Rick Johnson's NGC 4754 and 4762 (way back in March 2011)

This lovely duo was described on Cloudy Nights by imager Rick Johnson as “a fantastic pair.” Rick's discussion appears here: Discussion of NGC 4754 and 4762.

The full-size image is here.

14" LX200R @ f/10, L=7x10' RGB=2x10'x3, STL-11000XM, Paramount ME
 
Nearly all of Rick's posts on CN include a link to his image of some interesting celestial object(s) accompanied by an explanation of the state of observational speculation and science regarding it (them). The discussions are fascinating, and in this case in particular interesting because the galaxies appear to have interacted, yet scientists do not appear to have discussed the matter. Distance estimates are all over the map between 55 and 80 million light years for either galaxy, but the distance estimates seem not to have considered the evidence of interaction.

The image also includes some smudge galaxies and some distant background galaxies, and Rick has researched these, too, as well as two asteroids in the image.

Besides the background information, I like the image itself. It has so much of what I look for in an image.

First off, the stars are the shape that stars should be: they are round. This means something. Rick images with a Meade 14” SCT (LX200R version). I sometimes see round stars in an SCT image, but not often. I do not know all the causes for out-of-round stars in SCTs. I suspect mis-collimation plays a role, but there is more than that. I have spotted what I believe are pinched optics and poorly made (or poorly matched) corrector plates. Usually there are odd spikes that stick out from the stars, sometimes in an understandable pattern, sometimes not.

The fact is, a star is a point source. The shape the point source takes in an image is determined by the imaging system, not by the star. In other words, a star's shape in an image is a snapshot of the imaging system itself. Aesthetically, symmetry is better. I like my stars perfectly round, or, if not, then with symmetrical spikes (as few as possible). Any number of things can take a star out of round. Rick's image has none of them. He's obviously taken the time to work with his imaging system to eliminate each one. In fact, Rick enlightened me on this facet of SCT imaging, and what he said is too good not to pass along:

The spikes you see on SCT images are due to a surprising source, the dirt on the corrector plate. I can't explain it; I was given an explanation by Bob Cox (he did the optics for Mercury through Apollo and the ATM column for years in Sky and Telescope), but it was too technical for me to follow. Somehow a smudge on a corrector plate at the focal point of the scope can create this spike on the equivalent point on the image plane. .... I get these from time to time. If a bright star is on the image field at the point of the smudge on the corrector, it will make a spike or halo or some diffraction artifact. Spider droppings are my main source of these. Since I don't look at images often until months later, they can hang around for a while but only when a bright enough star aligns with the corrector. Bob said if they'd put the corrector "where it belongs at the radius of curvature" this wouldn't happen.

Along the same lines, note that this image was taken at the scope's native focal length, f/10. That would be 3556mm, but Rick said he has extrapolated from the image scale on this image and determined that the focal length was 3660mm. In fact, he says his SCT varies about 100mm—100mm!—in focal length with temperature changes. To get round stars at that focal length takes superior tracking. Initially, I was sure Rick would be guiding off-axis, and I was surprised to hear this image was unguided, as are most of his images.  He says it makes automatic imaging much easier. Rick writes that he makes

a very dense T Point map two hours on either side of the meridian from -15S on toward the pole. I put 800 points in this small area. .... With a dense map it easily can interpolate between points since they are so close together. Takes a couple days to make the map after remounting the scope after its annual spring cleaning but worth the effort!

Ah, Tpoint. I see. And, no surprise that Rick shoots from a Paramount ME. The accuracy in the tracking is a testament to great mechanics and software.

Another thing I like about this image is its modesty. Rick doesn't say, and it's not readily apparent, but there is another distortion from NGC 4754 on the lower side, moving to the left and down, opposite the one that is going right and up. If one stretches the image quite a bit, it's obvious. Rather than force the galactic spike into open view with selective processing, Rick has let the data speak for itself. It's a very dim feature, Rick's data barely catches it, and he has let it be. Rick is out to explore the universe. Letting the data do the talking is part of that mentality. Of course, there is some processing involved, and sometimes stretching of galactic centers and stars needs to be adjusted so that they do not blow out or unduly distract, but the data from the sky is left in the image, which is why you will see asteroid trails, for another example.

Finally, where does Rick find these targets? At this focal length, a great deal more of the universe opens up. I applaud Rick for going a step deeper and introducing us to the wonderful objects further out. I have some new goals for my own imaging after having seen some objects from Rick.

I asked Rick for a little biography, and he sent this:

I first got interested in astronomy when a article in some magazine (Life?) in 1953 mentioned that in the spring of 1954 Mars would be the closest it had ever been since the 200" scope was built, and it would answer once and for all whether the canals were real or an illusion. Of course that didn't happen, but I was convinced it would and also that I wanted to see first hand. I priced a 6" scope at about $200 ($1675 in today's dollars). No way that would happen! I found an astronomy book at the library that said, “Build your own 6" scope for $35” ($300 today). That was still steep but possible (gas was $0.25 at the time). I ordered my own copy of the book (long lost) and ordered the mirror blanks and grinding kits. Turned out you made the eyepiece lenses as well! The instructions you got were 3 pages long. Totally useless. I struggled for over a year but by opposition in May I was ready. All I saw was an orange-red amoeba-like blob. I was disappointed until Life published the 200" photos that failed to decide the issue after all. I later learned the mirror I'd made was great but the eyepieces I'd made were awful. A local amateur loaned me a good eyepiece and I was in heaven until I could afford my own. By 1955 I was photographing the moon and have been at it ever since. Finally after retiring and building my dream observatory, I can take images far beyond anything I ever dreamed of taking 57 years ago.

After watching the tremendous gains in both equipment and knowledge over those nearly 60 years, I wish I could stick around to see what the next 60 years bring!

You are living the dream, Rick! It gives me hope for my own future.

Rick images from the shores of a lake in rural Minnesota, not far from Paul Bunyan State Forest. He images about 150 objects a year and is currently fourteen months behind in processing data! What a wonderful problem to have. Please keep'em coming, Rick.