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ASI 294mc...Triband or Ha and SIII separately

Rattler

By Rattler
in Discussions - Cameras

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Rattler

Rattler

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Hi guys. I have a Zwo ASI 294mc on its way. I already have 1.25" Ha and SIII filters which I could use with it but then of course there is the Altair Triband and Quadband filters. In a way I'm leaning more towards the combined filters as I feel that individual may take away some of the ease with a OSC camera. I'd also maybe use one of the TS filter holders for ease of swapping filters between the combined filter and the LP filter without disturbing orientation.

Any thoughts please?

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Adam J

Adam J

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1 hour ago, Rattler said:

Hi guys. I have a Zwo ASI 294mc on its way. I already have 1.25" Ha and SIII filters which I could use with it but then of course there is the Altair Triband and Quadband filters. In a way I'm leaning more towards the combined filters as I feel that individual may take away some of the ease with a OSC camera. I'd also maybe use one of the TS filter holders for ease of swapping filters between the combined filter and the LP filter without disturbing orientation.

Any thoughts please?

I think that the quad band is pointless as you cant separate out the SII from the Ha using the red pixels and the difference between the placement of SII and Ha in most cases are not pronounced. I.e for the most part SII looks like dimmer Ha signal.

In the same way Hb is dimmer Ha signal so only really adds color balance at the expense of contrast.

So in essence: get Duel band (OIII + HA), if thats not possible get tri-band (Ha+Hb+OIII), if thats not possible get quad band (Ha +Hb + OIII + SII)...

I would not be using separate filters with OSC following the advent of these new designs, at least not unless i was trying to image from central London...then I would be using AD 3nm filters.

Adam

 

 

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Rattler

Rattler

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4 minutes ago, Adam J said:

I think that the quad band is pointless as you cant separate out the SII from the Ha using the red pixels and the difference between the placement of SII and Ha in most cases are not pronounced. I.e for the most part SII looks like dimmer Ha signal.

In the same way Hb is dimmer Ha signal so only really adds color balance at the expense of contrast.

So in essence: get Duel band (OIII + HA), if thats not possible get tri-band (Ha+Hb+OIII), if thats not possible get quad band (Ha +Hb + OIII + SII)...

I would not be using separate filters with OSC following the advent of these new designs, at least not unless i was trying to image from central London...then I would be using AD 3nm filters.

Adam

 

 

Thanks for that mate. Makes sense. Does anyone make a dual band?

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IDAS NB1 filter a Tri-Band ís also an option, https://www.firstlightoptics.com/light-pollution-reduction/idas-narrow-band-nebula-nb1-filter.html                                                                                                                                                 Or see also IDAS Narrow-Band Nebula (NB2) https://www.firstlightoptics.com/light-pollution-reduction/idas-narrow-band-nebula-nb2-filter.html

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Adam J

Adam J

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13 minutes ago, Rattler said:

Thanks. £100 more expensive than Altair's Triband though.

yes but altairs filter is 32nm wide at oiii and thats the most important band for light pollution. STC filter is 10nm i believe. Thats a massive three fold advantage to STC.

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Adam J

Adam J

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29 minutes ago, Rattler said:

Interesting. So I can image with the combined filter to give the Ha and OIII and also image with a LP filter such as the Skytech Lpro for RGB and combine the 2?

yes, but to be honest i dont see why you would want to do that, just separate the channels and process separately to gain a bi-color image from the STC for emission nebula and for galaxies or reflection nebula use the Lpro, I would not use the L-pro for nebula unless its just to add some RGB stars only.

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Adam J

Adam J

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2 hours ago, Rattler said:

Ok so it would be different to creating say a HaRGB image for example?

If you want to do HaRGB then get a Ha filter and a Lpro. The Duel band filter is for making bi-color images in narrowband.

So with HaRGB you are using the Ha as a luminance layer and then getting color from the L-pro.

With the Duel channel filter you will be able to split the channels, assign the Green and Blue channels back to Blue only and Keep the red seperate. Then re-combine to get a Blue + Red image, lastly you generate a synthetic green channel.

In essence that will give you something that looks like all the veil nebula bi-color images that you see taken by mono cameras.

Adam

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Rattler

Rattler

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It's been mentioned to me that narrower bandwidth is not necessarily a good thing with a colour camera as you are gathering less photons. I know that narrower prevents wavelengths of light pollution etc. Would it require longer integration time for narrower bandwidth?

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Adam J

Adam J

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3 hours ago, Rattler said:

It's been mentioned to me that narrower bandwidth is not necessarily a good thing with a colour camera as you are gathering less photons. I know that narrower prevents wavelengths of light pollution etc. Would it require longer integration time for narrower bandwidth?

No that's not true at all. All the photons from emission Nebula are contained within emission lines and as such a narrower the filter the better irrespective of if its OSC or mono. The filter will always let all the nebula light through but will block increasing amounts of broad band light as it gets narrower, that includes both light pollution and star light so smaller stars are a secondary bonus. But for this reason you would not use a narrow band filter for galaxy imaging, unless its to image Ha regions within a galaxy and add them to a broad band image.  

The only slight gocha used to be with older DSLRs, they would have a hard time focusing / finding a target with very narrow filters as they could not see a star in live view mode. That is absolutely not an issue for a camera like your 294 which is more than sufficiently sensitive. 

Would love to know who is feeding you that information. 

Adam 

 

 

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Adam J

Adam J

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1 hour ago, Anthonyexmouth said:

I'm looking at getting one of these for my 294. Altair are touting their triband for heavy light polluted areas and the quad band for moderately polluted areas. both are the same price at £215

 

As discussed about your better off with a duel band as opposed to tri-band.

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Adam J

Adam J

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1 hour ago, Rattler said:

Well, I went for the STC. This is my first image with it. Only 55 minutes as I lost about an hour due to guiding issues.

FINALSGL.png

Looking good in terms of signal but i would process it differently almost like you process separate Ha and OIII data. Its possible to extract channels and reasign them to different colors so if you want the more classical electric blue look as opposed to green then you can separate the channels process each channel and then re-integrate them. Its actually something that you need to do to get the most from a filter like this as in lots of nebula is you dont then the OIII will get buried under strong Ha signal and you will get very little color variation in the image. 

Adam

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