EQ3-2 polar scope illuminator

[JamesF]

Spurred on by other people's designs (mostly for EQ5s, I think) that have been posted here, I decided to make my own polar scope illuminator for my EQ3-2.

The polar scope "window" on my EQ3-2 is 35mm diameter. I couldn't find anything that would fit perfectly, but I had some 32mm waste pipe which is 36mm outside diameter so sanded the end of a piece down to a taper which would fit snugly into the window. I also bought (the horror!) a 32mm waste solvent weld tee and access plug:

I was planning on using a standard end cap, but the local builders merchants didn't have any in stock and actually the access plug probably worked out easier in the end.

To try to make the illuminator as short as possible I cut down the socket on the bottom of the tee to about 10mm and glued a section of the tapered pipe into it, having marked where it came to when inserted into the mount.

The access plug had a seal that I removed and some ridges on the top that I cut off with a hacksaw and sanded down. I then drilled a hole through the centre and fitted a power connector with a 5V LED (with a combined resistor) soldered directly onto the terminals. I planned to power the LED from a disused 3.7V Nokia phone charger, though I'd imagine it would work fine from three 1.5V batteries.

The plug body goes into the side of the tee, and the cap is screwed in so the LED just reaches the junction:

And here it is on the scope:

I went out this evening and set the tripod and mount up. There's enough light to see the reticle without making Polaris difficult to see and I have to say it's the easiest polar alignment I've ever done both in terms of accuracy and speed. It always used to be a real pain trying to adjust the mount one-handed whilst getting enough light from my torch down the tube to light the reticle without drowning out Polaris. Tonight it was almost a pleasure to do.

James

Edited February 12, 2012 by JamesF

[Gina]

Nice one

[Mav359]

Hi James

Loving this so i went out to buy the connectors and bought this...

Size N Coaxial DC Power Jack W/Switch on eBay!

How did you know which of the three prongs to solder the LED too?

[JamesF]

I checked with a meter

On my socket there was one prong for the centre pin, one for the sleeve and one that was connected to the second when the power plug was removed (so it can disconnect a battery with the power plug inserted and reconnect it when removed). With the socket prongs facing you, arranged left, top and right, the leftmost was the centre pin, top was the sleeve and right was the switched line. Looking at the image on the ebay page, I'd guess yours was the same.

If I recall correctly that means that the "long" leg of the LED goes to the left prong, and the shorter leg to the top. If you connect it the wrong way around it shouldn't hurt, but obviously it won't work.

James

[S.A.M]

Nice Mod, well done. Might try and make one for myself?

Peter

[JamesF]

I'm really pleased with it. It now takes me about thirty seconds to align the mount whereas before it was so fiddly and I used to hate all the faff. I was contemplating adding a polar scope camera, but now it's so easy I can't see the point.

It may take a little fiddling to get the LED to a position where you have enough, but not too much, light illuminating the reticle. That may take some experimentation when you can see Polaris and depend on your local sky conditions. As I have mine it's probably the absolute minimum I could get away with, but I couldn't be bothered to saw a few mm off the ends of the tee and cap so it would go in further

What might have been neat to add would be a variable resistance inline with the LED to allow the brightness to be changed, but as it worked for me the first time I tested it wired up as it is, I didn't bother.

James

[Mav359]

My skies are in heavy LP, that said i only need a touch of red light just to make that bit easier.

Ive only had to by the socket and matching jack, my dads a plumber so the 1.25" Sweeping T & end stop were only a matter of raiding his van, likwise for the liquid weld, I'm not much of a solderer (learning) though.

Great mod though, looking forward to finishing and using it

[DannyHarvey]

James,

I'm going to give one of these a go. Just tried my polar webcam tonight and I couldn't see any of the reticule....

Dan

[Gogleddgazer]

Having singularly failed to get anywhere with a non-illuminated polar scope, this is now top of my list of projects, particulalry as the Skywatcher illuminatornks £30 and not available right now!