Oiii filters without halos?

[paul]

I'm currently using the 36mm ZWO Oiii filter but it suffers from strong halos on bright stars that are difficult to process out. Does anyone have practical experience of (preferably lowish cost) alternatives? The filter will be mainly used on F4.8 gear though I plan to do some wide-field F2 imaging soon. I was looking at the latest fast Baader but I've seen recent reports of quality control issues. I refocus between filters so I am not concerned about it being parfocal with the others.

[ApophisAstros]

Took this sub 3 days ago. 600s Oiii

This is calibrated and Integrated in Pixinsight. 7 x 600s Oiii

Scope Redcat51 F4.9 250mm with Atik460ex CCD.

 Got mine from here . 

"Baader 3.5nm Ultra Narrow Band OIII Filter - CMOS Optimised" Choose: 1.25" 3.5nm OIII Filter Price: £215.00

 

from FLO.

Hope this helps,

Roger

Edited October 24, 2021 by ApophisAstros

[paul]

11 hours ago, ApophisAstros said:

Took this sub 3 days ago. 600s Oiii

This is calibrated and Integrated in Pixinsight. 7 x 600s Oiii

Scope Redcat51 F4.9 250mm with Atik460ex CCD.

 Got mine from here . 

"Baader 3.5nm Ultra Narrow Band OIII Filter - CMOS Optimised" Choose: 1.25" 3.5nm OIII Filter Price: £215.00

 

from FLO.

Hope this helps,

Roger

Thanks Roger, it is reassurring to see the result👍. It's easy to find problems with filters on the net. It's more difficult to find reports where people say it just works. 

[TerryMcK]

I’ve just bought a set of Baader Ultra Narrowband filters but not tried them out yet due to weather conditions. The filters are flawless in construction but obviously can’t comment on them for usage yet.

The O3 filters and S2 filters are actually 4nm band width rather than 3.5nm quoted on many websites. It’s the Ha filter that is 3.5nm.

 

[Wyvern]

To add another contender into the ring, the Antlia 3nm.

 

Found an interesting comparison with the 3.5nm versions which I have.

 

Antlia 3nm PRO Oiii Narrowband filter comparison

 

They use some really bright stars in the review so you can really see how good they are. Although there will always be differences between filters, some will be better, some worse.

Edited October 26, 2021 by Wyvern

[TerryMcK]

1 hour ago, Wyvern said:

To add another contender into the ring, the Antlia 3nm.

 

Found an interesting comparison with the 3.5nm versions which I have.

 

Antlia 3nm PRO Oiii Narrowband filter comparison

 

They use some really bright stars in the review so you can really see how good they are. Although there will always be differences between filters, some will be better, some worse.

Very interesting comparisons. You wouldn't have thought there would have been that much difference with .5nm bandwidth but it was clear to see in Ethan's review/test. I wonder what connection he is to Antlia, maybe he is one of their trusted reviewers and was loaned the filters, or if he just bought the filters himself to try out.

[Wyvern]

40 minutes ago, TerryMcK said:

Very interesting comparisons. You wouldn't have thought there would have been that much difference with .5nm bandwidth but it was clear to see in Ethan's review/test. I wonder what connection he is to Antlia, maybe he is one of their trusted reviewers and was loaned the filters, or if he just bought the filters himself to try out.

 

At the bottom of the review it states that he was given the opportunity to review. Not sure if that means loan or gift. Not sure of his relationship with them either.

[paul]

Thanks for all for your great inputs, Baader filters look the overall best option for my budget but the test report was particularly seductive and the Antlia is in stock too. I very nearly pulled the trigger on that one. 

 

I also checked out the first gen Askar filter that had good in-band transmission performance on paper but doesn't seem to have any anti-reflective finish - I suspect the next gen will have. Apart from transmission not a big change from ZWO. Optolong I dismissed as it had the lowest transmission (80%) and some poor reviews.

 

Uncharacteristically (I'm having a moment😀), I've decided that economics over spec wins at this stage. I'm trying out the new Baader 6.5nm (from FLO)  - it should bring Oiii halo performance in line with ZWO Ha. The slightly higher transmission (<>+10%)  of the Baader, and 6.5 vs 7nm of the ZWO gives a useful reduction in unwanted light (<>-10%) for overall better SNR. The new coatings should also reduce the general scatter for better contrast. All on paper at least!

 

It should arrive this week but the weather is looking bad until Monday (its always next week 😉). I'm keen to get more subs on the Wizard so I should be able to do a side by side comparison on the same night.

 

I have LP but it isn't as severe as for some and the RGB/NB results I'm getting are already several magnitudes better than my old DSLR of course. At the moment I haven't convinced myself that the bandwidth is holding me back. I do understand 4-3nm will give better contrast and maybe tighter stars so a full set is definitely on the the wish list for next year. By then hopefully the stock situation will be back to more normal.