94 replies to this topic

[j21blackjack]

I am thoroughly enjoying my Askar 6nm D1/D2 set. Yes, the band passes for Oiii and Sii are wider than Ha, 7.5 and 9nm is seems with Ha being 6nm. Sharpstar has explained this fairly well in the other posts regarding the Askar filters. I think they should update the descriptions, but basically it's for halo suppressing, which they seem to be great at. The D2 is significantly better than the NB3, which I owned for a year before switching. The D1 and NBZ are probably very close in comparison, but the Askar still has tighter bands than the NBZ, and seems to perform well down to f2. I am still a huge fan of the NBZ, but switched to the D1 to have matching filters in bands and thicknesses. I have a few of my first SHO Askar images on my astrobin, username jmdl101.

[nate9862]

I recently bought the l-ultimate from Optolong.  Bad, bad green reflections and halos around bright stars.  I never would've bought it if I know that.  I don't care what zwo says on their site. Nearly impossible to remove in post processing.  

 

[jerr]

Hi Nate,

 

There is noting special having a green cast in the subs. Common patter of the bayer matrix is 1 red, 1 blue and 2 green, so green prevails.
I see at your footnote that you use Photoshop. You can easily remove the green cast with HLVG plugin that is available for free.

[StuartT]

Hi Stuart any feedback yet? I have the NBZ and I am looking for an alternative to the NB3 as I cannot find one anywhere, having been discontinued.   

Hi. Yes indeed. I'm very happy w the new Askar D2 filter. I've developed a technique for extracting the Ha, Sii and Oiii from them (Askar D2 and L Extreme) then combining to form an SHO image. Only done one target yet (here) but working on the Rosette now also.

Edited by StuartT, 25 January 2023 - 06:13 AM.

[nate9862]

Hi Nate,

 

There is noting special having a green cast in the subs. Common patter of the bayer matrix is 1 red, 1 blue and 2 green, so green prevails.
I see at your footnote that you use Photoshop. You can easily remove the green cast with HLVG plugin that is available for free.

It's not a 'green cast'.  I know how to remove the excess green from the bayer matrix in post-processing.  It's specifically around very bright stars. If you look at the image closely, the bright stars have a very drastic green halo that is very, very difficult to remove.  That photo is already processed and color-balanced.  The halo exists pretty much only in the green (OIII) channel of the L-Ultimate subs.  I took a set of regular RGB subs with an L-Pro and that artifact does not exist.  

[msacco]

It's not a 'green cast'.  I know how to remove the excess green from the bayer matrix in post-processing.  It's specifically around very bright stars. If you look at the image closely, the bright stars have a very drastic green halo that is very, very difficult to remove.  That photo is already processed and color-balanced.  The halo exists pretty much only in the green (OIII) channel of the L-Ultimate subs.  I took a set of regular RGB subs with an L-Pro and that artifact does not exist.  

Not talking about the halos, but I'm not really sure about the green part you're referring to. this is for example just taking the image to pixinsight and running SCNR(which is equivalent to PS HLVG plugin).

 

 

 

The halos are still present but the green cast you're referring to seems rather fine to me.

[Digitaliz.se]

I have L-Ultimate, but haven’t had any green color cast. This filter is better than L-eXtreme which I also had as almost as good as the Ultimate.

 

/Stefan

[nateman_doo]

May I make a suggestion in an effort to help with the halos?  Putting a good IR/UV cut filter in front of everything.  I tried this with my wide field setup and there wasn't even a hint of a halo.  I used the Astronomik L3 before my image train here:

 

 

 

 

 

My original triad filter:

 

I havent had the chance to test this out on my R/C, but it worked well for both my refractors.

[msacco]

May I make a suggestion in an effort to help with the halos?  Putting a good IR/UV cut filter in front of everything.  I tried this with my wide field setup and there wasn't even a hint of a halo.  I used the Astronomik L3 before my image train here:

 

 

 

 

 

My original triad filter:

 

I havent had the chance to test this out on my R/C, but it worked well for both my refractors.

The question is whether there is also impact on the quality of the image. More glass could always worsen the image I guess, but an interesting idea.

[TareqPhoto]

I should buy L-Ultimate

[nate9862]

I will say that I was genuinely amazed at my subs using the L-Ultimate the first time I got a well-focused 3min exposure on my ASI 294MC.  Rosette was really impressive, too.  I didn't get many green halos imaging Rosette or California nebulas, mostly because there aren't any super bright stars in that field.  

 

I never thought about adding a second uv/ir cut filter.  I assumed that uv/ir would already be excluded based on the small band gap of the L-Ultimate.  Unless there is uv/ir reflection on the scope-end of the filter.  I saw an analysis that said those green reflections are caused by a certain about reflectivity on the scope-facing coating which reflect off the filter then back through the imaging train somehow.  I don't really know what to make of it all.  I might just try to take shorter subs when there are bright stars in the field.

[Zambiadarkskies]

May I make a suggestion in an effort to help with the halos? Putting a good IR/UV cut filter in front of everything. I tried this with my wide field setup and there wasn't even a hint of a halo. I used the Astronomik L3 before my image train here:






My original triad filter:


I havent had the chance to test this out on my R/C, but it worked well for both my refractors.

Interesting. So the L3 was mounted as well as the Triad? I recently purchased an L3 so will give it a try when I am back in Zambia with my gear.

Edited by Zambiadarkskies, 25 January 2023 - 01:54 PM.

[TareqPhoto]

I will say that I was genuinely amazed at my subs using the L-Ultimate the first time I got a well-focused 3min exposure on my ASI 294MC.  Rosette was really impressive, too.  I didn't get many green halos imaging Rosette or California nebulas, mostly because there aren't any super bright stars in that field.  

 

I never thought about adding a second uv/ir cut filter.  I assumed that uv/ir would already be excluded based on the small band gap of the L-Ultimate.  Unless there is uv/ir reflection on the scope-end of the filter.  I saw an analysis that said those green reflections are caused by a certain about reflectivity on the scope-facing coating which reflect off the filter then back through the imaging train somehow.  I don't really know what to make of it all.  I might just try to take shorter subs when there are bright stars in the field.

I have very simple answer, i will never use L-Ultimate to shoot Horsehead nebula or even Orion, those regions are mainly H L RGB, i really don't like any OIII or even SII in those regions, so should i kill the filter because i use it in a region where i shouldn't use and it is optional?

 

Another answer is, i want to get Ha & OIII signal only, not the stars, i really don't care much about NB stars first place, i will use the color camera with dual band filter and use it again for RGB stars, so simple as that, i think i waited so long time now without any imaging and no dual band filters while many who bought cameras color OSC before/after me already tried several ones such as L-extreme and NBZ and Triad and L-Ultimate, and always the topic of halo is coming up, so i don't have good budget but i sacrificed a lot so far to buy more, i will keep sacrifice so i never get into this point of what to do if the filter isn't delivering that quality, to me it will be cheaper for me to buy a color camera and scope than only buying larger size Astrodon/Chroma LRGB/NB filters anyway.

[jerr]

This is a result with single pass of HLVG

Attached Thumbnails

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[nateman_doo]

Interesting. So the L3 was mounted as well as the Triad? I recently purchased an L3 so will give it a try when I am back in Zambia with my gear.

The L3 and triad were never used together.  The L3 IRUV went in front of my refractors and it completely fixed all the halos.  It has its own anti-reflective coating. I would imagine a more expensive anti-reflective IRUV like Lumicon and Astrodon would work even better?  Was just showing the triad halo without any IRUV vs my narrowband with IRUV.  I am going to test with the Triad and Astronomik IRUV L3 whenever I finish making a filter drawer for my camera.  

[TareqPhoto]

It is kind of what the quality of scopes and the figure it is, because there is no way that a filter will make a halo in one setup and then no halo in another, which means the filter isn't the cause, if it is the filter then there will be halo always with any setup, and i saw enough examples from people all around using L-Ultimate with no halo to very minimal but not the brighter stars, so i can always finger to the setup itself then, i remember i used my Optolong NB filters in front of another filter can't remember which, and it caused that kind of halo that i thought it was new nebula or planetary nebula itself, but when i removed that filter and used NB filters alone the halo minimized but didn't go away completely.

[nate9862]

It is kind of what the quality of scopes and the figure it is, because there is no way that a filter will make a halo in one setup and then no halo in another, which means the filter isn't the cause, if it is the filter then there will be halo always with any setup, and i saw enough examples from people all around using L-Ultimate with no halo to very minimal but not the brighter stars, so i can always finger to the setup itself then, i remember i used my Optolong NB filters in front of another filter can't remember which, and it caused that kind of halo that i thought it was new nebula or planetary nebula itself, but when i removed that filter and used NB filters alone the halo minimized but didn't go away completely.

Yeah, might be true. I don't get halos with any other filters.

[TareqPhoto]

I am ready to take a risk really, which will force me to something else, i still can't decide if i should wait little bit to see if any new improvement will be out to current dual filters or it won't get any better than now, and in all cases i am planning to use stars from another filter and not dual band filter, so maybe in this case i shouldn't worry or care about how bad halo or any halo caused by it.

[900SL]

Based on user feedback so far, I think I'll add the Askar D2 Oiii Sii filter to the NBZ I already have, despite my misgivings about Askar and their dodgy marketing practices, as I appear to have no alternative

 

If anybody is using these in combination, any issues with backfocus?

 

NBZ 2.5mm, ASKAR 1.85mm so looks like 0.2mm potential difference so I'm not worried about that with a 533MC sensor

 

FOV should be the same so stacking no issues due to variation in scaling?

Edited by 900SL, 26 January 2023 - 05:08 AM.

[j21blackjack]

Based on user feedback so far, I think I'll add the Askar D2 Oiii Sii filter to the NBZ I already have, despite my misgivings about Askar and their dodgy marketing practices, as I appear to have no alternative

If anybody is using these in combination, any issues with backfocus?

NBZ 2.5mm, ASKAR 1.85mm so looks like 0.2mm potential difference so I'm not worried about that with a 533MC sensor

FOV should be the same so stacking no issues due to variation in scaling?

Unless you're using something like a Rasa, the difference in filter thickness shouldn't mess up your backfocus, it will on a Rasa though. You'll just need to refocus after changing the filter out. Even between the D1 and D2, there's a difference in focus enough that I need to run a new autofocus. I could probably just set a filter offset in Nina for changing them out, but an autofocus only takes about 2 minutes anyway.

Hopefully Sharpstar/Askar will update the descriptions soon for the filters, I know some resellers are asking them to fix it also since people are complaining. I would have still bought them even though they aren't 6nm across all 3 bands, and I think they are priced pretty fair, compared to other filters around the same range.

Another new filter is the Svbony 7nm Ha/Oiii filter, super cheap, and people are having great results so far. If didn't already have the D1, I would probably get that one to pair with the D2 instead for the $100 price difference.

Edited by j21blackjack, 26 January 2023 - 11:24 AM.