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cheap and easy collimation star


iancandler
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Now I have the C5 I had been lured towards buying some means to make collimation easier. Having invested in a set of bobs knobs already I was leaning towards a pico star but getting scared by the price. ( lasers for shmidts being even more expensive)

To cut a long story short I decided to play at the weekend and drew up a list of parts.

They where:

1 small project box (120mm X 80mm X 35MM plastic )

1 ultra bright LED (3mm)

1 battery clip with bare leads for PP3

a means of channeling the light to a fine point.

I quickly ruled out burning a hole with a hot pin as the resulting star image would be bound to end up irregular and instead whilst ferreting through my drawers chanced upon an optical link cable for my old cd player. Luckily for me it was terminated in 3.5mm jack fittings as well as toslink so I grabbed it.

Construction just involved soldering a 100k resistor to the positive leg of the LED then connecting that via a short piece of wire to the positive battery clip terminal, then conecting the negative leg to the negative side of the battery clip, I plugged in a 9 volt battery and voila! let ther be light.

Next I drilled a 3.5mm hole in the front of the project box and pushed one end of the optical cable through, then secured it in place on the inside with a blob of hot melt glue. I rested the body of the fitting on two self adhesive pads to hold it in place.

I then loosly coiled the cable around the inside of the box and held the coils together with a couple of small cable ties.

next came joining the LED to the end of the cable. I got a small piece of 3mm heat shrink tubing and pushed one end over the 3.5mm optical cable fitting, then cut it so there was just enough to push over the LED. The wires where bent to hold the LED in alignment then I connected the battery and turned the lights out.

It worked.. one bright pinpoint of light on the front of the box.

my brother then took it outside, placing it on the roof of his car some 30 yrds away. I looked through the scope and there was a nice little bright dot of light.. Just what the doctor ordered.

Sadly I only had a blue LED at the time and no switch but they have both been ordered now along with some 270k resistors which will work better with the LED's I have bought in matching them up voltage wise with the battery. Also I needed to get a switch to install to save unscrewing the box to turn it on and off.

This is such a cheap project as the cables can be picked up for under £5, the boxes for around £2-£3 and the LED's,resistors etc are also only a few pounds.

I would say buying everything new it shouldnt cost no more than around £15, quite a saving when you look at the price of the picostar itself.

My brother is also having a go at knocking up a cheap circuit to vary the brightness as LED's only vary in brightness according the current supplied not voltage.

Pics and diagrams will follow as soon as the new version is finished but its looking promising

A couple of quick pics of the original

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Right chaps, what's the minimum distance from 'scope to fibre that you reckon would work? I need a target that I can aim at from the shed, ideally, so I can either nail it to my house or to my tree. The tree is closer so the "star" could be controlled from the shed, but the house has mains power and the "star" could be on a switch indoors.

Excllent project Ian, I'm on the lookout for some fibre optic stuff now.

Anybody know if cable TV runs in fibre, and if the guys would have a few short bits (10M up the tree) lying about in their skip?

Captain Chaos

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I built mine at the weekend, and very well it works too! I had an optical cable lying around from my old sound card, so that got re-used!

The box I used had a battery enclosure built in. My components were from Maplin:

1 x ZB17T (Box) - 3.53

1 x HF28 (PP3 Clip) - 0.33

1 x BF87 (2.5mm Heatshrink 1m) - 1.28

1 x JM69A (1K Pot) - 0.69

1 x GV65 (3mm White LED) - 1.26

1 x FH97 (SPST Ultra mini toggle switch) - 1.47

1 x NC55K (knob for the pot) - 0.55

Costs are ex-vat.

Total cost £10.70 (inc Vat)

I already had a 270 ohm resistor, so I didn't need to buy this again. Be careful with the mini-switches though, they have a tendency to melt the innards if the soldering iron is applied for too long!!!

Cheers for the idea Ian!!

EDIT: I should also say, I have some fibre optic cable left over which I'll cut down to 5" lengths, if anyone wants one. I can probably get 3 lengths out of it. PM if you want one :)

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