Jun 14 2010

Backlighting a 11″ Zambuto Mirror
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I was pretty sure my 11″ Zambuto mirror was due to be stripped and recoated but I had no idea that it was in such bad condition. Here are a couple of photos of the mirror that shows how badly the coating has deteriorated. The photos were made in a dark room with my Canon XSi DSLR. The shots were made at ISO 100, 30 second exposures during which I ‘painted’ the back of the mirror with a red light. The amount of red light ‘leaking’ through the coating is very obvious. Here are two photos of the 11″ mirror (click on images to view larger representations):

 


 

 

As a comparison, here are similar photos of a recently re-coated 8″ mirror:

 

 

 

May 20 2010

Eyepiece Data
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The following table shows the eyepieces that I currently use with my 11″ Starmaster (f/5.4). Also shown in the table are the eyepieces’ apparent field of view, the magnification when used in the 11″ Starmaster, the calculated true field of view, and the measured true field of view:

Eyepiece Apparent FOV Magnification Calc. True FOV Meas. True FOV
TMB Optical 3.2mm 60o x472 0.13o 0.125o
TMB Optical 6mm 60o x252 0.24o 0.23o
Nagler Type 6 9mm 82o x168 0.49o 0.50o
Nagler Type 5 16mm 82o x94 0.87o 0.88o
Panoptic 27mm 68o x56 1.21o 1.17o

11″ Starmaster focal length = 11in. x 25.4mm/in. x 5.4 = 1509mm.

Magnification = (scope focal length) / (eyepiece focal length)

Eyepiece calculated field of view = (Apparent Field of View) / Magnfication

The eyepiece’s calculated field of view is found in a non-tracking scope by centering a star in a given eyepiece then timing how many seconds the star takes to leave the field of view. Divide this number of seconds by 120 to get the true size of the field of view in degrees. (Repeat several times for each eyepiece to be sure of the reading.)

Jan 17 2010

2010 Phases of the Moon
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New Moon First Quarter Full Moon Last Quarter
  day hr min | day hr min | day hr min | day hr min
        |       |       | JAN 7 10 39
JAN 15 7 11 | JAN 23 10 53 | JAN 30 6 18 | FEB 5 23 48
FEB 14 2 51 | FEB 22 0 42 | FEB 28 16 38 | MAR 7 15 42
MAR 15 21 1 | MAR 23 11 0 | MAR 30 2 25 | APR 6 9 37
APR 14 12 29 | APR 21 18 20 | APR 28 12 18 | MAY 6 4 15
MAY 14 1 4 | MAY 20 23 43 | MAY 27 23 7 | JUN 4 22 13
JUN 12 11 15 | JUN 19 4 29 | JUN 26 11 30 | JUL 4 14 35
JUL 11 19 40 | JUL 18 10 1 | JUL 26 1 37 | AUG 3 4 59
AUG 10 3 8 | AUG 16 18 14 | AUG 24 17 5 | SEP 1 17 22
SEP 8 10 30 | SEP 15 5 50 | SEP 23 9 17 | OCT 1 3 52
OCT 7 18 44 | OCT 14 21 27 | OCT 23 1 36 | OCT 30 12 46
NOV 6 4 52 | NOV 13 16 39 | NOV 21 17 27 | NOV 28 20 36
DEC 5 17 36 | DEC 13 13 59 | DEC 21 8 13 | DEC 28 4 18

*All Dates and Times are given in Univeral Time (UT)

 

Jan 07 2010

2010 New Moon Weekends
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Here is a tabulation of the date and time of each new Moon during 2010.  Also tabulated is the best weekend that comes nearest each occurance of a new Moon:

  • New Moon on Friday, January 15 @ 0711 UT
    • Best Fri. – Sun. Weekend: Jan. 15, 16, 17
  • New Moon on Sunday, February 14 @ 0251 UT
    • Best Fri. – Sun. Weekend: Feb. 12,13,14
  • New Moon on Monday, March 15 @ 2101 UT
    • Best Fri. – Sun. Weekend: Mar. 12,13,14 (See Note below)
  • New Moon on Wednesday, April 14 @ 1229 UT
    • Best Fri. – Sun. Weekend: Apr. 16,17,18
    • Alt. Fri. – Sun. Weekend: Apr. 9,10,11
  • New Moon on Friday, May 14 @ 0104 UT
    • Best Fri. – Sun. Weekend: May 14, 15, 16
  • New Moon on Saturday, June 12 @ 1115 UT
    • Best Fri. – Sun. Weekend: June 11,12,13
  • New Moon on Sunday, July 11 @ 1940 UT
    • Best Fri. – Sun. Weekend: July 9,10,11
  • New Moon on Tuesday, August 10 @ 0308 UT
    • Best Fri. – Sun. Weekend: Aug. 6,7,8
    • Alt. Fri. – Sun. Weekend: Aug. 13,14,15
  • New Moon on Wednesday, September 8 @ 1030 UT
    • Best Fri. – Sun. Weekend: Sept. 10,11,12
    • Alt. Fri. – Sun. Weekend: Sept. 3,4,5
  • New Moon on Thursday, October 7 @ 1844 UT
    • Best Fri. – Sun. Weekend: Oct. 8,9,10
  • New Moon on Saturday, November 6 @0452 UT
    • Best Fri. – Sun. Weekend: Nov. 5,6,7 (See Note below)
    • Star Party: Nov. 1 – 7
  • New Moon on Sunday, December 5 @ 1736 UT
    • Best Fri. – Sun. Weekend: Dec. 3,4,5

Note: Daylight Savings Time begins March 14 and ends November 7.

Dec 16 2009

Javascript Astronomy Applications
Posted by admin in astronomy, programming
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I finally decided to sit down and really learn some Javascript programming.  The end result is two apps that I put together and is available here.

The first app reads the user’s computer time and displays the local time, local date, GMT, time zone offset from GMT, Julian date, and local sidereal time with continuous updates every second.  The only input required is the user’s longitude and this is only used for the local sidereal time calculation.  Through the use of a cookie, once the user enters the longitude the first time, this value will be remembered the next time the app is invoked.  Being a Javascript application, this is a “client side” program that runs only on the user’s local machine (as opposed to a “server side” program that runs on the server hosting the called website.)

The second application is useful for astro-imagers.  This app, also written in Javascript, takes the user’s input of the pixel size of a CCD imaging device and the scope’s focal length to calculate the image scale for the given scope/camera combination.  Additionally, it will then take this calculated image scale and, using the user’s input of the number of rows and columns of pixels of the same CCD imaging device, calculate the field of view in arcminutes and in degrees.  Error checking is provided to make sure the user enters valid numbers for the calculations.

More Javascript apps are in the works and will be added as they become available.

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