This month I spent 5 nights on the mountain at El Sauce Observatory in Chile installing my CDK17-DeltaRho combination on the Planewave L-600 Mount.  This is the first light image with the CDk17 and I couldn't be happier with the data it is collecting.  I only hope my processing skills can do it justice.  

About The Install
We ran into a number of problems during the install starting with the fact that this scope combination won't naturally balance on the L-600 Mount.  The mount is designed to have a larger scope on the inside of the "L" which is both heavier and has a center gravity farther from the mount arm.  Add to that the DeltaRho on the other side of the mount arm and, with the L-600 fully shift on the RA axis and the full counterweight set on the toe, we were still 50 pounds out of balance!  In case you are wondering, yes, I did ask if it would balance before I bought the combination and was told it would.  

This issue was discovered a few days before my flight to Chile and, needless to say, I was worried the whole trip would be a waste.  But the guys at Obstech were resourceful and designed a counterweight shaft extension having it fabricated in a local town.  Unfortunately the counterweights available onsite were the wrong inner diameter so a sleeve was 3-D printed onsite to fill the gap.  Balance issue resolved but I was worried about the longer, relatively thin counterbalance shaft vibrating and causing poor performance.  

Cabling, final balancing and setting things up on the network required two full days.  I chose two different Power/USB hubs, a Power*Star from https://wa-chur-ed.com/powerstar/  for the CDK17 and the https://pegasusastro.com/products/ultimate-powerbox-v2/ for the DeltaRho.  Two different solutions gives me a potential back up solution if one is not performing or fails but also more clarity on which scope I'm controlling!.  I also used two different cameras.  A QHY600M on DeltaRho and an ATIK ApX60 for the CDK17.  I've used many QHY600s but wanted to try out the ATIK becuase it has built-in push-pull screws for tilt correction.  I did use the same FLI Centerline filter wheel on both scopes.  This indeed turned out to be a problem because the identifier the FLI driver puts out seems to change each time you power up.  So whichever was on first was wheel 0 and the next incremented to wheel 1.  It was impossible to tell which was which remotely.  The solution to this was simple since I only plan to use one scope at a time - power down the one you aren't using!

One the third night I started with focus.  Sure enough neither scope would reach focus with the adapter/space combinations that had been planned.  I still don't know how these calculation errors occurred.  One scope was too far in and one too far out.  After a night with little sleep, day three was spent trying to figure out a solution with parts that could be scavenged onsite.  Thankfully, we were able to find sufficient PW spacers and adapters to make it work.  WHEW!

One the fourth night, after polar alignment, autotune, and a quick model build, I focused and looked at the stars on the DeltaRho.  Not good.  Definite tilt.  The next two nights were spent trying to get the tilt corrected on the DeltaRho using the shims on the PW tip-tilt without success.  I could go on quite a while on this topic but suffice to say I prefer push-pull screws...

I had barely looked at the CDK17 at this point.  Only a quick image that showed it too had tilt issues.  But the skies clouded and my time was up.  Once I was back home, one of the Obtech technicians and I labored through using the ATIK tilt corrector and got it right.  Meanwhile, Planewave refined the tuning on the L-600 and got it to a 0.05-0.08" servo error range across most of the sky.  The counterweight shaft extension was not and issue!

First Light and Performance
Once the tilt was corrected I fired things up and shot a first image of NGC 253.  The first sub came back at 1.4" FWHM and the detail was better than I had hoped.  Over the next few days things got better from there.  The luminance master in this image has a FWHM of 1.35".  I used a cutoff of 1.59" and had subs down to 1.15".  As I'm typing this the best sub I've gotten was last night at 0.98".  The rig and software stack have been very consistent as well.  Most of the last few nights my yield has been been near 100% of the subs with overhead of about 15%.   This is all way beyond my expectations and I really excited about what this scope will give me in the future.

Processing This Dataset
My color subs had good sharp data as well so I did separate color masters of just the sharpest subs and then created a SuperLuminance of only the best data.  I ran the SuperLuminance through deconvolution in CCDstack. 

After creating the LRGB master in PI, I used StarXterminator to separate the stars from the galaxy.  The stars in the galaxy were well defined enough that StarX actually removed stars from the galaxy itself - 11 million light years away!.  Unfortunately it also removed quite a few of the nebulae and background galaxies.  To fix that, in Photoshop, I put the starless layer over the original layer, created a mask on the starless version, put the stars only version above it and painted black on the mask where I saw nebulae in the stars only version.  That returned the missing nebulae to the starless layer.  Then I copied the mask to the stars only version were it removed the nebulae that shouldn't have been there.  Sorry if that's confusing but if you do it in order in PS it works!

With the stars removed I could work on contrast and color without being harsh on the stars.  Color required very little work as I used PI's new Spectrophotometric Color Calibration for the first time.  Unlike the old PCC, the colors came out exactly like I was expecting on the first go.  And they should be the most accurate colors.  most of the color work that remained was just adding color contrast.  

Next Steps
I've taken a break from trying to get the tilt fixed on the DeltaRho.  We are going to get an analysis from Skywave to help guide us on the corrections.  I suspect we may revert to the old "aluminum foil on the dovetail" method for making adjustments rather than use the PW tip-tilt.  Will try again this full Moon.