splitting hairs in the backyard on a bonus night of poor seeing

by Richard Crisp

Suddenly about 9pm the skies cleared but the seeing was poor. So I decided to do some long delayed filter testing.

The Crab nebula is a great target for emission line filters because there are so many different things in it. I needed to test my [NII] Halpha set, having just purchased a new 3nm Halpha filter to go with my 3nm [NII] filter.

The [NII] emission is actually a doublet with the typically stronger line at 658.3 nm and the other one at 654.8 nm. Halpha is at 656.3nm so at most there is 2nm separating these two emission lines.

Those are the two that my filters are designed to separate and it was time to put them to the test using the 18" f/12.6 classical cassegrain used with a focal reducer to an effective ratio of f/7.1

When I last attempted to separate the lines I had a different Halpha filter with this [NII] and was using a C14 at f/12.46 so things were a bit different than in this case.

I took three x 20 minutes through each filter binned 2x2. The result is that the lines did in fact separate.

http://www.narrowbandimaging.com/m1_mk1sn2_cm10_geg_cs_n2ha_2x2_page.htm

I started taking [OIII] but only got two frames down before clouds finally shut me down for good. I went ahead and rolled up that data too, sort of as a placeholder for things to come.

http://www.narrowbandimaging.com/m1_mk1sn2_cm10_geg_cs_n2hao3_2x2_page.htm

Posted on sf-bay-tac Nov 26, 2006 15:57:36 PT
Converted by report.pm 1.4 Dec 13, 2006 21:48:10 PT