Dennis Webb's Imaging Techniques and Equipment

Recent Images | Image Processing | Homemade Lightbox

I have been making astronomical images with telescope and CCD camera since early 1997. I was inspired by the exploits of coworkers Al Kelly and Chuck Shaw. My equipment and technique has improved considerably in this time.

imaging system in side yardI am currently using a Cookbook 245 CCD camera (bought originally as a used CB211 through Astromart at Chuck Shaw's prodding). During the conversion to 245, I added a temperature sensor (Radio Shack $14 cheapie) on the coldfinger with the readout velcroed to the mount. My primary optical system for 2000 is a homemade 5" f/3.6 reflector depicted at right. Primary was made by Bob Taylor and he also provided a optical window supporting a unique secondary assembly. This gives a 48x36 arcminute field of view with 7 arcsecond pixels in the 378 mode.

I integrated the optics and camera into the overbuilt plywood monster you see. I use an extra-long dew/light shield since I have streetlights in sight of my home observing location. The camera is attached to an Andy Saulietis color filter wheel (filled with Edmund RGB's) that itself attaches to a rotating focuser board. Focus is adjusted across a narrow range with a wingnut on a bolt working against springs with two other bolts relieving the springs when I get to desired focus. Because I had some focus shift with the initial crummy design, I now have a nylon through teflon bearing surface that makes the focus travel smoother. I have previously used the camera as a CB211 with a range of Minolta camera lenses, my favorite being a nice Vivitar 200mm f/3.5 - I have used 28mm, 50mm, 135mm and 400mm lenses.

I find objects by starhopping using an 8x50 finder and a Telrad. Rarely can I see the object to be imaged through the finder so I look for star patterns in the finder using Uranometria and validate that I am on the right object by comparing a trial exposure on the screen to a deep paper finder chart printed out using Megastar, showing the hoped-for CCD field of view in a wider field. I never look through the primary optics as I would have to remove the camera.

I normally shoot multiple 60-second unguided shots with the camera and finders attached to a Takahashi EM-1 german equatorial mount (also found through Astromart). Image acquisition is with Richard Berry's 245PLUS running on an old 386 desktop (500MB Hard drive) with an old 14" VGA monitor, both provided by Triple Nickel. The monitor has a red plexiglas screen filter provided by Chris Randall. I have designed and built a homemade lightbox for making good flatfields, although I am now using a simpler design built around Cool Whip tubs and a single white LED. I transfer raw images to my home 233 MHz desktop using a parallel zipdrive and zipdisks for processing using Berry's MULTI, CB245 an old version of Photoshop, and occasionally Christian Buil's WINMIPS and IRIS. 1999 was a very productive year and I had to buy an HP CD Writer to keep up with the volume. I have also discovered XEROX "Fiery" printer at the local copy shop for producing excellent $2.50 11"x17" color prints, if your image is not too subtle.

waiting for leonids in the moonlightI shoot regularly in my suburban Houston sideyard (above picture) where I have a narrow bit of light polluted sky, although setup is very quick. I can take the show on expedition (the setup is shown at left at the Johnson Space Center Astronomical Society 1999 Leonid Expedition at Fort McKavett, TX).

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This page built by Dennis Webb and updated on October 15, 2000.