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Author Topic: The definative ERF risk assesment  (Read 8418 times)

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Offline Merlin66

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The definative ERF risk assesment
« on: 17:21:17, 02 June, 2008 »
http://www.icnirp.net/documents/broadband.pdf
The above document has everything needed to assess the safety of our ERF, and other solar filters. Although this is a 1997 document, there are some updates (on the WHO pages) but these don't affect the basic recommendations.
Unfortunately there is a bit of maths involved to apply the formulae to our application, but over the next few days I'll try and make sense of it and offer up some "Reader Digest" summaries.
If any of the forum members can read this and contribute; the more the merrier!
Note that most optical systems and the earth's atmosphere already block UV below 300nm, so we only have to consider UV-A, likewise anything above 1200nm is so low in energy, for the purposes of risk assessment can be ignored.
C11, C9.25 SCT, 4" Genesis, NEQ6pro, modded 1000D,  ATik314L+, DMK41AF04, SM60DS/BF15, and Spectroscopes (many!).
http://tech.groups.yahoo.com/group/astronomical_spectroscopy/
"Astronomical Spectroscopy for Amateurs", "Grating Spectroscopes-How to Use them" -Springer

Offline michaeloconnell78

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Re: Definately a STICKY - The definative ERF risk assesment
« Reply #1 on: 18:03:06, 02 June, 2008 »
nice one Ken. have some K.
Regards,
Michael
www.astroshot.com
Gemini G41 Observatory+ Mount; 16" LX200 SCT, TEC140; Pentax75SDHF; PST CaK, PST Ha.

Offline swashy

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Re: Definately a STICKY - The definative ERF risk assesment
« Reply #2 on: 18:17:02, 02 June, 2008 »
Ive stuck it for you Ken, looks useful, to those that may understand it  ;D
Ade

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Offline colinsk

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Re: The definative ERF risk assesment
« Reply #3 on: 16:31:18, 03 June, 2008 »
Thank you Ken, this is helpful. After reading it I am curious as to your thoughts about the specific dangers of monochromatic light. Normally we have an adversion to bright lights that will protect us but am I correct in my understanding that for monochromatic sources this might not be as accurate? It is hard as we are dealing with a non-coherent monochromatic source and everything in there for monochromatic light seems to be for lasers.

I am sure in order to get the h-alpha signal that bright we would need a 1 M objective or something but I am curious.

Offline Merlin66

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Re: The definative ERF risk assesment
« Reply #4 on: 16:50:23, 03 June, 2008 »
Colin,
Bear with me. I'm in the process of preparing a "Dummies Guide" and still struggling a bit not only with the maths, but getting consistant hard data to use in the calculations. The subject of narrow band filters/ very narrow band (!!!) will come out, I'm sure.
Should be something "for discussion" by the end of the week.
C11, C9.25 SCT, 4" Genesis, NEQ6pro, modded 1000D,  ATik314L+, DMK41AF04, SM60DS/BF15, and Spectroscopes (many!).
http://tech.groups.yahoo.com/group/astronomical_spectroscopy/
"Astronomical Spectroscopy for Amateurs", "Grating Spectroscopes-How to Use them" -Springer

Offline colinsk

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Re: The definative ERF risk assesment
« Reply #5 on: 03:47:13, 04 June, 2008 »
thank you! I'll also look for some solar safety references I have.

Offline Merlin66

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Re: The definative ERF risk assesment
« Reply #6 on: 10:31:11, 11 June, 2008 »
I've finished the write-up on the ICNIRP guidelines and included some other pertinant stuff from the WHO ( World Health Organisation) as well as other sources. Just checking my maths and content, should be up soon.
C11, C9.25 SCT, 4" Genesis, NEQ6pro, modded 1000D,  ATik314L+, DMK41AF04, SM60DS/BF15, and Spectroscopes (many!).
http://tech.groups.yahoo.com/group/astronomical_spectroscopy/
"Astronomical Spectroscopy for Amateurs", "Grating Spectroscopes-How to Use them" -Springer

Offline Merlin66

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Re: The definative ERF risk assesment
« Reply #7 on: 15:50:28, 13 June, 2008 »
Here's my review of the ICNIRP Guidelines with some other data thrown in.
Had to break it into two sections for upload.
Many thanks to ColinK for his comments on the final draft.

[attachment deleted by admin]
C11, C9.25 SCT, 4" Genesis, NEQ6pro, modded 1000D,  ATik314L+, DMK41AF04, SM60DS/BF15, and Spectroscopes (many!).
http://tech.groups.yahoo.com/group/astronomical_spectroscopy/
"Astronomical Spectroscopy for Amateurs", "Grating Spectroscopes-How to Use them" -Springer

Offline Merlin66

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Re: The definative ERF risk assesment
« Reply #8 on: 15:52:17, 13 June, 2008 »
And here's part 2.
Any questions/ comments I'll try to answer, but as I say it's my assessment of the guidelines; you may disagree.

[attachment deleted by admin]
C11, C9.25 SCT, 4" Genesis, NEQ6pro, modded 1000D,  ATik314L+, DMK41AF04, SM60DS/BF15, and Spectroscopes (many!).
http://tech.groups.yahoo.com/group/astronomical_spectroscopy/
"Astronomical Spectroscopy for Amateurs", "Grating Spectroscopes-How to Use them" -Springer

Offline colinsk

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Re: The definative ERF risk assesment
« Reply #9 on: 22:28:14, 15 June, 2008 »
Nice work Ken! That saved much time. When I do the study of my 90mm PST I'll post my methodology.

Have some K!

Offline michaeloconnell78

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Re: The definative ERF risk assesment
« Reply #10 on: 23:13:02, 15 June, 2008 »
Nice one Ken.
From reading that, I can't help but think the Baader C-ERF is the best and probably only ERF to use.
Regards,
Michael
www.astroshot.com
Gemini G41 Observatory+ Mount; 16" LX200 SCT, TEC140; Pentax75SDHF; PST CaK, PST Ha.

Offline colinsk

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Re: The definitive ERF risk assessment
« Reply #11 on: 02:49:08, 14 July, 2008 »
In communicating with Mark Wagner at Solar Spectrum I have learned that to block the IR between 1500nm and 4000nm you need a ITF filter.

While this range of frequencies is not transmitted to the retina it does tend to heat the lens and long term exposure has been shown to cause glassblowers cataracts. The problem seems to be that while it is rare that cells are damaged by the thermal loading from far IR there is no way for the eye to replace cells in the lens so damage is cumulitive.

The new PST has one at the EP side, the old PST has it on the objective. DayStar and Solar Spectrum contain one in the etalon stack. Coronado, Lunt and Solar Scope contain one in the blocking filter. I don't have any confirmation but with Thousand Oaks background in depositing metal on filters I assume they are using one as well.

An ITF filter is usually made from depositing a layer of silver then a dielectric layer and another layer of silver in precise thicknesses.

I mention it as a warning for those people who are trying to modify an older PST and use the stock blocking filter. I strongly recommend that if you have an older PST (one without the clear blue objective) you purchase a BF5 or larger Coronado blocking filter which contains an ITF.

As I learn more I will post it to this thread.

Offline michaeloconnell78

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Re: The definative ERF risk assesment
« Reply #12 on: 18:41:18, 14 July, 2008 »
That's very interesting Colin.
Thanks for the info.
Regards,
Michael
www.astroshot.com
Gemini G41 Observatory+ Mount; 16" LX200 SCT, TEC140; Pentax75SDHF; PST CaK, PST Ha.

Offline colinsk

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Re: The definative ERF risk assesment
« Reply #13 on: 02:38:30, 30 March, 2009 »
Here is a great link for those thinking about safety:

http://www.opticsplanet.net/coronado-safety-guide.html


Offline colinsk

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Re: The definative ERF risk assesment
« Reply #14 on: 04:54:30, 04 August, 2011 »
I really wish Ken's papers were still here. Would help if they were hosted on another site and linked?

 

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