How to Use Filters

Use color filters to better observe the planets — but don’t let the name fool you. Filters don’t add or show colors. They exaggerate brightness differences (contrast), making certain features easier to see. So, when you use a filter, look for brightness changes rather than color changes on the planet or in its clouds. 

Manufacturers label color filters along their circumferences. To use one, screw it into the eyepiece’s barrel. All eyepiece filters have threads that match the threaded inside barrels of eyepieces.

All color filters work better with larger telescopes. It’s a simple rule of light throughput. For example, a #47 (violet) filter used with a 4-inch telescope to see cloud features on Venus just doesn’t work. The filter transmits only 3 percent of the light hitting it. However, the same filter used with a 12-inch scope easily reveals features. 

Color filter	Transmission
#8 Light yellow	83 percent
#11 Yellow-green	78 percent
#12 Yellow	74 percent
#15 Deep yellow	67 percent
#21 Orange	46 percent
#23A Light red	25 percent
#25A Red	14 percent
#38A Dark blue	17 percent
#47 Violet	3 percent
#56 Light green	53 percent
#58 Green	24 percent
#80A Blue	30 percent
#82A Light blue	73 percent

খবর বিভাগঃ Articles in English Filer How to Use Filters Using Filter Using filter for eyepiece

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