How to com­bine images of vary­ing sizes from dif­fer­ent sources into a mea­sur­able stan­dard

Sky at Night Magazine - - IMAGING FOR SCIENCE -

WinJUPOS is the so ware equiv­a­lent of a Swiss army knife for plan­e­tary ob­serv­ing and imag­ing. It pro­vides many func­tions, in­clud­ing the abil­ity to mea­sure, an­a­lyse and re­port on fea­ture evo­lu­tion and dri over time. One hur­dle to over­come is nor­mal­is­ing images to a com­mon stan­dard for com­par­i­son. For ex­am­ple, it’s not un­com­mon to image over sev­eral nights with di er­ent cam­era ori­en­ta­tions or even image scales. For com­par­a­tive pur­poses WinJUPOS pro­vides a func­tion to bring images to a com­mon mea­sure­ment stan­dard saved by the pro­gram as an Image Mea­sure­ment Set­tings (.ims) le. is be­comes the ba­sis for other in­ter­nal op­er­a­tions such as map gen­er­a­tion and image de-ro­ta­tion.

Step 1

Open WinJUPOS and from the Pro­gram menu op­tion, click on Ce­les­tial Body and select Jupiter. Then from the Record­ing menu op­tion select Image Mea­sure­ment. From the Imag. tab in the win­dow that ap­pears, click Open image (F7).

Step 4

Ad­just the out­line frame to match Jupiter’s limb and ori­en­ta­tion. Ar­row keys move the out­line; N ro­tates clock­wise; P ro­tates coun­ter­clock­wise; PgUp en­larges; PgDn shrinks; and Space ro­tates by 180°. Use LD com­pen­sa­tion to brighten the planet’s limb if re­quired.

Step 2

Some cap­ture pro­grams al­low you to record movie se­quences with file­names that are recog­nised by the WinJUPOS image mea­sure­ment func­tion, au­topop­u­lat­ing the re­quired in­puts pre­sented. Al­ter­na­tively, en­ter the image val­ues un­der the Imag. tab as re­quired.

Step 5

Record as an .ims file via the Imag. tab’s Save but­ton. Re­peat for next (if any) cap­ture images. It is rec­om­mended that once the out­line frame has been set, it’s left un­ad­justed for sim­i­lar images from the same ses­sion.

Step 3

Select the Adj. tab. En­sure the Draw out­line frame box is ticked. Press F11 (or select Au­to­matic de­tec­tion of out­line frame from the right-click menu) to align the frame to the image. Ad­just­ments can be ap­plied (step 4) if the frame is mis­aligned or up­side down.

Step 6

The Opt. tab al­lows ad­just­ment for non-stan­dard sen­sors and image ori­en­ta­tions. In ad­di­tion, the fo­cal length and aper­ture size can be de­fined to cre­ate an ac­cu­rate sci­en­tific record of the cap­ture stored in the saved .ims file.

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