Lunt CaK filter transmission curve
- Merlin66
- Librarian
- Posts: 3972
- Joined: Tue Dec 13, 2011 1:23 pm
- Location: Junortoun, Australia
- Has thanked: 174 times
- Been thanked: 619 times
- Contact:
Lunt CaK filter transmission curve
Does anyone have a transmission curve for the Lunt CaK filter?
Interested in the possible UV and NIR leakage.
Interested in the possible UV and NIR leakage.
"Astronomical Spectroscopy - The Final Frontier" - to boldly go where few amateurs have gone before
https://groups.io/g/astronomicalspectroscopy
http://astronomicalspectroscopy.com
"Astronomical Spectroscopy for Amateurs" and
"Imaging Sunlight - using a digital spectroheliograph" - Springer
https://groups.io/g/astronomicalspectroscopy
http://astronomicalspectroscopy.com
"Astronomical Spectroscopy for Amateurs" and
"Imaging Sunlight - using a digital spectroheliograph" - Springer
- Bob Yoesle
- Almost There...
- Posts: 996
- Joined: Thu Mar 08, 2012 7:24 pm
- Has thanked: 541 times
- Been thanked: 811 times
Re: Lunt CaK filter transmission curve
Hi Ken,
I believe the Lunt CaK modules use a CaK bandpass filter sourced from Barr Associates. Note "some" of these are specified to have OD 4 blocking from "UV to far IR." Christian has published a filter curve for his Barr CaK filter here. There is another curve he recently posted here.
Here's the Lunt CaK filter curves form their product borchure:
Don't know about any specifics of the other filters employed in the Lunt CaK modules, but from the above and due to the lineage from early Coronado CaK filter systems to Lunt, it seems they may incorporate a a number of additional "conditioning" filters and a sub-diameter 20 nm + wide transmission filter as an ERF. Since Lunt does indicate they are safe for visual use, I would imagine they are otherwise blocked to OD5, but that's only an assumption on my part.
Here's the filter curves of one of my CaK PST filters I obtained from Mark Wagner when he checked it out at his facility a few months back:
Bob
I believe the Lunt CaK modules use a CaK bandpass filter sourced from Barr Associates. Note "some" of these are specified to have OD 4 blocking from "UV to far IR." Christian has published a filter curve for his Barr CaK filter here. There is another curve he recently posted here.
Here's the Lunt CaK filter curves form their product borchure:
Don't know about any specifics of the other filters employed in the Lunt CaK modules, but from the above and due to the lineage from early Coronado CaK filter systems to Lunt, it seems they may incorporate a a number of additional "conditioning" filters and a sub-diameter 20 nm + wide transmission filter as an ERF. Since Lunt does indicate they are safe for visual use, I would imagine they are otherwise blocked to OD5, but that's only an assumption on my part.
Here's the filter curves of one of my CaK PST filters I obtained from Mark Wagner when he checked it out at his facility a few months back:
Bob
Diagonally parked in a parallel universe.
Curiosity is the father of knowledge; uncertainty is the mother of wisdom.
Dark-Sky Defenders
Goldendale Observatory
Curiosity is the father of knowledge; uncertainty is the mother of wisdom.
Dark-Sky Defenders
Goldendale Observatory
- Merlin66
- Librarian
- Posts: 3972
- Joined: Tue Dec 13, 2011 1:23 pm
- Location: Junortoun, Australia
- Has thanked: 174 times
- Been thanked: 619 times
- Contact:
Re: Lunt CaK filter transmission curve
Bob,
Yes, I've seen those curves before.
But I haven't seen any 380 to 2500 nm transmission curves to confirm all the marketing hype.
I would have thought by now someone would have put a spectrograph on the Lunt CaK filter.......
Yes, I've seen those curves before.
But I haven't seen any 380 to 2500 nm transmission curves to confirm all the marketing hype.
I would have thought by now someone would have put a spectrograph on the Lunt CaK filter.......
"Astronomical Spectroscopy - The Final Frontier" - to boldly go where few amateurs have gone before
https://groups.io/g/astronomicalspectroscopy
http://astronomicalspectroscopy.com
"Astronomical Spectroscopy for Amateurs" and
"Imaging Sunlight - using a digital spectroheliograph" - Springer
https://groups.io/g/astronomicalspectroscopy
http://astronomicalspectroscopy.com
"Astronomical Spectroscopy for Amateurs" and
"Imaging Sunlight - using a digital spectroheliograph" - Springer
-
- Way More Fun to Share It!!
- Posts: 2161
- Joined: Sun Jun 14, 2015 4:46 pm
- Location: France
- Has thanked: 1 time
- Been thanked: 2725 times
- Contact:
Re: Lunt CaK filter transmission curve
Hello Ken,
I think someone on SolarChat shared the transmission curves of the Lunt Ca K etalon. It was a long time ago (3 or 4 years ?).
I don't know whether there is an easy way to make a search on the Forum ?
I think someone on SolarChat shared the transmission curves of the Lunt Ca K etalon. It was a long time ago (3 or 4 years ?).
I don't know whether there is an easy way to make a search on the Forum ?
Christian Viladrich
Co-author of "Planetary Astronomy"
http://planetary-astronomy.com/
Editor of "Solar Astronomy"
http://www.astronomiesolaire.com/
Co-author of "Planetary Astronomy"
http://planetary-astronomy.com/
Editor of "Solar Astronomy"
http://www.astronomiesolaire.com/
- Bob Yoesle
- Almost There...
- Posts: 996
- Joined: Thu Mar 08, 2012 7:24 pm
- Has thanked: 541 times
- Been thanked: 811 times
Re: Lunt CaK filter transmission curve
I couldn't find it using Google search, but I did find it on my hard drive:
I don't believe this is an etalon, rather it's a typical of a yellow dichroic filter - perhaps hard coated. UV blocking does look good, but anything over 440 nm needs additional blocking.
I don't believe this is an etalon, rather it's a typical of a yellow dichroic filter - perhaps hard coated. UV blocking does look good, but anything over 440 nm needs additional blocking.
Diagonally parked in a parallel universe.
Curiosity is the father of knowledge; uncertainty is the mother of wisdom.
Dark-Sky Defenders
Goldendale Observatory
Curiosity is the father of knowledge; uncertainty is the mother of wisdom.
Dark-Sky Defenders
Goldendale Observatory
- Merlin66
- Librarian
- Posts: 3972
- Joined: Tue Dec 13, 2011 1:23 pm
- Location: Junortoun, Australia
- Has thanked: 174 times
- Been thanked: 619 times
- Contact:
Re: Lunt CaK filter transmission curve
Bob,
Thanks for that.
I can understand why they added all the other blocking filters!!
Thanks for that.
I can understand why they added all the other blocking filters!!
"Astronomical Spectroscopy - The Final Frontier" - to boldly go where few amateurs have gone before
https://groups.io/g/astronomicalspectroscopy
http://astronomicalspectroscopy.com
"Astronomical Spectroscopy for Amateurs" and
"Imaging Sunlight - using a digital spectroheliograph" - Springer
https://groups.io/g/astronomicalspectroscopy
http://astronomicalspectroscopy.com
"Astronomical Spectroscopy for Amateurs" and
"Imaging Sunlight - using a digital spectroheliograph" - Springer
-
- Way More Fun to Share It!!
- Posts: 2161
- Joined: Sun Jun 14, 2015 4:46 pm
- Location: France
- Has thanked: 1 time
- Been thanked: 2725 times
- Contact:
Re: Lunt CaK filter transmission curve
Hi Bob,
I have this same one and others too on my HD. But for some reasons, I can't find the curve of the etalon.
I have this same one and others too on my HD. But for some reasons, I can't find the curve of the etalon.
Christian Viladrich
Co-author of "Planetary Astronomy"
http://planetary-astronomy.com/
Editor of "Solar Astronomy"
http://www.astronomiesolaire.com/
Co-author of "Planetary Astronomy"
http://planetary-astronomy.com/
Editor of "Solar Astronomy"
http://www.astronomiesolaire.com/
- Merlin66
- Librarian
- Posts: 3972
- Joined: Tue Dec 13, 2011 1:23 pm
- Location: Junortoun, Australia
- Has thanked: 174 times
- Been thanked: 619 times
- Contact:
Re: Lunt CaK filter transmission curve
Christian,
I don't believe there is an etalon involved in the Lunt CaK filter design.
Just a series of filter elements, as per the Lunt diagram and Bob's earlier comment.
I don't believe there is an etalon involved in the Lunt CaK filter design.
Just a series of filter elements, as per the Lunt diagram and Bob's earlier comment.
"Astronomical Spectroscopy - The Final Frontier" - to boldly go where few amateurs have gone before
https://groups.io/g/astronomicalspectroscopy
http://astronomicalspectroscopy.com
"Astronomical Spectroscopy for Amateurs" and
"Imaging Sunlight - using a digital spectroheliograph" - Springer
https://groups.io/g/astronomicalspectroscopy
http://astronomicalspectroscopy.com
"Astronomical Spectroscopy for Amateurs" and
"Imaging Sunlight - using a digital spectroheliograph" - Springer
-
- Way More Fun to Share It!!
- Posts: 2161
- Joined: Sun Jun 14, 2015 4:46 pm
- Location: France
- Has thanked: 1 time
- Been thanked: 2725 times
- Contact:
Re: Lunt CaK filter transmission curve
You are completely right Ken, this is not a Fabry-Perot but a dielectric filter.
Finally, I've found the original SolarChat post :
viewtopic.php?t=12203
Unfortunatly, there is no high resolution plot for the narrow band filter.
Finally, I've found the original SolarChat post :
viewtopic.php?t=12203
Unfortunatly, there is no high resolution plot for the narrow band filter.
Christian Viladrich
Co-author of "Planetary Astronomy"
http://planetary-astronomy.com/
Editor of "Solar Astronomy"
http://www.astronomiesolaire.com/
Co-author of "Planetary Astronomy"
http://planetary-astronomy.com/
Editor of "Solar Astronomy"
http://www.astronomiesolaire.com/
- Bob Yoesle
- Almost There...
- Posts: 996
- Joined: Thu Mar 08, 2012 7:24 pm
- Has thanked: 541 times
- Been thanked: 811 times
Re: Lunt CaK filter transmission curve
Thanks Christian - a good re-read of that thread :-)
Diagonally parked in a parallel universe.
Curiosity is the father of knowledge; uncertainty is the mother of wisdom.
Dark-Sky Defenders
Goldendale Observatory
Curiosity is the father of knowledge; uncertainty is the mother of wisdom.
Dark-Sky Defenders
Goldendale Observatory