SaratogaSkies Jim Solomon's Astropics

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M42 (The Great Nebula in Orion)

[Hα+R G B]

Mouse-over to see annotations. (Requires Javascript) Click to see high-res version.

Image Details:

Camera: Mofidied Canon Rebel XT (350D): Hutech Type I Filter Replacement
Mount: Celestron AS-GT
Scope: Orion ED80 (80mm f/7.5 APO Refractor)
Configuration: Focal Reduced
Additional Optics: William Optics 2" APO 0.8x Reducer/Field Flattener
Filter: Hutech Hα Front Filter (HA-FF)
Effective Focal Length: 480mm
Effective Focal Ratio: f/6
Exposure: 31x4m, 11x30s @ ISO 400 (RGB); 21x8m, 10x1m, 10x15s @ ISO 1600 (Hα)
Total Exposure: 5hrs, 10min
Date: 2/20/2006 (RGB); 1/7/2007 (Hα)
Location: Saratoga, CA, USA
Acquisition: DSLRfocus
Focus: DSLRFocus
Dithering: GADFly 1.0.5
Guiding: GuideDog via Philips ToUcam Pro II (840k) through Orion ST80 w/ Celestron 2x "Kit" Barlow

Processing:

  • IRIS: Dark subtraction, registration, gradient removal, high dynamic range compositing
  • JimP: Flat field, Kappa-Sigma Stacking, White balance, HαRGB combination, ASINH stretching
  • Photoshop: Levels, cropping, JPG conversion
  • Neat Image: Noise reduction

Image Description:

This is an update of my previous M42 image, with 3hrs of Hα exposure added to the existing RGB data. The Hα really helps bring out many of the features in this busy field.

To create the HαRGB composite, I used the original RGB data for Hue and Saturation, and used the equivalent of Photoshop's “Screen” blending mode to combine the luminance of the original RGB data with the (grayscale) Hα data. This Screen-blended Luminance, along with the Hue and Saturation of the original RGB image, was then converted back to RGB. This method seemed to preserve details in the non-Hα-emitting regions, provide excellent detail in the Hα regions, and preserve the colors.

Processing M42 provides a significant challenge because its dynamic range is so enormous. Long exposures are required to bring out the faint wisps of nebulosity, but those long exposures have the core/trapezium region completely blown out. So, short exposures are required to capture the detail in the bright, core/trapezium region. The typical method to combine the short and long exposures is using layer masks in Photoshop, as described well by Jerry Lodriguss. But for this image, I used IRIS's merge_hdr command to automatically merge and blend the various exposures into hdr (High Dynamic Range) images. The technique worked extremely well throughout the entire Hα image, as well as in the core region of the RGB image. However, it struggled to merge some of the clipped stars in the RGB image (away from the field center), perhaps due to registration imperfections. All in all, though, I'm extremely happy with this technique, and kudos to Christian Buil (author of the IRIS software) for this implementation of HDR.

Mouse-over the image to see the Hα image in grayscale. Mouse-off to see the HαRGB composite. A higher-resolution image is also available. North is up.

 
M8/M20 (Widefield)
SaratogaSkies Jim Solomon's Astropics

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M8/M20 (Widefield)

[Hα+R G B]

Mouse-over to see annotations. (Requires Javascript) Click to see high-res version.

Image Details:

Camera: Mofidied Canon Rebel XT (350D): Hutech Type I Filter Replacement
Mount: Celestron AS-GT
Scope: Canon EF 200mm f/2.8L II USM lens
Configuration: Prime Focus
Additional Optics: n/a (Prime)
Filter: None
Effective Focal Length: 200mm
Effective Focal Ratio: f/2.8
Exposure: 16 x 4min @ ISO 200
Total Exposure: 1hrs, 4min
Date: 8/23/2005 9:07:47 PM PDT (start)
Location: Saratoga, CA, USA
Acquisition: DSLRfocus
Focus: DSLRFocus
Dithering: Manual
Guiding: GuideDog via Philips ToUcam Pro II (840k) through Orion ST80 w/ Celestron 2x "Kit" Barlow

Processing:

  • IRIS: Dark subtraction, registration
  • JimP: Flat field, Kappa-Sigma Stacking, White balance, ASINH stretching
  • Photoshop: Levels, image scale, JPG conversion

Image Description:

This is "First Light" for my brand-spanking-new Canon EOS Digital Rebel XT (350D), modified by Hutech to remove Canon's standard "IR Blocking" filter which, unfortunately, blocks a lot more than Infrared. In particular, it blocks much of the Hα wavelength, that deep red color found in emission nebulae et. al., which is so prominent throughout the universe. This Hutech mod is a replacement of that standard filter with their Type I astronmical filter which only blocks IR and UV but lets the Hα wavelength pass. The camera was a 40th Birthday present from my dear wife, Lyena. She totally rocks!

Anyway, this is a well-traveled field in Sagittarius containing two of the showcase Messier objects of summer: M8 (the Lagoon Nebula) and M20 (the Trifid Nebula), plus the NGC 6559 Region that Rich and I recently shot with his modified 300D. Moonrise limited the exposure time to just over an hour. More would have been better, but the reality is that this was just a test shot to make sure all of the hardware and software was functioning. This is the full frame, shrunk for display on the web. A full resolution image is also available. North is right.

 
NGC 1499 (California Nebula)
SaratogaSkies Jim Solomon's Astropics

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NGC 1499 (California Nebula)

[Hα+R G B]

Mouse-over to see annotations. (Requires Javascript) Click to see high-res version.

Image Details:

Camera: Mofidied Canon Rebel XT (350D): Hutech Type I Filter Replacement
Mount: Celestron AS-GT
Scope: Orion ED80 (80mm f/7.5 APO Refractor)
Configuration: Focal Reduced
Additional Optics: William Optics 2" APO 0.8x Reducer/Field Flattener
Filter: Hutech Hα Front Filter (HA-FF)
Effective Focal Length: 480mm
Effective Focal Ratio: f/6
Exposure: 26 x 8min @ ISO 800 (RGB); 33 x 8min @ ISO 1600 (Hα)
Total Exposure: 7hrs, 52min
Date: 1/9/2007 (RGB); 1/8/2007 (Hα)
Location: Saratoga, CA, USA
Acquisition: DSLRfocus
Focus: DSLRFocus
Dithering: GADFly 1.0.5
Guiding: GuideDog via Philips ToUcam Pro II (840k) through Orion ST80 w/ Celestron 2x "Kit" Barlow

Processing:

  • IRIS: Dark subtraction, registration, gradient removal
  • JimP: Flat field, Kappa-Sigma Stacking, White balance, ASINH stretching
  • Photoshop: HαRGB combination, Levels, cropping, JPG conversion

Image Description:

This is NGC 1499, aka the California Nebula in the constellation of Perseus. (Tilt your head to the right if this nebula doesn't resemble the State of California in the USA.) Unlike previous HαRGB composites, I did all the combining of the Hα and RGB in Photoshop. First, I used the Hα in “Linear Dodge” mode to pre-saturate the Red (33%) and Blue (3%) channels, and then used the Hα as Luminance at 50%. The result looked better than I could do with my own software in “trial and error” mode.

Mouse-over the image to see the Hα image in grayscale. Mouse-off to see the HαRGB composite. A higher-resolution image is also available. North is up.

 
NGC 2244 (Rosette Nebula)
SaratogaSkies Jim Solomon's Astropics

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NGC 2244 (Rosette Nebula)

[Hα+R G B]

Mouse-over to see annotations. (Requires Javascript) Click to see high-res version.

Image Details:

Camera: Mofidied Canon Rebel XT (350D): Hutech Type I Filter Replacement
Mount: Celestron AS-GT
Scope: Orion ED80 (80mm f/7.5 APO Refractor)
Configuration: Focal Reduced
Additional Optics: William Optics 2" APO 0.8x Reducer/Field Flattener
Filter: None
Effective Focal Length: 480mm
Effective Focal Ratio: f/6
Exposure: 30 x 8min @ ISO 1600
Total Exposure: 4hrs, 0min
Date: 2/22/2006 7:40:04 PM PST (start)
Location: Saratoga, CA, USA
Acquisition: DSLRfocus
Focus: DSLRFocus
Dithering: GADFly 1.0.5
Guiding: GuideDog via Philips ToUcam Pro II (840k) through Orion ST80 w/ Celestron 2x "Kit" Barlow

Processing:

  • IRIS: Dark subtraction, registration, gradient removal
  • JimP: Flat field, Kappa-Sigma Stacking, White balance, ASINH stretching
  • Photoshop: Levels, cropping, JPG conversion

Image Description:

This is NGC 2244 et. al., aka, the Rosette Nebula in the constellation of Monoceros. The catalog numbers of this object are in dispute (cf Haluk Akcam's analysis), though most seem to agree that NGC 2244 refers to the Open Cluster of stars in the center of the nebula, and NGC 2246 et. al. refer to the nebula itself.

The Rosette Nebula is extremely faint, so I upped the individual exposures (8min) and cranked the ISO (1600) in order to better resolve the nebula. Close inspection reveals that the faintest traces of nebulosity are still below the read-noise floor of the camera. The cost of these long exposures/high ISOs is, of course, a washout of the color in the brightest stars. A worthwhile tradeoff IMO.

A higher-resolution image is also available. North is up.