18 replies to this topic

[kingsbishop]

What is the best way to get started on measuring exoplanet transits?

[BlueMoon]

 

Planets are extremely faint light sources compared to stars, and what little light comes from them tends to be lost in the glare from their parent star. So in general, it is very difficult to detect and resolve them directly from their host star. Planets orbiting far enough from stars to be resolved reflect very little starlight, so planets are detected through their thermal emission instead. https://en.wikipedia...ting_exoplanets

So, it appears you'll need a really large telescope, or work for NASA. Cheers.

[The0s]

So, it appears you'll need a really large telescope, or work for NASA. Cheers.

It's absolutely possible, and you don't even need a very big scope for it. This guy here on CN captured an exoplanet transit two days ago with an 8 inch scope.

 

OP, here might be a decent thread to just get you started - seems like there's a few good recommendations on there.

Edited by The0s, 14 January 2025 - 06:42 PM.

[auroraTDunn]

If you are talking transit light curves then note the very first ones were done with little 6" reflectors of semi-OK quality and at least one of those was in a fairly bright campus parking lot. Truth be told you don't even 'need' a telescope as I have seen it done with a Sigma 150-600mm lens on a Canon camera body (I sooooooo would not recommend this route - its' EXTREMELY difficult to get good data).

So aperture does not matter to much nor even focal length, but now that we have a large healthy list of stars to choose from a larger scope with longer fl makes life a bit easier.

The one thing I would suggest though is a decent enough scope and mix in some decent photometry filters to help get clean(er) light curves. Once upon a time Astrodon had some specialized photometry filters expressly for exoplanet research, good luck finding them now a days though with Astrodon sadly history (sniff sniff I LOVE their filters!). Not needed but they really help!

 

Since you need to record the entire transit multiple times you will want some sort of tracking, pending your target you don;t even really need guiding but you will want guiding.

 

After that its just go through all the great material we now have available, including entire classes, some of which are (err at least were) free and a slow patient approach with lack of fear to ask for help the first couple of times you try it.

 

The joy of seeing your own data for a planet circling another star for the first time will last the rest of your life!!!

[david_od]

So, it appears you'll need a really large telescope, or work for NASA. Cheers.

In exoplanet transit measurements you don't resolve the planet, but detect the changes in the star's luminosity when the exoplanet passes between it and us, via photometry.
It can be done even with DSLRs: https://www.cloudyni...s/#entry6010854

 

As additional resources:
https://astrodennis.com/
https://www.aavso.org/exoplanet-videos

Edited by david_od, 14 January 2025 - 07:52 PM.

[kingsbishop]

In exoplanet transit measurements you don't resolve the planet, but detect the changes in the star's luminosity when the exoplanet passes between it and us, via photometry.
It can be done even with DSLRs: https://www.cloudyni...s/#entry6010854

As additional resources:
https://astrodennis.com/
https://www.aavso.org/exoplanet-videos

yes but how can we be so sure that it isn’t atmosphere making the star change brightness I mean the camera equipment would have to be so sensitive and be able to detect the slightest dimming which the earth’s atmosphere can easily stuff up

[david_od]

yes but how can we be so sure that it isn’t atmosphere making the star change brightness I mean the camera equipment would have to be so sensitive and be able to detect the slightest dimming which the earth’s atmosphere can easily stuff up

Normally a few non-variable stars (close to the target) are used as reference. You can read more details in the websites cited above and associated documentation.

[GaryShaw]

What is the best way to get started on measuring exoplanet transits?

Hi

I’d suggest you start by reading some of the posts on the same topic as yours. Many of the response posts contain good advice - especially mine. 

Good luck !

Gary

[Ed Wiley]

What is the best way to get started on measuring exoplanet transits?

1. Learn to use your equipment (you didn't mention your equipment). You should be able to track a star for hours.

2. Do your homework reading up on exoplanet transit work.

3. Learn photometry and the photometric requirements for doing transit work with exoplanets, and do a bit of practice on eclipsing binaries.

 

Ed

[SeymoreStars]

Join the AAVSO and sign-up for their courses - https://www.aavso.org/choice-astronomy

 

 

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[kingsbishop]

1. Learn to use your equipment (you didn't mention your equipment). You should be able to track a star for hours.
2. Do your homework reading up on exoplanet transit work.
3. Learn photometry and the photometric requirements for doing transit work with exoplanets, and do a bit of practice on eclipsing binaries.

Ed

I have a 12 inch goto dobs but I am assuming I need a scope with better tracking

[GaryShaw]

Hi
You can probably play around with transits with the DOB just to test it out and see what it’s all about but if you’re really interested/committed, you’ll want to pick up a decent EQ Mount and OAG gear for the optics train. Quality guiding/ tracking is key in minimizing systematic type errors. That said, there’s still value in observing and reporting ( via AAVSO) transits of confirmed exoplanets using rather minimal gear. Give it a try. Doesn’t even have to be a full transit as long as you get a good baseline before/after the transit and around half of the transit itself.
Give it a try with what you have and go from there.
Gary

[kingsbishop]

Hi
You can probably play around with transits with the DOB just to test it out and see what it’s all about but if you’re really interested/committed, you’ll want to pick up a decent EQ Mount and OAG gear for the optics train. Quality guiding/ tracking is key in minimizing systematic type errors. That said, there’s still value in observing and reporting ( via AAVSO) transits of confirmed exoplanets using rather minimal gear. Give it a try. Doesn’t even have to be a full transit as long as you get a good baseline before/after the transit and around half of the transit itself.
Give it a try with what you have and go from there.
Gary

interesting but how do I know that it is the transit of the planet dimming the star and not atmosphere distortion since the dimming has to be extremely sensitive?

[GaryShaw]

You analyze the data with AIJ, detrend for AIRMASS and other factors and then the application (AIJ) mathematically fits a curve to the data showing the ‘relative’ drop in brightness of the star due to the transit of the planet.

A bit simplified but that’s a fair compressed view of the process. A lot to learn …
Gary

[pvdv]

interesting but how do I know that it is the transit of the planet dimming the star and not atmosphere distortion since the dimming has to be extremely sensitive?

By using differential photometry. You don't actually measure the variation of light coming from the star in absolute terms, but you compare it, in each frame, with other nearby, non-variable and, ideally, of similar brightness and color/spectral type stars. 

With that method, it becomes a counting game, and you want your ADU to be as high as possible, but never saturated. 

Reading the available tutorials in full is really a good idea, especially if you are only getting started. Much better than asking quick questions imho.

Edited by pvdv, 16 January 2025 - 08:01 AM.

[Ed Wiley]

Kingsbishop,

 

From the responses you have given to some of those on the forum suggests that you need to read up on how amateurs do exoplanet photometry and on photometry in general.You also need to understand the kind of equipemnt you need, and its not a 12" Dob. Once you do your homework you will be better positioned to ask questions and receive answers that make sense to you. 

 

Ed

[Matthew Paul]

A good place to start would be NASA's ExoPlanet Watch citizen science program. They provide fresh data from their small telescope network that you can process and make meaningful contributions. The data is processed through their software "Exotic" which then outputs the files necessary for you to upload them through the AAVSO. There is a plethora of documentation available and people to guide you along the way. 

The other option is to buy a couple books on the subject and use Dennis Conti's documentation and sample files, available through the AAVSO, and process the transit data through software like AstroImageJ. This is more complex but gives you some more freedoms in processing.

A small scope is plenty and you don't need a huge observatory to do transit photometry. Especially if you're just looking to do mid transit timing or just to perform an observation for fun. There are stars like HAT-P-68 which are bright and have HUGE transit depths. 

[Randyf2017]

Do look into this.  It is fascinating.  To think someone in their backyard has the technology to discern an exoplanet is amazing.  In the olden days (how many years ago?) this would have been science fiction. 

[Xilman]

It's absolutely possible, and you don't even need a very big scope for it. This guy here on CN captured an exoplanet transit two days ago with an 8 inch scope.

 

OP, here might be a decent thread to just get you started - seems like there's a few good recommendations on there.

This guy here at the BAA captured an exoplanet transit two days ago with a 4 inch scope.