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TOPIC: Filters

Filters 11 months 6 days ago #72

  • William and Jena
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We recently purchased a Celestron 6SE and love searching the night sky for what ever interests us. Tonight we observed the Ring Nebulae, (faint due to the super moon) and a question has arisen. Is there a filter that would allow us to see objects such has this in the stunning color you commonly see on the internet?
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Filters 11 months 6 days ago #73

  • Mike Simmons
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Alas, no. Cameras have the benefit of being able to capture light over a long time. Our eyes are more like a quick snapshot. To see colors in the Ring Nebula requires a really big telescope, and then the colors are different than what the camera records. Our eyes are more sensitive to green light and have a hard time picking up red so it's just green to our eyes. Planetary nebulae like the Ring get their name from appearing like the planets Uranus and Neptune -- small, round, and green. There are other smaller, more concentrated planetary nebulae that show the color really well in small telescopes. Cameras can record it all to varying degrees, and differences in sensitivity can be adjusted in the final image.

We have two types of sensors in our eyes. The center of the retina has cones which differentiate colors but aren't very sensitive. Around the center are rods which are monochromatic (something there or not, but no color differentiation) but are more sensitive. During the day when there's plenty of light the cones give us extra information in the form of colors. At night the cones can't pick up the faint light and the signals from the rods are what we see. Look around at night and you'll notice you can't tell what color things are. Same thing in a telescope. The two types of sensors are an adaptation to the different conditions. Without rods we'd be blind at night.

When observing deep sky objects like nebulae, faint clusters, and galaxies you want to take advantage of this and use "averted vision". Sweep your eye across the object and you'll notice that you see more when your gaze is directed to the side of the object instead of straight at it. With practice you can train yourself to look to the side of the object when you're observing faint objects.

Mike
Mike Simmons
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Astronomers Without Borders
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Filters 11 months 5 days ago #75

  • William and Jena
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Thank you for answering our question, we'll take your advice and practice this averted vision technique.
Last Edit: 11 months 5 days ago by William and Jena. Reason: misspelling
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