by Randy Muller
Six and a half months ago I finally gave in and ordered an 18" f/4.3 Starmaster dob. I had been wanting a large dobsonian for a couple of years, but had decided to wait, to grow into the scopes I had. Using other peoples' large scopes showed me just how much more I would be able to see in a 16 or 18 inch than I can in my 10 inch.
Finally, viewing several fields full of faint galaxies in Mark Wagner's scope and viewing Thor's Helmet and some amazing, but faint planetary nebulae in Steve Gottlieb's scope at Fiddletown, CA on a magical night in December convinced me I needed to move on a bigger scope, and I ordered it two weeks later.
I had narrowed the choice down to Obsession, LITEBOX and Starmaster dobs. I eliminated Obsession on the basis that the mirror is not really designed to be easily removable. I then eliminated the LITEBOX because I didn't like the potentially bad thermal properties of a closed mirror box.
I'm no expert in modern dobsonian construction, and I certainly did not evaluate every aspect of these three brands before purchase, and I may have made mistakes in the features I did evaluate, but I have had experience with unwieldy scopes and scopes with bad thermal properties, and I wanted to avoid these problems at all costs.
As it is, I doubt I could handle a larger scope than this.
The massive dob arrived on Wednesday, July 12 in 8 boxes, and I spent several hours unpacking them and doing some minor assembly. I had already decided to name the scope "Pleione", the mother of the Pleiades, and, to me, the Mother of All Scopes. Unpacking boxes which contained other boxes to unpack, and the ability of the secondary cage to fit into the mirror box for compact transport also reminded me of those Russian nesting dolls, called "Matryoshka" dolls. The word is derived from the word for mother with a couple diminutive and affectionate suffixes added for effect. So I may also call this scope Matryoshka, and I may also refer to it as the Humungous Feller.
Before I knew it, it was getting dark and I wasn't quite ready to go, so I left First Light for the evening of Thursday, July 13.
The scope went up quickly, and I used wheelbarrow type handles to roll the scope out the front door (since it wouldn't fit out the back door), and around the house to the backyard of my Roseville, CA house.
After assembling the trusses and erecting the scope, I collimated it. It was far easier to collimate than my 10". The adjustments could be made by hand, instead of with tools, and everything was centered better and well built, compared to my 10", where nothing is properly centered, and nothing is well built. It's a wonderful feeling to use a piece of well designed equipment that works as designed.
Actual first light came when I pointed at Spica to collimate my Telrad. Even though it was fairly low shortly after 9:30, it was pretty steady and showed a beautiful ideal (for a newtonian) pattern. I was a little surprised at how small it was, compared to what it would have looked like in my 10".
Next, I decided to see how Epsilon Lyrae, the famous Double Double looked. Using a 26mm eyepiece giving 76x, I could see that each component was double, but there was no dark space between them. Using the 10mm eyepiece at 197x, the components were easily split.
I moved on to faint stuff. Well, bright stuff which is hidden by much brighter stuff (the moon and light pollution). I searched in vain for M51. I really wished I had a finder. I guess I will put one on soon.
I then moved to the field of M109, a galaxy that I was use as a test object for transparency in my 10". I couldn't see it. I could see the field, but it wasn't there. Part of the problem was that I was looking through a tree, so my effective aperture may have been close to, uh, 10". At this point, I remembered why I don't observe much from my backyard anymore.
I took a look at another wide, bright double, Cor Caroli, aka Alpha Canum. I was surprised to see color in the dimmer component: A dim golden yellow. I don't recall seeing this before.
I looked at M94 while I was in the neighborhood. I was surprised to see detail in this very bright galaxy. I could even see a diffuse halo around the bright and highly concentrated center.
Pleased that I finally saw a galaxy, even though it was a bright one, I moved on to the fabulous Ring Nebula in Lyra, M57. My jaw dropped as I appreciated newfound beauty that I had never seen before. It seemed like there was elusive detail in the ring, and I had a sense of bluish color in my 7.5mm (262x) eyepiece.
Eager for more color, I went automatically to Albireo, the gorgeous big, bright, blue and gold double which is the head of Cygnus the Swan.
I decided to try for some faint galaxies in Bootes, to see what I could see. I began with a double star, STF 1825 (aka ADS 9192), near Arcturus, because it was there. At 4.3" it was much wider than the Double Double, but had a nice color and brightness contrast, with one bright yellowish component, and a smaller, dimmer, grayish-bluish component.
At this point, I slipped in the Paracorr coma corrector, to see if it improved the views any, and it certainly did. I hate coma, and at f/4.3, this scope has a lot more coma than my 10" f/5.6. The corrector raises the f/ ratio by a factor of 1.15x to nearly 5.
I hunted down NGC 5513, a faint galaxy just less than a degree away, which I had observed for the first time at Lassen last month. It has a B magnitude of 12.6, and was not even that hard to see, in spite of light pollution and the moon.
I decided to try for a fainter one: NGC 5332. I could barely make this one out as a very small, elusive diffuse spot, extremely faint and at the limit of my observation powers. This one has a B magnitude of 12.9. 12.9 from my backyard! What was impossible with a mere 10" is now possible, though difficult with an 18".
After spending quite a bit of time on those faint guys, I finished with M73, a relatively sparse and faint globular cluster. Faint, that is, for a Messier glob. Compared to what I had been viewing, it was a beacon showing logts of detail and resolved stars in front of a background glow.
I then scanned the Milky Way (invisible to the naked eye) for a while, and then packed up. I never did look at the moon. Oh well.
I was very pleased with the performance of the scope, and how well it works. I don't really know how to evaluate optics, other than what I see in the eyepiece, and what I saw was excellent. I am pretty sure that the weak link in my optical chain is now my eye pieces, which are Orion Sirius Plossls.
Compared to my 10", however, this new scope is a bear to set up and take down. But the view in the eyepiece is well worth it. I can't wait to bring it to Lassen.