Changes Thumbnail Description and Image

www/archives/archives.shtml

@@ -105,21 +105,42 @@
 					<h2>Thumbnails</h2>
 					<hr />
 					<span style="text-align: center; display: block">
-						<img src="/webdings/help/thumbinfo.png" style="margin: 15px; width: 700px; max-width: 35vw" />
-						<div style="font-style: italic; text-align: center; font-size: 10pt; margin-bottom: 10px; max-width: 35vw;">Two example plots. The left plot shows a poor session, with cloud cover and overexpsure, while the right plot shows a good session with a mostly-clear sky.</div>
+						<img src="/webdings/help/thumbnail.png" style="margin: 15px; width: 700px; max-width: 35vw" />
+						<div style="font-style: italic; text-align: center; font-size: 10pt; margin-bottom: 10px; max-width: 35vw;">
+							Four example plots. The left two plots show a low visibility session, with cloud coverage 
+							and overexposure, while the right two plots show a high visibility seassion with a mostly-clear sky.
+						</div>
 					</span>
 					<p>
 						Folders containing nightly FITS files are summarized by a thumbnail. 
 						This allows for at-a-glance evaluation of a session's quality.
 					</p>
 					<p>
-						The thumbnails are radial plots, where <b>r</b> represents the "visibility" and the angle represents the hour of the night.
-						The visibility <b>v</b> is computed as the average intensity <b>I</b> in the center of every frame, subtracted from the maximum possible intensity:
+						The thumbnails are radial plots, where <b>r</b> for the green/left plot represents the "visibility,"and  <b>r</b> 
+						for the orange/right plot represents the exposure time, and the angle represents the hour of the night. 
+						The visibility <b>v</b> is computed as the average intensity <b>I</b> in the center of every frame, 
+						subtracted from the maximum possible intensity: 
 					</p>
 					<p style="text-align: center">
 						<b>v = 65535 - I</b>
 					</p>
-					<p>Low visibility may indicate the presence of clouds, moonlight, or overexposure.</p>
+					<p>
+						The exposure is the exposure length at a given time with the edge being the maximum exposure 
+						time for each night. This means that the each exposure graph is scaled differently. The longer
+						for a night, the less images taken.
+					</p>
+					<p>
+						We also added a moon visualizaiton along with the name of the moon on that night.
+						An important note is that the moon illumination will have an effect on exposure time.
+					</p>
+					<p>
+						Low visibility and/or low exposure may indicate the presence of clouds, moonlight, or overexposure. 
+                        A way to identify a low visibility session is to look at the exposure graph during variable 
+                        exposure (which we currently use, before around June 2019, fixed exposure was used. Look at the brightness graph for clarity indication). 
+						High variance in exposure typically implies low visibility, but constant 
+                        high exposure often means high visibility
+					</p>
+
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