How to Handle Ground Seeing in Solar Photography?
Some people believe they should not invest much in solar photography, because they can't exert the performance from their equipment. The images will not be good enough, so why even try?
That's a wrong assumption.
You need to overcome a singular, pivotal obstacle while taking photos of the Sun: the dreaded Ground Seeing.
Once you find a way to minimize this effect to an acceptable level, you're good to go. The rest is down to fiddling with settings. You will perfect your technique with practice, and it's part of the fun.
In this article, I will show you an easy trick to basically eliminate seeing.
Fair warning: you might need to leave your cave to get the best photographs of the Sun.
However, if you are able and willing to do that, sky's the limit. Literally.
And once you look at solar photography as an outdoor adventure (it will take you to nice natural areas for sure), suddenly, you'll be motivated to upgrade your equipment. The flow of getting better and better images while having more and more memorable experiences during your 'expeditions' or field trips will fill you with a sense of adventure, joy, exploration, development and excitement.
The only thing we must know to get there is how to fight the ground seeing effect.
Transparency & Ground Seeing
There are two categories of things that can interfere with our efforts to create the best solar images possible.
Transparency is about how dirty the air is while you are out there hunting for that perfect solar photo.
This isn't always about regular old pollution, which comes from combustion engines of vehicles, factories, residential heating, and other similar sources.
Lately, sand from the Sahara has often visited Europe, throwing a strange brownish hue on the sky and rendering solar images practically useless.
Or there's a massive wildfire in Canada.
Or another Icelandic volcano activates.
The particles from these events and sources block light, making our job harder or impossible.
Luckily, solar images are not as vulnerable to transparency issues as nightsky ones, because of the vastly higher quantities of incoming light. So at least that's one thing we have as an advantage in astrophotography. (And that probably completes the list of our advantages…)
All that being said, when the air is really too dirty, there's little you can do about it.
Seeing comes from the waving motion of the air itself. As we discussed in detail in our post about Lucky Imaging, air behaves somewhat similarly to water - its movement has an effect on the light particles traveling through it.
Unless the flow is completely 'laminal', when the mass of air floats in straight lines, undisturbed, there will be some 'wavy' (turbulent) motion in it.
Many things can make the airflow turbulent, and one of the most important is heat.
One particular attribute of solar photography is that it has to be done during the day…
And during the day, the Sun heats up the land surface.
When you take a look at the Moon at night, you might see a nice, detailed image of it. Come daylight, the same image might be more distorted because of the turbulence.
When the Sun comes up, everything on the Earth's surface starts to warm up.
Roads, buildings, trees, even the grass, everything warms up and subsequently heats up the air around, making it move upwards from the surface. The higher the temperature, the stronger the turbulence.
The air is not heated by the Sun directly, that is important - Air is heated up by objects that are warmed up by the Sun.
This means that this heating effect is stronger closer to the surface.
The worst layer is the lowest 50 metres of the atmosphere.
Atmospheric Seeing Is A Factor - But Not A Key Factor
Many people believe that seeing is somewhat constant - that is true to one element of it and it's due to atmospheric conditions. But the vastly more powerful component of seeing during daytime is the surface turbulance.
Take heed: I managed to create some of the best solar photos ever (and with our new developments, I hope to raise the bar even higher) and I did all of my photos, including award-winning ones, from an area of Europe that has some of the worst atmospheric seeing conditions on average.
One reason many people might think that astronomical seeing conditions are something you need to consider and prepare for is because in nightsky imaging, it definitely is important. During the night, there's not much ground seeing going on. The Sun is not out, so there is no heating, only a cooloff process is underway for a while and then the air almost completely stabilises.
At night, atmospheric conditions greatly affect image quality, especially when looking at smaller and/or distant objects.
The key difference with solar photography is in the scope: we get a lot of incoming light. Our images have almost zero noise and very short exposition times. This makes us handle atmospheric 'waving' a lot better.
It's a factor, but not the most important one. Ground Seeing is what you need to manage to get really high resolutions.
So, to lessen or eliminate the seeing effect, you need to physically get away from this turbulence, somehow.
Dodging Turbulence
1. Climbing Up
One way to do this is to move up. Since the first 50 metres above the surface is the worst, you can try getting above it.
Air is not heated directly at all, so if you can somehow get a lot of air between you and the surface, that should work. I've seen astronomers experiment with boarding a jet to take the best solar photos, but even a 747 in the mildest of conditions can't fly so steadily to not hurt image quality. So even if we ignore how unfeasible (meaning: extremely wasteful) this solution is, it's probably out of the equation for a while anyhow.
In the late XIXth century, astronomers discovered that they could make better observations from the tops of towers. Every little elevation counts.
Towers can work. Getting your full solar photography equipment on top of one is another story, though.
What about mountains?
Mountains should be good in theory, but you need really high ones.
One reason why solar photographers prefer visiting mountains is that they reach above the most turbulent airspace, and they are usually at remote locations where the surface itself is not covered by material that radiates a ton of heat, like urban areas do.
But a forest or grassy area won't make your job significantly easier. It's certainly better than city blocks in summer heat, but they do cause some turbulence, just not that much. In most cases, you won't achieve really satisfying image quality there.
Besides, mountains themselves can cause significant turbulance, because they can be heated up by sunlight. They've got large surfaces and are very dense, so they actually absorb heat pretty well.
What can work on a mountain is if you can set up on a clearing, which is elevated, like a small tower or vantage point. The clean, laminal airflow flying towards you will blow the turbulent air away and you can shoot images through the undisturbed air.
This method is helpful, but it's not necessarily the best. There are other ways to circumvent ground seeing.
2. Having fun in the snow
Are there any things that are very slow to absorb the heat of sunlight?
For sure! Snow and ice is a prime example.
Snow is white, reflecting a lot of sunlight and absorbing very little heat. When it does absorb heat and starts to melt, that process also takes a while—it's not a matter of minutes.
The air above the snow is really not that turbulent.
Of course, it's a fact and a sad reminder of climate change that finding snow is getting harder and harder by the year. The seasons get shorter. You can't find much in easily accessible areas after February.
And you can't do much solar photography in the Northern Hemisphere before March, because the Sun is too low.
We need a more reliable and accessible solution. Luckily, we have one.
SOLEYE 300 in action at Weinebene, Austria
3. Hitting the beach
Tarmac can heat up significantly in five minutes, so much so that bodies of water need literally weeks to get up to similar temperatures.
Once you find a big enough spot of water, there is almost no chance for air turbulence to occur above it, at least for a few hours, in the window of opportunity you aim for.
A tranquil lakeside is the perfect venue for a nice and cozy solar photography session. The fishing hobbyists might wonder at your gear, but in my experience, they provide perfectly peaceful company for our astronomical endeavours.
The optimal solution is to set up on a pier. You need to be somewhat surrounded by water. The shoreline can work too, but it's best to be 'on' the water, even a few metres have a profound effect.
On a nice, calm day, the wind will move just enough to blow the still air mass towards you, which is what you're aiming for.
Depending on the size of the lake, eventually the surrounding land will get warm enough to make the turbulent air above it 'encompass' the airspace above the water as well.
SOLEYE 300 in action at Lake Velence, Hungary
The 'Soleye Method' For Making The Best Solar Photos
I've tested this method enough to say that I identified the following parameters:
> I need 2 km of water in front of me to have access to undisturbed air mass above me until 11 AM in the Summer and 1 PM in the Spring.
> I usually target 2 hours of undisturbed time to spend finding the best opportunities for the photos. (1 is usually enough. I just like to take my sweet time about it.)
> I consider wind direction forecasts and choose which side of the lake I visit accordingly.
When I do everything according to this plan, I always, and I mean always, 10 out of 10 tries, get the maximum resolution.
So, my brothers and sisters living at ocean fronts or seasides: you have the perfect surroundings for solar photography. Sure, you need clear skies as well, but when the weather is calm the wind will carry perfectly still air towards you. Don't go climbing mountains, because seeing-free air is coming right to your doorstep.
The only factor you need to consider is the accessibility of the pier or piece of beach: how can you carry your equipment there, how close can you park your vehicle?
Using Soleye, I can move the gear by hand to a distance of 10-15 metres with ease. Beyond that, I might need a trolley or some extra help because otherwise the setup might take too long.
So, this is my secret sauce.
Apart from building a killer piece of hardware that has objectively higher performance than anything commercially available in this price category, I used this little lakeside trick to make some of the best solar photos ever made (again, not my opinion, a jury or online community decided so). And now you can emulate these methods as well!
Be bold, grab your gear, and make sure to send me your images! Obviously I've got my favourite spots by now, close to where I currently live, and I'm eager to hear about how your location-hunting goes.
I wish you good luck and a particularly low amount of seeing during your shooting sessions.
Active region captured by SOLEYE 300, dualband mirror at Lake Velence, Hungary