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Dust lane in NGC 5866 ("M102")?

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#1 IVM

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Posted 18 May 2013 - 10:49 AM

Steve O'Meara draws it long and sharp with his 4" under Hawaiian skies, and Ronald Stoyan draws it bold and black with his 14" somewhere in the Alps. I have now tried many times and spent quite some time on it, but never seen more than a hint of a subtle dip in brightness near the center of the bulge, which might be illusory.

I used my 16" and magnifications up to 730x under dark enough skies (21.6-21.7 mag/sq arcsec by SQM-L). Generally we don't get good seeing, but I tried in decent enough conditions, when at least distorted Airy disks showed.

Has anyone here seen it? What conditions do you need to really see it? Apart from being transported in time and space to stand with Lord Rosse at the focus of his shiny new 72" mirror.

#2 deepskydarrell

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Posted 18 May 2013 - 03:08 PM

I saw it in '09. The seeing was quite good and SQM 21.54. Uranometria's Deep Sky Field Guide made no mention of any dust lane so I wasn't prepared for what I saw: "3' long at 203X, not average oval but a bit like a Cowboy Hat with a brighter crown and darker band and maybe lighter brim." I was impressed with the view and gave it "!" in my notes.

Thanks for bringing it up. I'll definitely give it another look with the new optics. Should be hoot.

Lately I've had quite poor seeing and the usual suspects (showpieces) with dust lanes were quite obscure, -- the same with Cassini's division those times. So I suspect that seeing is an important factor with this dust lane.

Didn't Ross have to refigure his speculum metal mirror each time he repolished it or did he have a glass mirror? You'd wonder if our figures are more accurate today and reveal better contrast than his light bucket.

DSD.

#3 IVM

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Posted 18 May 2013 - 04:26 PM

Thanks, Darrell.

It was a speculum, and I wondered the same.

#4 deepskydarrell

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Posted 18 May 2013 - 06:35 PM

Leon Foucault's Test was only announced in 1858 and so Rosse could only have had access to that in his last 9 years if at all. But he could have used a star test.

DSD.

#5 David Knisely

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Posted 18 May 2013 - 11:20 PM

Steve O'Meara draws it long and sharp with his 4" under Hawaiian skies, and Ronald Stoyan draws it bold and black with his 14" somewhere in the Alps. I have now tried many times and spent quite some time on it, but never seen more than a hint of a subtle dip in brightness near the center of the bulge, which might be illusory.

I used my 16" and magnifications up to 730x under dark enough skies (21.6-21.7 mag/sq arcsec by SQM-L). Generally we don't get good seeing, but I tried in decent enough conditions, when at least distorted Airy disks showed.

Has anyone here seen it? What conditions do you need to really see it? Apart from being transported in time and space to stand with Lord Rosse at the focus of his shiny new 72" mirror.


I have seen hints of it at over 200x in my 10 inch Newtonian, but the lane appeared with quite a bit more certainty in my 14 inch f/4.6 Newtonian at similar magnifications (230x to 384x). It takes really stable seeing to pick it up, as it is quite narrow and low in contrast. Even slight seeing variations are enough to make that narrow dust lane vanish. Even when visible, it takes some aperture to make it show up well (the first time I got to see the dust lane was in an 18 inch). Clear skies to you.

#6 IVM

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Posted 19 May 2013 - 11:11 AM

Thank you, David. Sometimes in summer we get really good seeing; maybe that will do the trick for me.

#7 Laurent Ferrero

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Posted 20 May 2013 - 03:04 AM

I hardly saw its dust lane last month in my 15 ", just in the central region. This is not an easy detail ...

This is my sketch :

http://splendeursduc...s-au-beau-fi...

#8 IVM

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Posted 20 May 2013 - 09:49 AM

Nice sketch, Laurent.

#9 Laurent Ferrero

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Posted 20 May 2013 - 04:13 PM

Thank you IVM !

I remember that the thin dust lane of M102 was only visible at very high magnification.






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