Sometimes I have - or rather had - difficulties to see the crosshairs of my 8x50 finder, because it simply was too dark to see them.
This was a big nuisance: when imaging I usually 'impale' my object on one of the crosshairs of my finder, so that I can easily re-aim.

My German TAL-2M friend Rudy Prinz found a solution and I copied his approach (with Rudi's approval opf course !!!).

Ingredients (total costs: almost neglectable)
1 Potentiometer 10K
1 Knob
1 Resistor 470 Ohm
1 LED Red 5 mm
1 LED-holder
1 Empty film cannister
some duct tape
1 clothes pin
2 Meters 2-wire cable

The construction is easy: connect the parts as shown in the diagram, tape the LED holder with LED at the clothes pin, with the LED pointing forward.
Put the potentiometer inside the film canister and hook it up to 12 Volt DC.

My first version, work done.
The red clothespin with the LED inside is clipped in my finder scope.

March 2005: I gave the components a new home and replaced the adjustable potentiometer with one of the smaller types that you can adjust with a screwdriver.

I rehoused the same components as used in version 1 and used a PVC fitting.
The components are hidden in a PVC cap which I hotglued to the main PVC part.
The red LED which illuminates the cross hairs.
I should have done a neater job when insulating the contacts of the LED and also the hot glueing lacked patience ...
The PVC shop of course also had a fitting cap.
All I need to do now it to spray it black to give it a more professional appearance.