Astronomy Specialist


$489.00 AUD
SKU: OP-9998


  • 3 nm




The new Optolong L-Ultimate is a dual-band astrophotography filter designed to drastically reduce the effect of light pollution. Its two ultra-narrow 3nm passing bands isolate the nebulae emissions in H-Alpha (red) and OIII (green-blue), maximizing signal and making the sky background dark. The L-Ultimate filter has been optimized for excellent halo performance.


The L-Ultimate is designed for use with optics not faster than f/4. For example, with a RASA at f/2 there will be too much band shifting for the desired signal to pass through.

  • It blocks the artificial light from mercury vapour lamps, both high and low pressure sodium vapour lights and the unwanted natural light caused by neutral oxygen emission in our atmosphere (i.e. skyglow).
  • Maximum transmission of the main nebula emission lines at OIII (500nm) and H-alpha (656nm).
  • Two transmission bands with a bandpass of 3nm.
  • Designed mainly for astrophotography.
  • Ideal for urban areas with extreme light pollution.
  • It incorporates an IR/UV-Cut filter that is necessary in astrophotography, especially for astronomy cameras that are sensitive to the infrared radiation.
  • Ultra-thin filter cell to maximise the compatibility with most filter wheels.
  • Multi-layers anti-reflection coating.
  • Cell in Aerometal Material, CNC machined, sand blasted, black anodized and laser engraved.
  • Plastic PP Case, high pressure EVA Case Lining.

Light pollution filters do not eliminate the effects of light pollution or increase the object’s brightness. It does increase the contrast between nebulae and night sky.



The interferential coating is deposited on the substrate using electron-beam gun evaporation with Ion-assisted deposition coating technology. This increases the filter durability and resistance to scratching, as well as stability on CWL (central wavelength) and no deviation affected by temperature changes. The planetary rotation system offers precision and homogeneity of coatings ensuring high transmission of pass-band and high optical density off-band.

WARNING: Optolong filters are not designed for sun observations. DO NOT LOOK AT THE SUN WITH OPTOLONG FILTERS. You could become BLIND if you fail to observe the warning.


Optolong L-Ultimate halo performance test


The L-Ultimate has excellent control of halos around bright stars. Credit: Tommaso Massimo Stella.


Passing band
Dual-band H-alpha and O-III 3nm
Glass thickness
1.85 mm
Optical flatness
1/4 λ (wavefront)
Bandpass transmission ~90%
Fully multi-coated
Surface quality 60/40
Parallelism 30"
Glass type Monolithic optical substrate (non glued)
SKU OP-9998 (1.25"), OP-9999 (2")



NGC7000 in LHaRVB by Nicola Martino | Optolong L-Ultimate, Takahashi FSQ-85EDX, ZWO ASI2400MC Pro




OU-4 by Tommaso Massimo Stella | Optolong L-Ultimate & L-eXtreme, TS PhotoLine 102, Takahashi FS60CB, ZWO ASI294MC Pro




Sh2-132 by Andrea Maggi | Optolong L-Ultimate




W63 by José Jiménez | Optolong L-Ultimate, modified Canon EOS 5D Mark IV


Customer Reviews

Based on 3 reviews
Martin Tymms
A revelation for OSC cameras Users

This filter has revolutionized my shooting in poor skies and created great images in Bortle 2 skies. The ability to extract Ha and OIII channels in AstroPixel Processor gives data to rival monochrome cameras
A must have filter!!

Paul Luciani - Coolhandjo
3nm for all round imaging with L- Ultimate

This filter gives a unique depth to your images over other duel band. I believe it's because of the 3nm band pass and Oiii and Ha combinations. The result is a smooth deep look. However be prepared to image longer with sub time and total integration time as you need that to increase the overall brightness. The quality control is excellent with no issues. Some halos on very bright stars but that's the same with other duel band for OSC. Attached pencil nebula 12 hours 5 min subs 533 osc

The L-Ultimate Outperforms the L-Extreme on Faster Scopes

Having been a fan of the 7nm L-Extreme, I purchased the L-Ultimate based on its' specs, and the 3nm bandpass. I was not dissapointed. For a dual pass narrowband filter, it is ideal for light polluted suburban skies, and at F/7. you can obtain excellent results without hours of intergration. All in all, an excellent purchase, and well worth the price for those that use OSC cameras. Attached is M42 Orion, with only 5 X 5min subs, combined with darks/flats/bias. I have had to shrink the image to less than 10Mb due to site limitiations.



From $489.00 AUD


  • 1.25"
  • 2"

Optical design

Image circle

Focal ratio


Focal length

Optical thickness



Colour or Mono

Pixel size

Sensor dimensions


Sensor diagonal

Quantum efficiency

Read noise

Fullwell capacity

Bit depth


Camera backfocus

Filter size

1.25", 2"

Filter size

1.25", 2"

Bandpass (FWHM)

3 nm

Bandpass (FWHM)

3 nm

Glass thickness

1.85 mm

Mount type

Payload capacity

Latitude range

Dovetail saddle

Slew speed


Periodic error correction

Counterweight shaft

Azimuth adjustment range

Internal diameter

Illuminated diameter

Compatible telescope external diameter





View product