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¨  What does 99% safe mean when purchasing a sun filter for a telescope?
¨  Why is Venus blurry when I look through my telescope?
¨  How do you take astronomy pictures with a camera?
¨  What is a pollution filter?

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I was looking into a sun filter but found all the info said 99% instead of 100% safe.  What is the 1% that doesn't make it safe?  Are they as safe as they claim it is?  Looking for the truth about this question.

ANSWER from Imagiverse on 14 August 2006:
You should always look for a reputable company when buying sun filters.  A local astronomy club or telescope shop are good sources.  I would hazard a guess that they say 99% so that they are not liable for any damage that you might get from using the filter.  I'm not sure whether it's the integrity of the product, but rather any damage you might inadvertently do on the filter or its misuse that they they are concerned about.  Ask reputable sources about the product.  If you have anymore questions about it, we might be able to ask one of our astronomy experts for a recommendation.

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When I look at Venus through the telescope with a 3x barlow lens and a 4mm eyepiece, it isn't clear.  I dont see it in great detail.  What should I do?

ANSWER from Roger Herzler on 29 September 2005:
Venus will likely not be clear.  It is essentially one solid color if you can't make out the clouds.  I suspect that your telescope is probably too small to resolve it well, if you're sure that you're in sharp focus.  I've never seen the clouds on it through my 4.5" reflector.  I believe it takes a larger telescope to resolve that kind of detail.

Also, I think you're using WAY too much magnification.  I think the best view of Venus I've ever gotten through my 4.5" is with the 13mm (and no Barlow).

You should see clouds on Saturn and Jupiter, and surface markings on Mars, but Venus is tough.

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How do you take astronomy pictures with a camera?  Where do I get a camera for my telescope?

ANSWER from Roger Herzler on 15 September 2005:
There are many ways to take astronomical pictures.  Simple techniques such as opening the shutter on a camera and leaving it open to the night sky will produce pictures of star trails.  All that's needed for that is a camera capable of the 'bulb' setting (i.e. the shutter can be held open) and a tripod for the camera to rest on.

More advanced techniques include using a camera placed in a telescope eyepiece and using the motor drive of the telescope to prevent star trailing.  Some of the most advanced night photography uses CCD cameras which record digital images of objects much like a digital camera would.  All of these methods have different equipment and different levels of expertise required to perform successfully.  I would like to refer you to some good astrophotography websites for your perusal:

Search Engines:

Basic technique:

Most high-end camera retailers will have astrophotography equipment.  A list of several retailers can be found at:

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What is a pollution filter?  Can you see galaxies and nebulas with large or small city light pollution?

ANSWER from Roger Herzler on 2 September 2005:
"Pollution filters" act to filter specific wavelengths of light.  Like other filters, such as colored filters, you are trying to block unwanted light while preserving the light that most helps to deliver a good image in your eyepiece.  For example, you might use a neutral filter to cut down on Moon glare which should help your views of craters.  The concept is to make your eyepiece show you the most view with the most contrast, etc.

Yes, you can see some nebulas and galaxies from cities.  For example, Orion Nebula is quite a sight from even the most light polluted area.  Your views of them might be improved with the use of filtering.  Your best bet for the best views is always to get to the darkest skies possible first, and then worry about the filtering later.

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Last Updated:
23 September 2006

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