M31 and OII filter

[Jerry_K]

Guys, will OIII filter make Andromeda look better? What DSOs is this filter good for?

Thanks, Jerry

[dts350z]

By itself, or with other filters?

 

I'm not an expert, but my understanding is that stars tend to have gaps in their spectra that correspond to nebula emission lines like Oiii, so unless there is nebulosity in a galaxy I wouldn't think Oiii would be useful. Having said that, I did see an Ha demo with a galaxy where it brought out some non-star features.

 

You could google m31 and Oiii and see what comes up. M31 and narrowband would be another set of search terms.

[astroman133]

Jerry,

 

At the risk of causing controversy, I am not sure that narrowband filtered images are that effective with a DSLR, mainly because of the Bayer filters.  Take Hydrogen alpha for example, even with a modified camera. Only the red pixels will collect any data, so 75% of the pixels (green and blue), after debayering, will contain calculated values for the red data.  The same would be true for other narrowband filters, but still only pixels of the color that matches the filter would contain the "real" data.

 

How do you plan to use the Ha data? Combine it with RGB? by replacing the original red data with the Ha image's Red channel? as a luminance layer? some combination of the above?

 

I tried shooting with a clip-in Ha filter. My camera was not modded, so some (most) of the light that got through the Ha filter was blocked by the cutoff filter in front of the sensor. When the histogram was still plastered against the left edge after a 20 minute exposure I gave up and considered it a learning experience. I still have that filter, in case I ever decide to go crazy and have the T5i modified. I also have an O III clip-in filter, but have never used it.

 

In general, would think that an OIII filter would give a better result on nebulas, instead of galaxies. I may have to give that a try once my observatory is operational...The contractor dug for the footers and the power trench today.  It should be operational by the end of next month.

[Jerry_K]

Jerry,

 

At the risk of causing controversy, I am not sure that narrowband filtered images are that effective with a DSLR, mainly because of the Bayer filters.  Take Hydrogen alpha for example, even with a modified camera. Only the red pixels will collect any data, so 75% of the pixels (green and blue), after debayering, will contain calculated values for the red data.  The same would be true for other narrowband filters, but still only pixels of the color that matches the filter would contain the "real" data.

 

How do you plan to use the Ha data? Combine it with RGB? by replacing the original red data with the Ha image's Red channel? as a luminance layer? some combination of the above?

 

I tried shooting with a clip-in Ha filter. My camera was not modded, so some (most) of the light that got through the Ha filter was blocked by the cutoff filter in front of the sensor. When the histogram was still plastered against the left edge after a 20 minute exposure I gave up and considered it a learning experience. I still have that filter, in case I ever decide to go crazy and have the T5i modified. I also have an O III clip-in filter, but have never used it.

 

In general, would think that an OIII filter would give a better result on nebulas, instead of galaxies. I may have to give that a try once my observatory is operational...The contractor dug for the footers and the power trench today.  It should be operational by the end of next month.

Thanks for advice. I'm already in shooting plan, 30 subs x 10 sec., and I have Neodymium filter on. This one does wonders on Sodium lights LP. So, you lucky guy, real observatory. Round or with sliding roof? I'll email you.Again, thanks for help,Jerry

[Jerry_K]

By itself, or with other filters?

 

I'm not an expert, but my understanding is that stars tend to have gaps in their spectra that correspond to nebula emission lines like Oiii, so unless there is nebulosity in a galaxy I wouldn't think Oiii would be useful. Having said that, I did see an Ha demo with a galaxy where it brought out some non-star features.

 

You could google m31 and Oiii and see what comes up. M31 and narrowband would be another set of search terms.

Thanks, I have already decided against using it. I think that it would work On 7 Sisters, though.

Jerry

[s3igell]

An OIII Filter used on a Galaxy is only working as an impromptu Light Pollution Filter.  Stars, which is what Galaxies are made of, emit rather evenly across the Visible Spectrum - including OIII light which is in the Bluish Green part of the Visible Spectrum.  So, the OIII Filter would work to block other wavelengths such as from Mercury Vapor or Sodium Halide Lighting, but let a rather "even" representation of the Galaxy's Light come through in the Blue-Green area.  And, since Blue and Green Pixels in a Color DSLR occupy 3/4ths of the Pixels total, you don't take too much of a Hit on the Image - as compared to a Ha Filter.

[dts350z]

I am experimenting with narrow band imaging on DSLR.

 

I'm using superpixel mode in DSS and then removing the un-needed colors in Photoshop (blue and green removed from Ha and Sii, and Red removed from Oiii). Superpixel puts my arcseconds per pixel to around 1.7, which is still probably better than seeing anyway, as opposed to fractional arcseconds per pixel with the DeBayer mode

 

FYI there are some whitepapers by Craig Stark on narrowband and DSLR. Of course he's pushing nebulocity but the information is still good.

 

I've done the Ha as L in LRGB, and now am working on a RGB as L, Sii as red, Ha as green, and Oiii as blue image. Oh, and I did an Ha as green with green removed from RGB as well.

 

FYI my RGB subs are 480 seconds through a CLS filter, but the narrowband subs take 1920 seconds (!) at the same iso, 1600.