Eclipse Cloudout

A couple of weeks ago, the Moon’s orbit carried it into the Earth’s shadow during the early morning hours of March 14th. This eclipse was ideally positioned for those of us in the United States, so I was excited and hopeful to have a chance to witness it and capture some beautiful shots during totality.

I started monitoring the weather forecast in earnest on Thursday morning. The sources didn’t agree much. Underground Weather and WeatherBug predicted a significant cloud deck, whereas Astropheric and Clear Outside were far more optimistic. It seemed like an offshore system might creep westward and potentially cloud us out. The pattern suggested it might be advantageous to try and outrun the clouds by heading to western Maryland or West Virginia. However, since that wasn’t a sure thing, I opted for the comfort and convenience of watching from my backyard.

I downloaded and set up the Lunar Eclipse Timer and Camera Controller (LETnC) application the day before. I had used the solar eclipse counterpart to this software during last year’s Total Solar Eclipse, so I was hoping to leverage it for this lunar eclipse. I ensured that both my Canon Mark II and Canon t6i had charged batteries. The former would provide nice views of the full Moon through the 80mm Vixen telescope, while the latter could be used for a variety of shots with the 300mm telephoto lens.

Around 9 PM, I brought the equipment out from the garage, aligned the mount, and balanced the Vixen on it. The iPolar was acting a bit quirky, so it took longer than expected—I even rebooted and reinstalled the software to no avail. Fortunately, there was plenty of time before the eclipse would start, and the rough alignment provided by the glitchy iPolar would suffice.

As we approached the point where the Earth’s penumbra began to creep onto the disk, I took a shot of Luna in her pre-eclipsed state. I noticed some very high, thin clouds creating a slight glow around the Moon, but through the telescope, their impact was negligible. Although chilly, the seeing seemed fairly good—around 5/10, with transparency at about 6/10.

Uneclipsed Moon

Slightly before midnight, the Earth’s outer shadow touched the Moon. However, as usual, the effect was too subtle to see. Only when we got within about 15 minutes of the first contact with the darker umbra could one begin to appreciate a darkening on the Moon’s limb. By C1 at 1:09 AM, the clouds were slowly thickening, but not enough to seriously impact the spectacle or my photography.

A few minutes after C1

Over the next hour, I continued to document the encroaching shadow, re-centering the Moon in the Vixen and hopping over to the telephoto setup to reel off a few bracketed shots. Unfortunately, the cloud cover seemed to be matching the depth of the eclipse, gradually but inexorably thickening as the minutes ticked down towards totality. I had to edit the LETnC script to make the exposures a little longer, and it became clear it would be a race to see if the clouds would win out and block totality. A look at the satellite infrared image was not at all promising, with offshore clouds pushing into our area.

About 30 minutes before totality

By a little after 2 AM, it was clear that the weather had won this round. As the Moon was further engulfed in shadow, it was first lost from eyesight, and then even the telescope's light-gathering advantage was overwhelmed in my effort to continue photographing the eclipse. When C2 arrived a little before 2:30 AM, there was nothing to see, and the hope of witnessing the beautiful coppery orb floating in the spring sky slipped away along with the Moon.

I retreated inside to rest a bit and set an alarm for 3 AM, just in case the clouds relented. But when I checked the window, there was still no hint of the Moon in the sky, so I turned in for the night. Interestingly, some other members of HAL went out to Alpha Ridge to view the eclipse, and their skies held clear enough up until totality to capture some nice images. And so it goes in this often-frustrating hobby that depends so heavily on having a clear sky above!

Leveraging Starlight for Sharpening Planets

The field of digital planetary imaging is where art meets science, particularly in post-processing. After using our preferred tools to distill a video of several thousand frames into a stacked and aligned image, there is still much work to do. We need to refine it into a sharpened view of the target before applying some tweaks in a program like Photoshop. To achieve that sharpened image, we have two techniques at our disposal: wavelet sharpening and deconvolution.

Wavelet sharpening is a key feature of the freeware application Registax6, a staple of planetary imagers for many years. The author of the software, Cor Berrevoets, has not issued an update to the venerable program since 2011. He has, however, created a successor in the form of another freeware application called waveSharp. Both of these tools decompose the selected image into layers - from large-scale components of the image to fine scale. By adjusting the sliders, you can selectively enhance these aspects of your image. The finer scale adjustments must be done with a light touch to avoid introducing significant noise to the final result. Fortunately, one can combat the noise by suppressing the finer scale adjustment.

The ability to apply deconvolution is appearing in more tools for the planetary imager. One excellent new addition is the Lucky Stack Worker (LSW) freeware application (a video by the author, Wilco Kasteleijn, is on the ALPO channel). Another is AstroSurface, an application with extensive filters and functions for not only the planetary imager but the deep sky enthusiast as well.

So, what is deconvolution? In brief, it is using a contemporary representation of an Airy disk to help recover detail lost through atmospheric turbulence, soft focus, or optical issues. Under perfect conditions, when examining a moderately bright star, you would expect to see a small disk with diffraction rings emanating from it, known as its Point Spread Function (PSF). The interface on the LSW has two checkboxes - one for "Deconvolve" and one for "Sharpen" (i.e., wavelet sharpening). If we select the Deconvolve and select the "bullseye" adjacent to it, we see that LSW is offering us a synthetic PSF with sliders to allow us to adjust it.

Impacts when adjusting the Seeing Index slider

You could take a few minutes before or after your imaging run to inspect a nearby star and make a note of its Airy disk appearance to emulate it in the synthetic version. But why not record an image to capture the PSF for that particular imaging session? This is exactly the sort of thing that Wilco Kasteleijn advocates in the LSW manual and references a nice article by Marco Lorenzi on how to do this.

A couple of nights ago, Astropheric was displaying that the seeing would be "average" with temperatures in the 40s, so it was an opportunity to try this technique and maybe gain some experience acquiring a PSF image to leverage in my processing. Like a deep sky flat frame, the PSF image should be taken with the same imaging setup and without pointing the telescope too far from the target.

My first attempt using a star near Jupiter did not yield results, as it ended up being too faint and requiring a longer exposure. That, in turn, blurred the Airy disk by its scintillation. For Mars, I targeted a brighter star and had more success with a frames-per-second rate nearing 100. Even so, it is challenging to get it right; in retrospect, I should have lowered the gain further to avoid "blowing out" the Airy disk.

The PSF image taken during the imaging run

So, here are the results! Even with only a fair PSF image processed by Autostakkert, the LSW did a nice job of recovering the details from what turned out to be sub-par seeing. Applying sharpening and denoising to the image resulted in a reasonable, if not admirable, image showing albedo features, the polar cap, and likely cloud features.

To me, this technique of capturing a PSF image as part of the Lucky Imaging session holds great promise. As a final note, here is a Copilot-assisted comparison of how these two techniques help us achieve fantastic planetary images.

Chasing Planets: January's Observations and Challenges

The media has been hawking the auspicious "planetary parade" that allows an observer to see 6 planets during frosty January evenings. Of course two of those (Uranus and Neptune) are not naked eye objects. I do not mind articles that generate interest in our hobby, but my fear is always the "over promising and under deliver" risk.

However, January was indeed a fun month for us planet observers. Mars was occulted by the nearly Full Moon on the evening of the 13^th, and then two days later came to opposition for this apparition. Jupiter was positioned well and decided to throw a major eruption amid its North Tropical Zone southern jet stream on January 10^th, garnering a lot of attention. Venus also ascended the Zodiac after lying close to the southwestern horizon most of its current evening apparition, reaching greatest elongation on the 10^th heading for its highest altitude in the western sky on February 2^nd. The only downside has been the weather with classic winter turbulent seeing amid very cold temps.

Mars Occultation

The skies were clear but quite cold for the occultation of Mars. I set up the 10" Cyrus telescope and verified its collimation. The Moon served as a convenient focus target as I set up about 20 minutes before the scheduled disappearance. I knew that the difference in brightness would be a challenge and thought I'd have time to fiddle with the gain setting right before the occultation, but it happened so fast that I really did not get a great capture with the Moon very overexposed. Still, it was a very cool event to watch the Moon relentlessly approach the red orb and cover it up with about 30 seconds.

The Moon ready to cover Mars

January 17th Session

The evening of the 17th was predicted to have average seeing and temperature right around the freezing mark, which is fairly good for this region in winter. I again set the Cyrus scope out early to cool and verified its collimation. As Venus emerged from encroaching twilight I set to work on capturing our sister planet. 

Starting with the Deep Red filter (642+nm) and no Barlow, Venus provided a bright target upon which to focus. Doing a 5 minute capture resulted in a nice image, showing the planet past dichotomy and a common cue-ball appearance. I have yet to truly discern any cloud details in IR light.

Swapping out the Deep Red filter for an IR-block and UV set, I retargeted the planet and adjusted the settings to bring up the brightness in the fainter UV light. I could make out even on the on-screen image that there was uneven brightness in the sunlight reflecting off the Venusian cloud tops.

Processing produced a nice greyscale image with a some cloud structure. Interestingly, a well defined cusp cap was not really seen, although you might argue one was around the south pole region. This is somewhat in agreement with the UV Venus images I have been seeing submitted to the ALPO for the current evening apparition; cusp caps are not as prominent as I believe they were during the last apparition.

By now Saturn was visible in the deepening twilight, close and to the left of Venus. I figured why not give it one last capture since the upcoming mid-March solar conjunction and my obstructed western horizon meant it would soon be inaccessible. I added the Barlow back into the imaging path and returned to the Deep Red filter. Seeing was not very good, and the rings had closed up again compared to a few months ago. I had enough juice in the laptop for two 2-minute captures, resulting in a sub-par image where it is hard to even detect the globe's shadow being cast against the rings. Au revoir Saturn - until we meet again in the late spring!

Getting the AC adapter hooked up to the laptop I next swung over to Jupiter. My hopes were to get multiple captures into the evening if the weather held, recording not only the very recent North Tropical Zone southern jet stream eruption but also that continually expanding disturbance in the South Equatorial Belt that started back in November.

The seeing ended up being fairly good over the course of about 5 hours, allowing me to capture a lot of interesting features, including that NTrZ outbreak. As we began to close in on midnight the gods conspired to end my run as the cirrus clouds began to thicken and the tracking on the Celestron mount suddenly had a stall (it is always amazing how quickly the planet exits the frame when this happens). Rather than fight to recenter and continue amid the deteriorating seeing and transparency I decided to wrap things up on Jupiter.

In the middle of my Jupiter captures I had to take a break due to the location of the planet. When an object is high and near the meridian, the Cyrus telescope tube runs up against one of the tripod legs. The resolution would be to raise the tube up off the saddle, somewhat like extending with a pier. But that would be a lot of effort and so is not likely to happen in the near future (if at all). 

But rather than waste the time I opted to do a run on Mars which had just passed opposition a few days earlier. While at only about 13" in size the disk was large enough to take in some nice albedo features such as Syrtis Major setting and Sinus Sabaeus and Sinus Meridiani on the central meridian. The NPC was also a brilliant white and was a good feature to leverage in trying to get the best possible focus. Hopefully I will get in a few more sessions with Mars for this apparition, but it's going to shrink in size quickly now that it is past opposition.

While I did not achieve all my goals for the evening (I missed seeing the SEB disturbance on Jupiter), it was quite a good night for the middle of January. It reflects why planetary observing provides such a rich experience for the amateur astronomer.