First Tau Her Meteor

Image taken at 05:46:46 UTC on 2022-05-28 with USL012.  Radiant is RA = 202.66425, DEC = +16.13974.

Here's another one from 2022-05-29 06:02:30 UTC:

the trail in the extreme upper left is an aircraft.  The meteor is the one just to the right.  Radiant RA = 203.90906, DEC = +18.88696

So cool...

Twilight Derivatives

Since change is the nature of the universe, I'm always interested in looking at how things change.

Measuring how things change is simply looking at the difference between two adjacent data points, either in time or space.

In the case of looking at twilight, I'm interested in seeing how the brightness changes as a function of time.  If you want to put this in terms of motion, the dimming of the sky after sunset is a lot like a velocity.  I can calculate the 'velocity' of the dimming by calculating the derivative, or difference, between two adjacent points in time.

I also like to make various forms of spectra -- also called 'histograms'.  I can make a spectrum of the velocities, and then break them up in time so I can see how the brightness is changing at different times of night.

Here's a recent sunset (x-axis is hours after sunset, y-axis is ADU):

and here are the differences for the same time period:

Notice that the 'velocity' is negative when the brightness is dropping, just as expected.

Here's the entire night's derivatives (x-axis is hours after sunset, y-axis is in ADU per 10 seconds):

I can then divide this up into 1000 second (16m 40s) chunks, and make a spectrum (histogram) of the derivatives:

times goes left to right, top to bottom.

At this point, I'm just looking at the data in as many ways as I can think of.  I'm not interested (yet) in understanding or explaining what I'm seeing with this data.

Maybe there's nothing interesting at all.

One thing I definitely want to do is a running average to smooth the derivative plot a little to see if there's any underlying structure.  If you look at the darkest part of the plot you get an idea of how dynamic the velocity is.

So yeah the velocity is changing, too.

Twilight

Here's one of the things I'm interested in looking at pretty closely -- twilight.

Civil twilight is 0 - 0.5 hours (which is saturated on my camera)

Nautical twilight is 0.5 - 1 hour

Astronomical twilight is 1 - 1.5 hours

I can now confirm with these plots that yes indeed at 1.5 hours after / before sunset / sunrise, the sky is as dark as it's gonna get:

and here's the entire night, zoomed in to show the fuzz:

according to the MMT almanac, moonrise was 7.41 hours after sunset.  I see a brightening of the sky at about 7.0 hours after sunset.  ?????

Sky Brightness

Been recently measuring the brightness of a very small portion of sky a few square arcmin) using one of the meteor cameras -- in this case, USL00X -- over the course of a night.  I plan on making these measurements (clear or cloudy) for at least the next month.  Here's the messy data sofar:

The x-axis the is the number of hours since sunset.  The y-axis is the brightness in ADU which ranges from 0 to 255.  This also shows the curve for the lunar eclipse that recently happened on 16 May 2022 UTC.  That particular curve is hard to see, so I separate it out:

In any case, this is pretty cool data and I'm hoping that I'll be able to see something in this to grab on to.  What initially captured my interest was looking at sunrise and sunset (from a project I did several years ago measuring the color of the set / rise sky at different locations).

Here's a closer look at the data going up to 2 hours after sunset:

... and the two hours before sunrise:

Looking at stuff like this is part of what basic research is all about -- observation and experimentation.

It's also cool that I can correlate sky brightness with lunar rise and set, but also lunar phase!  That last one was a bit of a pleasant surprise.

As I said, the next step is to look and see if there's anything worth grabbing on to.  I'll know I've got something when I start questioning why it is that way and start hunting for an answer.