Here are spectroscopic and photometric results on Neptune, obtained with a 305 mm Dobsonian and a Star Analyzer. This is the first run of three I have done near opposition. Results are:
1) A reflectance spectrum, calculated with a nearby G0V star
2) A colour spectrum, calculated in flux with a normalized magnitude (planet at 1 AU from Sun, and 1 AU from Earth)
3) Photometric UBVRI magnitudes, with normalized magnitudes.
I have recently modified my synthetic filters to make them more in coherence with the Bessel curves. Colour coefficients have been recalculated, and re-tested on various variable stars, and the results are more accurate than with my previous filters and coefficients.
The results obtained on Neptune look:
- In good coherence with the published ALPO/R.Schmude data for B and V, with especially the expected B-V of +0,4
- Maybe sligthly off for R and I in comparison with the same data, at least judging from the normalized magnitudes. R and I are working fine on stars though.
- Not far from published U values (+8,2/+8,3) but this is maybe just the luck!
The next two runs have been taken with an additional 3,8° prism to correct the chromatic coma of the Star Analyzer. The spectra will be more precise, but I need to re-observe stars to calculate new coefficients before making photometry again.