ASTRONOMIK · DEEP-SKY IMAGING
Less skyglow.
More room for deep-sky detail.
The Astronomik CLS CCD filter helps separate faint astronomical targets from a light-polluted background, suppressing selected unwanted wavelengths while transmitting important nebula emission lines.
With integrated infrared blocking and compatibility with CMOS, CCD and DSLR cameras, it brings two useful imaging functions together in one optical filter.
Help your target stand out
Reduces selected wavelengths associated with traditional sodium and mercury lighting, improving the separation between your target and the background sky.
Keep valuable nebula signal
High transmission at H-alpha, H-beta and OIII retains key emission lines, with wider passbands than a UHC filter for less star dimming by comparison.
IR blocking built in
Particularly useful for infrared-sensitive cameras without their own effective IR-cut filter, including suitable modified DSLR and astronomy camera setups.
Designed around the light you want to capture
The CLS CCD transmits two broad spectral windows: 450–520nm and 640–690nm. These include the blue-green emission of H-beta and OIII, together with the deep-red H-alpha emission found in many nebulae.
It selectively filters the incoming light to improve contrast where the unwanted skyglow falls within its blocked wavelengths.
Manufacturer-stated transmission at the listed wavelengths. These values do not represent total system throughput.
A useful choice for…
- Emission nebula imaging: retains important hydrogen and oxygen emission lines.
- CMOS and CCD cameras: suitable for modern dedicated astronomy cameras, despite the CCD name.
- Modified DSLRs: useful where the imaging system needs infrared blocking alongside light pollution suppression.
- Unmodified DSLRs: can improve contrast, with colour correction expected during processing.
CLS CCD or standard CLS?
The main difference is infrared blocking.
Choose the CLS CCD when you need light pollution suppression and an IR-cut function in the same filter.
If your camera or imaging train already blocks infrared effectively, the standard CLS may be a more economical option.
Check your camera specification: a protective sensor window does not necessarily provide IR blocking.
What to expect under your skies
Performance depends on your local lighting and chosen target. This filter is particularly relevant to the distinct emission lines of traditional sodium and mercury lamps. Broad-spectrum white LED lighting is harder to separate from astronomical signal.
Galaxies, reflection nebulae and star clusters emit across a broad spectrum, so some useful target light is also removed. Results vary, and colour calibration remains part of the imaging process.
| Filter function | Light pollution suppression with integrated infrared blocking |
|---|---|
| Camera types | CMOS, CCD and DSLR |
| Transmission bands | 450–520nm and 640–690nm |
| H-beta transmission | Approximately 95% at 486nm |
| OIII transmission | Approximately 95% at 496nm and 501nm |
| H-alpha transmission | Approximately 97% at 656nm |
| Focal ratio range | f/1.8–f/15 |
| Optical glass thickness | 1mm for standard versions; XT versions differ |
| Construction | Finely polished optical glass with durable, scratch-resistant coatings |
| Environmental resistance | Coatings resistant to humidity and ageing |
| Included accessory | Protective filter storage box |
Choose the fitting that matches your equipment
The CLS CCD range includes threaded, unmounted and camera-specific clip formats. Your selected variant determines the fitting supplied.
For a filter wheel or drawer, check the required diameter, mounting style and clearance. For a clip filter, confirm compatibility with your exact camera body and lens. Threaded 1.25-inch and 2-inch versions require a matching accessory thread.
Your questions answered
Does “CCD” mean it cannot be used with CMOS cameras?
No. The CLS CCD is suitable for both CMOS and CCD astronomy cameras, as well as DSLRs. The important checks are the filter fitting and the requirements of your imaging system.
Do I need a separate infrared-cut filter?
The CLS CCD includes infrared blocking, so a separate filter is generally unnecessary solely for that function. Check your camera and optical system requirements before choosing your filter combination.
Will it preserve the original colour balance?
Selective filtration changes the wavelengths reaching your sensor. Allow for colour calibration during processing, particularly with an unmodified DSLR, rather than expecting unchanged colours straight from the camera.
Will it remove all light pollution?
No. It suppresses selected wavelengths, so the improvement depends on the lighting around your site. It cannot completely remove broad-spectrum skyglow or replace darker observing conditions.
Can I use it for visual observing?
Suitable threaded 1.25-inch and 2-inch versions can be used visually. However, the standard CLS may offer better value because visual observing does not require the CCD version’s infrared blocking.
DARK CLEAR SKIES
The right filter starts with your setup.
Unsure which version to choose? Tell us your camera, telescope or lens, filter holder and preferred targets. We can help you assess whether the CLS CCD is a suitable match and identify the fitting you need.
