Thoughts on dual/tri/quad band + DSLR?

[rnobleeddy]

Realize there's a lot to consider, and lots of opinions, but hopefully this question is specific enough to be worth asking. 

I've enjoyed my first few months imaging with a modded DSLR, and longer term, might consider a small observatory/shed in the garden, at which point a mono camera + filter wheel seems like a good idea. At  the moment that's feels like a lot of expense given the relative hassle of getting everything setup in the garden. I've also come to the conclusion that there's not a great deal of value in the lower end of the OSC dedicated cameras.

I'd not really considered dual/tri/quad band filters until I saw a few posts about them, but it appears that it might a worthwhile middle ground. 

Just wondering if anyone has experience with them and can help with recommendations? I'm in a Bortle 5/6 area with what I consider to be moderate light pollution, on the edge of a small town, with fields on one side/town on the other.  I realize that narrow band filters  are also an option, but I'd prefer to retain the benefits of OSC, and much prefer to image from the comfort of my study rather than having to constantly head out to the garden!

Specifically, I'm wondering:

- how much of an improvement in imaging have you seen with filters of this type?

- how does the color end up? It appears most filters (whether dual, tri or quad) just pass two narrow bands, one in R and one across B/G - do they end up balanced?

- is any particular brand or type (dual/tri/quad) better for one use or another? 

 

So far I've been considering:

- Altair (quad https://www.altairastro.com/altair-quadband-osc-ccd-2-mm-filter-321-p.asp and tri https://www.altairastro.com/altair-triband-osc-ccd-2-filter-322-p.asp)

- Optolong (tri band https://www.firstlightoptics.com/optolong-filters/optolong-l-enhance-narrowband-deep-sky-imaging-filter.html or dual https://www.firstlightoptics.com/optolong-filters/optolong-dual-band-l-extreme-filter.html)

 

 

 

[Kyle Allen]

I have the Optolong L-eNhance filter. So far I've only used it on the Veil Nebula but it seems to work well. This is 15 x 2 minute exposures with no calibration frames taken last night using a William Optics ZS61 and Star Adventurer with unmodded Canon EOS 100D (batteries ran out!).

Compared with my attempts at imaging the Veil Nebula unfiltered, it is much easier to get the nebula to show without the stars taking over the image. The L-eXtreme should have even better contrast but would require longer exposures which was my reason for going with the L-eNhance - currently I only have a Star Adventurer.

The colours aren't balanced but I always have to do that anyway. I just move the black point until the channels line up.

[AKB]

I have the Altair quadband.  Unfortunately, I don't have a side-by-side comparison (and my camera is not a DSLR) but, speaking of the Veil, and with 20 x 2min and a 120ED I did this. 

It does tend to give a red tint to the stars, but it's much better than I've managed before...

[R26 oldtimer]

I have the optolong l-enhance.

First of all let's see what this is all about. These are not light pollution filters. Perhaps not the best narrowband band or with a tight bandpass but they are NB. So what your imaging is not enhanced rgb, it's HOO. Is it pure HOO? Not entirely because your camera's rgb array has not steep cutoff, so some red and blue creeps in to the green and vice versa, but that's a different subject. The bottom line is that you get similar results as you would if you used two different nb filters (Ha & OIII) in two sessions but you get that same data in one session.

Go for the L-eXtreme if you can afford it.

[TerryMcK]

I have the Altair triband and find it is reasonably good both with DSLR and dedicated Astrophotography OSC camera especially in Ha. However it does have issues with OIII band and I find it a touch too wide in bandwidth. It covers the HII band in the same green spectrum. The quadband is for less light polluted skies and may be good for you. I’m in Bortle 7/8 hence the tribander.

My favourite filter for OSC or DSLR is without doubt the IDAS D2 which blocks out LED lights as well as traditional light pollution but lets through most of the RGB. It produces far better pictures than the Altair Tribander. However use the Ha from the Altair as a lum layer with the RGB from the IDAS and it really makes images pop. 

However I also do mono and have Ha, OIII and SII filters in the armoury. UK skies are not ideal for mono due to the multiple filter exposures required, unreliable cloudy skies, rain etc. but when the skies are on form mono is superb.

Edited October 10, 2020 by TerryMcK

[rnobleeddy]

1 hour ago, TerryMcK said:

I have the Altair triband and find it is reasonably good both with DSLR and dedicated Astrophotography OSC camera especially in Ha. However it does have issues with OIII band and I find it a touch too wide in bandwidth. It covers the HII band in the same green spectrum. The quadband is for less light polluted skies and may be good for you. I’m in Bortle 7/8 hence the tribander.

My favourite filter for OSC or DSLR is without doubt the IDAS D2 which blocks out LED lights as well as traditional light pollution but lets through most of the RGB. It produces far better pictures than the Altair Tribander. However use the Ha from the Altair as a lum layer with the RGB from the IDAS and it really makes images pop. 

However I also do mono and have Ha, OIII and SII filters in the armoury. UK skies are not ideal for mono due to the multiple filter exposures required, unreliable cloudy skies, rain etc. but when the skies are on form mono is superb.

Thanks. I already use the Astronomik CLS CCD which I'd guess is similar to the IDAS D2 without the LED being filtered out, so maybe I'm expect too much for a tri or quad band filter.

I'd guess the triband helps more on nights with the moon?

[rnobleeddy]

2 hours ago, R26 oldtimer said:

I have the optolong l-enhance.

First of all let's see what this is all about. These are not light pollution filters. Perhaps not the best narrowband band or with a tight bandpass but they are NB. So what your imaging is not enhanced rgb, it's HOO. Is it pure HOO? Not entirely because your camera's rgb array has not steep cutoff, so some red and blue creeps in to the green and vice versa, but that's a different subject. The bottom line is that you get similar results as you would if you used two different nb filters (Ha & OIII) in two sessions but you get that same data in one session.

Go for the L-eXtreme if you can afford it.

Thanks. I guess I was thinking that more bands are better, but actually, it's better to to just have H/O and for them to be cleaner?

The l-enhance is on offer, but  extreme is £70 more. if I buy this, it'll probably commit me to keeping the OSC + filter for the rest of the winter, and I can reassess both how much I'm imaging and the finances next summer.

[TerryMcK]

3 hours ago, rnobleeddy said:

I'd guess the triband helps more on nights with the moon?

Yes it does but if you plan to point in the other direction the IDAS also does a stirling job.

[ollypenrice]

17 hours ago, R26 oldtimer said:

I have the optolong l-enhance.

First of all let's see what this is all about. These are not light pollution filters. Perhaps not the best narrowband band or with a tight bandpass but they are NB. So what your imaging is not enhanced rgb, it's HOO. Is it pure HOO? Not entirely because your camera's rgb array has not steep cutoff, so some red and blue creeps in to the green and vice versa, but that's a different subject. The bottom line is that you get similar results as you would if you used two different nb filters (Ha & OIII) in two sessions but you get that same data in one session.

Go for the L-eXtreme if you can afford it.

Yes, this is what makes the most sense to me, looking at the bandpasses. So the filter might be good on targets rich in Ha and OIII but will be destructive of reflection nebulae because the broadband blue is blocked. This will also slew the star colour towards red, as AKB points out.

Olly

[R26 oldtimer]

That's correct, in the trifid nebula, only the Ha lobe appears and it will not capture the blue one (reflection).

It would make sense for a tri-band if it was to capture three nb signals in the three distinct parts of the spectrum red-green-blue. It's a shame that SII is not in the greens....

[Stu Wilson]

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Thats my veil nebula with OSC and Altair Quadband.