I'm back from seven days at the Oregon Star Party 2014. Hot, hungry, and tired but well worth it! So I'm deviating from my usual .NET blog posting to highlight the trip and show some sketches of interesting deep-sky objects. First the optics: I have a 14-inch f/4.6 reflector on a standard Dobsonian mount. The focal length is 1.65m. I stick to these three eyepieces for about 95% of my viewing:
|Eyepiece||Focal Length||Mag||Apparant FOV||True FOV|
|Nagler Type 5 (2-inch)||31mm||53X||82 deg||1.45 deg|
|Nagler Type 4 (2-inch)||17mm||97X||82 deg||0.84 deg|
|Nagler Type 6 (1.25-inch)||9mm||183X||82 deg||0.43 deg|
I was working off of an observing list. I've come to appreciate double stars over the years and I was able to split several with little difficulty. For example Gamma 2 in Delphinus, 17 Draco, and 95 Hercules could be split at 97X or less. But I struggled for quite some time with Zeta 1 in Aquarius. I threw the 9mm on it (183X) to no effect. It was early evening around 22:00 so I thought maybe my mirror hadn't cooled down yet. The next night I had the same problem. When I saw that the stars had a 2.3" separation I knew this was going to be trouble. So I put a 2X Barlow on it and then at 366X was I able to see it. Just barely.
I spent a few hours on some obscure galaxies in Ursa Major (along with Virgo which is also away from the Milky Way UMa has a ton of galaxies). About a degree from M81 and M82 is NGC 3077. I sketched it at 97X because I could make out a core and that's not always possible unless the seeing is really good. And in the high desert of the Ochoco Mountains at 5K feet the seeing this week was extraordinary. I rated it and transparency a top 1 on the Antoniadi Scale. So on to NGC 5473, a very feint mag 12.4 galaxy in UMa that is about 2 degrees from M101. I couldn't make out a strong core but I could tell it was face on. Some others like NGC 5474 (mag 11.5) were so faint all I could do was look for the hint of a wispy gray elliptical shape.
Several planetary nebulae gave me a heap of trouble. I thought I saw NGC 6803 in Aquila (Aql). But a friend told me that it was about 3 arc seconds in diameter against a backdrop of low-magnitude stars that were 1 or 2 arc seconds. This just pushed beyond the limits of what my scope (and my eyes!) can see. So that was a bust. But with a lot of persistence I did see IC 3568 (the so-called "Lemon Slice" nebula) in Camelopardalis (Cam). Even at 183X it looked like little more than a few grains of sand. If I had enough aperature I suppose it might look like a lemon slice!
I also forced myself to sit and sketch open clusters this time. (From the wiki: "An open cluster, also known as galactic cluster, is a group of up to a few thousand stars that were formed from the same giant molecular cloud and have roughly the same age.") They're not my favorite deep-sky object. I usually don't have the patience to study the star patterns and sketch them accurately. But I found after looking and sketching several of them it forced me to slow down and really enjoy these wonderful objects. I think I have a new appreciation for them.
So here are four sketches in no particular order. Why old-school sketches and not photos? Sketches show you exactly how the object looks through the eyepiece. I find that real. Photos look amazing but they also lie. Beginners who look through a telescope for the first time expect to see Hubble photographs and are sometimes disappointed by the faint wisps of smoke from objects millions of light years away. The problem is our eyes did not evolve to see color so easily. The retina has cone cells for seeing color. But before they can be stimulated the object has to have a sufficient surface brightness to trigger them. That's why you can see a red ball during the day but you don't know what color it is when it's getting dark. A camera shutter can stay open for 30 minutes and gather enough light to resolve color in the Dumbbell Nebula (about 1.3 thousand light years away). But no matter how long you stare at it through the telescope with the eye you cannot see color. There's only so many photons your eye can take it at once.
M27 (Dumbbell Nebula)
M33 (North is to bottom)
M57 (Ring Nebula)
NGC 6751 (PNe)