Image requirementsWhich images are most welcome?
Webcam or CCD images to be measured in WinJUPOS must show local features of Jupiter's atmosphere in addition to the global belts and zones. Averagely enhanced images, neither being completely raw nor showing artefacts due to cruel over-processing are optimum. Jupiter's true limb has to be clearly visible, especially it must not have dimmed out by too heavy limb-darkening.
If you have secured several exposures during an observing session, please send good samples separated by 30 to 60 minutes each. Such series enable us to improve the accuracy of JUPOS measurements markedly as WinJUPOS' outline frame can additionally be adjusted at well defined atmospheric features then, not just at Jupiter's limb which is seldom perfectly displayed. Do not send your very top results only as striking features (for example, dark NEBs projections) are often measureable on images of lower resolution.
Individual frames used for producing the final image must not span more than 2 minutes in total. Otherwise, Jupiter's rotation will blur the image. Please indicate longer exposures as described in paragraph "How to specify time of exposure, and spectral properties?" below.
The orientation of Jupiter's disc (north up, or down, or...) is free. If a moon or moon shadow is displayed together with Jupiter, this is very helpful for positional measurements. Do not cut away a moon near Jupiter but leave it in the image.
Unless you are a contributor who already sends observations directly to another member of the JUPOS team, please send your image as file attachments to my e-mail address (see "Contact" in the left frame), or give web addresses of the individual images in your e-mail. For example:
please not just: http://www.mysite.net
It is impossible for me to monitor a long series of websites whether they maybe contain new images which have not yet been measured.
Which graphic format to use?
PNG files are our favourites because this format provides lossless compression. If you want to use JPEG, however, do not over-tune the compression rate. Values of 90% or so are nice for reducing transfer time when sending e-mails but kill much information visible on the original images, especially in the red RGB channel. In most cases, a compression rate of about 30% is optimum. Compress less in case of doubt.
How to specify time of exposure, and spectral properties?
Exact information on exposure time is an absolute must for determining precise positions. Please record all times with an accuracy of 30 seconds minimum. Images with exceptional high resolution require an accuracy of 0.2 minutes. Synchronise your clock against a reliable time source regularly.
Write date and time of exposure, and the colour channel directly on each image. Only use Universal Time (UT) to avoid worldwide confusion. Be aware of a possible change of day when converting your local time to UT!
That time has always to represent mid of exposure, neither its begin nor its end. However, if a composite was stacked from frames spanning slightly more than 2 minutes, please record the total time range on the image, e.g., 20:34.2-37.1 UT.
Please name each file according to a special scheme in order to simplify measuring and cataloguing of images. WinJUPOS supports several schemes. The most important are:
YYYY ... year
Method 1 is preferred by JUPOS. Please choose one scheme, and do not change it during a Jovian apparition. Notice the difference between minus sign (in 1) and underscore (in 2 and 3).
Examples of method 1:
Examples of method 2, same times as in 1:
Examples of method 3, same times as in 1:
Also this filename timestamp has to represent mid-exposure. However, if an image file shows several Jupiter discs taken at very different times during a night, omit hour and minute in its name, for example: 2008-05-21-Smith.png .
WinJUPOS 9.1.18 (and later) offers a function called de-rotation at "Tools / De-rotation of images, R/G/B frames, video streams". De-rotation eliminates geometrical distortions caused by the planet's rotation, and stacks rotation-rectified frames. It allows to produce precise image compilations spanning much more than two minutes.
If you use the de-rotation routine of WinJUPOS, please clearly indicate:
- the precise mid-point of exposure (in UT), and
and a short information about the used WinJUPOS method, that is:
- De-rotation of images
on every final image. Use the timestamp coded in the name of the de-rotated image file (for example, 2011-10-15-0058.5.png) as the mid-point of exposure.