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GavStar

Night vision on reflection nebulae (M42 and running man)

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Posted (edited)

In the recent night vision thread there were some comments about whether night vision works with reflection as well as emission nebulae. This was as a result of some recent posts by @alanjgreendescribing observing the running man nebula with his night vision setup.

It’s pretty clear to me based on my observations and understanding (and also numerous comments and observations on cloudynights) that night vision does not work on reflection nebula. This is because the sensitivity of the night vision devices in the blue end of the light spectrum is very low compared with the red sensitivity (even for the photonis intens tubes which do have slightly larger band sensitivity than the Gen 3 tubes).

However although classified as a reflection nebula, the running man has some red emission nebula within it as per this link

https://www.space.com/amp/40649-running-man-nebula-photo.html

M42 does not make good night vision phone photos because the core is so bright it just blows out completely if you want to get the surrounding nebulosity. It’s one of those times when your eyes are much better than a camera since the detail shown visually is incredible. At the recent London star event, M42 was what virtually all new NV observers ( @DirkSteele excepted ?) kept coming back to because it shows a lot even from extreme light polluted sites.

I haven’t shown this phone photo of m42 before. It was taken from a darkish site on the Isle of Wight in October last year (sqm 21.0). It’s not a pretty photo due to the core being blown out but it does show the fainter bits of the nebulosity at the edge.

And in particular you can see parts of the running man nebula. I’m sure these are the red emission nebula within the running man that the night vision monoculars can pick up (with the blue bits remaining invisible).

Hope this post has been useful.

6B673CE7-020A-4EE1-9CD0-359158ACB597.jpeg

PS my title is not inferring that M42 is a reflection nebula btw - a bit poorly worded from me!! ?

Edited by GavStar
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Posted (edited)

I have spent many hours on the Running Man over the last three months and it is possible to see the "black trousers" but not all at once. You need more magnification than that provided by the 55mm plossl and you need to work a section at a time. After a few attempts I made a "map" based on my sketches and images online...

rm2.jpg.70df45a03271e0a92b5c314dec05f4d9.jpg                                                                                                                         

Here is my sketch (made at the 20" scope) from a session on 1st Feb...

rm1.jpg.6345bef8e2171e65be5d2dce73abc8fc.jpg

I think that I can get more from it next year now I have learned a few pointers and the fact that the 35mm panoptic and 27mm panoptic can help reveal more black features.

Its the middle and south side that are the hardest to get much out of. You need to spend time at the eyepiece and plenty of averted to get anything from the south and east. The north section (in the stars) is pretty easy as is the western curve and the black finger coming in above the north.

I will be better prepared earlier in the season in 2019 (but thats what it is all about) to try to get more....

Alan

Edited by alanjgreen
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Posted (edited)

Be interesting to try some only reflection nebs, eg Pleiades or witch head. You take much better notes than I do Alan! Might be worth adding a B-filter to remove the red, and any “light pollution” in the more sensitive band.

Peter

Edited by PeterW
Addition

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45 minutes ago, PeterW said:

Be interesting to try some only reflection nebs, eg Pleiades or witch head. You take much better notes than I do Alan! Might be worth adding a B-filter to remove the red, and any “light pollution” in the more sensitive band.

Peter

I spent part of a session on the Witch Head and I was able to trace the outline easily - it was pretty large in the dob. I was using the Chroma Ha filter. But there is nothing seen within the boundaries and of course an OIII filter made it much worse.

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Posted (edited)
1 hour ago, alanjgreen said:

I spent part of a session on the Witch Head and I was able to trace the outline easily - it was pretty large in the dob. I was using the Chroma Ha filter. But there is nothing seen within the boundaries and of course an OIII filter made it much worse.

If you were using the chroma Ha filter then you were only seeing ha emission for the witch head (of which I guess there may be some albeit very limited) but any of the blue reflection light will be completely filtered out by the chroma filter.

How was the view of the witch head with normal glass?

Edited by GavStar

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Posted (edited)

Right, although having previously stated that I have "left the building". I just read the great enjoyments perceived by @scarp15 at my supposed "discredited" view of the Witch Head and my blood is boiling!

I saw and traced the whole outline of the Witch Head with the 20" using a 55m Plossl and a 5nm Chroma Ha filter - its written in my notes for 8th Jan 2019. I was able to follow the same outline on Sky Safari using the ipad at the same time to confirm it. This counts as seeing it in my book!

My notes do not say what I saw unfiltered so I must not have tried unfiltered or saw nothing.

If you choose to think that "I made it up just to get one over on you" then I dont have words to describe my contempt!

Its clear that my reports are just cannon fodder to some people and I think its pathetic that I am unable to post my OBSERVING REPORTS in a section called "Observing Reports" (If its not for observing reports then please rename it to something else).

This situation is so lame that I am lost for words.

Goodbye!

Alan

Edited by alanjgreen

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36 minutes ago, alanjgreen said:

unable to post my OBSERVING REPORTS in a section called "Observing Reports"

I would have thought that they would go in the most appropriate section.  Most likely Deep Sky, Wide field or Reports.

As long as the title starts with 'Night Vision'..?

Cheers 

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Posted (edited)

I don’t doubt the observation, I’m just slightly surprised as a pure reflection nebulae is broadband in emission (I’ve tried to find a spectrum for one). There may well be light at the hydrogen emission line, but it won’t be bright. The chroma are definitely very good, I was pleasantly surprised by a logarithmic transmission plot that @GavStar showed me, very little out of hand transmission. Also other people have reported failed observations (for which there may be many reasons). Please have a go with other pure reflection nebulae (eg Pleiades, some are emission/reflection combined) and tell us how you get on. The past months have seen people try out new things with many happy discoveries! Let’s keep up the experimentation!

Peter

Edited by PeterW
Correctuon
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1 hour ago, PeterW said:

I don’t doubt the observation, I’m just slightly surprised as a pure reflection nebulae is broadband in emission (I’ve tried to find a spectrum for one). There may well be light at the hydrogen emission line, but it won’t be bright. The chroma are definitely very good, I was pleasantly surprised by a logarithmic transmission plot that @GavStar showed me, very little out of hand transmission. Also other people have reported failed observations (for which there may be many reasons). Please have a go with other pure reflection nebulae (eg Pleiades, some are emission/reflection combined) and tell us how you get on. The past months have seen people try out new things with many happy discoveries! Let’s keep up the experimentation!

Peter

@PeterW @alanjgreen

There is Ha signal in the witch head as confirmed by @ollypenrice in the attached imaging thread 

So well done Alan, great observation ? and one I’d like to try replicate soon.

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11 hours ago, PeterW said:

I’m just slightly surprised as a pure reflection nebulae is broadband in emission

Peter, in my experience there can be emissions from other "objects" ie M42 in this case most likely, that can cause an "objects" border to blur so to speak. This is why I have a hard time in some areas of the sky because there is nebulosity all over the place and to pinpoint the exact named object can be difficult. I wonder if this is the case with the NV obs in the Witch Head area.

Up around IC1318 I can be at a complete loss as to what is what with a few well define exceptions.

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Don’t know about the witchhead, but I have a wide deep hydrogen alpha image of the wider central Cygnus area that I use to help confirm which wisps I have seen. Catalogs are littlenuse as the objwctsbare never simple circles/ellipses!!

 

Peter

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