The Green Comet and the Red Planet

Belated post but I have several things to share so playing catch-up....

In my last post, I shared my first attempt to capture The Green Comet, the solar system body with the official name C/2022 E3 (ZTF). By the time I was shooting it, the comet had faded enough that capturing it in the heavily light-polluted urban skies where we live so it was just a dim, green smudge in that shot. 

Much of the challenge in taking that shot was the glare of the Moon. About a week later, the Moon wasn't rising until after midnight so I had an opportunity to try again. Thankfully, the skies were clear on February 11th because in addition to the period of moonless skies that night, the Green Comet was within the same telescopic field of view as the Red Planet, Mars. 

To boost my prospects of capturing a better image of the comet framed in the same skies as Mars, I also went looking for a spot with less light pollution. My initial plan was to shoot from out by Lake Ray Hubbard. The light pollution at home is about as heavy as it can get, classified as 8-9 on the Bortle scale, whereas the skies out at the lake are darker, Bortle class 6. That's a long way from the truly dark skies in Big Bend (Bortle class 1) but I was limited to what was available in the Metroplex and I've had a lot of success over the years shooting things like meteor showers out there. 

Unfortunately, the spots I usually went had too many lights in the direction of the comet so I had to try someplace new. Consulting a light pollution map, I picked a spot a little south of Forney, outside a town called Talty. I found a spot at a turn-out off of an FM road we used to drive to get to our lake cabin at Cedar Creek Lake that was Bortle 5. I set up my telescope and started shooting. After capturing dozens of shots plus calibration shots, I packed it in and headed home. 

After a few days working on post-processing the images (see prior post about the process involved), here is what I ended up with. 

Although not perfect, I am pretty satisfied with the result. With the Green Comet on the left, Mars on the right and the stars of the constellation Taurus the Bull in between (the bright star at bottom is Tau Tauri, in the horn of Taurus), it's a lot closer to what I was hoping for than my last attempt. To do any better than this, I probably would have needed an equatorial mount capable of tracking the comet movement (vs. tracking the stars with my current tracker). If you see other shots of this comet where the tail is more prominent, it's likely it was shot with a telescope on an equatorial mount. 

One thing to note about this image is, yes, that really is Mars, not a star (or the Sun). Because I was taking long-exposure shots to capture as much of the comet as possible, then Mars (far brigher than the comet) is a bit over-exposed. That's why it appears more yellowish/white instead of rusty red. The down-side of an over-exposure like this ("blown highlights") in a digital shot is that the over-exposed area is lost data... there is nothing there to edit so no way to correct it. At least not without adding something to the image that wasn't naturally there. 

I learned a lot planning for and executing this shot. Sadly, it's unlikely I'll ever get another chance to shoot a comet and Mars like this but there are plenty of other interesting sights in the night sky that I'll be able to shoot, applying what I learned shooting the Green Comet and the Red Planet. 

As always, click on the image to see it big!

The Green Comet

Well, the first thing that came to mind seeing news headlines about The Green Comet was a flashback to the 60s TV show The Green Hornet staring Bruce Lee. :-)

Seriously, this has been a newsworthy comet. While it wasn't bright enough to be seen except under very dark skies and/or with optical assistance like a telescope, as you know if you've followed the news, it is a singularly unique solar system visitor. Check out sites like EarthSky.org for more details and some of the more interesting images. 

For my part, I had hoped to capture comet C/2022 E3 (ZTF) with my rig (Evostar 72ED on a Star Adventurer tracker, using a Nikon D750). Unfortunately, the North Texas weather hasn't cooperated. Last week when it was at its closest to Earth (and at its brightest magnitude), we were in the throes of a winter storm. By the time we had a night with relatively clear skies on Friday night, we also had a nearly full Moon. It was also still very cold outside. If it had been a moonless night, I'd have packed things up and headed out east of town to darker skies to shoot but since I knew the Moon was going to make it hard to get really good shots, I just set up in my backyard. At least I could duck inside from time to time to warm up. 

Here is the result. See below for more on how it was created. 

Comet C/2022 E3 (ZTF) captured in my backyard
February 3rd, 2023

Between the light pollution and the glare of the Moon, it was hard for me to pull out much detail but you can at least see the dim fuzzball of the comet's core. The comet was in a region of the sky without any bright stars but the few brighter ones on the right side of the image are in the constellation Camelopardalis.

Still, it was time well spent. It was the first time I've gone through the process of capturing what are called calibration frames (bias, darks, flats), additional shots taken to improve astrophotography images by accounting for things like sensor noise and dust. It is also the first time I have processed using calibration frames; I took 100 images (20 seconds each) and post-processed them and the calibration frames using a software tool called Siril and then finished in Photoshop. 

Capturing a comet is often tricky since it is moving at a different rate than the stars. Using a star tracker (vs. a telescope mount), my only choice was to track the stars and hope to be able to post-process the comet and stars separately then combine them afterwards. I did that but it took a long time and many tries just to get the results above. I wish I had more data but longer exposures weren't possible since the histogram showed that any longer than 20 seconds at ISO 3200 would have resulted in clipping (i.e., the blue was almost lost to the right side at 30 seconds). On top of that, the comet would have blurred if I used too long an exposure given how fast it was moving.

One of the other tools I learned how to use is Astrometry.net which can do something called plate solving, taking an image and finding where in the sky it is a view of. Here is the results of plate solving using one of the images used to create the shot above. I find this raw, astrometrically-labeled view an interesting alternative version of my night's labors since the comet (though not green) stands out a bit more.

The three dots and labels represent stars in the constellation
Camelopardalis identified using plate solving on astrometry.net

Anyway, the next time I am shooting a dim fuzzy (hopefully without the Moon up and away from city light pollution), I'll have had some practice and expect to be able to produce much better results. 

Stay tuned...

Click on an image to see full-screen. 

Perseid Meteor Shower Watching Success but Photography Fail

For this year's Perseid shower, other things got in the way of getting out to a dark sight to view it or to even be up watching pre-dawn on the 12th but that evening we sat out in the back yard with two of our grandkids, Jack and Harper, to try and catch at least a few bright ones. 

The good news is that we did each see at least one. The bad news is that was before I set up my camera to capture this time lapse video. The other challenge besides the light-polluted skies of Dallas are how many other lights there are in our back yard. The ever-changing color of the neon clock in the kitchen, visible through the back door or even the time one of us went to the bathroom (the window next to the back door) were the least of the problems. I'd turned out our patio LED light strings and the solar path lights but neighbors to the west and southwest have a lot of yard lights on all night. This video represents from about 11pm through about 3am and it was never truly dark out there. 

Normally, I would have had the camera at about ISO 4000, f/2.4 and shooting 20 second shots. The best I could do without blowing things out was ISO 400, f/2.8 and 8 second shots. That was still enough to catch stars rotating around Polaris and should have caught any bright bolides. Sadly, the only lights in the sky besides stars were aircraft going to and from Love Field and DFW.

I had been tempted to go out east of Dallas by myself about 5am to see if I could shoot the Perseids from a darker sight. Glad I didn't bother as the clouds rolling in would have spoiled the view under even the darkest skies. 

View full screen to catch the motion of the stars.

Light Pollution Map using Google Earth Plug-in

For anyone who's downloaded (or interested in downloading) the Google Earth plug-in for Google Maps, here's a glimpse of its power and a handy place to refer back to when checking how much light pollution there is in a given area. This gadget doesn't include a search capability, but it is pretty easy to interactively search for a spot on the map. Also, the map below is just for North America but you can Google "google earth light pollution overlay" to find similar maps for other areas of the Earth.

Note: If you don't already have the Google Earth plug-in installed, depending on your browser the gadget below may prompt you to install the plug-in or may just show a Google map of the United States. If the latter is the case, click on the ZOOM link below which will display the map in a full browser window; you will then be prompted to install the plug-in.

ZOOM TO FULL WINDOW

It's That Time Again... GLOBE At Night

When is the last time you looked up and saw the Milky Way at night? Or saw a meteor shower? If you live in an urban or suburban area, it may have been a long, long time. It has been many years for me but I can recall enjoying the splendor of these sights from my backyard when I was younger. Having spent a lot of time looking up at the night sky over the years since then, I've watched it change. Not noticeably from night to night or even year to year, but every few years it's obvious there's less to see.

At work, a common phrase is "what get's measured get's tended to". I think that with light pollution it's the same. It is one thing for someone to look up and realize they can't see what they could when they were a kid but anecdotal evidence isn't science. To make a case for change, to turn the tide and restore the beauty - and benefits - of clear, dark night skies, we need to measure the rate and circumstances of change. Only then can we forecast how much worse it may get in the future and justify steps to restore what we've lost. Or at least avoid losing more.

That's the point of a project called GLOBE At Night. I wrote about it last year so I won't repeat the details (you can find them here), just the invitation... please join me in making a small contribution to improving the world to which our future generations will be born. And do a little science. And learn a little. And have fun doing it.

Here's to darker skies,
Nate

PS. For more information on light pollution and ways to fight it, check out the International Dark-Sky Association.

Help Measure Light Pollution Around the Globe

The GLOBE at Night project is an opportunity for students, parents, teachers, amateur astronomers or anyone else interested to participate in real science. Held this year between March 16th and 28th, the project will use observations made by people around the globe to capture information on current light pollution levels. In addition to telling us what things are like now, the observations will also be compared to information collected in previous years so this is a great way to do your part to help identify how much light pollution has changed in areas all over the world.

Participating is as simple as:

• Find your location in longitude and latitude


• Locate the constellation Orion in the evening sky about an hour after sunset


• Match what you see to examples provided on the GLOBE at Night web site


• Report your observation

It's that easy. The project web site provides everything you need including tools to find your longitude/latitude, magnitude charts and even links to see what others around the world have reported. Keep in mind that the more observations reported, the more accurate and complete the project results will be so you can help by checking the sky over multiple nights and even from other places near where you live.

This is another great way to help celebrate the International Year of Astronomy. Get outside tonight and do your part... I'll be out there, too!

Update: Having gone out and done my observation for tonight (plan on doing other locations over other nights of the project), I have a suggestion: skip the step to look up your longitude and latitude. When you go to the link to report your observation, there is an option there to select long/lat by specifying an address. It is just as simple to wait till you report your observation as to look it up in advance and remember it to enter later on.

City Lights

City Lights
By neatonjr


Twinkle ...
Copyright Jamal Alayoubi, 2008

Although I enjoy spending time in the countryside, I'm a city boy at heart. I enjoy too many of the amenities conveniently available only in the city... a wide variety of restaurants, the symphony, major museums, etc. That said, there is one thing I don't like about living in town - I've watched the night sky from my backyard disappear over the last 20 odd years.

Our youngest sons are just about to turn 24. When they were small, we could sit in the backyard and clearly see the Milky Way rising up from the southern horizon and crossing overhead. I can't see it at all now and haven't been able to for probably 10 years or more.


While I can still enjoy observing from my own yard, the best targets are obviously the moon and planets... dim fuzzies are just too dim. As an example of the night-time illumination in my area, see the photo City Lights to the right. No, that wasn't taken during daylight. Look closely and you'll notice some faint star trails and even Polaris just to left of center. That shot was taken around midnight under clear skies; the exposure was 30 minutes at F/11 and ISO 200. Compare it to Twinkle ..., taken by Jamal Alayoubi in the Swiss countryside northeast of Lake Geneva. His exposure was almost 4 times as long at F/5 and ISO 500.


One of the most dramatic examples of just how bad light pollution has gotten in certain areas is the light pollution maps at The Night Sky in the World. To see how severe the problem has gotten in my hometown, check out this light pollution map for Dallas, Texas provided by cleardarksky.com. Mesquite is about half-way between the center of the image and the right side. Ouch!



While it is a shame to lose the connection our ancestors had with the sky, there are serious reasons for concern over light pollution including wasted energy, upsetting the natural rhythms of nocturnal animals and birds and possibly even impacts to our own health. The good news is that the issue seems to be getting more attention in the press. National Geographic published a great article on the subject this past November. And while reviewing the International Dark-Sky Association web site for other media coverage, I discovered that Think, one of my favorite programs on our local PBS radio station, KERA, recently highlighted the subject of light pollution. Hopefully, the increased attention - possibly aided by the International Year of Astronomy 2009 events - will begin to make a difference. I'd love for my grandkids to some day see the Milky Way from my backyard.