70 BBC Sky at Night Magazine August 2021
Step by step: how to use WinJupos
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 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 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 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 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 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.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