My 3rd exoplanet observation

[dokeeffe]

TrES-3b from 2 nights ago. An easy target with quite a large dip of 0.029mag

About 140 60sec exposures using a C11 @f6.3 and an ATIK383L+. Used a luminescence filter this time as an experiment instead of a photometric filter. Seems to have come out quite well 

More info on the planet here http://var2.astro.cz/ETD/etd.php?STARNAME=TrES-3&PLANET=b

 

[David Levi]

Very interesting. Do you have to monitor the star over several sessions to get the readings when the planet passes in front of it? Following on from that, is it possible to continue monitoring and work out the period of orbit of the planet?

[dokeeffe]

1 hour ago, David Levi said:

Very interesting. Do you have to monitor the star over several sessions to get the readings when the planet passes in front of it? Following on from that, is it possible to continue monitoring and work out the period of orbit of the planet?

all those measurements were taken on 1 night. The UTC time is on the x axis. about 23:30 to 2:30. However yes, as you say, it is possible to overlap several transits to get a much less noisy light curve and refine the orbit. I've never done this though.

[David Levi]

Were you just lucky to see something on that particular night or had you been looking at this star for a while?

[dokeeffe]

Kind of luck alright :-) It was the first clear night here in Ireland in like months. So I took a look at EDT http://var2.astro.cz/ETD/predictions.php?delka=-8&submit=submit&sirka=52 which lists all the transits happening soon for my location and spotted this star with a large dip in mag (0.029) and also the timing was good as it was rising in the sky and was pretty high by mid transit. The first bunch of points are noisy because it was lower in the sky,

[7170]

This is really interesting and inspiring, please keep posting your exoplanet observations here!

Out of interest what is your C11 mounted on - Celestron fork or something different?

[dokeeffe]

22 hours ago, 7170 said:

Out of interest what is your C11 mounted on - Celestron fork or something different?

It a fork mount, the CPC1100. Its the weak link in the chain now. Its got a lot of periodic error, roughness and backlash. So my stars are bigger than they should be on the images. Its contributing to the noise for sure. I'm thinking of de-forking it and getting something like an EQ8 or maybe an ioptron CEM120, the one with the encoder sounds good. No need to guide (or so I heard)

[Dave Smith]

That is very cool, well done. Presumably the gradual lowering of the brightness is due to the size of the planet being an appreciable proportion of the size of its transit. 

Dave

[Chris]

Great stuff!  

[Demonperformer]

Excellent. I'm going to have to go looking for observations 1&2 now.

[dokeeffe]

9 hours ago, Dave Smith said:

That is very cool, well done. Presumably the gradual lowering of the brightness is due to the size of the planet being an appreciable proportion of the size of its transit. 

Dave

Yes, and also other effects like limb darkening of the star combined with any tilt in the orbit. Its kinda hard to explain but if you imagine the planet crossing right through the midline of the star from our point of view, versus the planet crossing, closer to a polar region. If crossing right through the middle, the planet 'shadow' cuts right through the star's limb darkening quickly and crosses into the bright part of the star. If the planet's shadow cuts in closer to a pole or lower down, the shadow spends more time in the darkened limb area and therefore the change in brightness takes more time..

Its hard to explain. but imagine the difference between the top 'L' and middle 'L' below.

[Dave Smith]

Thanks for that. Very interesting.

Dave