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1)...With the single-passband red filter (Wratten 23a), red was seen in the Huygenian region *and* the area around it (as well as in the parts of the inner "wing" sections of M42 that are fairly bright).

2)...With the dual passband filters (NPB narrowband, red-leak OIII and red-leak H-Beta), ... reds *were* seen in various parts a little outside the Huygenian region,

3)..as well as in sections of the "wings" and in some other parts nearer to the outer boundary of the nebula.

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I understand that regions listed in point 2 are appering red also in test 1.
I understand that regions listed in point 3 are the so called "well away" spots which are not seen in test 1.

Thus, at least for the latter, they are seen red in the red-leaking filter but are not visible in the W23A.

My point is not whether the regions seen red in W23A turns green in OIII+Ha (that is obviuos if they emit enough OIII). My point is about spots seen red in OIII+Ha which are far away from the immediate surroundings of the Hygenian regions and are not seen in the W23A. How can be possible that a red spot is no longer seen in a red filter?

To be more precise, here is a picture of M42 where I marked various red sposts. Could you tell which of the marked points are seen red in the OIII/Ha filter? (or if there are others not listed. We can refine the picture with better indications (I also wait you Don here).

Edited by Mauro Da Lio (12/15/07 06:37 AM)

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