Help on reading ephemeris in HJD(TT)

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In summary, the conversation discusses the transit of a planet orbiting the star HD209458, with a specific ephemeris of HJD(TT) 2453344.768245 + 3.52474859 E. The person wishes to view the transit from the WHT in La Palma and asks for the best night and precise UTC of the mid-transit. It is determined that the transit occurs regularly every ~3.5 days, but the best viewing time would depend on the altitude of the star at mid-transit.
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Homework Statement



The star HD209458 has an orbiting planet. The planet has a transit with ephemeris
HJD(TT) 2453344.768245 + 3.52474859 E

I wish to view the transit of the planet from the WHT (William Herschel Telescope) in La Palma.
On which night in 2014 is the transit best observed?
What is the precise UTC of the mid-transit?



Homework Equations



None that I can think of (Except perhaps equations that convert units)


The Attempt at a Solution



I'm new to this terminology, and can't find any resources online that go into any detail. The planet transits with a regular period of course, and I believe the format of the above expression of the time of mid-transit is intended to convey this somehow. I had thought that the HJD(TT) 2453344.768245 part referred to a date (which it does, sometime in 2004) and the 3.52474859 E part indicates the periodicity, ie that the planet transits every ~3.5 days (in HJD(TT)), but if this is the case, there will be many nights on which the transit can be observed. Could anybody enlighten me on the correct way to read the ephemeris?
 
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You are doing it correctly, and you are right that there are many times that the transit occurs. However, some will be in the daytime, and some will be when the star is below the horizon or low in the sky. You are asked to find which one is best situated for viewing from La Palma. One way might be to calculate the altitude of the star at mid-transit. The best one might be when the star is highest above the horizon.
 

Related to Help on reading ephemeris in HJD(TT)

1. What is an ephemeris and how is it used in scientific research?

An ephemeris is a table or data set that lists the predicted positions of astronomical objects at specific times. In scientific research, ephemerides are used to track the movements of celestial bodies and to make accurate predictions for future observations.

2. What does HJD(TT) stand for and how is it different from other systems of time measurement?

HJD(TT) stands for Heliocentric Julian Date in Terrestrial Time. It is a system of time measurement that is commonly used in astronomy and is based on the position of the Earth relative to the Sun. Unlike other systems of time measurement, HJD(TT) takes into account the effects of relativity and is more precise for astronomical calculations.

3. How do I read and interpret an ephemeris in HJD(TT)?

An ephemeris in HJD(TT) is typically organized into columns that represent the date, time, and position of an astronomical object. The date and time are listed in HJD(TT) format, and the position is given in terms of right ascension and declination. These coordinates can be converted into a sky map for visualization purposes.

4. Are there any common mistakes when reading ephemerides in HJD(TT)?

One common mistake when reading ephemerides in HJD(TT) is confusing it with other systems of time measurement, such as Julian Date or Universal Time. It is important to use the correct system when making calculations or observations. Additionally, it is crucial to make sure that the date and time are accurate to ensure the predicted position is correct.

5. Where can I find reliable ephemerides in HJD(TT) for my research?

There are many reputable sources for ephemerides in HJD(TT), such as the Minor Planet Center, the International Astronomical Union, and NASA's Jet Propulsion Laboratory. It is important to choose a reliable source and to double-check the accuracy of the ephemeris before using it for research purposes.

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