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Upgrade from L-eNhance?

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#1 rapture91

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Posted 12 February 2024 - 05:00 PM

Hey there,

I‘ve been using the Optolong L-eNhance for more than a year now with my two setups:
- Askar FMA180Pro f/4.5 on AZ-GTi (max. 60 s subs unguided)
- 10“ f/3.75 Dobson on equatorial platform (max. 8 s subs)

I’m kind of still looking at other options which might improve SNR etc.

Given the fast f-ratios of my setups, the L-eXtreme would not be my choice. However, I found the IDAS NBZ with its 12 nm band passes intriguing.

Would I see a noticeable difference in my Bortle 5/6 skies when going from ~38 nm total bandwidth (L-eNhance) to ~24 nm (NBZ)? Also, would the NBZ be a better fit when imaging during full moon?

Thanks for your insight!

CS
Johannes

#2 Tymaishu

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Posted 12 February 2024 - 05:43 PM

Hey there,

I‘ve been using the Optolong L-eNhance for more than a year now with my two setups:
- Askar FMA180Pro f/4.5 on AZ-GTi (max. 60 s subs unguided)
- 10“ f/3.75 Dobson on equatorial platform (max. 8 s subs)

I’m kind of still looking at other options which might improve SNR etc.

Given the fast f-ratios of my setups, the L-eXtreme would not be my choice. However, I found the IDAS NBZ with its 12 nm band passes intriguing.

Would I see a noticeable difference in my Bortle 5/6 skies when going from ~38 nm total bandwidth (L-eNhance) to ~24 nm (NBZ)? Also, would the NBZ be a better fit when imaging during full moon?

Thanks for your insight!

CS
Johannes

I’ve been using the NBZ for sometime but started with the L enhance. The NBZ is a bit narrower but at 12nm it works great with my f3 and f4 systems. Honestly there are not enough advantages to stacking h beta. And given that the NBZ has much better halo control it’s a great upgrade.


Edited by Tymaishu, 12 February 2024 - 05:44 PM.

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#3 hyiger

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Posted 12 February 2024 - 06:06 PM

What camera are you using? l-Ultimate is the best in my opinion, especially if you live in a high Bortle environment. 



#4 bbasiaga

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Posted 12 February 2024 - 06:07 PM

Interesting to hear. I've the L enhance as well, and was looking st the NBZ.

Main difference seems to be on the blue end. As both are about 12nm on Ha. I wish they had a 7nm version to make the choice easier. The L extreme has halos. The Antlia does as well (5nm).

Interesting design on the NBZ too in that it can work equally well on fast systems.

Also looking at the L Quad enhance for broadband targets. But idk...seems like a gimmick.

#5 hyiger

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Posted 12 February 2024 - 06:14 PM

Also looking at the L Quad enhance for broadband targets. But idk...seems like a gimmick.

With the advent of LED lighting, broadband filters are useless. It's best for broadband to just shoot with an IR/UV cut then remove the gradients in post-processing. For emission nebula the l-Ultimate gives the best results. It's 3nm in both Ha and OIII


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#6 smiller

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Posted 12 February 2024 - 07:27 PM

In general, the narrower the better and B5/6 is bright enough to want a narrow filter, especially if imaging during a moon or targets low on the horizon.

 

You note concern about filter effectiveness at fast F-ratios due to spectrum shift.   Here is Jim Thompson’s report on the L-extreme and L-ultimate which addresses this concern:

 

https://www.research...Comparison_Test

 

In this you’ll see the L-Ultimate transmission on various F-ratios on Page 7, but you’ll have to interpolate for F3.75.    

 

However, I see you own the Nexus, as I do, and I screw my filter on the front of my Nexus so that it operates at the telescope’s Native F-ratio, which is F4.9 in my case.  The downside is the filter will take the brunt of dew and dust instead of the front optics of the Nexus.   For me that’s a good tradeoff.

 

Even at F3.75 it isn’t bad, but perhaps there are better choices with such a narrow bandpass.

 

What you lose with a narrower filter is Hb, Oiiia and NII compared to your current filter.

 

- Steven


Edited by smiller, 13 February 2024 - 10:31 AM.


#7 rapture91

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Posted 13 February 2024 - 03:44 AM

Wow, thanks for the many replies so far!

I‘m using an uncooled ZWO 533 camera with 3.76 mu pixels. I think the L-ultimate would be too narrow in combination with my limited exposures for the dobson.
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#8 smiller

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Posted 13 February 2024 - 10:45 AM

Wow, thanks for the many replies so far!

I‘m using an uncooled ZWO 533 camera with 3.76 mu pixels. I think the L-ultimate would be too narrow in combination with my limited exposures for the dobson.

That was exactly my concern when I first bought a dual narrowband filter, so I started with the more conservative IDAS NBZ.  Also with short exposures, read noise is a factor with narrowband even with modern CMOS cameras in high gain mode, so you lose some of the benefits of a very narrow filter because of the contribution of read noise, so I was a little concerned about that too.

 

However, I found that I could take very short exposures with the IDAS NBZ down to one to two seconds, so that gave me confidence that I could get away with a narrower filter.

 

When I got the Nexus reducer and also a large pixel ASI2400MC, (5.94um), I knew I was well positioned to use the narrowest of filters because I just quadrupled the amount of light going to each pixel. Plus I did the math on read noise and it turned out that I still gained the vast majority of the advantage especially with this large pixel camera at 6 to 8 second exposures, which is what I typically use.

 

So I got the Optolong L-ultimate and it’s been great.    I can shoot down to 2-4 second exposures and be fine.
 

I’ve gone back and tried that filter in my ASI2600MC, which has 3.75um pixels, and it works great there too down to 4 second exposures, but I’m not sure how low I can go.   However my read noise spreadsheet indicates that I lose about 30-40% of the advantage of the narrower filter due to read noise at 8 second exposures.  So still 60-70% of the benefit, but a material loss due to read noise.  But you are 1 Bortle darker (when no moon) so you’re gain will be a bit less still. 
 

What exposure times are you limited to?

 

I have a 12” scope so it does collect 44% more starlight from each star than a 10” scope but with a smaller field of view so it sees fewer stars, both of which contribute to platesolving.  I think this is a wash.

 

My estimate is you’ll be fine, but you are right that it’s a potential concern.  You are 1 Bortle darker than me so you have less need to go as narrow as I do.   Certainly the somewhat wider L-Extreme or similar width filter will be a very safe choice for you.  I think that is where I would lean:  something in the 12nm total bandpass range: Very safe for platesolving and stacking, not hitting diminishing return for read noise, a tad cheaper.

 

Just a warning, just because it’s wider, it still may have sensitivity to low F-ratio spectrum shift, so watch out for that and read Jim Thompson’s reports.  He has additional reports that cover nearly every filter made.  Just search for his name and the filter you are interested in and you’ll probably find a link.


Edited by smiller, 13 February 2024 - 11:56 AM.


#9 rapture91

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Posted 13 February 2024 - 11:26 AM

Thanks for your invaluable input Steven! You‘re really looking into the subject deeply.

Regarding pixel size and light gathering power, platesolving is no option for my manual dobsonian :D

What I don‘t like about the L-eXtreme - as mentioned before - is the bad transmission at f/3.75 (can be circumvented by putting the filter right in front of the Nexus of course) and also at f/5. According to Jim Thompson‘s report, transmission at f/5 is hardly above 50 %, whereas the NBZ shows a transmission >90 % up to f/3.

Are there any other options with a similar total bandwidth of around 15 nm besides the L-eXtreme which are not $$$? :)

If not, I would strongly favor the NBZ.

#10 smiller

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Posted 13 February 2024 - 12:03 PM

Thanks for your invaluable input Steven! You‘re really looking into the subject deeply.

Regarding pixel size and light gathering power, platesolving is no option for my manual dobsonian laugh.gif

What I don‘t like about the L-eXtreme - as mentioned before - is the bad transmission at f/3.75 (can be circumvented by putting the filter right in front of the Nexus of course) and also at f/5. According to Jim Thompson‘s report, transmission at f/5 is hardly above 50 %, whereas the NBZ shows a transmission >90 % up to f/3.

Are there any other options with a similar total bandwidth of around 15 nm besides the L-eXtreme which are not $$$? smile.gif

If not, I would strongly favor the NBZ.

I’m not sure where you got the 50% transmission from he has earlier tables that show transmission from the very edge of the filter, before he integrates it across the entire filter.  Here is the key table in his report with the full filter transmission integration:

 

IMG_3080.jpeg

He has the L-extreme at 88.8% for OiiiB and 88.6% for Ha at F-4.9.   You are right it is poor at Ha at F3.0 with 68.3%.

 

 

But you are right, there aren’t many choices and most of the narrower ones degrade at low F-ratios:

 

https://www.research...Comparison_Test

 

Perhaps given the good transmission of the IDAS NBZ, it’s still a good choice, although a more minor upgrade for you.  You gain OiiiA and Nii for what that’s worth.   You drop light pollution bandpass from 37.5nm to 25nm, so by 1/3.

 

I’m curious why these filter designers don’t shift the bandpass a bit on their baseline filters so the optimum point is closer to ~F4 rather than F-infinity (0 degree incident light), but perhaps they are making the optimum tradeoff and I just don’t understand filter design.


Edited by smiller, 13 February 2024 - 12:21 PM.


#11 rapture91

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Posted 13 February 2024 - 03:23 PM

Aah you‘re right. I was referring to the graph showing edge transmission, not being aware of the integrated transmission over the whole filter.
Still, there are the halos around bright stars with the L-extreme which I‘m sure would annoy me :D

I‘m still kinda indecisive… you‘re right that the NBZ likely wouldn‘t be a major upgrade^^

I think there is also a version of the NBZ with two 10 nm bandpasses. Gotta have a look at that as well…

#12 smiller

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Posted 13 February 2024 - 05:33 PM

Aah you‘re right. I was referring to the graph showing edge transmission, not being aware of the integrated transmission over the whole filter.
Still, there are the halos around bright stars with the L-extreme which I‘m sure would annoy me laugh.gif

I‘m still kinda indecisive… you‘re right that the NBZ likely wouldn‘t be a major upgrade^^

I think there is also a version of the NBZ with two 10 nm bandpasses. Gotta have a look at that as well…

As you communicated the new IDAS NBZ II with 18nm of bandpass would be an excellent choice.  It also has the bandpasses well shifted so you get good performance from high F-ratios all the way down to ~F2, so it's a very flexible filter.  Their spec is about 95% transmission at the F-ratios you are using.

 

It'll be a very safe filter to use with shorter exposures, higher transmission than the L-Extreme which will help make up for the somewhat larger total bandpass, and the IDAS filters have a reputation for no or minimal halos.  Ignoring cost and the lack of used versions on the market, it's a excellent choice.   



#13 bbasiaga

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Posted 13 February 2024 - 05:52 PM

I really wish there were a halo-free 5-7nm band pass filter out there.  

 

The NBZ II is 8nm OIII and 10nm HA.  Vs your L-ehnance which is about 20-30nm OIII + Hb and 12nm HA.  So you should see some improvement in light pollution reduction.  I've been thinking about this one as well, but its close enough to the Enhance I already have, its hard to decide.   They need to make a 5nm version!  

 

Brian



#14 readkonrad

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Posted 13 February 2024 - 06:30 PM

I really like my regular version Antlia ALP-T Ha/OIII filter.  It is spec'd at 5nm bandpass and has been essentially halo free for me.  Not sure if they are all this good or a case of winning the "filter lottery". Be careful, there is also an Antlia ALP-T Highspeed version, I have seen halo issues reported on it (by Cuiv and others).

Here is a close crop of a 300 second raw frame of Alnitak. The only thing I did to the raw .fit was a histogram stretch and a crop.

alpt.jpg

300sec, Redcat 51, ASI2600mc, Antlia ALP-T filter



#15 smiller

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Posted 13 February 2024 - 06:52 PM

I really like my regular version Antlia ALP-T Ha/OIII filter.  It is spec'd at 5nm bandpass and has been essentially halo free for me.  Not sure if they are all this good or a case of winning the "filter lottery". Be careful, there is also an Antlia ALP-T Highspeed version, I have seen halo issues reported on it (by Cuiv and others).

Here is a close crop of a 300 second raw frame of Alnitak. The only thing I did to the raw .fit was a histogram stretch and a crop.

attachicon.gif alpt.jpg

300sec, Redcat 51, ASI2600mc, Antlia ALP-T filter

Here is Jim Thompson’s test report:

 

 https://www.research...Comparison_Test

 

He also notes that he saw no halo with the ALP-T.  The only negative I can see is the Ha transmissibility is on the lower end:  low 80’s at most common f-ratios.


Edited by smiller, 13 February 2024 - 11:24 PM.


#16 bbasiaga

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Posted 13 February 2024 - 10:17 PM

That's interesting. When you go to buy them they have disclaimers that you can't return them due to halos. Maybe they have improved the formulation over time.

Brian

#17 hyiger

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Posted 14 February 2024 - 11:20 PM

That's interesting. When you go to buy them they have disclaimers that you can't return them due to halos. Maybe they have improved the formulation over time.

Brian

I'm sure I'm wrong, but I only know of one vendor that has a halo non-return policy. The vendor's name vaguely rhymes with "angina."


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