Filters and band pass scanning

[FaintFuzzies]

I took my ten filters to Lumicon in the Sacramento area and had them scanned by Cary. Some results are as expected with a few surprises. Read on and please comment away.

Narrowband Filters

Interesting results. No degradation, but the transmission results of the Orion Ultrablock are a bit lower than I expected. I bought this filter way back in the early to mid 1990s. Showed no degradation of the coatings and it still looks nearly pristine. I liked it as it kills everything after the last O-III lines. No red stuff.
2707

The Omega NPB has a quite a bit of red pass through and gives this annoying "double star" appearance in the eyepiece. The scan confirms this. About 10 years old.
2708

Lumicon UHC filter - very good filter. After seeing this result, I will start using this more often than the Orion. I had the Orion since 1995. Great filter and loved it. I picked up this Lumicon about 3 years ago.
2709

Now after seeing these three results, I think I'm going to switch my main narrow band from Ultrablock to UHC. The NPB will remain my second choice.



Now on to my broadband filters

My very old Celestron Nebular Filter I got since I was in high school in 1984. Wow, pretty broad bandpass and okay transmission. Everything past about 530nm is cut off, which was pretty good considering that this was made almost 35 years ago. I used it with my old RV-6 and original AC powered Celestron C8. Yeah those made in the late 70's.
2710

The very first time I saw Hanny's Voorwerp through my friend's 48" telescope was with the CLS filter. Since that thing is almost 700 million light years away and the O-III lines were red shifted away to about 525-530nm (https://academic.oup.com/mnras/article/399/1/129/1086654/Galaxy-Zoo-Hanny-s-Voorwerp-a-quasar-light-echo), which is still within the CLS bandwidth. Nothing else worked at the time. Jimi ended up getting the Sloan G filter which helped too.
2711

Lastly, the Lumicon Deep Sky - a rock solid broadband filter. About 3 years old.
2712

After seeing the scans, my preference remains the same starting with the CLS, then the Deep Sky.


Line Filters

Lumicon O-III (about 10 years old) Replaced my old blue box O-III
2713

Lumicon H-Beta (about 10 years old) Also replaced my old blue box H-Beta
2714

Lumicon Comet (about 3 years old)
2715


Enjoy the scans. If you are interested in getting your filters scanned. Contact Cary at Lumicon.

[FaintFuzzies]

Some photos of the actual filters.

Narrowband
2716

Broadband
2717

Line
2718

[Don Pensack]

I've been studying and lab testing nebula filters for the last few years, borrowing about ten and buying about 40 of them.
Field studies resulted in some preferences that were born out by the lab tests afterwards.

The results of my filter field tests and lab tests revealed some winners in the filter wars:

H-Beta filters: TeleVue Bandmate II H-ß, Astronomik H-ß, Orion H-ß, (all current filters), and a 2009 Lumicon H-ß

O-III filters: TeleVue Bandmate II H-ß, Astronomik O-III Visual, Lumicon Gen. 3 O-III, (all current filters).

Narrowband (UHC-type) filters: TeleVue Bandmate II Nebustar, Lumicon UHC, Astronomik UHC, DGM NPB (all current filters)

Broadband/CLS filters: Baader UHC-S, Lumicon Deep Sky (all current filters)

Many brands of filters in each category had misplaced bandwidths, or too-wide bandwidths, or simply too-low transmissions at the necessary wavelengths.
A few, notably some O-III filters, only picked up one of the two O-III lines, making them more suitable for imaging than visual use.
I have lab test results for each filter and could provide them if desired. You won't go wrong with any of the filters I mention above.

There were also a couple really odd filters that worked well despite the lab tests:
The DGM GCE, which is a broadband filter of sorts that is SO gentle you could just leave it in all the time on all objects.
It turns up the contrast only very slightly, so it won't provide the best possible view of any object.
But I found it useful in conditions where I just wanted a tad darker background, but didn't want to up the magnification.

And the Baader Contrast Booster which still remains the single most useful Mars filter I've ever tested (which includes 10 color filters and 4 dielectric-coated ones).

If I didn't mention a filter you like, let me know and I probably tested it.

Clear skies,
Don

[Don Pensack]

I've been studying and lab testing nebula filters for the last few years, borrowing about ten and buying about 40 of them.
Field studies resulted in some preferences that were born out by the lab tests afterwards.

The results of my filter field tests and lab tests revealed some winners in the filter wars:

H-Beta filters: TeleVue Bandmate II H-ß, Astronomik H-ß, Orion H-ß, (all current filters), and a 2009 Lumicon H-ß

O-III filters: TeleVue Bandmate II O-III, Astronomik O-III Visual, Lumicon Gen. 3 O-III, (all current filters).

Narrowband (UHC-type) filters: TeleVue Bandmate II Nebustar, Lumicon UHC, Astronomik UHC, DGM NPB (all current filters)

Broadband/CLS filters: Baader UHC-S, Lumicon Deep Sky (all current filters)

Many brands of filters in each category had misplaced bandwidths, or too-wide bandwidths, or simply too-low transmissions at the necessary wavelengths.
A few, notably some O-III filters, only picked up one of the two O-III lines, making them more suitable for imaging than visual use.
I have lab test results for each filter and could provide them if desired. You won't go wrong with any of the filters I mention above.

There were also a couple really odd filters that worked well despite the lab tests:
The DGM GCE, which is a broadband filter of sorts that is SO gentle you could just leave it in all the time on all objects.
It turns up the contrast only very slightly, so it won't provide the best possible view of any object.
But I found it useful in conditions where I just wanted a tad darker background, but didn't want to up the magnification.

And the Baader Contrast Booster which still remains the single most useful Mars filter I've ever tested (which includes 10 color filters and 4 dielectric-coated ones).

If I didn't mention a filter you like, let me know and I probably tested it.

Clear skies,
Don

[Don Pensack]

My friend Oggie Golub, also known as LunarFox on cloudynights.com, will also test filters for free and he has tested quite a few and the results are here:
https://searchlight.semrock.com/?sid=a08a1af9-84ee-49d2-959d-153d7e7c0eb8
You can turn on/off individual filters in the upper right and even superimpose any filters you want.

[Bertrand Laville]

Hi Don,

Have you the possibility to test those two new filters (that I use visually and like them)
- SCT Duo narrowband: OIII 10 nm + Ha 10 nm, https://www.cyclopsoptics.com/astronomy-filters/stc-astro-duo-narrowband-filter-48mm-2/
- IDAS NB1: (Hb + OIII) 32 nm + Ha 20 nm, http://icas.to/space/optical-filter/NB1.htm

If you can, I would be very interested on your results
Thanks

Bertrand
http://www.deepsky-drawings.com/

[Bertrand Laville]

Good morning, everyone,



a drawing worthing better than any speech, here are the Viel East with the following filters:

a) Classic: Lumicon OIII/12 nm (year 2001) and Astrodon OIII/5 nm for veins (observation 2016)

b) the same background + the H alpha revised with Hutech NB1, and the OIII revised with STC Duo Narrow Band (observation of 2019 06 05)

Even T635, same eyepieces, same sky.



For the record:

NB1: (H beta + OIII) 32nm and (H alpha) 20 nm

2NB: OIII/ 10nm + Ha/ 10 nm


Clear skies for all

Bertrand
http://www.deepsky-drawings.com/

3551

[wvreeven]

Bertrand, I think you posted the same picture twice. Even the details about the observations are the same.

[Bertrand Laville]

Nope !
For the OIII, the third vein of the broom (the Eastest one) is much more detailed; moreover, there is a new patch at the Southest part of the broom, between the two main veins.
For the H alpha, it is more extended at the NE of the bright star, and more stronger at the SE of that star.
Of course, the differences are weak, but real, and a filter can't totally change the view. Otherwise I would have to write a "little book" to add the second date, powers, and filters, only for 1%.
The notes are the same for the two images, because 99% of both are the same.