7 January 2011

Filters

I have seen several listings of filters and what they are good for and the ones I have seen so far have always been arranged by filter color which seems bass ackwards to me. It is like the people who write these lists are saying

“Gee, I have this red filter. What can I look at with it?”

I approach filters from the other side of the coin saying

“I am not seeing as much detail in Jupiter as the space telescope pictures tell me is there. Do I have a filter that will alter the view to let me see more?”

So I have been collecting filter data and have organized it by object so it is easier for me to use.

Sources: Celestron; Astronomy Hacks

Sun
Wratten	Color	Use
#21	Orange	With a Mylar filter, adding the orange filter will return the Sun to its “true” color

Moon
Wratten	Color	Use
#8	Light Yellow	Improves contrast Better appearance of features
#12	Yellow	Improves contrast Better appearance of features
#15	Deep Yellow	Enhances features
#21	Orange	Greatly enhances features
#25	Red	Improves features
#47	Violet	Improves detail
#56	Light Green	Enhances features
#58	Green	Enhances features
#82A	Pale Blue	Brings out low contrast features
#80A	Blue	Enhances detail
Moon	Neutral Density	Reduces brightness making it more comfortable to view the Moon Improves contrast Brings out detail Clear aperture is 21mm, ~84% of normal; 18% transmission

Mercury
Wratten	Color	Use
#21	Orange	Reduces brightness of sky during daytime/twilight Brigs out surface features
#25	Red	Improves observation in twilight when the planet is near the horizon During daylingt, reduces brightness of sky Brings out surface eatures
#29	Deep Red	Improves sky contrast during daytime and twilight Brings out surface features
#47	Violet	Observing clouds Improves contrast Brings out features
#80A	Blue	Improves dusky surface markings at twilight when the planet is near the horizon

Venus
Wratten	Color	Use
#11	Yellow-Green	Observing clouds
#15	Deep Yellow	Reveal low-contrast surface features Observe Clouds Observe ice caps
#21	Orange	Reduces sky brightness during daytime observing
#25	Red	Reduces brightness of daytime sky Terminator deformations
#29	Deep Red	Inproves daytime and twilight sky contrast Observe clouds Increases Contrast Brings out surface detail
#47	Violet	Observe clouds Improve contrast Brings out detail Favorite Venus filter for many observers
#56	Light Green	Observing clouds Reduces daytime sky brightness
#58	Green	Observing clouds Reduces daytime sky brightness
#80A	Blue	Increases contrast of dark shadings in upper clouds
#38A	Deep Blue	Observe clouds

Mars
Wratten	Color	Use
#8	Light Yellow	Observe maria
#11	Yellow-Green	Observe maria Observe ice caps
#12	Yellow	Observe maria
#15	Deep Yellow	Reduce light from blue and green areas which darkens the maria, oases and canal markings, while lightening the orange-hued desert regions Sharpens boundaries of yellow dust clouds Increases contrast
#21	Orange	Reduce light from blue and green areas which darkens the maria, oases and canal markings, while lightening the orange-hued desert regions Sharpens boundaries of yellow dust clouds
#25	Red	Observe polar ice caps Observe surface features sharpens boundaries of yellow dust clouds
#29	Deep Red	Observe Maria Observe ice caps Observe surface detail
#47	Violet	Observe ice caps
#56	Light Green	Observe dust storms observe ice caps Observe dust storms
#58	Green	Excellent to increase contrast of polar ice caps, low clouds and yellowish dust storms
#82A	Pale Blue	Brings out low-contrast features Improves detail
#80A	Blue	Observe dust storms
#38A	Deep Blue	Observe dust storms

Jupiter
Wratten	Color	Use
#8	Light Yellow	Observe belts
#11	Yellow-Green	Observe clouds Improves feature contrast
#12	Yellow	Observe belts
#15	Deep Yellow	Penetrate and darken atmospheric currents containing low-hue blue tones Enhance orange and red features of the belts and zones Useful for polar cap studies Increases contrast
#21	Orange	Improves appearance of detail revealed in structure of belts Enhances festoons Enhances polar regions
#25	Red	Used to study bluer clouds Observe belts Observe transits
#29	Deep Red	Observe clouds Observe belts Observe transits
#56	Light Green	Observe Clouds Increase low-contrast detail
#58	Green	Observe clouds Reduces sky brightness during daytime
#82A	Pale Blue	Observe low-contrast features Increase observed detail
#80A	Blue	Enhance boundaries between the reddish belts and adjacent bright zones Observe Great Red Spot
#38A	Deep Blue	Observe belts Observe Great Red Spot

Saturn
Wratten	Color	Use
#8	Light Yellow	Observe belts
#11	Yellow-Green	Observe the Cassini Division
#12	Yellow	Observe belts
#15	Deep Yellow	Increases contrast
#21	Orange	Improves band structure Highlights blue polar regions
#25	Red	Observe bluer clouds
#29	Deep Red	Observe clouds
#47	Violet	Observe ring structure
#56	Light Green	Observe clouds Observe surface detail
#58	Green	Observe clouds Observe belts Observe polar regions
#82A	Pale Blue	Observe low-contrast features Increases observed detail Observe cloud belts
#80A	Blue	Penetrate and darken atmospheric currents containing low-hue blue tones Enhance orange and red features of belts and zones
#38A	Deep Blue	Observe rings Observe belts Observe clouds

Uranus
Wratten	Color	Use
#8	Light Yellow	Increases observed detail
#11	Yellow-Green	Increases contrast Increases observed detail
#12	Yellow	Increases observed detail
#15	Deep Yellow	Improve detail in larger telescopes (>10”)

Neptune
Wratten	Color	Use
#8	Light Yellow	Increase observed detail
#11	Yellow-Green	Increase contrast Increase observed detail
#12	Yellow	Increase observed detail
#15	Deep Yellow	Improve detail in larger telescopes (>10”)

Comets
Wratten	Color	Use
#8	Light Yellow	Increases observed detail
#15	Deep Yellow	Enhances tail definition
#21	Orange	Enhances definition in dust trails and heads in larger telescopes (>10”)
#58	Green	Useful for observing brighter comets
#82A	Pale Blue	Observe comet tails
#80A	Blue	Best definition in gast tails
#38A	Deep Blue	Bright comet tails

Galaxies
Wratten	Color	Use
#82A	Pale Blue	Observe detail in bright galaxies