Galaxies

NGC2403 (Caldwell 7) Type: Mixed Spiral Galaxy (SABcd) Constellation: Camelopardalis

Nestled in a dark northern cave in the sky surrounded by Cassiopeia, Perseus, and Auriga, Camelopardalis (the giraffe) shares this cave with the two bears and a lynx (this cave is more like a zoo!). This constellation is all but hidden from naked eye detection for most observers in the currently light-polluted skies. It has no stars brighter than 4th magnitude, but spans 757 square degrees which makes it the 18th-largest constellation. Hidden in this faint constellation are several treasures including a faint, beautiful, spiral galaxy, IC 342 (Caldwell 5) which is obscured by the dust clouds of our own galaxy because it is only 11°above the plane of our galaxy. It also contains NGC1501, a nice planetary nebula with a central star, and NGC1502 which is a compact open star cluster.

However, my target of choice, ever since Karl Krasley mentioned it at the Chesmont winter sky targets talk this year, was NGC2403. This mixed spiral galaxy is 23.8’ by 12.8’ in size and has a surface brightness of magnitude 7.3. It is located near the nose of the Great Bear, Muscida. It is almost 8° away from this star in a direction almost parallel to the meridian. NGC2403 is located 14 million light-years away from Earth. It is a member of the Coma-Sculptor Cloud of galaxies. This gravitationally bound system also includes our local group and spans 90,000 light years of space.

Historically, this was first discovered in 1788 by William Herschel. Another contribution to the science of astronomy is that NGC2403 is the first system beyond our local group where Cepheids (variables whose periodicity has been an important tool for measuring extragalactic distances) were identified. When seen from Earth, the galaxy is inclined 28° from edge on. On first appearance the face of the galaxy seems to have clumps of starlight which could be misinterpreted as supernovae. Some of these are foreground stars, but other clumps of light were identified by Edwin Hubble during the 1950s using the Palomar Mountain 200-inch reflector as being over 100 H II regions lining the galaxies spiral arms. The largest of these has its own NGC denomination, NGC2404, and is locate 6’ north-northeast of the nucleus. It has an apparent diameter of 20” which means that it has a true diameter of 1,400 light-years!

When I decided to image this galaxy, it was the large number of H II star-forming regions that captured my interest. I decided right then that I wanted to use a Hydrogen-alpha exposure with my imaging to amplify the appearance of these regions. The only reference images I had were those done by much larger telescopes including an amazingly detailed image by Robert Gendler with his 20-inch RC from New Mexico. These were not challenges that I could easily meet with my 10 inch BRC-250 under suburban Philadelphia skies, not to mention that this was my first foray into any form of color imaging. Undaunted, ignorance is a wonderful thing (ignorance is bliss is the expression that comes to mind) so I tried to capture this galaxy. North on this image is located to the right and somewhat down. I hope that you enjoy this first effort into color imaging.

Technical Details:
The project began on December 5th and concluded on December 17, 2006 with the completion of processing. It was done over multiple nights due to the variable weather. The technical details are summarized below for those who are interested and the image is above.
Object: NGC2403 (Caldwell 7) Software: MaximDL Version 4.56
Location: Dark Horse Observatory, Kimberton, PA FocusMax
Telescope: Takahashi BRC-250 MiraPro
Camera: SBIG ST-10XME CCDStack
Other Equip: SBIG CFW-10 Filter Wheel Adobe Photoshop CS2
Flinger Lakes Instruments DF2 Focuser
Astrodon Filters
Mountain Instruments MI-250 Mount with Gemini L4
Exposures: All exposures were fully calibrated with bias, dark & flat field frames Color combine ratios were based upon G2V calibration on the night of color capture
Hydrogen alpha – 15 minute subexposures unbinned – # 28 – Time: 420 min. Clear IRB luminance – 6 minute subexposures unbinned – # 44 – Time: 264 minutes
Red - 5 minute subexposures binned 2x2 – #: 12 – Time: 60 minutes Green -5 minute subexposures binned 2x2 - #: 12 – Time: 60 minutes
Blue -5 minute subexposures binned 2x2 - #: 12 – Time: 60 minutes Total Exposure Time: 14.4 hours

Christopher J. Abissi 17 December 2006

M51 (NGC5194) and NGC5195

Constellation: Canes Venatici

RA: 13h 29.880m

Dec: +47 Degrees 12 Minutes

Distance: 15 million Ly

Magnitude: 8.4

Size: 11.2’ x 6.9’

Dates: 02 July 2007 to 04 August 2007

Location: The Dark Horse Observatory

Kimberton, PA

Luminance: 12 10-minute frames

Red: 09 10-minute frames

Green: 08 10-minute frames

Blue: 09 10-minute frames

Total: 380 minutes (6 1/3 hours)

Equipment:

Telescope: BRC-250

CCD: SBIG ST-10XME

Filterwheel: SBIG CFW-10

Filters: Astrodon Series E

Focuser: Finger Lakes Instrumentation DF2

Rotator: Optec Pyxis 2 inch Rotator

Mount: Mountain Instruments MI-250 with Gemini Level 4

Pier: Pier-Tech 3 Pier

Software:

Image Acquisition:

CDDAutopilot 3

Maxim DL

FocusMax

The Sky 6

Image Processing:

CCDStack

Adobe PhotoShop CS3

Russell Croman’s Gradient Xterminator

Noel Carboni’s PhotoShop Tools

Kodak GEM noise reduction Plug-in

Picture Code’s Noise Ninja

Name: IC 342 (UGC 2847)

Type: Galaxy – SABcd type

Constellation: Camelopardalis Exposure Time

RA: 03 hours 46.8 minutes Luminance: 10 min. (20) – 200 min.

Dec: +68 degrees 06 minutes Red: 10 min. (12) – 120 min.

Distance: 6.5 - 10 million light years Green: 10 min. (16) – 160 min.

Magnitude: 9.1 mag Blue: 10 min. (09) – 090 min.

Size: 21.4 x 20.9 arc minutes 15 min. (09) – 135 min.

Imaging Dates: 13 – 21 October 2007 Total Time: 11.75 hrs.

Location: Dark Horse Observatory

Kimberton, PA

Equipment:

Telescope: BRC-250 Mount: MI-250 (Gemini 1.04)

Focuser: FLI DF2 Rotator: Optec Pyxis (2”)

CCD: SBIG ST-10XME Filterwheel: SBIG CFW-10

Filters: Astrodon Series E

Software:

Acquisition: Processing:

MaximDL v 1.45 CCDStack: calibration & bloom removal

FocusMax MiraPro: image registration

The Sky 6 CCDStack: stacking and RGB combine

CCSAutoPilot3 PS CS3: Levels & curves

RC Gradient Xterminator

Kodak GEM noise reduction

Noel Carboni’s Photoshop Tools

Discussion:

I have been planning on imaging IC 342 for about one year since I first read about it. I knew that it would be a great challenge to my skills due to the dust clouds and the green and blue attenuation. I started gathering what I thought was sufficient exposure time and made an attempt to process it. Although the luminance was promising, the RGB result had almost no S:R ration in the blue channel and barely enough in the green channel. Then I saw several excellent versions (including Dan’s, Bob’s, Giovanni’s, and Jay’s) that were posted on the Yahoo groups. Each of these is different, but each was good. I was encouraged to go back and make another attempt to salvage my original attempt. I decided that I needed more color data especially in the blue channel so I went back this weekend to gather more color data. I decided to go for 15 minute subs in the blue channel to improve the S:N ratio. While the galaxy has come out much more blue I did not change the combine ratio from what I used for other objects.

Background:

IC 342 is a SABcd type galaxy located in the constellation Camelopardalis. It is approximately 21 arc minutes in apparent diameter and is faint at magnitude 9.1. The estimated distance has a wide degree of variation typically ranging from 6.5 to 10 million light years. It was first discovered by W.F. Denning in 1895 who first noted its core. However it was Edwin P Hubble and Milton L Humason who forst noted the spiral nature of this “nebula” in 1934 on plates taken from Mt. Wilson. IC 342 belongs to the Maffei I Group of galaxies, so named after the other major member of this group Maffei 1 which is so obscured by the galactic dust that it was only discovered in 1968. Because this group of galaxies lies only 11 degrees above the dust rim of our galaxy, there is a 3 magnitude attenuation of its brightness. As with objects low in the sky there is attenuation of all frequencies but less in the red portion of the spectrum. Hence this galaxy has a reddish appearance in most images.