Is photometry with a Seestar possible at all?

Tags

, , ,

This last experiment doesn’t look very promising. This a classic graph of random noise.

Unfortunately, it’s what I got during two hours of two-second exposures of known variable star RR Lyrae, two nights ago. These were the shortest times ever available for the ordinary user; the engineers at ZWO apparently listened to complaints that 10 seconds was the very shortest exposure time available

I had previously found that even at 10 seconds, and de-focusing, and applying the light pollution filter, the pixels capturing light from RRLyrae and many other well-known variable stars were generally over-filled (saturated), which meant that I couldn’t do any useful measurements. I had remembered to bring

However, after asking ASTAP and AIJ to process a sample of 859 short exposures, it looks to me that, unfortunately, the Seestar chip is just too noisy to be very useful at all for photometry.

Phooey.

Some Pretty Seestar S50 Photos

Tags

, , , , , , , , , , , , , , , , , , , , , , , , ,

I can’t take really take very much credit for any of these images, because all I did was this:

  1. Make sure the device was fully charged the day before.
  2. Choose the ‘Auto Plan’ option instead of the Manual option in the Plan section of the Seestar app on my tablet; accept and save the Plan that it creates for me.
  3. Most important: Drive to a safe location much farther from city lights — Hopewell Observatory, which I belong to.
  4. Once it’s getting dark, level the tripod carefully.
  5. Screw the Seestar onto the tripod.
  6. Push the button to turn it on.
  7. Be patient while my tablet and Seestar set up their communications channel.
  8. On my tablet, tell the Seestar to carry out the Plan that it created in step 2.
  9. Make sure it has actually started.
  10. Every so often, check the current image and make sure both devices have enough ‘juice’.
  11. In the morning, put everything away.
  12. Later on, examine the finished and stacked images, which I will show you in a moment. Decide whether or not to delete all the sub-exposures.

Here are the images of the distant nebulae it was able to get and process, all by itself, starting at about 10 pm:

SH2-142, Wizard Nebula, 10 to 11 pm
SH2-140, part of the Cepheus Bubble, 11 pm to 1 am
IC 5068, Forsaken Nebula,1 to 2 am
IC 1318B, Gamma Cygni Nebula, 2 to 3 am
M 45, Pleiades Cluster, 3 to 4 am
IC 1995, a very faint nebula in Taurus, connected with Pleiades nebula, 4 to 5 am
Caldwell 28 – an open cluster of stars in Andromeda (EDIT: I mis-typed Caldwell 27 originally, which is the Crescent Nebula)

A very ambitious imaging agenda, and very respectable accomplishment for a camera, mount, and processing system all put together into a package the size of a child’s backpack! Note: I didn’t have to take any darks or flats, nor stack and process any of the thousands of 10-second exposures it took that night, mostly while I was safely asleep on my cot in the Operations building.

Even though it doesn’t seem to work very well for detecting exoplanets (at least not for me) the ZWO engineers who invented this thing, making imaging of deep-sky nebulae a piece of cake, deserve a lot of credit!

More August 2026 Astro Events!

Tags

, , , , , , , , , , ,

1.This evening (8-19), NCA trustee Zack Gleiberman is giving a talk at Rhizome DC on astronomy in DC. Admission is free. The talk will start at 7 pm. 

2. This Saturday (8-22), NCA members will help the DC Dark Sky International staff a table at the National Book Festival, which will be held from 9 am to 8 pm at the Walter Washington Convention Center.

3. This Sunday (8-23) National Capital Astronomers will have its required annual board meeting to plan events, examine the budget, and so on. All officers and committee heads are expected, and any member of NCA is welcome, but there will be no public lecture or slide show. The physical location is my house, 1316 Randolph St NE, WDC 20017, starting at 3 pm, with light refreshments, or you can attend remotely at https://umd.zoom.us/j/95619565617?pwd=uqwxzZ39zgVfgOypmcp8cy6xFaCcRb.1

4. Next Wednesday (8-26), some NCA members will bring telescopes to another overnight event at the DC Department of Parks and Recreation program at Camp Riverview, MD. The camp (free; enrollment by lottery) is very close to Point Lookout, MD., which is a pretty long drive from DC. This event will be for senior citizens.

5. On the night of Thursday/Friday, August 26/27, the Earth’s shadow will cover almost all (96%) of the Moon. For us in the DMV region, the partial phase will begin at 10:33 pm, maximum eclipse will happen at 12:12 am (ie after midnight), and the partial phase will end at 1:51 am. No particular optics are required, and there is no chance of actual danger from viewing the event with either a camera, a telescope, binoculars, or your unaided vision.

6. The next day, August 27, the Astronomy@250 conference of the Astronomical Society of the Pacific (now known as the Astro Society) begins with a public panel on Dr. Nancy Grace Roman, who as you probably know was the first chief of science at NASA, shepherded the Hubble Space Telescope into eing, and was a member and officer of NCA for many years. The link to join this session is www.youtube.com/@astrosocietydotorg

7. Saturday, August 29 is the deadline for any articles or photos you would like to include in the September 2026 Star Dust newsletter.

8. On Sunday, August 30, around 8 AM, the Nancy Grace Roman Space Telescope is scheduled to lift off from Cape Canaveral on a Falcon Heavy rocket. It is expected to revolutionize astrophysics with its unprecedented wide-field infrared observations. Does anybody want to hold a watch party for the event?

August 20026: Eclipses, Meteor Shower, ATMing, and NGRST Space Telescope Liftoff!

Tags

, , , , , , , , ,

August 2026 is a very busy astronomical month!

1. Venus is VERY bright in the western sky at sunset right now, and it’s only half lit up! Any telescope or binocular will show this.

2. On August 12 we in the northeastern part of North America will get to witness a partial eclipse of the sun with safe solar telescopes or straw hats or colanders. The maximum bite will taken from sun around 2 pm EDT. Some parts of Europe and Africa will get a total eclipse, but for Washington DC only about 4% of the sun will be covered, so it won’t be noticeable without help. DO NOT LOOK DIRECTLY AT THE SUN!!!

3. Later on that very same night, especially after midnight, will be the annual Perseid meteor shower! The moon will not interfere at all! (see #2) Best to get to a big open field away from city lights. Wear insect repellent, bring something comfortable to lie down on, turn your phone off completely, and invite a few friends. Bring snacks and drinks, if you like, and pray for clear skies. Leave any telescope or other optics at home unless you already know how to take wide-field time-lapse photos. Make sure you cover or turn off your camera’s display or your eyes won’t be able to adjust to the night sky. I bet that a lot of people will end up at Big Meadows in Shenandoah National Park if it’s clear.

4. On the night August 27, everybody in the Americas will get to see a nearly-full (96%) lunar eclipse! You can view this event by going outside and looking up, from anywhere. A time-lapse photo will work well here as well.

5. At about 7:45 AM, EDT on August 30, the Nancy Grace Roman Space Telescope is scheduled to take off from Cape Canaveral. Ahead of schedule and under budget! This telescope will be a really big deal. My best wishes (which are worth exactly nothing) for a successful operation!

6. The Northern Virginia Astronomy Club (NOVAC) is having their monthly meeting tomorrow afternoon (8/9/26) regarding gamma- and x-ray astronomy, which I was lucky enough to work on a bit as a summer teacher intern 30 years ago at the Naval Research Lab. Go to NOVAC.com to find details for logging on or attending in person.

7. NOVAC is also organizing the Almost Heaven Star Party at the Spruce Knob Mountain Institute next weekend. That’s a great gathering at a very dark site with amazing skies, high-quality original talks and great West Virginia nature walks and so on. Unfortunately, Spruce Knob often suffers from amazing amounts of dew even on clear nights. It’s probably sold out. You can try again next year.

8. Thursday-Sunday, August 13-16, will be the annual Stellafane telescope making convention, held near Springfield, Vermont. It’s been going on for over a century. If you go, you can expect quite a crowd. You can hear lots of fascinating talks about telescope-making during the day, and look through a variety of telescopes at night. This location is where Russell Porter in 1920 recruited a dozen or so factory workers in the town and showed them how to make their own, excellent telescopes all by hand.

Green LED reflects as Red light???

Tags

, , , ,

Very weird: on an old Coulter mirror that we tested tonight, a green LED reflected back at us as **red** light instead of the normal green.

We don’t understand! Green LEDs have a wavelength of roughly 525 nanometers, give or take 30 nm. Red LEDs are about 100 nm longer. How can something that otherwise looks like a normal aluminum coating shift green light all the way to red light?

Inquiring minds would like suggestions.

The first two rows of green images are from a different old Coulter mirror that we also tested, that very same evening, with the same focal ratio, and the same apparatus. The last row of red images that we took of the weird Coulter-ish mirror that I wonder about.

UPDATE: July 18, 2026

There may be a solution to this mystery. Preston Engebretson wrote me on Facebook:

“The coating responsible is likely a standard Aluminum coating with a Silicon Monoxide (SiO) or Silicon Dioxide (SiO₂) protective overcoat that has degraded or contains specific impurities, causing it to exhibit fluorescence (photoluminescence). The Phenomenon: When a Green LED (wavelength ~525 nm) is shone onto the mirror (e.g., during a Foucault or Ronchi test), the reflection appears Red instead of green. The Coating: Coulter mirrors typically used Aluminum with a Silicon Monoxide (SiO) overcoat. Silicon Monoxide (or silicon-rich silicon oxide, SiO_{x} is known to exhibit red photoluminescence under certain conditions, particularly if silicon nanocrystals form within the oxide matrix due to aging, annealing, or specific deposition defects.”

A quick search with Bing and Copilot led me to a paper describing how engineers and scientists have recently been able to harness this photoluminescence to produce reflected light in wavelengths ranging all the way from ultraviolet through red! I never knew!

My guess is that this mirror at some point got very, very hot, and the silicon monoxide overcoat changed in part into a mixture of pure silicon crystals and silicon dioxide, causing the red photoluminescence that we saw. A quote from that paper:

“It has been almost 30 years since the discovery of silicon nanocrystals (SiNCs) (Canham, 1990), which carry unique properties distinct from bulk silicon. Since then, SiNCs have gained enormous attention around the world and harvested countless achievements in a myriad of hot fields (Kubby et al., 2006; Liang and Bowers, 2010; Mastronardi et al., 2012a; Bonafos et al., 2012; McVey and Tilley, 2014; Zhai et al., 2014; Sun et al., 2016c; Dasog et al., 2016; Meinardi et al., 2017; Ni et al., 2019). Many of the applications are based on SiNCs’ photoluminescent properties. Consequently, significant progress has been achieved in the performance of their photoluminescence (PL) with the concerted efforts by the numerous nanochemists and physicists: the quantum yield (QY) has risen from a few percentages to more than 70% (Sefannaser et al., 2021), and the photoluminescence window has been expanded to a full range from ultraviolet to infrared (Hessel et al., 2012; Ghosh and Shirahata, 2014).”

Another Attempt at Exoplanet Transit Detection

Tags

, , , , , , ,

This time I attempted to detect a different transit of another star using two different setups on the grounds of Hopewell Observatory in northern Virginia.

  1. A Canon 6D DSLR mounted on a big, heavy 14-inch Schmidt-Cassegrain telescope on a very sturdy AP1600GTO equatorial mount
  2. An alt-az Seestar S50 all-in-one astro camera

Can you spot where the exoplanet TOI-1259-b dimmed the light from its host star?

(Hint: this is a trick question!)

Here are the graphs I made from the data I collected:

Was it at A? Or did it happen at B? (Trick question!)

And this graph is what I got from my SeestarS50:

Psst:

Point A in the first graph was when I reduced the exposure time on the camera from 2 minutes to 30 seconds. That caused all of the fluxes to decrease, because cutting the time by 4 reduces the number of photons captured. Arrow B points to where the transit was supposed to happen, with a 2.7% decrease in brightness.

Do you see it?

Me neither.

In the second graph, done by the Seestar at the same location on the same night, smoothed as much as I can by averaging successive images, I again don’t see much evidence of a 2.7% dip in total flux.

Conclusion: chasing exoplanet transits looks like it could be easy, but it’s not.

===============

This graph here is no better.

And here is where I extracted just the two green channels:

No, I am not at all convinced that my measurements captured anything.

Another Exoplanet Transit Attempt: COROT-2

Tags

, , , , , , , ,

Do you see a transit in this data? I would say, “Maybe”.

Since the Seestar has quite a bit of error, caused in part by its Bayer array of green, red, and blue pixels, I grouped my original measurements (processed in AstroImageJ) in groups of 5, using Excel to do so.

Science with Seestar S50? Not so far!

Tags

, , , , ,

Latest results on a known variable star, W Ursae Majoris with my Seestar S50 during a very nice night: complete garbage. The graph below shows the flux of my star, WUMa, compared to the median of 9 comparison stars in the same frame, chosen by AstroImageJ.

As you can see, there is no real pattern.

If this data were real, then this star would be changing its brightness by a factor of three or for in less than a minute, with no discernable pattern. While a candle flame will flicker like that, it is simply not possible for something as large as a star to vary as quickly as that. In fact, this star is actually a contact-binary (double star) with a rotational period of about 8 hours. Even with the noise, I see no sign of a trend over these two hours.

The weather was very good, there was very little light pollution, and this star was quite high up in the sky the entire time, and none of the stars were saturated. But this data is just so, so noisy.

(I used ASTAP and AstroImageJ to do the plate solving and comparison of brightnesses. AIJ is an absolutely amazing program that automates so much of the tedium of this sort of process. For this graph, I had AIJ extract the green channel from the GRGB Bayer pattern, hoping that eliminating the blue channel would reduce atmospheric problems, but no luck so far. Combining all channels was no better.)

Other people claim success, but so far I’m zero for 12 in detecting exoplanet transits, and only 1 out of a dozen or so variable star measurements. Not sure what I am doing wrong or how I can reduce the errors. Yes, it’s true that this is only 2 hours out of an 8-hour period, but this data does not make any sense!

Zero for Twelve on Exoplanet Transit Detection

Tags

, , , , , , , , , , ,

As you probably have guessed, detecting exoplanets is not easy.

So far I am about zero detections for 12 attempts.

My equipment has been a Seestar S50, and either a ZWO CMOS camera on an Explore Scientific 5″ f/7 triplet refractor, and a Canon 6D DSLR affixed to a venerable C-14 mounted on an Astrophysics 1600 GTO mount.

The Seestar is able to detect brightness changes in other variable stars like RRLyrae, but so far the small changes in flux from exoplanet transits gets drowned in the noise. The DSLR on the C-14 has much less noise, but I still haven’t seen any clear and obvious signs of a transit.

Here are graphs from my latest attempt at detecting WASP-135-b. In the first one, I plotted the fluxes of that star against four of the comparison stars. I added a fixed number to the fluxes of the other stars so you could see trends more clearly. Shortly after 3:30 AM, measurements became very strange for every single star. I was asleep at that time. I’m guessing that there were clouds. Do you see any noticeable dip in brightness of the target star at 3:07? I sure don’t.

In the second graph, I asked Excel to take the average of the fluxes of several of the comparison stars, and then divide the flux from WASP-135 by that average. Again, I see no dip at the appropriate time (Julian Day).

I used NINA to program my cameras and the Hopewell Observatory’s AP mount to take these images. I used ASTAP and AstroimageJ to load all of the images from my various cameras, figure out exactly where the cameras were pointing (aka plate solving), find a bunch of comparison stars, and then measure the fluxes of each of those stars, on each and every single 30-second frame. That set of software — all free!!!– has made all of this work much easier. Thank you to all the incredibly smart and generous people who wrote, and then made freely available, all those complicated computer programs!

I will try TOI-1811 tonight, with some different settings.

Is NASA PUNCHing at solar storms?

Tags

, , , , , , , , , , , , , , , , , , , , , , , ,

Are you worried about solar storms?


We can perhaps defend against them with a high-flying scientific PUNCH!

(Pun intended. Sorry.)


NASA’s PUNCH mission is flying and is beginning to take polarized 3D images of the interaction between the Sun’s Corona and the heliosphere – to help us predict when our closest star is about to ‘go crazy’ and send so much energy our way as to cripple our power grids or our global networks of communications satellites. 


We will hear about the mission during the monthly April National Capital Astronomers meeting this Saturday, 4-11-2026, starting at 7:30 sharp. 


There will be a bit of club business first, then a talk about PUNCH by Dr Michael Kirk, a NASA – Goddard Space Flight Center scientist, followed by telescope observing at and around the University of Maryland’s observatory under what is predicted to be nice clear skies.  


Michael S. F. Kirk – Sciences and Exploration Directorate

If you like, you may bring your own telescope to set up on the pads outside on the observatory grounds, to share views with others. I plan to bring one of the scopes that I made, and I hope we can draft somebody to keep an eye on them during the meeting.


To drive to the meeting in person, aim your GPS at “UMD Observatory” or type in 3255 Metzerott Road, College Park, MD 20740. The inconspicuous entrance sign is on the south side of the road. Public transportation to the location is unfortunately not reliable. 


If you want to join us remotely, here is the link:
UMD-NCA-Zoom-Link
or you can try 

https://umd.zoom.us/j/95619565617pwd=uqwxzZ39zgVfgOypmcp8cy6xFaCcRb.1 (no spaces)

Log in well before 7:30 if possible.

Are you one of the lucky ones who have seen the enormous solar corona during a total eclipse?

Have you seen the Northern or Southern Lights?

These gigantic structures change like our own weather. If you fly near the Arctic or Antarctic circles at night you can see the aurorae just about any time, but the solar corona itself only becomes visible to us on Earth for a few fleeting minutes during a total solar eclipse.


There is a lot that is still unknown about the solar corona — and how it affects the solar winds and the heliopause that protects us from most nasty interstellar radiation. As you probably know, all these connected phenomena influence the Northern lights, can play havoc with radio communications and satellites, and have in the past occasionally knocked out all electricity to large parts of North America and other locations. Larger solar outbursts could conceivably disable every single global communications satellite system, without which modern civilization would largely crash to a halt.

(See List of solar storms – Wikipedia for examples.)


NASA science missions like PUNCH don’t get nearly as much publicity as crewed missions like Artemis. But they also cost a whole lot less, and when they work as planned, they get better data.  


(Compare the photos of the backside of the Moon made just now by the Artemis crew (with their cell phones) with those made by the unsung Lunar Reconnaissance Orbiter, LRO, which has been orbiting the Moon ever since 2009 and taking very high-resolution photos in lots of wavelengths. LRO not only has detected all sorts of chemical variation on the Moon’s surface, including signs of water ice, and has even sent back images with very clear tracks and rocket blast marks left behind by the Apollo astronauts over 50 years ago!)

These two images are of the same location, Vavilov Crater.


 LRO: https://upload.wikimedia.org/wikipedia/commons/thumb/b/b6/Vavilov_crater_LRO_WAC.jpg/960px-Vavilov_crater_LRO_WAC.jpg

Artemis: Finally, Artemis delivers some exceptional, high-quality photos of the Moon – Ars Technica

The photo from the LRO is incomparably more detailed.

Our speaker, Dr. Michael S. Kirk, is a Research Scientist in the Heliophysics Science Division at NASA’s Goddard Space Flight Center. He plans to explain to us the status and goals of NASA’s PUNCH constellation of four small satellites in low Earth orbit.

Using polarimeters, the craft are supposed to be making global, 3D observations of the entire inner heliosphere to learn how the Sun’s corona becomes the solar wind that comes our way.


PUNCH stands for Polarimeter to UNify the Corona and Heliosphere.

NCA is a 501c3 educational and charitable non-profit, and all of our meetings are free and open to the public. Our website is capitalastronomers.org

Guy Brandenburg,

President, National Capital Astronomers