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How do we estimate the size of a star in arcminutes?

Postby mno11407 » Sun Oct 17, 2021 11:08 am

I'm doing the "How Old Is the Universe?" Project and they ask us to find the approximate size of a star in arcminutes with the length on the chart, but I'm struggling to do so. Is there an equation I need to work with?

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Re: How do we estimate the size of a star in arcminutes?

Postby AmyCowen » Tue Oct 19, 2021 4:58 pm

Make sure that you have selected the "grid" and "label" options, as shown in Figure 4.

Step 4 explains and indicates you also need to look at Technical Note 2, that appears below it:
"Using the length scale in the top left corner of the image, estimate the size in arcminutes (see Technical Note #2) of the globular cluster. The size will likely be in the range of 1.5' to 3.0'. Make a note of how big the cluster is in arcminutes, and take a screenshot of the cluster (using the print screen on your keyboard), with the image zoomed as near to the size of the cluster as possible."

Technical Note 2 explains what arcseconds and arcminutes are - and how they are written.

When looking at the image, the "length scale" varies based on your zoom factor. You should see the dimension (e.g., number of arcseconds or arcminutes) noted near the top left of the image.

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