Last Saturday night was the initiation of the 12.5" f/5 dobsonian-mounted newtonian that I have dubbed "The Big Guy" (to distinguish it from itıs predecessor, a 6" f/5 dob we constructed as a prototype). This started off pretty rocky, indeed. After spending the last week scrambling to get the scope into a functional, if incomplete, state for its initiation, I had plans to travel to Little Blair Valley (LBV) in Anza Borrego Desert State Park, CA northeast of San Diego with my brother, my woodworking mentor and the co-conspirator in the construction of this scope, Since getting there is a two hour plus drive we planned a 2-3 PM departure time.
I worked on the scope all morning getting together the last essential bits, constructing the spring counterbalance, bolting on the trunions, placing the Quickfinder, etc. Just after noon I took the scope outside for some final adjustments using a target a couple miles away on a hilltop. But alas, I couldnıt bring the thing into focus. After considerable fiddling I determined "something was really wrong". A quick reference to my notes and the e-mails I had exchanged with my brother revealed that we had somehow miscalculated the truss tube length. Fortunately, they were cut too long rather than too short. A half an hour of double checks of the measurements and the math revealed our error. We had used the wrong base length for the equilateral triangle defined by the truss components making the truss tubes almost 2" longer than required. I tossed in the towel. After all, my brother would be arriving to join me at about our scheduled departure time and then we would have to alter and then reconstruct the truss assembly, test it out and only then head out to LBV. However, upon getting to my house he said,"Well, lets cut these things down and get out of here!"
Well, with that spirit I was thrown into action. I immediately disassembled the truss, marked it for cutting and headed into the house to do the final preparations for departure. He cut, drilled and reassembled the truss. We were on the road by 4PM headed for the star party at LBV. Yes, we would at best arrive in partial darkness with an untested scope with radically mis-aligned mirrors but we would make it!
We arrived at LBV shortly after 6 PM in full darkness, lights out. Pulling up to the line of parked cars and unrecognizable faces I stuck my head out the window and said "Anyone know where Paul L. is?" An immediate response of "Yeah, thatıs me" and Paul directed us into the spot heıd saved for us next to him. Yeah, my good buddy, Paul. In reality we had never actually met but had conversed with for half a year over the internet and set up a local discussion group called TAC-South. He was here along with several other members of the TAC-South e-group and had saved me a nice spot along the line of cars, scopes and people making up the star party. Quickly, my brother and I spread the tarp, unfolded the table, set up the chairs followed by our three telescopes. A 4.5" Eq mounted Meade newt, the 6" f/6 dob dubbed "The Little Guy" and our new, somewhat more refined creation, "The Big Guy".
Assembly of the big guy was a breeze because of the one-piece truss assembly and the new improved bracket system my brother had designed and machined. Slip the 4 bottom and four top brackets under the thumb screws and give a twist to cinch down and the OTA is assembled and square. The ebony-star lined trunions floated nicely on the virgin teflon pads of the rocker box restrained by the tension from the spring counterbalance based largely on the system of Tom Kracji. My first rendition of the counterweight will need some revision. The rocker bears a strong resemblance to that of Albert Higheıs beautiful RTMC award winning scopes as do elements of the mirror box assembly. Other inspirations have come from Paul LeFevreıs "Papa Joe" (which was sitting right next to me but I had only seen until now on the internet), the guidance of Berry and Kriegeıs book "The Dobsonian Telescope" and others. The azimuthal motion is a bit sluggish but nevertheless lacks serious "sticktion. That will be easily corrected with a coat of Rain-X on the ebony star.
Quickly popping in the 30 mm Ultima I glanced in the eyepiece and there they were, stars, lots of them. Cranking the JMI NGF3 focuser I could immediately bring them into "focus". The image was fuzzy but the scope had never been collimated and all the fiddling before figuring out the truss assembly problem had left the mirrors severely out of align. The 30 mm was followed quickly by the 8 mm Radian and two Gary Russell SWA eyepieces all of which came into the same fuzzy focus. Yes! We had gotten the truss right. After another hour of tweaking the Steve Swayze primary and the Protostar 2.14" secondary we had the best estimation of collimation we could achieve in the dark despite a questionable positioning of the secondary. We would stop there and get down to some observing.
Given the scramble to get this scope functional, I had little time to think about an observing list. Although the folks at the starrynights e-group had committed significant effort in constructing a list of targets, I forgot to pursue that until too late in the evening, at which time those objects were mostly too low in the sky. What I concentrated on were a number of object that I had looked at before in the 6" f/6 so that I had something to compare to and objects that my friends from TAC-South were either discussing or imaging. Paul L. was working his way through his project to image all of the Messier objects, so it was fun to compare with what he was seeing on the computer screen, what I could see in "The Big Guy" and what I had seen previously in my 4.5" f/8 and 6" f/6 newts. Here is a semiformal report of that program (if you just want the punchline go to the last paragraph):
| Date | 1/21/01 3:30 13:00 UT (7:30 PM 1/20/01 5 AM 1/21/01 PST) |
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| Location | Little Blair Valley, Anza Borrego Desert State Park, CA |
| Temperature | falling to 22 deg F. |
| Limiting Magnitude | ~6.0-6/5 |
| Seeing | 5/10 7/10 over session |
| Scopes | 6" f/6 Dob, 12.5" f/5 Dob |
| Eyepieces | 30mm Celestron Ultima, 13 mm SWA Gary Russell Optical, 8 mm Televue Radian, 2.5X Televue Barlow |
| M42/43, emission nebula, Orion | The first test was that old standard. The Orion Nebula was gorgeous in the 30 mm at 45X in a 1.2 degree field. A contrasty three-dimensional image surrounding a trapezium. The dramatic undulations of the wisps of nebulosity that form the cup-shaped edge of M42 that holds M43 in its embrace. The bulge of nebulosity beside the trapezium was particularly apparent. I never tire of these objects and this view was particularly stunning. I had the distinct feeling that the image faded from subtle pink on the outer reaches to an equally subtle blue/green hue. Not enough to say that the color was real but the sensation of color was certainly there. Moving to the 8 mm Radian the contrast remained and the dimensionality was enhanced. Although the seeing was unstable 5 stars in the trapezium were apparent (6 were picked up later in the evening as both the sky and I settled down). Despite the lack of blackening on the uncoated portions of the secondary and still-needed fine tuning, this was going to be a wonderful scope. |
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| NGC2024; emission nebula; Orion | Paul L. was imaging the Flame Nebula and I thought I would give it a shot. Since it was adjacent to Altinak, the first star in Orionıs belt, I thought it would be easy to find and I was right. Paul had told me I would see it without a filter if I moved Altinak out of the field but I found it was obvious without doing that. Of course, doing so made the image even more distinct providing excellent views of this beautiful bifurcated flame of this emission nebula. In my haste I forgot to try my newly acquired OIII filter that is said to increase the extent of this image. |
| B33/IC434 reflection nebula; Orion | Paulıs CCD image included the Horsehead Nebula to the North. I asked him whether I should expect to see it in the 12.5" with my H-III filter. He said yes and went to the 30 mm eyepiece, took a look and imediately said "There it is. This is a nice scope". I took a look myself. Although I clearly saw the undulating edge of IC434 and the dark abscess of B33, it was very difficult to make it out as a horseıs head. I asked for guidance as to the orientation of the head and only then did I believe, via averted imagination, that I had seen the famed Horsehead. Not a great visual object, but exciting to be sure. |
| M36-38, open clusters, Auriga | Since my brother was still struggling with starhopping using the 6" f/6 and his 4.5" newt I thought it would be fun to take in M36-38. I showed him where to look and then took the big guy over to M37. I love this open cluster which in the 6" f/6 just begins to be fully resolved into component stars. That was certainly not the case in The Big Guy. Here the stars are clearly resolved with clear distinction in color variation of the pinpoint stars in the middle of the cluster. I have always found M36 and M38 to be somewhat less satisfying but it was fun to see them from the perspective of this more powerful light bucket. |
Now it was on to some galaxies. Opening up Penningtonıs wonderful "Year-round Messier Marathon" I picked out a number of galaxies and galaxy clusters. Most of them I had seen before and since this was a night for comparisons I thought them appropriate targets.
| M108, spiral galaxy, Ursa Major | This spiral in Ursa Major presented its mottled edge-on view with stunning clarity. This was one of the less distinct M objects in my smaller scope but here it was clear and distinct. Unfortunately, I forgot to look for its neighbor M97, the owl nebula. |
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| M109, spiral galaxy, Ursa Major | This view of a spiral from another perspective, in this case a top-view, was equally satisfying, a clearly denser core surrounded by the dimmer disk of the galaxyıs periphery. |
| M81/82, elliptical/irregular galaxies, Ursa Major | The first of the multiple galaxy groups viewed that night and the first galaxies I ever saw in a telescope. I saw these in my 4.5" DS114 EC in late 1999, just over a year ago, from my suburban front yard. There, with averted vision, I saw the faint apparitions of this irregular cigar shaped galaxy and its spiral neighbor. These were anything but apparitions in this scope, standing out against a starry background. |
| M65/M66/NGC3628, galaxies, Leo | This striking triple galaxy cluster in Leo was another first for me. I had never looked at these before, but again, because Paul had decided that these were good imaging targets, I decided to pursue them. What a reward! Less than half a degree apart, this pair of spiral galaxies is beautiful their own right. But throw into the mix the edge-on spiral, NGC3928, and you have a truly awesome sight. NGC3928 is dimmer but spans a significant portion of the 1.2 degree field on the 30 mm Ultima. All three are contained in that single field of view. |
Close by, just to the west of Chort, lie M95/ M96 and M105. Again, M95/96 fit in a single field. Both galaxies are smaller and more condensed that those previously discussed.
| M105/NGC 3384/NGC 3389, galaxies, Leo | M105 has two fainter companions which form a striking L shaped array with the NGCıs almost starlike at 45X. However, all three still fit in the same field of my 13 mm SWA at around 120X. NGC3389 is significantly fainter and forms a relatively featureless smudge just to the North. |
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After scanning the Pleiades for nebulosity which was plentiful, I went to sleep for a couple of hours in preparation for viewing of Omega Centauri which would rise slightly above our southern horizon about 3 AM. Awakening about 4:15 AM I heard Paul up and about. Exiting the van I found him at the eyepiece taking in this dramatic cluster.
| Omega Centauri, globular cluster, Centaurus | Peaking into Paulıs 10" LX200 I saw this globular cluster filling the field (not sure what eyepiece or magnification). I went to my scope and asked Paul where he was pointing. Since he had jumped to it using GoTo he wasnıt quite sure but thought it was a weakly visible object about 20 degrees above the horizon. Positioning that in the quickfinder and scanning the area I found a diffuse object but definitely not the one I saw in Paulıs eyepiece (see below). Referring to both Starry Night Pro running on my now completely frosted over Mac laptop, I determined that the two stars low on my horizon were zeta and gamma and that the bright object between them was, in fact, Omega Centauri. Positioning my scope on that object gave the "wow" I was expecting. This globular has an extremely dense core which feathers out to areas of blotchy but still unresolved regions in the 12.5" at 45X. Finally, there is some resolution of stars around the edge. This cluster is a huge. Despite its position only 10-15 degrees above a somewhat bright southern horizon, it was very impressive. Yet another reason I feel blessed to live so far south (that morning warm temperature was not one of them). |
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| Centaurus A, elliptical galaxy, Centaurus | The first object I found turned out to be the peculiar elliptical galaxy Centaurus A. I didnıt spend much time on it because it wasnıt my target but I regret that now. It was obvious to me that this galaxy was irregular and appeared to be fragmented. I realize now that that appearance resulted from the dramatic dust lane running across it. I now need to revisit this interesting object. I wrapped up viewing for the night with relatively unsatisfying views of Mars and a glance at the rising moon that was pretty with a bright star off the limb but unstable through the soup at a ridiculous 10 degrees above the horizon. The latter was really just to feel what it was like to position myself at the eyepiece of the almost horizontal Dob. |
All in all this was a very good night and a milestone in my observing history. Despite the shaky start, First Light turned out to be exciting and satisfying as promised. I have yet to do a star test or to rigorously test any aspect of the system. That said, the Swayze/Protostar optics had so far shown themselves excellent performers, despite the lack of optimization.
Our basic design had proven itself once again to give good stablity and movements and attracted a number of oohs and ahs from others which is always satisfying and I think made my brother proud of his work and oversight. Do we have more to do? Yes! The whole scope will be torn down and several more coats of marine varnish applied. Mirror edges blackened, baffling inserted, bushings reamed out, fan installed, etc. But these are fine adjustments to what promises to be a fine optical instrument that will give us satisfaction for a long time. And, no. Although it is the next step in the arithmetic progression, we have not started designing a 24"f/4. :^)