Skip to main content

Exoplanet WASP-11b/HAT-P-10b with a DSLR

mdurkin
mdurkin's picture
Offline
Joined: 2010-12-01

Hi everyone,

Last week I had a chance to try to measure a transit by exoplanet WASP-11b/HAT-P-10b using my DSLR camera.  My equiment used included a Canon Rebel XT (350D) and an 8 inch f/10 SCT.  For a period of just over 3 hours, I took a series of one minute exposures at ISO 1600 and calibrated using flat and dark frames.  I then used AIP4WIN with the green channel of the images with a selection of about 12 comp stars for ensemble photometry measurements which I've graphed below.  The Y axis is magnitude with an arbitrary offset so that I could place the two lightcurves relatively close to each other for comparison.  I haven't yet done any tranformations to a standard such as Johnson V since I was only interested in the shape of the curve.

To me, there seems to be a clear drop in brightness consistent with the time and depth as given by http://var2.astro.cz, the web site that I was using as a reference.  It also appears that I may have missed the very beginning of the transit since it took me a little longer to set up my gear than I had hoped.

Thanks for looking, and let me know what you think.


-Mike Durkin (DMPA)

What I think?
hhu
hhu's picture
Offline
Joined: 2010-07-23

Well, I find it very encouraging that you can do this with a DSLR. 

Hubert

Transit & DSLR
Roger Pieri
Roger Pieri's picture
Offline
Joined: 2010-08-02

Hi Mike,

Congratulation, you got it !

The depth is clearly about 2.5% that's well the value for this transit. You could determine it accurately by making the average during the deep compared to the average of the plateau at the end.  You just started imaging at the 1st contact, this is an usual problem ! I had the same experience a couple of times. It's not easy to properly start a four hours observation in a short night, the polar is not always visible at dusk and it's often difficult to make the setup in time.  

What you could try to reduce the scatter is to use the sum of the four DSLR channels instead of the green only. Normally the red should be somewhat more stable, the blue is said worst and is often eliminated by the transit observers. In fact this is not my experience with DSLR, using the four channels is usually best. Depending the case, you could have to compensate the color of the comparison ensemble to eliminate the effect of the atmospheric reddening during the observation. That could be made by balancing the RGB color mix of the comparison ensemble to make it similar to such of the target star. 

No doubt the DSLR are able to make it, they are able of very accurate photometry thanks to their CMOS technology. The fact to get three colors simultaneousely is important and has not been properly explored at time being. Next the technology of CMOS sensors improves every year. I just measured the instrumental noise of the last Canon APS-C, it's a factor two improvement from my 450D. Just a few more years and another paradigm... 

Clear Skies !    (here in Burgundy very bad, as most of this year, hope a better winter... )

Roger (PROC)

 

AAVSO 49 Bay State Rd. Cambridge, MA 02138 aavso@aavso.org 617-354-0484