Filters for f2

Any recommendations for filters for fast setups? F2 -f2.8?

https://www.baader-planetarium.com/en/baader-3.5--4nm--f2-ultra-highspeed-filter-set-%E2%80%93-cmos-optimized-(h-alpha--o-iii--s-ii).html

This is about all I can think of. For RGB it does not matter at all. I use them on a RASA and Roki 135 and they do a good job.

Astronomik and their max fr series.
you can even talk to them and they will select you filters for your specific f-ratio.

ps.
i don’t and have never owned a max fr filter. Only know it from their website

Astronimik maxFR… they are reeeaally worth it. I got a set of hso 6nm in 50x50, but my results are waay better than my badder hso in 3.5nm. Running a rasa 11 and 6200mm. They are very good to talk with as well.

Antlia Triband RGB Ultra
Idas NBZ UHS
Optolong l pro works
as does Optolong L Ultimate

If your talking about camera lens, can't help. As for scopes, I used Astrodon 6nm on a Tak E-180 f2.8 with no issues.
When Astrodon came out with the 5nm and 3nm filters, I jumped on the 3nm and used them on a Tak E-210 f3, again with no issues.

I have used my ZWO dual band filter (basically a cheaper / wider version of l-enhance) with some Samyang and Sigma lenses at f/2 and it worked fine. Most of the loss is likely in the Ha signal and there is typically more than enough of that anyway. Also afaik people use l-enhance on RASA but I'm yet to try that.

Think most "fast" dual band filters are just somewhat wider to allow for the shifted light to pass. Optolong were supposed to release an f2 version of an l-extreme and there's a number of reviews online but don't think it is available yet?

I also recommend the Baader Ultra High Speed F2 3.5/4nm narrowband filter set.
They work excellent with my HD 11/Hyperstar @ F1.9 setup.

As others wrote, recent Baader filters are a good choice, when you have an OSC the the Antlia ALP-T Highspeed also works well.

Samyang 135 @f2.4 with l-extreme

https://www.astrobin.com/4y9la8/
https://www.astrobin.com/tqwamc/
https://www.astrobin.com/zxuaxu/C/

no issue with this lense and tbis filter, at least for my standards

I also recommend the Baader Ultra High Speed F2 3.5/4nm narrowband filter set.
They work excellent with my HD 11/Hyperstar @ F1.9 setup.

+1
Baader Ultra High Speed F2 3.5/4nm is a great device.

Bob Lockwood:
When Astrodon came out with the 5nm and 3nm filters, I jumped on the 3nm and used them on a Tak E-210 f3, again with no issues.

Generally, the issue you would face with this scenario is spectral shift in HA where the had band gets shifted by the fast f-ratio and pushed outside the bandpass of your filter. This would show up as reduced efficiency and not an observable artifact. Thats why wider bandpass filters are recommended for fast f-ratio scopes or a filter in which the passthrough has been shifted to accommodate the spectral shift.

To the OP, I would recommend the Astronomik Deep Sky and Astronomik MaxFR 6nm series filters. I'm using with epsilon at f3.3 and have been very happy. No halos, or other artifacts.

Don't know about others experience with dual NB filters and fast lenses, but I was ready to get almost nothing from the samyang 135 @f2/2.4/2.8 but the true is the opposite.

Could be, maybe, the shift related to the lenght of the light path? The angle of impact through the lenses is different from those generated into longer scopes?

F. Londe:
I recommend Idas NBZ UHS (HyperStar 9.25 v4 HS4-C925) @Bortle 8 location,

https://www.astrobin.com/xuxz7t/
https://www.astrobin.com/625sqw/
https://www.astrobin.com/wdsy5g/

I'm going to buy that one for my hyperstar 8 setup.
Never ending spending

Could be, maybe, the shift related to the lenght of the light path? The angle of impact through the lenses is different from those generated into longer scopes?

I really dont know the physics here, but it is my understanding that spectral shift is entirely dependent on f-ratio only. (Please correct me if I am wrong). Most of the dual band filters have a wider bandpass so there are minimal issues due to spectral shift even with very fast scopes. Also another thing to consider, is that if you lose 30% of the transmission due to spectral shift, a very fast scope may be 300 or 400% more efficient to begin with (assuming FL is the same and only aperture increases). So losing 30% might not be noticed.

It's complicated but in simple terms it depends on the cosine of the incidence angle, thus depends linearly with the f/ratio. Note that not only this results in a shift to shorter wavelength but also in a reduction in transmission.

Astronomik max fr - work fine with my RASA11 and Hypergraph 6. IDAS-NBZ-UHS are supposed to work at f/2.2 as well but I can see some discoloration in the corners at full field.

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