Baader Solar Continuum 10 nm filter review

Since approximately July 2017, I have been the owner of a special filter for observing and photographing the Sun – Baader Solar Continuum 1.25″. This is an interference filter that transmits part of the spectrum in the green region at a wavelength of 540 nanometers and a half-bandwidth of 10 nanometers. It is now on sale no, and it was replaced in 2022 by an updated version with a narrower band (7.5 nm) and IR blocking.
The filter housing has an M28.5 thread, both external and internal. The filter is small and the thread height is small, so be careful not to drop it when unscrewing it from the eyepiece, T-adapter, or other filter.

IMPORTANT!
The Baader Solar Continuum filter cannot be used without first filtering sunlight, otherwise you can damage the filter, your eyesight or your camera! It is necessary to use a full-aperture filter, or a Herschel wedge + an additional ND filter. Also, due to the leakage of the filter in the infrared range, I recommend additionally using an IR-cut filter for visual observations. Although, SUDDENLY it turned out that my filter from the old series, when tested with an incandescent lamp through a spectroscope and an IR-sensitive camera (QHY5III462C), DOES NOT LEAK INTO IR.

One more test

Why do you need this filter?
Unlike the hydrogen Al-alpha line (656.28 nm), or the calcium line (393.3 nm), the wavelength of 540 nm does not correspond to any specific solar substance. The main task of the filter is to cut off telescope distortions (for example, chromatism or spherochromatism), since most lens and mirror-lens telescopes are optimized for a wavelength of 546 nanometers.

Another advantage of such a narrow-band filter is the ability to reduce the influence of atmospheric dispersion. This is especially true for shooting the Sun, which is located low above the horizon (less than 30 degrees). When photographing the Sun, I do not use an atmospheric dispersion corrector.

A little about the technique of filming solar granulation
You don’t need to buy a Baader Solar Continuum filter to capture solar granulation.
For a confident appearance of granulation, a telescope with an aperture of 100 millimeters or more is desirable, but even at 66 mm I was able to capture hints of granulation. Of course, it is necessary to select a scale so that individual granules do not fall off the camera pixel.
1. If you are using a color camera, you can only process the green channel in the PIPP program. I’ve done this before, it works.
2. If you are using a color or monochrome camera, you can use a green CCD filter, or a CCD OIII (with built-in IR-cut). In the case of a color camera, we also take only the green channel.
3. To photograph the Sun with the Baader Solar Continuum filter, I use several cameras QHY5III178m (monochrome) and ZWO ASI183MC (color).

When using a Herschel wedge, all filters must be placed between the wedge and the eyepiece or the wedge and the camera! You cannot screw filters in front of the wedge!

SUMMARY

An interesting filter that allows you to obtain exceptionally detailed images of the Sun in a calm atmosphere and a sufficiently large aperture. Before use, I recommend checking the leakage of the filter in the IR range. If in doubt, it is better to use it in conjunction with an IR-cut filter. Many of my photographs of the Sun can be viewed at the link.

Among the analogues, you can also buy the Player One Photosphere filter — the same thing, but from the Chinese and with IR blocking.

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