Astronomik
Astronomik UHC Filter 2″
The versatile nebula filter: enough contrast to transform most emission nebulae, broad enough to work on far more of them than an OIII. The one to own first.
90/ 100
Polaris Score
#1 of 7 UHC filters we recommend
From$199.95
Where to buy
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01Where it shinesThe 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.
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.
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 meWhat 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.
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.
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 fitsWhere 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.
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.
A filter isn't a standalone instrument — it threads into the light path just before your eye. Here's the chain.
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04Which filterHow 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.
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.
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.
Dual-band
Imaging only
Bandpass
~3–7 nm × 2
Best for
Colour cameras on emission nebulae
Two narrow windows, H-alpha and OIII, on one piece of glass. Transformative for a one-shot-colour camera in a city, far too dark to look through.
05The numbersWhat These Numbers Mean
5 numbers in plain English · full specifications
05The numbers
What These Numbers Mean
5 numbers in plain English · full specifications
5 numbers in plain English · full specifications
Filter typeNebula
UHC narrowband
It passes the specific wavelengths emission nebulae glow at, chiefly the OIII doublet and hydrogen beta, and blocks nearly everything else. The nebula keeps almost all its light while the sky background goes dark, which is why contrast improves so much.
What changesSelective
Emission nebulae only
The Lagoon, the Swan, the Veil and the North America Nebula gain obvious structure. Galaxies, globular clusters and reflection nebulae shine by starlight rather than emission lines, so a UHC filter does nothing for them and can make them worse.
BandwidthVersatile
Broader than an OIII
A wider passband than a pure OIII filter means it works on more targets and dims the view less, which matters in smaller telescopes. An OIII gives a stronger effect on planetary nebulae and the Veil, but on fewer objects.
Barrel sizeWide field
2 inch
The 2 inch format fits low-power wide-field eyepieces, which is where nebula filters do their best work because you want the whole object in the field. It will not thread into a 1.25 inch eyepiece.
Sky requirementContrast
Helps most under light pollution
It rejects the mercury and sodium emission that makes suburban skies bright, so the gain is largest exactly where the sky is worst. Under a genuinely dark sky the improvement is real but less dramatic.
Optical
TypeNarrowband — UHC
Bandpass≈ 24 nm FWHM
PassesH-β · OIII 496/501 · H-α
Peak transmission> 90%
BlockingUV–IR, deep
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 withCompatible gear.
3 matches for this filter
06Pairs with
Compatible gear.
3 matches for this filter
3 matches for this filter
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 moreGuides for nebula observing.
2 guides that cover this ground
07Learn more
Guides for nebula observing.
2 guides that cover this ground
2 guides that cover this ground
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 →