the £5 telescope

Sooooo - haven't posted in a while, but I think this one will be the first of many in the near future.

The title is true (approximately), on the day I built the telescope I spent less than £3.50 - but I already had convenient tubing and tape lying around.

Long story short, I decided to have a rather strong coffee on Tuesday morning and that evening, having buzzed around all day, I had built myself a 75mm aperture refracting telescope. Why? Well I have always enjoyed looking through my dad's telescope back home, pointing it at Jupiter, Venus, Mars, the moon and whatever else happened to be along my line of sight. I have been having withdrawal symptoms ever since coming to uni, but my recently completed work for the ESA "fly a rocket program" (more on that in another post) tipped me over the edge.

How did I do it? Search up refracting telescope on google and you will get all sorts of lovely diagrams, adverts, pictures and links to educational websites. Trawling through this lot left me with two impressions: 1. Whatever I built wasn't going to produce pretty images - the colours would blur away from the centre of the image, the image would be flipped and shapes may end up distorted as well. 2. Magnification is done at the eyepiece (the place where your eye goes) - a good goal for the main telescope-y bit is to get it as large as possible, both in diameter (to get as much light), and length (as this counters 1.), but these are both limited by the lenses you use.
Off I went to find a nice big lens to put at the front of my telescope, the correct name for this lens is the 'objective'. Hundreds of years of gradual improvements to telescope design started pretty much immediately by getting rid of the standard convex lens as the objective, instead using all sorts of wonderful shapes to limit colour blurring.

HA HA HA. 

75p later I have myself the greatest abomination of an objective lens in the form of a wilco magnifying glass. At 75mm across it is not the biggest lens, but it is a lot bigger than my eye which is actually the important bit. Another ~£1.50 later and I have myself a pair of small binoculars from a charity store, ready to be killed and resurrected as my eyepiece. None of this is going to work fantastically, but all I want to do is not have only my eyes to look at the stars with.

So having spent the entire day polishing my new objective lens I rushed home to begin construction!! The key thing I was concerned about with the focal length of each of my lenses (including the ones from my binoculars). This simply involved pointing a lamp into the lens from a long way away, and then looking to see where the image came out clearly on the other side:

As you can see I had lots of fun with little pieces of tape, the first black piece after the big lens marks the focal length of that lens while the white pieces were used to measure the distance from the target to my eye.

One of the key mistakes I made at this point was to check for magnification. This being my first recent foray into optics, I really didn't want to manage to make an incredibly convoluted way of looking through a cardboard tube, with all benefits brought by the lenses cancelled in some way. As all I wanted to do was see some of my favourite nighttime targets a bit more precisely, I didn't really care how much magnification I got, simply that it was more than none. Thus I spent ages with the white bits of tape, checking angular sizes of things with and without the lenses, only to realise later that magnification comes primarily from the eyepiece, which usually like to sit very near the focus of the scope - which simplified the design immensely.

Construction was very simple:

1. Take cardboard and cut section off with  a length corresponding to the focal length of your objective lens, I tried with a slightly longer tube to begin with but this did not work at all.
2. Cut another much shorter section of cardboard to act as a light shield in front of your objective lens.
3. I then added slightly smaller rings of cardboard inside the two sections at the ends where I was going to put my objective lens to help mount the objective lens and keep it still once the telescope was complete.
4. Then tape the cardboard sections together with the objective lens between them.
5. Now we need to have some sort of mounting for our eyepiece (s). Looking around the web you can see that most mountings allow for the eyepiece to move towards and away from the objective lens to help focus the output image. I took a ring of cardboard with a diameter such that a toilet paper roll could slide through it. I then took a convenient object matching the cross section of my main tube (the end of the tube for when it was a postage tube), cut a hole at its center with a diameter corresponding to my loo paper roll collar, then taped the collar into this hole.
6. Bodge an eyepiece. I am still doing this. Actually looking at eyepiece layouts was a good start, I eventually opted for a Ramsden configuration as this was the best I could do with the lenses available...
   

My conclusions...

£5 for any telescope would be good, but building it has meant that instead of a rubbishy kids second hand novelty scope I have ended up with a passable scope with an alright aperture and plenty of potential. At the moment the telescope mainly just focuses images, without enhancing them too much, but with some more lenses (and a bit of practice) I think that new eyepieces would drastically improve the telescope's performance. The dodgy objective lens reduces the potential utility of the scope: colour bleed and image distortion are utterly pathetic, and this project is missing the crucial element of any true telescope - the mount.

I envision many happy evenings spent looking at random celestial objects with the telescope, but in reality I think my efforts in telescope building may have only just begun...

Lunar Rover progress update

Been a while but here we go!!

So progress on the lunar rover project has been reflective of the once a week meetings - as predicted the comms team merged with control (although there was a proposal to spin off power into its own team).

One of the problems we are facing is that we cannot easily define the boundaries of each team so early in the project. Ideally communications would build the talking bit of the robot, how we get information into and out of the robot including commands, sensor data and possibly images. Control will have to deal with how we use this information on board the rover, including making it move and deploy our sensors. Power will be given a big battery, a bunch of required outputs and told to go sit in a corner and design an interface between the two.

The problem arises when the functionality of one section impact on another. The best example here is the communications potentially impacting on the control system by restricting the amount of information we can feed to the rover.

How do we solve this? It will probably be done gradually, as things start to fall into place the required behaviours of each section will become better defined to the point where sub teams can split off to work on separate project areas.

What has actually happened so far? A bunch of rough proposal work, most teams (including the structural teams) have come up with a rough idea of what they are supposed to be doing and passed on the biggest requirements they can think of to everyone else (including the fact that the payload deployment and drive train will probably mean we have to deal with upwards of 6 motors :| ). Within the control/comms/power team we have come up with some basic control system ideas - and how each have to be supported by the communication and power teams. While Raspberry Pi came up as the immediately obvious solution (you can say it is a proven technology and therefore less risky, as well as being easy-ish to use), someone from the control team found a Commercial Off The Shelf (COTS) piloting and control system, a bit pricey but would certainly solve many of our problems at a stroke.

Our next meeting is tomorrow, so ideally there will soon be lots to write about.

3DS Hardmod and Wii Controller Dissassembly

Hi, Andrey over here.

One of my flatmate's Wii Controllers were in quite bad condition after travelling across Asia for a while....

So I took them apart, desoldered the battery contacts and submerged everything but the PCB in soapy water (to remove gunk and alkaline corrotion). Soon I will reassemble them and hopefully there won't be explosions (hehehe).

Also, a couple of weeks ago, I modified my "New 3DS XL" by soldering four wires to the NAND chip test points. The mod allows to copy the firmware directly from the NAND chip by using an SD card reader. With the firmware backed up, many doors for homebrew open up   ͡° ͜ʖ ͡°)

Lunar Rover Part 1

The UK head branch of the 'Students for the Exploration and Development of Space' (SEDS) has announced the 'Lunar Rover Design Competition' for this year! An absolutely awesome challenge to take, our University SEDS branch has now started their entry.

Unsurprisingly my fellow blog masters and I ended up in a team dealing with communications  (and an obvious wink wink that we may be about to take over electronics, power and control as well). 

So, what are the problems facing your lovely electronics if they were lucky enough to go to space, and the moon in particular:

1. This is the biggest: RADIATION. Down here on lovely Earth we have a nice blanket called the atmosphere blocking out all the horrible energy the sun (and space in general) likes to throw around in the form of radiation, both EM and particulate. In space these have a nasty habit of interacting with our electronics, changing logic states, causing voltage levels to fluctuate and so on. There are a whole bunch of fancy names for this, the big ones are 'Single Event Effects' where a single element of radiation causes unpredicted behaviour in our system (like changing a logic value), and the alternative measured with the 'Total Ionising Dose' which refers to transistors becoming unusable after their oxide layers are saturated with radiation induced holes over time. I think this is a really cool area to look at so I will no doubt talk about it at length later.

2.Getting there. So even if we let someone else do the whole rocket/launcher bit, we still have to deal with the environment experienced during launch. This is so important that they are actually making the rovers undergo a vibration test for the competition. The effects of this are fairly intuitive, any dodgy solder joints or loose connections will just wobble loose and ruin our day.

3. Temperature. The other lovely thing about our atmosphere is that it keeps everything at about the same temperature (although during winter it doesn't feel like it). To put it into perspective the maximum temperature range at Kew in London (record high to record low) is around 29°C. On the moon this is 290°C. Additionally, once we are in the vacuum there is no lovely air convection to take your heat away. This all adds up to produce concerns which we really don't have to worry about on the ground such as conductance changes and material fatigue (due to heat expensions and contractions.

4. They are a long way away. If your electronics/electrical systems fail terminally then you can't go and kick them (or the equivalent) until they restart, the Hubble Space Telescope being a notable exception. Failures in space need to be dealt with before they happen usually by exhaustive analysis and sneaky design.

5. Dust. Moon dust is pointy, with only solar radiation to break it down grains, unlike the many weathering effects we have down here, they retain sharp edges which can be really rather problematic when those edges start to point at your electro mechanical components.

I have not even scratched the surface here, I imagine that rewriting this article in 8 months time would be an amusing exercise after actually facing these problems.

Just One More Resistor Begins...

Here we go!

So, why the blog?
Well, to display some of the insanely cool projects I have managed to throw together (mainly with others) after only a year of studying Electrical and Electronic engineering (time period growing as we go on).

For example, after only 6 months of electronic goodness myself and three others attempted to make a radio telescope as an entry into a 24 hour hackathon. I actually wrote a post somewhere else (here). Surprisingly we did not do too badly, we were not able to get a high enough angular resolution and the weather on the day prevented us from taking it outside and pointing it at the largest object we could find (the sun).

Other projects included an antweight robot wars entry, and a model rocket accelerometer payload.

Coming in the near future are more robots (including fun with servos), and possibly an internet connected coffee machine...