Askar Filter HO + SO - Forums

Topic starter

Feb 9, 2023 · Edited: Feb 9, 2023

Hi all,

Today I received my Askar duo Magic Color 6nm HO + SO. I'm really excited to try them.
I actually using L-eXtrem duoband filter and I extract Hydrogen and Oxygen and assembly them for H-HOO combination.
With the Duo Magic Color from Askar filters, I have the possibility to make SHO assembly.

But, I'm questionning about the time exposure from OIII which will be 2 times higher than H and S:
- This 2 times higher exposure time will impact the data processing in PixInsight ?
- There is any "tips" with a higher signal on OIII or it is unnoticeable during data processing ?

Thanks for advices,

Stuart Taylor

Feb 9, 2023

I have the Askar D2 filter (Sii and Oiii) and I combine the results with my L Extreme filter (Ha and Oiii) to produce SHO images.

I used 600s exposures for both (at f/5.6) which was successful. But it doesn't matter if you use a different exposure time on each filter as the PI process (using WBPP is done separately for each filter). Channel extraction (for Ha, Sii and Oiii) is then done on each final integration and re-combined to produce the SHO result.

California Nebula (NGC1499)

Soul Nebula (combining two duoband filters)

Helpful

Maxime Martin

Topic starter

Feb 9, 2023

Stuart Taylor:
I have the Askar D2 filter (Sii and Oiii) and I combine the results with my L Extreme filter (Ha and Oiii) to produce SHO images.

I used 600s exposures for both (at f/5.6) which was successful. But it doesn't matter if you use a different exposure time on each filter as the PI process (using WBPP is done separately for each filter). Channel extraction (for Ha, Sii and Oiii) is then done on each final integration and re-combined to produce the SHO result.

California Nebula (NGC1499)

Soul Nebula (combining two duoband filters)

Thanks for your feedback. Do you have any issue with halos with Askar comparing to L-eXtrem ?

Michael Ring

Feb 9, 2023

Having twice the Oiii is actually helpfull, you have the choice to either integrate all Oiii from both filters and get better Signal to Noise ratio on that signal or you can cherrypick the best of your Oiii signal to improove sharpness/details in Oiii. But looking for details does not make sense on a lot of targets because most of the signal is in Ha and this usually also means best contrasts and details.
But for targets like the Flaming Star Nebula and the California Nebula, which have quite weak Oiii the higher SNR will help a lot to bring out the Oiii without too much Noise.
Here'S my version of the California Nebula with the filter:
https://www.astrobin.com/ejsquu/

So far I have not yet used the Askar filter on Orion or Horsehead, I am currently shooting a panorama of the Rosette Nebula Area and the stars there are not that bright.

Helpful Engaging

Stuart Taylor

Feb 10, 2023

Maxime Martin:

Thanks for your feedback. Do you have any issue with halos with Askar comparing to L-eXtrem ?

I find the halos are less bad with the Askar D2

Michael Ring:
Having twice the Oiii is actually helpfull, you have the choice to either integrate all Oiii from both filters and get better Signal to Noise ratio on that signal

This is what I do. I extract the oxygen signal from both and add them

jmdl101

Feb 10, 2023

Maxime Martin:

@Maxime Martin The D1 and D2 both have pretty rough halos for me. It's a pretty big problem coming from the IDAS NBZ which was halo free. Hopefully Askar will figure out how to fix it, otherwise we just have another l-extreme on our hands. Here's a screenshot I sent to sharpstar recently demsotratimg the halos in both filters. Obviously Alnitak is rough, but I also have halos is much dimmer stars, like in the California Nebula.

Concise

jmdl101

Feb 10, 2023 · Edited: Feb 10, 2023

To answer you original question, doubling the Oiii exposure doesn't hurt at all, it just makes for a less noisy Oiii channel. The real issue is the very faint Sii channel normally, so I try to double the exposure time with the D2 filter if possible.

I normally stack each filter with separate rgb selected in WBPP, if you do them all at once, they'll all be registered and aligned to each other already too. Then just take the D1 red as Ha, D2 red as Sii, then pixelmath to add each filter's blue and green together as a D1 and D2 Oiii, then linear fit all images to Sii, then pixelmath to combine the two Oiii images together into one final Oiii (D1+D2)/2. Then finally channel combination to make the SHO pallete image. Sounds like a lot, but it only takes a few minutes. After this just standard SHO processing.

For the stars, since I can't stand the weird colors SHO processing leaves them, I take out the stars after running blur exterminator on the SHO image, then process the image without them. I use the stars from the D1 filter, combined as rgb, ABE, blurX, SPCC, scnr green, then remove them with starX to recombine later either in photoshop or pixinsight.

Helpful

Maxime Martin

Topic starter

Feb 10, 2023

Michael Ring:
Having twice the Oiii is actually helpfull, you have the choice to either integrate all Oiii from both filters and get better Signal to Noise ratio on that signal or you can cherrypick the best of your Oiii signal to improove sharpness/details in Oiii. But looking for details does not make sense on a lot of targets because most of the signal is in Ha and this usually also means best contrasts and details.
But for targets like the Flaming Star Nebula and the California Nebula, which have quite weak Oiii the higher SNR will help a lot to bring out the Oiii without too much Noise.
Here'S my version of the California Nebula with the filter:
https://www.astrobin.com/ejsquu/

So far I have not yet used the Askar filter on Orion or Horsehead, I am currently shooting a panorama of the Rosette Nebula Area and the stars there are not that bright.

Thanks for your comment. I hope I will have clear sky as soon as possible to test them

To answer you original question, doubling the Oiii exposure doesn't hurt at all, it just makes for a less noisy Oiii channel. The real issue is the very faint Sii channel normally, so I try to double the exposure time with the D2 filter if possible.

I normally stack each filter with separate rgb selected in WBPP, if you do them all at once, they'll all be registered and aligned to each other already too. Then just take the D1 red as Ha, D2 red as Sii, then pixelmath to add each filter's blue and green together as a D1 and D2 Oiii, then linear fit all images to Sii, then pixelmath to combine the two Oiii images together into one final Oiii (D1+D2)/2. Then finally channel combination to make the SHO pallete image. Sounds like a lot, but it only takes a few minutes. After this just standard SHO processing.

For the stars, since I can't stand the weird colors SHO processing leaves them, I take out the stars after running blur exterminator on the SHO image, then process the image without them. I use the stars from the D1 filter, combined as rgb, ABE, blurX, SPCC, scnr green, then remove them with starX to recombine later either in photoshop or pixinsight.

Ok, thanks for the little process in PI.
I will make you un feedback when a clear sky appears

Thanks a lot for your recommandations. Help a lot

Maxime Martin

Topic starter

Feb 20, 2023

Hello all,

This is my first attempt with D1+D2 filters. First SHO processing.
Happy about these filters even though I can see some halos around stars. Not as much as L-eXtrem but I can see them.

An another question, do you have any idea about the efficiency of these filters with fast tube ? I'm thinikg about to buy a reductor x0.75 from Starizona and get f/3.75. Do you you if these filters will loss efficiency with f/ration under 4 ?

Thanks for your advices

jmdl101

Feb 20, 2023

This is from my 8" newt with the 0.75x Nexus and D1 filter. Seems to work fine so far at f3. The halo picture is a single 30s exposure on Alnitak just to confirm the halos on a third scope.