Part 3: Image Analysis

This part of the lab should be completed after a few nights or weeks of observations of a planet. Refer back to the Image Analysis with MaxIM DL lab for more help.

1. With your images,аanimateаthe movement of theаplanetsаyou observed. Describe what you observe. Do you see any retrograde motion? Does the planet cross into another constellation?

2. Look up the mean distance from Earth during your observations in km for the planets.

3. How much did the planet move in angular distance (degrees or radians) between your first and last images? Note: For VAO, the pixel scale is 0.67 arcseconds per pixel or 0.000186 deg/pixel. Remember you can use theа‘area’ mode in the information window (ctrl + i).

4. How far did theаplanetаmove, in km, between your first and last observations?

5. Since you know how much time passed between your first and last observations, how fast is the planet moving in km/s? Remember you can always look at the FITS header (ctrl + f) to look at when the images were taken.

6. Look up the orbital velocity of each planet. How accurate is the speed you calculated? Recalling what you know about how the planets orbit, give reasons as to why your answer is different.


Guideposts

•аWhen was this image taken?

Astronomical images are usually in FITS format, which is essentially a bitmap (i.e. a large, uncompressed image) with a bunch of text attached that gives important information about the image such as when and how it was taken, where the telescope was pointing, etc. You can view this information byаselectingаViewа->аFITS Header Windowаfrom the menu. аSome of the noteworthy pieces of information are: OBJECT - the name of the object the telescope was looking at; DATE-OBS - the date and time the picture was taken; EXPTIME, FILTER - the exposure time in seconds and filter used.

•аAligning Images

Maxim has a tool that can align images that are slightly offset from one another.аSelectаProcessа->аAlignаfrom the menu. Select the names of the images you want to align and click on the right arrow to add them to the list, then click OK. The Align Images window will appear. Here, you have several Alignment Modes from which you can choose. а For these particular images, 'Auto-star matching' works well. You can preview how well your Alignment Mode is working by selecting 'Overlay All Images' before you proceed. аOnce you've selected your Alignment Mode, click OK. аNotice the background stars of both images are now mapped to identical (x,y) pixel coordinates.

•аAnimating/Stacking Images

Once you have aligned images, you can animate them to see the motion of an object. This is useful when you are looking for a moving object that is hard to distinguish from background stars in a single image. You can also stack images, which is helpful if you are trying to measure how much an object moved between successive images. To perform these functions,аselectаViewа->аAnimateаorаProcessа->аStackаfrom the menu.

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