Skip to main content

Practical astronomy - Where to place the observatory

Following are posts on a practical introduction to astronomy, practical in the sense as to the steps taken before and after observations, practical in the sense that I shall try look at things from an engineering perspective instead of a science perspective.

So, to start, before we look up at the skies, we need to look around on Earth to decide on a place to setup the observatory. How does it matter where we setup the observatory, you ask? Depending on the position of the observatory on Earth, the amount of sky covered by the telescope will differ. You might've come across `all sky' maps, for example the all sky map by the Planck telescope or the all sky map by Fermi telescope. Planck and Fermi are in-space observatories, orbiting the earth while observing the heavens. In contrast, here is the sky coverage of the SDSS telescope, located in New Mexico, USA. As you can clearly see, the SDSS telescope can only cover a portion of the sky whereas the in-orbit telescopes can cover the whole sky. In fact, any telescope on earth will only be able to cover a limited portion of the sky i.e a telescope located in the northern hemisphere will not be able to observe the southern pole star and vice-verse. So, understanding the sky coverage of a telescope is an important factor in deciding where to place it on Earth, especially if the telescope is being built to observe a specific portion of the sky.

Moving on, another fact which most of you would've noticed about observatories on Earth is the fact that all of them are located on tall mountains. The observatories on Mauna Kea, Hawaii, observatories at La Serena, Chile, or our very own Indian observatories at Leh, Ladakh, India to name a few. The reason behind positioning telescopes on top of mountain hills is to reduce atmospheric seeing. Seeing is the phenomenon in which light from stars is distorted by the atmosphere as it passes through it, thereby changing the shape of the star or astronomical object. There is even a qualitative scale used to refer to the amount of seeing. Seeing is primarily due to atmospheric turbulence and the fact that air in the atmosphere is in constant motion. As most of the atmosphere lies within the first few kilometers of the surface, which is also the most turbulent, a telescope atop a mountain experiences lesser seeing than one on the surface. And why is seeing important you ask? In many cases, the smallest object that a telescope can observe is not limited by the instrument or errors but by atmospheric seeing. Therefore, there is only so much we can do to negate the bad effects of atmospheric seeing, using adaptive and active optics.

Depending on the kind of science we intend to extract from the observations, we need to decide on the type of instruments to use on the telescope. Also, depending on our technical prowess, we need to choose one of the many telescope configurations for our setup.









 
source
 



Popular posts from this blog

Animation using GNUPlot

Animation using GNUPlotI've been trying to create an animation depicting a quasar spectrum moving across the 5 SDSS pass bands with respect to redshift. It is important to visualise what emission lines are moving in and out of bands to be able to understand the color-redshift plots and the changes in it.
I've tried doing this using the animate function in matplotlib, python but i wasn't able to make it work - meaning i worked on it for a couple of days and then i gave up, not having found solutions for my problems on the internet.
And then i came across this site, where the gunn-peterson trough and the lyman alpha forest have been depicted - in a beautiful manner. And this got me interested in using js and d3 to do the animations and make it dynamic - using sliders etc.
In the meanwhile, i thought i'd look up and see if there was a way to create animations in gnuplot and whoopdedoo, what do i find but nirvana!

In the image, you see 5 static curves and one dynam…

on MOOCs.

For those of you who don't know, MOOC stands for Massively Open Online Course.

The internet is an awesome thing. It's making education free for all. Well, mostly free. But it's surprising at the width and depth of courses being offered online. And it looks like they are also having an impact on students, especially those from universities that are not top ranked. Students in all parts of the world can now get a first class education experience, thanks to courses offered by Stanford, MIT, Caltech, etc.

I'm talking about MOOCs because one of my new year resolutions is to take online courses, atleast 2 per semester (6 months). And I've chosen the following two courses on edX - Analyzing Big Data with Microsoft R Server and Data Science Essentials for now. I looked at courses on Coursera but I couldn't find any which was worthy and free. There are a lot more MOOC providers out there but let's start here. And I feel like the two courses are relevant to where I …

On programmers.

I just watched this brilliant keynote today. It's a commentary on Programmers and the software development industry/ecosystem as a whole.



I am not going to give you a tl;dr version of the talk because it is a talk that I believe everyone should watch, that everyone should learn from. Instead, I am going to give my own parallel-ish views on programmers and programming.
As pointed out in the talk, there are mythical creatures in the software development industry who are revered as gods. Guido Van Rossum, the creator of Python, was given the title Benevolent Dictator For Life (BDFL). People flock around the creators of popular languages or libraries. They are god-like to most programmers and are treated like gods. By which, I mean to say, we assume they don't have flaws. That they are infallible. That they are perfect.
And alongside this belief in the infallibility of these Gods, we believe that they were born programmers. That programming is something that people are born wit…