[Aavso-photometry] Halogen lamps for flats

[Wolfgang Renz]

Hello

Just out of interest:
What are your light boxes made off ?
Foam core ? Ply wood ? Metal ?

Do the halogen and incandescent bulbs not get too hot when oper-
ated at the nominal voltage for a longer time ?

As halogen lamps need a certain pretty high temperature on the in-
side of the glas bulb to operate as intended, they might get really
very hot (> 300° C), hotter than usual incandescent bulbs (especially
if these are operated at a lower than nominal voltage). This temper-
ature should be also high enough to inflame most materials com-
monly used in light boxes if the surrounding of the bulbs is not activly
cooled somehow.

If the lamps have not enough output in the NUV one might still make
diffused sky flats of a few seconds right after sun set or right before
sun rise and use the light box just for BVRcIc flats.

Clear skies
 Wolfgang

-- 
Wolfgang Renz, Karlsruhe, Germany



----- Original Message ----- 
From: "Barbara G. Harris"
To: "Brad Walter"; <aavso-photometry at mira.aavso.org>
Sent: Sunday, April 12, 2009 6:45 PM
Subject: Re: [Aavso-photometry] Halogen lamps for flats

> I would think that you would need to take the filter off to get U flats (but
> I would wait for others to answer).  How many lumens will that 20 watt
> halogen lamp put out?  How many are you using?  I have a large light
> box for my 16" Meade SCT(I don't remember the exact dimensions of
> the box) but I use 4 15 watt incandescent bulbs in my light box with a
> rheostat to take all of my flats except for the I filter, then I switch over to
> 7.5 watts.  The 15 watt bulb is 110 lumens and the 7.5 watt puts out 55
> lumens.  Usually halogen lamps are more efficient and require a lower
> wattage than an incandescent light to get the same light output.  I usually
> shoot for 5 sec flats and adjust my light output to get a 5 min flat at about
> 40% full well.
> 
> 
> 
> -----Original Message-----
> From: aavso-photometry-bounces at aavso.org On Behalf Of Brad Walter
> Sent: Sunday, April 12, 2009 12:10 PM
> To: aavso-photometry at mira.aavso.org
> Subject: [Aavso-photometry] Halogen lamps for flats
> 
> I am about ready to mount some 20 watt halogen lamps in a new light box.
> The fixtures include a UV filter which is required for normal household use.
> Do I want to leave the UV filters in or take them out? My inclination is to
> take them out since I want to use the light box for the full UBVRI spectrum
> and the spectrum of a "halogen bulb in a desk lamp, which would normally
> have the filter in place, rolls off sharply above 500 nm as shown on the
> ledmuseum.org website.