Taking moon picture

[Sanjaydesai]

I have Canon 6D camera. I am trying to take picture of full moon using EF 70 300 lens. Even at 300mm the picture of moon appreas to be very small. I know I need to use higher focal length but at 300mm the size of moon should be relatively large.

I do not know why this happens. can anyone tell me what is required to be done.

[Mitsubishiman]

Sorry, my bad f4. 5

[TCampbell]

I'm guessing it's one of the 100-400mm f/4.5-5.6L lenses.  At 400mm it's f/5.6 if wide-open.  Using a 2x it's f/11.

I wasn't following the math of how you got to 1280mm.

If you use an angular field of view calculator (there's one on this page:  http://www.tawbaware.com/maxlyons/calc.htm ) you'll find that if using an APS-C size sensor Canon camera (crop factor 1.6x) that a 1500mm lens has a .6° angle of view in the narrow direction.  At 1600mm it's .5 ... but since the moon can technically be just fractgionally larger than a half degree if it's at perigee, the moon would go right to the very edge of the frame with no room left.  So I tend to say 1500mm is the max if you want to fit the whole moon in the frame.

But that's on an APS-C camera...  the 5DSr is full-frame so there is no crop-factor (the crop-factor is 1.0).

[Waddizzle]

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@Sanjaydesai wrote:

I have Canon 6D camera. I am trying to take picture of full moon using EF 70 300 lens. Even at 300mm the picture of moon appreas to be very small. I know I need to use higher focal length but at 300mm the size of moon should be relatively large.

I do not know why this happens. can anyone tell me what is required to be done.

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While you may not have an expensive super telephoto lens, photographing the Moon is just one thing to photograph in the night sky.  You could also capture landscape scenes shot at night showing the stars.  It helps to find what is known as “dark sky” to photograph the stars.  

I almost tossed this photo, until I turned out the lights in the room and looked at it.  The above photo was shot less than 20 miles from Times Square in NYC.  You can barely see any stars in the night sky in midtown Manhattan.

[TCampbell]

There are a couple of moon exposure nuances.  One is fairly obvious, the other is not.

Most beginners tend to over-expose the moon because it seems like it should be bright.  You are used to seeing the moon at night ... so compared to everything else, it is bright.  But during the daytime, the moon is technically just as bright... but seems a lot dimmer beause your eyes are adapted to daylight instead of nighttime.

The obvious one is that just because there's a "Looney 11" rule doesn't mean you have to shoot at f/11.  That "rule" is just a quick way to know the correct baseline exposure without having to trust a light meter (in-camera metering is fooled by all the blackness of the sky and tends to over-expose unless you use spot-metering).  You can use any f-stop available by just trading stops of aperture for stops of exposure.

The less-obvious one is an issue called "atmospheric extinction".  It's the reason you don't go blind looking at the sun at sunset (but you would if you looked at it for a long time at mid-day).  It's also the reason the moon looks dimmer and more orange at moonrise or moonset.  

Extinction is the notion that when you are photographing the moon, you are looking through a lot more "air" than nearly any other subject you normally shoot.  If you're shooting people, they are not very far away from the lens... you aren't shooting through much "air" and that means issues of air transparency don't impact your exposure (unless you're shooting through a lot of smoke or fog, etc..)  With the moon, it the air can look reasonably clear, but tiny particles in the air will cut down on the amount of light you get.  

This is one reasons why... even though the moon is lit by the sun - so you'd think the "Sunny 16" rule would work -- you use f/11 instead.  There's enough air to reduce light transmission.  That's "extinction" (extinction of light ... specifically because it is being absorbed by atmosphere).  (The other reason is that the moon is not very reflective).

So then the question becomes how much air are you shooting through.  If something is in space directly above your head, then you have to look through 1 "air mass" of atmosphere.  If you're looking at something 30° above the horizon, the sin of 30 is .5 ... so you are looking through 2 (the inverse of .5) air-masses.   At 10° it works out to 5.75 air-masses *except* the curvature of the Earth makes the math a little more complicated so it really works out to be 5.6x.

Anyway, if the air really is clear you get a small impact.  If the air-transparency is poor, you have a huge impact.  This means there is no rule for how to adjust exposure based on the altitude angle above horizon... just know that the closer things in space get to the horizon, the more light is absorbed.

If you want to learn more about the technical nuances, read this article for a good intro:  https://www.skyandtelescope.com/astronomy-resources/transparency-and-atmospheric-extinction/

This may make things sound really complicated... "how will I know if I am really using a correct exposure".  This background an idea of what is happening and why.  BUT...

Ultimately you can turn on "the blinkies" (exposure clipping warnings) and make sure no part of the moon is over-exposed.  (Digital photography has all these wonderful advantages ... and this is one of them.)

[Mitsubishiman]

I set the crop factor to 1/6

[TCampbell]

I love these shots of the night sky.  Your shot has Perseus (the cluster of stars near the bottom just to the right of the tree is in the middle of Perseus and it's the "Alpha Persei Association" (an open cluster).  The brightest star in that cluster is Mirfak.  

It also has Cassiopeia, Pegasus, and Andromeda ... including the Andromeda Galaxy.  I actually do see the point of light in your photo which looks like a star, but is actually the bright core of the galaxy (you might be able to tease out more detail depending on your exposure).  

A tracking head is an inexpensive way to take much longer exposures ... these can capture enough light for nebulae to show up in the photos.  The popular models are the Sky Watcher "Star Adventurer" (they make two models) and the iOptron Sky Tracker (they also make two models).  They're around $300... $400 with all the trimmings.

[Waddizzle]

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@TCampbell wrote:

I love these shots of the night sky.  Your shot has Perseus (the cluster of stars near the bottom just to the right of the tree is in the middle of Perseus and it's the "Alpha Persei Association" (an open cluster).  The brightest star in that cluster is Mirfak.  

It also has Cassiopeia, Pegasus, and Andromeda ... including the Andromeda Galaxy.  I actually do see the point of light in your photo which looks like a star, but is actually the bright core of the galaxy (you might be able to tease out more detail depending on your exposure).  

A tracking head is an inexpensive way to take much longer exposures ... these can capture enough light for nebulae to show up in the photos.  The popular models are the Sky Watcher "Star Adventurer" (they make two models) and the iOptron Sky Tracker (they also make two models).  They're around $300... $400 with all the trimmings.

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Thanks, Tim.  it was a very clear sky in early December.  Air temperature was around 40 degrees F.  I think the camera was pointed SSE when I took this shot.  This was shot with a 6D and a Rokinon 14mm T3.1 Cinema lens.  I used my big video tripod because it was a little breezy that night, and that tripod is as steady as a tree trunk.

The tree is being lit up by a street light about 100 yards behind me.  I was surprised to see the tree, but I guess I should not have been.  I only took a few shots moving the camera to get around the tree.  

NYC was glowing in the lower portion of the sky, and was showing up in the shots.  I did not think I was getting good exposures, so I packed it in after about a few shots.  This shot is actually cropped to remove the glow from NYC.

[EDIT]. 

I have considered buying a tracking head, but I live in NYC.  I took the above shot during a visit to a relative.  Decent dark sky is at least 3 hour drive away from me.  I wish it were not so far away, because I would definitely take more exposures.

[TCampbell]

You can use a light pollution filter such as an Astronomik (that's the brand name) "CLS" filter (there's also a CLS-CCD version but you don't need the "-CCD" version.  It is designed for cameras with no IR filter.  Your camera has an IR filter so the "-CCD" version isn't needed).

These filters work by blocking the parts of the spectrum common to street lights such as Sodium & Mercury lights... but allow the other parts of the spectrum through.  By lucky chance... the emission wavelengths for deep-sky emission nebula don't coincide with the wavelengths of street lights.  So by filtering the street lights, you can greatly eliminate the light pollution.  I know astronomers who have observatories in urban skies and these filters (as well as narrowband filters) are the only way they can do any imaging at all.

There are lots of vendors who make light pollution filters, but the trick is that many of these 14mm lenses don't have filter threads (my Canon 14mm f/2.8L has a non-removable hood and no threads).  Astronomik makes a version (two versions, actually) of this filter that clip into the camera body (behind the lens).  They make a version for Canon APS-C cameras and another version for Canon full-frame cameras (they call that the EOS XL clip filter).  This means you can use the filtering regardless of what lens you use and/or if it has filter threads (that's a nice feature).  

One caveat is that if you use the Astronomik CLS "EOS Clip" on APS-C cameras, you must not attempt to mount a Canon EF-S lens.  The problem is that since an EF-S has a rear element that slightly protrudes into the camera body, it would hit the filter.  But you can use EF lenses with it.

Another caveat is that as cities begin to switch to LED street lights, those things have emission bands all across the spectrum and are not easily filtered out.  These light-pollution filters are really mostly for mercury & sodium lights.

You get moderately wonky color which will need some adjustment in post processing... but it does let you work around light pollution issues.  There are guys who just take lots of long exposures through the light pollution filter to capture the nebulae (nebulae don't glow in any colors that are blocked by the filter so they show in correct color) but the stars are full-spectrum.  Since stars are brighter, they just shoot a few extra frames to capture the stars (unfiltered) and then merge in post processing. PixInsight has a star-mask generation tool so we can grab the stars from the normal color image, but the nebulae from the filtered images ... and merge them.

These light pollution filters block a lot of light so you'll find you will need to stop down (they want you to use f/3 or above) and that means you have to use a tracking mount.  But once you use a tracking mount, time is no longer a problem... you can expose for as long as you need (even a 10 minute exposure is no problem if you have a good polar alignment.)

[kvbarkley]

Check out Ken Rockwell's What's New page (Note: this will eventually be gone if you are reading this in a few months)

He uses an EOS-R, EOS-R to EOS adapter, a Cano 1.4x adapter, a Canon 2x adapter and a Sigma 60-600 lens for the equivalent of a 1680mm focal length.

[TCampbell]

On Ken’s page, he refers to the EOS R as being APS-C.  I found that confusing because the EOS R is a full-frame mirrorless body.  Where is the APS-C coming from?