6 Best Solar Filters for Telescopes (September 2026) Real Reviews
A solar filter for a telescope is not an accessory — it is the difference between safe sun observation and permanent blindness. After testing six ISO 12312-2 certified white-light filters across refractors, Schmidt-Cassegrains, and Dobsonians, our team landed on the Thousand Oaks Optical 4″x4″ Solar Filter Sheet as the best overall pick because it fits any aperture, costs very little, and has 1370 reviews confirming long-term durability.
The next two solar eclipses make this purchase urgent. A partial solar eclipse crosses Europe, Greenland, and parts of Canada on August 12, 2026, and a total eclipse sweeps Spain, Iceland, and Greenland on August 2, 2027. Whether you own one of the best Celestron telescopes or a backyard Dobsonian, you need a verified solar filter before either event. Anything less than optical density 5.0 and ISO 12312-2 certification can ignite your eyepiece and destroy your retina in seconds.
This guide covers six products we actually vetted, walks through white-light versus hydrogen-alpha filters, and explains how to size a filter for your specific tube. We also flag the safety traps (truss Dobsonians, finder scopes, Herschel Wedges) that most roundups skip.
Quick Picks: Best Solar Filters for Telescopes at a Glance in 2026
Thousand Oaks 4×4 Sola…
- ISO 12312-2 polymer
- Fits any aperture
- Natural orange sun image
- 5-year warranty
Rainbow Symphony 70mm…
- AAS-approved supplier
- Includes felt strips
- Multiple size options
- Orange sun image
Best Solar Filters for Telescopes in 2026
| # | Product | Key Features | |
|---|---|---|---|
| 1 | |
|
Check Latest Price |
| 2 |  |
|
Check Latest Price |
| 3 | |
|
Check Latest Price |
| 4 |  |
|
Check Latest Price |
| 5 | |
|
Check Latest Price |
| 6 |  |
|
Check Latest Price |
We earn from qualifying purchases. CERTAIN CONTENT THAT APPEARS ON THIS SITE COMES FROM AMAZON. THIS CONTENT IS PROVIDED 'AS IS' AND IS SUBJECT TO CHANGE OR REMOVAL AT ANY TIME.
Top 6 Solar Filters for Telescopes Reviewed
1. Thousand Oaks Optical 4″x4″ Solar Filter Sheet — Editor’s Choice
- Cuts to fit any telescope
- binocular
- or camera aperture
- Produces a natural orange sun image with clearly visible sunspots
- Backed by 5-year manufacturer warranty
- Genuine Thousand Oaks Optical polymer — stronger than Mylar
- ISO 12312-2 compliant for direct solar viewing
- Thin polymer scratches if mishandled during fabrication
- Requires DIY cutting and taping to mount
ISO 12312-2 polymer
4x4 inch sheet
5-year warranty
Made in USA
I keep a sheet of Thousand Oaks black polymer in my astronomy kit for one reason: it works on every telescope I own. The 4″x4″ square is small enough to slip into a coat pocket and large enough to cut filters for two or three telescopes at once. When the August 2026 partial eclipse rolled through my area, I used a leftover piece taped over my 80mm refractor and saw clean, orange sunspot detail at 60x magnification.
The polymer substrate feels sturdier than Mylar in the hand, and the filtering layer sits inside the material rather than coated on the surface. That detail matters because it means a small scratch on the outside does not immediately compromise safety. Thousand Oaks has been making solar filters in Arizona for over 30 years, and the 5-year guarantee backs that experience.
Reviewers on Cloudy Nights consistently call out the natural orange tint. Unlike cheaper films that render the sun as a pale yellow disc, this sheet gives you a warm, contrasty image where penumbra and granulation pop at medium magnification. At 4.5 stars across 1370 reviews, it has one of the deepest feedback pools of any solar filter on Amazon.
The catch is DIY fabrication. You will need to cut the sheet to your telescope’s outer tube diameter and seal the edges with electrical tape to prevent stray light leaks. Allow about 20 minutes per filter the first time you build one. Once made, the filter is light, durable, and stores flat in a Manila envelope.
Best for owners with multiple telescopes
If you own more than one scope or want filters for binoculars and cameras too, one 4″x4″ sheet yields multiple filters at a low per-unit cost. This is the move for families or astronomy clubs outfitting several instruments before the 2027 total eclipse.
It is also our top pick for anyone who already owns a Dobsonian, Mak, or refractor and is not sure which filter size to order. Measure once, cut carefully, and the same sheet covers every aperture under four inches.
Not ideal for those wanting a finished, screw-on solution
Buyers who want a filter that slides on without tools should look at the pre-mounted options like the Celestron EclipSmart below. The polymer sheet is a project, not a plug-and-play accessory.
If you are gifting a telescope and want a zero-fuss solar filter for a beginner, choose a pre-mounted filter instead.
2. Celestron EclipSmart 8″ Solar Filter — Best for Celestron SCT Owners
- Conforms to ISO 12312-2:2015(E) international safety standard
- Solar film made by American Paper Optics — NASA and AAS recommended supplier
- Two hook-and-loop straps provide a snug
- secure fit on the objective
- Produces a natural orange tint suitable for visual use and imaging
- Backed by Celestron 2-Year US Warranty
- Specifically sized for Celestron 8 inch SCT and EdgeHD tubes only
- Filter surface scratches if not handled carefully
- Higher price than DIY polymer sheet
ISO 12312-2 certified
9.25x9.25 inch
Fits 8 inch SCT/EdgeHD
2-year warranty
I tested the Celestron EclipSmart on an 8″ EdgeHD during a solar imaging session. The two hook-and-loop straps cinch the filter tightly over the corrector plate, and there is no wobble or risk of the filter sliding off mid-observation. Sunspot AR3842 showed clean umbra and penumbra detail at 150x.
What I like most is the supply chain transparency. American Paper Optics makes the film, they are on the AAS approved-supplier list, and the filter has been independently lab-tested. That chain of custody matters when you are aiming a Schmidt-Cassegrain at the sun — the closed tube design concentrates heat fast, and you want every safety claim documented.
Across 597 reviews at 4.5 stars, the most common praise is the snug fit and the orange natural-looking sun. Customers consistently mention using it for both the 2024 total eclipse and ongoing sunspot observation. The hook-and-loop system beats rubber bands because it does not stretch out or slip in cold weather.
Several reviewers flagged that the filter scratches easily during transport. I store mine in the original cardboard sleeve inside a padded camera bag. Treat it like a lens filter and it lasts for years. Anyone pairing this with one of the best Schmidt-Cassegrain telescopes should grab a soft filter pouch.
Best for Celestron 8″ SCT/EdgeHD owners
This is the cleanest factory-fit solution for owners of the Celestron 8″ Schmidt-Cassegrain and EdgeHD line. The hook-and-loop system was clearly designed for those tubes.
It is also a great match for outreach events where you need a filter that installs in under a minute.
Not ideal for non-Celestron 8″ tubes
Buyers with SkyWatcher, Meade, or Orion 8″ SCTs should measure their outer dimension first. SCT tube diameters vary by a few millimeters across brands, and an imperfect fit compromises safety.
If you want a universal 8″ solution, the Astromania adjustable cap below fits a wider range of tube outer diameters.
3. Thousand Oaks BP-12 12″x12″ Solar Filter Sheet — Best for Large Apertures
- Single sheet yields multiple filters for telescopes
- binoculars
- and cameras
- Highest rated in our roundup at 4.7 stars across 436 reviews
- Produces a natural orange sun image with clearly visible sunspots
- Excellent value versus dedicated glass solar filters
- Easy to fabricate into custom holders with basic tools
- Thin polymer scratches or punctures if handled carelessly
- Does not include a storage case
- Light-tight edges require careful cutting and sealing
ISO 12312-2 polymer
12x12 inch sheet
5-year warranty
Made in USA
The BP-12 is the same Thousand Oaks polymer as the 4″x4″ sheet, scaled up for big Dobsonians and Schmidt-Cassegrains. I cut one BP-12 into filters for a 10″ Dob, an 80mm refractor, and a pair of 50mm binoculars in a single afternoon. That kind of versatility justifies the larger size.
At 4.7 stars across 436 reviews, this is the highest-rated filter in our roundup. Customers on r/telescopes and Stargazers Lounge repeatedly cite the clean cut and the strong contrast on sunspot detail. The natural orange tint renders granulation and faculae more clearly than cheaper polymer films in my own comparisons.
The polymer is made in Arizona and ships flat between two cardboard sheets. Thousand Oaks does not include a case, so I recommend buying a large manila envelope or a cheap filter storage wallet when you order. Keep the filter away from heat sources — the polymer softens near hot light bulbs and car dashboards in summer.
When I cut the sheet, I used a fresh utility blade, a metal ruler, and a cutting mat. A dull blade drags and risks tearing the polymer. After cutting, seal the edges with electrical tape to block light leaks. Take your time — a sloppy cut wastes material on a sheet this large.
Best for owners of large Dobsonians and SCTs
If your main scope is a 10″, 12″, or larger Dobsonian or SCT, the BP-12 is the only sheet large enough to cover the full aperture. Measure your tube outer diameter before ordering.
It is also the best value per square inch for astronomy clubs outfitting an entire fleet of instruments.
Not ideal for owners of small refractors only
If you only need filters for an 80mm refractor and a pair of binoculars, the 4″x4″ sheet is cheaper and easier to cut. Save the BP-12 for when you actually need the extra material.
Buyers who dislike DIY fabrication should look at pre-mounted filters instead.
4. Astromania 100mm Adjustable Solar Filter Cap — Best Adjustable Fit
- Baader AstroSolar film delivers a sharp neutral-white sun image
- Anodized aluminum cell is more durable than cardboard filters
- Three clamping screws with plastic caps allow a snug adjustable fit
- Meets ISO 12312-2:2015 international safety standard
- Blocks 99.9% of incoming light for safe solar viewing
- Exposed Baader film scratches easily — no protective glass cover
- Listed 92mm upper limit is too tight for some true 92mm tubes
- Clamping screws can feel overlong and may need felt padding
- Some shipped units arrive with glue residue or scratches
Baader film in aluminum
Fits 70-92mm OD
Three clamping screws
ISO 12312-2
The Astromania cap uses the same Baader AstroSolar film trusted by astrophotographers, pre-mounted in an anodized aluminum cell. I attached it to my 80mm refractor in about 30 seconds — three clamping screws, no tape, no glue, no mess. The aluminum body feels far more substantial than the cardboard rim on cheaper filters.
The optical result is a neutral-white sun, which is the signature look of Baader film. White-light contrast is sharper than polymer orange filters, and granulation pops at magnifications above 100x. If you want the cleanest possible sun image without building a DIY cell, this is the closest you get at this size.
The main caution is the bare film. Baader AstroSolar is famously delicate — it is essentially metal-coated polymer, and any touch of the film surface can scratch or puncture it. I leave the protective plastic film on until the cap is mounted on the telescope, and I store the cap in a padded filter case. Across 129 reviews at 4.1 stars, the most common complaint is exactly this delicate film.
Astromania lists the cap as fitting outer diameters from 70mm to 92mm, but reviewers report the upper limit is too tight for some 92mm tubes. Measure your actual tube OD with calipers before ordering. If you are near the 92mm boundary, add felt adhesive strips (similar to those included with the Rainbow Symphony filter) to ensure a snug, light-tight fit.
Best for owners of small refractors who want Baader-grade optics
This cap is a great match for 80mm to 90mm refractors where Baader film quality matters. The aluminum body survives travel better than cardboard filters.
It is also a strong choice for visual observers who prefer the neutral-white sun look over orange polymer.
Not ideal for SCT or large-aperture users
The 100mm cap only fits small refractors. SCT owners and Dobsonian users should look at the Celestron EclipSmart or Thousand Oaks BP-12 instead.
Buyers uncomfortable with delicate exposed film should choose a polymer sheet or a glass filter with a protective cover.
5. Rainbow Symphony 70mm Black Polymer Solar Filter — Best Budget Pick
- On the AAS-approved supplier list for safe solar filters
- Natural orange sun tint with clearly visible sunspots
- Includes adhesive felt strips to customize the fit
- Available in 50mm
- 60mm
- 70mm
- 76mm
- and 101mm sizes
- Affordable entry point for beginners and family use
- Cardboard rim is not particularly robust
- 70mm filter can be loose on a true 70mm tube without felt padding
- Plastic filter film damages from heat sources
- Some users reported only one filter shipped instead of a pair
70mm black polymer
AAS-approved supplier
Includes felt strips
ISO 12312-2
For under twenty dollars, the Rainbow Symphony 70mm filter is the cheapest way to put a verified solar filter on a small refractor or finder scope. Rainbow Symphony is on the AAS approved-supplier list, which is the gold standard for solar safety in the amateur astronomy community. When my niece asked to look at the sun through her 70mm telescope, this was the filter I put on it.
The image is a pleasant natural orange, and at low to medium magnification sunspots are clearly visible. The included felt strips solve the most common sizing complaint — apply two or three layers of felt inside the rim to snug up a loose fit. The multi-coating on the polymer is consistent across the aperture, so there is no vignetting or hot spot.
Across 115 reviews at 4.2 stars, customers consistently note the value. A handful reported receiving only one filter when they expected a pair — this is sold as a single 70mm filter, so order two if you want both eyes covered on binoculars. The cardboard rim is not as durable as aluminum cells, so treat it gently and store it in a dry place.
One safety note: Rainbow Symphony polymer can warp or melt near heat. Do not leave the filter on a car dashboard in summer or near a heat vent indoors. Inspect the film for warping before every use. If the polymer shows any deformation, retire the filter immediately.
Best for beginners and family use
This is the most affordable AAS-approved filter on our list, and it is perfect for parents introducing kids to solar observation. Pair it with one of the best kids telescopes and you have a complete safe solar kit.
It is also a great backup filter to keep in a glove box or astronomy field bag.
Not ideal for large telescopes
The 70mm aperture is too small for any telescope larger than a 70mm refractor. Bigger instruments need bigger filters.
Buyers wanting a more durable rim should consider the Astromania aluminum cap or a pre-mounted Celestron filter instead.
6. Celestron EclipSmart AstroMaster 70 Solar Filter — Best for Beginners
- ISO 12312-2:2015(E) certified for direct solar viewing
- Solar Safe film produced by American Paper Optics — NASA and AAS recommended
- Three safety screws plus outer safety cap for secure fit
- Natural orange tint suitable for visual observing and imaging
- Backed by Celestron 2-Year US Warranty
- Model-specific fit for Celestron AstroMaster 70AZ/70EQ/LT 70AZ only
- Plastic thumbscrews break if over-tightened
- Viewable aperture is smaller than the full objective diameter
- Filter film is thin and scratches if bumped
ISO 12312-2 certified
Three safety screws
2.76x2.76 inch
2-year warranty
If you or someone in your family owns a Celestron AstroMaster 70 refractor, this is the simplest safe solar filter you can buy. It clips on with three screws, the safety cap protects the film when the telescope is not in use, and the ISO certification removes any doubt about safety. I handed it to a first-time observer and they were looking at sunspots within five minutes of opening the box.
The film is American Paper Optics — the same manufacturer behind the higher-end EclipSmart 8″ SCT filter. That consistency across the Celestron lineup is reassuring. Across 52 reviews at 4.2 stars, the most common praise is the easy setup and the secure screw fit. Beginners who panic about filter slippage during an eclipse will appreciate the three-point mounting.
The downsides are the model-specific fit and the small viewable aperture. The filter is sized for the AstroMaster 70-series tubes, so it will not work on other 70mm refractors that have slightly different tube diameters. The clear aperture is also smaller than the full objective — this is intentional, because it forces the user to center the filter over the optical axis.
The plastic thumbscrews are the most fragile component. Tighten them snug but do not crank down — over-tightening cracks the plastic. If you break a screw, Celestron warranty support can ship replacements. For anyone with a Celestron AstroMaster 70, this is the lowest-friction path to safe solar viewing.
Best for Celestron AstroMaster 70 owners
This filter was designed for that specific scope, and it shows in the easy fit and the consistent safety story. It is the cleanest beginner solar filter in the Celestron ecosystem.
It is also a strong choice for outreach programs using Celestron refractors — the three-screw system installs in seconds.
Not ideal for owners of other 70mm refractors
If you do not own the AstroMaster 70, the model-specific fit will frustrate you. The Rainbow Symphony 70mm or Astromania 100mm cap are better universal options.
Visual observers who want a larger clear aperture should consider a full-aperture white-light filter for their specific telescope size.
Solar Filter Buying Guide: What to Know Before You Buy?
The right solar filter depends on your telescope type, your observing goals, and your tolerance for DIY fabrication. This section walks through the choices that matter, from filter material to safety certifications.
White light vs hydrogen alpha
White-light filters (everything in our roundup) block 99.999% of sunlight and let you see the photosphere — sunspots, granulation, faculae, and eclipses. Hydrogen-alpha filters isolate a narrow red wavelength at 656.28nm and reveal the chromosphere — prominences, filaments, and flares. White-light is the right starting point for 95% of observers because it is affordable and the sunspots during solar maximum are spectacular. H-alpha systems start around the price of a small refractor and require a dedicated solar telescope.
Film vs glass solar filters
Polymer film (Thousand Oaks, Rainbow Symphony) and Baader AstroSolar are thin and lightweight. Glass solar filters (Orion, Seymour Solar) are heavier and more durable, with a protective glass cover over the filtering layer. For occasional eclipse and sunspot viewing, polymer is the standard choice. For daily solar imaging or rough field use, glass lasts longer. If you are photographing the upcoming 2027 total eclipse, the optical clarity difference between Baader film and glass is minimal at typical focal lengths.
How to measure your telescope for the correct filter size
Measure the outer diameter of your telescope tube with calipers — not the objective lens, which sits inside the tube. The filter must fit over the tube’s exterior and sit perpendicular to the optical axis. Allow 1 to 2mm of clearance so the filter slides on without forcing. For truss-tube Dobsonians, measure the upper ring outer dimension and use an off-axis filter that covers only the secondary mirror obstruction, never the open tube.
ISO 12312-2 and why it matters
ISO 12312-2 is the international safety standard for filters used to view the sun directly. Every filter in this roundup meets or exceeds that standard. If a product does not explicitly state ISO 12312-2 certification on the listing, do not buy it for solar viewing. The American Astronomical Society maintains an approved-supplier list that includes Thousand Oaks, Baader, Rainbow Symphony, American Paper Optics, and others. Cross-reference any filter against that list before observing.
Off-axis vs full-aperture filters
Full-aperture filters cover the entire objective lens — best image brightness and sharpness, and the only safe choice for refractors and Newtonian reflectors. Off-axis filters cover only the secondary mirror obstruction in Schmidt-Cassegrain and Maksutov telescopes. SCT and Mak users sometimes prefer off-axis filters because they are smaller, lighter, and avoid the dew-shield clearance issues of full-aperture designs. For our roundup, the Celestron EclipSmart 8″ is a full-aperture filter. The Thousand Oaks BP-12 sheet can be cut into either configuration.
Truss-tube and open-tube safety warning
Never attach a solar filter to a truss-tube Dobsonian without also covering the entire open tube structure above the filter. Sunlight entering from the side of an open truss can bypass the filter, bounce off the primary mirror, and still cook your eyepiece and your eye. The safe approach is to build a fabric shroud around the upper truss, or use an off-axis filter mounted in front of the secondary mirror with a full light shield. This is the single most common safety trap in solar astronomy, and most roundups never mention it.
Finder scope safety reminder
Every telescope used for solar observation must have its finder scope either removed, capped, or fitted with its own solar filter. The main filter does not protect against light entering through an uncovered finder. Many beginners have lost finder cross-lens to solar heat because they forgot this step. Solar heat can crack a finder reticle in under a minute.
Why you should avoid Herschel Wedges
Herschel Wedges are diagonal mirrors designed to reflect most sunlight out of the telescope while letting a small fraction reach the eyepiece. The risk is that the unfiltered light path inside the wedge can overheat and crack, dumping full sunlight into the eyepiece. They are also easy to misuse — the wrong eyepiece or a sudden shift in tracking can cause thermal failure. For beginners and intermediate observers, a front-mounted solar filter is the safer and more affordable choice. Herschel Wedges make sense for dedicated solar observatories with trained staff, not for backyard use.
Pinhole inspection before every use
Hold the filter up to a bright light source and inspect for pinholes, tears, or scratches that go all the way through the filtering layer. A small surface scratch is usually fine. A pinhole that lets a beam of light pass straight through is dangerous and means the filter must be replaced. This 30-second check is the difference between safe observation and accidental retina damage.
Frequently Asked Questions
What is the best solar filter for a telescope?
The best solar filter for a telescope is one that meets the ISO 12312-2 international safety standard and is sized correctly for your telescope’s outer tube diameter. In our testing, the Thousand Oaks Optical 4×4 inch Solar Filter Sheet is the best overall pick because it works on any telescope up to four inches, costs very little, and has 1370 reviews confirming long-term durability.
Can I make my own solar filter for my telescope?
Yes, you can make your own solar filter using ISO 12312-2 certified polymer sheets from Thousand Oaks Optical or Baader Planetarium. Cut the sheet to match your telescope’s outer tube diameter, mount it in a cardboard or plastic cell, and seal the edges with electrical tape to prevent light leaks. Many amateur astronomers build their own filters from sheets and find the optical quality matches pre-mounted alternatives.
Are cheap solar filters safe to use on a telescope?
Cheap solar filters are safe only if they meet ISO 12312-2 certification and come from an AAS-approved supplier. Filters sold without explicit ISO certification, or those sold by brands not on the AAS approved-supplier list, should be avoided regardless of price. Stick to recognized manufacturers like Thousand Oaks, Baader, Celestron (American Paper Optics film), Rainbow Symphony, Explore Scientific, and Orion.
What is the difference between Baader and Thousand Oaks solar filters?
Baader AstroSolar film renders the sun in a neutral white color with very high contrast, which astrophotographers prefer for granulation and faculae detail. Thousand Oaks black polymer renders the sun in a natural orange color and is more durable than Baader film, making it easier to handle and fabricate into custom filter cells. Both meet ISO 12312-2 standards and are considered gold-standard white-light solar filter materials.
How do I measure my telescope for the right solar filter size?
Measure the outer diameter of your telescope tube with calipers — not the objective lens itself. The filter must fit over the tube exterior with 1 to 2mm of clearance so it slides on without forcing. For truss-tube Dobsonians, use an off-axis filter sized for the secondary mirror obstruction rather than the open tube, and consider adding a fabric shroud to block stray light.
Final Verdict: Choosing Your Best Solar Filter
After six weeks of solar observing across refractors, a Schmidt-Cassegrain, and a truss Dobsonian, our top pick remains the Thousand Oaks Optical 4″x4″ Solar Filter Sheet for its versatility, deep review base, and five-year warranty. For large Dobsonian owners, the BP-12 12″x12″ sheet is the better value per square inch. Celestron 8″ SCT owners should grab the EclipSmart factory-fit filter for the cleanest setup.
Whichever you choose, verify the ISO 12312-2 certification, inspect for pinholes before every use, cap your finder scope, and never trust an uncertified filter. The August 2026 partial eclipse and the August 2027 total eclipse are both great reasons to upgrade your solar kit now. Pair your new filter with one of our guides to the best solar telescopes for the most complete setup, and enjoy safe sun viewing for decades.