Being a professional journalist, James knows how to turn any topic into a comprehensive, easy-to-digest text. Even if you've never dealt with telescopes before, rest assured James will explain everything you wanted to know about them better than your physics coursebook.
Charles holds a Master’s degree in Physics Engineering (optics and photonics specialization), has been teaching physics at school for almost 15 years and recently has started teaching a course on optics at a local university. Our irreplaceable website expert.
Last updated: September 19, 2022
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Have you ever looked through a telescope? Did you know that your telescope viewing experience and photographs can be greatly improved by using telescope filters?
The best telescope filters have many different factors to consider. One of these factors is the effect. This is what the filter does. Another thing to think about is the thickness of the glass. Different materials create different effects and are used for different things. The coating of your filter is very important because that is what will keep your filter from being scratched. Compatibility is very important because it determines if your filter will fit on your telescope. Lastly, transmission is the percentage of light that is let through your filter. All of these factors come together to create the best telescope filter for you.
More features: ISO compliant solar safe film, designed for a snug fit, produced by American Paper Optics
The Celestron EclipSmart Solar Filter is designed for Celestron 8” telescopes. It has velcro straps and pads so that the filter is sure to stay on as an extra safety measure. It is ISO compliant. It filters both IR and UV light, as well as 99.999% of visible light. It has been independently tested.
This product is perfect for those who care about safety and own a Celestron 8” telescope. It has two Velcro straps as well as four Velcro pads to make sure it will never move out of place. By filtering 99.999% of visible light, this best telescope filter will be sure to keep your eyes safe. You can rest easy knowing that SAI Global Assurance Services independently tested it.
Why did it make our list?
We love how many telescopes this solar filter for telescopes can fit onto. There are a lot of Celestron 8" telescopes, and they are all of incredibly high quality. We could breathe easily, knowing how much thought went into the product. It was impossible for it to be accidentally hit or fall off the telescope because of the extra adhesive. This means it is extra safe to use with kids.
What is not ideal about it?
There isn’t much that could be better about this telescope filter. We didn’t run into any problems with it. It fit on all the Celestron 8” telescopes perfectly. It would be amazing if it was able to fit on other telescopes as well so more people can enjoy this incredibly safe and well-thought-out product. It takes an extra step to add on all the velcro, and it might be tricky at first, but it is well worth it.
More features: improves image contrast, fits into the 8 RASAs integrated filter mount, optically flat surfaces free of defects
This best telescope filter enhances your 8″ RASA by creating deeper contrast because it darkens the sky by blocking light pollution. It chooses which wavelengths to block but still lets in the right light. It doesn’t block emission nebulae wavelengths, so you can still see the nebula through your telescope.
This is the perfect product for people who live in a city and get a lot of light pollution. If it’s impossible to get to a dark place to use your telescope, this is the light pollution filter for you. It blocks light such as streetlights but still lets in the light from outer space so you can see the image you want to see.
Why did it make our list?
We loved how crisp our images were through this filter! Even in the middle of a city, you can still get a good image by using this filter. It darkens the sky behind the image while blocking unwanted light in order to produce a beautiful picture for you to look at. We were blown away by how much we were able to see even with the streetlights on. This is a must-have for anyone who lives in the city and is passionate about telescopes.
What is not ideal about it?
This filter sometimes worked too well. Sometimes the image was like if someone edited the contrast way too high. At times it made the image feel too edited. We found that even though the images were beautiful, we knew we were looking through a filter. Also, although it works great to block out light, it works best at filtering indirect light rather than the light that is right in the frame. That means if what you want to see is directly behind a streetlight, your image is going to suffer.
More features: parfocal design, minimum exposure times
These color filters are interference filters and also block IR. It blocks red, green, and blue interference depending on which filter you use. They were designed for the Meade Deep Sky Imager PRO CCD Camera but can be used with filter wheels from other companies. These color filters help limit exposure time, and you don’t have to refocus when changing colors.
We found that this product is great when trying to view something in its true color. Sometimes color wavelengths get in the way of properly viewing your image, and with the right knowledge, you will be able to eliminate that problem with these filters. They are also great to learn with if you are new to this concept.
Why did it make our list?
We love so many features! These filters are so sturdy, coming in at 3mm thick. They are transferable to lots of different telescopes because they fit with the standard filter wheel. You don’t have to refocus your telescope every time you change filters, and your exposure times are limited. This limits the chance of your photo being blurry. We loved playing around with these filters to get the best photos.
What is not ideal about it?
These filters can be a little tricky to use if you don’t know what you’re doing. It can be hard to know which filter to use unless you’ve done it before. However, they are a great place to start and learn. The instruction manual isn't very clear, so you'll have to do your own research. Also, we found that it is easy to screw these in too tight and have trouble getting them back off. But all in all, this is a great product and will greatly enhance your photographs.
More features: blocks 99.999% of incoming light, ISO certified
This best solar filter for telescopes will let you safely view the sun. It comes in 10 different sizes to view and image the sun. It is attached using three screws, keeping it incredibly secure. The screws come with the filter. It blocks 99.999% of incoming light keeping your eyes and camera safe.
This product is great for those who own multiple telescopes and want a reliable filter for each one. Coming in ten sizes, chances are you will be able to find a size for you. Being attached by screws, you never have to worry about it shifting in place while you view the sun.
What makes it special?
We love how safe and versatile this product is! We tried it in multiple sizes, and the quality was the same throughout each size. We loved viewing the sun through this filter. Knowing that it blocks 99.999% of incoming light and is attached with screws kept our minds at ease because we knew we were guaranteed to be safe. Our pictures also came out amazing. This is a must-have for people who want to view and photograph the sun.
What cons did we find?
These filters are only for closed tube telescopes and can’t be used with open truss telescopes. Open tube designs will let in extra light, which can damage the telescope as well as your eyes, potentially causing blindness. A light shroud is not enough. This limits the amount and kind of telescopes you can use these filters on. But for the telescopes they are designed for, they definitely do the trick, and you won't have to buy another light filter besides these ones.
Effect type: blocks out most of the visible spectrum
Glass thickness: not specified
Coating: not specified
Compatible with: not specified
More features: transmission level of 98.3%
This is a glass twist-on light pollution blocking lens that can go on your telescope in order for you to look through your telescope or take photographs even if there is light pollution where you live. With this product, it will be as if you are out in the country with no light besides the stars and moon.
This best telescope filter is great for people who live in the city or suburbs but are passionate about looking at outer space through telescopes. It is the best telescope filter for hobbyists because it lets in 98.3% of light, which is a good amount for hobbyists but not the best for professionals.
What are its best features?
We loved how easy this filter is to use. You just twist it on, and you're done. It is great to use with the family and enjoy outer space no matter where you live. Some people think you need absolute darkness to get a good look at the stars, but with this filter, you can do so anywhere. You can teach your children the importance of nature even if you are living in a city with this filter.
What could be improved?
We found that this filter is the best for hobbyists. While it is perfect for a night out with the family at your local park or even from your apartment or backyard, it does not block as much light as other filters on the market. But if you're not taking professional photographs, the difference is minimal. However, if you are looking for professional-grade experience or images, this may not be the filter for you.
Effect type: for reducing the brightness of the moon and improving contrast
Glass thickness: not specified
Material: not specified
Coating: not specified
Compatible with: not specified
More features: allows to observes detailed moon surface, 18% transmission
The Celestron Telescope Moon Filter is a 1.25” filter designed to get rid of glare and create greater contrast while looking at the moon. You can also use it to view bright planets or to reduce glare while gazing at the stars on top of sand or snow. It fits onto most 1.25” eyepieces.
This moon filter is great for people with multiple 1.25” eyepieces who want one product to fit them all. If you are a fan of using your telescope to look at the moon, this is a must-have. It is also incredible for viewing outer space on top of sand or snow, so if you live in a location that has either of those things, this is the filter for you.
What are our favorite features?
We love a lot of things about this product! For starters, it is universal with most 1.25" eyepieces, so you don't have to worry about buying multiple lenses. The increased contrast is impressive. But what we loved most was actually the ability to stand on the beach or in a field of snow and still look up at the sky. Often the reflection from the bright ground gets in the way, but with this filter, you can still enjoy your telescope from a beautiful beach or snowy location.
What could be better?
While the reduction in glare was palpable, it still wasn’t perfect. But for the price point of this filter, it is a significant reduction of glare. It is much better for viewing the moon than it is for viewing bright planets. We found that the image was always better looking through the telescope than it was captured in a photograph. But this filter really shines when on snow or sand.
Things to Consider
Telescope filters make the details better and heighten the image’s contrast. They removed colors and wavelengths of light that are hurting the image. Professionals may use filters for things like classifying stars. But hobbyists mostly just want a clear picture.
Why Do You Need Telescope Filters?
The most common source of light that gets in the way of a clear picture is light pollution, like from street lamps or buildings. You can get colored filters to filter out specific colors that you don’t want. You can also get filters specialized for looking at the moon. Telescope filters help you enjoy the night sky more by improving your image.
There are a lot of important features to consider when thinking about buying the best telescope
Trusted SourceEmily Levesque: How Have Telescopes Transformed Our Understanding Of The Universe? : NPRAstronomers once gazed at the night sky and charted the stars using their naked eyes. Astrophysicist Emily Levesque describes how generations of telescopes have unlocked the wonders of the universe.
filter. The first thing to consider is effect type. This is whether you want something to filter for the moon, to reduce light pollution, to block colors, and things like that. Also, think about glass thickness. The glass is specifically designed to be a certain thickness in order to achieve the desired effect. The thicker, the sturdier. Also, think about the material. Different materials do different things. The coating is very important because it is what protects your filter.
Almost most importantly, think about compatibility. You want to make sure the filter you buy fits the telescope you have. Transmission is the amount of light that is let in; you can think of transmission as a pair of sunglasses.
There are five main types of telescope filters. One is a moon filter
Trusted SourceThe secrets to stargazing from your backyard | Learning holidays | The GuardianThe moon is visible day and the night over the course of a month and on 7 May it will be a supermoon – a little closer to us than normal and appearing around 10% bigger. Look at the moon with your naked eyes and notice the dark and light-grey patches. Light-grey areas are mountainous highlands; the dark grey are long-dried-up lava beds called “seas” because early astronomers took them for actual seas.
. These work similar to sunglasses. They reduce white light and produce a more clear view. The next is light pollution filters. They block light pollution that comes from cities and suburbs. There are also light blue filters, which create a better experience while looking at planets and galaxies. Narrow band filters improve contrast. Lastly, solar aperture filters filter out the sun’s rays to keep your eyes or your telescope from getting damaged. The Meade Glass Solar Filter makes it safe to look at the sun.
The glass thickness is determined by a lot of things. For one, it depends on what you are trying to filter. Some things require thicker glass to filter than other things. It also depends on the percentage of light filtered. Glass thickness will also determine how strong and durable your lens is. Some lenses are curved too. There are pros and cons to having thicker or thinner lenses. It all just depends on what the filter is trying to accomplish. The Celestron Light Pollution Imaging Filter has a glass thickness of 1.9mm.
Some materials used to make telescope filters include paper, glass, and more. Essentially, telescope filters filter out unwanted wavelengths of light and can protect you from UV or IR rays.
Different types of materials filter out different kinds of things. That’s why each kind of telescope filter uses a different kind of material, generally speaking.
The coating of the lens is what protects the lens. Without a coating, the lens can get scratched easily. Coatings have to be tested and applied perfectly so as not to distort the image. They can’t be too thick or too thin, and they have to be perfectly even.
Every lens has a coating because, without a coating, the lens would be too vulnerable because even dust can scratch glass.
The compatibility of a filter means what telescopes it can attach to. Some filters are designed specifically for one telescope or one line of telescopes. Other filters can fit almost any lens of a certain diameter. For example, if you have a universal 1.25” filter, it can fit almost any lens that is 1.25”. But if a filter is made for just one telescope, even if another telescope’s lens has the same diameter, it won’t fit.
Transmission is the amount of light that gets passed through a lens. For example, visible light transmission is how much visible light can pass through the lens. Visible light transmission is known as VLT%. It is a percentage that tells how dark the image will be.
The transmission factor is how much light will reach the sensor of your camera. It depends on how many lenses there are and the glass and coating of the lenses. If the transmission is 100%, that means 100% of the light is reaching your eye or the sensor of your camera.
There are a couple of different kinds of filters that everyone should have. Lunar filters decrease all visible wavelengths of light, kind of like sunglasses. There are two kinds: neutral density filters and two polarizing filters. Planetary filters are one color. They filter out every color except for the color that the lens is. This increases the contrast. It might seem odd at first to see everything in one color, but once you’re used to it, you will be able to appreciate the increased contrast. Lastly, deep-sky filters, or light pollution filters, filter out light pollution from your image. These are the most expensive kinds of filters.
No, there are no filters that are compatible with all telescopes. This is because telescopes all have different-sized lenses. A lot of filters are made specifically for one telescope or a line of telescopes. They are typically manufactured by the same company that made the telescopes. When a filter is specific to a telescope, it takes all the lenses into consideration and is more customized and precise. But there are some filters that fit most lenses of a certain size. For example, there are some 2” filters that will fit most 2” lenses, but still not all of them. It is impossible to make a filter that is universal because every telescope has a different sized lens. Even telescopes with the same size lens have discrepancies which are why a filter will only ever fit most lenses of a specific size if that’s what it’s designed for.
It is important to store filters correctly to avoid dirt or scratches. You have multiple options on how to store your filters. It depends on what’s easiest for you as well as how much money you want to spend. One way to store a filter is to keep it in the protective pouch it came in. But if you have multiple filters, this might not make sense. That’s when lens filter stackers or caps might start to make sense. They are storage that keeps all your same-sized stack filters altogether. Make sure you’re only storing filters together in a container that is made for that. Or else the filters could damage each other. If you keep your filter on the lens, make sure to always put on the cap, especially when you’re not using the camera.
Yes, you need to clean your telescope filters. Otherwise, the quality of your image will be affected. There are right ways as well as correct tools to use. There are also wrong ways and wrong tools. There is a lot of conflicting information that you can find about how to clean a telescope filter. First off, don’t clean your telescope filter unless it needs to be cleaned. It is just unnecessarily touching your filter, which can actually hurt it even if you’re trying to clean it. If there are just a few specs of dust, leave it. You are just risking scratching the glass every time you try to clean it. To clean your filter, get as much dust and dirt off as you can with a blower or soft brush. Then add a few drops of lens cleaning solution to a cleaning cloth. Lastly, use circular motions to clean your filter.
Telescope filters are very important. Without having telescope filters, you can’t customize your experience with your telescope. If you have filters, you can block out colors of light, focus on the moon, see solar eclipses, and so much more. Now that you know about the different features of a telescope filter, you can choose the right filter for you. Our Editor’s Choice, the Celestron EclipSmart Solar Filter, filters out 99.999% of the light, which means you can look at the sun. It has extra security with velcro. Our Best Value is the Meade CCD Color Filter Set, which has a set of colored filters to increase contrast in your image. Our Premium Pick is the Celestron Light Pollution Imaging Filter. With this filter, you can view the sky no matter where you live. Out of these three best telescope filters, there is definitely a filter for you!
Emily Levesque: How Have Telescopes Transformed Our Understanding Of The Universe? : NPR
Astronomers once gazed at the night sky and charted the stars using their naked eyes. Astrophysicist Emily Levesque describes how generations of telescopes have unlocked the wonders of the universe.
The secrets to stargazing from your backyard | Learning holidays | The Guardian
The moon is visible day and the night over the course of a month and on 7 May it will be a supermoon – a little closer to us than normal and appearing around 10% bigger. Look at the moon with your naked eyes and notice the dark and light-grey patches. Light-grey areas are mountainous highlands; the dark grey are long-dried-up lava beds called “seas” because early astronomers took them for actual seas.