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Pleaides Nebulosity

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#51 Daniel Mounsey

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Posted 12 December 2012 - 11:35 PM

David,

I double checked the observational notes in NSOG on the nebulosity around M45 and they mentioned the use of an OIII with some subtle improvement. I find that rather odd. I'll do some tests this winter.

#52 David Knisely

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Posted 13 December 2012 - 12:20 AM

David,

I double checked the observational notes in NSOG on the nebulosity around M45 and they mentioned the use of an OIII with some subtle improvement. I find that rather odd. I'll do some tests this winter.


NSOG has a few misleading statements like that one (including one suggesting an OIII be used on the Horsehead, which is ridiculous). For filter use reports, I do not trust NSOG very much. While in sufficient aperture, the Merope portion might be visible in one of the broader OIII's, I would definitely not recommend one for use on that object. I saw a little improvement from my driveway on the Merope fan using the Orion Ultrablock narrow-band filter in my 10 inch Newtonian, but not much with a "true" OIII. However, the narrow-band view does not usually match the brightness seen in broad-band filters or without a filter under dark sky conditions. Clear skies to you.

#53 Sasa

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Posted 13 December 2012 - 05:55 AM

From my yellow zone observing location, I pretty much always see nebulosity around the Pleiades. My impression is more that of high level atmospheric haze than fogged optics (which tend to uniformly cover and fog the entire field of view). Sometimes when I will check other bright stars in the area, I find nebulosity (or haze) around them and sometimes I don't. This threw me for awhile until I finally decided that on really clear days, I had to be seeing the nebulosity and on those days of lesser transparency, I was probably just seeing the haze or possibly a combination of the two. I also would like to say that I found Sasa's drawing to be quite good. Although drawing negative space is not a new concept, it seems to have been applied very well to this drawing. As for seeing details that aren't really there, that is to be expected when one is trying to stretch the limits of seeing beyond that which is readily apparent. My guess is that if this exercise were repeated over a number of observing sessions, the details would eventually take care of themselves. If nothing else, it appears to be a very effective way to enhance one's ability to see.


Yep, these are exactly the reasons why I tried to make the sketch. It forces you to make your mind and try to decide what is real and what to put down on the paper. At the end it sharpens the observer's ability to see, as you said. Also repeating the exercise is important. BTW, this was my second try, the first one (through 80mm scope) looked like: this. Unfortunately no more tries, there was no decent sky for DSO observing for last two months! There was always strong atmospheric haze which makes observing M45 nebulosity pretty much hopeless.

The negative concept is definitely not knew. But at that time, it was a "discovery" for me. Later on, I read for example, that O'Meara recommends similar approach for M45 in his book about Messier objects.

#54 Feidb

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Posted 13 December 2012 - 10:07 AM

As David points out, a true O-III doesn't help the nebulosity. When I tried both of mine, a 1 1/4" and 2" from different manufacturers over several decades, only one time did the one help just a tad on one night (I think it was the 1 1/4"). Most of the time, even that one blocked more than helped the nebulosity. The naked eyepiece worked better.

#55 Starman81

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Posted 13 December 2012 - 01:51 PM

I viewed M45 in the EON 80 with the XW 10 last night (50x, 1.4* TFOV) in my backyard (mag ~4.8 NELM that night) and I saw some haziness across the entire FOV. M45 was quite high in the sky as the time was past midnight. I turned the scope to the OC M41, which is much lower in the sky and did the view was clear with no haze at all. Did I see the nebulosity? I think so!

#56 northernontario

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Posted 15 December 2012 - 01:14 PM

I have seen the striations of nebula a few times. Most nights it is visible with my 16 inch reflector. I seen the nebula faintly with my 6 inch refractor as well.

But the most outstanding view was with my 8" SCT on a cold, crisp transparent January sky a years ago.

Aperture is king, but sky conditions are equally important.

On another note...when all the stars you view look like there is nebula around them....it's time to go in...or get the blow dryer.

jake

#57 blb

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Posted 15 December 2012 - 03:24 PM

On another note...when all the stars you view look like there is nebula around them....it's time to go in...or get the blow dryer.


Even when there is no fog around any other star? I have been out many nights when there appeared to be no haze around any stars only to look at the Pleaides and see haze around the four or five brightest stars in it. I do not wont to go in then.

#58 northernontario

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Posted 15 December 2012 - 03:44 PM

Hi Buddy

I meant stars other than the ones in the Plaides.

I too, am very stuborn when seeing is good.

Even if it's a work night.

jake






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