Summary (or TLDR):
Is it as crisp and bright as my 16" Dob? No.
Is it as easy to collimate as my 16" Dob? No.
Is it easier to move and transport than my 16" Dob? Oh yes.
Will it get used more often? Yes indeed - and that is the clincher.
I recently sold my 16" Telekit Dobsonian (details here,
http://www.iceinspace.com.au/forum/s...d.php?t=134192 ). It was (and still is) an exceptionally good scope and easy to set up. However it is over engineered, heavy and larger than it needs to be. It was next to impossible for me to transport to dark sites and I am a little peeved at the poor contrast available in my light polluted suburban back yard. So something marginally smaller was called for. Enter the Celestron CPC 1100.
First things first, lifting and shifting. Yep the OTA weighs in at nearly 30kgs but the cleverly placed handles made carrying it very easy for me. I would not recommend it for someone with a back problem though. I had a little trouble finding the locating pin on the tripod but this should get easier with practice. Tomorrow night I will be carrying the scope around to the other side of my house to view Jupiter. Something I could not do with my 16" Dob even with the wheelbarrow handles as the path is too narrow. The CPC fits in my car with room to spare, no ramps required - the 16 Dob barely fitted in my Outback station wagon.
Secondly, power. I was using a Kogan 20000mAh 12V Lithium battery pack that you may be able to see balanced on the azimuth clutch in the attached picture. From tonight's tests (with a lot of slewing) I think I will get a bit over 5 hours use from this tiny lightweight battery. At least until I add a SkyFi which will likely reduce that operating time a bit. I will probably just purchase a second battery for longer sessions. Two downsides to this battery: 1) the blue power level and voltage selection LEDs are blindingly bright and will need replacing with red LEDs and higher value current limiting resistors - a project for another day, black tape works for now. Downside 2), there isn't a large enough flat surface on the rotating azimuth section of the scope to attach it to. The AZ clutch does not rotate when locked and it took me a while to work out what the ripping Velcro sound was when slewing! I was going to turn the anti-cord-wrap feature of the CPC off if I could put the battery somewhere that rotates with the scope. Not to be it seems. Not really a big issue, it just means the scope may occasionally slew the long way round.
Thirdly, collimation. I purchased some Bob's Knobs and am glad I did. Poking a Phillips head screwdriver at the corrector plate in the dark is the stuff Murphy's Law was built on. The collimation was way off from installation of the knobs and it took me at least 15 minutes to get it right. I do miss my motorised primary mirror cell and holographic collimator. Got there in the end though and it will be interesting to see how well it holds collimation during transport.
Fourth point, goto alignment. Sky align is just stupidly simple. Colour me impressed. I'm used to having to know and select stars for the Argo Navis alignment. This "pick any three bright things" is an excellent example of Arthur C. Clark's third law (any sufficiently advanced technology is indistinguishable from magic.) No issues with GPS lock or centring objects all night. A+
Number Five, the Nextstar handpad. It took a bit of fiddling with the contrast and scroll speed settings to get a readable display on this chilly 7°C (3.7°C with wind chill) night. The slew/jog speed controls are very good but I find the goto lists a bit lacking and cumbersome. I don't know the NGC designations for a lot of my favourite DSOs (deep sky objects) and their names were not in the named objects list. This will be rectified with the addition of a SkyFi and tablet control.
Last but not least, optical performance. The scope is stored downstairs in a very cool room that is just about outside temperature - still I think part of the poor seeing I was experiencing was due air movement in the scope as the corrector plate and mirror tried to keep up with the plummeting temperature. To my naked eye the stars were not noticeably twinkling anything like what I was seeing through the scope. I just barely split Rigil Kent (4.1"). I have some Temp-est fans on order and hope this will help. Saturn was wobbling all over the place and (as an aside - the scope and tripod with the legs retracted is very stable, vibrations damp down in a second or so) little detail could be seen. I don't actually remember if I could even see the Cassini division.
Omega Centauri and 47 Tucanae were their usually disappointing selves due to the bright sky in my back yard. The dark dust lane in NGC5128 was barely visible with averted vision. All this was through my Tele Vue 35mm Panoptic, 17mm, 13mm and 9mm Nagler eps. I switched to my Denkmeier binoviewer with 21mm Denk eps for a look at the Tarantula Nebula. Bam! Oh my! Two eyes are better than one. The Eta Carinae nebula was next and did not disappoint either. I went back to my previous objects and all were enhanced except for Saturn. I have no difficulty merging the two eye images for DSOs but I just can't do bright planets. Possibly due to a slight downward missalignment of one of my eyes and the smaller pupil size when looking at brighter objects.
Overall, in my subjective and entirely un-empirical view, the optical performance was not as good as I was used to with my 16 Dob. I actually miss diffraction spikes! The larger secondary obstruction and smaller diameter of the CPC was noticeable in comparison giving a slightly softer image. Disappointingly so? No. This is a compromise I can live with if it means I can use my telescope more often and transport it to darker sites.
