The Mapstar chart light

[mapstar]

Hi all,

Having looked all over for a chart light for those long star hopping session I have planned (hopefully) later in the year I couldn't find what I wanted.

I wanted a chart light that did not disturb others and also had the same field of view as my 9x50 RACI. Rechargable and capable of being dimmed. 

So it was to the workshop to build something that fits the bill. A piece of 24mm ply and some Carbon fibre sheet offcuts would fit the bill. 

I managed to find some frosted perspex tube the same diameter as my finder field of view at 64mm which would be illuminated by a strip LEDs from behind.

Heres the ply and the carbon fibre cut and glued together ready for a bit of trimming.

And after it was trimmed around using a laminate trim bit in the router table.

So I then had to fill it with electronics. So in went a 12v lithium ion battery, a charge socket, LED controller, a switch and a variable resistor to dim the srip of LEDs around the perspex.

Here's the switch and resistor mounted.

 

It was a proper squeeze to get everything  in and I added a 500mA fuse just to keep it all safe soldered to the battery terminal.

So after it was all packed in I glued the bottom sheet of carbon fibre on making sure everything was well insulated.

Next post it all finished ready for a good star chart session.

 

[Demon Barber]

And i thought Yorkshire folk were thrifty!

You`ve upped the bar again,nice job 

Regards

Mike

[mapstar]

With the bottom glued on it was a return to the router for trimming.

A quick clean up with some fine glass paper and black stain for the ply it was complete.

And in its correct orientation 

And just to test it with the LEDs dimmed and on full.

Just need some dark clear skies to give it a proper run out 

Cheers 

[mapstar]

7 minutes ago, Demon Barber said:

And i thought Yorkshire folk were thrifty!

You`ve upped the bar again,nice job 

Regards

Mike

Just a few scraps out of the garage Mike So hit the nail on its thrifty head 

[Lorne]

May I suggest the round hole be filled with a magnifying lens of sorts for us "eyes not as good as they used to be" types! ?

[mapstar]

Hopefully the round hole will fill my scope with galaxies 

[cjdawson]

That's awesome.  How long does the battery last when it's on full blast and in the fridge?  All night I hope.

[mapstar]

20 minutes ago, cjdawson said:

That's awesome.  How long does the battery last when it's on full blast and in the fridge?  All night I hope.

Cheers

I've not tested it yet but on calcs it should last at least 10hrs at max output which will be very rare as it will be at minimum for dark adaption.

I will have to see as the temperature drops. 

It took just over 30mins to recharge so would be great to recharge during a break from observing. 

[michaelmorris]

That is one seriously nifty piece of kit you've built. Excellent.

[mapstar]

52 minutes ago, michaelmorris said:

That is one seriously nifty piece of kit you've built. Excellent.

Cheers michael. Hard to get it compact but it's turned out o.k. thanks for looking at it 

[mapstar]

An update on this if anyone was wondering about the longevity.

I put the battery through a full charge cycle and set the LEDs to their lowest level. 

So far the chart light has been on for 36hours and still going. Eventually it will just cut out but it would do for a star party where you dont have electric hook up for at least 4 nights viewing. 

The camera actually brightens the image somewhat. But works lovely not as though the skies are dark or cloud free enough to give it a true test.

[Stardust Dave]

Id think without a aperture stop of sorts those led lights would be in your direct vision while dark adapted . 

Guess the object type and magnitude would determine whether an issue.

I find any direct led ight hampers my chart  to eyepiece transition , may just be me.

Or is the hole conical and we are looking at the bottom side facing up in last pic?

Looks very professional !

 

 

[mapstar]

9 minutes ago, Stardust Dave said:

Id think without a aperture stop of sorts those led lights would be in your direct vision while dark adapted . 

Guess the object type and magnitude would determine whether an issue.

I find any direct led ight hampers my chart  to eyepiece transition , may just be me.

Or is the hole conical and we are looking at the bottom side facing up in last pic?

Looks very professional !

 

 

The camera brightens the LEDs quite a bit so it's not a true reflection of how dim they are.

The tube inside is not conical and I agree that direct light could affect dark adaption.

It is very much still an experimental prototype and I had thought about blackening the frosted tube about halfway down so that you cannot directly see the LED's.

I'll see how it goes on the first outing. At present the battery life is spot on and the light output. Maybe just a tweak or two to perfect it. 

 

[mapstar]

Hi all,

The battery finally gave out somewhere around 4pm this aft so at 55 hours run time I can safely say it'll probably last next to near a full week at a star party 

So final testing when I get some clear skies and I will report back on the performance.

[mapstar]

Still not had chance to test this but the re-charge time is 1.5hours.

 

[Soupy]

Looks great now it's finished. Excellent work buddy. When is the production line starting?

[mapstar]

3 hours ago, Soupy said:

Looks great now it's finished. Excellent work buddy. When is the production line starting?

Cheers Soupy. Feels like a long time since I've needed a light on the chart

[Soupy]

Season is starting again soon. We are over due some serious EP time.