Choosing SHO filters for RASA 8

Topic starter

Mar 13, 2025 · Edited: Mar 13, 2025

I bought RASA 8 recently and I'm still thinking what is the best choice for monochrome narrowband filter to me - if the budget is limited as mine excluding Astrodon and Chroma options.

So I think that my options are Baader F2-ultra-highspeed (3.5nm-4nm) or Astronomik MaxFR 6nm SHO-filters. But which one of these is the best filter for RASA 8 and just now? I have read some bad experiences of Baader F2-filters, but I have also read that some quality problems are fixed and the later series are better than older series. There are less quality issues regarding Astronmik MaxFR filters, but these have wider bandpass, optimization range is not just F/2 but wider, and worst of all, these are much more expensive than Baader alternative. There are also older topics of F2-filters, but now I am concentrated on new experiences of these filters because of recent quality improvements regardig Baader. I specifically want experiences with these filters on RASA telescopes, as an F/3 aperture ratio is already quite different from F/2. How well do the filters transmit emission regions (SNR?) and do they produce halos?

And the prices: Baader F/2 Ultra-Highspeed filter 3.5-4nm 2" SHO-set costs 1100 euros and Astronomik 6nm MaxFR 2" SHO-set 2037 euros, so Astronomik is double expensive than Baader.

I use these filters under bortle 3 sky, but of course narrower bandpass is still better. I use these filters with Baader UFC filter drawer and prefer 2" version.

Thank you for help!

Josh Jones

Mar 13, 2025

I've used all of these pretty extensively, from the older baader f/2 to the newer version f/2 narrow 3.5 filters and now the astronomik MaxFR 6nm on RASA 8 and RASA 11's and I saw significant improvement especially in the blue halo with the MaxFR. I'm in a bortle 3-4 region as well.

this might be a good example: https://app.astrobin.com/u/astrospaceguide?i=k88fi9 still show halos, but much more managable when I process.
smaller stars show no signs of halos to me: https://app.astrobin.com/u/astrospaceguide?i=3dxsif

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Rodrigo Roesch

Mar 13, 2025 · Edited: Mar 13, 2025

I have the 36mm Astronomik max FR. They work pretty well with the RASA 8. I just mount them in the 36mm-2" ring adapter so they fit into the filter drawer.
Here is an example
https://astrob.in/n13o69/D/

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Bob Dalton

Mar 13, 2025

I dont have a RASA, rather the Hyperstar on my C11 Edge HD. I've been using the Optolong 3nm which aren't really designed for fast optics but that being said, only the Oiii produces halos, my Sii and Ha have none.

I too am in the search for a affordable set that would make the halos minimal so I reached out to Starizona and they recommended the Baader 3.5 / 4nm f/2 Ultra-Highspeed-Filter-Set for Bortal 4 and above skies, but helps in better skies on nights with a moon. Whereby the Baader 6.5nm f/2 Highspeed Filter Set – CMOS-optimized (H-alpha, O-III, S-II) would probably do just as well and cost much less (almost half), I am a little skeptical of the higher bandpass.

Funny part is, I also had a set of 36mm Baader back in 2021 that were absolutely the worst, my Sii, back then, was so bad I threw it in the trash.

I probably will purchase the Baader and try my luck since my budget is much like yours and I cannot see spending 2k for a set of Astronomik when their Oiii looks to produce just as large of Halos as my Optolong.

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Rodrigo Roesch

Mar 13, 2025

You can buy the 36mm instead of the 2" to reduce cost

Bob Dalton

Mar 13, 2025

Rodrigo Roesch:
You can buy the 36mm instead of the 2" to reduce cost

Thanks, unfortunately I have a full Frame sensor.

Bob Dalton

Mar 13, 2025

Astronomik MaxFR 6nm SHO-filters 2

Here is an example of the MaxFR 6nm, for the money, still a lot of Halo's

https://www.astrobin.com/vl00ov/0/

Rodrigo Roesch

Mar 13, 2025

Bob Dalton:
Astronomik MaxFR 6nm SHO-filters 2

Here is an example of the MaxFR 6nm, for the money, still a lot of Halo's

https://www.astrobin.com/vl00ov/0/

Well if you read the description, that picture was not taken with the Astronomik MaxFR. It was taken with the regular Astronomik 6nm filter. they exchanged my set of filters with the Max RF

Bob Dalton

Mar 13, 2025

Well if you read the description, that picture was not taken with the Astronomik MaxFR. It was taken with the regular Astronomik 6nm filter. they exchanged my set of filters with the Max RF

yes, you are correct. Sorry, ,my oversight. I still believe that Halos are troublesome with all the filters that I have looked at, some larger, some smaller. It is a difficult decision to make and with manufacturers inconsistencies, even harder.

Sometimes I just think it is better to keep them cheap and remove the Halos in post. 😂

Rodrigo Roesch

Mar 13, 2025

I find the OIII is the most problematic, I actually discussed that with Astronomik and they exchanged for a better one. They claimed the new coating of their OIII reduces halos, however, it still has some in the bright stars.

I would say that the dual band Antlia has better halo management, but not sure if that is a fair comparison because I use it in longer FL telescopes. The RASA tends to be very susceptible.

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Ryan Génier

Mar 13, 2025

I use a RASA8 with the Baader ultra-highspeed SHO filters. They work great! Check out my profile.

The only filter I have halos on are the Sii. I reached out to the local supplier and said it's an issue, they are going to replace mine. So support has been great.

Bob Dalton

Mar 13, 2025

Bob Dalton:
Well if you read the description, that picture was not taken with the Astronomik MaxFR. It was taken with the regular Astronomik 6nm filter. they exchanged my set of filters with the Max RF

yes, you are correct. Sorry, ,my oversight. I still believe that Halos are troublesome with all the filters that I have looked at, some larger, some smaller. It is a difficult decision to make and with manufacturers inconsistencies, even harder.

Sometimes I just think it is better to keep them cheap and remove the Halos in post. 😂

Some differences in post, I used Optolong SHO 3nm on my Squid, and look at the difference between these two,
One using the Max RF
https://cdn.astrobin.com/thumbs/By6h3Y5Mshx1_16536x0_b9muqi8S.jpg
and mine
https://cdn.astrobin.com/thumbs/aOLWuH4QRxo8_2560x0_esdlMP5Y.jpg

I just dumped the Halo from the Oiii with Pixinsight first before combining images

Bob Dalton

Mar 13, 2025

Ryan Génier:
I use a RASA8 with the Baader ultra-highspeed SHO filters. They work great! Check out my profile.

The only filter I have halos on are the Sii. I reached out to the local supplier and said it's an issue, they are going to replace mine. So support has been great.

The Soul nebula looks great, what kind of skies are you under?

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Rodrigo Roesch

Mar 13, 2025 · Edited: Mar 14, 2025

Ryan Génier

Mar 14, 2025

Bob Dalton:
Ryan Génier:
I use a RASA8 with the Baader ultra-highspeed SHO filters. They work great! Check out my profile.

The only filter I have halos on are the Sii. I reached out to the local supplier and said it's an issue, they are going to replace mine. So support has been great.

The Soul nebula looks great, what kind of skies are you under?

Thanks! I shoot almost all my images from my backyard which is B7

Tommi Liinalampi

Topic starter

Mar 14, 2025

Thank you all for the great comments. It was great to get information about your experiences. The choice is not very easy, as the price difference is significant, but on the other hand, the quality might be better with Astronomik. Based on the images, the results with Baader filters have also been quite impressive. I am now seriously considering that if I go with Astronomik, I might opt for smaller filters than the 2" mounted ones. At least 36 mm filters would be quite sufficient for me.

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Which one of SHO-sets would you buy right now for RASA 8?