Philips ToUcam PRO II (Webcam)
The ToUcam is placed in the eyepiece port after removing the webcam's lens and threading,
in its place, a Scopetronix adapter equipped with an IR blocker to prevent washed-out images.
ToUcam has a 1/3" VGA CCD sensor with a video resolution of 640x480.
It is important to have the adapter fit
tightly into the TouCam's lens port. The reason is that the ToUcam has an effective focal length of 4 mm which
gives a magnification of 325 when it is coupled to the 1300 mm Questar. At this magnification the slightest movement
of the webcam and/or adapter can destabilize images (and this also means that focussing with ToUcam is a never-ending
struggle!). The desired fit is obtained by placing rubber washers between the adapter and the ToUcam. A decided advantage of
using the washers is that the adapter cannot accidentally damage the webcam's CCD chip as it is tightened.
Webcam astrophotography requires
appropriate image capture software. I use K3CCD Tools to acquire avi frames followed by the now-familiar
aligning/stacking process offered by Registax.
Both trial and permanent versions
of the latest K3CCD Tools are available, the latter be it noted for a fee, from:
In the field, after launching K3CCD
Tools, I take ToUcam off its auto exposure settings and experiment with various parameters to achieve
optimal image brightness and clarity. Note that at the start of the observing session it is useful to set the gain parameter
in K3CCD high enough to render the target visible and then to reduce it as appropriate prior to starting image capture.
As for a portable computer, I employ a Dell laptop with 512 MB RAM and 40 GB fixed memory.
Nikon 4500 Digital Camera
The Nikon was used in its "continuous mode" option
with a fixed shutter speed. The proper shutter speed was determined by trail and error based on image
brightness and clarity.
I attached the Nikon to the Questar using a
18mm wide-angle eyepiece from Scopetronix. This eyepiece has an apparent field of view (AFOV) of 66 degrees. To illustrate
how wide a field a view that is, note that the closest comparable Questar-Brandon 16 mm eyepiece has an AFOV
of 42 degrees. Thus Scopetronix's AFOV is 57% greater. An advantageous feature of the Scopetronix eyepiece
is that it threads directly into Nikon 4500's 28mm lens. This provides a tightly bonded combination which provides
stability during image capture.
The Scopetronix eyepiece yields a magnification
of 1300/18 or 72. When Questar's 1.5x Barlow is engaged a magnification of 108 is achieved. When the Nikon is
used afocally, magnifications > 108 are obtained with an optical zoom of upto 4x. One can go even higher by trigerring the
4x digital zoom. However, as magnification increases images become correspondingly more sensitive to any disturbance (e.g. jarring
the telescope, camera movement, atmospheric turbulence, ...) and are thus rendered unstable.
Leica D-LUX 3 Digital Camera
The
Leica is an ultracompact camera introduced in September 2006. Its main advantage over the Nikon is that it has a substantially
larger LCD screen (2.8" compared to Nikon's 1.5") which makes it that much easier to focus an image.
However, astrophotography with the Leica requires
a different approach from that for the Nikon since (i) Leica does not have a threaded lens so one cannot achieve that
desirable tight bond between the camera and an eyepiece; (ii) there is no way to trip Leica's shutter by remote
control; and (iii) in the "continuous" mode of the Leica, depressing the shutter button produces 3 or
5 images (depending on the selection of picture quality) after which the target has to be brought into focus before
restarting the capture process.
From item (iii), it is apparent that acquiring images with the Leica requires more time than with the Nikon. This
can prove a handicap in flighty weather conditions where one has to acquire as many images as possible before shutting
down the equipment.
In order to resolve the issues posed by item (i), I used
Orion Telescope's "SteadyPix" universal camera mount. The use of this tool is described on Orion Telescope's website at:
http://www.telescope.com/text/content/pdf/inst_steadypix.pdf.
Briefly stated, at one end of the mount is a vertically
movable clamp for an eyepiece and at the other end is a horizontally movable pedestal onto which a camera can be
screwed via its tripod attachment. Leica's tripod attachment point is off to one side of the camera but this poses no problem
since the camera can be swivelled about its point of attachment to the pedestal.
In order to avoid the dreaded vignetting of images, it
was found necessary to jam Leica's lens right up against the telescope's eyepiece. The results, especially for the
moon, are quite satisfactory as shown on my Digital Camera Astrophotography With Leica D-LUX 3 (New) page.
With respect to item (ii), I found that the use
of Leica's "optical image stabilizer" in conjunction with a 10-second self-timer allowed enough time to dampen vibrations
between manual operations of the shutter release. It is noted that the Leica was used in its "continuous mode"
option with a fixed shutter speed. The proper shutter speed was determined by trail and error based on
image brightness and clarity.
Aligning and Stacking Images
Whether using the ToUcam or the Nikon/Leica one
obtains hundreds or thousands of images or frames. These are aligned/stacked/wavelet processed using Registax (a
freeware). While one must beware of the power of software, any software, to overenhance an image experience
indicates that to get the best out of Registax:
[Note
that the latest version of Registax can be downloaded from http://www.astronomie.be/registax/.
Also, a
tutorial for Registax is available at http://www.threebuttes.com/RegistaxTutorial/RegistaxTutorial.htm.]
The final image from Registax
is unsharp masked, adjusted for contrast/color and resized, if necessary, using AstroArt 3.0. Other software such as
Adobe Photoshop Elements and Maxim DL were also occasionally used.
Note that the perils of "photo-manipulation" have attracted public notoriety
to the point of being the subject of an article in The New York Times of 24 January 2006 accessible via http://www.nytimes.com/glogin?URI=http://www.nytimes.com/2006/01/24/science/24frau.html&OQ=_rQ3D2&OP=2d5cf707Q2F.0!K.,Q24moeQ24Q24DY.Y77Q2B.7Z.Yi.omM!cm!.YileQ51pQ25Q3ADkI
Limitations
Some drawbacks in my approach stem from the fact that:
Given that,
I am limited not only to the solar system, as such, but even more narrowly to the Moon, Sun and such planets as
Saturn, Jupiter and Mars. Stellar and more detailed planetary work are out of reach.
But there is consolation
in these lines from Dante!
tanto ch'i' vidi de le cose belle/che
porta 'l ciel, per un perfugio tondo./E quindi uscimmo o riverder le stelle.
[Through a round aperture I saw appear/Some of
the beautiful things that Heaven bears,/Where we came forth, and once more saw the stars.]
Last 3 lines from The Inferno of Dante (1265-1321),
Canto xxxiv, 137-139, trans. Robert Pinsky 1994.
