# Arun Waves

## August 2, 2011

### Nice infographic about Solar System and distances involved

Filed under: Astronomy — Arun @ 9:19 pm
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I found this great infographic which gives a mind boggling insight into the distances involved just with in our Solar System. Similar infographics are available in abundance but this one has a new twist in that it shows the distance traveled by light in time scales that we use in our daily lives. The original link of the articles is here. This infographic is a long one so I am posting couple of screenshots to entice you 🙂 You can find the infographic below the screenshots.

PS: The below picture of the Milky Way is an artist’s rendering and not an actual image. To do this we will have to send a probe outside the Milky Way (as of 2011, we have barely managed to send 2 probes out of the Solar System). However this picture is not just wild imagination. We have photographed other galaxies and we have studied (& photographed) our own Milky Way from inside and this picture is a combination of all that knowledge.

Ah … the (below) picture that shows the size of planets and Sun to scale. No matter how often I see this, it always amazes me. All the Sun has to do is send out a little burp and we will simply cease to exist!!

And here is the infographic, you may begin your journey …………… Live Long and Prosper

Source SPACE.com: All about our solar system, outer space and exploration

## July 15, 2011

### Encyclopedia of Astronomy by SAO – COSMOS

Filed under: Astronomy — Arun @ 6:21 pm
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COSMOS – The SAO Encyclopedia of Astronomy” is a great collection of definitions and explanations of astronomy related terms. Wait, it gets better, it is written by research astronomers!! so you get information “directly from the horse’s mouth” which is always the most authentic source.

## June 1, 2011

### Dark Sky viewpoint around Phoenix

Filed under: Astronomy — Arun @ 5:46 pm
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You may scream ARE YOU CRAZY? or more appropriately ARE YOU BLIND? Dark sky in Phoenix, one of the most light polluted cities in continental US!!!!!!!!

Yup I am talking of THE Phoenix in Arizona 🙂 granted it is not the best dark sky location but hey give it some credit for being just 40miles from the city center and you can still see the Andromeda galaxy (M31)

Where to find it ………. head out in a North-Eastern direction on highway 87 (Beeline Hwy), keep going and cross Fort McDowell Road and then Bush Highway, watch for a big green sign saying “Four Peaks *something*” on your right leading to a dirt road; just drive in couple minutes and ta-da you are there.

Here is the board you would see after which you will make a right turn into the dirt road; there will be a cattle guard also.

Don’t believe me!? check out these pics that I took there, see the little light smudge at 2 o’clock position (click the image to go to Flickr and see the notes) …………..

Hey I even took a shot of Perseid meteor shower (click the image to go to Flickr and see the notes) …………..

NOTE: This spot is lonely (depending on the day of the year) and very dark AND you will hear animals that howl, so use common sense and be alert.

## May 21, 2011

### Awesome pics from a blog

Filed under: Astronomy — Arun @ 11:32 am
Tags:

This is what I love about internet and blogs, sitting in my house in Phoenix, Arizona, I can experience a person’s interest who lives in Oak Ridge, Tennessee.

This philosophy professor processes planetary images from various sources and produces amazing pictures of planets and their moons, check it out for yourself, very high quality images, almost surreal views ……………. http://planetimages.blogspot.com/2005_09_01_archive.html

Since Blogpost does not let you link to a specific post I am linking the entire page and this is the topic I want you to look at first, then feel free to explore his blog. Search for “New Color Views of Europa” in the above link and be dazzled 🙂

## May 14, 2011

### What can you see with a 4.5″ telescope? – Ptolemy Cluster (M7)

Filed under: Astronomy — Arun @ 3:45 pm
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Surprise surprise, I woke up at 3am to feed the baby and once I was done I decided to step outside with my 10*50 binocular and voila ……….. there was M7 in all its glory 🙂 I ran back in and got my telescope.

The exciting part was that it was not visible with naked eyes, the light pollution was surprisingly high even at such early hours – suburban skies, what more can I say :mad:. I saw something that looked like the Orion’s belt and in my zeal to view my favorite constellation (actually asterism) using my first telescope, I quickly concluded that it was the Orion’s belt. But a voice deep inside me kept on pointing to contrary evidence like the absence of Betelgeuse or why was Orion’s sword’s center star so bright?! While scanning the alleged Orion’s sword I went off track and chanced upon this high concentration of stars. Immediately I knew that it was a star cluster. Happy with my observation and eager to catch some sleep before the baby wakes up I went to bed. As soon as I got up I looked up the star chart and almost instantly realized my folly, Orion’s belt is not visible during early summer (May) 🙄 So what was it? luckily I remembered the approximate orientation, time and star layout, and it turned out to be …….. M7 – a beautiful open cluster, also known as Ptolemy Cluster. This is the essence of astronomy as a hobby, a chance discovery, seeing things that are not visible with naked eyes.

25mm EP (eyepiece) (36X with a Meade 4400) gave the best view where you could distinguish the cluster’s stars from the overall background stars. The 12.5 mm EP was way too zoomed in to appreciate the cluster and as usual the 4mm was absolutely useless.

As far as pics, I need to see what I can do, esp. since I do not have a tracking mount and anything other than the moon and planets are difficult to image without tracking.

## May 10, 2011

### What can you see with a 4.5″ telescope? – Saturn’s rings

Filed under: Astronomy — Arun @ 9:49 pm
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Today I saw Saturn’s rings. Saturn is very easy to spot with naked eye and at a convenient elevation at 9 pm.

25mm (36X with a Meade 4400) and 12.5mm (73X with a Meade 4400) eyepieces worked just fine but the 4mm (228X with a Meade 4400) eyepiece was very susceptible to vibration, quickly moved out of view, and was blurry due to atmospheric disturbance.

The 25mm eyepiece resolved the planet as a small circle but the rings and its shadow did look like horns on the plant 🙂 The 12.5mm clearly showed the ring around the planet. I also saw a spec of light very close Saturn, I think it is one of the moons but got to confirm it. Neither of them could resolve any surface features on Saturn.

Again my 3X Barlow lens was not of much use since any higher magnification caused blurry images and the subject moved out of view (I do not have tracking mount).

Later I will try to snap a pic 🙂 You know what they say “pics or it did not happen”

PS: Viewing from backyard in the light polluted city of Phoenix, AZ, USA

Pics are not at all good since I was pointing my DSLR on the eyepiece and contorting my body in all possible ways to align with the optical axis, a.k.a. “afocal coupling“. This is pretty much the size that you will get to see with a 12.5mm (73X with a Meade 4400) but it will be much more clear and sharp.

CLICK the pic for better view

CLICK the pic for better view

## April 16, 2011

### What can you see with a 4.5″ telescope? – Moon

Filed under: Astronomy — Arun @ 12:43 pm
Tags: , ,

Today I saw the moon and it was awesome. In a way this is the first light for my telescope even though it is second hand. I could clearly see the mountains, impact craters, lava filled craters, craters with a small peak right in the middle, the dark colored flat regions on the moon, craters within a crater, so on and so forth ……………… 🙂

When I used the 25mm (36X with a Meade 4400) eyepiece, the moon filled the field of view while the 12.5mm (73X with a Meade 4400) eyepiece allowed me to view about half of the moon and more details. The 4mm (228X with a Meade 4400) eyepiece showed only a small fraction of the surface but it enabled me to see numerous surface features. However since I was at a high magnification, the moon moved while I was viewing it and in few seconds I had to realign my telescope. After a while this became irritating and I switched back to 12.5mm eyepiece.

My 3X Barlow lens was not of much use since any magnification at or above 200X causes the moon to quickly move out of view (I do not have tracking mount).

Pics are coming sooonnnnnnnn ………… (if I can manage to aim my DSLR into the eyepiece without smashing my camera’s lens!!)

PS: Viewing from backyard in the light polluted city of Phoenix, AZ, USA

Pics are not at all good since I was pointing my DSLR on the eyepiece and contorting my body in all possible ways to align with the optical axis, a.k.a. “afocal coupling“. This is pretty much the size that you will get to see with a 12.5mm (73X with a Meade 4400) but it will be much more clear and sharp.

CLICK the pic for better view

CLICK the pic for better view

CLICK the pic for better view

## April 1, 2011

### Targets for my Meade 4400 4.5″ reflecting telescope

Filed under: Astronomy — Arun @ 9:14 pm
Tags:

1] Moon

2] Mars

3] Jupiter

4] Saturn

5] any other planets 🙂

6] Andromeda Galaxy (M31)

7] Betelgeuse star

9] Orion nebula (M42)

10] Perseus double cluster

11] M81

12] any comets that might show up!!!!! 😀

Some great links for astro newbies

## July 23, 2010

### Leg-Wheel hybrid for a rover robot: Whegs

Filed under: Robotics — Arun @ 2:05 am
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During one of my exploratory voyages across the vast untamed expanse of the “internet” I made an exciting discovery, Whegs – a wheel-leg hybrid system. First watch this video to get hooked.

Robot designers are constantly on the look out for tricks to get better performance out of their robots. Just like we humans, robots also face obstacles along their way. Now you can detect the obstacle and go around it but there are plenty of occasions where it is advantageous to go over the obstacle. And between you and me, the real reason for the latter options is your robot will be lot more cool and awesome (and bada**) if it can simply go over the obstacles!!

Wheels are great but mother nature decided to give us and many other animals legs, so there must be some advantage to it. Thus millions of years after legs became a way of life and thousands of years after wheels came into being, someone thought, “hey why not mix the two” and the result is Whegs. I found it at this site and this (no time to figure out who came up with it first). Long story short, Whegs climb over taller obstacles when compared to wheels.

Now why is a hybrid design better than the wheel?!?! Here is an illustrative description…..

Consider the above wheel with an obstacle much smaller than the wheel radius (which is the height of the wheel’s center (the black dot) from the floor.

As the robot moves forward (which is ‘left’ in this case), it’s wheel will make contact with the obstacle.

Once a contact has been made, friction will kick in which will force the point of contact to stay the same. Since the torque on the wheel will continue to act, the point of contact acts like a pivot. If the robot’s motor is powerful enough then it will continue turning the wheel, use the pivot point to push down and lift the robot chassis. Eventually this will result in the wheel climbing over the obstacle.

Now imagine a similar condition but this time the obstacle is comparable to the radius of the wheel ($h \approx r$). Once again contact is made but this time the point of contact is on the face of the obstacle and not on top as in the previous case. Although friction kicks in, at this point the friction has to be so high that it should allow the wheel to travel vertically up on the face of the obstacle!! Typically this will not be the scenario and even if the friction is so high, think of how will the wheel let go the point of contact if it tries to move forward (in this case move up); if it wants to roll then it must continuously change the point of contact. Since it fails for this scenario it will fail to work for $h > r$ since the point of contact is always on the face of the obstacle and not on top of it.

Now that we have understood how the wheel works, let us consider the same obstacle vs. a Wheg. For accurate comparison this Wheg has the same radius as the wheel and this particular one is a three legged Wheg. The circle is purely illustrative and is shown for reference only – it does not exist. The first thing that becomes apparent is the large amount of empty space that this structure has and in the following sections we will see how this is used to our advantage.

Since it has empty space where there was a wheel once, this structure can, so to speak, penetrate the obstacle as shown in the above illustration. Remember the circle is just a guide to the eye; it merely shows the trajectory of the three legs. Even if the Wheg started out with the previous position, it will simply slip and eventually get to a position similar to the one showed above.

As this Wheg rolls forward (not as smooth as a wheel though), one of the legs will make a contact with the obstacle and its approach will be from top and not on the face as see in the case of a wheel. As before the torque on the Wheg continues and the leg that makes the contact is used as a pivot to raise the chassis as shown below. PS: Note the illustrative circle digs into the floor because the Wheg moves from one leg to another unlike a wheel which has a continuous contact with the floor.

The above discussion is applicable for taller obstacles also. Thus this hybrid wheel can climb over obstacles that are comparable to the radius of the Wheg 😀 by virtue of it being able to penetrate the obstacle profile and having the leg approach the obstacle from top. So if obstacle climbing is your thing then Wheg is the way to go.

Now let us push the system further – what is the maximum height of the obstacle where even the Wheg fails? Above illustrations shows the maximum height for which this Wheg will work, if the obstacle were any taller then the leg will not be able to rest on its top. Thus the limiting height depends on how high a leg can reach so as to approach the bstacle from top which depends on how deep the Wheg can penetrate the obstacle’s profile. PS: you can achieve more height by reducing the angle between the top two legs but then the Wheg will not be stable, or you can add more legs but then the penetration depth will be reduced.

Now as magical as this may seem, remember, there is no free lunch!! Cons for a Wheg;

• The robot’s ride will be rough
• Slender legs have a tendency to sink into soft/nonrigid surfaces like sand and mud because of reduced contact surface area to the floor
• If things are poking out of a moving part then they tend to get entangled in stuff, like in grass or undergrowth
• If you are really deep into robotics then consider the non-uniform forces that the axle-leg joint will be subject to with every rotation

Happy Robotics 🙂

## June 19, 2010

### Building a Boid system with Processing sketch

Filed under: Boid,code,Object Oriented Programming,Processing,sketch — Arun @ 5:38 pm

Recently I discovered a wonderful open source software, Processing, which is simple to use and great for visualization applications. My first Processing sketch 🙂

http://www.openprocessing.org/visuals/iframe.php?visualID=10494

Click on the above link, it will open a browser (you would need Java in your machine). Once the app starts running, move your mouse pointer within the white square box and try to stay away from the red and the blue balls; for interesting response move your mouse pointer in circles of varying radii. I always wanted to say this……. “You take the blue pill, the story ends. You take the red pill, you stay in wonderland”.

This is my first step towards a Boid code. I wrote this code to learn PVector, vector manipulation and OOP (Class). This sketch creates a system with two elements (balls) that try to catch up to the mouse pointer. These elements bounce off the walls and have different accelerations. Red ball’s acceleration is twice that of the blue ball. To begin with the balls start at random locations and also have a maximum speed limitation.

Screen shot 1

Screen shot 2

Next step would be to make these elements interact with each other while chasing the target, which would make it a Boid code.

Took help from PVector and Objects tutorial @ processing.org
Have fun with the animation. Feel free to comment.

PS: If you want the code then go here.

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