Measurement of some solar filters

[christian viladrich]

Hi,

Here the transmission profile of various solar filters measured with an Ocean Optics HR 4000 spectrometer. The dispersion is 0.27 nm/pixel. Measured spectral resolution near Ca K is better than 1 nm.

Some profiles are measured at a much higher spectral resolution with Sol'Ex.

1) The Antlia 393-3 nm was measured at 3.7 nm (instead of 3.0 nm). Max transmission = 72%:

http://astrosurf.com/viladrich/astro/in ... ug2023.jpg

The FWHM was confirmed at 3.6 nm with the larger spectral resolution of Sol'Ex (oscillations near the peak of transmission are artefacts) :

http://astrosurf.com/viladrich/astro/in ... ec2022.jpg

2) I measured two different Altair G-band 2 nm :

The first one was measured to 2.9 nm, transmission max = 85%:

http://astrosurf.com/viladrich/astro/in ... 023-CV.jpg

The FWHM was confirmed at 3.0 nm with Solex at a higher resolution :

http://astrosurf.com/viladrich/astro/in ... ay2023.jpg

The second Altair G-band 2 nm was measured to 2.9 nm :
http://astrosurf.com/viladrich/astro/in ... 23-ALH.jpg

3) The Edmund Optics 430-10 nm is slighly better than the specifications (FWHM = 8.7 nm) :
http://astrosurf.com/viladrich/astro/in ... HR4000.jpg

Confirmed at a higher spectral resolution with Solex (FWHM = 8.4 nm) :
http://astrosurf.com/viladrich/astro/in ... il2023.jpg

4) The Andover 430-2 nm is right to the spec (FWHM = 2.0 nm) :
http://astrosurf.com/viladrich/astro/in ... -1.9nm.jpg
http://astrosurf.com/viladrich/astro/in ... il2023.jpg

5) The Optolong IR-cut based on KG3. Transmission at Ha is about 65% :
http://astrosurf.com/viladrich/astro/in ... ug2023.jpg

6) Baader D-ERF :
http://astrosurf.com/viladrich/astro/in ... 00-ALH.jpg

More here :
http://astrosurf.com/viladrich/astro/in ... lters.html

[Dennis]

This is very useful, thanks for this.

[thesmiths]

Thanks for that. With regards to the Optolong IR-cut: it's surprising how much it reduces H-alpha. I have a GSO IR-cut filter that also reduces H-alpha by a similar amount but does very well at Calcium-K/H. I would be interested to see the Astronomik L1 UV/IR cut filter measured independently. It is the one I (and others) recommend to use with an SHG.

[christian viladrich]

I have a measurement of a very old L astrononik :

http://astrosurf.com/viladrich/astro/in ... k-L-CV.JPG

The L1 is probably different.

[christian viladrich]

Here is the SV Bony IR-cut :

http://astrosurf.com/viladrich/astro/in ... 00-ALH.jpg

[christian viladrich]

Thanks for that. With regards to the Optolong IR-cut: it's surprising how much it reduces H-alpha. I have a GSO IR-cut filter that also reduces H-alpha by a similar amount but does very well at Calcium-K/H. I would be interested to see the Astronomik L1 UV/IR cut filter measured independently. It is the one I (and others) recommend to use with an SHG.

The transmission of the KG3 is about 70% at 650 nm :

https://www.schott.com/shop/medias/SCHO ... GQ0ZDE1NGY

[thesmiths]

Is KG3 a very common glass to use for so-called IR-cut filters? A lot of companies don't give the spectral data (Astronomik and Baader do, but many do not). I did find my GSO IR-cut filter was a nice one for Ca-K/H as an ERF for SHG, and now that I see the Schott chart, I understand why. But it reduced the light too much near H-alpha (for that I used a Baader 35nm H-alpha as an ERF -- unfortunately now discontinued for some reason).

[marktownley]

Great thread! Thanks Christian!

I will leave for a couple of days here to get attention then move to the solar reference library.

[Nicksolar]

Hi there, I dug out the official spectrographic test for the first Altair G-Band filter, serial number 0031-0423. I can't post images here so I posted it on BYA solar section here: https://www.backyardastro.org/topic/494 ... ctrograph/

If you let me know the serial number of the other filter I'll post that as well. Onward weekend!

Best, Nick

[Nicksolar]

I've added an 0.1nm spectrograph test of filter serial number 001-0423 here too - thanks Christian

[marktownley]

I've added an 0.1nm spectrograph test of filter serial number 001-0423 here too - thanks Christian

Thanks Nick!

Do you have an extended response of the filter? I'm wondering where the extremes of blocking are?

Mark

[christian viladrich]

Great thread! Thanks Christian!

I will leave for a couple of days here to get attention then move to the solar reference library.

Hi Mark,

Please wait until the end of the week. I'll post some more measurements.

[christian viladrich]

I've added an 0.1nm spectrograph test of filter serial number 001-0423 here too - thanks Christian

Thanks for the curves Nick ! I'll have a look at them.

[Nicksolar]

Thanks Nick!

Do you have an extended response of the filter? I'm wondering where the extremes of blocking are?

Mark

Hi Mark, here's a full Spectrum test report from 200nm to 30000nm for the current Quartz Altair 2nm G-Band Filter
Because the filter is made from Quartz, the transmission in the G-Band region is excellent for such a narrow FWHM in order to keep the exposure as fast as possible to freeze the seeing, but of course it doesn't block beyond about 1150nm. Therefore we are very clear on both the product packaging, and marketing material, that this filter must be used with professional solar filters such as Baader film or a Herschel Wedge which attenuate all wavelengths, and that it is not for visual use, only for imaging.

[christian viladrich]

Thanks for the extended transmission curve Nick !

[marktownley]

Yes. thanks Nick. Appreciate this.