Yes, Peter. You can test during the day with a Neon bulb at a distance.
RSpec has the Neon lines available on the Elements screen. There are a lot of lines, but do a two point calibration by focusing your attention on the two strongest, one at either end, as shown in the image below from the Walker Atlas (which is no longer available.)
http://www.rspec-astro.com/download/neon.png