Color vs. Mono Camera Match
SBIG ST-2000XCM color camera vs. the ST-2000XM mono w/filters

  There is an ongoing debate between the arenas of CCD imager's about the performance of the one-shot color cameras appearing on the market that was once dominated by mono CCD's. A lot of pro and cons have been discussed on this subject. Having own and used both cameras extensively I decided to conduct my own tests to finally put results, instead of theory or hearsay, on the table. I've conducted a series of tests that include acquiring and processing data from both the XCM color camera and the mono XM w/filters. Both cameras use the same Kodak KAI-2020 CCD's with the same electrical characteristics which makes this a very fair comparison. The only difference between the two cameras is the Bayer mask used with the XCM CCD sensor, which is the focal point of performance differences.

  Every effort was made to acquire the data with similar outdoor environmental conditions, sub-exposure times, overall exposure times, CCD temperature, and same OTA. CCDInspector was used to select the best consistent frames between each data set. I have included objects that range from simple gaseous nebulas to more intricate structures such as the M1 crab nebula. This was to allow a more accurate evaluation of the performance of the two camera types with respect to color accuracy, signal to noise, star shape reproduction and resolution ,to name a few, in order to show their strengths and weaknesses in each category. These tests are to display the 'out of the gate' performance of each camera type before more involved processing is done. All relevant environment data is included with each image set.

My Disclaimer- This is not a test to compare SBIG cameras, but instead to compare the two types of CCD technology that are used in some of the SBIG camera models. These very same CCD's are also used in other camera manufacturer and the results should be approximately similar.
The results displayed here were based on the equipment I have and seeing conditions so your mileage will vary.

This is truly an apples to apples comparison.

Unless mentioned otherwise the following were used for all tests:
  • OTA - TMB 130-SS APO F/7 - Image scale 1.68 arc seconds/pixel for both cameras
  • Mount - Losmandy G11, non Gemini
  • Location - Backyard - Abbott Observatory, NY
  • SBIG ST-2000XM mono camera w/CFW8 & Custom Scientific LRGB filters
  • SBIG ST-2000XCM color camera
  • 2" Baader UV/IR filter for use with ST-2000XCM
  • 2" Astronomik 13nm H-a filter for H-alpha tests
  • Images Plus 2.75 - Processing Software for calibration, stacking, DDP and R/L Deconvolution
  • Adobe CS2 - Post calibration processing
  • CCDSoft - Image acquisition and guiding
  • CCDInspector - Evaluate individual data frames
  • Focusing - FocusMax using 3 focus runs @ 7 iterations each per focus session
  • Image Processing - 16 bit TIFF, Display - uncompressed JPEG
  • All local weather conditions reported by with a substation 2 miles from my house.

Comparison Test Sections:
For accurate display results images are not compressed and may be large.

Round 1- H-Alpha Performance

Round 2-Color Performance - Emission Nebula DSO

Round 3-Color Performance - Reflection Nebula DSO

Round 4-Color Performance - DSO w/O-III and H-Beta

Round 5-Resolution Performance

Round 6-Exposure Time Comparison

Round 7-Star Cluster Comparison

Round 8-The XCM Hybrid

Round 9-Selecting a Good Display Size

Round 10-Meet the Contender's

Judging- In Summary

© 2008 Michael A. Siniscalchi