This is the story of my new 24” telescope.  Grab some coffee—it’s a long one.

As many of you know, I’m driven to produce images that reveal as much detail in an object as possible and the desire for a bigger telescope has bounced around in my mind for quite some time.  The idea really took root when the sales guys at 4D Technology told me about their visits to Astro Systeme Austria (ASA).  They reported that they did an interferometer install at the company in Austria and met a very professional group of engineers working in an impressive facility to produce both amateur and professional level telescopes.  Over time, ASA has purchased 3 PhaseCam real-time interferometer systems (and now they may have a 4th) so they have the means to very accurately test their optics.  Furthermore, I’ve since learned that they use holographic optical nulls to very accurately (and repeatably) make the aspheric surfaces for their RC telescopes.  After seeing the images that Wolfgang Promper produced with his ASA600, I began to think more seriously about buying one of their systems.  Wolfgang works for ASA and he uses his own ASA600 to image remotely in Namibia so he is much more than simply a “sales guy”.  He is an expert in these telescope systems.

Along the way, I mentioned the idea to my former professor, long-time business partner, and friend Jim Wyant. At the time, he was growing more physically debilitated from the effects of ALS and his time was quickly running out.  So, when he said, "Don’t worry about the cost, just get the bigger telescope!", his advice held special meaning.  Life is indeed short and he was right—as always.

The Telescope

When I first inquired about the specifics of the ASA600, ASA actually had the two mirrors for a new 24” sitting on the shelf and they were kind enough to send raw PhaseCam test data of the primary so that I could look at it using my own copy of Foresight (the 4D data analysis program).  I was immediately impressed.  I’ve included the data I received from ASA.  The PhaseCam is a Twyman-Green type interferometer that measures optical phase in a single exposure of about 25 micro-seconds. That makes it possible to “freeze” the effects of normal mechanical vibration and air turbulence in the air path.  Using fans to stir the air randomizes the turbulence to shorten the short correlation time so that the random turbulence can be time averaged to very low values over a few hundred frames.  This makes the optical test results very precise and with care, it is possible to measure the surface down to a precision of about 1-3 milli-waves.  This data can be used to assess both the optical figure as well as micro-waviness, which relates to figure “smoothness”.  ASA specs micro-waviness (they call it micro-roughness) at 1 nm rms on the optical surface and they can actually measure it!  PhaseCams were used to test all of the segments of the JWST mirrors (both in production at Tinsley and for cryo-testing) as well as to measure the thermal and mechanical stability of the carbon fiber back-plane structure.  A special multi-wavelength version was also used to test the phasing algorithms for the assembled telescope.  So, this is state of the art optical testing capability.

Computer generated holographic optical null elements basically produce an image of the lens needed to produce a spherical return wavefront from the aspheric surface under test.  The challenge with this technique is to get the hologram perfectly aligned to the axis of the optic being tested.  Arizona Optical Metrology (AOM) has solved this problem is a very clever way using separate alignment holograms around the edges of the null hologram to precisely align the hologram to within fractions of a wavelength from where it is supposed to be for any particular test.  This method makes it easy to test very steep aspheric surfaces that could not otherwise be tested without very expensive optical nulls.  So, ASA is using state of the art methods to measure the quality of the components that go into their telescopes.  And judging from the results, they have the fabrication capability to make world class components.

The ASA600 is a F/7 RC that has an aperture of 600 mm with an obscuration ratio of 40%.  The primary mirror has a focal ratio of F/2.5, which makes for a relatively short OTA and give an optical magnification factor of 2.8 for the secondary.  The OTA design incorporates a rigid carbon fiber mirror box with an upper carbon fiber truss to support the secondary.  Physically, the ASA OTA looks considerably smaller than the CDK systems made by Planewave.  Planewave uses a slightly different OTA design with the primary mirror cell supported by a lower truss structure and a slightly slower primary mirror so the OTA is both a bit longer and bigger around.  The CDK24 is a F/6.5 system so it’s a bit faster than the ASA600 but that means that it requires a slightly larger obscuration ratio of 47%.  At 231 lbs, the weight of the ASA600 is 9 lbs lighter than the PW CDK24 OTA so, it is within the 300 lb load limit of a L600 mount.  Since I had a lot of experience with the L500 on my CDK20 and I liked it, I ultimately decided to go with a known quantity and ordered a L600 to go with this scope.  

On paper, the ASA600 appears to be more expensive than the CDK24, but they are bundled differently.  The base price of the ASA scope includes a secondary focusing system that uses encoders to report precise position.  The ASA scope also includes built-in motorized mirror covers.  Both of these things are separate line items for the Planewave scopes.  The one item missing from the ASA standard price is a field flattener, which is inherent in the CDK design.  With a focal length of 4200 mm, a field flattener is not absolutely required unless the sensor is pretty large.  I wanted the system to handle any size sensor and this scope can cover up to a 100 mm field radius.  I also wanted the field flattener to provide a dust barrier to the filters so I ordered one.   In the end, depending on what you need and the exchange rate, the ASA scope may be very comparably priced a similarly equipped Planewave scope.  It was also an unexpected bonus to discover that the shipping rate from Austria to Chile was considerably less than from Michigan to Chile.

One final fairly significant difference between these two scopes is the back working distance (also called the back focal distance) which is the distance from the rearmost mounting surface to the focal plane.  The BWD relates to how much physical space you have for focusers and other gear that you might want to put on the back of the scope.  With the field flattener, ASA only provides 210.38 mm, which is considerably less than the total distance provided by the CDK24 from the telescope backplane to the focal plane (which PW doesn’t specify in their online literature.)  I believe this is one reason that the ASA is offered with the integrated secondary focuser as standard equipment.  With my ONAG guider, there just isn’t much room available for an external focuser or rotator so the orientation of the camera is fixed.  This is how I ran my C14 for years and it works well.  With a fixed camera, framing is sometimes more difficult but flat data can last for quite a long time!

So, How Good is the Wavefront?

One thing that I wanted before taking delivery of the telescope was a wavefront measurement of the fully assembled telescope in double pass. So, I planned to travel to Austria to help set up the test and to inspect the telescope.  The folks at ASA knew that I was one of the founders of 4D Technology and one of the inventors of the PhaseCam technology and they were incredibly nice to try to accommodate my request.  In preparation, they set up the test in their shop using a large precision return flat and sent me some data, which was really what I wanted to see in the first place!  I’ve included an image of the test set up.  I had them tweak a couple of things and after looking at on-axis data from the two-mirror system as well as the system including the reducer, I canceled my plan to visit the factory.  (That turned out well because half of Europe got shut down by a giant snow storm in early December when I had planned to go!)  I discovered some problems with the telescope after delivery but I’m not sure that I would have caught them during a pre-delivery inspection anyway, but more on that to come.  Overall, the optical quality looked superb!  The spec for the telescope is to achieve a Stehl of 94% or better and the double pass data shows a measured Strehl of 95.4%, which included a bit of residual astigmatism that may be due to the field position.  We don’t remove astigmatic errors because that also may be due to manufacturing errors as well.  Clearly the wavefront meets the ASA spec.  With the field flattener installed, the on-axis Strehl drops to be just slightly below 90%, but it is still very acceptable.

Micro-waviness can be determined by removing the overall shape of the wavefront with high order Zernike polynomials.  In order to remove the effects of some minor zones, I removed 120 terms and found the micro-waviness to be 9.4 milli-waves rms or about 6 nm.  Keep in mind that this number includes the contributions of micro-waviness from both surfaces so assuming an equal contribution from each surface, that’s about 4 nm rms on the surfaces, which doesn’t meet the 1 nm specification; but, it’s not terrible either.  In this case, the micro-waviness appears to originate primarily from the figuring process.  Micro-roughness as specified by ASA could also be associated with the surface finish of the surface but the PhaseCam is not a good way to measure that parameter.

The Installation

It took about six months before the scope shipped from ASA to Chile and I had to wait a bit for the new observatory building to be built before the scope could be installed in early March.  The trip to Obstech in Chile is a long one but it’s becoming familiar to me.  The telescope is going in the newest building (#12) next to an array of ten, 500 mm Delta-Rho telescopes operated by a group of Korean astronomers.  The Obstech techs had my new mount already unpacked, on the pier and set up when I arrived.  The OTA arrived in one of the nicest wooden shipping crates that I’ve ever seen!  That thing was built like a piece of furniture and it didn’t require any tools to open.  The scope is mounted vertically and it’s easy to use a crane to lift it out of the box. The installation, which included getting the scope on the mount, the camera package mounted, the wires run, and the scope balanced, took roughly 4.5 days before it was ready for first light.  I used the control system and guider/camera package from my 20” for this new scope.  So, I just had to wire everything through the mount, add a 24VDC supply for the OTA, and get everything balanced.  The OTA was seriously out of balance about its axis, which required making some improvised counter weights out of threaded rod and large steel nuts.  ASA sells a nicely machined version of what I made, but not realizing that I’d need it, I didn’t order them.  Maybe I’ll order some and send them to be installed.  My improvised weights almost perfectly balance the mount—but I had to leave it just a little off because I ran out of nuts and patience to keep fooling with it.  Installing more weight might mean having to shift the scope on the saddle and that is not easy so I don’t want to create unnecessary problems.

While balancing, I moved the scope around by hand on the mount and I heard a faint “click”.  I could move the scope back and forth to generate the same clicking sound so I searched for the source.  I put my hand on one of the lower truss tube ball locks and as I moved the scope, I could feel the truss tube shift down when it clicked.  Oh, oh…that’s definitely not good!  I felt the other tubes and found others that were moving as well.  I discovered that the tubes could be easily rotated and that virtually all of them were loose.  Looking closely at the ball clamps, I could see that ALL of them were pulled surface-to-surface tight.  That means that NONE of them were really clamping the balls on the end of the truss support tubes.  This is a significant manufacturing defect and I’m stunned that no one at ASA caught this.

I paced the floor about how to fix this problem and finally settled on using aluminum tape over the balls to get the clamps to tighten.  The tape is only ~0.002” thick (like aluminum foil) so it took multiple layers on many of the balls before I could get them to clamp tight.  The problem is that the tape is not very robust and the tape gets completely torn up if the rods are rotated.  When I left them, they were pretty snug but I need to figure out a way in the long term to fix this the right way with new clamps and/or new rods.  My final sky model showed pointing errors of 8.4” rms after the fix, so the truss is rigid enough—for now.

The basic initial optical alignment is pretty straight forward. Simply use a laser to boresight the main optical support tube on the back to the center of the secondary mirror and then use a Takahashi alignment telescope to adjust the secondary tilt to the axis of the optical support tube.

First Light

When we first pointed the scope at a star, we could see a bit of coma so we tweaked the tilt on the primary.  We got lucky and it came out pretty close.  Next, we defocused the star image enough to use SkyWave to precisely align the system.  We immediately measured a lot of coma…and a very strangely deformed defocused star image.  We moved focus from inside to outside and something was definitely very wrong.  I had carefully gone through the manual and there was nothing there about what might be going on.  Vincent (one of the two astronomers who own Obstech) thought that there might be internal centering screws inside the mirror’s central hole that could be too tight.  We both agreed that the mirror appeared to be mechanically distorted.

I contacted Wolfgang at ASA and he sent me pages from “the manual” that showed the problem.  The primary has a retaining ring around the perimeter at the front to prevent the mirror from falling out should the telescope ever point down.  That ring was touching the mirror and distorting it!  So, I followed the procedure in the manual to move the ring forward a bit.  The odd thing is that the version of the manual that is most useful has been removed from the ASA site so I had to get this manual through Wolfgang.  I just don’t understand how that kind of thing happens.  The most recent user manual on the ASA site is lacking almost all of the useful technical information contained in the earlier version that Wolfgang supplied!

After we moved the ring, the defocused stars looked MUCH better!  So, we went back to SKW to adjust the primary.  We carefully defocused, zero’d out the coma term and refocused.  Now the star field was loaded with maybe 2 waves of coma!  I know that SKW works (heck, I even wrote a paper with Gaston about it) but at that moment I was having my doubts.  How could this be???  Vincent told me that SKW always works and that they have used it countless times to precisely align other scopes.  We just could not understand this.  We looked at the star field and guessed where the alignment gave the least coma so that I could take some images with pretty round stars.  And, that’s how I solved the mystery. 

When I imaged, I turned on autofocus.  Thinking back on my trip to Chile, I sat on the plane thinking about it and I concluded that the focuser was the biggest unknown.  If it didn’t work well, I was going to be seriously screwed.  With autofocus running, I spotted something bad right away.  It held the star image steady in the RA direction but the image was moving about +/- 20 microns purely in the DEC axis.  I should mention that I aligned the camera on the scope so that it is roughly aligned with the long direction of the sensor aligned with RA.  That made it easy to see that the image stability with autofocus running in DEC was terrible!  With autofocus disabled, the guiding data was tight and very uniform in each axis.

Back to Wolfgang and he had the engineering department send me some 3D CAD cut away drawings of the focusing mechanism.  They suggested that one of the bearings might be too tight and suggested that I readjust the bearing set-screws.  I pulled it apart and sure enough, I found the problem.  The bearings weren’t too tight; they were too loose!  That caused the focuser to sag under the weight of the secondary as it moved and that’s why SKW couldn’t give good data.  The secondary was changing tilt when the focus changed!  I’ve adjusted a lot of precision bearing so I carefully adjusted these and it fixed two things:  sagging as the focuser moved and image shift during focus.  After my adjustments, the image shift isn’t quite zero but I should be able to make it work.  I spotted a number of weaknesses in the focuser mechanical design and I hope to be able to talk to the engineers about how they can improve the performance—and make the focuser easier to build.  I really need a night of excellent seeing to push the limits of this focuser before I can declare it 100% acceptable.  With this fixed, SKW now works really well and I have the alignment adjusted to show coma below 0.01 - 0.02 waves, which is fine.  SKG shows tight guiding with errors in both axis to be around 0.15” rms, which of course varies a bit with the seeing.  Autofocus works better on this scope than I have ever experienced!  When I first start, the system snaps into focus within only 2-4 guiding cycles and it holds focus within the CFZ all night long. I triple checked the focus against the 24” B-mask that I made for this scope and it is spot-on to within about +/- 0.125 waves of defocus.

When I checked the field performance, I could see two things.  First, the amount of astigmatism in one of the corners was not perfectly zero.  The other three corners showed perfectly round stars; however, it was obvious that there was image tilt relative to the sensor.  I don’t run NINA so I couldn’t use the nice routine in there for zeroing tilt.  I couldn’t find a dense enough star field for SKW and I had my doubts about using it.  I’m sure it works but I wanted something more concrete.  As I paced the floor, my eyes fell upon the B-mask and I realized that I had the perfect solution.  I pointed the telescope at M44 (an open cluster that happened to be near the Zenith and took an exposure through the mask and bingo!  It was trivial to see the tilt across the field.  It gave me both magnitude as well as direction—I just had to figure out which corner was which between the image and the actual sensor.  I installed the new/unused c1x61000 Pro Moravian camera that I brought down last April and when I pulled the camera to check the tilt plate, there were no set-screws!  My personal experience with Moravian has not been good with regard to this stuff.  So, I was faced with having to shim the camera.  I decided to use vinyl label tape, which should stand up to the weather, was easy to handle, and had a thickness of about 100 microns.  A little trial and error showed which corner I needed to shim.  Within an hour, I had it close enough.  I probably could have added just one more tape layer to get it perfect, but once I had the defocus term to less than about 0.25 waves across the field, that’s within the diffraction limit and good enough.  I've included an image showing the B-Mask image after alignment.  This method is unambiguous, inherently accurate, and very easy so it’s something to consider in lieu of using software measurements (and, please…I don’t have anything against software methods!).  The only downside to this method was that with all the camera removals, a big piece of debris ended up on the sensor creating a big dust mote but that’s correctable by flats.  I'll have to clean it out on my next visit.

I ultimately decided that the small amount of eccentricity that I could see in that one corner wasn’t worth the risk of messing with--simply because the chances of completely screwing up the entire alignment was far higher than the chances of fixing it perfectly.  I just didn’t have enough time on the mountain to fix it if I really messed it up.  It’s pretty minor and it’s easy fixed in post processing by BXT if needed.  If I have enough time on my next visit, I may mess with it.  I’ll certainly have to fix it if I put a bigger sensor on the scope in the future.

The Software

Because I run ONAG, I use SkyGuard for guiding and auto-focusing.  That limits my choices for the main control software.  I’ve been using SGP for years because it plays well with SKG so I’m sticking with it.  When I updated SGP, it lost the ability to plate solve and center on the target.   I had to reload PW2 and all of the catalogs to fix the plate solving problem.  Then I had to get with the guys at SGP to fix the centering function.  They eventually admitted a problem on their end but gave me a way to work around the problem.  Still, I give Ken at SGP an A+ for support.  He jumped right on it and I had a solution within a day or two.

As for SKG, I’ve never seen autofocus work as well as it does on this scope.  It snaps the system into focus within just 2-4 guide cycles and holds it there in real-time all night.  The guide performance is equally impressive.  I’m seeing typical guide errors of around 0.15” rms in each axis!  Overall guiding and focusing performance is superb.

The Dedication

Jim Wyant who pushed me over the hump to get this telescope died from ALS late last December.  He was a giant in the world of optics and I joined multiple university presidents and optical society luminaries to speak at his celebration of life.  When he passed away, he had won the highest award in optics --the Ives medal and he had three honorary Ph.D.s along with the one that he earned in grad school.  He was also a philanthropist and supported both the college and the students—and in turn, the University named the college, the “James Wyant College of Optical Sciences" after him.  And even though I knew it was coming, it was a very sad day for me personally when he died.  So, I had a little plaque made to dedicate this telescope to his memory.  He wlll always be remembered as “Jim” by everyone who knew him and now that’s what I’ll call this telescope.  I found some quiet moments to be alone with the scope and my memories of Jim while I mounted the plaque at the base of the mount.  He would be amused to know that I might say something like, “Damn it Jim!  Now what?” whenever I run into some new problem!

First image:  A Personal Best

As I worked to finish the commissioning, I began taking test images and almost right out of the box, I got lucky and snagged a lum-sub that broke the 1” barrier.  That’s a personal best for me.  I’ve posted it so that you can see it for yourself.  FWHMEccentrrictiy measures it at 0.96” FWHM.  I’ve gathered few more that are just slightly above 1” so I have high hopes that this scope can take full advantage of the seeing whenever it goes below 1”.  So, stay tuned.  This is just the beginning of the story!

John


Post Script

After my visit to the observatory, I met my wife in Calama to travel to San Pedro de Atacama for a week.   I ran the scope each night and half way into our vacation, I could see that something was seriously wrong.  In spite of arcsecond level seeing, the scope was producing nothing but blurry images.  When I mentioned it to my wife over breakfast, she looked at me and said, “There is still time before our flight back home.  I think that you should go fix it before we leave.”  We were in a nice resort and we had daily tours set up but she was totally happy to finish the trip on her own.  I’m sure that she was thinking about how miserable I’d be if I went home with the scope completely screwed up.  So, I agreed and made arrangements to get back to the observatory the next day.

On my first night back at the observatory, I first checked the focusing system and although it could be adjusted a little, it was clear that that wasn’t the source of the problem.  Then I checked the secondary centering screws and they were perfect.  Next, I defocused on a star and did an analysis with Sky Wave (SKW) and it showed a LOT of both coma and astigmatism!  How could that be?  I then took a 60 second exposure and zoomed in to closely examine the fainter star images and sure enough, they were indeed comatic.  So, I set about adjusting out the coma and I dialed it down to about 0.03 waves, but the astigmatism remained very high—like around 0.25-0.30 waves rms.  That’s around 1 wave of 3rd order coma, which is huge!  If you focus a system with that much coma to the position that’s called the “zone of least confusion”, you can produce nice round (ish) star images, but the FWHM will be pretty large—and I think that was my problem.  I fooled with the system until about 4 am before finally running out of gas. 

The Cause of the Problem

The next morning (actually around noon), I started thinking about what could cause all that astigmatism and the only way that I could get on-axis astigmatism is if something was being mechanically distorted.  So, I went back down to the scope and pulled the back cover to check the primary mirror retaining ring.  I tried following the method outlined in the instruction manual but it relies on “feeling” the ring contact through the screws.  What it doesn’t consider is that half of the screws feel tight and “gummy” throughout their range of motion.  The “feel the screws” method described in the manual is useless.

I then looked into the front of the scope to carefully study how the ring worked and I could see 4 evenly spaced, white pads (probably Nylon) around the bottom side of the ring between the metal and the mirror surface under the ring.  So, I took a thin card and used it as a feeler gauge to see if there was a gap at each pad and sure enough, one of them was touching.  So, I adjusted the position of the ring to produce a gap between the offending pad and the mirror surface.  That way, I knew for sure that nothing was in contact with the surface of the mirror. 

One thing that I should mention is that without drawings of how the telescope is built, it’s a process of experimentation to see how it is designed.  What I learned here was that the primary mirror retaining ring is not mounted to the mirror cell; it is mounted to the backplane structure that holds the mirror cell.  That means that when you adjust the tilt of the primary to remove coma, you are changing the mechanical spacing to the ring—and if you were to introduce enough tilt, the mirror can contact the ring.  That’s why they put so many screws around the perimeter so that once the mirror is adjusted, you can set the angle of the ring to match the angle of the mirror surface.  It’s not a terrible design but unfortunately, they don’t tell the user any of that in any of the manuals.  They also don’t give a very workable procedure to get the ring properly positioned.  I think that they should supply go/no-go plastic feeler gauges (readily available on Amazon) to set the position of the ring—AFTER the scope has been aligned (with the ring initially pulled way above the mirror surface.)

While it was still light and I had time, I also pulled the camera package and double checked the alignment of the secondary with the Takahashi alignment scope.  It wasn’t quite as good as I had left it but after fooling with that scope, I concluded that the mechanics of the Tak scope and all of the spacers was so sloppy that the alignment was within the repeatability of that whole mess.  I am not very impressed with how a lot of these so-called alignment tools are made.  It’s like no one understands the basics of mechanical design, which is stunning given that they sell this stuff as tools for precision optical alignment!

That night, the imaging improved tremendously.  SKW immediately showed MUCH less Astig and I was able to quickly dial out the residual coma, which had changed because of pressure from the ring.  Even the defocused star image looked nearly perfect with excellent radial symmetry and very uniform diffraction rings all around.  That retainer ring was clearly the cause of the problem!  That night I snagged three Lum subs with FWHM just a hair above 1”—right in line with when the seeing monitor said the seeing was the best.

My Screw Up!

So, how did this happen?  I didn’t keep a careful daily log of my activities so I have to reconstruct from memory what happened and when.  When I first learned about the mirror retaining ring, Wolfgang simply told me to tighten the screws to raise the ring.  I turned them all by one turn inward.  A few days later, Mark McComskey sent me a copy of the manual that described this procedure and it specified a half turn inward to lift the ring.  About a year ago, the L500 on my CDK20 went crazy and although I wasn’t there to witness it, it sure looked like it turned the scope upside down at one point.  That event started to weigh on my mind and I was concerned about having the ring positioned too far from the mirror creating a possibility that it be damaged if the scope ever went inverted for some unexpected, uncontrollable reason.  So, at some point shortly before I finished up with the scope, I went back and loosened those screws by 1/3-1/2 turn.  This was a self-inflicted wound and at the time, I didn’t think of physically checking the mirror ring to see if anything was touching.  I had turned the screws way too far the first time, so I was certain that I could lower the ring by a little bit with no problem and boy was that ever wrong!

Last night started with 1” (and slightly under) seeing conditions.  So, I started by taking some 300 second exposures of objects in different parts of the sky just to see how things were working.  All of my subs showed blurry images and some showed pretty elongated stars.  I couldn’t sort any of that out so I went back to the Antenna Galaxies, which have served as my test object.  Early images were pretty blurry but my system showed that in spite of the good seeing, it was working pretty hard to hold focus.  The observatory seeing monitor is a differential seeing monitor that Vincent designed and built—and it is quite good.  However, it measures tilt in the wavefront, which is what produces image translation.  It does not measure focus stability and I think that might be what was going on last night.  My early images were also taken when the object was moderately low—around 35 degrees so I was wary of the conditions even though the monitor showed really good numbers.  After some experimenting with the focusing system, I went to bed and accidently left the autofocus system turned off so my last night of imaging was worthless for assessing image sharpness.

How Will it Perform?

Will I be able to reproduce 1’ imaging?  I don’t know but I hope so.  I’m heading home but as soon as I get there, I’ll be running every night to see how the system works all on its own.  I don’t know what else I can possibly do to tune it up so we’ll see.  Getting everything—the optics, the mechanics, and the mount to work perfectly to regularly have the ability to achieve 1” image quality is extremely challenging.  I reached 1” FWHM with my C14 in New Mexico a few times but the local seeing conditions made that a fleeting experience.  My feeling is that the quality and the aperture of the optics in this scope along with the excellent sky conditions should make this goal much more likely—at least occasionally.  I’d sure like to produce a first image with very tight FWHM values so stay tuned—hopefully it will happen.

John