Noctutec anti-reflective varnish for blackening telescopic tubes and components

Noctutec Antireflex Lacquer for blackening telescope tubes and components

Antireflex Varnish Spray Can 400 mlThe Noctutec SL-94 Antireflex Paint Spray is based on the varnish SL-94 smooth. The varnish spray is ideal for varnishing secondary mirror spiders, mirror cells and telescope tubes. The substrates to be varnished must be clean, dry and free of grease. Highly absorbent surfaces such as hard paper must be primed beforehand. We recommend sanding smooth substrates.
Please observe the instructions in the data sheet. This data sheet is enclosed with every can and is available for download below.

The Noctutec Antireflex varnishs were developed in cooperation with a chemist specialised in varnish and a German varnish manufacturer.
The coatings eliminate up to 99.3% of stray light at an angle of 60°. In 20° grazing light even up to 99.9%! Tested according to DIN EN ISO 2813.
The varnishes are available in smooth and rough and also as spray cans, so that the right material is available for every type of application. The varnishs have been specially developed to adhere to almost all surfaces found in the optical field, especially metals and glass.

Observe all instructions from the technical data sheet of the respective product and the PDF file "Application range" at the end of the page. Only use the products in well-ventilated rooms!

A comparison:

Top: Noctutec anti-reflective paint SL-94 rough

Middle: noctutec anti-reflective coating SL-94 smooth

Bottom: Berger anti-reflective paint

All samples were applied with the same brush on identical substrates for comparison.

Test surfaces taken at a flat angle against the light





To achieve the best anti-reflective properties for extremely flat light incidence, it makes sense to use the SL94-grey varnish as a base. A thin layer of Smooth SL-94 is then painted onto this base. The result is a highly matt surface that works particularly well in flat incidence of light.

This application makes sense wherever light rays hit the surfaces at a very flat angle. We advise applying the varnish with a spray gun here.

The first coat is applied with SL-94 rough. Spray pressure 4-6 bar. Nozzle size 1.5 mm. The second coat is painted after the first coat has dried. Use SL-94 smooth for this.

Important: The second coat must be applied with plenty of air and only very little paint. Smaller nozzles can also be used here. The result is a soot-like paint layer. We sometimes use airbrush guns for the second coat. This works very well.

Experiment with a tube inner surface, taken at a flat angle against the light





Procedure:

One coat of SL-94 Rau as a base.

On top of that a thin layer of SL-94 smooth with a lot of air and little colour addition.

The picture was taken in the automatic exposure mode of the camera and not post-processed.

Experiment with a glossy object





Procedure:

SL-94 rough as base

SL-94 smooth as top coat

Apply with a brush

Gloss Level Measurement

The gloss level was measured on 03.06.2019 using a calibrated gloss level meter type Elcometer 480. 12 measurements were taken each at 20°, 60° and 85°.

The average gloss level measured in the 20° grazing light was 0.1%.

The value measured in 60° grazing light had an average value of 0.76666%.

The value measured in 85° grazing light was 5.44% on average.

The minimum value measured in 20° was 0.1%. The maximum value was 0.1%.

The minimum value measured at 60° was 0.7%. The maximum value was 0.8%.

The measured minimum value in 85° was 5.3%. The maximum value was 5.7%.

The combination SL-94 smooth on SL-94 rough could not be tested. This coating structure is especially suitable for extremely flat incident light, i.e. for the range 45° to below 85°. Internal tests, which were not carried out according to DIN, show excellent values here of less than 1% reflection at 85° (according to DIN angle).

The complete DIN ISO 2813 measurement protocol and the technical data sheets are available for download. The download is for personal information only. Please note that the use of this information in any respect is only permitted with our express permission.

Links to further information (currently only available in German)

Noctutec SL-94 Antireflexlack, technisches Merkblatt

Noctutec SL-94 Antireflexlack, Messprotokoll

Noctutec VK-80 Verdünnung, technisches Merkblatt

Welcher Lack für welche Anwendung

Vergleich von Velours und Antireflexlack

Safety informations: PDF Download