ISS tracker.
Note: even though ISS will pass over 95% of the world population it has over every place pauses for many days. This is because the Earth is rotating under it and it takes some time before it comes to “phase” again.
today I will write more about telescopes. In a previous post I already mentioned why radio telescopes like Arecibo are so huge, its because of the long wavelength. Today though I will concentrate on another type of telescopes and those are the ones that sit on Earth and collect information from visible light (those are called optical telescopes).
Comparison of various telescopes. Note OWL, the big circle in the background and even bigger white Arecibo.
I already mentioned Hubble telescope and James Webb Telescope (JWT) that is planned for launch next year. Those are in space so they have quite limited size. Down here we can build bigger ones. Right now in building phase is the E-ELT (European Extremely Large Telescope). Its primary mirror will have 39 meters  making it the largest optical telescope. It has to be so big because otherwise it could not match the ones in space. This is because we have our lovely atmosphere in the way and it makes harder for telescopes to distinquish small objects (though these days we have software that is able to account for that).
VLT aka Very Large Telescope is already working optical/infra-red telescope. It consists of 4 telescopes each of them with primary mirror of 8.2 meters in diameter. They can work together to make images of angular resolution 0.001 arcsecond. In one post I said that we are not able to take an image of star other than just point like source of light but apparently that is not true so I apologize for it:
First confirmed image of an exoplanet. The ones that we can see are bigger than Jupiter and usually quite far away from their star. Credit: Gemini Observatory
VLT is second, right behind Hubble in the amount of scientific papers that its work produced (in the field of visible light/infrared telescopes).
There are many other telscopes that I might mention in the future like Thirty Meter Telescope but I will end it with OWL – Overwhelmingly Large Telescope. It was supposed to be the largest telescope ever, with primary mirror of 100 meters! The price was estimated to be about 1.5 billion euro and because of that it was decided that its not worth it. If we do not kill ourselves we might see giants like those in the future though I have no idea how the scientists, or whoever does it, will name them (UGHT – Unimaginably Giantic Huge Telescope).
Just as JWT, the mirror is made from smaller segments. In the case of E-ELT it is because the mirror would be too heavy and we do not have the technology to build it and in the case of JWT it is because you have to somehow get it into orbit.
Comparison of telescopes: By Cmglee – Own workiThe source code of this SVG is valid., CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=33613161