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
|
0 comments: