The compact fluorescent light bulbs in the study work well for calibrating the spectrometers – providing good range of sharp lines across the range of the spectrometers.
However it is located in the study on a tall lamp stand and is not very portable.
Hence I purchased this small desk light for the purpose. The compact fluorescent bulbs turned out to be difficult to find as they are now outdated and replaced with LEDs. However, Wilkes had some on sale – I have tested the spectra of both old and new bulbs to ensure they match on principal lines and the match is virtually exact – see pictures below.
Great thing about this new light is that I can take it easily out into the field for calibrating telescope outside. Does need 240V but Ed’s marvellous battery box provides that – so no problems there.
Existing calibration light in study on tall stand and new portable desk light – bulbs in both are compact fluorescent lights:
CCDSPEC spectra of both types of bulb – amazing how similar they are given different manufacturers and bulb numbers. The wider peaks on the new bulb is due to over-saturation as the bulb is very bright and I was taking the spectra with CCDSPEC only 50cm away from the bulb. In practice this won’t be an issue as long as light placed some distance away. I may also purchase something to act as diffuser in front of light:
New CFL on small black flexible desk lamp base: