Instructables
While stuyding astronomy charts you don't want to ruin your night vision with those white lights so here is simple flashlight which will preserve your night vision.Our astronomy flashlight uses red LED's instead of white which will help you to preserve your night vision , it is rechargable and you can control the brigthness of the light according to your need.This is a simple and fun to do project.

This instructables explains how to create your own astronomy flashlight , test it  and making some changes to it.
 
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Step 1: Parts & Tools

Parts:
~ 5 x RedLED's - Local Electronics Store
~ BC635 Transistor - Local Electronics Store
~ 5.6 Ohm Resistor - Local Electronics Store
~ 270 Ohm Resistor - Local Electronics Store
~ NIMH Rechargeable Batteries(3.6v)  - Got Mine From A Old Cordless Phone 

Tools:
~ Soldering Iron - Sparkfun.com
~ Solder Wire - Sparkfun.com
~ Jumper Wires -Sparkfun.com
~ Protoboard - Sparkfun.com
~ A Small Container - I Found The Container At My Place

The cost would be around 5$ excluding the batteries and tools

Step 2: Build The Charging Circuit

Our flashlight can be recharged using the USB port of any Laptop Or PC.The circuit to achieve this is quiet simple it has only a single transistor and a few other components.The circuit relies on the fact that the current flow through a transistor is virtually the same in the collector as it is in the emitter.You can solder the circuit on a protoboard as I did or you could just do it without using anything.The LED in the circuit only lights up when the batteries are connected and charging.I have added the schematic (See last image)
what is the function of that in studying astronomy??
you use a red flashlight for astronomy because the red doesn't effect your night vision. If you ever go to a "star party" where there a bunch of telescopes you will get yelled out if you use a regular flashlight. especially if anyone is doing astrophotography. a regular flashlight will ruin any photographs, which can take hours.
ok! wait are a astronomer?
Paulbacca1 year ago
Nice! I will definitely make one of these. I'm also considering a couple of astronomy Ible's of my own. A solar filter and a motor drive for my Dobsonian.
nice! I image that it's difficult to find a red rechargeable flashlight. This is a good solution.
Awesome project! I didn't know red led lights would help perserve your night vision; good to know :)