Narrow band filters / filter wheel dilemma

[knobby]

Hi all, should have really researched before I bought the 5 position wheel 🙂 I ventured into mono a short while back (ZWO 1600mm / 5 pos wheel / LRGBHA)

I've been so impressed with Ha at my LP garden (RED/WHITE ZONE) that I'm now thinking I should have got the 8 position wheel !

Whats the best shortcut to try ?

take out the Green filter  - put in an Oiii, therefore still allowing RGB with a synthetic green,  try Ha - Oiii of some sort or go the whole hog and ditch the RGB and get Oiii and Sii ... leaving an empty slot ?

The 8 position would be too much additional expense so that route is out of the question and probably too big / heavy for the Az-Gti anyway

 

Opinions gratefully received

[carastro]

These smaller Filterwheels are a real pain.  I live in a LP location and use narrowband for a lot of images, but from time to time use RGB as well.  

If you've only got 5 positions and can't afford to replace the filterwheel, I would say the best option would be:

Ha (can be used in the Red channel if you want to do RGB.

Oiii

Sii

Green

Blue

In a LP location the Luminance normally comes out dreadful anyway, it does for me in Bortle 8.

So you can then do narrowband or HaGB (using the ha in the red channel).  This might not be the conventional (or correct) way of doing things, but often I do HaRGB and find I am normally replacing the Red or combining the red with Ha and sometimes wonder whether to bother doing Red for these type of images.  (I use LRGB when I go to a dark lcation). 

I also use the Ha as the luminance channel by adding for a 2nd time for detail. 

Not a perfect solution but might get you out of your predicament.

Hang on to the Luminance and red filters for when you can get an 8 position wheel.

Carole

Edited September 21, 2019 by carastro

[knobby]

Thanks Carole, sounds logical, which do you use for focusing ? I've been using the Lum as it lets more light in.

[carastro]

Well I have a 7 position filterwheel so I normally use Lum for focus, but then I always check the focus on the other filters as well to check they are all the same (or not), so I always check Ha as well if I am using narrowband. 

Without the lum as an option, then I would try the green or blue initially because they will be easier to find and focus, but once that is in focus, check the other filters you are going to use as well.  

Generally I find most of my filters are par focal, though occasionally one of them is slightly different (don't understand why this should vary as this is not always the case).  If any are different obviously I have to take those images separately re-focussed.

Carole 

Edited September 21, 2019 by carastro

[knobby]

Thanks Carole, looks like I'm just over the water from you so similar conditions, appreciate your input 👍

I think I'm going to get the Oiii and Sii, now just deciding between sticking with ZWO to match the Ha I already have or a set of Baader narrow band and selling the ZWO lot.

[Adam J]

On 21/09/2019 at 11:38, knobby said:

Hi all, should have really researched before I bought the 5 position wheel 🙂 I ventured into mono a short while back (ZWO 1600mm / 5 pos wheel / LRGBHA)

I've been so impressed with Ha at my LP garden (RED/WHITE ZONE) that I'm now thinking I should have got the 8 position wheel !

Whats the best shortcut to try ?

take out the Green filter  - put in an Oiii, therefore still allowing RGB with a synthetic green,  try Ha - Oiii of some sort or go the whole hog and ditch the RGB and get Oiii and Sii ... leaving an empty slot ?

The 8 position would be too much additional expense so that route is out of the question and probably too big / heavy for the Az-Gti anyway

 

Opinions gratefully received

SII is not required as you can just do bi-color images. Either HOO or HSyO

So i would go with Ha OIII R G B

But on the whole yes this is why I got the 8-position wheel. Realized that eventually it would be a false economy.

Adam

 

[carastro]

Quote

SII is not required as you can just do bi-color images. Either HOO or HSyO

That's a good point, some targets work well in HOO (veil for instance).  Though here are a few where the signal in Sii is better than the signal in Oii (California nebula), but that idea will certainly keep you going for a while.

Carole 

[knobby]

HsyO ?

Ha - synth something - Oiii

?

[Adam J]

On 23/09/2019 at 13:05, knobby said:

HsyO ?

Ha - synth something - Oiii

?

Yes, you assign ha to red and oIII to blue and then generate a synthetic green channel. You can find tutorials online. 

[knobby]

Cheers all, I've got the Oiii ordered, probably why the weather has turned naff !

[MartinB]

When I started colour imaging it was without a filterwheel.  I had to change each filter manually.  I think I was the first person on the forum to invest in a motorised filter wheel, a 5 position Trutek.  It seemed a ridiculous extravegence at the time.  10 years ago I got a QSI camera with an integrated 5 position wheel and am still using it.  It is a relatively minor hassle, the good thing being that you do longer imaging runs so that you only swap around your filters during the day.  Convenient though an 8 position wheel might you only need one if you are working roboticly from a remote location.

[prusling]

5 hours ago, Adam J said:

Yes, you assign ha to red and oIII to blue and then generate a synthetic green channel. You can find tutorials online. 

StarTools is one tool that can interpolate green from Ha (as red) and Oiii (as blue) giving images where the Ha comes out a rich golden colour. I sometimes process using the Ha as Luminance as well but that doesn't seem to make much difference. I also have an Sii filter but struggle to capture enough with it to avoid Hubble SHO coming out over-green.

[Science562h]

I put in, what I'm going to use. For example, it's winter; so, there are no planets to image or view. I leave out my Venus, Mars & Jupiter filters. Currently:

1.  Open
2. UV-IR Cut
3. Moon 25%
4. Moon 13%
5. O-III 

My targets are the Moon, Orion & stars. I have plenty of other filters, just don't need them. I can always add to eyepiece, which is why I leave "1" open. 

Image. Five position filter wheel.

Maksutov Cassegrain

 

Edited January 1, 2020 by Science562h
Grammar