L-Ultimate Star halos Optolong L-Ultimate 2" · Doversole83 · ... · 12 · 976 · 10

Hello,

I don't own the L-Ultimate, but I had for a short time the L-Extreme, which has a similar rendering concerning the stars halos.
Those filters are not good with fast apertures. So I chose the IDAS NBZ. It has better coatings and there are almost no halo (but it's 10 nm).
Look at the picture, a 2 frames mosaic taken with Samyang 135, ASI533 and IDAS NBZ.
You may also have a look at Antlia ALP-T duo, there is a version for fast aperture, and it's 5 nm.

Dear Astrobin community,

I have recently bought an L-Ultimate dual band filter which I just tried using a Samysang 135 (at f/2) and an ASI071MC color camera. This gives a very wide field around 11deg by 7deg.
This is the first image, centered around the Crescent Nebula. 300s subframes, 13 of them taken between the clouds!
I like the contrast but I not so much the star halos, in particular around red stars!

I need your view on this particular issue of star halos. What do you think?
- This filter has an issue. I should send it back and ask for a new one
- This is a known issue, I should use an Antlia filter instead
- This is linked to the very fast system. Just live with it!

Thanks for your views!
Cheers and clear skies!

Hi Doversole83,

Great images! Unfortunately it seems that star halos are a common problem with Optolong filters. I have the L-eNhance and L-eXtreme, both of which produce halos around stars when I use either of them with my Radian 61.

I do agree with David's response about halos being caused by fast imaging systems, especially equipment that has f/2, which many duoband filters aren't good at emitting their full bandpasses due to band shift. There are definitely filters that are available and designed specifically for fast imaging systems, such as the IDAS NBZ or L-eXtreme f/2, although the L-eXtreme f/2 still produces halos, even Antlia's ALP-T f/2 filter produces halos whereas the normal ALP-T produces minimal to no halos from my observations. I found that out by watching Cuiv the Lazy Geek's and Lukomatico's reviews on it. In regards to the L-Ultimate, it can produce halos but from a few different reviews of the filter I have watched on YouTube, some people didn't experience halos whereas others did.

I wouldn't send the L-Ultimate back due to this. I would keep it as a backup in case you are in heavily light polluted skies and are imaging emission nebulae. If the halos are annoying you, I would try removing them in post-processing if you can. If you have the latest version of Photoshop, the new remove tool is amazing. I've used it with great success on my images plagued with halos. I've found the best results are achieved when the stars are taken out of the image, using something such as StarNet2 or StarXTerminator. I then carefully go around the area where the halo was and then see if anything else needs to be cleaned up, but most of the time I try not to do too much as I like maintaining the accuracy of what I shot.

If they are still annoying you, you could perhaps look at the Antlia ALP-T. It has 2nm less bandpass than the L-Ultimate, but it is very good for controlling star halos. I'm not trying to suggest that you go out and buy this filter, but it is another option if you feel that the halos are too much.

Ultimately, it's down to personal preference. I personally would like to try both the Antlia ALP-T and Optolong L-Ultimate one day, as both filters are very capable of producing excellent results. In fact, I loved my Optolong L-eNhance so much that I only just started using my L-eXtreme last week which had been sitting in my containers until then, and the difference between the two filters was mindblowing. The L-eXtreme has much more contrast than the L-eNhance!

Hope this helps.

Zak

Thanks for your answers. I will try the filter with the Redcat51 which is f/4.9.

All good! Happy to help.

Looking forward to seeing how it goes!

Zak

For information, I did a trial at f2. 8, same result. 
At f4 there are no more halos. 
Below an image of 21x300s centered on America. 

Awesome image!

Glad to hear that the halos are gone at f/4. Bummer that they are still there at f/2.8 though, but at least you know now that anything lower than f/4 can cause halos for your setup. Have you managed to try the L-Ultimate with your RedCat 51? It should help further in preventing halos due to it's slower f-stop.

I have halos on my L-eXtreme at f/4.5 with my Radian 61, but that's ok though for me as I just remove them with Photoshop once the images are starless. The L-eXtreme is known for halos unfortunately, but that's not stopping me from using it. It's way better than the L-eNhance that I am used to using.

Really thinking about potentially getting either the Antlia ALP-T or Optolong L-Ultimate in the near future as well. They are both exceptional filters for what they do!

Zak

Hi, 

I am no expert here but the the Optolong website does not recommend Lultimate filter with with fast ratio systems. The recommended F-ratio is F/4 or higher. I have been using Lultimate for last couple of months with a F/6 scope. The halos are definitely there but around very bright stars only and its quite faint - with some processing I am sure one can make it go away. With a faster system perhaps the bigger issue would be bandpass shift than halos around the star. The filter will not perform optimally with a faster system. I have not tried in any other scope but while researching for the filter this seem to be the most common opinion floating around. Hope it helps.

CS!

Optolong L-extreme (L-ultimate doesn't seem to be any better) is a filter that should have never been offered for sale, or made it past R&D.     I owned one for an entire 2 weeks before I sold it for the exact reasons you mention above.   It's not a good filter.  Also, I still had halos even at F/7.    ALP-T I've heard only good things about, but no experience personally.   Narrowband imaging on an OSC is highly inefficient, so I went to mono afterwards and never looked back.