Filter question

[Bottletopburly]

Would a dedicated O111 filter give  a better results  than a dual filter which seems to be a HA and O111 or the same, with the bonus the the dual also captures Ha bear in mind this would be used with a unmodded  Dslr. 

[+Graham]

Cannot see the point of running filters on an unmodified DSLR. 

 

[Bottletopburly]

23 minutes ago, Graham said:

Cannot see the point of running filters on an unmodified DSLR. 

 

That was my next question would I see any benefit, more so the O111  

[Sheila]

OK it may be me that is a bit dim but how do you get a dual filter for a DSLR.  Wavelength of Ha is about 650nm and Oii is about 500nm that's quite a range?

 

My filters are obviously for CCD but they have a very narrow window of wavelength for each one  (3nm).  Does this means the filters for DSLR (dual)

would let in everything between 500-650 nm, would that not be a bit noisy?   If this is the case then narrowing this window would mean less light would get through?  assume that means

you would need longer exposures?    I am not sure what the benefit would be as I dont do DSLR stuff?   An explanation would be appreciated as I thought generally you used a 

modded dslr with light pollution/ uv filter etc?  If the DSLR is not cooled and used for fainter stuff in is noise going to be a problem here?

 

 

[Bottletopburly]

18 minutes ago, Sheila said:

OK it may be me that is a bit dim but how do you get a dual filter for a DSLR.  Wavelength of Ha is about 650nm and Oii is about 500nm that's quite a range?

 

My filters are obviously for CCD but they have a very narrow window of wavelength for each one  (3nm).  Does this means the filters for DSLR (dual)

would let in everything between 500-650 nm, would that not be a bit noisy?   If this is the case then narrowing this window would mean less light would get through?  assume that means

you would need longer exposures?    I am not sure what the benefit would be as I dont do DSLR stuff?   An explanation would be appreciated as I thought generally you used a 

modded dslr with light pollution/ uv filter etc?  If the DSLR is not cooled and used for fainter stuff in is noise going to be a problem here?

 

 

https://www.firstlightoptics.com/light-pollution-reduction-imaging/optolong-l-enhance-dual-narrowband-deep-sky-imaging-filter.html

 According to the blurb says for dslr ,osc  cameras 

 copy and pasted from link 

 

High transmission of H-Alpha, H-Beta and Oxygen III emission lines (avg. 90% or higher)

Use with colour DSLR, CMOS and CCD Cameras

1.25" or 2" Mounted Sizes

Supplied in a protective plastic case with EVA foam lining

More than 150 coating layers on B270 glass.

1.85mm Thick Glass

Fine-optically polished on both sides - ensures accurate λ/4 wavefront and <30 seconds parallelism over the both surfaces

Ultrasonic wave cleaned substrate with purified water - Cleanup by 13 stage purified water tank to remove impurities and dust effectively

Ion source assisted coating— For durability and resistance to scratching, as well as stability on CWL (central wavelength)  - no deviation affected by temperature change

Stringent quality testing process - each filter is tested on a spectrophotometer and laser interferometer

Transmission Chart

White Line - Represents the transmission curve of the L-eNhance Filter.

The Major Emission Lines of Nebulae: H-α (656.3nm), H-β (486.1nm), OIII (495.9nm) and OIII (500.7nm)

The Major Emission Lines of Artificial Light Pollution: Hg / Mercury (435.8nm, 546.1nm, 577nm and 578.1nm), Na / Sodium (598nm, 589.6nm, 615.4nm

 

[Sheila]

Not as daft as I thought, the filter lets through anything between about 450nm to 680 nm so is quite wide.  Good for cutting out light pollution though and other stuff you don't want.

If you go with just an Oiii much narrower filter, it will darken the image quite a lot as the light transmission is much less through a narrowband filter just

for Oiii i suspect.  To get the same detail i would think your subs would have to be considerably longer, or a LOT more of them.  The only thing I can suggest is to look at

someone else's data to see if you can see a difference that would make you want to buy one?

 

How it figures out the colours etc I will leave to the technical pixies in the processing   LOL

[8472]

There's a few Duo (and even Triad and Quad, if your pockets are deep enough) narrowband filters designed for OSCs on the market now.

 

OPT, STC, Optolong (what I use) and a few others all do them.

 

Obviously not as efficient as mono+filters, but it gives OSC users the option of narrowband through the Bayer matrix.

 

Mine maps Oiii/Hb to blue/green and Ha to red. Yes, the bandpass is wider than regular NB filters, but much narrower than the traditional LP filters.

 

With this filter, my subs generally need to be in the 600s range at F/6 and faster optics for the photons to swamp the read noise and bring the histogram to the ideal 25-33% range. But I have shed engineered both my OSCs with set point cooling to achieve this with lowered noise levels. YMMV.

 

HTH

[Bottletopburly]

9 hours ago, 8472 said:

There's a few Duo (and even Triad and Quad, if your pockets are deep enough) narrowband filters designed for OSCs on the market now.

 

OPT, STC, Optolong (what I use) and a few others all do them.

 

Obviously not as efficient as mono+filters, but it gives OSC users the option of narrowband through the Bayer matrix.

 

Mine maps Oiii/Hb to blue/green and Ha to red. Yes, the bandpass is wider than regular NB filters, but much narrower than the traditional LP filters.

 

With this filter, my subs generally need to be in the 600s range at F/6 and faster optics for the photons to swamp the read noise and bring the histogram to the ideal 25-33% range. But I have shed engineered both my OSCs with set point cooling to achieve this with lowered noise levels. YMMV.

 

HTH

Kev have you ever tried blending data from these filters to regular data , like say Pleiades regular data and adding o111 filter data ?

[8472]

1 hour ago, Bottletopburly said:

Kev have you ever tried blending data from these filters to regular data , like say Pleiades regular data and adding o111 filter data ?

Yes, I have.

 

My Cocoon nebula image from Kelling consisted of 1 night of regular RGB data blended with a second night of l-eNhance Oiii/Ha data. If I recall, It worked quite well. It's in the DSO gallery section somewhere.

 

Btw, I wouldn't purchase an Oiii filter for an OSC camera. With the CFA, you'd only be making use of a small portion of the sensor and it would take forever to acquire a meaningful amount of data.