Buying guide
Filter Upgrade Kit
Updated How we research
Small add-ons that sharpen contrast on every target. The page is split into five sections (Tame the Moon; Filter the Sun safely; Fight skyglow; Boost planetary contrast; Clean up the light path), followed by every pick ranked by our score so you can compare them in one place.
The short version
We compared 20 picks. Our scores range from 7.1 to 8.6 out of 10.
- Best overall:Thousand Oaks Optical 6"x6" Solar Filter Sheet for Telescopes, Binoculars and Cameras White Light Sun Viewing. Highest overall score in this guide at 8.6/10.
- Also great value:SVBONY Telescope Filter 1.25 inches Variable Polarizing Filter for Astronomical Telescope Eyepiece Moon Observation. Value score of 9/10, overall 8.4/10.
- Solid build:Celestron Dielectric Star Diagonal 1.25 inch with Twist Lock 58 Layer Coating 99% Reflectivity. Build and materials score of 8/10, overall 8.6/10.
- Feature-rich:Celestron 94107 Variable Polarizing Moon Filter Reduces Brightness Glare Compatible with 1.25" Eyepieces Lunar Venus. Features score of 8/10, overall 8.4/10.
Scores are our editorial assessment, not customer ratings. How we score
Tame the Moon
- SVBONY Telescope Filter 1.25 inches Variable Polarizing Filter for Astronomical Telescope Eyepiece Moon ObservationOur score8.4/10
- Celestron 94107 Variable Polarizing Moon Filter Reduces Brightness Glare Compatible with 1.25" Eyepieces Lunar VenusOur score8.4/10
- Celestron 94105 Neutral Density Moon Filter Compatible with 1.25" Eyepieces for Lunar Venus Double Star ObservationOur score7.8/10
- SVBONY Telescope Filter 1.25 inches Variable Polarizing Filter Bundle with SVBONY 1.25 inches UHC FilterOur score7.8/10
Filter the Sun safely
- Thousand Oaks Optical 6"x6" Solar Filter Sheet for Telescopes, Binoculars and Cameras White Light Sun ViewingOur score8.6/10
- Explore Scientific Sun Catcher Sun Filter for Refractors and 8 inch SC Telescopes Viewing the Sun in White LightOur score8.4/10
- Thousand Oaks Optical SolarLite Solar Filter Film (ND 5) 3" (76mm) Square Piece for Telescope Sun ObservationOur score8.3/10
- Thousand Oaks 4"x4" Solar Filter Sheet for Telescopes, Binoculars and Cameras Safe White Light Sun FilmOur score8.3/10
Fight skyglow
- SVBONY Telescope Filter 1.25 inches CLS Filter Bundle with UHC Filter and Universal Cell Phone Adapter MountOur score8.4/10
- SVBONY Telescope Filter 1.25" UHC Filter Astrophotography to Improve The Image Contrast Reduces Light PollutionOur score8.1/10
- SVBONY Telescope Filter 1.25 inches UHC Filter Bundle with 1.25 inches CLS City Light Pollution Reduction FilterOur score8.1/10
- SVBONY Telescope Filter 1.25" CLS Broadband Filter for Deep Sky Visual Astronomical Photography Reduce City Light PollutionOur score7.8/10
Boost planetary contrast
- Astromania 1.25-Inch Telescope Eyepiece Filter Set (6 Pieces), Variable Grey Polarizing Filter, 5 Planetary Color FiltersOur score8.4/10
- SVBONY Telescope Filters 1.25" Moon, CPL, Five Color Filter Kit (7PCS) Enhance Lunar Planetary Views and ContrastOur score8.4/10
- SVBONY SV127 Telescope Filter Eyepiece Filter Set 1.25 Inch for Telescope Eyepiece with Storage Case for Planetary DetailsOur score7.9/10
- Celestron Accessory Kit with Five 1.25" Plossl Eyepieces, 2x Barlow and Filter Set for TelescopeOur score7.1/10
Clean up the light path
- Celestron Dielectric Star Diagonal 1.25 inch with Twist Lock 58 Layer Coating 99% ReflectivityOur score8.6/10
- SVBONY SV188P Telescope Diagonal, 2" 90°Mirror Diagonal 99% ReflectivityOur score8.4/10
- SVBONY SV188P Telescope Diagonal 1.25" 90°Mirror Diagonal 99% ReflectivityOur score8.1/10
- Astromania Telescope Diagonal 2" 90° Diagonal Mirror 99% Reflective CoatingOur score8.0/10
All 20 picks, ranked by our score
Every product from the sections above, listed once. Sort by the criterion you care about most, or tick up to three to compare.
#1Thousand Oaks Optical 6 x 6 inch solar filter sheet for making safe white light filters for telescopes, binoculars and cameras.
Fit for the job 9/10 · Features and specs 8/10 · Build and materials 8/10 · Value 9/10
- + Sheet lets you build a custom full-aperture filter sized to your instrument
- + White light filter shows sunspots and eclipse phases safely when properly fitted
- + Works for telescopes, binoculars and cameras with one purchase
- - Must be mounted securely over the full front aperture, never used loosely or behind an eyepiece
- - DIY cell building takes care, and any pinhole or tear means the film must be replaced
#2Celestron 1.25 inch dielectric star diagonal with twist lock and 58 layer coating for 99% reflectivity.
Fit for the job 9/10 · Features and specs 9/10 · Build and materials 8/10 · Value 8/10
- + 58 layer dielectric coating reaches 99% reflectivity for bright views
- + Twist lock holds eyepieces securely without marring barrels
- + Celestron quality suits refractors and SCTs
- - Priced above basic diagonals with similar coating claims
- - Small-barrel format rules out wide-field 2 inch eyepieces
#3SVBONY 1.25 inch variable polarizing filter for telescope eyepieces, designed for comfortable Moon observation.
Fit for the job 9/10 · Features and specs 8/10 · Build and materials 7/10 · Value 9/10
- + Variable polarizer lets you dial in exactly the right lunar brightness
- + Reduces glare so crater detail stands out near full Moon
- + Fits standard 1.25 inch eyepiece threads
- - Dual polarizers add two glass surfaces that can slightly lower contrast
- - Adjusting rotation can be fiddly in the dark
#4Celestron 94107 variable polarizing Moon filter that reduces brightness and glare for lunar and Venus viewing.
Fit for the job 9/10 · Features and specs 8/10 · Build and materials 8/10 · Value 8/10
- + Variable density adjusts brightness for the Moon, Venus and bright planets
- + Celestron quality ensures a good fit on 1.25 inch eyepieces
- + Helps preserve night vision after bright lunar views
- - Priced higher than generic variable polarizers
- - Rotation adjustment may be stiff or loose depending on unit
#5Explore Scientific Sun Catcher filter for refractors and 8 inch SC telescopes to view the Sun in white light.
Fit for the job 9/10 · Features and specs 8/10 · Build and materials 8/10 · Value 8/10
- + Ready-made front filter avoids DIY film mounting mistakes
- + Designed to fit refractors and 8 inch SC telescopes securely
- + White light views show sunspots and solar eclipses safely
- - Fit depends on tube diameter, so measure your telescope before buying
- - Check the filter for damage before each use and never use a torn or scratched one
#6SVBONY 1.25 inch CLS filter bundle with a UHC filter and universal cell phone adapter mount.
Fit for the job 9/10 · Features and specs 8/10 · Build and materials 7/10 · Value 9/10
- + CLS and UHC filters cover broadband city glow and narrower nebula contrast
- + Universal cell phone adapter lets you snap filtered views through the eyepiece
- + Bundle is a practical starter kit for suburban deep-sky observers
- - Phone adapter is basic and can take patience to align with the eyepiece
- - Two filters stacked or swapped often means fumbling in the dark
#7Astromania 1.25-inch eyepiece filter set of 6 pieces with a variable grey polarizing filter and 5 planetary color filters.
Fit for the job 9/10 · Features and specs 8/10 · Build and materials 7/10 · Value 9/10
- + Variable grey polarizing filter adjusts brightness for bright lunar views
- + 5 planetary color filters bring out features on Mars, Jupiter and Saturn
- + 6 piece set covers both the Moon and planetary observing
- - Stacking filters reduces light quickly in small telescopes
- - Color filters take experimentation to see useful benefits
#8SVBONY 1.25 inch Moon, CPL and five color filter kit, 7PCS, to enhance lunar and planetary views and contrast.
Fit for the job 9/10 · Features and specs 8/10 · Build and materials 7/10 · Value 9/10
- + Moon and CPL filters reduce glare for comfortable lunar observing
- + Five color filters help bring out planetary details
- + 7PCS kit offers good variety in one purchase
- - Many filters in a budget kit may vary in optical quality
- - Light loss from filters can be noticeable in small telescopes
#9SVBONY's SV188P 2 inch, 90-degree dielectric diagonal with reflectivity stated at up to 99% and a 2 inch to 1.25 inch adapter included. A budget way into 2 inch wide-field eyepieces.
Fit for the job 9/10 · Features and specs 8/10 · Build and materials 7/10 · Value 9/10
- + Dielectric coating with reflectivity up to 99%, described as more durable than an enhanced aluminum coating
- + Comes with a 2 inch to 1.25 inch converter and supports 2 inch filters, so both eyepiece sizes work
- + Brass pressure ring protects eyepiece barrels, and the interior is matte treated to cut stray light
- - Uses a side screw lock, not the twist-lock collar found on the pricier diagonals in this guide
- - Mirror accuracy is stated as 1/4 wavelength, a looser figure than premium diagonals quote
#10Thousand Oaks Optical SolarLite ND 5 solar filter film, a 3 inch (76mm) square piece for telescope Sun observation.
Fit for the job 9/10 · Features and specs 7/10 · Build and materials 8/10 · Value 9/10
- + ND 5 density is the standard safe level for direct white light solar viewing
- + 3 inch square piece suits small telescopes, finders and binocular objectives
- + SolarLite film gives a natural looking Sun image
- - Small piece only covers small apertures, so larger scopes need bigger sheets
- - Needs a secure homemade cell over the front of the scope before any Sun viewing
#11Thousand Oaks 4 x 4 inch solar filter sheet for building safe white light Sun filters for small telescopes, binoculars and cameras.
Fit for the job 9/10 · Features and specs 7/10 · Build and materials 8/10 · Value 9/10
- + 4 x 4 inch sheet is a handy size for binocular objectives, finders and small refractors
- + Safe white light film shows sunspots and eclipse phases once mounted in a proper cell
- + Lets you make a filter that exactly matches an odd-sized front aperture
- - Too small for most mid-size telescopes, which need a larger sheet or ready-made filter
- - Film must be taped into a secure full-aperture cell, since a loose sheet can blow off in wind
#12SVBONY 1.25 inch UHC filter that boosts nebula contrast and cuts light pollution for visual use and astrophotography.
Fit for the job 9/10 · Features and specs 7/10 · Build and materials 7/10 · Value 9/10
- + UHC passband darkens the sky background so emission nebulae stand out
- + 1.25 inch threads fit most eyepieces and small camera adapters
- + Low price makes it an easy first nebula filter to try
- - Does little for galaxies and star clusters, which emit broad-spectrum light
- - Dims the whole view noticeably in telescopes with small apertures
#13SVBONY 1.25 inch UHC filter bundle with a 1.25 inch CLS city light pollution reduction filter.
Fit for the job 9/10 · Features and specs 7/10 · Build and materials 7/10 · Value 9/10
- + Pairing UHC and CLS lets you choose strong or gentle light pollution control
- + Standard threads fit most eyepieces and camera nosepieces
- + Bundle value is better than buying both filters separately
- - No phone adapter in this bundle, unlike the similar SVBONY kit
- - Filters cannot make a bright city sky as good as a dark site
#14A 1.25 inch, 90-degree dielectric mirror diagonal with a stated reflectivity of over 99%. A low-cost upgrade for the diagonal on small refractors and Cassegrains with a 1.25 inch focuser.
Fit for the job 9/10 · Features and specs 7/10 · Build and materials 7/10 · Value 9/10
- + Dielectric coatings on a super-flat mirror reduce reflected light loss, with the surface stated at over 99% reflective
- + 1.25 inch nosepiece accepts standard 1.25 inch filters, and the body takes 1.25 inch eyepieces and Barlow lenses
- + Brass compression ring with thumbscrew holds the eyepiece firmly without scratching the barrel
- - 1.25 inch format only, so it cannot take 2 inch wide-field eyepieces on a larger focuser
- - The view is upright but reversed left to right, as the listing notes, which is normal for a mirror diagonal
#15A 2 inch, 90-degree dielectric mirror diagonal with a stated 99% reflectivity and a Pyrex glass mirror. It ships with an SCT adapter and a 2 inch to 1.25 inch adapter for refractors and Cassegrains.
Fit for the job 9/10 · Features and specs 8/10 · Build and materials 8/10 · Value 6/10
- + Multi-layer dielectric coatings on a super-flat Pyrex mirror, with reflectivity stated at over 99% for brighter images
- + Includes both an SCT to 2 inch adapter and a 2 inch to 1.25 inch adapter, so it takes both eyepiece sizes
- + Listed as suitable for refractors, Schmidt-Cassegrains, ACF, EdgeHD and Maksutov-Cassegrain telescopes
- - The listing says it is not recommended for reflectors, especially Newtonians, so it is no use on a Dobsonian
- - Costs about twice as much as the budget 2 inch dielectric diagonal in this guide for the same stated reflectivity
#16SVBONY SV127 1.25 inch telescope eyepiece filter set with storage case for enhancing planetary details.
Fit for the job 9/10 · Features and specs 7/10 · Build and materials 7/10 · Value 8/10
- + Color filters help reveal surface markings on Mars and cloud belts on Jupiter
- + Storage case keeps filters clean and organized between sessions
- + Standard 1.25 inch threads fit most eyepieces
- - Colored filters dim the image, which can be hard in small apertures
- - Check the filter set contents before buying to confirm colors included
#17Celestron 94105 neutral density Moon filter for 1.25 inch eyepieces, for lunar, Venus and double star observation.
Fit for the job 8/10 · Features and specs 7/10 · Build and materials 8/10 · Value 8/10
- + Neutral density cuts brightness evenly without adding a color cast
- + Useful for Venus and splitting bright double stars
- + Simple fixed filter with no parts to adjust at night
- - Fixed density cannot be adjusted for different Moon phases
- - May be too dark for small telescopes when the Moon is only a thin crescent
#18SVBONY 1.25 inch variable polarizing filter bundled with an SVBONY 1.25 inch UHC nebula filter.
Fit for the job 8/10 · Features and specs 8/10 · Build and materials 7/10 · Value 8/10
- + Variable polarizer handles Moon glare while UHC improves nebula contrast
- + Bundle covers both lunar and deep-sky filter needs
- + Standard 1.25 inch threads fit most eyepieces
- - UHC filter is not a Moon filter, so half the bundle serves a different job
- - UHC benefits are limited for galaxies and small telescopes
#19SVBONY 1.25 inch CLS broadband filter to reduce city light pollution for deep sky visual and astronomical photography.
Fit for the job 8/10 · Features and specs 7/10 · Build and materials 7/10 · Value 9/10
- + Broadband CLS design keeps more star color than narrow UHC filters
- + Helps cut sodium and mercury streetlight glow from suburban skies
- + Works for both visual observing and entry-level imaging
- - Broadband filters give a milder contrast boost than UHC on nebulae
- - Modern LED streetlights are harder to block with CLS-style filters
#20Celestron accessory kit with five 1.25 inch Plossl eyepieces, a 2x Barlow and filter set, broader than a filter kit alone.
Fit for the job 6/10 · Features and specs 8/10 · Build and materials 7/10 · Value 8/10
- + Five Plossl eyepieces plus a 2x Barlow cover a wide range of magnifications
- + Included filter set lets you start experimenting with planetary contrast right away
- + One kit fills out a bare starter telescope with eyepieces, Barlow and filters together
- - Eyepieces add bulk and cost that filter-only buyers do not need
- - Budget Plossl eyepieces offer narrower views than modern wide designs
Popular right now
- Best Intervalometers for Automated Astro Shots (2026)Buying guide
- Best Finder Scopes to Locate Targets Fast (2026)Buying guide
- Telescope Aperture and Magnification ChartArticle
- Best Star Diagonals for Comfortable Viewing (2026)Buying guide
- Best Red Flashlights to Protect Night Vision (2026)Buying guide
- Equatorial mount explainedGlossary
Based on the last 28 days of search and visitor data.
Stargazer Nest curates picks for US shoppers. Scores are our editorial assessment. We may earn a commission from links on this page.