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Re: (IAAC) Obj: NGC 6822 - Inst: 12.5" f5 Dob
Lew Gramer wrote:
> Thanks for the interesting comments about Barnard's Galaxy, Bruce! I have never
> taken the time to explore the constituent objects within n6822 myself - sounds
> like a great project. And thanks for the link to Jim Shields' *EXCELLENT*
> deep-sky Web pages! I'll be exploring them for a while too. :)
>
> BTW, the general rule of thumb (now almost cliche) among deep-sky observers, of
> using higher magnification to increase contrast, may not be TOTALLY appropriate
> for certain objects like this one... I note in a previous log that the optimum
> magnification for perceiving this large, low-surface-brightness object AS A
> WHOLE, was extremely low.
>
> In fact, using higher powers (and thus a narrower annulus of sky around the
> object) actually made it impossible to see! Of course, the HII regions, bar, OB
> associations, and other gross features (including resolved stars) will only be
> accessible at much higher powers. But to perceive this object in its full
> beauty - as E. E. Barnard originally did - do not be too overcome by the
> current craze to view everything at 200x or above. Instead, try a variety of
> filters, magnifications, and *apertures* (including binoculars!) to see what
> YOU perceive as the best view...
>
> Well anyway, here's an observing log I posted to IAAC last year:
> http://www.tiac.net/users/lewkaren/netastrocatalog/msg00237.html
>
> Note the mention of brighter direct-vision details - good targets for detailed
> viewing with much higher magnifications and larger apertures. Also keep in mind
> what I neglected to mention - that attempts to see the same view with a higher
> power eyepiece (12mm Nagler, 45x) failed...
>
> What are the experiences of some of our deep sky mavens on the list, with this
> grand-daddy of the Low Surface Brightness galaxies?
>
> Lew
Lew Gramer wrote:
> Thanks for the interesting comments about Barnard's Galaxy, Bruce! I have never
> taken the time to explore the constituent objects within n6822 myself - sounds
> like a great project. And thanks for the link to Jim Shields' *EXCELLENT*
> deep-sky Web pages! I'll be exploring them for a while too. :)
>
> BTW, the general rule of thumb (now almost cliche) among deep-sky observers, of
> using higher magnification to increase contrast, may not be TOTALLY appropriate
> for certain objects like this one... I note in a previous log that the optimum
> magnification for perceiving this large, low-surface-brightness object AS A
> WHOLE, was extremely low.
>
> In fact, using higher powers (and thus a narrower annulus of sky around the
> object) actually made it impossible to see! Of course, the HII regions, bar, OB
> associations, and other gross features (including resolved stars) will only be
> accessible at much higher powers. But to perceive this object in its full
> beauty - as E. E. Barnard originally did - do not be too overcome by the
> current craze to view everything at 200x or above. Instead, try a variety of
> filters, magnifications, and *apertures* (including binoculars!) to see what
> YOU perceive as the best view...
>
> Well anyway, here's an observing log I posted to IAAC last year:
> http://www.tiac.net/users/lewkaren/netastrocatalog/msg00237.html
>
> Note the mention of brighter direct-vision details - good targets for detailed
> viewing with much higher magnifications and larger apertures. Also keep in mind
> what I neglected to mention - that attempts to see the same view with a higher
> power eyepiece (12mm Nagler, 45x) failed...
>
> What are the experiences of some of our deep sky mavens on the list, with this
> grand-daddy of the Low Surface Brightness galaxies?
>
> Lew
Lew,
My best views of NGC 6822 have been through a 20" f/10 classical Cassegrain (127x)
and a 32" f/4 Dobnewt (x?). The HII regions were quite apparent in both cases.
Dave Mitsky
References: