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Which is better, HA/ OIII/ SII filters or L-enhance/ extreme

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#1 Karlp295

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Posted 15 August 2022 - 04:23 AM

I wonder if adding to my existing HA filter to use with my DSLR Canon 600D modified would be a good idea as a next step?

I am thinking of EITHER getting:

 

  • an oxygen III filter 
  • a duo band like an L enhance or l extreme

Do I really need to get a S II filter? 

 

Which of these alternatives do you think is best for my set up (DSLR modified camera with 130mm reflector)?

I guide and have a CEM 26 Ioptron mount and can do long exposures.

 

Thanks for any advice, I keep seeing excellent photos that seem way beyond my equipment right now, will filters like these help?

 

 

 

 

 



#2 F.Meiresonne

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Posted 15 August 2022 - 05:35 AM

An SII filter is only needed if you want SHO palette.

 

L-enhance and L-extreme are more HOO oriented imho as they let only Ha and OIII through and a little H b but no SII, which makes the SHO hubble palette out of reach.

 

L-enhance and L-extreme are great filters imo, but they do kill starcolor.


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#3 Pantilas

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Posted 15 August 2022 - 05:51 AM

A OIII filter only makes sense if you plan to go mono in the future. A duo narrowband filter does the same and you get Ha in the same session for free.

The L-extreme catches Ha and OIII, the L-enhance Hb, Ha and OIII. If you like to seperate hydrogen and oxygen in your image, the L-extreme is better, but it will give you some star halos you have to get rid of in post.
 


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#4 mjanzou

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Posted 15 August 2022 - 06:43 AM

Does the l-enhance have the same star halos as the extreme?

#5 Pantilas

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Posted 15 August 2022 - 07:26 AM

No, it has significantly less.
Check this: https://astrogeartod...ooting-nebulas/



#6 the Elf

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Posted 15 August 2022 - 11:26 AM

The ideal camera for NB filters Ha/O3/S2 is a cooled mono camera. The low priced ones with small sensors work well with 1.25'' filters. An APS-C sized DSLR like the 600D requires 2'' filters. So there is no point buying 3 large NB filters for twice the price now expecting to use them on an astro camera one fine day. If you want to go that route save money for a camera plus a filter wheel plus filters just large enough for that camera. The entry level ZWO 1600 is sold in a bundle with all that stuff.

Second best choice is a mono moded DSLR as Freddy and me own one (600D, modded in the US). The downside compared to a dedicated astro camera is lack of cooling and the price for the conversion is high. Nonetheless I'm very happy with it as it saves me from using the computer in the field and I hate computers. Minority decision, fractions of a percent go that route.

3rd best - and that is near poor - is a modded camera as it picks up Ha better. Well, wait, it's not that easy. Some brands pick up Ha better than others and the 600D does quite a nice job. Modding will approx. double your signal, I have measurements if you need more detail. Anyway, if you mod it, it is slightly better but far from a mono camera.

Worst choice is an unmodded DSLR, but as I said, Canon is not that bad compared to others. Now why is this a poor choice? You have next to zero sensitivity for S2, you have low sensitivity for Ha and both only trigger 1 out of 4 pixels on the sensor. O3 works well, 2 out of 4 pixels get a signal.

 

Some practical considerations: how many objects come with an O3 level high enough for an uncooled DSLR? In my part of the sky it is Veil and Dumbbell. Most other objects need 10+ hours and still come out noisy. Using the L-extreme instead does not solve any of the problems stated so far. Only if you have an object with approx. the same signal in Ha and O3 you save a lot of time because you get both images together. In my part of the sky these objects are.... you guess it. Veil and Dumbbell. For all other objects O3 is way, way, way weaker than Ha so you need different exposure times for the two. S2? Probably not. Only very few objects come with significant S2 and the DSLR is not very sensitive there. In the L-extrem Ha and S2 cannot be distinguished because both are red.

 

So, which one to buy? Consider a full moon night. The moon has the same spectrum as the sun so there is plenty of signal in the green part. You can use either L-extreme or Ha, the result will be the same more or less. In case of the L-extreme your green channel will just be bright, in case of the Ha it will be dark but no structure in either case. So, Veil and Dumbbell aside, grab the cheaper one!

 

 

Here is the 600Ds spectral sensitivity. I work in an optics lab and measured this myself:

 

rel_Sensitivity_Canon_600D.gif

 

and this is my T3i mono full spectrum

rel_Sensitivity_Canon_T3i_mono.gif

 

Hope this helps.

CS

 

the Elf


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#7 FrostByte

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Posted 15 August 2022 - 11:58 AM

Another thing you can consider, if you're interested in SII, is a dual-band SII/OIII filter like the IDAS NB3 filter with a modded or full-spectrum camera. It does need to be used in conjunction with an IR-block filter, but this would allow you to collect both OIII and SII wavelengths simultaneously with your color sensor. Paired with a dual-band Ha/OIII filter, you'd be able to shoot SHO images.



#8 Pantilas

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Posted 15 August 2022 - 12:04 PM

The ideal camera for NB filters Ha/O3/S2 is a cooled mono camera. The low priced ones with small sensors work well with 1.25'' filters. An APS-C sized DSLR like the 600D requires 2'' filters. So there is no point buying 3 large NB filters for twice the price now expecting to use them on an astro camera one fine day. If you want to go that route save money for a camera plus a filter wheel plus filters just large enough for that camera. The entry level ZWO 1600 is sold in a bundle with all that stuff.

Second best choice is a mono moded DSLR as Freddy and me own one (600D, modded in the US). The downside compared to a dedicated astro camera is lack of cooling and the price for the conversion is high. Nonetheless I'm very happy with it as it saves me from using the computer in the field and I hate computers. Minority decision, fractions of a percent go that route.

3rd best - and that is near poor - is a modded camera as it picks up Ha better. Well, wait, it's not that easy. Some brands pick up Ha better than others and the 600D does quite a nice job. Modding will approx. double your signal, I have measurements if you need more detail. Anyway, if you mod it, it is slightly better but far from a mono camera.

Worst choice is an unmodded DSLR, but as I said, Canon is not that bad compared to others. Now why is this a poor choice? You have next to zero sensitivity for S2, you have low sensitivity for Ha and both only trigger 1 out of 4 pixels on the sensor. O3 works well, 2 out of 4 pixels get a signal.

 

Some practical considerations: how many objects come with an O3 level high enough for an uncooled DSLR? In my part of the sky it is Veil and Dumbbell. Most other objects need 10+ hours and still come out noisy. Using the L-extreme instead does not solve any of the problems stated so far. Only if you have an object with approx. the same signal in Ha and O3 you save a lot of time because you get both images together. In my part of the sky these objects are.... you guess it. Veil and Dumbbell. For all other objects O3 is way, way, way weaker than Ha so you need different exposure times for the two. S2? Probably not. Only very few objects come with significant S2 and the DSLR is not very sensitive there. In the L-extrem Ha and S2 cannot be distinguished because both are red.

 

So, which one to buy? Consider a full moon night. The moon has the same spectrum as the sun so there is plenty of signal in the green part. You can use either L-extreme or Ha, the result will be the same more or less. In case of the L-extreme your green channel will just be bright, in case of the Ha it will be dark but no structure in either case. So, Veil and Dumbbell aside, grab the cheaper one!

 

 

Here is the 600Ds spectral sensitivity. I work in an optics lab and measured this myself:

 

attachicon.gifrel_Sensitivity_Canon_600D.gif

 

and this is my T3i mono full spectrum

attachicon.gifrel_Sensitivity_Canon_T3i_mono.gif

 

Hope this helps.

CS

 

the Elf

Do you really need a 2" filter for APS-C? Isn't a 36mm filter big enough?
Does the L-extreme pick up SII? It's 7nm wide, Ha is at 656nm, SII 672nm and should be blocked?
OIII is at 496nm and 501nm, so three of four pixels should get a signal (2x green, 1x blue) right? This also mitigates the fact that there is normally much less OIII a bit?
 



#9 the Elf

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Posted 16 August 2022 - 04:49 AM

Do you really need a 2" filter for APS-C? Isn't a 36mm filter big enough?
Does the L-extreme pick up SII? It's 7nm wide, Ha is at 656nm, SII 672nm and should be blocked?
OIII is at 496nm and 501nm, so three of four pixels should get a signal (2x green, 1x blue) right? This also mitigates the fact that there is normally much less OIII a bit?
 

With my RC8 and reducer I see vignetting by the flipped up mirror. This tells me that I need the large filter. Otoh it does not mean imaging with a smaller filter is impossible. Depending on the imaging train there can be more or less vignetting. If in doubt cut out circular rings from cardboard and make a with/without comparison.

The L-extreme does not pick up S2 afaik. Did not want to say it does, sorry for the confusion.

Looking at the above curves you see that many colors are picked up by all three channels only with different intensity. So there is blue signal and even some red. The 'much less' is orders of magnitudes so a 1.5x does not mitigate that much. There are two topics we must not confuse. The OP's question is about what to buy. Once someone has made a decision (be it wise or crazy) and has some real life data you have to check that individual data set and make a decision if green only or blue and green leads to a better image in terms of noise and resolution. It also depends on your way of processing. You might go the simple way, take the image as it is, accept the color that comes out of the camera and call it a day. You could also try to extract the best monochrome image from your O3 and to do so you have to adjust the blue level to the green level. That means the noise level gets higher. If you now combine green and blue you might end up with a higher or lower SNR compared to green only. Then you either toss the blue or you don't. After having extracted a monochrome Ha as well you might go Steve Cannistra's way of pseudo S made from Ha and O3 (which is in simple terms a fake not an attempt to reconstruct any S2) to make an image that has the look and feel of HSO but isn't. After all it is art what we are doing here, so nothing wrong with his method. You might even find that debayer at full resolution is a bad decision and go for super pixel instead. For color measurement in an industrial application I always go for super pixels. You might even extract some sort of luminance from the full res and apply it to an upsampled color image from super pixels and find the result to look better because it has less color noise. So what to buy and how to process are two different stories.

 

To the OP: once you have data feel free to upload it to dropbox and let the community process it. You will be surprised how much the results will differ.

Here is my favorite example. My processing:
https://www.elf-of-l...l_2020_1080.jpg

CN member OhmEye, exact same data:

https://www.elf-of-l...l_by_OhmEye.jpg

:-O



#10 T~Stew

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Posted 16 August 2022 - 10:13 PM

For a color camera, a duo band filter makes a lot more sense than individual filters. A single duo band filter will work just fine, and lack of SII is not a huge deal... very few nebula have strong SII and many on here can 'fake' the SHO pallet with duo band data and it looks spectacular. I used a duo band filter with my modded 60D (very similar to 600D) and it worked well. I did start buying 2" narrowband filters with the intention of mono astro cam later, and started with SII so I could do SHO with my dslr. I got to say, SII took a lot more exposure time and was still weak. It added 4 more days to my North American nebula, and the data was still far more noisy than that from my duo band filter. I suspect I could have made just as nice of image without it. So I'd say SII is totally optional. 



#11 tosjduenfs

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Posted 16 August 2022 - 10:51 PM

Duo narrowband would be best for a color camera.  I sold my L-extreme for the IDAS NBZ, no more star halos.


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#12 galacticinsomnia

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Posted 16 August 2022 - 11:33 PM

Lenhance for DSLR's and mirrorless IMO.

A lot more fun to play with for sure.  More data is yummy. 

Cleaar Skies !!




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