Although Sunday(9-16)evening at Mt Pinos was a bit of a challenge with poor transparency coupled with good seeing at a SQM reading of 21.15, I did enjoy observing a number of objects including an elusive planetary in Cepheus. The Observer's Guide notes NGC7139 has an angular diameter of 47', roughly the same size as Jupiter. It appeared quite a bit larger in my 16" f4.5 dob when I used my 14mm ES 100 AFOV eyepiece, together with a paracorr. I did need several attempts to find it as it doesn't stand out at magnitude 13.3. I found an O111 filter helped quite a bit and I had just put my Lumicon O111 filter away so I grabbed my Celestron 0111 near my fingertips and placed it in front of the eyepiece and immediately noticed an improvement. I think the shear size of the planetary is a bit of a surprise, here's Skyhound's take on it:
http://observing.skyhound.com/archives/sep/NGC_7139.html
I found it more challenging than the account in the aforementioned link, probably due to less than optimum transparency. Clouds, not predicted by either NOAA or the clear sky clock, persisted for awhile after sunset and likely contributed to poor transparency. Nevertheless, I doubt this object would be visible in a four inch scope, and questionable in a six, despite what skyhound says. The Observer's Guide notes it is difficult in a 8"/10" scope. I'd like to know what others think about it...
http://observing.skyhound.com/archives/sep/NGC_7139.html
I found it more challenging than the account in the aforementioned link, probably due to less than optimum transparency. Clouds, not predicted by either NOAA or the clear sky clock, persisted for awhile after sunset and likely contributed to poor transparency. Nevertheless, I doubt this object would be visible in a four inch scope, and questionable in a six, despite what skyhound says. The Observer's Guide notes it is difficult in a 8"/10" scope. I'd like to know what others think about it...
