Illuminated Polar Scope for AVX Mounts

[goldfishrock]

Having recently bought a Polar Scope for my AVX mount and quickly realising it’s one glaring design flaw, the lack of illumination, I decided to have a go at building my own illuminator that was quick and easy to use. I know there are several of these mods already out there….. but where’s the fun in that! I formulated a design in my head and after a few days and nights of mental refining, I decided how I was going to do it. I wanted it to be simple, just an on/off switch and the ability to dim the LED. I didn’t want any more wires dangling from the scope so the whole unit had to be self-contained and powered by 2xAA batteries.
 
Components used

Clockwise from top left: 4AA Battery Box with On/Off Switch. 12mm Threaded Running Nipple, 32mm Push Fit Socket Plug, 5k Linear Potentiometer + Knob, Wired 3mm Red LED (includes the resistor)
 
 
Stage 1
First, using a 25mm hole saw I removed the blanking part of the plug to produce a hole all the way through. Then, using a junior hacksaw, removed part of the flange and cleaned it up with a file until it was flush with the edge of the plug itself. I then drilled a 12mm hole in the side of the plug and screwed the brass barrel into it until it was flush with the inside of the hole.
 

 
 
Stage 2
Putting the plug aside, I turned my attention to the battery box. The reason I chose a four battery version was I actually wanted to use two of the battery spaces for components. I identified that I would put batteries in the first two slots behind the switch. First thing was to drill a 7mm hole where the potentiometer was to go and then a 12mm hole though one side of the box. I did this at the opposite side to the switch so they were in the areas not occupied by batteries.
 

 
 
Stage 3
Opening the box, I now set to work with a Stanley knife and a pair of flat nosed pliers removing the thin piece of plastic that normally separates two of the batteries. 
 

 
 
Stage 4
I also removed the redundant contacts. I de-soldered the red wire from the old contact and soldered it onto the second contact (which I cut in half to remove the half that wasn’t being used).
 

 
 
Stage 5
Now I fitted the Potentiometer (removing the third wire that I wasn’t going to use)
 

 
 
Stage 6
Time to solder! I connected the negative from the battery box and soldered it to, what was, the centre pin of the pot….. of course forgetting to thread the heat shrink tube over the wire first!!! After de-soldering to allow me to apply the heat shrink tube and putting it back together I then connected the remaining wire from the pot to the negative lead to the LED, and finally the positive from the battery box to the positive of the LED.
 

 
 
Stage 7
Quick test of the circuit before I shrink the heat shrink tubing (oh yes, I’ve been caught with that one before too!) and it’s working well.
 

 
 
Stage 8
Apply some heat from my trusty Dremel Versatip to shrink the shrink and I think we’re done.
 

 
 
Stage 9
Final reassembly. The wire was stiff enough to allow me not to fix the LED. I thought that until I know exactly how it’s going to perform I would leave it free-floating to allow for adjustment.
 

 
 
Fitted to the scope.
 

 
In case anyone else fancies a go at this one, here’s the shopping List:
 
Battery Box:    http://www.ebay.co.uk/itm/141317432725
Brass Nipple:   http://www.ebay.co.uk/itm/111648033612
32mm Plug:     http://www.toolstation.com/shop/Plumbing/d20/Push+Fit+Waste/sd2886/Push+Fit+Socket+Plug/p46510
5k POT:          http://www.ebay.co.uk/itm/252008294420
Red LED:        http://www.ebay.co.uk/itm/140987464344 
 
Total cost of parts: £9
 
Now I just need some clear weather to try it out!!