Newt for the Web

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The Yellow Sample Design is the build-it-youself Dob at Stellafane.org/tm/dob

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Newtonian Telescope Specifications

Use this form to input and adjust your telescope design values.

Unit of Measure

Project Info

Title		These fields allow you to add a title to your design and add notes or comments about a specific design
Notes

Optics

Primary Mirror Diameter		Typically 4¼, 6, 8, 10 or 12½ inches
Focal Ratio		= Focal Length / Primary Diameter
Diagonal Mirror Minor Axis		? Typically .75, 1.0, 1.3, 1.52, 1.83 inch
Diagonal Sizing Assistance: Involves Conflicting Goals - Please Read Help ?
		Find range of error free diagonal sizes
100% Illuminated Diameter: 0.75 inch		Maximize, ½ inch or 12mm typical.
Diagonal Obstruction of Primary Diameter: 25%		Minimize, 20% or less is a good goal.

Tube

Tube Inside Diameter		? Allow ½ to 1 inch around primary mirror
Tube Wall Thickness		Adds to overall Focuser Height
Focuser to Front of Tube		Measure from Center of Focuser
Mirror Face to Back of Tube		Allow room for Mirror Cell
Fixed Diameter Baffles		? Tapered Baffles if not checked

Focuser

Focuser Minimum Height		? Outside Tube to Top of Focuser
Spare Focuser In Travel		? Allows for Eyepiece Field Stop Variations.
Additional Height for Camera		? Optional, to focus on Camera Film Plane
Focuser Inside Diameter		? Typically 1.25 or 2.00 inches

Eyepiece Performance with this Telescope Design

Eyepiece Focal Length	Power	Exit Pupil	Apparaent Field	True Field
mm	34.8x	4.38 mm	°	1.005°
mm	48.8x	3.13 mm	°	1.394°
mm	135.5x	1.13 mm	°	0.295°
mm			°
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Display:
Ray Trace ? Zoom in on Diagonal & Focuser:

Performance Information for your Telescope

The theoretical limiting magnitude for a 6 inch objective is 12.7.

The obstruction of the primary surface area by the diagonal is 6% which results in a reduction of light gathering ability. ?

The theoretical resolution (Dawes limit) for a 6 inch objective is 0.76 arc seconds.

The obstruction of the diameter of the primary by the diagonal is 25%, which affects image quality by increasing diffraction and lowering contrast. ?

Maximum useful power is about 300x (for 50x per inch of aperture).

Minimum useful power is about 21.8x (for a 7mm exit pupil).

Angular field of view for the 100% illuminated area is 0.8973°. The diameter is 0.7477 inch ?

Angular field of view for the 75% illuminated area is 1.4112°. The diameter is 1.1760 inch ?

If you see "NaN" where you expected a number, the specifications resulted in incalculable results, such a division by zero or some other mathematical problem. "NaN" is an abbreviation for Not a Number.

Dimensions for your Telescope

Unit of Measure	inch
Primary Mirror Diameter	6.000
Focal Length	48.000
Focal Ratio	8.000
Tube Inside Diameter	7.000	?
Tube Thickness	0.125
Focuser Minimum Height	3.000	?
Focuser Inside Diameter	1.250	?
Focuser Extra Travel	0.250	?
Focuser Camera Travel	0.000	?
Diagonal Minor Axis	1.500	?
Diagonal Offset	0.047
100% Illumination Diameter	0.748	?
75% Illumination Diameter	1.176	?
Front Aperture Diameter	7.149	?
Mirror Face to Focuser Hole	41.125
Focuser to Front End of Tube	6.000
Mirror Face to Back of Tube	3.500
Tube Length	50.625

Dimensions for the Baffles ?

The 75% ray is vignetted by the inside of the tube at the front.

The tube inside diameter should be a little larger, or the diagonal minor axis could be made smaller to shrink the illuminated field.

The baffles can't be calculated until the vignetting at the front is corrected.

If you see "NaN" where you expected a number, the specifications resulted in incalculable results, such a division by zero or some other mathematical problem. "NaN" is an abbreviation for Not a Number.

Newt for the Web (Newt-Web for short) is a Newtonian Telescope Computer Aided Design program. It ray traces a Newtonian telescope design checking for vignetting, optimizes diagonal size, calculates baffle sizes and positions, and produces performance and dimensional data for construction. It runs in your web browser - there is no need to install a program on your computer.

To get started:

Use the File tab to load an existing design or sample designs.
Use the Specifications tab to enter a design of your choice.
Click ? for help on items it is near, or see the Help tab for a list of topics.
Many items, such as tabs or buttons, provide extra information if you hover over them.

Newt-Web V1.2-0088 Built on 2024-Sep-26

Thanks to Dave Tabor, Julian Shull, Matt Considine, Michael Patterson, Dave Prowten, Glenn Becker & Dale Keller
for their help, expertise, ideas and advice during development of Newt-Web.
Newt-Web is based upon NewtWin and the Newt25 sources by Dale Keller; See Dale Keller's Newt Software Page

Browser Size: 1280×720

Screen Size: 1280×720

Newt-Web is released under the GNU General Public License Version 2 (Click link to view).

Source code for the current, running version. Right click and use the "Save Link As..." function to download and save each file.

newt-web.html newt-web.css newt-web.js newt-save.php	newt-calc.js newt-file.js newt-info.js telescope.ico	newt-specs.js newt-trace.js newt-draw.js	newt-help-ap.html newt-help-scope.html newt-help-ver.html newt-help-gpl.html
If you can't download newt-save.php, then download newt-save.php.zip instead.

General Help Information

Click the Help Icon ? for help on topics it is near. If you hover your mouse over the icon, the help topic it links to will be displayed in a tiny pop-up window.

Help links in the Newt-Web application panes open in a new window in your browser. Note that many people choose an option in their browser to open new windows as new browser tabs (not Newt-Web application tabs).