I Zw 18 aka UGCA 166

So popular in the science scene so rare observed in the amateur scene - I Zw 18?

Last new moon period I tried this unusual young and active dwarf irregular galaxy. With the 27-inch the galaxy was visible without problems with direct vision at 586x-837x. Seeing was only average. The brighter knot was easy to detect but the fainter one (~5" distance) was tough and only pops in and out of view. I could not see the companion galaxy 30" NW.

What are your experiences with this fuzzy guy? Could anyone catch the companion, Jimi?

HST - ESA/STScI
Attachment 1404

SDSS (~3'x3')
Attachment 1405

sketch: 27", 586x-837x, NELM 7m+, Seeing III
http://www.deepsky-visuell.de/Zeichnungen/UGCA166.jpg

A quite faint target indeed, Uwe ! Could you give us an estimate of the visual magnitude of each component ?

I've viewed I Zw 18 in my 18-inch a few years ago, but it was just a very faint glow, slightly elongated NW-SE, ~20"x15", located just 0.6' west of a mag 15 star. The fainter component was not seen (or resolved) at 280x. I'm guessing the V mag of the main component is close to 16.

Simbad only gived the V magnitude of the brighter component: 15.98.


Clear skies,

Wouter

The SDSS DR9 tool gives a visual magnitude of ~16.5 for the brighter component and ~17.5 for the fainter. The companion galaxy is shown at magnitude ~19.7.

16-16,5vmag/17,5vmag fits into the observations of Steve an me. 19.7 looks a little bit hard for the 30-inch class.

The object remembers me of the view of the Footprint M 1-92 through a 12-inch telescope, pretty the same knot situation.