CCD Group

Please review the topics below for helpful tips and tricks.

• Camera
• Telescope
• Mount
• Computer
• Software
• Power supply
• Willingness to climb a steep learning curve

• CCD = “Charge Coupled Device”
• Based on photoelectric effect (Heinrich Hertz)
• Photons in – electrons out…Proportional
• Primary unit is the pixel (Picture Element)
• Chip can have 100K’s to millions of pixels
• Circuit has an amp and A/D converter
• Signal to noise ratio (SNR) is concern

• CCD has greater light sensitivity
• Avoids reciprocity problem of film
• Almost Instant image examination
• Image “Stacking” ~ long exposure
• Can remove plane/satellite tracks

• Can use almost any type of scope, even a camera lens with an adapter
• Shorter FL scopes = shorter exposure time and less demanding tracking
• Typical scopes include 60-152mm refractors and 6-14” Newts & SCT
• f/5 or less = “fast” focal ratio scope
• Image scale is an important consideration

• The single most important component
• Must be able to track & have low PE
• Must be solid & vibration dampening
• Must be capable of supporting wt. of gear
• Should be capable of being guided
• Needs to be polar aligned for long exposures

The histogram graphically depicts the exposure of the image. The “X” axis of the histogram shows from black on the far left to white on the far right. The “Y” axis illustrates the number of photons captured along that continuum.

• Will need to manipulate digital image to bring out the image data
• Post capture data manipulation divided into “Calibration”, preprocessing & “Post processing”
• Calibration removes various types of “noise”
• Post processing “stretches” (enhances) the image data
• Involves another learning curve

• Represents bias signal already on the chip before the image is taken. (it’s always present)
• Taken at min. exposure time & the scope covered
• Taken at same temp as dark and light frame

• Taken at lowest possible exposure time with scope covered to keep light out

• Records the thermal noise of the actual exposure
• Noise increases with exposure time and ambient temp. (reason CCD’s are cooled)
• A dark frame should be taken at same time & temp. as the light exposure

• Electrical noise in system
• affected by time & temp.
• Taken with objective lens covered & same time & temp as light frame
• Must subtract bias from dark to get a “clean ”dark frame

• Flats are another type of calibration image
• They remove photosite to photosite variations and problems in the optical train (dust motes, gradients, vignetting, etc.)
• Flats need their own calibration with bias & dark frames before being used
• Must be taken with same optical set-up

• Removes Optical Train Defects. Exposure is usually ½ to 1/3 ADU of Luminance
• Must use “flat” uniform illumination

• Image + noise, Hot pixels, amp glow & dust/gradient

• 30 sec. sub –(bias, dark frame)/ flat

• Next step after image calibration
• “Stacking” combines sub frames, increases S/N ratio, simulates a long exp.
• Aligning reduces tracking errors of mount and some sky rotation in AltAz mounts

• All CCD chips are B&W
• Color requires separate RGB images (not unlike the photo pigments in the human eye’s cone cells)

EMS Spectrum	Visible Light

Two Ways to Color
B&W (monochrome) with individual RGB filters
One Shot Color with filters on Chip

• Must use separate images taken through individual RGB color filters (not visual filters)
• Need Luminance image, usually with an IR block filter, to enhance image detail,
• Result is higher resolution than 1-shot color but requires 4x the number of images

• Preprocess color image as if “raw” B&W with regard to “Bias, Darks & Flats”
• Must “deBayer” into component colors
• Software then magically combines RGB
• Post process as Tiff or Bmp

• Requires significantly longer imaging sessions than One-shot color.
• Time introduces variables (focus between filters, tracking, sky position, etc).
• Most advanced imagers use LRGB imaging

• Set-up and polar align mount & scope (drift align)
• Find target to image & critically focus
• Determine maximum exposure time
• Set software to take a series of Lum exposures (25-50)
• Take 10-15 bias frames at lowest exposure time
• Take 10-15 dark frames at time & temp of light exposure
• Take 10-15 flat frames at 1/3 to ½ ADU of light exposure
• If color, repeat with individual RGB filters (not with one-shot)
• Break-down equip. and head home (~4am)

• Calibrate all sub frames
• Align & combine all calibrated sub frames and save as separate files
• Process to merge into an LRGB image
• Post process in PhotoShop or similar to bring out detail
• Swear you’ll do better next time

• Advanced post processing techniques
• Mount tuning to improve tracking & minimize PE
• Auto-guiding
• Narrow band filters

1. Are you willing to make the commitment?
2. Will you or your bank account go first?
3. Will your marriage survive?

The Reward

You get to hang out with a great bunch of people!

• Ron Wadoski’s “The New CCD Astronomy”
• R. Scott Ireland “Photoshop Astronomy”
• Michael A. Covington “Astrophotography for the Amateur” 2^nd ed.
• Plus many others

Many people have said they are having problems controlling the Meade LPI camera from Windows Vista. The drivers are not compatible. It appears (and Simon Porter has seen it work) that the following driver from TRUST WEBCAMS will work:

www.liutilities.com/device-driver/trust-webcam-14823-driver