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Naked eye observation of Pleiadies neb. is that possible?
/Magnus

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I tried several times and finally saw the Merope and Maia nebula one very transparent night with my 4-inch TV-102 Light Cup. I think the key is transparency and any haze or light scatter would just make the observation dubious. I used various stars outside of M45 as gauge to make sure it wasn't light scattering , a tip I gratefully got from an expert.

Ron B[ee]

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5-inch Tele Vue NP127 APO
4-inch Tele Vue TV-102 APO
8-inch f/6 Discovery PDHQ Dob

Edited by Ron B[ee] (03/21/05 02:33 PM)

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Hi Don,

Could you just elaborate a bit on what is your dark sky. For me dark sky is mag 5.5 to 5.8. I suspect you are talking about mag 6.5 to 7.0 skies.

I've observed M45 literally hundreds of times just over the last year and a half, as it was the subject if my LM studies. For the first time in my life this past year I once was able to see the Merope nebula. That was with a BT100 binocular telescope and 4mm exit pupils under mag 5.7 skies. In all my years of record keeping I've never seen it with either of my 6" scopes nor my 5" scope. I hold no hope of seeing it naked eye!

edz

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I'm pretty sure that subject is discussed in Deep Sky Wonders. Anybody got a copy handy that can give us a quick report?

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Yep web page

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Thank you, Scott.

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Erika



10" LX200 Classic, ETX70-AT, DS Maxscope 60mm, 12" Truss Dob, Orion ED80, WO Binoviewers, 10x50's and 7x50's Binoculars, Rebel XT 350
Having Fun in the Sun!
More solar fun: 2007 July - tracking NOAA10963

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Scott,
Since this is a full-spectrum reflection nebula, a UHC filter would dim it to near invisibility. Unfortunately, the best way to view it is without any filter.

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Actually, from a dark or even a semi-dark sky site, the UHC does help contrast of the Merope nebula just a bit, although for filter use on that object, I still prefer a broadband "light pollution" filter like the Lumicon Deep-Sky. This reflection nebulosity tends to be somewhat bluish like the stars in the cluster, so at least a modest amount of its light can get into the UHC's primary passband. I have had little trouble seeing the faint diffuse fan that extends away from Merope with the UHC and Orion Ultrablock in my 10 inch f/5.6 Newtonian when I am observing on a dark moonless night from my driveway. One night, I even used the UHC on the spiral galaxy M33, and surprisingly, in my 10 inch, I could still see the object's spiral structure with that filter in place (ZLM 6.6). From a really dark sky site, unless you have some faint auroral glow in the sky, no filter is usually needed for the Merope nebula. As for sightings of it naked-eye, when I look up at the Pleiades with my unaided eye at a dark sky site, I see a very faint glow around the stars but only with averted vision. It is unclear whether this glow is just scattered light in my eye/glasses, unresolved stars in the cluster, or true nebulosity. Clear skies to you.

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David W. Knisely
Hyde Memorial Observatory
http://www.hydeobservatory.info

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Scott,
Since this is a full-spectrum reflection nebula, a UHC filter would dim it to near invisibility. Unfortunately, the best way to view it is without any filter.

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Actually, from a dark or even a semi-dark sky site, the UHC does help contrast of the Merope nebula just a bit, although for filter use on that object, I still prefer a broadband "light pollution" filter like the Lumicon Deep-Sky.

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Boy, now you guys have really got me confused Maybe I'll try my broadband just for kicks.

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Scott
10" LX200 Classic, Konus 200, Orion ST80, ETX90 OTA, 60mm Celestron alt-az, Obie 20x80's, Meade 10x50's

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Scott,
Since this is a full-spectrum reflection nebula, a UHC filter would dim it to near invisibility. Unfortunately, the best way to view it is without any filter.

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Actually, from a dark or even a semi-dark sky site, the UHC does help contrast of the Merope nebula just a bit, although for filter use on that object, I still prefer a broadband "light pollution" filter like the Lumicon Deep-Sky.

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Boy, now you guys have really got me confused Maybe I'll try my broadband just for kicks.

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Well, sorry about the confusion, but perhaps a little background information would help things a bit. There are three types of nebulae: Dark Nebulae, Emission nebulae, and Reflection nebulae. Dark nebulae are just dense clouds of dust which are visible when they block out the light of a rich field of background stars or bock portions of an bright nebula in the background (the Horsehead Nebula is a good example). Emission nebulae (like the Orion Nebula for example) are clouds of gas (sometimes known as "HII Regions") which are relatively near very hot stars that put out a lot of ultraviolet light. This UV light excites the gas atoms and causes them to emit light at only a few specific wavelengths, most notably, the red H-alpha line (6563 Angstroms), the bluish-green OIII lines (4959 Angstroms and 5007 Angstroms), and the blue H-Beta line (4861 Angstroms). Our eyes don't usually pick up the H-alpha line all that well, but the OIII and H-Beta lines come through fairly well. These are the lines that "nebula" filters tend to work with, as they pass them and exclude nearly everything else. Reflection nebulae are different, in that, rather than having mostly gas, they contain very fine particulate matter which scatters or reflects the light from nearby stars. Thus, they produce a more broad spectrum of light which is similar to that of the stars which are near them. The nebulosity around the Pleiades is one example of a reflection nebula. However, the brightest stars in that star cluster tend to be somewhat on the bluish side, so the light scattered by a nearby reflection nebula will also tend to be more bluish. The passband of a narrow-band nebula filter like the UHC is broad enough to take in both the OIII and H-Beta lines plus the wavelengths in between them, so it can also be broad enough to let at least some of the scattered light from a reflection nebula through as well. However, a filter that just "notches out" the wavelengths of the common light pollution lines (mercury or sodium vapor, as well as the airglow lines) but passes almost everything else can be a little more effective on reflection nebulae than a narrower bandpass filter like the UHC, since it lets even more light from a reflection nebula through while only blocking several annoying wavelengths. I hope this clears up a little of the confusion. Clear skies to you.

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David W. Knisely
Hyde Memorial Observatory
http://www.hydeobservatory.info

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David,
Note the shape of the "glow" around the Pleaides next time you're in a dark site. You'll probably see, as I did, that the "glow" extends a finger in the direction of the Merope nebula, and the overall shape resembles long time exposure photographs of the nebula.
The overall shape of the star patterns are similar, but without the extensions visible as a "glow" around the cluster.
I do not see a similar glow around the Perseus double cluster, the Praesepe, the M46-47 area, or the Hyades with averted vision--yet another reason I think what we are seeing is nebula.

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At the times I have observed the glow in and around the Pleiades, I have never really confirmed the fan of the Merope Nebula, as the resolution with averted vision did not allow me to clearly determine whether it was there or not. Even with my 80mm f/5 refractor, the fan is not all that prominent, although I usually have no trouble seeing it at around 13x with that scope. That a glow exists is certain, but what exactly the glow is due to is not quite as certain. Clear skies to you.

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David W. Knisely
Hyde Memorial Observatory
http://www.hydeobservatory.info

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