The Wolf Nebula

[gregbradley]

[QUOTE=DavidTrap;1022464]I think it's better Greg, but the stars are all white - I was wondering if some shorter subs might give you back some star colour??



Not sure which stars you are referring to - the ones in the glob? I think they probably are white.

The rest of the stars do have colour, mostly yellow and some subtle blue ones. Your monitor? The 16803 has a well depth of at least 100,000 electrons and even a half hour exposure is unlikely to lose star colour except in the very brightest perhaps. I noted that R Jay Gabany and Don Goldman both now use 30 minute exposures as their standard. They use 16803 cameras too.

Greg

[gregbradley]

To me, the latest H-alpha shots by experienced imagers like yourself and Paul are a discovery machine.

There is so much diffuse Ha on your image that it is going to be difficult to distinguish individual objects from the Ha background, in ultra-deep Ha exposures!

Actually, the main scientific interest of deep amateur Ha imaging might be the detection of highly unusual Ionized Gas structures far above the plane of the Milky Way, like ultra-faint outflows and supergiant Ha shells.

cheers, Robert

That's an interesting concept. Where would you point the scope to pick that area up? Above the Milky Way centre star area?

Greg

[madbadgalaxyman (Robert)]

I express the opinion that the most relevant posts about the possibility of a deep H-alpha Imaging Survey by amateur astronomers, should soon be copied into the Science Forum.

I am happy to copy an edited version of them into that forum, and to continue this discussion in the 'heavier' forum!

Originally Posted by gregbradley

bad galaxy man said:
Actually, the main scientific interest of deep amateur Ha imaging might be the detection of highly unusual Ionized Gas structures far above the plane of the Milky Way, like ultra-faint outflows and supergiant Ha shells.
Greg said:
That's an interesting concept. Where would you point the scope to pick that area up? Above the Milky Way centre star area?

Greg,

I will find some H-alpha images of edge-on spiral galaxies that show unusual HII distributions extending outwards at right angles to the plane of a galaxy. This might give us a better idea of what to look for.

As mentioned in my thread "massive molecular outflow in NGC 253"(in Science Forum), there is often an outflow of gas "vertical" to the plane of a spiral galaxy, an outflow which has several components, e.g. neutral atomic hydrogen gas (detectable at 21cm in the radio regime), ionized gas (e.g. OIII, Ha, etc), and molecular gas (millimeter and submillimeter emission).

The extraplanar or above-plane Ha emission in our own Galaxy will be very very faint and very very extended, but well above the Galactic Equator there is at least the possibility of discovering something that was previously unknown.

Generally, gas is often pushed out of the disk component of spiral galaxy above those parts of the disk where there are very multiple OB stars and supernovae; hence my interest in the possible dust+gas chimney above NGC 6231+Scorpius OB1 .

I have downloaded nearly every paper that was ever written about NGC 6231 and Sco OB1 and RCW 113......the cluster is often studied, but the nebular shell surrounding it is hardly ever studied by professional astronomers!!

cheers,
Robert

Originally Posted by Paul Haese

Urgh, Robert. It took enough time to image my image of this area. At 21 hours I have probably the deepest image of the object with 11 or 12 hours of Ha. Perhaps it might be prudent for a group of us to image the region in Ha and produce a combined survey. I am more than happy to contribute and participate in such a survey.

Paul,

I have enjoyed your very deep image of a section of RCW113.
A hypothetical "vertical" dust chimney above the N6231 + Scorpius OB1 + Supershell complex is well shown in your image entitled "Galactic Centre"....this feature is Quite suggestive of gas & dust expulsion from the Galactic plane, as was first discovered on Greg's 11 hour Milky Way image.

I am fascinated with the Giant Shell Structure of which RCW113/Gum 55 is a part. It may well be a complete shell, and it should have some astrophysicalinterest.

I believe that deep Survey Images of the wide-scale spatial distribution of HII over the face of the apparent Milky Way, imaging multiple Deep fields, could potentially be useful, especially for the very very faint Ionized Gas Features such as :
- expanding supershells of ionized gas that are powered by OB stars and supernovae. For instance, what is the origin and future evolution of the shell nebula that includes RCW 113? Stellar winds? Supernovae?
- material being pushed far above the galactic plane, e.g. chimneys and plumes of H-alpha emitting gas that is outflowing from spiral galaxies, at 90 degrees to the plane of the disk component

(subtracting out the stellar continuum light from the Ha filter images would be necessary, so as to leave only the light from the Halpha line)

It seems to me that amateur nebulae imaging could overcome the deficiencies of some of the professional H-alpha surveys of the Milky Way :
(1) Big Telescope sky surveys of Large Areas of Sky are often not optimized for depth , because individual fields in these surveys usually have to be a "rush jobs" so as to avoid cost and time overruns.
(2) H-alpha surveys of the Milky Way done by professional astronomers generally stick to fields that are relatively near to the galactic equator (e.g. VPHAS+ does not go beyond +/- 5 degrees galactic latitude), which means that these surveys miss a lot of the faint and little-understood features that may exist far above the galactic plane; there is significant scientific uncertainty about what happens to gas as it is ejected to far above the plane of a spiral galaxy (at the "disk-halo interface").

It is now a long time since the publication of the pioneering large-sky-area Southern Milky Way HII region surveys and catalogs of Rodgers & Campbell & Whiteoak (RCW), Gum, Bart J Bok, Georgelin et al., and others;
and I think today's amateur astronomers could do better than these people if amateurs were to undertake large area H-alpha surveys of the Milky Way. For instance, the RCW catalog, which is probably the most important and useful general-purpose catalog of southern HII regions, was made with an 8 inch Schmidt Camera and Kodak 103a-E emulsion !

It is hard to say if Deep imaging of HII features by amateur astronomers can actually lead to useful science, but discoveries are always possible when images or sky surveys reach a greater depth and/or achieve greater sky coverage. (this has occurred in the case of deep galaxy imaging by amateurs....)

Best regards,
Robert Lang

[multiweb (Marc)]

I have imaged this area repeatedly in the past at various focal lengths in Ha and more recently in infrared. The shells seem to be going on both sides of the milkyway band, up and down.

Hydrogen Alpha: 35mm, 50mm, 100mm
Infrared: 100mm

[madbadgalaxyman (Robert)]

Originally Posted by multiweb

I have imaged this area repeatedly in the past at various focal lengths in Ha and more recently in infrared. The shells seem to be going on both sides of the milkyway band, up and down.

Hydrogen Alpha: 35mm, 50mm, 100mm
Infrared: 100mm

Marc,
very good observations, and an extremely interesting interpretation.

As I suggested in my previous post, it may be necessary to subtract out the stellar red light contribution from the light that is admitted by the Ha filter, in order to go further in our understanding of the structures of extremely faint nebulae like this one.
(there are various mathematical "fudge factors" that model stellar light in the red band)
Also, there is a lot of diffuse Ha which makes it hard to see the outlines of individual HII regions.

Robert

[multiweb (Marc)]

Originally Posted by madbadgalaxyman

As I suggested in my previous post, it may be necessary to subtract out the stellar red light contribution from the light that is admitted by the Ha filter, in order to go further in our understanding of the structures of extremely faint nebulae like this one.
(there are various mathematical "fudge factors" that model stellar light in the red band)
Also, there is a lot of diffuse Ha which makes it hard to see the outlines of individual HII regions.

Hi Robert, I'm not sure how to do that but I'd love to learn more about it. The Ha filter I use has a bandpass of 7nm around 650nm. The IR filter was blocking everything up to 740nm and letting everything in onwards. Sii and Ha are below and out. That's why you can't see the prawn and NGC6188. A lot of obscured clusters come up though at that wave length. The QE of my camera drops dramatically from 800nm onwards and is quasi inexistant at 900nm onwards.

[naskies (Dave)]

Another great image, Greg! Nice to see you've been productive with deep imaging again

This has also been a great thread to read - a mix of pretty pictures and science.

[madbadgalaxyman (Robert)]

Originally Posted by multiweb

Hi Robert, I'm not sure how to do that but I'd love to learn more about it. The Ha filter I use has a bandpass of 7nm around 650nm. The IR filter was blocking everything up to 740nm and letting everything in onwards. Sii and Ha are below and out. That's why you can't see the prawn and NGC6188.

Indeed, amateurs could benefit from the ability to produce "images in the h-alpha line only ".(showing only nebular light, without stellar contamination)

I wonder if Richard Crisp (I think I remember the name properly) knows how to do it; he does a lot of amateur Ha of galaxies.

In the jargon of professional astronomy, these are referred to as "continuum subtracted" images. i.e. the stellar continuum has been subtracted out of the image, leaving only the nebular light from the actual Ha line itself.

Most professional galaxy images in the Halpha line are presented with the continuum already subtracted.

I believe that the procedure involves making a red light image, and subtracting it from the Ha image, taking into account various mathematical transformations that are necessary.

If I get "a round tuit", I will try to find a quick and easy way to do this; there must be some procedures for continuum subtraction in the professional literature.

[marc4darkskies (Marcus)]

I guess I missed this one! A belated well done - a very nice rendition Greg!

Cheers, Marcus

[naskies (Dave)]

Originally Posted by madbadgalaxyman

Indeed, amateurs could benefit from the ability to produce "images in the h-alpha line only ".(showing only nebular light, without stellar contamination)

Astrodon sells a 5 nm red continuum filter, for subtracting stars from Ha images:

http://www.astrodon.com/products/filters/narrowband/

[gregbradley]

Originally Posted by naskies

Another great image, Greg! Nice to see you've been productive with deep imaging again

This has also been a great thread to read - a mix of pretty pictures and science.

Thansk Dave. Yes it has been an interesting thread.

Originally Posted by marc4darkskies

I guess I missed this one! A belated well done - a very nice rendition Greg!

Cheers, Marcus

Cheers Marcus. Hows the Officina Stellare scope coming along?

Originally Posted by naskies

Astrodon sells a 5 nm red continuum filter, for subtracting stars from Ha images:

http://www.astrodon.com/products/filters/narrowband/

Yeah that is the one I was thinking of.

Greg.

[multiweb (Marc)]

Originally Posted by naskies

Astrodon sells a 5 nm red continuum filter, for subtracting stars from Ha images:

http://www.astrodon.com/products/filters/narrowband/

So basically it lets only starlight through, then you subtract this from your Ha correct? Like a star mask?

[madbadgalaxyman (Robert)]

Originally Posted by multiweb

So basically it lets only starlight through, then you subtract this from your Ha correct? Like a star mask?

Subtracting the red image should work, but I think there is still some maths involved to adjust the images.

Perhaps contact Richard Crisp :
rdcrisp@earthlink.net

His website is : www.narrowbandimaging.com

I think most of us in this thread would agree that when there is a really intense stellar background from the Milky Way, continuum subtraction is highly desirable.

Obviously, if there were nebular emission lines somewhere within the bandpass of the filter that is used as a red stellar continuum filter, this would stuff things up completely.