Celestron C-11 vs Meade 10" LX200R

The Setup
When my new 10" LX200R OTA arrived I spent the first couple of clear nights messing around with astrophotography issues. On the third, mostly clear night I undertook a thorough comparison of this new scope with my trusty old C-11. Here are some photo's of the two scope installed side by side on a 16" Casady Tandem Bar with two 8" Casady Saddles. An embarrassment of riches to be sure!
If anyone is contemplating the same course let me recommend a longer tandem bar. The 16" just barely worked. The screw head on the front ring of the Meade are touching the front ring of the C-11 and the Meade dust cap is touching the C-11 so tightly that I had to remove the OTA to take the cap on and off! Never fear this is not a permanent setup, just a one or two night testing arrangement. I had to order an extra 25# weight in order to balance both of these OTA's together on the CGE mount. While I certainly can't recommend this for photographic stability for casual visual use it works alright.
Focus and Collimation
I finished the two-star alignment of my mount on Regulus and it was high enough up that I decided to use it for my initial testing. The first difference that I noticed between the two scopes was that in slewing from my first alignment star to my second alignment star the focus of the C-11 showed no discernible shift but the LX200R did need to be refocused. The focus lock was not engaged on the LX200R but then the C-11 has no focus lock. My second observation was that when viewing the region around Regulus in my 56mm Meade Plossl eyepiece in both scope the C-11 showed a slightly crisper view and slightly better contrast than the LX200R.
I had collimated the LX200R on the previous night but I decided, based on these initial observations, to recollimate. I spent the next 30-45 minutes fine tuning the collimation of the LX200R. While I did make some improvement I was disappointed to find that I could never get my concentrically defocused star perfectly center both inside and outside focus. When I got it perfectly centered on one side of focus I would roll to the other side and it would not be centered. I finally settled on splitting the difference between the two sides of focus.
Star Test
I proceeded to star testing the scope using Thomas Back's Primer as my guide. I should note that the seeing was not spectacular. I would estimate it to be about Pickering 6. Normally one would not wish to undertake a serious star test under such conditions but since my primary concern was a side-by-side comparison I decided to forego a prolonged wait for ideal conditions. I did not use a diagonal in the testing.
Starting on the LX200R I centered Regulus at slightly better than 200X and defocused 5 diffraction rings. This looked promising, the inner most and outer most rings were of similar thickness and the three intermediate rings were thin, evenly spaced and quite distinct. Shifting to 5 rings on the other side of focus was less impressive. The outer ring was still thick and symmetrical but the inner ring was mushy and blurred into the second and third rings. Next I moved to the C-11 and repeated the test. The inner and outer rings were thick and well defined. The three intermediate rings were fairly distinct and evenly spaced but slightly broken. The whole diffraction pattern had radial "jaggies" that I did not observe in the LX200R. The pattern was the same on both sides of focus.
Next I defocused by just a couple of rings. The LX200R showed a pretty symmetrical ring with just a little bit of squashing on one side. On the other side of focus, however, the ring was fuzzy and indistinct. The C-11 made a much better showing on this test. It displayed a sharp symmetrical ring on both sides of focus.
I defocused the LX200R by 10 rings or so and on both sides of focus it showed a fairly nice and symmetrical ring pattern with no real obviously thinner or brighter rings. The C-11 showed similar results. At this level of defocusing the radial "jaggies" were less noticeable.
Next I attempted an in-focus test but with the seeing conditions I could not get a steady enough airy disk to judge the 7% and 3% energy distribution of the first and second rings. I evaluated the "snap" of the focus and found that there was none. Critical focus was mushy in both OTA's.
First let me say that you can't got wrong observing Jupiter near opposition with either one of these instruments. The differences were subtle. Here are a few observations.
  • In 32mm eyepiece C-11 showed darker sky background around the planet.
  • In 17mm eyepiece both scopes showed amazing detail in the equatorial bands including faint swirls in moments of excellent seeing. Maybe a slight edge to the C-11.
  • In 17mm eyepiece the moons appears more sharp and "pin-point" like in the LX200R.
Splitting Doubles
I've never been into splitting doubles so forgive me if I've butchered your pastime. Again, for comparison purposes I figured it was worthwhile. I slewed the scope to STF1647 in Virgo. I naively thought that a well known double of 1.3" separation should be no problem. As it was I had to go to about 375X with seeing conditions that could scarcely handle it but I did manage to split the pair in both telescopes. The only useful comment I can make is that I thought the LX200R showed a little better defined separation than the C-11.
Field Correction
Clouds were starting to roll in around the south-east and south-west horizons so I slewed over to Ursa Major for my last test. I wanted to spend some time inspecting the edges of the field in my 56mm Plossl in both telescopes. Here I think I could finally see what all the "R" fuss is about. In the LX200R the stars were pin-point from edge to edge. In the C-11 I could see flaring around stars close to the edges.
I bought the LX200R primarily for astrophotography. If I had bought the scope as an upgrade for visual use I would have been disappointed with these results. My biggest concern from these tests is the collimation problem and asymmetrical focus properties. Further work may be required to resolve these issues.
I hope that you have found this information helpful. As for me, I intend to continue debugging photographic issues with my LX200R rig.
See my first light image taken with the LX200R.

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