Forums / The Science / Visual Observing / Project Idea: Assisted visual photometry as done in the old times
Project Idea: Assisted visual photometry as done in the old times
Hi all,
This is an attempt to float an idea that I presented here before but without much resonance. I still think it's a nice idea for a project, but I'm already involved in three CS teams so I'd rather see this idea adopted by somebody else than see it die of neglect.
Here's the story:
The idea is to improve visual magnitute estimates by using a variable aperture that can be used to reduce the passing light in a well-defined way.
To make a measurement, you would reduce the aperture so that the star is just no longer visible to the human eye. If you do this for your target and your comparison star, you can get a differential measurement: if it takes a 5% longer aperture diameter for your target star to vanish than is required for your comparison star, obviously your target star is 1.05^2 times brighter than your comparison star (or about 0.1 mag).
Unfortunately this is not my own idea :-), it seems that this method was used in the old times of Herschel and Norman Pogson, see this article:
http:
//adsabs.harvard.edu/full/1968ASPL...10..145J
I wonder whether it might be possible, with todays technology, to somehow construct a low-cost "variable transmission aperture gadget" that could be used in this way to improve visual magnitude estimates.
For example, it could rely on a filterwheel of grey filters, some tricky stuff with polarization filters or even a mechanical "light blocking" mechanism, as long as the transmission rate is easy to vary and read from the instrument. It should also work for a wide range of optics (telescopes & binos). I have no idea whether the perfect solution would be something on the eye-piece end or at the aperture of the primary observation instrument.
CS
HBE
Thanks Brian, that would be most interesting. CS HB
Hello again Heintz, The papers are by Harold F. Weaver and consist of a six-part discussion of the development of photometry. They should all be open to the public by now (if not in PDF form, at least in scanned GIF format): http://adsabs.harvard.edu/abs/1946PA.....54..211W http://adsabs.harvard.edu/abs/1946PA.....54..287W http://adsabs.harvard.edu/abs/1946PA.....54..339W http://adsabs.harvard.edu/abs/1946PA.....54..389W http://adsabs.harvard.edu/abs/1946PA.....54..451W http://adsabs.harvard.edu/abs/1946PA.....54..504W
I started reading them a while back and found that they gave a very good discussion up to 1946. He presents a very good discussion of the uncertainties, but he may not cover all of the techniques. I suppose that would be for a team to figure out. Brian
Hi Heinz, I think this is a really great idea. I am particularly interested in the photometric accuracy of devices used in the late 1800s as many of the observers of epsilon Aurigae used "step magnitudes" and devices similar to the one you described above. There were a nice series of articles published on the history of photometry that I have on my desk... I'll look them up and post them here tomorrow. I wonder if Arne is aware of any other people doing similar activities in the pas? Brian