Specifications

Section 5 - Hints and Tips
Page 31
in the CCD camera view. The chip is only .1 x .13 inch in size and 90 degree diagonals are
never rotationally collimated to optical axis close enough to use for CCD work. Special laser
collimated diagonals are available for this purpose as well as CCD framing oculars with
exact reticle patterns to match the CCD chip.
• Digital setting circles with hi-res encoders (1/12 degree or better) can get you close to faint
objects if you are polar aligned and they are "dialed in" as well.
• Integrating Software Bisque's "The Sky" software into your imaging system is another help
in object acquisition, but adds new complexity to the operations until after you are
comfortable with CCDOPS and CCD imaging. It is then a very interactive tool.
• Don't bother with deep sky imaging on an Alt/Az configured mount even if it tracks.
Image rotation results and precludes co-adding, etc. in most instances. Use a wedge and
polar align such systems for best and simplest results.
• Wait for both telescope and CCD camera to thermally settle in before trying for optimal
results. Typically wait 1/2 to 1 hour after setting up and running. This is a good time to set
up software, balance scope, and polar align, etc.
• Use a dew shield on SCTs to prevent dewing and minimize stray light. Re-balance as
necessary. CCDs have a tremendous dynamic range. Bright stars at the edge of the field
can spray light across nebula, especially Veil, Horsehead, California nebulae. Anti-
blooming can't help scattered light. Reposition field slightly and try again.
• Due to small 10 micron pixels (.0004") the TC-255 works best at shorter focal lengths of 12" -
80". An 8" aperture is an ideal match for this imager. A bigger scope and larger chip will
just scale results like a larger format 6x7 camera compared to a 35mm camera. A TC-255
and 8" SCT can offer years of imaging capability before plunging into bigger/better with
more money. Tricolor should be the next progression before scaling up.
• Fast telescopes with high resolution optics offer remarkable imaging characteristics with
CCD cameras, especially tricolor. Exposure times are short, excellent tracking is easier,
signal is awesome, therefore contrast of colors in deep sky objects is spectacular enough to
warrant color dye sublimation prints that rival photographic color prints done with film
through much larger telescopes at a much higher difficulty level. Takahashi Epsilon, Flat
Field cameras and specialized SCTs are hard to match in performance.
• Off-axis guiding is necessary to fully exploit the great imaging potential of your CCD
camera. Even with an 8" SCT @ f/6.3, the 50" focal length offers 1.6 arc seconds/pixel
resolution, much finer than optimum photographic results. Many of the software's sample
SCT images were off-axis guided to produce small round high resolution stars. No matter
how good your mount is, count on guiding to get the most from your CCD camera.