Bortle 7 filter question, Antlia ALP T

[900SL]

Hi

 

Am I likely to see a big difference in overall exposure time, contrast and noise between a IDAS NBZ duoband (10 nm) and an Antlia ALP T (5 nm)?  I understand Oiii is generally improved at tighter bandpasses?

My imaging location is either Bortle 7 or Bortle 4.

I currently have the IDAS NBZ. Clear nights are few and far between here at the moment so if the Antlia would make a significant difference I might switch, otherwise I'll stick with the NBZ which seems to work well for Ha and Oiii

 

[900SL]

I'm slowly talking myself around to a Mono set up, 533MM Pro, 1.25" Antlia Edge HSO 4.5nm, AsI manual 5* filter wheel

[ollypenrice]

An interesting thing about bandpass is that broader does not seem to be faster. My Astrodon 3nm Ha gives a better result in the time than my 7nm Baader. This may be down to its better transmission but not necessarily. In principle a luminance or a red filter passes the same amount of Ha as an Ha filter. The Ha's advantage lies not in what it passes but in what it blocks. A tight bandpass may block more of what you don't want.

Olly

[900SL]

On 02/02/2023 at 11:06, ollypenrice said:

An interesting thing about bandpass is that broader does not seem to be faster. My Astrodon 3nm Ha gives a better result in the time than my 7nm Baader. This may be down to its better transmission but not necessarily. In principle a luminance or a red filter passes the same amount of Ha as an Ha filter. The Ha's advantage lies not in what it passes but in what it blocks. A tight bandpass may block more of what you don't want.

Olly

Thanks Ollie. I found a formula for the improvement in S/N and going from a 10nm NBZ to a 5nm Askar should give me a 1.4 X improvement. Now ordered