Introduction to OSLO optical design software

This is my guide to understanding the OSLO lens designing program.  OSLO is available as a free download from:

WARNING:  This page is slow to load because it contains many images.  I have tried to keep the file sizes small while keeping good image quality.  I believe these images are the best way to show how to use OSLO.

  OSLO has a good help program which is included with the program, but it is written for optical engineers.  Still, it is a good tool which can answer many of your questions.  I suggest that you look in the help file when you have a question.  Most of us who are amateur telescope makers would benefit from a simpler introduction to OSLO.  This is my goal with this introduction to learning how to use OSLO software.  I plan to make several pages which cover the basics of using OSLO.  This page will consider opening a lens file and navigating in OSLO.

  I will be happy to try and answer specific questions.  Please email me at:

  I recommend the book Telescope Optics, by Rutten & van Venrooij.  The subtitle is "A Comprehensive Manual for Amateur Astronomers".  It is available from Willman Bell publishers.  This book is a good guide for telescope optics.  It covers the major types of telescope designs and eyepiece designs also.  It will give a solid foundation about optical designs and optical evaluations.  This book discusses subjects like: optical aberrations, glass types, and basic optics.

  It took a lot of time for me to become comfortable using OLSO.  But I have found OSLO to be an easy program to learn to use.  It is a powerful tool for optical design and evaluation.  I encourage you to experiment with OSLO and play around a bit.  You are not likely to mess up the program by making some changes to an optical design.

  Hold your mouse cursor over an icon and OSLO will give a description about what this icon does.  OSLO also allows right clicking in many cases.  Right clicking will often display a dialog box which has several options.

This is the way OSLO LT (version 6.1) looks on my computer when I start the program:

  There are three windows opened on this page.

  The top left window says command.  It has three icons on the left side, a green check, a red X, and a yellow question mark.  You will not use this window very often.

  The second window is located on the left, below the first window we looked at.  This window is identified as TW1.  This window is where the text information will be displayed.  I don't use this window very often when I am working with OSLO.

  The third window is on the upper right side.  This window is identified as GW1, or perhaps it might have another title such as UW1.  This window is where OSLO displays the analysis of an optical design.  I will discuss this window on a different web page, which is called OSLO ANALYSIS.

  OSLO will permit many additional windows to be opened along with these three default windows.  They will be identified as something like TW2, or GW2.  I don't open additional windows very often.

  Now, let's open a lens file and examine it.  I will go step by step in case you are not very familiar working with Windows.  Look in the upper left corner of the OSLO window.

  In the upper left corner, you will see where it says File.  Left click on this.  A drop down dialog box will open.

  Click on Open Lens.  A small window will open which has the title Open Lens File.

   We will need to navigate to the folder which has our lens files in it.  Click on the box in the lower right corner which is called Public.

  I want to open a demonstration file (demo).  Double click on "demo".  Some computers have MS Windows set to open a folder with a single click, while many computers are set to open a folder with a double click of the left mouse button.

 Now click, or double click on LT to open this folder.  This is the folder which has demonstration lenses for our free "LT" version of OSLO.

  I want to examine the hubble file.  Click on "hubble" to select this file.  This is the design of the Hubble Space Telescope.  This is a Cassegrain reflecting telescope design, which uses two curved mirrors to form an image.  Then click on Open.  You should see this:

  The new window in the upper left corner shows the Surface Data.  This is where the information is entered for an optical design.   I will explain how to enter design data into this Surface Data window on the next web page called OSLO Data Entry.

  If you don't see the Surface Data window then you can open it by clicking on the blue lens in the upper left corner.  It is located on the left side just below where the toolbar says  File Lens.  Left clicking this icon will open the Surface Data window.  When the Surface Data window is open the blue lens turns grey, when you close this window the grey lens will turn blue again.

  You can save this file with a new file name.  Click on File, then Save As, and enter a new name.  I suggest putting it in the Private folder.  I keep all the files I modify in the Private folder.  I have several sub folders in my Private folder, like one for reflectors, one for refractors, and another one for eyepieces.  When you have changed a file, it is a good idea to save that file with a new name.  This way the original file is not changed, and you can always go back and look at it.  We really have not changed this file yet, but when we try to close it OSLO will ask if we want to save the changes to the current lens file.  I am in the habit of clicking on NO when prompted like this.  This way I don't overwrite an existing file by mistake.  I save it with a new name if I want to accept any changes.

  We did not get very far with learning how to use OSLO on this page.  But I wanted to start slowly for those who are not familiar with opening new windows.  The next sessions will cover more information.  I hope they are easy to understand.  Please contact me if you have comments or questions.

Steve Fejes