As I'm filming this right now the total solar eclipse is only 4 days in the future.
I'm thinking of putting something together to make a camera track the Sun so I can film it
And I already have this rotating platform that I built years ago so I was thinking I
just need something to elevate the camera and that can optically track the Sun
But how do I make sure my algorithm can actually track through the period of totality? I have
no way of testing that ahead of time So much simpler is going to be to just tilt
this platform so it lines up with the Earth's axis and make it turn once every 24 hours,
and I don't need to track the Sun. So I got about a 15 to1 reduction on
here and I need to do one step of the motor every 28 seconds to make a once every 24-hour turn
And this is doing one step every second and you can really see that move when
it steps so that could be a little jerky especially if I put a long arm on there
to see what it looks like at a distance you can see that's really jump around a lot
But my stepper driver supports micro stepping so I can divide physical steps of the motor into up to
32 smaller steps so I'm just going to reconfigure that via dip switches first three off
And now the steps are too small for me to see here and if we look at the end of the stick here
that still shakes quite a bit from the stepping but of course that has some resonance to it
But if I just attach a stick straight to the motor pulley and look at it here you can see that motion
is still quite jerky so it'd be better to have more reduction but even better would be just
some kind of a DC motor running slowly maybe with a belt drive, but there's not much time left.
But then I realized I was actually planning on taking a time lapse with one picture every
5 seconds or so at that point I can just make the adjustment let it settle and then take a
picture and the jerkiness won't matter So I wrote a little bit of code and right
now with the time interval set to three seconds it actually moves really nicely not too much bumping
around but that's because it's at the step rate to not mess with the harmonics of this Chopstick
here of course the camera will be different I've been trying to check the consistency of
my intervals if I go for 5 seconds and I've marked where the end of this pointer goes
and the interval is not exactly consistent. It doesn't help that sometimes I'm doing five steps
and sometimes six but the bigger inaccuracy is that micro stepping just isn't that accurate
So now with a camera on here that's fairly telephoto hooked up to the Raspberry Pi and
stepping and taking photos I should ideally get a smooth panning motion as it pans across
the view here but looking at the video it's a little bit jerky in its motion,
and the Sun is only going to be about this big with that level of Zoom
So I did it again consistently stepping three micro steps and I still get that jerkiness
so basically the micro stepping just isn't consistent enough
But in my various collections I found these two pulleys and an extra belt
so I could try reducing that a little bit. I just finished cobbling together my reduction
here and it looks quite nice but then I turn this and notice how this keeps jumping and
that's because this timing belt is not quite the same pitch as the wheel on here.. oops!
So now I just flipped that belt teeth facing outwards and now it runs perfectly smooth
and I think that'll be fine because I don't really need absolute position.
With that extra reduction I get over quarter million micro-steps per revolution,
and running that at 15 times actual speed the end of that
stick actually moves pretty smoothly now And for 5-second intervals with a sun I need
to do about 13 or 14 steps between pictures and just doing a panning experiment that seems to pan
fairly smooth now and taken with a Raspberry Pi HQ camera module attached to a 50 mm lens which
is pretty long for such a small sensor But this camera lens is 135 mm focal length
I just need a way of mounting that to my camera module.
I can just barely screw in a screw Mount extension tube straight into the wooden hole,
and on this knurled side the mut part of the S Mount fits nicely in there as a friction fit so
with the extension tube in here and the S mount in here I think I have my lens adapter thingy
Well I made this thing to go with a 20 mm extension tube but that turns out to
be too long a 10 mm one will be too short but I have lots of focus adjustment here
to make up for it but as it is right now I can't focus to Infinity which is no good
I've been photographing this camera battery and the text spacing on here is 1/5 mm per
line and photographing that at 3 m away with the 135 mm lens I get uh this sharp
and the sun would be roughly about this big on here so a reasonable amount of detail
I also photographed it with that 50 mm lens and the image is much sharper but of course
it's a fair bit smaller and if I zoom in on that to be the same size we just don't have
enough pixel density in the sensor to get that writing, whereas on here we can get it
although I can tell here just from how this image looks that we're very much limited by the lens
And that's using this lens at f/8 which is probably about as sharp as it'll get
whereas this one I was using an f/4 which just tells me this is an incredible lens
that's made for these digital sensors to have a much higher spatial resolution than the film
ever had. These 35 mm lenses with a teeny little sensor on the end they're just not that sharp
Oh and on top of that this is actually a zoom lens whereas this is a fixed primary.
But then I realized I also have 180 mm screw mount lens so I put that on there photograph that again
and now looking at that uh this is with a 180 mm lens very legible whereas with a 135 mm not so
satisfactory and 50 mm not legible at all. I've been experimenting with variant the
aperture on the lens to see what gives me the sharpest image. The aperture is usually focal
length over whatever so f/22 is focal length over 22 and f/4 is focal length over four
And the smaller I make the aperture say f/22 I get way more depth of field which means it's much
easier to get focus and lens abberations are less of an issue but I run into diffraction limits,
whereas if I open up the lens further I get more light but now the lens limitations also
become a factor and depth of field so if my focus is a little bit off that's bad.
So here's some test images at f/4 it's legible but uh not great then if I switch to f/5.6
it's becoming much more clear at f/8 slight Improvement f/11 also quite good but then once
we get to f/16 it's starting to get blurry again and f/22 it's really quite blurry and
that's diffraction limits at the small apertures and lens aberations at the larger apertures
So ideally I'll use an aperture in the range of f/11 to f/5.6 of course I have to make
that work with the exposure of the sun so depending on what filter works best I may
have to pick possibly outside that range but I'm starting to question whether I'll
have this thing ready by the time of the eclipse especially with the first sunny
day being the day of the eclipse it's going to be cloudy up to that day
And a quick panning test with that 180 mm lens looking not too bad this would be about 15 minutes
of real time so if I wasn't following the sun with my mechanism I would lose it pretty quickly.
I made a mount for this lens here and I'm actually grabbing the lens by this front thing here but I
can still focus it, very important. And this is actually inclined by about 8° because we are on
the summer side of the Equinox which is to say the sun if we're at a North Pole would always be about
8° above the Horizon which means this needs to be inclined 8° and then this axis needs to be lined
up with the Earth's axis which is why I added this foot here and that should put at the right incline
to correspond with where we are Man I just hope this thing is
going to work the day of the eclipse I am testing this right now this is looking
at one of these bulbs 10 m away so it gives you an idea how much magnification I've got and I've also
added an Aiming device because it's very difficult to even get the light in view so as long as the
sun shining through this hole here ends up going through this hole here I know it'll be in frame
And I also made this bracket to hold my auto darkening welding filter in front
of the lens. It uh can be quite unclear in various positions although at one position
it's not too bad but not as clear as without Now if I could move that filter from front here
to near the sensor then it deflection wouldn't make the image so fuzzy but then the light
wouldn't hit the solar cell on here and it wouldn't darken anymore so that's no good
And I've been playing around with other sort of darkening filters like these sunglasses and
they make things really fuzzy optically not very good also these eclipse glasses but they are so
incredibly dark that I just don't have anything bright enough to even see through those things
Looking straight at the sun with them you can barely see the Sun they're so dim but I've also
tried these little uh spy glasses that the kids have that have basically a mirror on the sides to
see behind you but that mirror is not fully opaque I can see light through there and that turns out
to be an optically not a badh light reducer. So if I take a lens out of one of those and somehow put
it back here that might work that's tough stuff
I cut this slot wider than I needed cause I wasn't sure if one lens would be enough but sticking that
half mirror in here and locking the rest of it with this piece of wood I can now get my light 10
m away this clear which I'm pretty happy with and I also made an aperture to go on the front
of the lens instead of using the one back here and that way most of the heat from the sun will
not get inside lens and with the settings I'm using right now I can still reduce my
sensitivity by a factor of 100, and I figure the sun is probably about 100 times brighter
than that led light I've got up there Of course to get the best shot of the eclipse
the logical thing to do would be to spend a few thousand on gear but my goal is to see what can
I do it with the stuff I have, and so far my total spend is $2 for these things here
Today's the day of the eclipse it's also the first sunny day in a long time so I can finally
test how dark my filters are and testing with one of those kid spy glass mirror type filters
that was way too bright so I used a filter for one of these eclipse glasses out front and that
worked awfully dim though but to get better image quality I thought i' tried to put it at
the focal plane and that worked for a little bit then suddenly my image got really really
bright cuz I was focusing the sun onto this thing here and it burnt a hole through it
And afterwards I could see a speck on my sensor I thought oh oh no I burnt a
hole in the sensor but it was just a speck of dust that I hadn't paid attention to before
But these things aside from being awfully dim they also make it rather orangey so I went back
to these kid spy glass filters and then I put the other lens in the back mirror facing forward and
between those two I get a reasonable exposure And looking at some of my time lapses with just
a plain Sun it seems to be jumping around an awful lot and I thought maybe there's something
unsteady about my device but no so this is a live View and that sun is just jumping around
a little bit if I use my Eclipse projector so this is a mirror here's a 1/8th diopter lens
and that projects onto the wall here and if I look at that this is actually the clearest
image I can get of the Sun but you can see how it just keeps jumping around an awful lot and that's
because it's a sunny and windy day so there's probably quite a lot of turbulence for that
plane up there and that's causing the atmosphere to refract the light differently over time causing
the sun to appear to jump around Of course any astronomy buff could
have probably told me that just watch that jump around and
notice the sun approaching my fingers here the sun moves one whole sun diameter every 2 minutes and
just testing that it isn't my camera that's doing all the jumping around I've got aimed at the door
knob of the shed down here and here's what we're seeing and it is not jumping around a whole lot
As for this auto darkening welding filter I got terrible picture quality out of that one,
possibly the auto darken makes it worse. So I'm not using that one it also
made everything green As for my geometry that was
off a little bit too I researched it some more and my estimate was I needed 8° inclination on
here it's actually 7 and also I shimmed it back a little bit and I'm not sure if
my platform is perfectly level so I shimmed that too to get that to aim at the Sun and.
And I looked up on Google Maps what the angle of our house is and set that to that
just eyeballing on the screen I'm using that to make sure I have this axis that the whole
thing pivots on lined up with a North Pole And here's the time lapse that I captured you
can see a little bit of shaking around and then sometimes big jerky movements as I
reposition the camera to make up for a drift because my axes weren't lined up properly.
The sharpness isn't optimal partially cuz I was using a relatively small aperture
but also I think because my filters were less than perfect optically now in the leadup it's
a bit more shaky because I was showing this to a friend and I was actually leaning against the
porch railing which caused a lot of vibration And I was shooting frames at a 10-second interval
because the whole thing is relatively slow progress this is entering totality at 10 seconds
per frame the final transition was a matter of seconds so I wish I'd used a shorter interval.
And this is now in totality and actually using Auto exposure because every 10 seconds I took
a manual exposure and an auto exposure and you can see the little red geyser sticking out of
the Sun and as the moon moves in front of it you can actually tell that the sun is in a different
position based on how the geysers stick out and Now halfway through totality I pulled the filters
which resulted in a lot more light but unfortunately it also threw the
focus off and here comes the sun again and I quickly put the filters back in the lens for
fear of burning a hole in my sensor Now it's a little bit less sharp after
totality because pulling those filters out and putting them back in somehow threw off the focus,
and I'm speeding this up a bit more because after totality is just not nearly as exciting.
And a few photos uh this is at nearly 95% occlusion and it doesn't really look that
different because our eyes and the camera do such a good job of adjusting for light levels though
it does seem kind of odd that my flashlight lights up the ground as much as it does
And this photo was taken the very moment we entered totality and this is during totality
it wasn't actually all that dark because the Horizon was still bright but it looks dark
here cuz this one's with a flashlight same photo without a flashlight the camera does a
good job of compensating for light levels. An interesting takeaway from this is how well
our eyes and our cameras are able to adjust for drastically different levels of light.
And this time lapse here is of our driveway with the camera fixed at daylight exposure
time stamp on the bottom left. And you can see how really dark it gets and you can see
the driveway light turning on top right but it's barely visible with the daylight exposure
because it's so much dimmer than daylight But the coolest part to me is this photo
which shows a plasma eruption sticking out from behind the moon it's underexposed and
fuzzy but I don't see that sort of photo in social media very much