Under the Influence

The Howard Astronomical League lost one of their luminaries last month with the passing of Bob Prokop. The club never had a more ardent supporter than Bob, serving in the leadership role as a club president and supporting many of the club's outreach activities. He loved our hobby and it showed in many ways.

While I never had the opportunity to develop a personal relationship with Bob, I was certainly under his influence. He had the ability to advocate for the spectacular above us as well as the sublime. Was Mercury having a favorable apparition? Bob would be posting about it in the email group. Was the Moon's libration tilting a far-flung crater into a better position for us to grab a look at it? Our lunar expert knew the when, where, and how of the circumstances. On more than one occasion his exhortations found their mark and nudged me outside to hunt down what Bob was showcasing.

Bob was indefatigably upbeat about any clear night. Do NOT complain to him that the full Moon was ruining the evening lest you be embarrassed by Bob's retort as to the lunar features, asterisms, or other bright destinations that would not be suppressed by a glorious full Moon. And everyone in the club knew that he wasn't Googling that information, it simply flowed effortlessly from his years gazing up at the heavens. I still recall a passing comment that I made - something along the lines of "only a mediocre double star" - to which I was called to account in a most affable manner.

One thing that Bob and I were resolutely in lock step on was the value of star-hopping. We both cut our astronomical teeth by using instruments that required you locate your object rather than simply dialing it in. To quote Bob, "Of course, I am also the nut who has my telescope on an unmotorized alt/az mount with no finder scope... and can still find that 9th magnitude star faster than anyone with their fancy go-to software!" No brag, just fact.

I understood his lament that "today's kids" miss the anticipation and preparation involved when stalking a faint object, not to mention the thrill and sense of accomplishment when it finally appears in your eyepiece. Plus, who knows what stary vistas and uncharted beauty you may encounter along the path to your objective? While I have succumbed to the GoTo siren with my latest mount, I still do put the keypad down at times and drive myself to my destination. 

While my interactions with Bob were virtual, they were valued nonetheless. He was a welcome inspiration and source of knowledge for me and many of my club peers. He was one of those special people I've had the good fortune to come across who's love of the night sky was palpable and contagious. 

Getting Started

It's a question that I (and most amateur astronomers) get from friends from time to time: "I want to look at stuff in the sky - what sort of telescope should I get?" It is a tough question to answer because there are a multitude of variables (like how dark your sky is), a wide variety of celestial objects for which each has a "best" instrument, and the prospective user's existing familiarity with the night sky. 

It is understandable why folks get the urge to grab a scope and go out into the night. The images sent back from our spacecraft are stunning to say the least. And while most people grasp that their telescope is going to fall short of a billion dollar scientific instrument, they likely also have acquaintances posting to Facebook or Instagram with some pretty cool stuff. That's part of the problem with social media - it makes stuff look easy since we only display our victories, not the flubs we made getting there.

OK, so rather than totally dodging the question with a "it depends..." answer, let's consider the following scenario. We have a newbie who really knows very little about finding things in the night sky and who lives in suburbia (where their sky is not going to be bleached out by a ton of lights). They'd love to see a galaxy, some beautiful star clusters, and maybe a nebula (gas cloud) or two. They'd like to see Saturn's rings and Jupiter's Great Red Spot.

Those two sets of objectives (Deep Space Objects [DSO] and Solar System Objects) are somewhat mutually exclusive for our beginner. DSO present the challenge of being faint and potentially very difficult to find for a new telescope user. Of course you can buy a scope with computer assisted GoTo that will point the telescope to the object if you can align it properly (not to mention that you'll be jumping into the hobby for a much bigger financial bang). 

Planets, being brighter, are much easier to find with your telescope. However, features like the polar ice caps of Mars and the belts of Jupiter are more subtle than you might imagine to pick out with your eye. It's almost like playing an instrument with planetary observing - you need practice before you can detect some of the cool things your telescope can show you.
So - how can you break into this hobby without breaking the bank? The answer lies in a nice set of binoculars. Most people don't even consider them because they believe they are not powerful enough. The truth is that their wide field and additional light gathering power will indeed open up a lot of celestial DSO for you. They have the added benefit of being user friendly - no need to align anything, just pick them up and step outside to begin exploring. And - they pack easily for that trip to the beach or the mountains where the skies are much darker than at home.

There are a lot of sites with binocular recommendations. One thing to know up front is that the first number in the binocular description is the magnification (or power), the second is the diameter of the front lens (larger diameter = ability to see fainter objects). I personally own two pairs: a 7x50 by Celestron and a 15x70 by Oberwerk. The former are reasonably light and easy to use, the latter are a bit heavier but give wonderful views. I'd recommend a 7x50 or 8x56 for someone starting off - something you should be able to do for under $150 easily.

Binoculars - ready to go & user friendly!

"Sky Safari" App

Equipment is only half the battle. The really important thing is to begin to learn your way around the sky so that you can find things to look at. You don't need the binoculars to start this, your eyes and a star chart (or, even better, an app on your smart phone that can simulate the sky where you point the phone) are all you need. Start learning to identify the bright stars, then trace out the other stars in the constellation that has the bright star. From there see if you can locate stars in some of the dimmer constellations between the bright stars. As you do this you'll also become familiar with how astronomers quantify the brightness of an object (its "magnitude"). Once you've made friends with the stars overhead you can use them as markers to find the more interesting stuff.

Like what? Well, on a crisp February night you could swing by the Orion Nebula, a hydrogen gas cloud birthing new stars. Or high up in the sky catch the Seven Sisters (Pleaides), a beautiful collection of diamonds in the sky. For something more subtle you can track down the oval smudge of light that is the Andromeda galaxy lying some 2 million light-years from Earth. And since Jupiter is out in the evening sky take a moment to check it out - you may not see the Great Red Spot but you'll likely get to see some of its moons very close by as little stars. For other ideas I'd suggest picking up a book such as Touring the Universe Through Binoculars and let it guide you to a lot of fascinating destinations.

The tiny cloud represents the Orion Nebula
(It looks much better from dark skies)

An important lesson that you'll quickly learn is that when it come to the night sky a camera is much better equipped to show color and detail than our eyes. The camera opens its lens and collects light for many seconds, our eyes take an instantaneous reading of the photons. As such you'll not see the pinkish tinge in the Orion Nebula nor the spiral arms of Andromeda. But, you still do get to see them first hand, and that can be rewarding and exciting as well.

Orion Nebula - 2 sec Exposure

If you are still at it with your binoculars some 6 months later and you want to take the next step, then I'd say invest in a telescope. A great idea would be to go to a local club's star party and look through a variety of telescopes. But even if you can't, you cannot really go wrong getting an uncomplicated Dobsonian telescope in the 6-10" mirror size range. The additional light gathering power and magnification will open up a much larger range of DSO that you can hunt down from your yard.

Of course if it turns out that the thrill of seeing faint fuzzies in the sky does not give you the satisfaction you were hoping for the binoculars can always be used for checking the wildlife in your backyard - or getting an up close look at the horse you're betting on in the fourth race at Pimlico. 😏

C/2022 E3 (ZTF)

Last March the folks at the Zwicky Transient Facility picked up an object using their wide field survey. It was soon determined that this was a comet heading inbound for a rendezvous with the Sun after a 50,000 year absence. The orbital calculations along with the comet's brightness led astronomers to predict that C/2022 E3 (ZTF) might become a naked-eye object soon after its perihelion on January 12th, peaking as it makes its closest approach to Earth on February 1st. Given it's the brightest comet to grace our skies since Neowise in the summer of 2020 I thought it was worth trying to observe it and possibly get an image or two last Friday.

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Jan 27, 2023 21:45 ET from Towson, MD
Clear skies, 35°F with light wind
Seeing 3/10 Transparency 9/10

First up is a quick scan of the area just a little NW of β Ursae Minoris (Kochab) using the 15x70 Oberwerk binoculars. At 2nd magnitude and a deep orange color it is easy to pick out Kochab from even my Bortle 8 skies to start the brief star hop. A little pan to the right and up and I can quickly see what appears to be a tiny, weak nebulosity. Working to hold the binoculars steady enough to get a good look I confirm that we have a comet that should be an easy target.

Rolling the 10" Cyrus Newtonian out I ditch getting 2-star alignment in favor of just using the finder scope to target the fuzzy visitor. It's readily visible in the spotting scope so it doesn't take long to sweep it up in the 40mm eyepiece. It's set in a nice star field and there is a star-like nucleus along with a diffuse, weak haze representing its coma. No real color can be discerned. Bumping up to the 25mm Plossl to darken the background a bit the coma is a little easier to see but in all honesty I cannot make out any shape to it that would let me guess as to the presence of a tail and its direction. It certainly seems to be at about 5th magnitude as predicted.

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To round out my ZTF session I grab my Canon camera and put the kit 70-300mm lens on. This time I try to avoid focus issues by targeting the almost 1st quarter moon and dialing it in to be as sharp as possible. At 200mm focal length I should get a reasonable size for the comet, and the rule of 500 suggests an exposure of 2½ seconds. But a quick test exposure shows unacceptable trailing at 2 seconds, so I drop it back to 1 second and begin firing off pictures, accumulating about 100 of them. From there I drop the focal length down to 70mm and run a series of 6 second exposures before calling it a night.

A few months ago Sky & Telescope ran a nice spread on nightscape photography. Among the tools that they mentioned was Sequator, a free program that I had not heard of before that stacks your images and can "freeze" the foreground. Sounded like a perfect tool to use for my ZTF images, so I downloaded and did a quick YouTube video to get me oriented to its use. I have to say it was much easier and faster than my standard go-to in this scenario (Deep Sky Stacker), although it could not keep my foreground tree from blurring, likely because of the breeze shifting its branches. But the resulting TIF yielded a very nice result after having some tweaking in Photoshop, especially given the minimal effort I put into the capture.

While the comet is outbound to the Kuiper belt deep freeze, we do have a couple of opportunities to get some interesting shots of it as it photo-bombs a few celestial luminaries as it leaves the stage:

Feb 6: The comet swings close by Capella

Feb 11: ZTF buzzes Mars

Feb 15: The green ghost will contrast nicely with nearby Aldebaran

While comet C/2022 E3 ZTF is likely to fall short of the media hype, it still is an interesting and readily accessible example of what most comets look like - star-like nucleus encased by a puffy, tenuous cloud. 

The Pixel Sweet Spot

Earlier this week the forecast was for an evening of average to perhaps better than average seeing with cold (but not biting) temps. I rolled out the scope a little before sunset to begin cooling and got things ready - with Jupiter just past quadrature it is always going to be highest in the sky as soon as it becomes visible. 

I did the routine alignment, collimation check, and finder alignment before finally popping in the ZWO camera. Activating the camera I was greeted by a strange sight - an emerald green Jupiter. At first I thought maybe a Debayer setting was off in the capture interface but soon noticed that the histogram was not registering in blue or red, only green. I rebooted the laptop hoping maybe that would restore things, but no luck. I brought up a different capture application, but it, too, sported a green globe.

Rather than admit defeat I located my retired Imaging Source camera and popped it into the Barlow. The view and histogram confirmed that we were back to getting a color image, but I immediately was struck by how much smaller the image appeared to be. Hmm - what was that about?

It turns out that my older camera, a DFK21AU042, has a pixel size of 5.6µ whereas my ASI178MC has a size of less than half that, checking in at 2.4µ. The formula for calculating how much sky each pixel registers for your setup is as follows:

  (Pixel Size/Telescope Focal Length) * 206.265  

For my setup using a 2.5x Barlow that becomes:

DFK21AU042 = 0.31"

ASI178MC = 0.13"

The theoretical ideal for planetary imaging for under average seeing conditions is around 0.15" per pixel (Note that this is different than DSO imaging, where the average is about 1-2" per pixel). Clearly, my ZWO camera is a lot closer to the mark, and the better thing to have done would have been to stop and swap out my 2.5x Barlow for my 4x one to get a little lower arc-second/pixel value. But the window of calm seeing that we often get shortly after sundown wouldn't allow that, so I forged ahead.

Below are comparative images taken about a week apart of roughly the same Jovian longitude. It is pretty obvious from it that we lose resolution in the image acquired using the DFK21AU042 camera.

Is the image from the older camera terrible? No, hardly. We can still make out details like Oval BA and anti-cyclone storm A1 - something that was unheard of using film a few decades ago. But in astronomy, and in planetary imaging in particular, it is all about getting all the parameters as ideal as possible so that you can capture all the details available given the seeing conditions. Hopefully I get my ZWO camera fixed, but in the meantime I know from experience now to at least break out the 4x Barlow to try to get closer to that desired arc-second/pixel value.

Frost Moon Eclipse

For the second November in a row, the Moon was scheduled to take a plunge into the Earth's shadow (only this November it'd be a total eclipse rather than a very near total eclipse). With the forecast for the early morning of November 8th being a bit questionable (and not taking the workday off), my plan was to set an early 5am alarm to check the western sky for clouds. The weather gods ended up being kind as I could see the eclipsed Moon hanging low in the sky with minimal clouds. I threw on street clothes, grabbed the camera waiting on the tripod in the kitchen, and headed out to locate a spot along the street with an unobstructed view of the event.

It was chilly but not frigid (50°) with some scattered clouds amid a pretty transparent sky overall (7/10). There was a sporadic breeze out of the north. I took some time to just visually enjoy the sight of the deep orange lunar disk hanging about 10° above the western horizon between a gap in the trees. It seemed to be a little on the dark side as lunar eclipses go, probably a Danjon 2 by my estimate. I thought about how these events are beautiful occurrences to us but that centuries ago they would likely strike fear and dread to the average person. Iconic Taurus and Orion looked on nearby along with brilliant Mars, but the spot occupied by Luna was devoid of visible stars given my Bortle 8 suburban skyglow. 

 

 

I racked the telephoto out to 300mm and worked on getting a focus. I then started firing off a set of shots, altering the exposure time to hopefully get one close to approximating the visual appearance. I then dropped the focal length down for some wide-angle shots before calling it a successful event as the Moon slid further to its approaching western horizon rendezvous.

Downloading the shots to the computer showed that, yet again, I had managed to just miss the desired razor-sharp focus. To me this is the Achilles Heel of DSLR cameras – they excel at allowing multiple photos without worry of film expense and even a digital darkroom, but gone are the days where you could reliably slide the focus ring all the way over to infinity and know that you were indeed focused at infinity. Some of it might have been that northerly wind buffeting the tripod a little, but probably 90% of the issue was my not being attentive enough to the focus.

 

I wonder how many lunar eclipses I’ve now taken in over the years. It would be hard for me to go back and tally them as earlier on I certainly didn’t keep records, at least nothing that survived till now. Whether it’s 10 or 20 I can certainly say that they are one of the most pleasant spectacles that Mother Nature provides.

 

Putting It to the Test

One of the many sections of ALPO^[1] is the Online section, of which I’m an assistant coordinator. While currently this means I’m focused on helping to maintain the organization’s website and post observations to the galleries, I think there can be more to the section.

Born as the “computer” section in response to the PC revolution and its impact on our hobby, the original aim was more towards what sort of software was available to assist the amateur planetary observer. To me, this has more relevance than ever given how integral software has become in processing most observations today.

There are many competing products out there that one can choose to align, stack, sharpen, and tweak their video capture into a valuable image that documents the state of an astronomical body for a given point in time. Less available to the amateur observer is a sense of how the software works or what approach is preferred (or should be avoided). Often the individual approaches it as a bit of a black art, playing with settings in the interface and seeing if the outcome is better or worse. While the learning curve is perhaps not as steep as with something like PixInsight for our deep sky imaging brethren, there are still many nagging questions when doing a planetary imaging workflow – “Am I doing this right?”

This is where I believe that the ALPO Online section has a role to play harking back to our roots as the “technology” arm of the organization by conducting studies to shed light on common questions. As an example, when setting alignment points on an image in preparation for alignment & stacking, what size works best? How important is that? What is the current theory on it, and does that theory hold when tested? Questions such as this are not just academic, their answers can impact the quality of our output.

With all this as background I’m announcing an effort to tackle some of these software setting questions. Lifting a page from the Zooniverse folks, my idea is to generate a set of images where, to the best of my ability, all parameters are the same except for one and then invite the amateur community to score them. With a sufficient number of evaluations, it should be possible to make a statement (and perhaps a recommendation) on the optimal setting to use when processing your video into a final image.

I have defined my first inquiry and worked up a set of images to use in the test. The posit is that when processing a video taken under only fair seeing it is better to use larger alignment points, whereas a capture under very good seeing benefits from smaller sized alignment points. The theory is well explained by Christophe Pellier in Chapter 7 of his excellent book Planetary Astronomy:

“An AP is defined by small boxes and the alignment will be done based on the details that are present inside of it. If the image is noisy and with low contrast, a size that is too small will prevent the software from performing a comparison because of a lack of detail found in some of these boxes. On the other hand, if there is considerable detail present a smaller size AP will increase the accuracy of the alignment.”

Perhaps I am tilting at windmills here in thinking that I’ll get enough participation, who knows? I’m hoping to be able to not just confirm the theory but to also offer some qualitative assessment of its impact on one’s resulting image. If you would like to participate in reviewing the six sets of images, please visit my new ALPO Research & Investigation web page that I am hosting on my personal website until such time that it proves viable and suitable for deployment on the official ALPO website. And thank you in advance for your time if you do decide to participate!

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^[1] Association of Lunar and Planetary Observers

More Than Meets the Eye

Sept 20-21, 2022  

While prepping for my HAL talk last month I stumbled across the fact that the Astronomical League has a Jupiter Observing program among its offerings. It's a program whose objectives I've certainly met over the years, but thought it would be fun to officially claim the prize. 

One task is to collect a series of observations on the 4 bright Galilean moons and interpret your data to characterize the moons and their orbits. You need a couple of sessions spanning over two hours, and this evening's clear skies (and an added bonus of a Ganymede transit) was a nice opportunity to meet some of the program's requirements. I decided to use the 80mm Vixen refractor since it is easier to set up and more than adequate for recording the bright moons.

By 10:30 I had Jupiter centered in the eyepiece. Ganymede's large and stark shadow is not hard at all to pick up on, even in this small aperture. While I could have simply sketch the moon positions, I opted for a set of video images at 30 minute intervals as a better approach. 

Galilean Moons, with Ganymede in Transit

When I finished the first capture I did a quick processing to see what I had. I was actually a little surprised at the detail on the planet using such a small aperture. It led me to wonder just how much detail could I get using the Vixen if I tried? 

Since I needed to wait a half hour to make my next capture I decided to explore the question. I popped in the Meade 2x short Barlow and brought the Region of Interest (ROI) as tight as I could. This smaller capture area allowed the frames-per-second rate to go from 96 to 286, increasing the chances of leveraging those microseconds of steady seeing into a nice photo.

Next day I set to work running the video capture through my workflow - PIPP, Autostakkert3!, and Registax6 to produce a final image. Although the details are puny compared to what the 10" Cyrus reflector produces, they are pretty amazing given the aperture. Not only do we get the major bands, but features such as festoons in the NEB, Ganymede's disk as it begins to egress, and even Oval BA can be clearly identified in the tiny image. 

Would one suggest an 80mm refractor as a good instrument for planetary exploration? Not really - but it clearly has a lot more to offer compared to what you'll see behind the eyepiece when you team it up with computer assisted planetary imaging. Visually it takes a little effort for me to discern Oval BA using the 10" with a suitable filter. Snaring it in a capture using a telescope with 3 inches of aperture is really quite a testimony to the high-contrast quality that refractors offer as well as the power of using the lucky imaging technique. If you use a similar scope as your main tool for exploring the night sky you might consider adding on a planetary video camera and discover for yourself the enjoyment of capturing features that you'll likely never see visually.