Gimbal Head Question

donas · Jan 17, 2019

Hello all, this is my first post on here, as it seems thus far all my questions can be answered via the search box. What I can't find too much to read about is gimbal head usage. I understand the primary use seems to be for fast moving wildlife for easy panning, but since it balances a larger lens so easily, why don't I see it used for moon photography? I recently bought a Wimberly Sidekick and it sure seems like it balances and can lock my Tameron 150-600 in quite well. I'm am quite the beginner, so most of what I take is mediocre at best, I don't want to be behind the curve with bad technique to start with!

Thanks for the input.

Braineack · Jan 17, 2019

the moon doesn't move around -- no need for a gimbal head, any standard tripod head will suffice.

used a $20 tripod for these with the 150-600:
Supermoon Eclipse

donas · Jan 17, 2019

I understand one wouldn't go out and buy a gimbal head for this purpose, but my question was more - why don't people use them for this purpose if they already have one? In playing around with the setup, it seems that my lens is much easier to position exactly how I want using the gimbal head vs ball.

Designer · Jan 17, 2019

donas said:
I understand one wouldn't go out and buy a gimbal head for this purpose, but my question was more - why don't people use them for this purpose if they already have one? In playing around with the setup, it seems that my lens is much easier to position exactly how I want using the gimbal head vs ball.

If you're mounting a really heavy lens, a gimbal head will certainly make things easier, and the swings will be smooth, but consider this: The moon does move, albeit imperceptibly slowly. IMO the ideal "head" would be a motorized equatorial mount (found on telescopes) that would match the speed of the moon (actually the speed of the earth's rotation) exactly.

As to the question of gimbal vs. ball head; they do different things, so use the one that does what you need for the shot. Whichever you use, you can't pan with the movement of the moon anyway, so just lock it down.

TCampbell · Jan 17, 2019

The Moon moves at 14.685 arc-seconds per second. (The Earth spins at 15.04 arc-seconds per second ... but since the moon is orbiting as we spin, it makes the moon appear to move just fractionally slower than the stars.)

The formula for calculating field of view (assuming you have a calculator that works in Degrees) is:

Angular field of view = 2 * arctan(sensor width / ( 2 * focal length))

For an APS-C sensor camera (say 22.5mm in the horizontal direction) and a 600mm lens it's:

2 * arctan( 22.5 / ( 2 * 600))

This works out to a 2.148° field of view (in the horizontal direction)

Multiply that by 3600 to convert degrees into arc-seconds and that works out to 7732.8.

If I pick on my own Canon 60Da camera, the 18MP sensor is 5184 x 3456.

Divide 5184 / 7732.8 = .67 arc-seconds per pixel.

In 1 second, the moon will travel 14.685 arc-seconds. So 14.685 * .67 = 9.84 pixels (per second).

So if you were to take a photo of the moon at ISO 100, f/11, 1/100th sec (the "Looney 11" guideline)... it would move about .0984 pixels (you could just round that to .1 pixels) during that exposure (without a tracking mount).

This is why even though the moon does move ... you don't need to worry about it for purposes of most photography

By the way ... there is a total Lunar eclipse happening this Sunday night (Jan 20). It starts at roughly 9:30pm US Eastern time.

If you are photographing the moon during totality, the Looney 11 rule no longer applies (since the moon is no longer in full sunlight). This gets a bit more complicated. There is SIGNIFICANTLY less light on a fully-eclipsed moon. If you left the ISO and f-stop alone and only changed the shutter speed ... that 1/100th sec exposure when the moon isn't eclipsed could become a 30-minute exposure if the moon has a Danjon value of L=0 (darkest eclipse ... with the moon directly in the center of the shadow when the moon is near perigee.) At this weekend's eclipse... the moon WILL be at Perigee (which means it is closest to Earth). But it doesn't get to the very center of the shadow. Even a moderate totally eclipse could require 30 seconds to expose if you don't open up the aperture.

This would be a problem because if you require a 30 second exposure and the moon moves 9.84 pixels per second, the moon would move 295 pixels during that 30 second exposure if you don't have a tracking mount (that would certainly result in a smeared image.)

If you open up a couple of stops (say your 600mm lens can give you f/5.6) ... now the 30 second shot turns into an 8 second exposure. But then boost the ISO a few stops (say ISO 1600) and now you're down to a 1/2 second exposure (the moon will move about 5 pixels during that time). If your camera could handle ISO 3200 with acceptable results, now you're down to just a couple of pixels.

Keep in mind that 9.84 pixels per second is based on my own Canon 60Da astrophotography camera. I posted the math above so you can drop in your own focal length and your own sensor resolution to see how it applies to your own camera.

Anyway ... the best resource for eclipse photography is Fred Espenak (aka "Mr. Eclipse"):
How to Photograph a Lunar Eclipse

Overread · Jan 17, 2019

It's most likely that Gimbals are expensive tripod heads and that those who have astrophotography as their primary focus are more likely to spend that kind of money on a tracking head and setup for their tripod to track astral movements.

I can assure you I've used my gimbal (well ok its not a real one its a ballhead that does similar) for night time photography with good results. So there's no reason to stop you, its just not the "standard" investment people make.

Much like how many landscape photographers might not use a geared head for landscape work even though its an ideal head for such work; however a macro photographer might well since they've already invested in the head for the benefits for their insect work.

Strodav · Jan 21, 2019

I am into birding and a gimbal head is highly recommended for shooting birds in flight (BIF). Yes, you will see some great shots hand held and even some on a ball head, but your hit rate will go up significantly with a gimbal head. I use a ball head for everything else including landscapes and astrophotography. If you are going to buy a gimbal, you really do get what you pay for. Stay away from the $100 range gimbals as so many report they have had to take them apart, clean out sticky grease, then smooth out and polish rough surfaces with a Dremel tool, chase threads, use graphite lube, ... I use a Sirui PH-20 carbon fiber gimbal, which is OK, but there are better ones out there for about $700.

ac12 · Jan 21, 2019

I use my gimbal head like @Strodav , to shoot rapidly moving sports with a LONG lens. So it has to move easily and freely.
Yes it can be used to point to the sky, but I just use a 3-way pan head for that, because I am not tracking a rapidly moving object.

If it works for you, use it. There is no law that said you have to use X head for Y task.

Most of us don't have a gimbal head, because the good ones are EXPENSIVE, and we rather put the $$$ into camera and lenses.

BTW, I use an inexpensive Chinese gimbal, and as @Strodav said, it needed and needs work to keep smooth. The grease they used was so sticky and stiff that the gimbal behaved like my ball head, LOTS of drag, and not easy and smooth to move.

petrochemist · Jan 22, 2019

donas said:
Hello all, this is my first post on here, as it seems thus far all my questions can be answered via the search box. What I can't find too much to read about is gimbal head usage. I understand the primary use seems to be for fast moving wildlife for easy panning, but since it balances a larger lens so easily, why don't I see it used for moon photography? I recently bought a Wimberly Sidekick and it sure seems like it balances and can lock my Tameron 150-600 in quite well. I'm am quite the beginner, so most of what I take is mediocre at best, I don't want to be behind the curve with bad technique to start with!

Thanks for the input.

Gimbals are great for unpredictable movement. For the stars & moon the motion is VERY predictable, so your better off with something that follows the movement automatically if exposures are going to be long enough to need tracking.

dhavalbbhatt · Jan 24, 2019

One of the challenges that I found with shooting this past weekend's lunar eclipse was when the Moon was at zenith - the Gimbal head mount just wouldn't allow me to get the Moon in the field of view. I am not sure if people find that to be a reason why they won't use Gimbals, but as others have pointed out, for lunar imaging (and even wide field astroimaging), you are better off getting a tracking mount.

Strodav · Jan 24, 2019

dhavalbbhatt said:
One of the challenges that I found with shooting this past weekend's lunar eclipse was when the Moon was at zenith - the Gimbal head mount just wouldn't allow me to get the Moon in the field of view. I am not sure if people find that to be a reason why they won't use Gimbals, but as others have pointed out, for lunar imaging (and even wide field astroimaging), you are better off getting a tracking mount.

Would shortening one or two legs of your tripod get you there?