Space and Astronomy News 21st February 2026

Filters for colour astronomy cameras

Duo band filters to help with nebula imaging

We chatted last week about the Olympus OM-3 ASTRO camera from OM System and touched on how this camera allows light from emission nebulae through, instead of blocking it like most DSRL/mirrorless cameras. 

Dedicated colour astronomy cameras like those from ZWO capture the light wavelengths from emission nebula (called Hα or Hydrogen Alpha or sometimes just H-Alpha) as well as another part of the light spectrum where emission nebulae, planetary nebulae and supernova remnants shine. This is around two doubly-ionized oxygen lines (496 and 501nm) called OIII which is the blue-green region.

While colour astronomy cameras see the light from these nebulae and much more in the Milky Way, they also pick up various kinds of light pollution. This can overwhelm the details from deep-sky objects. One way to get around this problem and largely capture light from nebulae is by using a filter that lets the light from H-Alpha and OIII while blocking light from other sources. 

These are often called Duo Band filters as they let in light from just two main parts of the spectrum and do their best to keep the rest out.

This graph shows what light  TMB Pro Series Duo-Band Nebula Imaging Filter lets through, with the two peaks around the Ha and OIII regions. 

What does this mean for taking astro images?

If you're interested in taking photos of nebulae and have either a DSLR/mirrorless or a colour astronomy camera, low cost duo band filters are a handy way to bring out the details and beauty of these wonderful parts of the night sky. 

As they don't let light through from many sources of light pollution, they help those in the city or suburbs where artificial light and sky glow are a problem.

Any downsides?

Yes. You won't see as many stars themselves in images as much of their light is blocked out. They're also not going to produce ideal images for objects that produce light across a wide part of the light spectrum such as galaxies. 

UV/IR Cut Filters for planetary images

The problem: sometimes astro cameras can see too much!

Another type of filter commonly used with colour astronomy cameras are UV/IR Cut Filters.

These types of cameras are sensitive not only to the entire visible light spectrum but also to a little bit either side of the light that we can see.  This goes into the ultraviolet at one end, and in the infrared at the other. Infrared or IR especially focuses slightly different due to its longer wavelength and can wash out some the finer details on planets. 

Light transmission from a TMB UV/IR Cut Imaging Filter showing how it sharply cuts off light from either end of the light spectrum to only through visible light

IR also reduces the sharpness over entire image. With planets, we take lots of shorter exposures rather than longer ones in order to minimize the effects of atmospheric blurring and shakes. Image processing software then just uses the sharper frames and doesn't use the blurrier ones.

Anything that helps this process adds to quality of the final image and these affordable filters are an ideal add-on if you intend to take photos of planets with a full colour of any sort. 

Hubble spots a dark matter galaxy - say g'day to CDG-2 

One of the darkest galaxies ever discovered

Just about all galaxies shine quite brightly and we can view them either because of the light from their millions or even billions of stars. But how do we observe galaxies that are largely made up of dark matter that doesn't reflect or emit light?

Using the Hubble Space Telescope (HST) astronomers have now discovered a galaxy some 300 million light years away called Candidate Dark Galaxy-2 (CDG-2) which seems to be comprised almost entirely of dark matter.

How was this galaxy found?

Using a combination of the Hubble Space Telescope, ESA’s Euclid space observatory, and the ground-based Subaru Telescope in Hawaii astronomers were able to isolate four globular clusters. These are ancient tightly bound star clusters, often found on the edges of galaxies. For example, our own Milky Way galaxy has over 150 known globular clusters, with some such as NGC 5139 or Omega Centauri being among the most spectacular objects in the sky for both visual observers and astrophotographers alike.

For this new discovery known for now as CDG-2, the team headed up by David Li of the University of Toronto, Canada had worked on identifying very low surface brightness galaxies. The finding of just four globular clusters indicated that they were embedded in a larger galaxy that emitted almost no light. CGD-2 is the first galaxy found just by the observation of its globular clusters alone. The galaxy is estimated to have a total light output of approx. 1 million Sun-like stars with the 4 globular clusters providing about 16% of this. By comparison, the light put out from the Milky Way's globular clusters is about 0.1–0.2% of the entire galaxy.

“This is the first galaxy detected solely through its globular cluster population,” said Dr. Li. “Under conservative assumptions, the four clusters represent the entire globular cluster population of CDG-2.”

The globular clusters found in CDG-2 are not bright enough to be observed in your telescopes however.

Read more here.

Artemis fuelling test is a success

Now aiming for a 6th of March 2026 launch

Great news to wake up to this morning; the full loading and unloading of fuel into the SLS rocket for the Artemis II mission was a success!

The leaks found during the previous testing that had caused the scrubbing of the launch earlier this month seem to have been largely resolved, although NASA admits there is still more work to do.

The launch date for the four crew members to fly to the Moon will be NET (No earlier than) 6th March 2026. This means that it's been 19,426 days since humans last flew to the Moon and just over 13 days until we go again!

Read more here.

Cheers,

Earl White

BINTEL

21st February 2026