3towers Observatory Moon web cam imaging

Mosaic of the Full Moon on December 23, 2007

The major features on the Moon are labeled

The 12-inch f/10 Meade LX 200 telescope at the 3towers Observatory was used for extensive Lunar photography. The earliest images were taken at prime focus with an f/6.3 focal reducer effectively operating at f/6.5 producing an 80-inch (2000 mm) focal length.  Later Lunar imaging used either the f/10 prime focus (focal length 120-inches, 3000 mm) or a 2x Barlow system coupled to the f/10 prime focus of the telescope. This later technique gave a focal ratio of f/20 with a 240 inch (6000 mm) focal length. 

For Lunar and planetary imaging, the telescope was equipped with a variety of interchangeable web cameras.  Initial imaging was performed with a Philips ToUcam Pro PCVC740K web camera.  Later imaging used either a Lumenera SKYnxy 2-0 monochromatic camera or a Lumenera SKYnyx 2-1 color camera. Monochromatic or color images were obtained depending on the sky conditions and the result desired result. 

Since June 2014, a Celesteron 14-inch f/11 telescope situated in a second dome (Dome 2) has been used for lunar and planetary imaging, either at f/11 3910 mm (154 inches) focal length or at f/22 7820 mm (308 inches) focal length. This telescope is currently used with a ZWO ASI1034 web camera.

General Formula:
D = (W x 3438) / (F) 

Where D is field of view in arcminutes, F is focal length, and W is the size of a chip dimension length or width (pixel size x # pixels).  F and W have to be in the same units.

For the C-14 telescope:

f/11 = 3910 mm or 3,910,000 microns 

f/22 = 2X Barlow = 7820 mm or 7,820,000 microns

I.  Philips ToUcam Pro PCVC740K web camera contains a CCD chip with 640 x 480 5.6 micron pixels. 

f/11 = 3.15  x  2.4 arcminutes        0.30 arcseconds/pixel

f/22 = 1.6  x  1.2 arcminutes         0.15 arcseconds/pixel

II.  Lumenera SKYnyx 2-0  contains a CCD chip with 640 x 480 7.4 micron pixels: 

f/11 = 4.16 x 3.12 arcminutes           0.39 arcseconds/pixel

f/22 = 2.08 x 1.6 arcminutes           0.18 arcseconds/pixel

 III.  Lumenera SKYnyx 2-1 contains a CCD chip with 1392 x 1040 4.65  micron pixels.

f/11 =  5.69 x 4.27 arcminutes            0.25 arcseconds/pixel

f/22 =  2.85 x 2.14 arcminutes            0.13 arcseconds/pixel

IV. ZWO ASI1034 contains a CCD chip with 728 x 512 5.6 micron pixels

f/11 = 3.58 x 2.69 arcminutes           0.30 arcseconds/pixel

f22 = 1.80 x 1.35 arcminutes            0.15 arcseconds/pixel

To check the accuracy of web cam imaging for Lunar measurement, the widths of selected Lunar craters were measured with the Philips ToUcam. The diameter of the craters were calculated using the small angle formula as shown below. Each feature width was measured in pixels with Maxim DL Version 4.01 (Diffraction Limited, Ottawa, Ontario). This pixel value was converted into arcseconds using the factor 0.58 arcseconds/pixel for the Philips ToUcam working at f/6.5 with the Meade LX 200 telescope. The date each image was obtained was correlated with the Moon’s distance from the Earth for that date as shown in LunarPhase Pro. To estimate the accuracy of this methodology, the following features were measured and compared to their sizes (LunarPhase Pro):

*Calculations: Philips web cam CCD chip 640 x 480 pixels. Pixel size = 5.6 microns, 0.58 arcseconds/pixel

Small Angle Forumla: D = (a x d) / 206265

D = Linear Size in kilometers; a = Angular size in arcseconds; d = Moon distance in kilometers.

These measurements show this method for determining the size of a Lunar feature from the images obtained at the 3towers Observatory is reasonably accurate.   The Table below lists standard formations found on the Moon.  Various representatives of these Lunar features are shown in the web cam images displayed on this web site.

Table  Lunar Formations*

* Taken from Rukl 2004