Dust lane in NGC 5866 ("M102")

[Ivan Maly]

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 could be seen.

Is there any visual trick that brings it out? 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.

[Uwe Glahn]

Ivan,

I could also pick it up. Instrument was a 20" under fairly good but not perfect conditions. Seeing was also good, but not perfect, magnification high, AP around 0,9mm.
When I remember right it was not easy to detect and I needed more that one attempt to see the lane. I only saw the lane in the bulge region.

M102.jpg
20", 543x, NELM 6m3, Seeing II

[Howard B]

Hi Ivan,

I've seen the dark lane with my 20 and 28 inch scopes but it is fairly subtle, and I have seen it split the galaxy from end to end. My notes show I used 413x and 467x for my latest two observations (2001 and 2006) to see it well. I should have another look at 5866 next time I observe to see if I can still see the dark lane as well. Your skies are at least as good as when I made my observations, perhaps better because of altitude, so maybe you've just been unlucky and further observations will reveal the dark lane. Good luck!

[Ivan Maly]

Thank you for your responses. I will try again. Sometimes in summer we get really good seeing; maybe that will do the trick.

[Ron Abbott]

Ivan,
Sorry for the tardy reply, but M-102 is still well placed for observing early in the evening. I have observed the dust lane a number of times. I am using a "pee wee" scope (11-inch SCT), but found this feature to be quite elusive. Seeing it requires a perfect night for both transparency and steadiness. When I HAVE observed it, it was using my 16mm (175X) and 12mm (233X) TeleVue Naglers. The dust lane is very subtle and low contrast, and is best seen with averted vision. On best nights, I could see it across perhaps 2/3 of the visual envelope. Hope this helps.

Ron Abbott
Land of Oz Observatory
http://www.astrolandofoz.com

[Steve Gottlieb]

It appeared fairly subtle in my 24-inch last month in good conditions -- "A very thin, low contrast dust lane bisects the galaxy and is most evident along the central bulging core." This was using just 200x. Hard to image it being sharply defined in a 4"!

There is another challenge here -- NGC 5867 -- which is shown in Uwe's sketch. Here are my notes on this one: "At 322x, NGC 5867 was picked up 1.0' SSE of the mag 12.2 star as a very faint 8" glow, held continuously with averted vision." This small galaxy is probably 16th magnitude. I've seen it in my 18", but it was pretty tough.

[Ivan Maly]

I've made what I'll call a satisfactory observation, although it is really more of a central equatorially extended dip in brightness than an unmistakable dust lane. Thank you for the detailed descriptions, gentlemen.

[Pala61]

I've made what I'll call a satisfactory observation, although it is really more of a central equatorially extended dip in brightness than an unmistakable dust lane. Thank you for the detailed descriptions, gentlemen.

Glad you caught it. Without prior knowledge of photographic suggestion I have detected a dither with my 8". It was peculiar to this galaxy alone. There'd be a fluctuation in light - a confused flicker - then nothing. A photo of course revealed the lane behind the dither. Further investigation of visuals with my aperture via other observers has a gentleman sho actually resolved the lane, albeit, offcenter slightly to one side. I f love to have better sky conditions to detail the dither. It is a nice object, lane aside. Glad you got it.

Pete