Astronomik UHC Filter

Astronomik UHC Filter

  (9 Reviews)
✓ 2 year warranty


Out of stock due 4-6 working days

About this product

Model:  ak_uhc_125
Part Number:  10210125

The Astronomik UHC is THE filter for visual observing.

The Astronomik UHC (Ultra High Contrast) filter allows transmission of almost 100% of radiation from both O-III and H beta, and 96% of H-alpha.

Though the second window for the H-alpha-line is not intended for visual observing, it is important when the filter is used with an imaging camera.

All scattered light from other wavelengths, including most artificial light pollution, is filtered out. This reveals a wealth of detail when observing gas nebulae and planetary nebulae.


  • Nearly 100% transmission of O-III & H-beta
  • 96% transmission of H-alpha
  • Blocks most artificial light pollution
  • Ideal all-round deep sky filter, even for small telescopes
  • Not sensitive to high humidity or ageing effects
  • Scratch-resistance!
  • Excellent quality substrate
  • Diffraction limited - the optical performance of your telescope will not be reduced
  • Parfocal with other Astronomik filters
  • 1mm Glass Thickness
  • Supplied in a high-quality, long lasting, filter box

Main use

The Astronomik UHC filters’ remarkably high light transmission improves views of deep-sky-objects, even when used with smaller telescope apertures! (I.e. 2" / 50mm). 

Optimised for use with telescope f-ratios f/4 to f/15.

Transmission losses and chromatic distortions, which arise with other filters, only occur with Astronomik filters when they are used with extremely bright aperture ratios 1:2 and higher! 

Astronomik's UHC filters use very high quality glass and optical coatings so the telescope's native performance is not degraded. 

Transmission Chart

  • The horizontal axis is the Wavelength in Nanometers (nm). 400nm is deep blue, at 520nm the human eye senses green and at 600nm red. At 656nm is the famous "H-Alpha" emission line of hydrogen.
  • The transmission in % is plotted on the vertical axis.
  • The blue line shows the transmission of the filter.
  • The most important emission lines from nebulas are shown in orange. The most important lines are from ionised Hydrogen (H-alpha and H-beta) and double ionised oxygen (OIII).

The major emission lines of artificial light pollution:
| Hg 435,8nm | Hg 546,1nm | Hg 577,0nm | Hg 578,1nm |
| Na 589,0nm | Na 589,6nm | Na 615,4nm | Na 616,1nm |

The major emission lines of nebulas:
H-β 486,1nm | OIII 495,9nm | OIII 500,7nm | H-α 656,3nm


  • Visual observation (dark skies): Very good, for telescopes of all apertures and high exit pupil
  • Visual observation (urban skies): Very good, for telescopes from 100 mm aperture
  • Film photography: Reasonable, but very long exposure time
  • CCD photography: Good, when used with an additional IR-block-filter
  • DSLR photography (original): Good, colour balance shifted but contrast enhanced
  • DSLR photography (astro modified): Very good, colour balance is near perfect
  • DSLR photography (MC modified): Good, when used with an additional IR-block-filter
  • Webcam / Video (Planets): Unsuitable
  • Webcam / Video (Deep Sky): Good, if light pollution is a big problem


Customer reviews

Average Rating (9 Reviews):  
Write a Review and share your opinions!

Rating (max 5):  
2" Astronomik UHC Filter
03 March 2023  | 

Due to numerous reasons I've only used this filter a couple of times and only on the Orion Nebula, however both times I have been blown away by the detail I've seen. I've never seen so much fine wispy detail in the nebula before, absolutely blown away by it. I've only used it with my 4" Esprit 100 so far and I am really looking forward to seeing how it performs with a larger aperture. If you're thinking about getting one of these then don't think about it - get it!

Rating (max 5):  
Thoroughly recommend 1 1/4" Astronomik UHC visual filter.
14 July 2022  | 

I would thoroughly recommend 1 1/4" Astronomik UHC visual filter. I tested it on on the Dumbell nebula through an 8mm Televue Delos EP + 8", F6 Dobsonian + Hilux mirror coating (got to squeeze it to the max after all!). Location: Rural, Time: July, Midnight+. The Moon was setting and the object was high in the sky. The filter very effectively darkened the background and the nebula stood out nicely (almost a 3D effect) with some structure visible.
Likewise for the Ring nebula, however as this remained relatively small in the 8mm EP, it just appeared brighter - still an excellent result.
I don't want to overstate the improvement as all the visual gains that we make are marginal, but they all add up and I'm pleased to have this filter in my optical inventory.

Rating (max 5):  
Amazing filter
22 January 2022  | 

I have only had the chance to use this item once so far. I viewed m42 with it under a full moon and although seeing conditions were far from ideal it popped. A lot of structure was seen in my 8" SCT.

Rating (max 5):  
Astronomik UHC Filter
13 December 2021  | 

I have previously tried several of the cheaper UHC filters and wasnít really impressed. However this changed when I upped my game and bought the Astronomik UHC. The contrast benefit is immense and Iíve spent hours observing targets i used to glance over. Iíve learned that i should have bought this straight out rather than wasting my time and money on sub par filters

Rating (max 5):  
Uhc filter
25 January 2021  | 

Amazing filter. Would recommend for those who are just starting out as I am. Used on the moon, the colour what the filter did was amazing. Definitely will purchase again from FLO. Fast delivery great service 100% +++

Rating (max 5):  
Astronomik UHC
30 October 2019  | 

Simply the best filters out there in my opinion. I've the Astronomik OIII, UHC and H beta. Not the cheapest, but when you factor in time and money spent on your scope, getting to a dark site and then not being able to see some faint DSO as well as you could (or not at all) because your filter isn't up to spec, then they are worth every penny. It's frustrating if you can't see something faint and elusive, then wondering if it's your filter, seeing conditions, scope alignment, etc. With Astronomik filters you don't have to worry about that being the issue. Good resale value as well.

Rating (max 5):  
Really nice effect
18 December 2018  | 

I put this filter on to a 10mm eyepiece after finding the Orion nebula and it made a big difference. Would definitely recommend.

Rating (max 5):  
Astronomik UHC Filter.
02 November 2018  | 

Excellent service as usual from FLO.

Rating (max 5):  
A lovely filter with great bandpass
27 April 2018  | 

I owned a couple of "cheaper" UHCs before eventually moving to Astronomik. I should have saved some money and got the best to begin with! This filter provides lovery starry views of many night sky nebula and it is a regular in all my scopes.


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