Success . . . and maturity!
It's been two and a half months since the 15-inch Obsession arrived, but last night it was all worth it. I had four hours of excellent observing despite 4.5 magnitude skies that were not nearly as steady as predicted.
Why so long? The weather has been terrible and I ran into a list of small problems, one of which brought me almost to the send-it-back-point. But with help from Dave (Obsession) , Gary (of ArgoNavis) and many on the Yahooo Obsession Users discussion list, I got it all together and last night it all worked together as advertised. My enthusiasm for the Obsesion 15 hasn't dimmed - but it has matured significantly ;-)
( Click photos for larger version.)
My only remaiing concern is whether I've got the collimation to where it should be. I feel I'm following the laser collimating procedure as described and getting the right results, but I was still surprised last night to find that I could barely split the double double in Lyra at 205X. (This is after using an extra, external fan to blow on the mirror for more than four hours and observing between midnight and 4 am when my Clearsky Clock forecast was for cloudless skies (true) with poor transparency (true), but good seeing (false - i think). I was able to use 264X on Mars, though it was just as good at 205X, so the seeing didn't seem that poor, though I certainly could go no higher. I also checked this near the start and end of my observing session and recollimated for the second observation. So I'd like to hear from other 15-inch users in this respect - that is, do others find there are many nights when it is hard to split the double-double?
My greatest observing satisfaction of the night came when using an OIII filter on the Veil. Simply magnificient. I could barely detect it without the filter, but with the filter I could have spent hours exploring all the detail and I can't wait for a truly transparent night when my skies get down to about 5.5.
What problems have been solved? Primarily the nasty encoder problem. Having replaced the alt encoder I had difficulty getting it correctly positioned. However, the post #21455 on the Obsession Users Group from Jean-Paul Richard describing an approach with a laser worked beautifully for me. I also moved the whole assembly to the other side (opposite the eyepiece) making room for one of Charlie Stark's "Stalks." See: http://Marklessastronomics.com/#dscstalk
Charlie, btw, has been extremely helpful with a number of questions related and unrelated to the stalk, as have other individuals in the users group.
I find the stalk absolutely essential with the ArgoNavis and ServoCat installation. I had tried to use the scope without them and the wires going everywhere were driving me crazy. The stalk solved the major part of my wiring problems and provided really convenient placement for the two handcontrollers. I found that with this arrangement I could easily use the ServoCat hand controller "blind" - that is, while looking through the eyepiece I could reach for it and tell by feel which button to push. This worked better for me than using "Velcro" to attach it nearer the eyepiece and I really like the AN controller sitting there in plain sight. (I have the new version with a plastic holder - also new - that I screwed to the little Plexiglas stand using a couple 6-32 metal screws, washers, and nuts. )
The second solution to my wiring problem I borrowed from Bob Smith - see his photos in Photo File section of Obsession Users list at Yahoo. I got a piece of maple from the local Lowes and made a very simple shelf that holds my Orion Dynamo 7-amp-hour battery - again, on the side opposite the eyepiece and using the mounting holes already there for the wheelbarrow wheels. The battery had plenty of juice left after providing more than four hours of power for the ServoCat and the AstroSystems Dew Guard for the secondary mirror. I prefer this last to the simple heat rope - uses less juice and tells you when it's running - see: http://astrosystems.biz/dewgrd.htm) I'm still powering the AN on batteries, but will probably add it to the main battery. It would be a rare night where I would need more than four hours of power, but I suspect this would provide it if needed it and I doubt the AN adds very much.)
The first time I did a "goto" from one side of the sky to the other I must admit I shone a red flashlight around in a half panic looking for wiring problems. There were none - of course, since all wires now travel neatly with the scope as it moves. Without the shelf wires can easily get tangled and bring the scope to an unwelcome stop.
Performance? The optical performance should go without saying - and besids, I really don't consider myself much of a judge on that score. Certainly seems great to me, except for that nagging business of the double-double.
GoTo performance was excellent most of the time and satisfactory the few times it wasn't excellent. That is, I was going all over the sky - M27, M31, M57, M11, M33, Gamma Andromeda, the Veil, Mars, etc. - and with nearly every move the object I sought was in the 34' FOV at 115X. In fact, a couple times when I had forgotten to change from high power it was in a FOV less than half that size. A couple of times, inexplicably, it missed by a little. In these instances, however, I very quickly found the object with the elegant spiral search technique provided by the ServoCat. Tracking was fine for visual observing up to 264X, the highest I used, though I didn't stay on any single object more than 30 minutes and most much less. ( I was in kid-in-a-candy-store observing mode ;-)
Computer interface? I much prefer the AN to the Meade AutoStar system on my LX90. I've gotten used to the Meade quirks now, but there are too many quirks for my sense of what constitutes good computer interface design. The ArgoNavis is fast and simple and solid. The ServoCat teams up with it remarkably well and I found the ServoCat was easy to use both for finetuning and for more lengthy sidetrips, such as tracking down M32 and M110, the two companions of M31.
Bottom line. If I were talking to potential buyers I would recommend the Obsession and the ArgoNavis and the Servocat. But I would also suggest to them that there is a significant list of extras, starting with the stalk. Some necessary extras are sold by Obsession, some not, but you really need to look closely at this situation if you're going to get full satisfaction out of the scope. And, I would add that this may turn out to be more of a do-it-yourself project than you think.
That said, I do feel I have a good understanding of the scope and its possibilities and I am looking forward to the drier, more transparent skies of Autumn with more enthusiasm than I ever have had in 40-plus years of on-and-off amateur astronomy.
