Transit Time @ Local Meridian

Good images of a planet is usually made when the object is crossing the local meridian. I use CALSky to get the ephemeris of the transit time of the planets for my location.

First, you have to set your location clicking in Setup and follow the instructions to set it precisely.


Once you have set and saved your location you can start looking for the ephemeris of the Solar System and Deep Sky objects. For example, for Jupiter you may click in “Planets” then click in the image of Jupiter. After that, you click in the “Positional Ephemeris”.


Then, you select:

  • Starting Date of Calculation –  in this example I set it to 01 January 2018 AD
  • Time,  set to “00:00:00”
  • Duration, select “1 Year”
  • Interval – “1 Day”

Press “go


You will get one year Jupiter ephemeris for your vey location where the most important information are:

  • Date,
  • Diameter in arc senconds,
  • Rise time,
  • Transit time, and
  • Set Time.

Transit time being the time where Jupiter will cross your local meridian and that is the time you want to image Jupiter which will give the best results for sure.


Copy and paste the data in an Excel spreadsheet. After you paste it to Excel you will notice that the date is in colunm A cells only.

Click in the colunm A header to select all cells in colunm A, then select “Data” and “Text to Colunms” tool in the Excel ribbon.

Select “Delimited” and then “Space”. You will have to play with the divisions in order to get them right and adjust the header after the convertion from Text to Colunms. Try different sets.

You may want to do it again for the other planets and save the data in different tabs of your spreadsheet, one for each planet of interest.

Now, you can start planning your image sessions based on the planets transit time. The best moment to get a good image of any object even for Deep Sky Objects.


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