A bit of filter addendum


jimcoble2000
 

Due to the recent thread on filters I thought it was time to check my filters against the spectroscope again. It has been some years since Ted, Kent, and I did this testing. Filters may have changed a bit but the real variable now is lighting technology. Gone are the days of the old sodium lamps and mercury lamps. New LED bulbs have changed the landscape of the night in urban areas.

While I need to do more work and would like to acquire a couple of Gen 3 filters. My initial look tonight left me with a couple of impressions. This was a bit informal. It is easy to find a continuous spectrum bulb. Many porch lights still use this technology (though I'll bet fewer and fewer). I also compared the filters against gas discharge bulbs. Lacking in my experiment is a confirmed source of LED Light. I also need to acquire a lumicon UHC to run the test on. I will have to work on that.

Initial findings:
OIII still cuts most of the visible spectrum out except for green and blue sections. That has not changed.

My Baader UHC cuts very little out of the spectrum. Just a bit in the yellow sodium range. I did say it cuts the least light. Not much has changed there.

Ultrablock. A fair bit more is eliminated than the Baader UHC. That was expected.

Broadband Moon and sky glow filter. This is where the rubber meets the road in change. With the new lighting, I cannot detect any blocking at all, it all comes through. I suspect broadband filters are now totally obsolete in urban and suburban settings. They may do a small bit in more rural settings in low intensity skyglow but frankly I think they are now a waste of money. They have not kept up. Originally they were designed for sodium light but that is largely gone now. My experience has been that they were only of very limited effect in fairly dark skies years ago but even there and then it was marginal, if not imaginary.

Comet filter. Only allows a couple of narrow bands in the green. Often referred to as cyanogen filters, that is incorrect as the advertised specs for the filter do not affect the wavelengths of cyanogen. I don't know where that myth started.

Things to do still.

Locate a confirmed LED source and run the tests. If possible find an old sodium and mercury light. Acquire a gen 3 to run the test. Borrow an old Lumicom UHC.


galacticprobe
 

Starting off this post by quoting the opening of the one below: "Due to the recent thread on filters..." After reading everything people with far more knowledge on filters than I have are saying about them, especially the terminology, I was wondering if there was a decent publication available for a dunce like me - who lately has experienced difficulty just getting his eye to find its way to the eyepiece without losing his balance and landing on the ground - that has put all of this magnificent info into a sort of 'Idiot's Guide to Telescope Eyepiece Filters', or some such book.

Other than the term "broadband", which I know all too well from my days as an electronics tech and how it applies to radio frequencies (same principle, I'm guessing, applies to light frequencies), I'm having trouble keeping up with everything that's being put forth.

I've got no eyepiece filters at the moment, not even a Moon filter (so ol' Luna gets a bit blinding once she crosses the First Quarter stage). So back to my original question: Is there a 'Telescope Eyepiece Filters For Dummies' out there? (There's at least one dummy at this keyboard now looking for something like that.)

"Keep looking up!"
Dino.


-----Original Message-----
From: jimcoble2000 via groups.io <jimcoble2000@...>
To: BBAA-Group <backbayastro@groups.io>
Sent: Sat, Jul 2, 2022 10:00 pm
Subject: [BackBayAstro] A bit of filter addendum

Due to the recent thread on filters I thought it was time to check my filters against the spectroscope again. It has been some years since Ted, Kent, and I did this testing. Filters may have changed a bit but the real variable now is lighting technology. Gone are the days of the old sodium lamps and mercury lamps. New LED bulbs have changed the landscape of the night in urban areas.

While I need to do more work and would like to acquire a couple of Gen 3 filters. My initial look tonight left me with a couple of impressions. This was a bit informal. It is easy to find a continuous spectrum bulb. Many porch lights still use this technology (though I'll bet fewer and fewer). I also compared the filters against gas discharge bulbs. Lacking in my experiment is a confirmed source of LED Light. I also need to acquire a lumicon UHC to run the test on. I will have to work on that.

Initial findings:
OIII still cuts most of the visible spectrum out except for green and blue sections. That has not changed.

My Baader UHC cuts very little out of the spectrum. Just a bit in the yellow sodium range. I did say it cuts the least light. Not much has changed there.

Ultrablock. A fair bit more is eliminated than the Baader UHC. That was expected.

Broadband Moon and sky glow filter. This is where the rubber meets the road in change. With the new lighting, I cannot detect any blocking at all, it all comes through. I suspect broadband filters are now totally obsolete in urban and suburban settings. They may do a small bit in more rural settings in low intensity skyglow but frankly I think they are now a waste of money. They have not kept up. Originally they were designed for sodium light but that is largely gone now. My experience has been that they were only of very limited effect in fairly dark skies years ago but even there and then it was marginal, if not imaginary.

Comet filter. Only allows a couple of narrow bands in the green. Often referred to as cyanogen filters, that is incorrect as the advertised specs for the filter do not affect the wavelengths of cyanogen. I don't know where that myth started.

Things to do still.

Locate a confirmed LED source and run the tests. If possible find an old sodium and mercury light. Acquire a gen 3 to run the test. Borrow an old Lumicom UHC.


jimcoble2000
 

I have not read any of the general books on the astronomy hobby in years but if memory serves correct there was one book that seemed well written. "The Backyard Astronomer" by Dickenson and Dyer. Doubtless there are others but this is the one that comes to mind. https://www.amazon.com/Backyard-Astronomers-Guide-Terence-Dickinson/dp/155209507X/ref=asc_df_155209507X?tag=bingshoppinga-20&linkCode=df0&hvadid=80058242197447&hvnetw=o&hvqmt=e&hvbmt=be&hvdev=c&hvlocint=&hvlocphy=&hvtargid=pla-4583657821898853&psc=1

On Sunday, July 3, 2022 at 12:48:10 AM EDT, galacticprobe via groups.io <lambulambu@...> wrote:


Starting off this post by quoting the opening of the one below: "Due to the recent thread on filters..." After reading everything people with far more knowledge on filters than I have are saying about them, especially the terminology, I was wondering if there was a decent publication available for a dunce like me - who lately has experienced difficulty just getting his eye to find its way to the eyepiece without losing his balance and landing on the ground - that has put all of this magnificent info into a sort of 'Idiot's Guide to Telescope Eyepiece Filters', or some such book.

Other than the term "broadband", which I know all too well from my days as an electronics tech and how it applies to radio frequencies (same principle, I'm guessing, applies to light frequencies), I'm having trouble keeping up with everything that's being put forth.

I've got no eyepiece filters at the moment, not even a Moon filter (so ol' Luna gets a bit blinding once she crosses the First Quarter stage). So back to my original question: Is there a 'Telescope Eyepiece Filters For Dummies' out there? (There's at least one dummy at this keyboard now looking for something like that.)

"Keep looking up!"
Dino.


-----Original Message-----
From: jimcoble2000 via groups.io <jimcoble2000@...>
To: BBAA-Group <backbayastro@groups.io>
Sent: Sat, Jul 2, 2022 10:00 pm
Subject: [BackBayAstro] A bit of filter addendum

Due to the recent thread on filters I thought it was time to check my filters against the spectroscope again. It has been some years since Ted, Kent, and I did this testing. Filters may have changed a bit but the real variable now is lighting technology. Gone are the days of the old sodium lamps and mercury lamps. New LED bulbs have changed the landscape of the night in urban areas.

While I need to do more work and would like to acquire a couple of Gen 3 filters. My initial look tonight left me with a couple of impressions. This was a bit informal. It is easy to find a continuous spectrum bulb. Many porch lights still use this technology (though I'll bet fewer and fewer). I also compared the filters against gas discharge bulbs. Lacking in my experiment is a confirmed source of LED Light. I also need to acquire a lumicon UHC to run the test on. I will have to work on that.

Initial findings:
OIII still cuts most of the visible spectrum out except for green and blue sections. That has not changed.

My Baader UHC cuts very little out of the spectrum. Just a bit in the yellow sodium range. I did say it cuts the least light. Not much has changed there.

Ultrablock. A fair bit more is eliminated than the Baader UHC. That was expected.

Broadband Moon and sky glow filter. This is where the rubber meets the road in change. With the new lighting, I cannot detect any blocking at all, it all comes through. I suspect broadband filters are now totally obsolete in urban and suburban settings. They may do a small bit in more rural settings in low intensity skyglow but frankly I think they are now a waste of money. They have not kept up. Originally they were designed for sodium light but that is largely gone now. My experience has been that they were only of very limited effect in fairly dark skies years ago but even there and then it was marginal, if not imaginary.

Comet filter. Only allows a couple of narrow bands in the green. Often referred to as cyanogen filters, that is incorrect as the advertised specs for the filter do not affect the wavelengths of cyanogen. I don't know where that myth started.

Things to do still.

Locate a confirmed LED source and run the tests. If possible find an old sodium and mercury light. Acquire a gen 3 to run the test. Borrow an old Lumicom UHC.


Troy Riedel
 

Dino,

Plenty of good resources online ... anything by David Knisely will be good. He's active on CloudyNights.com & he's had reviews published in ASTRONOMY Mag (maybe S&T, too?).

Here's an excellent primer:
https://www.prairieastronomyclub.org/useful-filters-for-viewing-deep-sky-objects/

David has a nice write-up on the Orion Broadband that nicely covers light pollution (dated but still valid):
https://www.cloudynights.com/articles/cat/cn-reports/accessories-reports/orion-skyglow-broad-band-light-pollution-filter-r2316

There is a book on Astronomical Filters, but frankly it barely covers "Nebula" Filters and concentrates on other types for visual & for astrophotography. Again, I don't recommend it for "Nebula Filters" but here it is:
https://www.amazon.com/Choosing-Astronomical-Filters-Practical-Astronomy/dp/1493910434/ref=sr_1_1?crid=2KSTDJATYAGH7&keywords=astronomy+filters&qid=1656854662&s=books&sprefix=astronomy+filters%2Cstripbooks%2C47&sr=1-1&ufe=app_do%3Aamzn1.fos.18ed3cb5-28d5-4975-8bc7-93deae8f9840

Lastly, when I started buying filters around 2000, I found Phil Harrington's book series "Starware" (the Consumer Reports for Astro Equipment) extremely helpful in learning & understanding. Granted, I think the last update was in 2007 so it's very dated re: what's on the market *now* - but for basic understanding of what they do it's excellent. I asked Phil years ago (at NEAF) if he'd update it and he said - paraphrased - "No, there's too much information available on the Internet for free and neither he nor his publisher had a desire for a new edition".

https://www.amazon.com/Star-Ware-Astronomers-Telescopes-Accessories/dp/0471750638/ref=sr_1_1?crid=3HV813L4IPEUD&keywords=starware&qid=1656857001&s=books&sprefix=starware%2Cstripbooks%2C67&sr=1-1

Lastly, I'll attach a short article from ASTRONOMY that Phil wrote a long, long time ago (2005?).

In summary, check the links, attachment - and - look for David Knisely's articles & posts online. If you need help finding his posts, reply back.

Cheers,

Troy


Troy Riedel
 

Dino,

I just realized I didn't include Jim Thompson ... he's THE man that does a lot of his own testing & posts his spectrographs online ... he stays pretty current. He posts at Cloudynights.com but here's his personal web site: http://karmalimbo.com/aro/index.htm

Another great [free] primer on all filters ... & he overlays multiple graphs over each other so you can compare sets of Narrowband filters, O-III filters, etc.

Between Jim & David Knisely, they've been my long-distance filter mentors.

Cheers mate,

Troy


preciousmyprecious
 

This is fantastic, Troy!

Carpe Noctem
Bill McLean


On Sunday, July 3, 2022, 10:07:27 AM EDT, Troy Riedel <troy.riedel@...> wrote:


Dino,

Plenty of good resources online ... anything by David Knisely will be good. He's active on CloudyNights.com & he's had reviews published in ASTRONOMY Mag (maybe S&T, too?).

Here's an excellent primer:
https://www.prairieastronomyclub.org/useful-filters-for-viewing-deep-sky-objects/

David has a nice write-up on the Orion Broadband that nicely covers light pollution (dated but still valid):
https://www.cloudynights.com/articles/cat/cn-reports/accessories-reports/orion-skyglow-broad-band-light-pollution-filter-r2316

There is a book on Astronomical Filters, but frankly it barely covers "Nebula" Filters and concentrates on other types for visual & for astrophotography. Again, I don't recommend it for "Nebula Filters" but here it is:
https://www.amazon.com/Choosing-Astronomical-Filters-Practical-Astronomy/dp/1493910434/ref=sr_1_1?crid=2KSTDJATYAGH7&keywords=astronomy+filters&qid=1656854662&s=books&sprefix=astronomy+filters%2Cstripbooks%2C47&sr=1-1&ufe=app_do%3Aamzn1.fos.18ed3cb5-28d5-4975-8bc7-93deae8f9840

Lastly, when I started buying filters around 2000, I found Phil Harrington's book series "Starware" (the Consumer Reports for Astro Equipment) extremely helpful in learning & understanding. Granted, I think the last update was in 2007 so it's very dated re: what's on the market *now* - but for basic understanding of what they do it's excellent. I asked Phil years ago (at NEAF) if he'd update it and he said - paraphrased - "No, there's too much information available on the Internet for free and neither he nor his publisher had a desire for a new edition".

https://www.amazon.com/Star-Ware-Astronomers-Telescopes-Accessories/dp/0471750638/ref=sr_1_1?crid=3HV813L4IPEUD&keywords=starware&qid=1656857001&s=books&sprefix=starware%2Cstripbooks%2C67&sr=1-1

Lastly, I'll attach a short article from ASTRONOMY that Phil wrote a long, long time ago (2005?).

In summary, check the links, attachment - and - look for David Knisely's articles & posts online. If you need help finding his posts, reply back.

Cheers,

Troy


galacticprobe
 

Wow! Thanks to everyone for the info! The links are saved so I can get at them with ease, and the book is in the wife's Amazon basket... so I just have to ask her to finish the purchase. (She's smart; she doesn't give me the passwords to the final stages of purchasing because she knows I'd have us in the poorhouse in no time!) And when I check out Jim Thompson's site, if I work up the nerve to contact him directly, I may drop your name, Troy, (and my BBAA membership) to let him know how I got referred to him. At least then he won't think I'm just a nut job - at least no more so than any other amateur astronomer is!Smile

"Keep looking up!"
Dino.


-----Original Message-----
From: Troy Riedel <troy.riedel@...>
To: BackBayAstro@groups.io
Sent: Sun, Jul 3, 2022 10:25 am
Subject: Re: [BackBayAstro] A bit of filter addendum

Dino,

I just realized I didn't include Jim Thompson ... he's THE man that does a lot of his own testing & posts his spectrographs online ... he stays pretty current. He posts at Cloudynights.com but here's his personal web site: http://karmalimbo.com/aro/index.htm

Another great [free] primer on all filters ... & he overlays multiple graphs over each other so you can compare sets of Narrowband filters, O-III filters, etc.

Between Jim & David Knisely, they've been my long-distance filter mentors.

Cheers mate,

Troy


Troy Riedel
 

Dino,

Are you a member of Cloudynights.com? It's owned & sponsored by the online retailer Astronomics.com (https://www.astronomics.com).  Cloudy Nights (CN) has classifieds for picking-up used gear (https://www.cloudynights.com/classifieds/category/1-root/?sort_key=date_added&sort_order=desc) and a plethora of Forums (https://www.cloudynights.com/index/).

Jim & David have thousands of posts there. You don't have to be a member to read the Forum posts, but you do if you wish to post a question or comment (you have to be a member for 30-days before you can post equipment you wish to sell). Anyway, both of their user names are quite easy to remember ... "jimthompson" and "David Knisely". There are a lot of knowledgable amateurs there just like there are here in the Back Bay club. But the beauty of CN is the sheer volume of posts - in other words - the massive volume of information. I honestly spent years ... probably 5 or more years ... just reading and learning before I had the nerve to actually post anything myself. Check out the Beginner Forum and the Equipment Forum (further broken-down into sub-categories). That should keep you busy for months if not years.

Other members to look for? The late Tom Trusock (school teacher from Michigan) contributed reviews that were published in ASTRONOMY Magazine (https://www.cloudynights.com/topic/659557-a-stalwart-of-cloudy-nights-tom-trusock-has-passed-away/). His posts have been saved 'In Memoriam". Another great person to read is William "Bill" Paolini (a USAF Veteran!). He is an eyepiece guru (he has thousands of posts on CN - user name BillP) and he authored this: https://www.amazon.com/Choosing-Astronomical-Eyepieces-Practical-Astronomy/dp/1461477220/ref=sr_1_1?crid=1QUWIFND69238&keywords=William+%22Bill%22+Paolini&qid=1656973530&sprefix=william%2520%2522bill%2522%2520paolini%2Caps%2C48&sr=8-1

Lastly, the vendor of http://eyepiecesetc.com is a frequent & knowledgable contributor (user name Starman1).

Oh, there's Don Pensack ... I could go on & on but you get the point.

And remember, the book I linked via Amazon (https://www.amazon.com/Choosing-Astronomical-Filters-Practical-Astronomy/dp/1493910434/ref=sr_1_1?crid=18QY8Q35CEIJR&keywords=choosing+and+using+filters&qid=1656974005&s=books&sprefix=choosing+and+using+efilters%2Cstripbooks%2C59&sr=1-1&ufe=app_do%3Aamzn1.fos.18ed3cb5-28d5-4975-8bc7-93deae8f9840) isn't great detailing nebula/deep-sky filters (the topic of this original thread), but it does a good job covering color filters, solar filters, and helpful filters for astrophotography.

Okay, sorry for the long post. CN should keep you busy for the next couple of years.

Cheers,

Troy