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My second exoplanet transit in the bag



 
 
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  #1  
Old October 17th 05, 01:59 AM
Robin Leadbeater
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Posts: n/a
Default My second exoplanet transit in the bag

Well half in the bag at least.

I managed to catch the egress of recently announced HD189733b on Friday
using just a modified webcam but missed the ingress window tonight because
of cloud cover.

http://mysite.wanadoo-members.co.uk/..._HD189733b.htm

This is the easiest exoplanet for amateurs to date. Nice and deep at 3% , a
bright mag 7 parent star and a good matching comparison star nearby. It is
easy to find too, near M27.

Robin
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54.75N 3.24W
http://www.leadbeaterhome.fsnet.co.uk/astro.htm
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  #2  
Old October 17th 05, 02:37 AM
Doink
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Posts: n/a
Default My second exoplanet transit in the bag

How are you able to measure magnitude so accurately? Seems a real
task---nice job.

Doink

"Robin Leadbeater" wrote in message
...
Well half in the bag at least.

I managed to catch the egress of recently announced HD189733b on Friday
using just a modified webcam but missed the ingress window tonight because
of cloud cover.

http://mysite.wanadoo-members.co.uk/..._HD189733b.htm

This is the easiest exoplanet for amateurs to date. Nice and deep at 3% ,
a
bright mag 7 parent star and a good matching comparison star nearby. It
is
easy to find too, near M27.

Robin
----------------------------------------------------------------------------
-
54.75N 3.24W
http://www.leadbeaterhome.fsnet.co.uk/astro.htm
----------------------------------------------------------------------------
-




  #3  
Old October 17th 05, 08:21 AM
nytecam[_1_] nytecam[_1_] is offline
Senior Member
 
First recorded activity by SpaceBanter: May 2005
Location: london-uk
Posts: 741
Default

Well done Robin - nice to see someone is actually observing on this forum;-)
Nytecam

Quote:
Originally Posted by Robin Leadbeater
Well half in the bag at least.

I managed to catch the egress of recently announced HD189733b on Friday
using just a modified webcam but missed the ingress window tonight because
of cloud cover.

http://mysite.wanadoo-members.co.uk/..._HD189733b.htm

This is the easiest exoplanet for amateurs to date. Nice and deep at 3% , a
bright mag 7 parent star and a good matching comparison star nearby. It is
easy to find too, near M27.

Robin
----------------------------------------------------------------------------
-
54.75N 3.24W
http://www.leadbeaterhome.fsnet.co.uk/astro.htm
----------------------------------------------------------------------------
-
  #4  
Old October 17th 05, 10:34 AM
Robin Leadbeater
external usenet poster
 
Posts: n/a
Default My second exoplanet transit in the bag


"Doink" wrote in message
...
How are you able to measure magnitude so accurately? Seems a real
task---nice job.

Doink


High absolute accuracy is not so important in transit measurements, just the
ability to keep everthing stable enough to measure small changes over a few
hours. This is done by comparing the brightness of the varying star in the
images with a nearby reference star .

Robin


  #5  
Old October 17th 05, 02:22 PM
Anthony Ayiomamitis
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Posts: n/a
Default My second exoplanet transit in the bag

Robin,

Many congrats on the light curve and a big thanks for the heads-up. I
will pursue something similar in a couple of weeks when I will have a
favourable transit for my location.

Clear skies!

Anthony.


Robin Leadbeater wrote:
Well half in the bag at least.

I managed to catch the egress of recently announced HD189733b on Friday
using just a modified webcam but missed the ingress window tonight because
of cloud cover.

http://mysite.wanadoo-members.co.uk/..._HD189733b.htm

This is the easiest exoplanet for amateurs to date. Nice and deep at 3% , a
bright mag 7 parent star and a good matching comparison star nearby. It is
easy to find too, near M27.

Robin
----------------------------------------------------------------------------
-
54.75N 3.24W
http://www.leadbeaterhome.fsnet.co.uk/astro.htm
----------------------------------------------------------------------------
-


  #6  
Old October 17th 05, 02:24 PM
Anthony Ayiomamitis
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Posts: n/a
Default My second exoplanet transit in the bag

Robin Leadbeater wrote:

"Doink" wrote in message
...

How are you able to measure magnitude so accurately? Seems a real
task---nice job.

Doink



High absolute accuracy is not so important in transit measurements, just the
ability to keep everthing stable enough to measure small changes over a few
hours. This is done by comparing the brightness of the varying star in the
images with a nearby reference star .


Robin,

Typically with photometry we need two reference stars (comparison and
calibration). Which star(s) did you use?

Anthony.


Robin


  #7  
Old October 17th 05, 02:47 PM
Robin Leadbeater
external usenet poster
 
Posts: n/a
Default My second exoplanet transit in the bag


"Anthony Ayiomamitis" wrote in message
...
Robin Leadbeater wrote:

"Doink" wrote in message
...

How are you able to measure magnitude so accurately? Seems a real
task---nice job.

Doink



High absolute accuracy is not so important in transit measurements, just

the
ability to keep everthing stable enough to measure small changes over a

few
hours. This is done by comparing the brightness of the varying star in

the
images with a nearby reference star .


Robin,

Typically with photometry we need two reference stars (comparison and
calibration). Which star(s) did you use?


Hi Anthony,

It is nice to have an additional check star to make sure everything is
stable but you can get away with just one comparison star. In this case
(unlike TrES-1) I had to make do with just one as there were no other
suitable stars close enough, though you might find some if you have a wider
field. I used SAO 88067 which is similar in same magnitude to HD189733
(important when you have only 8 bits to play with!) and a good colour
match to minimise differential extinction issues. The Vmags shown on the
image are published values.

Good luck with your measurements

Robin


  #8  
Old October 24th 05, 02:20 AM
jerry warner
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Posts: n/a
Default My second exoplanet transit in the bag

nice work.

Robin Leadbeater wrote:

"Anthony Ayiomamitis" wrote in message
...
Robin Leadbeater wrote:

"Doink" wrote in message
...

How are you able to measure magnitude so accurately? Seems a real
task---nice job.

Doink


High absolute accuracy is not so important in transit measurements, just

the
ability to keep everthing stable enough to measure small changes over a

few
hours. This is done by comparing the brightness of the varying star in

the
images with a nearby reference star .


Robin,

Typically with photometry we need two reference stars (comparison and
calibration). Which star(s) did you use?


Hi Anthony,

It is nice to have an additional check star to make sure everything is
stable but you can get away with just one comparison star. In this case
(unlike TrES-1) I had to make do with just one as there were no other
suitable stars close enough, though you might find some if you have a wider
field. I used SAO 88067 which is similar in same magnitude to HD189733
(important when you have only 8 bits to play with!) and a good colour
match to minimise differential extinction issues. The Vmags shown on the
image are published values.

Good luck with your measurements

Robin


 




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