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Detecting Exoplanets

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#1 Jeff Struve

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Posted 18 March 2019 - 02:03 PM

Howdy!

 

Have any of you checked out the YouTube Video, "Detect exoplanets by yourself with the cheapest equipment" by The Exoplanets Channel?

 

https://www.youtube....h?v=XHCppdWYs6w

 

This looks like a fun thing to do but have a few questions for those that have given it a shot. 

 

The Exoplanet Channel has been great help, but was hoping that someone here may have additional files that they would not mind letting me use for my learning to use the software and for demo purposes in giving a presentation to our club on the subject.... at least until I can collect my own data...

 

The data I have for the HD 189733 would work fine, but it isn't as 'perfect' as I'd like.

  • There is a null spot where a cloud blanked out the data, and that seems like a key location in the data.
  • Selecting on some stars as the reference point errors out... Possibly over exposure?
  • I wish there was a little more pre and post transit data 

 

Another problem that I am having is in looking up date/time of transits on the web site, "ETD - Exoplanet Transit Database" , http://var2.astro.cz/ETD/

  • I am not sure how to enter my Latitude and Longitude in to the Transit Predictions section, http://var2.astro.cz...189733&PLANET=b  ... they ask for:
    • Your ELONGITUDE (in deg):  0° - 360° 
      Your LATITUDE (in deg):  90° - 0° - -90°
    • I tried a number of different variations and my link is for 91° and 42° respectively
  • The time is in UTC, and they give you different color font to indicate, Transit occurs below 20° in the sky, During the daylight and Observable. But when I convert the UTC time into Central time, the Observable times are during daylight... maybe because my Lat/Long is off??? Maybe not part of the calculation?

 

Anywho... If any of you have loaner data... understand how to better input my Lat/Long for here in Iowa, USA... make it easier to convert to Central Time... I'd appreciate it!

 

Thanx and Clear Skies!

Jeff

 

 


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#2 George Bailey

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Posted 18 March 2019 - 02:50 PM

Jeff -

 

Our longitude is actually negative (my house is -90.591 , which is also 90.591 W, where W is negative. East is positive).

 

Since they seem to ask for a 0 to 360 long, maybe one needs to calculate the absolute long going EAST to our location?

 

SO 180.000* + (180.000* - 90.571) = 269.409*  ish.

 

Would that make sense ???

 

Or just try the negative sign value and see if that helps.

 

Good luck !


Edited by George Bailey, 18 March 2019 - 02:59 PM.

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#3 S.Boerner

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Posted 18 March 2019 - 03:26 PM

There's an excellent reference on the AAVSO's web site.  Go to https://www.aavso.or...serving-manuals and check out Dennis Conti's Exoplanet Observing Guide.  Also look at Conti's web site at astrodennis.com where you can find instructions to use AstroImage-J, data you can download to test things out and a number of presentations he's made to groups.

 

Good luck!


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#4 Jeff Struve

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Posted 19 March 2019 - 11:09 AM

Jeff -

 

Our longitude is actually negative (my house is -90.591 , which is also 90.591 W, where W is negative. East is positive).

 

Since they seem to ask for a 0 to 360 long, maybe one needs to calculate the absolute long going EAST to our location?

 

SO 180.000* + (180.000* - 90.571) = 269.409*  ish.

 

Would that make sense ???

 

Or just try the negative sign value and see if that helps.

 

Good luck !

yep... I think this was the ticket... It looks like all of the "Observable" times are now after sunset. I used 42° and 269°

 

Thanx!



#5 Jeff Struve

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Posted 19 March 2019 - 11:11 AM

There's an excellent reference on the AAVSO's web site.  Go to https://www.aavso.or...serving-manuals and check out Dennis Conti's Exoplanet Observing Guide.  Also look at Conti's web site at astrodennis.com where you can find instructions to use AstroImage-J, data you can download to test things out and a number of presentations he's made to groups.

 

Good luck!

AstroImageJ is pretty simple if ya just click on a few of the right things... I could use more sample data though... I'll check it out.  

 

Thanx!



#6 StarmanDan

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Posted 19 March 2019 - 11:41 AM

ETD uses east longitude for location.  So for my site at roughly 96W 31N it would get put in as 264 for the longitude (360-96) and 31 for latitude.  Click submit and ETD will show you a list of observable transits for your location.  All times are in UTC so you will have to do some mental math to convert to your time zone.  If you click on a transit, a finder chart will show the location of the target star, and a list of future transit predictions appear below.  Transit dates are in Julian date.  There are plenty of online calculators to convert to Gregorian date.  Transits in yellow are during the day, in black are observable at night.  Here is a transit I did last year:

 

 

Attached Thumbnails

  • wasp80b.png

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#7 Jeff Struve

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Posted 19 March 2019 - 12:07 PM

Any ideas on why using some reference stars don't set a valid reference point while others do?

 

THis is the data I received from The Exoplanet Channel using their reference star: 

 

 

Attached Thumbnails

  • 507062877_20190315_180612_3648482_resized.jpg


#8 Jeff Struve

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Posted 19 March 2019 - 12:09 PM

Here is the same data using different stars for reference...

 

The top one also gave some sort of error message that the a file could not be read... then if you delete that bad one and rerun it, the next file is bad... and that continues on, and on... 

Attached Thumbnails

  • -2070484234_20190315_180341_3531440_resized.jpg
  • 1224309819_20190315_180203_4043244_resized.jpg


#9 gavinm

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Posted 19 March 2019 - 02:13 PM

What sort of data do you want? raw images or just numbers?


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#10 Jeff Struve

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Posted 19 March 2019 - 02:16 PM

What sort of data do you want? raw images or just numbers?

I would actually like raw images so I can show the whole process...after imaging imaging...



#11 gavinm

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Posted 19 March 2019 - 02:41 PM

Can do - I just need to find a way of posting them :) thats a lot of images (I'll probably need to convert them to JPEGS)

 

I do/did all my photometry using Maxim DL and the analysis and modelling using software I wrote in MATLAB (verified using ETD)


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#12 StarmanDan

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Posted 19 March 2019 - 02:52 PM

Have you read through Dennis Conti's guide? 

 

http://astrodennis.com/Guide.pdf

 

Sounds like you may have corrupted data.  Might try downloading it again.  AIJ can be a bit particular in the image format and header info.  This vid will give you a very basic, quick and dirty procedure to get a curve.

 

https://www.youtube....h?v=EfMPl2SaSjM

 

using different reference stars shouldn't change the curve unless the reference star is variable also.  Ideally you want to use several reference stars not just one.


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#13 gavinm

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Posted 19 March 2019 - 03:40 PM

This was always my favourite when I started

http://brucegary.net/book_EOA/EOA.pdf


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#14 gavinm

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Posted 19 March 2019 - 03:43 PM

The best data will always be if you use reference stars of a similar spectral type to the target (assuming broadband filter) where possible (or use a narrowband photometric filter)


Edited by gavinm, 19 March 2019 - 03:43 PM.

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#15 gavinm

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Posted 19 March 2019 - 10:30 PM

I've got a full transit of WASP 6b from a 0.6m that I took, but it's 257 FITS files (@ 541 MB) - anyone got suggestions how I can post this?

I know I've got some smaller ones around as well, just have to dig them out (and they're still pretty huge)


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#16 Jeff Struve

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Posted 20 March 2019 - 06:25 AM

Can do - I just need to find a way of posting them smile.gif thats a lot of images (I'll probably need to convert them to JPEGS)

 

I do/did all my photometry using Maxim DL and the analysis and modelling using software I wrote in MATLAB (verified using ETD)

I was sent a .rar compressed file via email containing quite a few FITS files... I just had to unzip it... I don't know how to create that though... 

 

Thanx!



#17 Jeff Struve

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Posted 20 March 2019 - 06:31 AM

Have you read through Dennis Conti's guide? 

 

http://astrodennis.com/Guide.pdf

 

Sounds like you may have corrupted data.  Might try downloading it again.  AIJ can be a bit particular in the image format and header info.  This vid will give you a very basic, quick and dirty procedure to get a curve.

 

https://www.youtube....h?v=EfMPl2SaSjM

 

using different reference stars shouldn't change the curve unless the reference star is variable also.  Ideally you want to use several reference stars not just one.

After watching that video, I'm thinking that maybe the data is not quite as good as what I'd like to have. It will work if I stick to the target and that 1 reference star, but does nothing like shown in this video.

 

Thanx!



#18 Jeff Struve

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Posted 20 March 2019 - 06:33 AM

I've got a full transit of WASP 6b from a 0.6m that I took, but it's 257 FITS files (@ 541 MB) - anyone got suggestions how I can post this?

I know I've got some smaller ones around as well, just have to dig them out (and they're still pretty huge)

Not sure how it can be posted here... can they be compressed and emailed?

 

Thanx!



#19 yawg

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Posted 24 March 2019 - 06:44 PM

ETD uses east longitude for location.  So for my site at roughly 96W 31N it would get put in as 264 for the longitude (360-96) and 31 for latitude.  Click submit and ETD will show you a list of observable transits for your location.  All times are in UTC so you will have to do some mental math to convert to your time zone.  If you click on a transit, a finder chart will show the location of the target star, and a list of future transit predictions appear below.  Transit dates are in Julian date.  There are plenty of online calculators to convert to Gregorian date.  Transits in yellow are during the day, in black are observable at night.  Here is a transit I did last year:

 

Dan, how did you get such clean data?  What were your acquisition details and hardware?  how are your error bars so small?  All of my results (albeit with a 5 inch refractor) have had a really high scatter.  Too high to be useful imo.  Also, what is the SNR of your target in each image, on average?



#20 StarmanDan

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Posted 25 March 2019 - 12:21 PM

Dan, how did you get such clean data?  What were your acquisition details and hardware?  how are your error bars so small?  All of my results (albeit with a 5 inch refractor) have had a really high scatter.  Too high to be useful imo.  Also, what is the SNR of your target in each image, on average?

My club has a research grade observatory with a 24" f/9 RC and a Princeton Instruments Pixis 2048 camera capable of cooling to absolute temps as low as -70C.  We can obtain mmag photometry on objects as faint as 16 mag with 30 sec images.  We usually get reliable photometry with target SNRs as low as 200 counts above the background but have gone as low as 100 before and still gotten useable data.  The real trick to getting small error bars is not only having good equipment but getting good calibration.  Despite not technically needing darks or bias, we take them anyway.  

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  • trsscope.jpeg

Edited by StarmanDan, 25 March 2019 - 02:49 PM.

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#21 BillP

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Posted 28 March 2019 - 06:33 PM

Jerry Hubbell at jrh@explorescientific.com does exoplanet transit detection using a local observatory he and some other amateur astronomers in Virginia put together.  He's more than happy to discuss the process with anyone.  Here's an article on their effort - https://www.cloudyni...t-hunters-r3173




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