Contamination of the O I (³P2-¹D2) emission line by the (9-3) band of OHX²II in high-resolution measurements of the night sky

Abstract

The effects of contamination of the O I (³P2–¹D2) line by the rotational lines of the (9–3) band of OH X²Π in high-resolution (Fabry-Perot spectrometer) measurements of the night sky have been investigated and found to be other than negligible and apparently independent of geographical location. Although the effects of OH contamination are never insignificant, they do become relatively small under optimum conditions when the O I line (zenith) emission rate exceeds 150–200 R. Since removal of the contamination is the obvious solution, the advantages and disadvantages of some possible schemes to accomplish this are discussed. The locations of the P1(3) and P2(3) rotational lines of the (9–3) band of OH have been determined, and they are 15,851.404 ± 0.02 K and 15,873.687 ± 0.01 K, respectively. The emission rates associated with these lines are in the range 5–8 R and 2–4 R for the P1(3) and P2(3) lines, respectively, and in agreement for the P1(3) line with previous measurements.