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of this week. Mercury is visible in the western sky about 30 minutes after sunset. Mercury is in the constellation of Gemini shining at magnitude 0.5 on the 15th. The quick tutorial on magnitudes. The magnitude scale is an inverse logarithmic scale, meaning as the magnitudes increase the apparent brightness of an object decreases by a factor of about 2.5. The dimness object that the human eye can see under optimal conditions is about 6 magnitude. So a magnitude 5 object is 2.5 times brighter than a magnitude 6 object. Well, a magnitude 7 object is 2.5 times dimmer. Venus is setting about 11 p.m. this week. Look for Venus to the last about 30 minutes out.