From: "milton_aupperle" <milton@outcastsoft.com>

Date: April 26, 2012 1:38:10 PM MDT

To: Astro_IIDC@yahoogroups.com

Subject: Qatar Exoplanet Transit

Hi Folks;

Last week I mentioned there was the Qatar-2B Exoplanet transit on April 20th.

I "sort of" captured it but under very bad conditions. Qatar was 25 to 31° above the horizon then so I'm shooting through 2+ times  the air mass, the Jet Stream was right over top with FWHM in the 5 to 7 arc second range, under light polluted skies (brightly lit parking lot to my immediate south now) and I had thin hazy clouds passing through too. I using a small 200 mm aperture scope shooting at 1625 mm focal length,  so I had to shoot binned 2x2 and use 30 second exposures for a Mag 13.3 (mag ~ 14.0  after air mass correction dimming).

In any case, after using a 16 point FFT fit to smooth the data (327 samples over ~ 3 hours) points down and generate the fitted curves, I came up with this:

http://groups.yahoo.com/group/Astro_IIDC/files/Other/Qatar2B_Transit_20120420_MJA.pdf

The Blue curves are my three constant stars, which show a 0.02 mag variations after being 16 point smoothed. Scatter for individual samples is around 0.03 mags.

The Yellow curve it the Qatar Original curve and the Green curve - dots are my Check star. The vertical black lines mark the predicted start and end of the transit. However just after half way through the transit, both Qatar yellow and the green Check star brightens up "early" by about 0.03 magnitudes. I checked the detailed results for each sample and that brightening hump is due to the sky background going from 5,700 to  about 6,500 (out of 65,535). That is what cause the increase, because that raises the star brightness measured within the Aperture. The SNR Ratio goes from 244:1 at the start of the "hump"  to 92:1 at the centre and then back to 260:1 at the end. Qatar and the check star only have a maximum pixel brightness of  about 10,000 out of 65,535, so the raised background really affects them much more that the brighter constant stars.

So what I did was assume my green check star is constant (other stars of similar brightness show the same brightening too), and used the difference from the green star average to adjust the smoothed curve data for Qatar, which is the Red Qatar Leveled curve. So you can sort of see the drop of about 0.04 magnitudes. The 16 point FFT smoothing will spread the expected sharp drop off over 8 minutes of time, which is why I don't have sharp edges for the transit.

So it looks like yes I detected it, but it isn't of any scientific use. And if I did not have apriori knowledge that this was an exoplanet, I would never have known it is a transit.

Clear Skies..

Milton Aupperle