Optolong 3nm Dual-Band L-Ultimate Light Pollution Filter

Optolong 3nm Dual-Band L-Ultimate Light Pollution Filter

  (2 Reviews)
✓ 2 year warranty


9x in stock shipped 1-2 working days

About this product

Model:  opt_l-ultimate_2

New L-Ultimate Filter - Dual H-alpha / Oxygen III 3nm Ultra-Narrowband Filter

For One Shot Colour CCD / CMOS / DSLR Imaging - Simultaneously Capture H-alpha and Oxygen III

The advantage of L-Ultimate is that it only passes through the emission lines OIII(500.7nm) and Ha(656.3nm), in which case all other light pollution emission lines are eliminated so that only the emission and reflection signals of the nebula are captured during imaging. Therefore, the sky background of the image is darker, and the contrast between the nebulae and the signal-to-noise ratio are improved to the greatest extent. In heavy light pollution areas, the product can also selectively filter light pollution and clutter signals through the emission lines of nebulae, and finally avoid the impact of light pollution on astrophotography.

It is different from the series of dual-narrowband L-eNhance and L-eXtreme in that L-Ultimate is a dual-3nm bandwidth filter that only passes through Ha and OIII emission lines. You will get a darker sky background, more contrast of the image and the suppression on stars. L-Ultimate has also been optimised in terms of halo performance, so that there is no obvious halo when shooting on a bright star object.

Suitable for use with DSLR, colour/MONO CMOS and CCD astronomy cameras and telescopes with f-ratio f/4 or slower. 

IMPORTANT: Filters manufactured by Optolong are NOT designed for observing or photographing the Sun. DO NOT use Optolong filters to observe or photograph the Sun. If you do it will result in permanent eye damage! 


  • High transmission of H-Alpha and Oxygen III emission lines (avg. 90% or higher)
  • FWHM: Ha 3nm, OIII 3nm
  • Use with colour DSLR, CMOS and CCD Cameras
  • 2" Mounted Filters.
  • 300-1000nm >OD4 Blocking Range
  • Supplied in a protective plastic case with EVA foam lining
  • B270 1.85mm Thick Glass
  • Fine-optically polished on both sides - ensures accurate λ/4 wavefront and <30 seconds parallelism over the both surfaces
  • Ultrasonic wave cleaned substrate with purified water - Cleanup by 13 stage purified water tank to remove impurities and dust effectively
  • Ion source assisted coating— For durability and resistance to scratching, as well as stability on CWL (central wavelength)  - no deviation affected by temperature change
  • Stringent quality testing process - each filter is tested on a spectrophotometer and laser interferometer


L-Ultimate is a 3nn dual band designed to drastically reduce the effect of light pollution, the 3nm isolates the nebulae's emissions into H-Alpha (red) and OIII (green-blue).
It blocks light pollution, maximises the signal from nebulae, and darkens the sky background. It also blocks artificial light from mercury vapor lamps, high and low pressure sodium vapor lights, and unwanted natural light caused by the emission of neutral oxygen in our atmosphere. Maximises the transmission of the main emission lines of the nebula in OIII (496nm and 500nm) and H-alpha (656nm).

Transmission Chart

This is a representative transmission chart for reference only. The production filters may differ slightly based on product testing.

Blue Line - Represents the transmission curve of the L-Ultimate Filter.

The Major Emission Lines of Nebulae: H-α (656.3nm), H-β (486.1nm), OIII (495.9nm) and OIII (500.7nm)

The Major Emission Lines of Artificial Light Pollution: Hg / Mercury (435.8nm, 546.1nm, 577nm and 578.1nm), Na / Sodium (598nm, 589.6nm, 615.4nm and 616.1nm)

Halo Test

Sample Images

Lights: 258x300s (Ou4, L-Extreme) + 30x900s (Sh2-129, L-Ultimate)

Telescope1: Apocromatic TS PhotoLine 102 f/5,6 Triplet FPL53
Telescope2: Takahashi FS60CB @ f/4.2
Camera1: ZWO ASI 294mc Pro
Camera2: Omegon veTEC 571C
Mount: Skywatcher AZ-EQ6 GT
Filters: Optolong Astronomy Filter L-Extreme + L-Ultimate
Processing: DeepSkyStacker, Photoshop CC, PixInsight 
Credit: Tommaso Massimo Stella

Sh2-132 The Lion nebula
Prosegue il test del filtro  Ultimate della Optolong Astronomy Filter
96 light da 300 sec 
No dark no flat
Credit: Andrea Maggi

North America and Pelican nebulae - LHaRVB composition with new L-Ultimate filter
Equipment: Imaging Telescopes Or Lenses
Takahashi FSQ-85EDX
Imaging Cameras: ZWO ASI2400MC Pro
Mounts: Sky-Watcher EQ6-R
Filters: Optolong L-Ultimate 2"
Accessories: ZWO ASIair Plus
Software: Adobe Photoshop °§ Cyril Richard Siril °§ Pleiades Astrophoto PixInsight
Credit: Nicola Martino









O3 3nm+Ha 3nm

Blocking range


Blocking depth

Light pollution  lines blocked >99.9%

Surface quality


Transmitted Wavefront RMS




Customer reviews

Average Rating (2 Reviews):  
Write a Review and share your opinions!

Rating (max 5):  
Optolong ultimate and FLO
14 September 2023  | 

Amazing filter, eliminates so much light pollution and brings out nebulas with minimal exposure. Does a better job than the extreme. Unfortunately, bright stars look a bit weird but nothing is perfect. Also, amazing service from FLO as always, quick delivery and hassle free

Rating (max 5):  
Definitely an upgrade from L enhance
12 October 2022  | 

An excellent narrowband filter, cuts a lot of light pollution and delivers a better contrast in the sky! Do you need longer exposure time? I don’t think so, I usually do 2-4 min subs and that enough to get good data with this filter. Also, I don’t see any halos if that is a concern. Obviously, compared with the L enhance filter, this one gives better results. I don’t have the L extreme to compare. The price is a little bit high but it might be justified. By the way, I used it with a Redcat 51 and a 5” Newtonian f/5.
As always, FLO service was excellent, the filter arrived in less than four days to Mexico!
Thank you FLO!!

Un excelente filtro de banda estrecha, reduce mucho la contaminación lumínica y da un mejor contraste en el cielo!
¿necesitas más tiempo de exposición? No lo creo, normalmente hago subs de 2-4 min y eso es suficiente para obtener buena información con este filtro. Tampoco veo ningún halo si eso es una preocupación. Obviamente, comparado con el L enhance, este da mejores resultados. No tengo un L extreme para comparación. El precio es un poco alto pero puede que esté justificado. Por cierto, lo use con un Redcat 51 y un Newton de 5” f/5.
Como siempre el servicio de FLO fue excelente, ¡el filtro llego en 4 días a México!
¡¡Gracias FLO!!


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