AP: First detection of extra-solar terrestial sized planet?

I presume the short term variability is a long one, that it won't be picked up during 'b's transit and be lost in the noise.

In the case of 'b', I'm guessing that the eclipse may block approximately 1/300th the star's surface, dimming its light by only 0.003 magnitude, or 0.3%. This all depends of course on the ratio diameter of 'b' to the star. An eclipse of this degree cannot be detected unless the photometric measurements have a consistency approaching the milli-mag level over a span of many images (ie. 0.001 magnitude variation means that the brightness variation is about 0.1% of the signal).

What is the ratio of 'b' to star?
What exposure should I apply? eg. 5 to 40 seconds?
I wonder how precise the predictions are? I may have to start earlier this evening, in case the transit starts earlier than anticipated.

Detecting the transit is going to be an extremely difficult challenge. This will require luck of timing to catch an eclipse, the acquiring high quality image data, and the application of sophisticated techniques for image processing and measurement. Going to be a tall order to pull off.

Eamonn A

I'm going to watch this thread with great interest as this is exactly the sort of thing I want to try when I get myself finally set up. I imagine that the chances of getting enough reliable data for generate a light curve are vanishingly small given all the different factors and variables you have to wrangle with, but if you pull it off it will be an enormous feather in your cap! What instruments are you guys planning to use for the observations?

Phil.

Hi Phil,

I am going to use the 0.9m with an AP8p.

Alot of preparations to do yet. Going to be a long night!

Exposures may be over a 3.5 hour period (840) at 15 secs each.
This assumes the transit might start earlier than expected or later beyond the predicted times.

The longest period will be post processing the images.

Eamonn A

You've got a cracker of a night... at least it's a cracker here! Moonrise isn't until 23.10 and shouldn't be a problem until much later.

Best of luck!

Phil.

Present status of exoplanet 'b' of Gl 581. A predicted 86 minute transit event.

I managed to image Gl 581 last night.
230 images @ 20secs exposures with 12 second intervals.
Gl 581 was on my virtual horizon at an elevation of 15 degrees in Libra.
Started imaging before the event and about 45 mins after the event in case the transit predictions were inaccurate. This lasted about 2.5 hours of a sequence of 20 sec exposures. The last image was at 0200hrs UT.
The images came out well of Gl 581 and surrounding stars for comparison photometry.

I haven't had a chance yet to try photometric image processing. This will take a long time to process.

Eamonn A

Well done for grabbing it so low to the horizon. Let's hope there's some usable data hidden is some of the frames. Keep us posted.

Phil.