Step by step: how to use WinJupos

Thanks to its many measuring tools, WinJupos is the software equivalent of a Swiss Army Knife for planetary observers. Here we use it to show the width of the Great Red Spot

Step 1

Download WinJupos from http://jupos.org. Run the freeware and select ‘Celestial Body > Jupiter’ under the ‘Program’ menu. Next, under the ‘Recording’ menu, select ‘Image measurement…’ . In the subsequent window click ‘Open image’ (F7) and select your image.

Step 3

The correct frame orientation and alignment is important. ‘Outline frame’ > ‘Automatic detection’ may work, otherwise use the cursor arrow keys to move position, ‘PgUp’/’PgDn’ to magnify/ shrink and ‘N’ and ’P’ keys to rotate clockwise/counter-clockwise.

Step 5

Click ‘Compile map’ (F12) to generate a map in WinJupos. You will notice that the latitude (B) and longitude (L1, L2 and L3) values at the position of your mouse cursor are displayed in the status bar.

Step 2

Ensure the 'Date' and ‘Time’ for the image are correct in the ‘Imag.’ tab, before selecting the ‘Adj.’ tab (to the immediate right of the ‘Imag’ tab). Select the correct ‘Channel’ (F9) value for the image and ensure ‘Draw outline frame’ is selected.

Step 4

With everything set correctly, click ‘Save’ (F2) from the ‘Imag.’ tab and save the ‘Image measurement’ file. Next, select ‘Analysis’ > ‘Map computation…’ and then click on ‘Add’ from the dropdown ‘Edit’ menu.

Step 6

Measuring the longitude values of the preceding and following edges of the Great Red Spot (GRS) using L2 (System II), along with its central latitude, allows you to calculate the physical width of the GRS as 17,132km.