Has anyone tried measuring beam profile with a light meter?

[Cheesy]

I think it might be possible with a data logger by pulling it across the beam on a bit of string using a Lego winch geared to give an appropriate speed of traverse.

Comments?

Anyone like to try it?

I don't have a light meter ATM or I'd do it myself.

I'm trying to work out if I should get an Extech HD450 for £180/$300 or a Gossen Mavolux 5032C for £500/$900 or neither as I don't really need one.

Anyway, I'd like someone to give it a go while I make up my mind.


Kev.

 

[Citivolus]

I've contemplated beam profiling on my telescope mount while slewing it past the light sensor. I keep saying I'm going to do it, maybe I actually will

If you are serious about trying it and would like to do it on the cheap, around $20 in parts plus a basic ADC (such as a $25 http://www.dataq.com/194.htm ), connected to a spare port on your PC, would be all you would need. The numbers you would get would need to be run through a transform to yield lux, but it isn't difficult to do.

You would need:

1x photocell ($2-5)
3x resistors (to build a wheatstone bridge, see wikipedia)
1x voltage source, optionally regulated (for the run time of your beam profiling regulated wouldn't really be necessary, this circuit isn't high drain). The voltage source needs to be under the voltage range of your ADC, so a lithium battery would be fine.

I personally cheat and use a USB logging meter (uni-t UT71D) rather than the bridge and ADC, but the above is much cheaper to implement.

If you are at all interested, I can post a schematic and some formulas, as well as suggested part numbers.

Regards,
Eric