Do I need a UHC?

[Don Pensack]

1 hour ago, Kon said:

You have me intrigued on colour on M42, 8 and 17 with a UHC. I have seen deep reds and teal green on M42 without a filter (under excellent transparency) but not on the others. Does a UHC routinely help or does  it make them pop more under excellent conditions?

I will be placing an order on the original DGM.

I think having the red transmission, when the red is the brightest emission from the nebula, makes the nebula appear larger and allows those of us with exceptional abilities to see reds and long wavelengths, to pick up reds in the nebulae.

M42 is so bright it damages my night vision, so no surprise I see multiple colors there.

M8 and M17 are not as bright, so it is an exceptional night where even a filter that passes reds allows reds to be seen (or maybe I should call it "pinkish-grey").

I've also see red in M20 and M16, but due to the low surface brightness, the colors could be spurious.

To wit: under extremely low light conditions, two grey areas immediately adjacent, one of which is ever so slightly brighter than the other are seen as greenish-grey (the brighter) and reddish-grey (the fainter).

The colors aren't real, but are filled in by the brain.  It's always wise to distrust the colorations.

However, I have seen a yellowish-beige in M42 adjacent to the central region, and marked it on a crude drawing.  Later, I verified its reality on color photos of the nebula.

So sometimes the colors seen are real.

 

I'm also at 35°N, so these nebulae all rise much higher in the sky for me.  M8, for instance, culminates at +30-31° for me.  So I see a brighter nebula against a darker sky. 

[Stu]

On 29/07/2022 at 22:35, Jiggy 67 said:

Personally I prefer the uhc over the OIII. Its not just about the darkness of the sky but also the aperture of the scope. I also use an 8inch newt and find it's at the limit of usefulness for an OIII filter, it's just about enough for this filter but I definitely wouldn't bother with a smaller aperture because an OIII will just darken the image too much, you need as much light as possible with this filter which is why it is not the best for an 8inch. I find the UHC better as it has a wider bandpass. I love observing planetary nebula, many of them can be seen without a filter, a UHC will assist in making it stand out against a black background, some, even in light polluted skies. The same object disappears from view with an OIII...when it would look great with a 12inch scope. I use the Astronomik filter (all my filters are Astronomik or Baader) and can fully recommend it.

I think a lot depends on exit pupil. I would agree that an OIII at small exit pupils/high power in a small scope is too dark, but with a large exit pupil for low power/wide field observations of objects like the Veil and NAN, an OIII can be very effective even in scopes of less than 80mm.

[Kon]

47 minutes ago, Don Pensack said:

I think having the red transmission, when the red is the brightest emission from the nebula, makes the nebula appear larger and allows those of us with exceptional abilities to see reds and long wavelengths, to pick up reds in the nebulae.

M42 is so bright it damages my night vision, so no surprise I see multiple colors there.

M8 and M17 are not as bright, so it is an exceptional night where even a filter that passes reds allows reds to be seen (or maybe I should call it "pinkish-grey").

I've also see red in M20 and M16, but due to the low surface brightness, the colors could be spurious.

To wit: under extremely low light conditions, two grey areas immediately adjacent, one of which is ever so slightly brighter than the other are seen as greenish-grey (the brighter) and reddish-grey (the fainter).

The colors aren't real, but are filled in by the brain.  It's always wise to distrust the colorations.

However, I have seen a yellowish-beige in M42 adjacent to the central region, and marked it on a crude drawing.  Later, I verified its reality on color photos of the nebula.

So sometimes the colors seen are real.

 

I'm also at 35°N, so these nebulae all rise much higher in the sky for me.  M8, for instance, culminates at +30-31° for me.  So I see a brighter nebula against a darker sky. 

I am going a bit off topic here, I am not so sure the colours are a trick of the eye. For example when seeing is not at its best I do not see reds on M42, more like greyish. I have seen rusty reds, pinkish that extend on the wings. Similarly the teal in the trapezium area. If that was the case we should see colours more regularly. It has to be related to the emission and which eye receptors are activated. Ps when I see colours, it is the time that Flame is also 'bright' and the HH visible for me with an Hb filter (after going night vision readjustment for a while).

Yes the others sit at 20 degrees at their best for me so a lot of atmosphere to observe through.

 

But trying with a UHC will be very interesting.