Stuart Taylor:
I'd not thought of using a Sii filter separately to add the rest of the emission. This is a good idea and I plan to try it.
My question is, how should I choose which width of Sii filter to use? I guess the broader the bandpass the less it needs to be 100% accurate on the centre of the frequency?
the 6nm seems to be almost twice the price of the 12nm, so I am wondering if there is a big difference between the two to justify this?
Light pollution around 672nm seems quite insignificant, so I assume a very narrow bandpass isn't really essential?
Stuart Taylor:
I'd not thought of using a Sii filter separately to add the rest of the emission. This is a good idea and I plan to try it.
My question is, how should I choose which width of Sii filter to use? I guess the broader the bandpass the less it needs to be 100% accurate on the centre of the frequency?
the 6nm seems to be almost twice the price of the 12nm, so I am wondering if there is a big difference between the two to justify this?
Light pollution around 672nm seems quite insignificant, so I assume a very narrow bandpass isn't really essential?
Actually with an OSC you may consider the IDAS NB3 Dualband filter. So you can capture H+O in one session with an H/O Dualband like the L-Extreme/L-Enhance/L-Ultimate and S+O in another session. Since OIII is usually fainter than Ha but an important part of the image , getting additional OIII signal while collecting SII may be nice.
Clear skies
Wolfgang
Rodrigo:Stuart Taylor:
I'd not thought of using a Sii filter separately to add the rest of the emission. This is a good idea and I plan to try it.
My question is, how should I choose which width of Sii filter to use? I guess the broader the bandpass the less it needs to be 100% accurate on the centre of the frequency?
the 6nm seems to be almost twice the price of the 12nm, so I am wondering if there is a big difference between the two to justify this?
Light pollution around 672nm seems quite insignificant, so I assume a very narrow bandpass isn't really essential?
Actually with an OSC you may consider the IDAS NB3 Dualband filter. So you can capture H+O in one session with an H/O Dualband like the L-Extreme/L-Enhance/L-Ultimate and S+O in another session. Since OIII is usually fainter than Ha but an important part of the image , getting additional OIII signal while collecting SII may be nice.
Clear skies
Wolfgang
Is there a dual band O3+SII?
Stuart Taylor:
I'd not thought of using a Sii filter separately to add the rest of the emission. This is a good idea and I plan to try it.
My question is, how should I choose which width of Sii filter to use? I guess the broader the bandpass the less it needs to be 100% accurate on the centre of the frequency?
the 6nm seems to be almost twice the price of the 12nm, so I am wondering if there is a big difference between the two to justify this?
Light pollution around 672nm seems quite insignificant, so I assume a very narrow bandpass isn't really essential?
for ASI2600MC (RGGB)
https://astronomy-imaging-camera.com/product/asi2600mc-pro-color
OIII (500nm) B relative QE = 50%, 1/4 area
OIII (500nm) G relative QE = 90%, 2/4 area
total OIII effectiveness = 0.5*0.25 + 0.9*0.5 = 58%
Ha effectiveness = 80%, 1/4 area = 20%
So when I image 60 minutes with dual narrow + 2600MC,
OIII = 60x58% = 35 minutes with 2600MM
Ha = 60x20% = 12 minutes with 2600MM
-> OIII is about 3 times more than Ha
OSC + dual narrow will work for "faint OIII" nebula like Sh2-129 and OU4 (Flying Bat and Squid), North America and Pelican, ...
but not effective as Mono for "faint Ha" nebula like Sh2-240, outer shell of Veil, etc
Stuart Taylor:
I'd not thought of using a Sii filter separately to add the rest of the emission. This is a good idea and I plan to try it.
My question is, how should I choose which width of Sii filter to use? I guess the broader the bandpass the less it needs to be 100% accurate on the centre of the frequency?
the 6nm seems to be almost twice the price of the 12nm, so I am wondering if there is a big difference between the two to justify this?
Light pollution around 672nm seems quite insignificant, so I assume a very narrow bandpass isn't really essential?
Is there a dual band O3+SII?
Yes, the IDAS NB3 Dualband filter.
Roger Nichol:Is there a dual band O3+SII?
Yes, the IDAS NB3 Dualband filter.
I have the IDAS NB3 filter and have used it effectively. I would hesitate to recommend it though as it has a wide bandwidth around the Oiii and Sii. I find that when combining the Oiii from the NB3 with Oiii from an L-eXtreme or Antlia ALP-T, it degrades the result, so I discard it. It would be better to use a 3nm Sii filter, e.g. from Antlia.
Some examples using the NB3 filter are at: https://www.astrobin.com/0z1g7d/ ,
This one has the stack from just that filter to compare with the stack from the L-eXtreme: https://www.astrobin.com/tv44gx/E/ The original is L-eXtreme, Rev B is NB3, Rev C is combined
Dale Penkala:
I totally agree NB with OSC is very doable and I’ve been very happy with my results. I used my NBZ filter for quite sometime but moved to the Antlia ALP-T. Below is a couple examples of what I’ve been happy with if your interested. I did a comparison of both filters and if your interested it is here: https://www.astrobin.com/uz2syz/E/
I was not aware of the filter for Oiii and Sii so I’m glad I stumbled on this thread! When I process for SHO or HSO I create a synthetic Sii and use it. It may not be the “correct” way or most “accurate” representation of the channel but I’ve been quite happy with the results. I have used several different methods to do this but here is a link to my “basic” approach. https://www.youtube.com/watch?v=QV6ObLVRvNk
You may have even used it yourself.
Ghost: https://www.astrobin.com/blrfbi/E/
M76: https://www.astrobin.com/k0zbvd/D/
Soap Bubble: https://www.astrobin.com/rkulit/P/
Ring/M57: https://www.astrobin.com/bkyont/E/
Agree with @Rodrigo I was very surprised at how much of the shell was captured. It does take integration time for sure though.
Dale