Ivan Maly
March 28th, 2014, 07:32 PM
Here is a sketch that I made recently with my 12" SCT, observing at ~125-400x. N up, W right, SQM 21.68.
1146
At the lower magnification the galaxy displays what seems to be one-half of a bar inside a halo that it divides into two unequal and unequally bright parts. At high magnification the boundary of the halo is traced by a ring of visually detached faint compact regions. One of them is at the end of the "half-bar", and at the other end is a compact core. The small peripheral regions generally correlate with HII regions that were mapped in this galaxy by Hodge in 1969 or with their groups. Overall the galaxy (Herschel class III and 5' across at 25 Mly) is unexpectedly detailed visually, even though it can take half an hour to find these small enhancements one by one.
P.S. I see some crazy faint magnitudes for these knots in NOMAD. Some visible knots are larger than NOMAD objects, but the one to the W of the nucleus, for example, should correspond to only one very compact object. This knot has no Vm in VizieR, but its Rm is 17.4 and Bm is 17.3. In my memory this was one of the more difficult ones, but still clearly visible without an inordinate amount of effort. If one is to believe these magnitudes (the area of integration used for these measurements could still be smaller than the actual knot, since it was supposed to be a survey of stars), my only explanation could be that the halo background might, hypothetically, make a compact nonstellar knot more visible. It is the opposite with stars and larger features on a diffuse background, but the size may be of importance, as I have noticed previously that the visibility of a faint star may be enhanced on the background of a compact knot.
P.P.S. I am inclined to think these measurements are underestimations for non-starlike objects. The very small round knot in NGC 4248 (the companion of M106) has interpolated Vm ~15.0, and it looked downright bright to me in the same instrument.
1146
At the lower magnification the galaxy displays what seems to be one-half of a bar inside a halo that it divides into two unequal and unequally bright parts. At high magnification the boundary of the halo is traced by a ring of visually detached faint compact regions. One of them is at the end of the "half-bar", and at the other end is a compact core. The small peripheral regions generally correlate with HII regions that were mapped in this galaxy by Hodge in 1969 or with their groups. Overall the galaxy (Herschel class III and 5' across at 25 Mly) is unexpectedly detailed visually, even though it can take half an hour to find these small enhancements one by one.
P.S. I see some crazy faint magnitudes for these knots in NOMAD. Some visible knots are larger than NOMAD objects, but the one to the W of the nucleus, for example, should correspond to only one very compact object. This knot has no Vm in VizieR, but its Rm is 17.4 and Bm is 17.3. In my memory this was one of the more difficult ones, but still clearly visible without an inordinate amount of effort. If one is to believe these magnitudes (the area of integration used for these measurements could still be smaller than the actual knot, since it was supposed to be a survey of stars), my only explanation could be that the halo background might, hypothetically, make a compact nonstellar knot more visible. It is the opposite with stars and larger features on a diffuse background, but the size may be of importance, as I have noticed previously that the visibility of a faint star may be enhanced on the background of a compact knot.
P.P.S. I am inclined to think these measurements are underestimations for non-starlike objects. The very small round knot in NGC 4248 (the companion of M106) has interpolated Vm ~15.0, and it looked downright bright to me in the same instrument.