Best filter for imaging narrowband with the ASI 552MM Pro.

[wavydavy]

What do you consider the best filter for imaging narrowband mainly h-alpha, I currently am using a Baader 7nm 1.25"................is there anything better, make/quality etc. The camera is an ASI 553MM Pro.

[Adam J]

On 26/09/2023 at 15:25, wavydavy said:

What do you consider the best filter for imaging narrowband mainly h-alpha, I currently am using a Baader 7nm 1.25"................is there anything better, make/quality etc. The camera is an ASI 553MM Pro.

Well that is a can of worms, you are opening. 

Firstly the Baader 7nm is by no means a bad filter, it was the goto starter narrow band filter set for a long long time an for good reasons. On the Ha at least I never really found that you had much in the way of reflections. 

So what are you going to gain? Well you will gain some signal to noise by going narrower potentially most so if you go with a 3nm filter. 

However, you will also lose something in going for a 3nm filter and the thing you will loose is NII. What will that mean, well in my opinion it means less definition in quite a large number of targets and not just SNR.  For this reason I tend to think that for Ha at least the optimal band pass is about 5nm and not 3nm. 

I have never felt a need to upgrade from my 5nm Astrodon filters, for me they are perfect. For a 533m you can use 1.25, 31mm or 36mm filters. The first two will cover a IMX492 sized sensor in the future to about F4 / F3 respectively and the 36mm will cover a IMX571 sized APSC sensor. So think about your upgrade path, better not to have to buy twice. 

The best filters are still made by Chroma and Astrodon, that is still what you yet if money is no object. 

But if you are only using a small IMX533 base senor i am going to guess that money is a consideration. 

 

Top tip: By the time you are spending more on your filters than you spent on your camera you are doing it wrong in my opinion. 

 

1) Do you have a filter wheel? 

2) Do you already have OIII and SII filters to go with the 7nm Ha?

3) What scope / scopes are you using? You may or may not need pre-shifted filters. 

 

 

Adam