Optolong

The Optolong Filter Range

The line spans broadband light pollution rejection through single-line narrowband, with the dual and triple-band filters being the most widely used.

• Dual-band filters: Pass Ha and OIII together, which a colour camera's Bayer array separates naturally. The most effective single filter for one-shot colour imaging under light pollution.
• Narrower dual-band options: Tighter passbands giving higher contrast, best suited to slower focal ratios where the passband does not shift significantly.
• Broadband light pollution filters: Reject artificial emission lines while passing most of the spectrum, useful for galaxies and star clusters where narrowband would remove the target's own light.
• Single-line narrowband: Ha, OIII and SII in several bandwidths for monochrome imaging with a filter wheel.
• LRGB sets: Balanced colour separation filters with UV and IR blocking for monochrome broadband imaging.
• Sizes and formats: Mounted 1.25 inch and 2 inch, plus 31 mm, 36 mm and unmounted formats for filter wheels and drawers.

Why Choose David Astro for Optolong

Dual-band filters are the highest-value purchase available to a colour imager in a city, provided the bandwidth suits the optics.

• Focal ratio matched: Very narrow dual-band filters lose performance below roughly f/4 as the passband shifts. We recommend a bandwidth appropriate to your system.
• Camera type considered: We distinguish clearly between what suits a one-shot colour camera and what suits monochrome, since the right filter differs completely.
• Spacing accounted for: Filter thickness shifts focus, and we include it in the back-focus calculation supplied with your order.
• Authorized dealer: Genuine filters with verified coatings and manufacturer warranty, in Canadian stock.
• Ships from Canada: No duties or brokerage fees for Canadian buyers.

Optolong in Canada — Frequently Asked Questions

Which filter for a colour camera in a city?

A dual-band Ha and OIII filter, almost without exception. It gives the largest single improvement available to a one-shot colour imager under light pollution, on emission nebulae.

Will a dual-band filter help with galaxies?

No. Galaxies emit across the spectrum, so a narrow filter removes their light along with the skyglow. Use a broadband light pollution filter, or better, a darker site.

Does bandwidth matter for my telescope?

Yes below about f/4, where a steep light cone shifts a narrow passband away from the emission line. In that case a slightly wider version performs better despite the looser rejection.

Can I use these with a monochrome camera?

Dual-band filters are designed for colour sensors. With monochrome, use single-line filters in a wheel, which gives better control and higher signal per channel.

Imaging in colour from a bright site?

Tell us your camera and focal ratio and we will recommend the right filter. In Canadian stock, shipped worldwide.