Shooting the Moon with 400mm lenses: Sigma APO and Telemegor

Gerald · Joined: 25 Mar 2014 Posts: 1196 Location: Brazil

Some people say that shooting the Moon is an excellent way of testing a telephoto lens. Well, I disagree. A test chart is a better target to test a lens, but I admit that shooting the Moon is much funnier.

This post is about specific lenses I used to shoot the Moon, but I decided to add some general comments because I thought they could be useful for who wants to photograph the Moon with different pieces of equipment.

The Moon is a bright and static subject (well, quasi static, to be exact), so the Moon should be simple to shoot, right? Unfortunately, the Moon is a very small subject, photographically speaking, and to make things even more complicated, there is a thick layer of air, the atmosphere itself, between the camera and the Moon. The atmosphere is always in motion due to wind and local temperature variations, what makes that the quality of a Moon picture depends not only on the lens performance, but also on favorable atmospheric conditions. Besides, focusing errors and camera shake can easily ruin any photo of the Moon. In summary, the results of photographing the Moon depend on the lens, the atmospheric conditions, and competency of the photographer.

Just out of curiosity, few people realize that the Moon is seen "upside down" in the southern hemisphere!? Or it is upside down in the northern hemisphere? Mr. Green

As I suppose that most of the members live in the northern hemisphere, I rotated the original pictures by 180° to a more familiar view. Razz

The lenses

a) Meyer Telemegor 400mm F5.5
My first 400mm lens was a Meyer Telemegor 400mm F5.5 that I bought second-hand.
After the photographic industries in the former East Germany were unified under the name VEB Pentacon, the Meyer Telemegor 400mm F5.5 was replaced by the slightly longer Pentacon 500mm F5.6. Optically, both lenses are based on a front and a rear doublet, which is a classic formula with elements 4 and 2 groups. After WW II, this type of construction was used by many German brands, such as Enna, Kilfitt, Meyer and Schneider. The performances of all these telephoto lenses were reasonable for the time, and they are still usable if stopped down one or two stops.

Closest focusing distance: 5.5m
Weight: 1980g
Length (∞): 320mm
Length (d=5.5m): 355mm

The Telemore is mechanically simple but robust. It uses a double helical focusing system that moves the lens as a whole. It is slow but accurate. The main limitation of this focusing system is that the closest focusing distance is 5.5m, which is a little excessive, for example, to photograph flowers and small animals. The diaphragm is a pre-set type with 19 blades that produces an almost circular aperture for all F-number.

Unlike the Pentacon 500mm, which is a monster of 3500g that can only be used on a tripod, the Telemegor 400mm is a lens that can be used handheld by brave (and fit) photographers.

b) Sigma APO 400mm F5.6
My Sigma APO 400mm F5.6 telephoto lens is the first version, the one which Sigma claimed to have designed as an apochromatic with normal dispersion glass. The secret for apochromatic correction was the thick front triplet. Unfortunately, Sigma cemented the front triplet with some synthetic glue, which degenerated over time. It seems that most lenses of this type, including mine, developed gradually a fog in one of the cement layers of the front triplet, what made the lens practically unusable.

Recently I saw on eBay a Sigma APO 400mm that appeared to be equal to my lens, but the seller's pictures showed that the lens was clear and didn't suffer from foggy cement. I ended up buying that lens, but for my surprise I discovered that Sigma had quietly changed the design. The problematic triplet had apparently been replaced by two doublets and the tripod collar, which originally was metal, was replaced by a plastic one. The overall quality of the lens was still very good, and except for the tripod collar, the rest of the les was all metal, including an integral telescopic lens hood. A bonus of the redesign was that the lens became about 300g lighter.

Closest focusing distance: 3m
Weight: 1030g
Length: 270mm

One of the high points of the Sigma APO 400mm is its internal focusing. The lens focuses an object at just 3m away with only ¼ turn of the focusing ring. The length of the lens does not change with focusing. If, instead, a unit focusing were used, the lens length would increase by more than 70mm. The focusing ring is similar in size and smoothness to a SMC Takumar 135mm F2.5 lens. The balance is very good when the lens used with a relatively heavy camera like the Sony A99. The balance of the Sigma APO is much better, for example, than the Sonnar 200mm F2.8, which is a front heavy lens. Although the Sigma has a tripod collar, it is very comfortable to use handheld.

Shooting the Moon – The Technique
The angular diameter of the Moon is about 1/2 degree, what requires a telephoto lens of 2000mm or more for a tight framing. With a lens of "only" 400mm, you have no alternative but cropping the image, or using one or more tele-converters to increase the effective focal length.

Focusing
Unless the lens is absolutely calibrated for infinity, it is best to use your own eyes to focus the Moon. OVFs in particular are not very suitable for the task; it is best to use a mirrorless camera with EVF, or a DSLR with Live View. I used a viewfinder magnification of 11.7X, which allowed a precise focus adjustment.

A display magnification of 11.7X on a lens of 1600mm (400mm lens plus two stacked 2X tele-converter) means that you are effectively seeing through a lens of 18720mm equivalent focal length! In terms of an equivalent telescope, the magnification is 265 times! With so high magnification, the simple act of touching the focusing ring was enough to shake the image, making difficult to detect the exact point of focus.

Exposure
Maybe the simplest way to control the exposure is by using the manual mode of the camera. It is very simple to estimate the correct exposition simply by observing the Moon image in the EVF or LCD. An alternative is using the spot photometer if the camera has this feature. Any way, it is important to not let the brightest parts of the Moon burn out.

Vibration control
Despite being possible to shoot the Moon handheld under certain conditions, in practice the use of a tripod is mandatory, especially when using super telephoto lenses and small apertures. However, the use of tripod alone does not guarantee a sharp picture. The greatest enemies of a sharp photograph are the vibrations caused by the shock of mirror and shutter curtains in a DSLR camera. It is important that the mirror be locked up, what happens automatically in most DSLR when using the Live View. Of course, the mirror shock is no problem in a mirrorless camera.

The shutter shock can be avoided in certain cameras that offer the EFC (Electronic First Curtain) option, such as Canon DSLRs and Sony Alphas. Including, there are cameras, as certain Panasonic models, which offer the option of a completely electronic shutter. The Sony A99 has a fixed semi-transparent mirror and EFC, so camera shake should be no problem. To avoid vibration by the operator, a remote control or the camera self-timer must be used to fire the shutter.

The pictures

The first picture was taken with the Sigma APO plus two 2X Komura Telemore II MC-7 tele-converters. The equivalent focal length was 1600mm and the lens aperture was F8 (or it was F5.6, I don't remember well). The effective aperture of lens plus tele-converters was F32 (F22?). The exposure time was 1/5s with ISO 50 plus +0.3 EV compensation.

The second photo was taken with the Sigma APO plus only one 2X Komura Telemore II MC-7 tele-converter. I had already noticed that there was no advantage in using two tele-converters. The lens aperture was F11 (F45 equivalent) and the exposure time was 1/8s ISO 200.

The third photo was taken with Meyer Telemegor plus plus one 2X Komura Telemore II MC-7 tele-converter. The lens aperture was F22 (F45 equivalent) and the exposure time was 1/5s at ISO 400. The aperture may seem unreasonably small; however a larger aperture would show excessive lateral chromatic aberration.

Conclusions and remarks
1) The Sigma APO produced an image quality considerably better than Telemegor.
2) Long shutter times are no problem with mirror lockup and EFC.
3) After comparing my pictures with those taken by Roger N. Clark, I concluded that expensive photographic lenses, like the Canon 500mm F4, do not guarantee better photos that those I took with the Sigma APO.
4) It requires a professional telescope and special techniques, like image stacking and mosaicing, to achieve considerably better results than mine

duckrider · Joined: 11 Dec 2013 Posts: 437 Location: Germany

Am I allowed to post some harsh critics?

1.: The moon might be anything, but "static" is the last thing in the world he is: He RUNS over the sky, reasonally sharp pictures need a astro mount or stacking. Take a look through a hihger magnification telescope.

2.: Your first (sharp) picture seems to be taken at a very other time than the other both. As You mention difference in atmospheric clearance is one possible reason for the differences. The last two pictures seem to be made at the same time, but did You try more than once? Give the Telemegor a second chance!

All in all I must admit that the APO Sigma has deserved a chance to be tested by me.... Wink

Thanks for Your work & don't over overrate my post, it's written as an emotionally too fast reply, tinted with some delicious Spätburgundy Redwine, there will be others with more competence following!

ForenSeil · Joined: 15 Apr 2011 Posts: 2726 Location: Kiel, Germany.

Not bad, the Sigma "APO" is better than I expected. Amazing what you got out of this lens, considering it's only 400mm and price tag.

Gerald · Joined: 25 Mar 2014 Posts: 1196 Location: Brazil

s58y · Expire: 2013-09-10

Both sets of moon pics are very nice. The OPs images are really good for a 400mm lens on a fixed tripod.

Of course, the images from the 2000mm diffraction-limited scope will be better, especially if a tracking mount (with lunar rate?) and special planetary/lunar imaging software is used for post-processing.

BTW, I've usually used from 1/125 to 1/640 second shutter speed for capturing the moon at f/8 to f/10, using 800mm (lens) or 2000mm (telescope) focal length. The goal of shooting lots of images at higher speeds is to maybe capture a few shots between "flickers" of the unsteady atmosphere. This is more important at 2000mm than at 400mm or 800mm.

enzodm · Joined: 11 Sep 2010 Posts: 350 Location: Italy

This was my moon with a Hanimex 400/6.3 (kind gift of iangreenhaigh) plus Marexar 2x teleconverter (top level equipment Smile

) on Canon 60D:
The most difficult thing for me was to maintain the moon in the field of view because it was running away.

ForenSeil · Joined: 15 Apr 2011 Posts: 2726 Location: Kiel, Germany.

Wow! Best moon shot I've ever seen from a cheapo lens!
Was it made outside or through a window? Was some kind of stacking etc. and CA-removal used?

Rick1779 · Expire: 2014-06-06

that's my moon taken with the Sigma 600mm F8 Mirror Telephoto Multicoated

Rick1779 · Expire: 2014-06-06

sammo · Joined: 04 Jan 2012 Posts: 223 Location: CH and SI

Some really good moon shots here!

Gerald · Joined: 25 Mar 2014 Posts: 1196 Location: Brazil

enzodm · Joined: 11 Sep 2010 Posts: 350 Location: Italy

Rick1779 · Expire: 2014-06-06

good idea to use the green channel, I must try myself too

sammo · Joined: 04 Jan 2012 Posts: 223 Location: CH and SI

Going to longer wavelengths, red and near-IR will lower the atmosphering blur on the photos. But it makes sense that normal photos are better in green than in red or blue, simply because of chromatic abberation green is focused the best.