Cassiopeia Observatory

Mercury, Critters, DSO Observing with OIII Filter,
Rising Waning Gibbous Moon
Posted: 27 June 2013

Another warm day in Oracle, as seen on the right from my weather station. Tucson (about 2000' lower in elevation) is forecast to be 113°F this Saturday.

The observatory was opened Wednesday, 26 June 2013, at 1832 MST, 105°F. The sky was clear, with an occasional breeze blowing. I first did a check on the dome weather stripping in anticipation of monsoon storms starting up, possibly next week. All was good.

At 1846 MST, viewed Venus, 83X. A very slight gibbous phase was visible. Then slewed to Mercury. At 83X, the crescent phase was visible but difficult to see against the bright sky about 50 minutes before sunset. At 1857 MST, I switched to a 1.25" 15mm eyepiece (133X). Mercury was too faint to use to focus, so went back to Venus to focus the eyepiece. At 1901 MST, finally saw Mercury again, this time at 133X. A difficult object.

This image, generated by the US Naval Observatory "Apparent Disk of Solar System Object" web page, shows the phase of Mercury as seen in the telescope:

This next image is a single frame from an iPhone 4 video recording, afocal 133X. Mercury is arrowed. The inset is a magnified and edited image of Mercury from the same frame showing the crescent phase.

At 1921 MST, I noticed that while viewing Mercury, it was so faint and low contrast against the bright western sky, that if I looked away from the eyepiece, it would take a couple of seconds to re-acquire it when I returned to the eyepiece. Mercury is definitely a difficult object to see and photograph now. At 1925 MST, with the sky a little less bright, Mercury was slightly easier to re-acquire. At 1935 MST, Mercury was now into the tree branches.

Slewed to Saturn. The view at 1942 MST, a couple of minutes after sunset, was very good at 133X. Switched to 364X, but seeing was not quite good enough for that much magnification. Switched to the 2" 9mm 100° eyepiece (222X). That was a much better view of the planet and Ring System. At 2004 MST, four moons were visible against the still bright sky: Titan, Rhea, Tethys, and Dione.

Beginning at 2025 MST, I started doing some Deep Sky Object (DSO) observing, 83X. First was the Omega Centauri globular cluster, low in the southern sky. It was just visible in the bright sky of twilight. Astronomical Twilight would not end for another 50 minutes. Next viewed was M4 (globular cluster), also just barely visible. I then viewed M57 (Ring Nebula), high in the eastern sky and nicely visible. Next were the globular clusters M13 and M92 in Hercules.

At 2028 MST, viewed Epsilon Lyrae ("Double-Double" star), 83X. The secondary stars were easily visible at 83X.

I began a tour of DSOs in the constellation of Draco at 2055 MST. Viewed NGC4236 (large spiral galaxy; added to imaging list), M102 (galaxy), and NGC6543 (Cat's Eye Nebula; planetary nebula).

By 2100 MST, I had not seen any Kissing Bugs. They previously had been first appearing between 2000 and 2030 MST. I had decided to stay in the observatory this night until I saw the first one.

I took a short break for the observatory 2118-2133 MST. When I returned I began observing some diffuse nebula in the constellation of Cygnus. I compared the views of the nebula at 77X, with and without an OIII filter. The Crescent Nebula (NGC6888) was visible without the filter, but was more easily seen with the filter. The crescent shape was apparent when using the OIII filter. The Veil Nebula (NGC6960), which was larger than the eyepiece field-of-view (FOV), was faintly visible without the filter. But with the filter the Veil Nebula was easily seen as a long and curving thin nebula with lots of structure and changing brightness. A very nice view with the OIII filter. I then viewed the Pelican Nebula (IC5067); it was faint without the filter and invisible with the filter. NGC6992 (larger than the eyepiece FOV), was faintly visible without the filter, but a great view with the filter. It appeared somewhat similar to the Veil Nebula. IC5146 was faintly visible without the filter, but invisible with the filter.

I switched to a 1.25" 40mm eyepiece (50X) and viewed the Crescent Nebula, Veil Nebula, and NGC6992 using the OIII filter. All three nebula were very nice views with the low magnification, wide field-of-view eyepiece.

At 2206 MST, viewed M20 (Trifid Nebula), 50X. Good view without the OIII filter, but faint with the filter. M17 (Swan Nebula), 50X, was nice without the filter, but was really nice with the filter. It was almost glowing when viewed using the OIII filter. M16 (Eagle Nebula), 50X, was faintly visible without the filter, but with the filter it showed a large and distinctive shape. Very nice view with low magnification and OIII filter.

At 2211 MST, the eastern sky was beginning to brighten from the rising waning gibbbous moon. I switched back to the 26mm eyepiece (77X) and viewed M16, M17, and M20 using the OIII filter. M16 and M17 were nice views with the filter; M20 was just OK.

At 2222 MST, switched to the 2" 9mm eyepiece (222X) and viewed M20. Some structure was visible using averted vision. M17 showed lots of details. M16 was not visible at 222X.

Switched to 83X and at 2238 MST I viewed the small globular clusters NGC6934 and NGC7006.

At 2254 MST, I noticed that some clouds had appeared in the eastern sky. Clouds not been in the forecast for this night. The moon had not yet appeared over the hill to the east.

At 2320 MST, the clouds were getting higher in the eastern sky, almost seeming to rise with the rising moon. I took these photos (cropped) with the D7000 DSLR, f/8 and f/5.6, 1/250sec, 300mm, ISO 400, showing the moon through the clouds and tree branches as it rose over the hill to the east:

The observatory was closed at 2345 MST, 76°F. No Kissing Bugs were seen this night. I don't know if this was because the temperature was too warm, the mitigation efforts of removing pack rat nests near the observatory were finally successful, or if the Kissing Bug season is over for this year.

A new feature has been added to the main "Reports" page. If you expand the "Past Reports" section, you can now click on a year label to see a listing of all reports for that year.

Comments are welcome; use the Comments section below, or you can Email Me. Thanks.