Life moves on and sometimes it's hard to ignore the mile markers as they go by and this image represents one such marker.  Back in 2016, I started monochrome imaging with a new FLI-ML16803 on a C14 Edge and the very first LRGB+Ha image that I recorded back then was M101 (https://www.astrobin.com/244800/H/?nc=&nce=) taken from Oregon. This image bookends my experience with that scope because it's the last image that I'll take with that camera on a C14 Edge scope.  To be clear, calling that scope a C14 Edge understates what it really is.  Yes, it has C14 Edge optics, which are remarkably good (Strehl ~ 0.92 with a very smooth wavefront); but, very little else is stock Celestron.  It incorporates the custom internal, zero focus-shift, zero backlash focuser that I designed for Celestron.  It has a carbon fiber tube and a custom ultra-stable, pseudo-kinematic secondary mount with orthogonal tilt adjustments.  The highly effective dew control system is fully automatic.  The ONAG guider allows real-time auto-focus capability and the AP1600 mount with encoders is extrodinarily stable.  I put a lot of work and a lot of love into that scope and it has been a super reliable workhorse for the last 6 years at DSW under the New Mexico sky.

This last spring I realized that my energy had turned to my 20" in Chile so I put the scope up for sale.  I advertised it on Astromart and on Cloudy Nights where I expected that I might find a buyer in a far away, light-polluted big city.  The amazing thing is that the most serious inquiry came from a guy who lives almost within walking distance from my house in Bend!  The idea was to sell it in place at DSW and that kind of deal can be a complicated.  Along the way, the prospective buyer offered to pay for a month of pier rental so that he could understand how to operate the scope, see how well it worked, and to try it out.  He picked M101 as a target and we teamed up to take the data for this image.  M101 is certainly a spectacular galaxy and it is among the most popular objects for Northern Hemisphere imagers.  Heck, there are over 100 pages of images of this object just on Astrobin alone!  It had been so long since I imaged this object that I was delighted to have another shot at it.  The buyer's name is Brad Rode and he gets credit as a team member on this image.  We were both unusually busy during this data run so we just let it rip for around 6 weeks and I was stunned to see that we wound up gathering over 70 hours of useable data!

Brad and I finally finally completed the sale of the scope last week and I have to admit that as I prepared the bill of sale,  I felt like I was selling one of my kids!  The good news is that I'm sure that Brad will give the scope a good home and I wish him as good of an experience as I had with it.  It really is a world class instrument and I'm sure that Brad will have a lot of fun with it.

Finishing this image was a challenge.  In spite of all the data we took, I realized that I hadn't taken a fresh series of flats since 2019!  So, we had to quickly fire off a series of flats before we pulled the camera to replace it with the ML4040 camera that Brad wanted to use on his new scope.  Since we had to take the flats in the daytime, I closed the observatory roof and doors and used black garbage bags to shield the panel from any stray light.  Fortunately, the flats came out perfectly.

Processing the data was the next adventure.  I sometime have the mistaken idea that since I've processed a lot of galaxy images, I know what I'm doing.  Nothing could be further from the truth.  I wound up grinding through all this data five times before I wrestled it under control!  The first thing is to remember that when meridian flips are involved, a LOT can go wrong when the data is registered.  The only way to catch problems is to pixel peep the stars in the aligned stack in all four corners to confirm that everything aligns as well as the stars in the center.  The C14 Edge achieves a very well corrected, large flat field at the expense of optical distortion.  That means that a meridian flip introduces non-linear position mismatches across the image.  Fortunately the StarAlignment tool in PI can handle optical distortion but it requires carefully checking each aligned frame to look for small errors.  And if you don't check the "Distortion Correction" with "Thin Plate Splines" alignment, you'll end up with subtle yet significant alignment errors.  Small alignment errors will ultimately result in color problems and profile errors that will become obvious when you zoom in.  This is one of the big reasons that I generally don't use the WBP script.  It is a fantastic tool but I want to catch errors as they happen; not at the end of long process.

I used MureDenoise to control the noise in the LRGB data and a gentle application of Deconvolution to sharpen the galaxy core details.  The Ha signal was added using Martin Pugh and Vincent Perez's excellent method to separate the Ha signal from the red signal and to add it back into the LRGB image (http://www.arciereceleste.it/tutorial-pixinsight/cat-tutorial-eng/85-enhance-galaxy-ha-eng).  As usual, color calibration was a challenge.  Using the galaxy as the white reference tends to generate regions with a green tint.  That is probably due to the fact that this galaxy has extensive Ha emissions with strong red/violet colors that tip the total white balance toward the green.  SCNR was used to dial back the green level.  After five runs at this data I finally arrived at this result and it looks about right to me.  Hopefully it's not too far off.   As usual, C&C is always welcome.

I'll miss that C14 system.  It was a great ride!

- John


Final Version:  After staring at the pervious versions for a couple of days, I decided to take one more run at processing this image.  My goal was to minimize the processing.  I used PCC to color calibrate the raw LRGB combination--and it produced a believable result.  I toned the saturation way down (although it looks even less saturated on AB than it does on my local screen.)  The main color adjustment was to remove a bit of random green fringing on the stars with SCNR.  That shifted the blues toward purple so I corrected for that shift.  The only sharpening was the original Deconvolution on the Lum channel.  The only noise reduction was Demure Noise in each of the 4 integrated color channels.  Masked StarShrink was used to de-emphasize the star field.  I spent 15 minutes on this version.  Let me know if it works.  I have apparently lost touch with what makes up a decent image around here.