Optolong
Optolong UHC Filter 2″
A well-priced broadband-narrowband filter that lifts most emission nebulae out of a light-polluted sky. A strong-value first nebula filter.
87/ 100
Polaris Score
#2 of 7 UHC filters we recommend
From$85
Where to buy
Affiliate link — we earn a commission, you pay the same. We rank on fit, not payout.
01Where it shines
The targets it was made for.
A nebula filter only helps objects that glow at the right emission line — but on those, nothing else comes close. These are the ones it transforms most.
02Be honest with me
What this filter does NOT improve.
Half of buying the right filter is knowing when to leave it in the case. On these targets it makes the view worse, not better — put it away and enjoy them unfiltered.
✕Galaxies
Galaxies glow with broad starlight across all colours. A narrowband filter blocks most of it, they get dimmer, not better.
✕Open clusters
Just stars. There is no nebula emission to isolate, so the filter only dims the very thing you came to see.
✕Globular clusters
Dense balls of stars, again, pure starlight. The filter robs them of brightness and resolution.
✕The Moon
Bright, broadband and reflective. A nebula filter throws away most of the light and adds a colour cast for no gain.
✕Planets
Reflected sunlight, not emission. A narrowband filter does nothing useful here, use it only on emission nebulae.
03Where it fits
Where it lives in your kit.
A filter isn't a standalone instrument — it threads into the light path just before your eye. Here's the chain.
→
→
→
→
04Which filter
How the filter types compare.
A handful of filters cover almost all visual observing. The narrower the band, the more contrast — and the fewer targets it works on.
OIII
Narrowest
Bandpass
~12–18 nm
Best for
Planetary & supernova nebulae
Maximum contrast on the right targets, but only those.
This one
UHC
Broad narrowband
Bandpass
~24 nm
Best for
Most emission nebulae
The versatile all-rounder. A little less punch on Veil-type targets, but works on more of them.
H-Beta
Specialist
Bandpass
~9 nm
Best for
A handful of dim nebulae
The “Horsehead filter.” Superb on a few faint targets, useless on everything else.
Broadband
Light-pollution
Bandpass
Wide
Best for
General city observing
Gently cuts skyglow across the board. Helps a little everywhere, transforms nothing.
05The numbers
What These Numbers Mean
Filter typeNebula
UHC narrowband
It transmits the emission lines nebulae actually radiate and blocks the rest of the spectrum, so the target keeps its brightness while the sky darkens behind it. That contrast gain is what makes faint nebulosity visible from a suburban garden.
What changesSelective
Emission nebulae only
Expect a clear improvement on the Orion, Lagoon and Swan Nebulae and the Veil. Galaxies and star clusters shine by ordinary starlight, so this filter simply dims them and should be left out for those targets.
BandwidthVersatile
Broad UHC passband
A wider passband than an OIII filter keeps the view brighter and works across more objects, which suits telescopes under about eight inches where light is at a premium.
Barrel sizeWide field
2 inch
Threads into 2 inch eyepieces, which is where you want it: large nebulae need low power and a wide true field to be appreciated. A 1.25 inch version is a separate purchase.
ValueEntry
Budget narrowband
It delivers most of the contrast benefit of premium narrowband glass at a fraction of the price, which makes it the sensible first nebula filter before deciding whether an OIII is worth adding.
Optical
TypeNarrowband, UHC
Bandpass≈ 25 nm FWHM
PassesH-β · OIII 496/501
Peak transmission> 90%
BlockingUV–IR
SubstratePolished optical glass
Fit & build
Cell size2″ (M48 × 0.75)
Also available1.25″ · 31 mm unmounted
ThreadingBoth faces threaded
MountAnodised aluminium cell
ReflectionFully multi-coated
UseVisual & imaging
06Pairs with
Compatible gear.
Eyepieces
Low power, wide field
2″ Nagler 31 mm
Frames the whole Veil
32 mm Plössl
Budget wide field
24 mm 68°
The 1.25″ option
Telescopes
The faster, the better
8″+ Dobsonian
Aperture feeds contrast
Fast refractor · f/5–6
Whole-nebula framing
SCT · 8–11″
Use with a 2″ diagonal
Wheels & drawers
For quick in / out
2″ filter drawer
Swap without unscrewing
Manual filter wheel
Carry OIII + UHC together
2″ threaded cell
Threads onto any 2″ EP
07Learn more
Guides for nebula observing.
Guide · 6 min
OIII vs UHC: which nebula filter should you buy first?
Most observers start with the wrong one. When the extra contrast of OIII is worth the narrower range, and when UHC is the smarter first buy.
Read the guide →
Guide · 8 min
Why filters do nothing for galaxies (and everything for nebulae)
The physics behind emission lines, in plain English, so you always know before you look whether the filter will help.
Read the guide →