I’ve always been fascinated by the possibility to capture some planets with a cheap webcam. As you can see, I can rely on an entry-level setup that consists in a Sky-Watcher 130/900 telescope on an EQ2 mount. In my experience, mount is as fundamental as the telescope itself, probably much more: as you can see from the picture above, a HEQ5 can provide a better-defined result because it is able to dampen more vibrations than the EQ2.
Many environmentalists are sure that renewable energy would save the planet from disaster. Just yesterday I heard from Science Club on BBC that we should deploy giant solar panels in order to capture all the energy we need from the Sun and say goodbye to pollution, global warming and well drillings throughout the Earth.
Here is Jupiter as seen using a Skywatcher 130/900 telescope, an EQ2 mount, and a Logitech c270 webcam.
I used the usual procedure which consists of shooting a video, then processing the best frames with Registax, and finally applying wavelet sharpening filters (together to other Photoshop tuning). With a bit of imagination you can see two stripes parallel to Jupiter’s equator (in this picture the polar axis is roughly horizontal).
This experiment teaches that the mount is of fundamental importance in amateur astronomy imaging, because the vibrations and the approximative tracking offered by EQ2 can frustrate any effort.
Last year, I decided to put online a website able to transcode (almost) every kind of video format or codec into another (from avi to mkv, from xvid to h.264, and so on); it was called onlinevideotranscoder.com (yes, I admit that my fantasy isn’t very rich), and it had been around the web for some times before I decided to pull off the plug. I still think that an Internet-based video transcoder can be a very useful tool, so here are some lines of code to create it.
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Posted in video coding
Tagged avi, f4v, ffmpeg, flv, h264, hosting, lamp, mkv, mov, php, video, wamp
The underground of Naples has always been an integral part of city life; you can tell from the access to the Bourbon Tunnel (Tunnel Borbonico in Italian), located inside an elegant parking lot in the city center. Even if the citizens sometimes forget this truth, it’s a fact that through the ages the underground served as water supply, source of building materials, illegal dumping, hospitalization during WWII, garage and so on.
In video coding, understanding the real bitrate requirements that correspond to the desired quality is a key feature. It’s possible to assess quality by using appropriate objective metrics such as PSNR and SSIM Index, or simply through subjective methods as the Mean Opinion Score (MOS). Objective metrics are good if the aim is evaluating video coding performances without the pollution of human perceptions; but this is the bad side too: without human perceptions, objective metrics fail to give meaning to their results (numbers are merely numbers). So, subjective evaluation procedures – that simply consist in averaging the scores given by human observers – are fundamental in putting together the perceived video quality and objective evaluations.
As an amateur astronomer, I’ve always been attracted by astrophotography; but, because of light pollution and a poor equipment (just a 130/900 newtonian Skywatcher!), I never went very far from the mere but still exciting visual observation. Now, with remote telescope services available on Internet (like Global Rent a Scope), I just gained the ability to access to darker skies, better equipment and, most of all, to astrophotography.
In this second part, I will show another metric used in video quality evaluation: the Structural SIMilarity Index (SSIM). In the previuos article, we saw that PSNR and MSE are not always reliable in every situation, so we need a more accurate metric that’s able to cover a wider spectrum of distorsions and losses in video information.
With this post I begin a series of articles covering the issue of image and video quality assessment through both objective and subjective methods. Where possible, I will also attach a little piece of Matlab code in order to show a possible implementation of the suggested algorithms.
As an amateur astrophile, I can count on very simple tools – such as a 130/900 Skywatcher Newtonian telescope on an EQ2 mount – that sometimes can seem obscure to a total newbie (or to an occasional observer). So, I decided to write this simple vademecum to read everytime the official manual isn’t available for a reason or another.