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

2024.01.10.
csillagászati hírekenglishsaját asztrofotóim
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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…)

The Sun on 2024-01-05

2024.01.08.
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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

 

Calcium K Sun on 2023-12-31

2024.01.08.
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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…)

Donate Button

2023.12.05.
belső hírekenglish
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A while back, well, in 2017, a friend mentioned rather publicly that I should put a donate button onto my website. So I put one into the sidebar of the main page, and into the photo planner. However, the software (the photo planner for example) and content (astrophotos, webcomic etc) I publish, they all remain as they were: free to use (unless fine print blah-blah).

The Sun on 2023-08-05

2023.08.10.
englishsaját asztrofotóim
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Using the good old 150/750 tube, with a ND3.8 film in front, I obtained the following frames.

Antlia CaK 3nm:

For reference, a Lunt CaK image, colorized and mono

And the infrared cwl 850nm, fwhm 20nm filter showing the active regions

The Sun on 2023-06-01

2023.06.03.
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ASI 178MM (cooled), IR850nm 20nm fwhm, Skywatcher 72/420 ED-APO, ND5, mountpusher, EQ3-mod — I believe this image shows the Calcium Triplet

For comparison, here’s the Baader CaK 5nm image (tovább…)

The Sun on 2023-05-21

2023.05.23.
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EQ3-mod, mountpusher, Lunt LS60T Ha B600, ASI 178MM (cooled)

Hunting the Calcium II triplet

2023.03.25.
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The Sun at around 850 nm infrared*, false color

With my usual setup, the EQ3-mod, mountpusher, Baader Astrosolar ND3.8 Film, TS-Optics 76/342 TS76EDPH, ?filters?, ASI 178MM (cooled), I though what if I got creative. I put in the IRpass 850 filter from ZWO, and added an additional ND1.3 filter, because the ND5 front filter was a bit out of reach. Afterthought: I don’t know the transmittance curve of the ND filter, so maybe what I photographed is actually undefined-ish.

With the above in mind, the transmittance curve of the ZWO IR pass filter, along with the response curve of the camera, gives us a gentle hill around the magic 850 nanometer region, which is where the Calcium II triplet resides, and should draw the active regions in a similar way the CaK does. No matter what filters I used, these active regions show up in all of them, from UV, through CaK, deep blue, even in oxygen III, solar continuum, and 7nm Hα.

Digging out the details did take a good while, since the granulation (I guess it is that) on the surface of the Sun causes a sort of pixel noise to appear that doesn’t fare well with my emphasizing solutions. This „pixelnoise” is also present in my CaK images, and looks exactly the same on the DSO resources I checked at 160 and 170 nanometers.

ND1.3 and telescope glass aside, this is the wavelength-intensity area that should be in the photo. Telluric absorption is not that interesting in this region, and is uniform across the solar disk anyway.

(tovább…)

A Nap aktív régiói, szűrő-tesztek

2023.03.24.
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Testing Baader’s solar filters, in the ersatz-obsi

Az elmúlt időszakban, ilyen-olyan okokból az asztrofotós tevékenységem a napkorongra összpontosult. Rengeteg szűrőt fordítottam a Nap felé, ezek egy része kifejezetten Nap-észleléshez készült, másokat inkább kontár, lássuk milyen lesz alapon. A kalcium K vonala természetesen az egyik kedvencem. Most, hogy a Baader kihozta a jól ismert és méltán szeretett 1.25″-ös kalcium K cella második generációs, felújított változatát, gondoltam, gyorsan ki is próbálom, összehasonlítom a régit az újjal, a sokkal keskenyebb sávú (és szélesebb árú) Lunt modullal, és persze más szűrőkkel.

Az asztrofotós munkásságom hobbi, tudományos cél nélkül, a hangulatért, a csillagászat szépségéért és a fotókért készítem ezeket a képeket, ennek megfelelően mateket vagy fizikát ebbe a cikkbe sem fogok írni.

Dióhéjban 1: alig van különbség, de azért mégis.

Dióhéjban 2: teljes napkoronghoz akinek megvan a régi kalcium szűrő, az megtarthatja, vitatható, hogy jobb-e az új filter képe, akkor is, ha a régi filterem több éves. Ennyire jók ezek a filterek, régin is, újonnan is. A borsos árat is figyelembe véve, ezek a kicsi kalcium szűrők nem vehetik fel a versenyt a Lunt sokkal keskenyebb sávú moduljával.

Dióhéjban 2: a Baader Venus U szűrőnek is adjunk egy esélyt, sőt a mélykék szűrőnek is. Van ott még Fraunhofer-vonal, ami szépen mutatkozik kékben is, solar continuum-ban is, sőt még a mélyégre szánt hidrogén alfa filter is mutatja pontosan ezeket az aktív zónákat.

Dióhéjban 3: a Vénusz légköréhez érdekes lehet ez az új kalcium szűrő, hiszen az expozíciós időt megfelezi: hiába névleg keskenyebb a szűrő, egyszerűen több fényt enged be, ami a Vénuszhoz mindenképp kívánatos. Itt alul még a régi kalcium K szűrős kép a Vénuszról, a nagy 2020-as szezonból.

Vénusz 2020-04-05,  Baader CaK (gen1) mint cián és zöld mint narancs, bikolor, hamis színes fotó N150/750 tububussal.

(tovább…)

The Sun’s active regions, in Calcium K and other wavelengths, filters’ comparison

2023.03.20.
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Testing Baader’s solar filters, in the ersatz-obsi

As you know, due to various reasons, lately I’ve been doing solar imaging almost exclusively, focusing on full disk observations. Of the many filters I have turned towards the Sun — some dedicated solar filters, some more in a hacker spirit –, the Calcium K wavelength is one of my favorites, obviously. Now that Baader started selling its generation ii CaK filter, I figured I’d test it against itself, the first generation, and against Lunt’s Calcium module.

UPDATE 2024: in the meanwhile I tested Altair Astro’s early bird sample of Calcium K 3nm, against Antlia’s 3nm CaK, and got a B1800 Lunt CaK (btw fuck Bresser for wasting my time, for the second time in a row regarding Lunt products), to deploy in a long, f/11 tube and protected by a full aperture ERF (from Altair), to do full disk solar with chromosphere and all.

As you also know, I record images as a hobby, without any specific scientific goal, I just like the rigor and if some aesthetics can arise from it, in the form of nice solar disk images in this case.

TLDR0: not much difference, but still.

TLDR1: if doing full disk, if you have the old CaK and like it — keep it and your setup the way it is, the new filter is nice, the profile is standard, but overall, doesn’t show anything new nor better than the old one. Both are that good. Obviously not as good as Lunt’s CaK, but they are a fair competition, given the price range.

TLDR2: if you have the Venus U filter, do use it. It’s not as good for the Sun’s active regions as the CaK, but still pretty good. Also, give the dark blue a chance. Or basically any filter you own.

TLDR3: for Venus, the new filter may yield better images, due to it letting through about two times more light (half the expo time). I like very much the CaK images I obtained of Venus, in the 2020 epic season.

Venus, on 2020-04-05, using Baader’s CaK (gen1), as a false bi-color image with a green filter, mapped to cyan and orange respectively, with a N150/750 tube.

(tovább…)

Jól kalibrált monitoron mindegyik számnál elkülönülő árnyalat látszik. Ha mégsem látszanak, akkor a megjelenített képek színhiányosan rajzolódnak ki. A monitort valószínűleg kalibrálni kell.

You should see distinct shades for each number. If those shades are not clearly visible, the displayed pictures will lack accuracy. Your display most likely needs to be calibrated (brightness, gamma, contrast etc.).