Doing things the hard way, or how many teleconverters can you stack?

March 27, 2018

A long while back, before I got the telescopes I now have, I was sitting around wondering what I could do to take a full frame picture of the moon. Of course the obvious answer is get a telescope and attach your camera to it. But what could I do with the equipment I had?

Well it turns out I have a lot of misc. camera gear that I have just collected over the years. Including several teleconverters for the two film bodies I have.

So what is a teleconverter? A teleconverter is a lens you put between the lens you use on a SLR and the camera body. It magnifies the image. So if you have a 300mm lens, you can slap one of these on there and get a 600 mm lens. Cool right? They are generally a lot cheaper then buying an actual lens with the higher focal length. (For you astronomy folks, this is a barlow. Same idea, different name.)

Well nothing is free so there are trade offs with using a teleconverter. One is a loss of contrast. You get this whenever you put more glass between you and the thing. Each time the light hits the glass some of it scatters and things happen. Designers making a lens can mitigate this, but they haven’t got a clue about that extra hunk of glass you are going to add later. Besides loss of contrast, there is simple loss of light. For a 2x teleconverter you can generally count on losing 2 stops of light. In non-photography speak, this means you 1/4 the light on the backside of the teleconverter as went in. (every stop is around 1/2 the amount of light of the previous one.)

The pro to all this con was that I could use equipment I actually had right then instead of equipment I was thinking about getting.

So I rummaged around in my gear. I chose to use the Olympus OM2n for this exercise. The long lens I had for this camera was a Soligar 28-200mm 1:3.8-5.5 zoom. On top of that I stacked a Telesor 3x teleconverter and then a CPC 2x teleconverter. On top of that I stacked yet a 3rd teleconverter this one also a 2x. I think it may have been a Vivitar 2X macro focusing teleconverter.

Here are a couple of sample shots from that night:



Both of these are pretty bad. The first one has such a long exposure the moon has moved. The second also has some chromatic aberration as you can see in the orange rim near the top.

But, they demonstrate two important things. Firstly, the moon is so bright that even through the darkness of stacked teleconverters you can get enough light. Second, 2,400 mm is a good focal length for 35mm film for the moon.

This later detail I confirmed by reading the book “Astrophotography” by Barry Gordon. This is a good getting started guide for film based astrophotography.

If you want to know why you should use film for astrophotography, well, let me just say that the windmills other people tilt at never seem as interesting as our own.

In any case he explains how to calculate the amount of focal length needed given the degrees of arc across the phenomenon is. The moon is 31 arc seconds which is just over 1/2 a degree. For 35 mm film, or full frame DSLRs, the full frame focal length is 2,539.5 mm.

I also learned something of a con in my setup. At the time I had a simple pan and tilt tripod head. This was not easy to use to photograph the moon. For one thing when you had the head locked in position, it would sag under the weight of the camera. This meant to frame the shot, you had to over correct and take into account the sag once you let go. This quickly becomes frustrating. It explains why neither of these shots is framed well. I have since corrected this with a gear head as I have mentioned in other posts.

What I did not learn from this but which was a problem was that it is difficult to focus on the moon. For me at least, it is absolutely necessary to use the focusing aids that manual cameras have to get a clear shot at full frame.

So what focusing aids do manual cameras have. The most common is a split prism screen. Some DSLRs have the ability to use these because some high end lenses do not have auto focus abilities. Also auto focus can be difficult to use, or simply fail in low light conditions or when teleconverters are used with certain lenses.

The way I figured out that focusing was the problem will be covered in another blog post, but it turns out that the lens I was using was not able to focus on the moon when stacked on the teleconverters. I wonder if the lens used for the above shots had the same issue. I certainly wasn’t being as careful to focus as I have learned to be.

So lessons:

  1. Use a tripod head you are comfortable using to track the moon. It should not sag under weight when you let go of the controls. For me this is a gear head. Ball heads are notorious for sagging.
  2. 2,400 mm is a reasonable focal length for 35 mm or full frame cameras.
  3. 3200 ISO film is overkill. The moon is a bright object.
  4. Plan on using focusing aids to get that critical focus.
  5. Don’t take it for granted that your lens can focus in the given configuration.

First Head to Head

December 14, 2017

So a blog dedicated to exploring how to do something would be pointless if it did not compare methods from time to time. With that in mind it is time for the first head to head.

In this corner we have the Youniker lens, and add for smart phones that let’s you, yes you, get that perfect shot. In the other corner we have a Celestron Travel Scope.

Youniker 18x Zoom



While the Youniker kit came with a smart phone clamp, the Travel Scope did not. So an accessory, a Gorsky universal telescope adapter, was also necessary.

First the pics:

On the left is the Youniker shot. On the right is the Celestron shot.



To me the winner is clear. The Celestron shot has better detail. (It is also better exposed, but that hasn’t anything to do with the lens.)

Another point is that both shots have chromatic aberration. What’s that? That’s when you see a colored fringe near and edge in your picture. It happens because different colors bend by different amounts as they pass through the glass of the lenses. All lenses have this to some degree or another, but higher end optics have coatings on them to correct for this kind of thing. It can also be corrected by software such as Photoshop. The aberration is more apparent in the full size version of this image. There is a green fringe in the Celestron shot and a bluish fringe in the Youniker shot.

So better lenses right? In the case of the Youniker, there isn’t anything you can do except post process it out. In the case of the Celestron, I am not sure if the issue is in the main telescope lens, or the eyepiece used. If in the eyepiece, then a multi-coated eyepiece would be a simple solution. Otherwise a new scope would be required.

So the Celestron wins the first part. It has better detail, even though both fail for chromatic aberration.

But now the second part. Ease of use.

The Youniker was difficult to use. It is difficult to mount to the smart phone in the first place. It was difficult to aim at the moon. (And if you can’t just look up and see the moon, what is going on?) The little table top tripod it came with was useless for this task. Once pointed, it was difficult to get focus as this required turning the barrel of the Youniker and then tapping the screen to autofocus.

The Celestron was not a picnic either. Like the Youniker, the tripod it came with was not useful for this task. (I have since learned that these kinds of tripods work better if you do not extend the legs.) Nevertheless, the Celestron was easier to aim then the Youniker.

So the Celestron wins in both image quality and ease of use. Not that this means much. There are better ways to get a moon pic.

What about a telescope?

September 12, 2017

So last tie I posted pics and video from an experimental moon shot that used one of these big add on lenses meant for smart phones. There are many many kinds of optional do-dads to designed to extract money from smart phone photographers. But there are also do-dads designed to attach smart phones to some serious lenses. For example:


This pictured thing is a Gorsky universal telescope adapter for Smart Phones. With some patience, it allows you to line up your smart phones camera to look through the eye piece of a telescope or similar viewing device.

Intrigued, in the throes of camera gear acquisitiveness, and also on the lookout for more ways to take moon pics, I got one.

I set it up indoors, which I highly recommend. There is better light indoors. You can work out the kinks of the getting the camera lens over the eyepiece where you can see and where hopefully you will be pestered less by insects.

Like other smart phone photography gear I have tried, this one insists on mashing the buttons on the side of the phone. There is no getting around this.

Out of habit, when the smart phone screen goes off I used to press the power button. You can’t do that with this accessory. The other method is to double tab the phone’s screen.

On the whole though, I found this setup less fidly and easier to focus then the Youniker setup I talked about in my previous post. I used the same tripod and tripod head, but obviously, used a much bigger lens.


This thing was also easier to aim then the Youniker lens, despite them both being on the same tripod and head. (Not the tripod in the picture above.)

So how do these widgets do?


Clearly the best shot yet.

The notable improvements over other shots are the level of detail. It is a decent exposure as well.

What can you do with a Smart Phone and a big lens?

September 12, 2017

I took some time to get back to my moon shot experiments. A while back I had purchased a lens made to attach to Smart Phones by means of a clamp. It was red among other things.

Youniker 18x Zoom

This is described as an 18x universal optical camera lens kit. It is made by a company named Youniker. The reason I got this one instead of anything else is because it attached to the camera using a clamp rather then a plastic spring loaded clip. Also it is red.

So I got this thing because I am an acquisitive camera junkie, but once I had it I wondered if I could use it to take a Moon shot. Well yes I can.

The first time I tried this I could not get the setup to focus and it finally dawned on me that there was condensation on the lens. This is the price of living in air conditioned comfort. Well and global warming.

The second time I tried I put the setup in the garage a few hours before taking the shot. This appeared to have helped.

I say setup because I did not use the cute little table top tripod that came with it. The ball head on the tripod is difficult to adjust and when you get the moon zoomed in, it moves rather faster then you might expect it to. Meaning there is constant adjustment, something no ball head, never mind the one on this tripod, is good at.

With that in mind I put the lens on my gear head tripod head. A gear head is like it sounds. It has knobs that you can turn to adjust the equipment mounted to it in three directions. (Roll, pitch and yaw.) This has made moon shot so much easier. I can quickly make minor adjustments and line up the shot. I don’t think it would do for astro-photography in general though as you need something that can track. The gear head I have is the Manfrotto 410 Junior Gear Head.

Because I actually use my phone, I did not align it in the holder prior to going in my backyard. At night. Where it is dark. Well I live in a big city so darkish. So to align I shined a flashlight into the lens until I could see this on the screen of my phone. It occurs to me writing this I could have taken care of this in the garage. Which had a light. And fewer mosquitoes.

Setting up somewhere well lit is definitely a good idea. Set up the phone and then carefully transport to your viewing location.

As a tip if you happen to be using this lens and mount hardware on your phone. Mount it so that the phone’s lens is the lowest part. Put another way mount in upside down portrait mode. Why? Because then the weight of the phone presses the lens towards the lens and bracket arrangement. In pretty much every other orientation, the weight of the lens pulls the phone’s lens away which will cause vignetting and a smaller image.

The next challenge was actually pointing at the moon. The moon was full on the night I chose. It turned out to be pretty difficult to get it.

Once aligned I had difficulties getting the image focused. This is a two part problem with a setup like this. Firstly the Younkier 18x lens has a manual focus ring. So you adjust that. And then you have to focus the phone’s camera. There are phone camera apps that allow you to focus manually, so I could have locked in the focus. Maybe I will try that next time.

But after all that work here is the result.


This is a zoomed in shot of the moon. Meaning that I had to use the digital zoom features of the phone’s camera to get this shot. Considering the necessary distortion this adds, it turned out pretty well.

So what are the pros and cons of this setup?

Pros –

It is inexpensive for what it is. Besides your smart phone, you purchase an add on lens which runs around $30 and comes with some accessories. The lens and its accessories are pretty portable, but to use it for a moon shot you will need better a better head and tripod.

Cons –

It is endlessly fiddly. You have to get the phone aligned just so and clamp it down good so it doesn’t fall. (Mine fell out once.) This is problematic as you can’t use it with a camera case. You know, the thing designed to protect your phone in the event of a fall? The magnification is less then ideal for a moon shot. Another problem is that the clamp, and pretty much every clamp I have tried, interferes with the phones button on the side of the phone. (My phone at least. Your phone may be fine.) This can be annoying when the phone is trying to power off because the power button is being held. Why not clamp somewhere else? Because the clamp has to fit on where the lens attachment is over the lens of the phone. My phone also has a curved back further complicating getting the lens set up right.

Overall, if this is the gear you have, you can make it work. The main thing is get a better tripod head and tripod. (The tripod head I used is many times more expensive then the lens. Think about that when considering this plan.)

Here is a link to a video I took while getting this picture. You can see me fiddling with the manual focus on the lens, the auto focus in the camera app and also the adjustments on the tripod head.


April 9, 2017

What is my moonshot project about? It is about taking a good picture of the Moon. You may think this is not very ambitious. Try it.

What I want to do is get a full frame image of the moon that I can blow up and put on my wall. I will most likely get images at full and at several phases. (Full moons are less interesting, but more on that later. Besides, during a full moon everyone is busy coping with their lunacy.)

I suppose the seed for this starts with my Dad. A family story tells about a 5 year old version of me sitting with him under the stars and learning the constellations. I apparently never forgave him when we moved far enough away that what I had learned wasn’t right anymore. My Dad also gave me his camera, a Canon FTb, along with the kit he has assembled. Two Vivitar Series 1 lenses, a 35-85mm f2.8 zoom, and Vivitar Series 1 100-300 mm along with a good traveling set of other interesting gear.

This interest in stars stuck with me even though the heavens had shifted, and one of my favorite school trips was to the planetarium for the classic constellation show.

Too my horror, I have discovered recently that planetariums don’t show constellation shows as often.

About a year ago I got a course from a company called the Great Courses called Our Night Sky. The Great Courses get college professors in front of a camera or sometimes just a microphone and have them talk about some subject. The Night Sky is 12 30 minute lectures on the things you can see at night presented by Professor Edward M. Murphy of the University of Virginia.

Professor Murphy suggests, when talking about the moon, that you actually go out and look up at it every night for a month. I recommend this too.

For one thing, it gives you an appreciation of the fact that our calendar months are approximately the amount of time it takes for the moon to go through a whole cycle.

For another, this is a natural wonder accessible to everyone. Even if you live near a city, the moon is so bright, you can see it.

It does take some planning though. For instance you need to find out when the moon is up. I have been using an app for my tablet for this. One specific to phases of the moon, and another that shows you the night sky. The first app is useful to know when the moon will come up. This second app is useful if you don’t know what direction the moon is going to rise from.


April 3, 2017

A long time ago, I sat out on my drive way and took some pictures of the moon. I know I was in South West Austin, and the it had to be from 1998 to 2005.

Like many photographer before me, I tried to take some pics of the moon. I no longer know what kind of gear I used, but I believe that I used a Canon FTb with a Vivitar Series 1 100 – 300mm zoom lens. I also used a vintage (even then) table top tripod.

Here is a challenge for you. Use a table top tripod on your drive way and take some pics of the moon. Go on. Get your face right down there to the concrete. (I could have gotten a sensible sized tripod. I could have gotten a table to go with the table top tripod. I did none of these things.)

The Canon FTb is a strictly manual camera with only a match needle light meter built in. This mean when you look through the view finder, there is a needle that indicates the amount of light in your scene. You adjust the aperture so that the aperture indicator in the view, is more or less lined up with the needle. (I was using print film. You can be pretty sloppy with your exposure on print film.)

This needle is black. The night sky is black. See a problem? Or maybe don’t see a problem? Actually, just move that part of the viewfinder to look at the moon, make the adjustment and then move back. (Remember the part about print film? If you ever get into film photography, just remember this magic phrase. Print film has a wide latitude. It will make sense later.)

The shots did not turn out well. Part of the reason is that the moon moves across the sky rather quickly. (If you actually understand astronomy, you know that last sentence is not exactly correct.) So to take a good picture of the moon, you need to have a short exposure time. (Relatively short.) The shots I took that had good exposure time, did not allow enough light to reach the film. The shots that did get enough light had the aperture open so long, the moon looks smeared across the frame. (So yes, even with the latitude of print film, you can still get an underexposed shot.)

The two most pleasing are the underexposed ones. These let you see the “seas” on the moon.


Blurry, may be out of focus or simply moving to fast for the exposure time.


Definitely moving too fast.


The length of time keeps the moon “frozen” but is underexposed and grainy. (Insert chorus of “Let it Go” here…


Another one with good shutter speed, but too slow film.


The aperture was open too long. The details are washed out and the moon is moving across the frame. Also there is no graininess from underexposure.


This one is close. Good time exposure that freezes the motion, but too much light that washes out the detail. Maybe can fix with Photoshop or similar?


Another blurred edge and washed out details.


Another one that is close.


Omar reacting dangerously to moon light. Look out! Look out! Or is he just yawning?

October 29, 2009

This is a test of the category system.

Getting Started in Robotics

June 6, 2009

Hello again. This is Robotchef with this weeks article about robotics. This week we are going to discuss several ways to get started in robotics.

So how do I get started?

Get Help!
The single most important bit of advice I can give to a budding roboticist is to get help. Any activity is more fun when done with a group of like minded people. Such a group of people can offer help and encouragement as you work on your project. In addition you get to see their projects grow.

There are several ways to find this kind of help. Firstly, look for a robot group in your area. In the previous post I mentioned The Robot Group which operates in the Austin, TX area. The Dallas Personal Robotics Group operates out of the Dallas, TX area. The easiest way to find such a group is to use your favorite search engine with the words “robot” and the name of the city where you live.

If a live robot group is not a good choice for you, there are still a lot of live resources you can tap into. One such resource is forums. Forums are a kind of bulletin board. As a member, you post an article. Other members read your post and can make comments on it. For example, you could ask for recommendations for a micro-processor developers kit and get recommendations from other members of the forum. One such forum is the Society of Robots. (Hint: Forums can be a very useful way to find out about a lot of things. Try looking for forums the next time you are stumped by a problem.)

Still another way to find information is newsgroups. Newsgroups are a predecessor of forums that date back to the beginning of the internet. Newsgroups generally require a bit of software to gain access and you may have to pay to access the service. Most e-mail clients support newsgroups. You will want to contact your internet service provider about newsgroups to see if that is included with your service. A guide on how to get started is here. Here is a sample list of robot related newsgroups.

Lastly, another live way to use the internet to connect with people and learn about robots is e-mail lists. A simple way to look for such a group is to go to or and type “robot” in the search area. Another way is to use your favorite search engine on the terms “robot” and “mail list”.

Membership in such a group is not requirement to build a robot, but it can add a lot to your robot building experience. After you get the hang of robot building, be sure to help other new members of whatever group you join.


Besides the internet, there are many many books on the subjects for robotics. Everything from getting started to the latest techniques in navigation or using robotic limbs to manipulate delicate objects.

For beginners, I personally recomend Mobile Robots by Joseph L. Jones and Anita M. Flynn. This is the book I got started with. Even if you do not want to build the two example robots in the book, you can learn a lot about the techniques used for motor control, sensors, and other things. As a note, it appears that the second edition of Mobile Robots is the subject of a lawsuit between Anita M. Flynn and the publisher A.K. Peters. All things being equal, I think I would recommend the first edition of the book.

In addition to books, there are also several magazines of interest to the robot building community. Two of these are Nuts and Volts and Servo Magazine

Finally, you should never forget the WWW. In addition to the forums, newsgroups and e-mail lists discussed earlier, there are Wiki’s, blogs and just plain old fashioned web pages. These will cover general robotics and also specific technologies that go into making a robot. (For example using accelerometers for dead reckoning navigation or a tilt sensor.)

OK, but how do I get started?

Right you are! There are three ways to get started right away. You can buy a kit. You can take an existing bit of electronics and ‘hack’ it or kit bash it. Lastly you can build one up from scratch.

Robot Kits

The world has a plethora of robot kits ready for you to build and requiring a range of skill. The great grand-daddy of all robot kits is the Heathkit Hero. A more recent but also wildly successful kit is the LEGO Mind Storms. Once again the internet is your friend and a search on your favorite engine can give you nearly endless lists for kits of all difficulties.

Kits are convenient. All the parts needed usually come with the kit along with detailed asembly instructions. All you need are some tools and some time. The downside to kits is that you may spend more time building them then in undestanding the principles used to make the kit work.

Hacks and Kit Bashing

The word hack has a long and varied history. In the case of this blog it refers to one of two things. Firstly hacking can be the art of taking an existing system, such as the iRobot Roomba. Check out “Hacking the Roomba“, and many other websites for things you can do with these little guys.

Kit bashing is the art of taking several kits and making something totally different or something far in excess of the original intent of the kits. It is a term that comes over from the Model Building community, but applies well to robotics.

As a homework assignment, I would have you look around you for things that you could hack. A good place to look is the toy department of whatever store you are in.

From Scratch

“In order to make an apple pie from scratch, you must first create the universe.” Carl Sagan

Of course you can always build your robot from scratch. You, and only you, get to make every decision of design. Will it be pink? Will it have a flame thrower?

The downside to this is that in order to make every decision, you have to know quite a bit about everything that goes into a robot. While hacking the Roomba limits you to a smallish round disk, you also get quite a bit of engineering taken care of for you. The power supply, recharge, and motion control is already designed into the package. Your hack adds on to it.

But if these limts are too, well limiting, you can always go from scratch.

In this case it is good to know about some of the small parts providers that you will be needing to get that from scratch robot out of your head and on the pavement.

Small Parts Inc.
Allied Electronics
Fry’s Home Electronics

OK Now What?

First, I hope this article has inspired you to reach out to the robot building community near you so you can learn more. Second, I hope it has inspired you to look around you and see what kinds of things you can turn into a robot.

The next article is going to be more nitty gritty detail. I am going to do a tear down of the toy I am going to hack. We are also going to start with a schematic. (I promised nitty gritty detail.)

See you next time!

What is a Robot?

May 26, 2009

Hi,This is Robot Chef!

This is the first in a series of blogs that will cover how to make a robot. The articles will be a mix of theory and nitty gritty, grease under your nails, grab your soldering iron details.

What is a robot anyway?

In the broadest sense, a robot is an autonomous machine that can perform some task. The autonomous part means that you don’t have to tell it what to do. A robot car would need you to tell it where to go, but would figure how to get there by itself. What task the robot performs is as varied as the human imagination. It can be anything from drilling holes in sheet metal, to teaching kids about American history.

Lots of things qualify as robots under this definition. The Voyager space probe is a kind of robot. There are robot planes, cars, submarines, dogs and cats. A lot of robots look like humans in some way. A lot of robots look like animals too. Still others look like nothing in nature.

Why do you want to make a robot?

Because they are cool! Ok, not get a date, or dance with the stars kinda cool, but hey sometimes you have to make sacrifices to accomplish the really important things in life, right?

There are many many reasons to build a robot. Since the Industrial Revolution people have been using machines as ways to replace human labor. The machines often are faster, more precise, and more repeatable then human craftsmen and women. This means that more things can be made in less time and for less money. Increasingly industrial robots have been part of this trend.

Robots are often used to perform tasks that are too dangerous for humans such as exploring the depths of the ocean or working in radio active environments. Several robots have been made to defuse bombs, or enter situations where a human might be shot.

Robots are labor saving devices. Robots have been made to do everything from serving tea to vacuuming your floors.

One of the greatly underestimated areas of robotics is in art. Robots have long been part of the movies and other forms of entertainment. This form of art is sometimes called animatronics. More formally, robots have entered captured the imagination of artists and the results can be seen in many galleries. One such gallery has a website here. For those of you that live near the Austin TX area there is a group of Robotic Artists there.

Finally one of the more important reason to build a robot is for education and research. Teaching people about robotics exposes them to a wealth of knowledge on modern technologies and how they are used. This can be a good way to teach kids and young adults about engineering. Even a simple robot will require knowledge of electrical engineering, software engineering, and mechanical engineering. (Don’t worry. You can make a robot without going to college.) Many people use robots to research new ideas and learn more about nature. This is done by making robots that mimic our understanding of the world around us. One such robot project sought to mimic the way insects move. This was done by giving them 6 legs and by modeling ideas about how insect nervous system swork.  More can be read about these robots here.

Are robots a new idea?

Nope. The word itself goes back to 1920 when it was used in the science fiction play ‘R.U.R. (Rossum’s Universal Robots)‘ by Karel Čapek. The word was coined by Karel’s brother, Josef Čapek, when Karel asked him for help naming the artificial beings in his play. Josef suggested roboti from the Czech word robota which means hard work especially that done by a serf.

The idea goes much farther back then that. Ancient Greek mythology tells of Hephaestus making mechanical servants. In the far east, a report of an artificial man that had the cheek to wink at the ladies of the court is reported to have happened between 1023-957 BCE. For more on the history of robots, go here.

Now what?

Hopefully this has whetted your appetite for robotics in general. I encourage you to think about what kind of robot you want to build or what kinds of things you want to know about robotics.There is wealth of information on the internet.

In the comming articles I will discuss various issues about making a robot. The next article will specifically talk about how to get started in robotics. From then on there should be a new article once a week. See you then!

Hello world!

May 22, 2009

Welcome to This is your first post. Edit or delete it and start blogging!