SBIG ST-2000XM

    In late July 2005 I purchased a SBIG ST-2000XM, a CFW-8A color filter wheel, and a set of Astrodon LRGBCHa filters. The filters are advertised as parfocal, and yielding true color with equal exposures of the RGB filters. I purchased the I-Series filters that are designed to match the spectral characteristics of the Kodak interline CCD's, such as that in the SBIG ST-2000XM. The E-Series is for cameras that use Kodak full-frame CCD's. Additionally, the blue and green Astrodon filters are designed with equal responses at the primary OIII emission lines to give a more realistic teal color to planetary nebula. My image of M27 below, taken my first night of CCD imaging (other than with a ToUcam), compares favorably with the image published on the Astrodon site that was taken with a ST-10XME.
    When using the ST-2000XM (7.4 micron pixels) with my Takahashi FS-102 at f/6, the resolution is approximately 2.5 arc seconds per pixel. A more ideal resolution would be 1 arc second per pixel. Even with this mismatch between pixel size and focal length, for nebulae and galaxies I will continue to use 2x2 binning for the RGB images. I compared the NGC6992/6995 below (LRGB unbinned) with one I took on 30 July 2005 (L unbinned, RGB 2x2 binned, not shown), and I couldn't see any difference. The advantage of 2x2 binning is increased sensitivity and thus decreased exposure time. Thus I can devote more time to taking luminance images to improve signal-to-noise. For M13 I used LRGB unbinned due to the density of stars, though I have not taken a comparison image with RGB binned 2x2 to test if unbinned RGB is beneficial in this case. Comparing Double Cluster images suggests 1x1 binning is beneficial compared to 2x2 binning (see below for discussion regarding sensitivity testing of Double Cluster images to get rid of blue halos). The improvement  is most evident at the lower left of the core NGC869 where more overlap of stars occurs at 2x2 binning.
    Some problems are noticeable on my images, including stars of intermediate brightness having a blue edge and a pink edge, or sometimes completely surrounded by a blue halo. The orientation seems to change depending where in the field of view a star is located, suggesting that the image field is not flat. On very bright stars (see IC5067/5070, NGC6960, and NGC7000) the dispersion of green wavelengths is greater than for red or blue, giving a noticeable green edge. I'm not sure if this is due to the color correction of the telescope optics and/or the focal reducer, different dispersion characteristics of each of the filters and/or their interaction with the wavelengths for which the scope is optimized, the flat-field issue, and/or internal reflections. The current suggestion is that I need a Minus-Violet filter because the scope optics may not bring the violet and ultraviolet wavelengths to the same focal point as the other visible wavelengths. I tried using my IDAS light pollution filter that has a cutoff in the far-violet, and the problem was not ameliorated. My first Double Cluster image (4 September 2005) has many stars with blue halos. For this image, as most others before it, a mid-range brightening was applied to only the luminance image. The most dramatic reduction of blue halos occurred through modifying my post processing by also performing a mid-range brightening of the RGB frames then shifting the lower histogram cutoff to the middle of the histogram peak. However, this only works when the LRGB frames were all taken at the same resolution, as in the Double Cluster image of 27 November 2005. Using a Minus-Violet filter had a secondary but discernible beneficial effect in reducing the blue halos in a second image also taken 27 November 2005. However, using the Minus-Violet filter requires either longer blue exposures or an atrifical increase in the weight of the blue frame in the color combine which makes it a bit more challenging to get a realistic color balance.
    A close eye will spot the occasional dust donut. However, beginning with my 24 Jaunuary 2006 images I have been able to apply flat-field images for calibration. While patiently monitoring the image acquisition I noted that the background to CCDSoft is a neutral grey. By holding the laptop screen up to the end of the telescope I was able to take flat-field images.
    There is sensitivity to using a luminance frame in the color combine.  Using the luminance frame tends to wash out color in one version of M42 compared to a second version in which it is excluded. Of course the beneficial impact of using the luminance frame is the visibility of the more tenuous outer envelope of the Great Orion Nebula.
    A special thanks to Gert Gottschalk for helping to show me the ropes of CCDSoft, and for encouragement and advice.

Click on the pictures to see full size versions.
 
IC1318/LDN889/Do10
L(6x10min), RGB(3x5min; 2x2 bin)
IDAS Light Pollution Filter
Takahashi FS-102 @ f/6 (625kb)
Luminance Frames Only (645kb)
  9 October 2005


IC1369A and van den Bergh 142
L(47x5min), RGB(13x5min; 2x2 bin)
Takahashi FS-102 @ f/6 (908kb, 980kb)
 
The left image was created with my standard image processing technique. The right image indicates that dramatic improvement can be obtained with the application of Lucy-Richardson deconvolution to the luminance image.
  19, 26 August 2006


IC5067/5070 (The Pelican Nebula)
L(6x10min), RGB(3x5min; 2x2 bin)
Takahashi FS-102 @ f/6 (712kb)

  28 August 2005

IC5146 (The Cocoon Nebula)/B168
L(6x10min), RGB(4x5min; 2x2 bin)
Takahashi FS-102 @ f/6 (837kb)

  3 September 2005

NGC281
L(7x10min), RG(3x5min; 2x2 bin)

IDAS Light Pollution Filter

Takahashi FS-102 @ f/6 (692kb)
  9 October 2005

NGC221(M32)/NGC224 (M31)
L(4x10min), RG(3x5min; 2x2 bin),
B(2x5min; 2x2 bin)
Takahashi FS-102 @ f/6 (451kb)

  4 September 2005

NGC598 (M33, The Pinwheel Galaxy)
L(4x10min), RGB(3x5min; 2x2 bin)
Takahashi FS-102 @ f/6 (711kb)

  6 August 2005

NGC884/NGC869 (The Double Cluster)
L(6x10min), RGB(4x5min; 2x2 bin)
Takahashi FS-102 @ f/6 (772kb)

  4 September 2005

NGC884/NGC869 (The Double Cluster)
LRGB(3x10min)
Takahashi FS-102 @ f/6 (729kb)

  27 November 2005

NGC884/NGC869 (The Double Cluster)
LRGB(3x10min)
Minus Violet Filter
Takahashi FS-102 @ f/6 (785kb)

  27 November 2005

NGC896
L(6x10min), RGB(3x5min; 2x2 bin)
Takahashi FS-102 @ f/6 (707kb)

  4 December 2005

NGC1976 (M42)/NGC1982 (M43)
LRGB(3x10min), RGB(3x10min)
Takahashi FS-102 @ f/6
(364kb, 300kb)
  27 November 2005


NGC2023/NGC2024/B33
H-aRB(5x5min; 2x2 bin)
Takahashi FS-102 @ f/6
(101kb)
CFW malfunctioned selecting the H-a filter rather than the green
filter. H-a, R, and B images used in the RGB color combine bins.
  24 January 2006

NGC2068 (M78)
L(32x5min), RGB(10x5min; 2x2 bin)
Takahashi FS-102 @ f/6 (986kb)

  The night was very windy with poor seeing, and the
guide star was moving substantially on the CCD.
21 January 2007


NGC2437 (M46)/NGC2438
LRGB(10x5min); 3 iterations of LR on L
Takahashi FS-102 @ f/6 (1.5mb)

The red color at the edge of the planetary nebula, NGC2438, compares well with the image by Jim Misti (processed by Rob Gendler) taken with a 32" Ritchey-Chretien.
http://www.robgendlerastropics.com/M46JM.html
  First image taken with AP1200 GOTO mount.  12 March 2007


NGC3034 (M82)/NGC3031 (M81)
L(6x10min), RGB(3x5min; 2x2 bin)
Takahashi FS-102 @ f/6 (440kb)

  25 February 2006

NGC3628, NGC3627 (M66),
NGC3623 (M65)
LRGB(30x5min)
Takahashi FS-102 @ f/6 (755kb)
Color Processing by  Gert Gottschalk
Luminance Frames Only (980kb)
Three asteroids were noted on the processed image, see the attached PDF presentation (2.1mb) describing the method used to identify them.
17-18 March 2007



NGC4406 (M86)/Virgo Cluster
L(16x10min), RGB(7x5min)
Takahashi FS-102 @ f/6 (305kb)
Luminance Frames Only (422kb, 507kb)
45 galaxies down to 20th magnitude are visible!     29 April 2006



NGC5194 (M51)/NGC5195
L(10x5min), RGB(4x5min)
Takahashi FS-102 @ f/6
(330kb)
Luminance Frames Only (200kb)

  26 May 2006


NGC5457 (M101)/NGC5477
L(22x5min), RGB(11x5min)
Takahashi FS-102 @ f/6 (376kb)
Luminance Frames Only (181kb, 264kb)
  30 May 2006



NGC6205 (M13)/NGC6207
LRGB(2x10min)
Takahashi FS-102 @ f/6 (652kb)

  3 September 2005

NGC6514 (M20, The Trifid Nebula)
L(3x10min), RGB(3x5min; 2x2 bin)
Takahashi FS-102 @ f/6 (601kb)

  3 August 2005

NGC6523 (M8, The Lagoon Nebula)
L(5x10min), RGB(3x5min; 2x2 bin)
Takahashi FS-102 @ f/6
(546kb)
 
3 August 2005

NGC6611 (M16, The Eagle Nebula)
L(4x10min), RGB(2x5min; 2x2 bin)
Takahashi FS-102 @ f/6
(602kb, 579kb) 
These images use the same input data, but the luminance data has been manipulated differently between the two images.
3 August 2005


NGC6618 (M17, The Swan Nebula)
L(4x10min), RGB(2x5min; 2x2 bin)
Takahashi FS-102 @ f/6
(746kb)
 
31 July 2005

NGC6820/NGC6823 (Uranometria and Burnham's do not list a name for NGC6820, I suggest either the Elephant's Trunk Nebula or the Anteater Nebula)
L(48x5min), RGB(12x5min; 2x2 bin)
Takahashi FS-102 @ f/6 (837kb)

  24June, 1 July 2006

NGC6853 (M27, The Dumbbell Nebula)
L(3x10min), RGB(2x5min; 2x2 bin)
Takahashi FS-102 @ f/6 (830kb)

  30 July 2005

NGC6888 (The Crescent Nebula)
LRGB(3x10min)
Takahashi FS-102 @ f/6 (1.1mb)

  6 August 2005

NGC6960 (The Veil Nebula)
L(6x10min), RGB(3x5min; 2x2 bin)
Takahashi FS-102 @ f/6 (1.1mb)

  3 August 2005

NGC6992/6995 (The Veil Nebula)
LRGB(3x10min), RGB(1x5min)
Takahashi FS-102 @ f/6 (1.0mb)
 
6 August 2005


Pickering's Triangular Wisp
(This is an unnumbered
component of the Veil Nebula)
L(6x10min), RGB(3x5min; 2x2 bin)
Takahashi FS-102 @ f/6 (1.0mb)

  3 September 2005

NGC7000
(The North American Nebula)
L(6x10min), RGB(3x5min; 2x2 bin)
Takahashi FS-102 @ f/6 (680kb)

  28 August 2005

NGC7293 (The Helix Nebula)
L(24x5min), RGB(6x5min; 2x2 bin)
Takahashi FS-102 @ f/6 (524kb)

  23 September 2006

Sh2-132
L(6x10min), RGB(3x5min; 2x2 bin)
Takahashi FS-102 @ f/6 (992kb)

  These images use the same input data, but the luminance data has been manipulated differently between the two images.
4 September 2005



All photos are copyright K. R. Sperber
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