DeltaOptical light blue filter #82A 1.25″
Looking for a filter that won't cover your view with a heavy layer of colour, but instead subtly and elegantly refine the rendering of a scene? The DeltaOptical #82A light blue filter in 1.25″ thread is exactly the tool that experienced observers reach for when they want to fine-tune contrast and colour rendition without dramatically darkening the image. It is one of the most popular and versatile filters in astronomical practice - and for good reason.
What is the #82A filter?
The #82A filter is classified as a light blue correction filter with a very low degree of transmission reduction - it passes approximately 73% of light, so the image remains bright and usable even with smaller-aperture telescopes. Its primary purpose is the gentle suppression of warm, yellow-orange wavelengths and the enhancement of the cooler blue spectrum. The result is a more natural and contrastive rendering of surface details, particularly on planets and the Moon.
Practical applications
The Moon
The #82A filter pleasantly reduces the dazzling brightness at full Moon while gently improving the contrast between different surface types - maria, craters and ridges appear somewhat more distinct.
Mars
It helps differentiate polar caps and atmospheric veils from the red surface, making surface features easier to interpret.
Saturn
Cloud bands and atmospheric transitions become easier to follow, giving you a cleaner view of the planet's disc.
The effect is always subtle but measurable - and that is precisely what makes this filter valuable.
Planetary photography
The #82A light blue filter is also popular among planetary photographers working with CMOS or CCD cameras. Thanks to its high transmission, it causes no issues with exposure duration and works well as a balancing filter when used alongside other filters, or as a standalone tool for finer colour tuning of the final image. When used for solar observation in combination with a suitable solar filter, it helps soften contrast and makes longer observing sessions more comfortable.
Construction and compatibility
The filter is mounted in a standard 1.25″ screw thread, compatible with the vast majority of eyepieces and adapters on the market. The build is robust - the glass is ground and polished with emphasis on parallel surfaces to prevent any image degradation caused by the filter itself. The thread is machined precisely, so the filter can be attached and removed without play, remaining firmly in place even during handling of the telescope.
Who is this filter for?
The #82A is an ideal choice for astronomers who want to start using filters without making radical changes to the spectral composition of light. It equally serves experienced observers as part of a filter set, complementing darker filters under varying conditions. Its gentle effect is especially appreciated on nights with good atmospheric stability (seeing), when you have the chance to see fine details - and that is precisely when it pays to have a tool that supports those details rather than erasing them.
About DeltaOptical
DeltaOptical is a brand focused on the practical needs of astronomers and naturalists, with an emphasis on accessible quality optics without unnecessary compromises. DeltaOptical filters are made from optical glass with precisely defined spectral characteristics and undergo quality control to meet the requirements of both beginners and advanced users. The wide range of filter types and sizes makes it easy to build a set tailored to your specific observing goals - from basic colour correction through to narrowband observation of nebulae and emission objects.
Technical specifications
| Parameter |
Value |
| Thread size |
1.25″ |
| Filter type |
Light blue correction filter |
| Designation |
#82A |
| Light transmission |
approx. 73% |
| Compatibility |
Standard 1.25″ eyepieces and adapters |
| Glass |
Optical glass, ground and polished parallel surfaces |
| Recommended use |
Moon, Mars, Saturn, planetary photography, solar observation (with solar filter) |
