Tuesday, November 08, 2005

20051107 - M1 & the Milky Way

Session name: 20051107.2000

From our open observatory at the top of the lawn, not all nebulae type have equality. The various bright diffuse nebulae suffer most from our bright sky background which I estimate to be around 19.5 mag/(arc second^2). Having tried for M1, a supernova remnant from 1054, unsuccessfully a number of times with the Tak102 and TP-10, it wasn't on my target list until Ben had mentioned it. I shrugged off the idea to go for it, but since I was in the neighborhood observing
NGC1647, what the heck.

Following the classification for nebulae types that Erich Karkoschka outlines in his
atlas they are listed by increasing difficulty:
Open Clusters, Globular Clusters, Planetary Nebula, Galaxy, Diffuse Nebula

These bright diffuse nebulae, excluding M42, can be very difficult to detect and observe. Even M43 or M8, the Lagoon Nebula, prove difficult. Even more difficult are supernova remnants (SNR), which Karkoschka classifies as filamentary supernova remnant, the likes of M1, the Crab Nebula and NGC6960/6992, parts of the Cygnus Loop.

Under dark sky I've seen this "pea-sized" object in the same fov with zeta Tau in the Pentax XW 40mm eyepiece; a fov about 2.3° with 32x magnification; however, as expected, it was not to be seen at all. I swapped the EP to a Nagler 17mm, 1.1° with 75x magnification. I was shocked to sense a very large and very, very, faint object in the area. At 75x, the surface brightness was so faint that it barely provided enough contrast to be detected. It best appeared with averted vision and scope shake. Under higher power, the contrast improved considerably, where M1 held up to direct vision, and I sensed a brightening along the following edge (eastern side). Both Ben and Charlie observed it, with Ben stating confidently that he saw it and was just as impressed by the size. I am not certain if Charlie saw it. He described its location properly at 75x, but was not confident he saw it under the higher powers.

We completed the observation by changing focus to a nearby bright star that turned out to be the double STF 742. Information from Cartes du Ciel states the magnitudes as 7.09/7.47 and the separation and position for epoch 2000 at 4.0"/273°.


Earlier in the evening, we were talking about John Pazmino's sighting of the Milky Way. I brought up again the topic of seeing it with bins or a scope in Cassiopeia. Ben's novae hunting search areas are in the band and he never mentioned seeing or sensing it. We played around in the square of Cas, noticing both
NGC225 and, NGC129. The sky was "milky" white, not really granular as it was faintly pixilated across the field.

To contrast what we were seeing in that area, we swept the scope to another area without aid from an atlas to see if we could detect the absence of this brightness. We both agreed on an area northeast of eps Cas where we could almost isolate a border where the sky changed. Ben noticed another cluster and left it in the EP. Another pleasant surprise - he left
Trumpler 1, a small open cluster with a conspicuous double, when observed at 75x or higher.

I find it interesting to note that NGC225 is a nearby cluster within our local arm, also called Orion-Cygnus Arm, NGC129 is located in the inter-arm gap between our arm and the next further outlying Perseus Spiral arm. Lastly, Tr1 is situated in the distant Perseus Arm, nearly 11,000 ly away. It turns out that M1 is also within the Perseus Arm, and it is a good head turn away from Cassiopeia. It’s a treat to benefit from the efforts of others who rose to the challenge of discovering the structure of our