The Spectral Composer

I’ve been photographing the Sun for more than two years now almost each and every day, in a bit of a hackish way: using all kinds of filters beyond the 540nm continuum – hydrogen alpha – near UV calcium triad. However, as I advanced, I discovered that this knowledge is simply not common in the community, and not just that, it’s also a bit hard to come by while googling around. Also, to better explain double stacking, off banding and similar stuff, articles like this one Altair Astro’s 3nm CaK Ultra filter: testing, comparison, review are maybe rare.

So I put together an interactive tool to play around with spectra, in a way amateur astronomers find it interesting. The Spectral Composer.

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Altair Astro’s 3nm CaK Ultra filter: testing, comparison, review

Solar disk in Altair Astro’s 3nm CaK Ultra filter, enhanced contrast

I got a new filter to pudding-test: Altair Astro’s 3nm Calcium K Ultra, stated to have 3nm FWHM and a very high transmission. Let’s see how it performs.

Before we jump in, let me also present some information I compiled along the way, and some theory and links fellow amateur astronomers may find useful.

Important note: this article is not sponsored by the vendor, and the vendor has not influenced the conclusions presented below in any way.

Contents

  • market overview: what’s available to amateurs, around the Calcium K line
  • theory and practice: about the filters, the Sun and its spectrum
  • first impressions, unboxing
  • the tests themselves
  • further (reference) images
  • conclusions

(tovább…)

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The Sun on 2024-01-05

With a front ERF, Altair Astro’s Triband, 115mm, Tecnosky 102/1100 refractor, Lunt’s CaK B1800 and the ASI 533MM camera, I obtained the following:

CaK, 2.4Å

CaK 2.4Å, colorized

 

With a Tecnosky 102/1100 refractor, Herschel prism, ND 0.96, a filterwheel and the ASI 533MM camera, I obtained the following:

Antlia 3nm hydrogen alpha. The disk is clearly continuum, but the prominences were obvious even on the live view

Altair Astro’s G-band filter, 2nm fwhm at around 430nm cwl

 

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Calcium K Sun on 2023-12-31

Using a fairly new setup, as they were in the light train: Altair Astro Triband D-ERF 115mm, Tecnosky 102/1100 ED refractor, Lunt CaK B1800, ASI 533MM, along with my EQ3 with the home built controller, I captured the following frames.

full disk, linear light

full disk, linear light

full disk, paraboloid gamma curve

full disk, paraboloid gamma curve

detail from the full disk

detail from the full disk

same, colorized

same, colorized

(tovább…)

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