ScopeCalc Ver. Version 1.0 December 22, 1989 Programmed by Michael S. Franzyshen Copyright 1989 by DynaSoft Technologies This software is being released as SHAREWARE. If you find it useful, please send $5.00 to the address below. You may not disassemble its code, reduce it to any other machine readable format, or incorporate any of its routines in other programs, without prior consent of its author. Source code is available for the nominal fee of $10.00, which will also entitle you to full registration and updates. While these fees are reasonable, I understand that this program will have a limited "audience". At the same time I ask those that do use it, to uphold the terms of the shareware agreement. ScopeCalc is a small program that I wrote to analyze various performance indices of astronomical telescopes. It is written primarily for amateur astronomers that would like to evaluate a given optical system without doing all of the calculations by hand. By providing a few key values, the user can evaluate the limiting magnitude, resolution, magnification, and focal length of the optical system, as well as other important information. - Running ScopeCalc 1.0 - ScopeCalc can be run from either the CLI or Workbench environments. To run from the Workbench, simply click on the program's icon. If you prefer to run it from the CLI: Run ScopeCalc. After the program starts running the ScopeCalc window will open. At this point the program is waiting for input. There are 7 string gadgets in the window, From top to bottom the string gadgets are: TELESCOPE APERATURE: In this gadget you must enter the aperature of the telescope. The aperature refers to the diameter of the lens (in a refractor, or cassegrain) or mirror (in a refelector). The value that you enter for the APERATURE MUST BE IN INCHES, otherwise the results of ScopeCalc's work will be incorrect. For example, if I have a 3" refractor, I would enter a value of 3 in the aperature box. If I have a 50 millimeter refractor, I would enter a 2 in the aperature box, because there are 25 millimeters to one inch. For the most part, telecope aperatures are stated in inches, which is why I have conformed to inches. FOCAL RATIO (F-Ratio) : In this gadget, you must enter the Focal Ratio. The focal ratio is loosely refered to as the "speed" of the system. It is directly related to the telescopes focal length. Most, if not all manufacturers supply the F-Ratio with the specifications of the telescope. If you cannot find the F-Ratio with the documentation supplied with the telecope, there is a way to figure it out yourself. F-Ratio = Aperature/Focal_Length Where Aperature is the telescope's Aperature, and Focal_Length is the length the image must travel before coming to a focus. For example, if I have a 6 inch reflector, and the telescope has a focal length of 48 inches, then the telescope's Focal Ratio is 8. EYEPIECE FOCAL LENGTHS: At the bottom of the window, along the left hand edge, are the eyepiece focal length gadgets. The important thing to with respect to these gadgets is that data should be entered in millimeters. This is the single most common way of specifiying eyepieces, so I decided to stay consistent with that convention. You do not need to fill in ANY of the eyepiece focal length gadgets, but this is one of the more useful aspects of ScopeCalc. - What ScopeCalc will Actually Tell Me - After entering the appropriate data, ScopeCalc will calculate the following values: MAXIMUM EFFECTIVE MAGNIFICATION: This is basically self explanatory, but a few points should be made. Theoretically, the maximum magnification of a telescope should be 100X the aperature expressed in inches. However, this is under ideal conditions, and a closer value will be more likely 60X the aperature. This is the value that ScopeCalc assigns as the Maximum Effective magnification. Under the steadiest seeing conditions, you may find that you can push the magnification marginally higher. The value that ScopeCalc produces is applicable under most circumstances. LOWEST EFFECTIVE MAGNIFICATION: Just as a telescope has a maximum magnification it also has a lower limit. For the most part this ranges from 3X to 6X the aperature in inches. ScopeCalc assigns the Lowest Effective Magnification to a value of 5X the aperature. For example, if I have an 8 inch telescope, the lowest power that I can expect to use is approximately 40x. VISUAL LIMITING MAGNITUDE: This expresses the faintest star that a telescope can display to the observer. It is directly related to the telescope's aperature, so the larger the aperature, the fainter the objects that you can hope to see. An interesting point to keep in mind is that by doubling the aperature of a telescope you increase its light gathering ability by a factor of four. Therefor, an 8 inch telescope gathers four times the light of a 4 inch telescope. You can see what effect this has on the limiting magnitude by comparing the results of both a 4 inch aperature, and an 8 inch aperature. DAWES LIMIT: This expresses the resolution of a given telescope. The resolution refers to the telescopes ability to show two very close objects as distinct from one another. When a smaller telescope is near it's theoretical limit of resolution, the two objects tend to "blend" into ONE indistinct object. By using a larger telescope, the observer will be able to "resolve" the objects and show them as TWO distinct objects. FOCAL LENGTH (Expressed in INCHES): This field refers to the overall distance (in inches) that it takes for an image to come to a focus within the optical system. It is calculated through the following formuala: Focal Length = Aperature * Focal Ratio If we have a system that has an aperature of 8 inches and a focal ratio of 10 (F/10), then the system has a focal length of 80 inches. EYEPIECES (Expresses in millimeters): There are five fields for you to enter the focal length of the eyepieces that you will use with a given telescope. If you don't know the focal length (expressed in millimeters) either check with the manufacturer or look on the barrel of the eyepiece, the focal length may be found there. After entering the eyepiece focal lengths, ScopeCalc will calculate the magnification that will result when using them with a telescope of the specifications that you defined earlier; aperature, focal ratio, etc. It will also give you a recommendation as to whether this eyepiece can be effectively used with the telescope specifications that you have defined. This recommendation is based on the results of MAXIMUM and MINIMUM EFFECTIVE MAGNIFICATION values. ScopeCalc simply determines whether the eyepiece magnifications fall within or outside of these two values, and then makes its recommedation. - Gadgets - CALCULATE Gadget - After you have entered the data, hit the CALCULATE gadget, and all of the values will be calculated for you. ScopeCalc will only calculate eyepiece magnifications if you have defined the telescope's FOCAL LENGTH. This is because the focal length of the telescope is an integral value when calculating magnification. If no FOCAL LENGTH is supplied, ALL eyepiece magnifications will yield ZERO, and the associated recommendation will always be NO. QUIT Gadget - Select this gadget to exit the program, or alternatively, select the window close gadget in the upper left hand corner of ScopeCalc's window. CLEAR Gadget - Select this gadget to clear all of ScopeCalc's gadgets, and calculated data. - NOTE - If ScopeCalc fails to calculate after selecting the Calculate Gadget, it has failed to locate the floating point MATH LIBRARIES on your system disk. You have probably deleted them, all you have to do is copy them back to a valid system disk, and ScopeCalc should perform without any further trouble. If you have any questions or comments, I may be contacted at one of the following: CompuServe: 71210,2522 Pro-Graphics BBS: (201) 469 - 0049 Send mail to MICHAELF Please mail all shareware donations and requests for source code to the following address: DynaSoft Technologies 23 Mercury Street Somerset, NJ 08873 (201) 356-6833