Filters using a OSC camera

[bomberbaz]

Hello all.

I currently use this ZWO dual band  Filter when imaging nebula and the details can be found at the link. This has a fairly high bandwidth of 15nm in HA and stated transmission of "over" 80%. I don't like this because this could vary from 80.01 to 89.99, a considerable difference but that's another story.

I was wondering if adding more data to an hydrogen rich image using a tighter bandwidth filter is worthwhile consideration with the OSC camera (It's the ZWO 183 MC Pro ) ZWO 1.25" Ha 7nm Narrowband Filter | First Light Optics

Has anyone tried this and had any success ?

cheers

steve

[Lee_P]

Tighter bandwidths do make a difference. See my review of some dualband filters here for examples. The Optolong L-Ultimate is possibly the best available right now (Ha / OIII dualband, 3nm) but it's 2" only and expensive!

[vlaiv]

48 minutes ago, bomberbaz said:

. I don't like this because this could vary from 80.01 to 89.99, a considerable difference but that's another story.

Depending on conditions of the night that you don't control difference of 9.99% in light transmission is small. You can get up to 40-50% loss of light depending on how and when you choose to image a target - and most people don't ever consider this.

49 minutes ago, bomberbaz said:

I was wondering if adding more data to an hydrogen rich image using a tighter bandwidth filter is worthwhile consideration with the OSC camera (It's the ZWO 183 MC Pro ) ZWO 1.25" Ha 7nm Narrowband Filter | First Light Optics

Same principle applies to OSC as does to Mono when comparing two filters with different bandwidth.

Both will let same signal pass (with differences to a few percent in transmission). Where they differ is amount of other light that they will pass. This is value of NB filter - in cutting off unwanted light. Tighter the bandwidth - less unwanted light is passed. This is especially important in light polluted scenarios, or when you want to separate close lines - like Ha and SII (656nm and 672 - so gap between is about 16nm and filters like Ha with 30nm bandwidth might not separate the two - depending on CWL).

[bomberbaz]

6 hours ago, Lee_P said:

Tighter bandwidths do make a difference. See my review of some dualband filters here for examples. The Optolong L-Ultimate is possibly the best available right now (Ha / OIII dualband, 3nm) but it's 2" only and expensive!

Great review Lee. If I had a bottomless wallet it would be the L-ultimate, shame they don't do a 1.25"! 

However the Askar dual band is a compelling buy at that price and performance. 

Thanks for bringing it to my attention.

Steve

[Elp]

What's wrong with the L-Extreme?

[Lee_P]

1 hour ago, Elp said:

What's wrong with the L-Extreme?

L-eXtreme is a solid choice, and the OP should be able to find a second-hand one for a good price. The catch is that it does feel a bit "last generation" compared to new models like the L-Ultimate (which, to be fair, it is!) Specifically, the L-eXtreme gives halos around bright stars, and is 7nm. Excellent results are still possible of course. I used an L-eXtreme extensively before the L-Ultimate came out. 

[licho52]

I think it's worth doing and I have done with some star fields in the galaxy disk like Cas.  It's a very clean Ha signal without the O-window, especially with light pollution and/or moon.   First I'd look in classifieds where 1.25 Ha filters may pop up for a much friendlier price.

[900SL]

Antlia ALP-T is working for me, and it seems to be an accurate bandpass.

[iantaylor2uk]

I like the L-Enhance filter for my OSC - it doesn't have as much of a halo problem around bright stars that the L-Ultimate has.  

[bomberbaz]

For anyone interested I eventually went for the askar, the price and shootout results made it a compelling buy. If they ever bring out a 1.25 ultimate, I would be tempted.