Michael Purcell's Astrophotography

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Centaurus A
(NGC5128, Caldwell 77)

Centaurus A

(Click on the picture above to go to the main image.)

A Tale of Two Images

This is my second image of Centaurus A taken at Grove Creek Observatory. The notes for the image from my first visit to GCO are below. Whereas the first image was a combination of two images, this most recent image was a single 20 minute exposure using the more sensitive ST-7E. It was good enough such that I did not need to perform any extra processing to sharpen the image. The master dark frame was a combination of three separate dark frames. The master flat frame was built from 10 separate flats.

For comparison purposes I have included both full images.

Centaurus A is a giant galaxy with three times the stellar population of our Milky Way (itself a very large galaxy). While possessing the size and shape of a giant elliptical galaxy, it also has dust lanes and blue stars more typical of a spiral galaxy. In addition to being very bright optically, it is also an extremely powerful emitter of radio and X rays. It has been proposed that we are seeing the merger of two galaxies: one elliptical, and one spiral. Very recent research I have read seems to support this.

This image is a replacement for my earlier ST-7 effort with this object. Given the high quality of GCO's C14 optics and mount, I decided to compare the effects of Track and Accumulate versus a single integrated image. Therefore, Steven Williams and I took two 10 minute images. The first was a single 10 minute exposure. It was guided using an ST-4 attached to a 3" refractor mounted on the C14. We then used the ST-7 Track and Accumulate feature to build a 10 minute image with 20 images of 30 seconds each.

Both images turned out reasonably well. Therefore I added them together to create this image.

This is a grayscale image with the Mira A/P "galaxy" palette applied.

I took this picture at Grove Creek Observatory.


Constellation Centaurus
Right Asc (hh:mm:ss) 13:25:30
Declination(deg:sec) -43:01
Magnitude 7
Size (ArcMin) 18x14
Tirion SkyAtlas 2000 #21
Uranometria 2000 #403

CCD Camera Parameters

ST-7E Compressed Image
File_version = 3
Data_version = 1
Exposure = 20 minutes
Focal_length = 98.000
Aperture = 141.3700
Response_factor = 2000.000
Note = Image taken 03/31/00 at 00:48:20
Background = 71
Range = 256
Height = 510
Width = 765
Date = 03/31/00
Time = 00:48:20
Exposure_state = 356
Temperature = -14.81 C
Number_exposures = 1
Each_exposure = 20 minutes
History = d
Observer = Michael Purcell at Grove Creek Observatory
X_pixel_size = 0.0090
Y_pixel_size = 0.0090
Pedestal = 0
E_gain = 2.30
User_1 = CCDOPS for DOS Version 3.84
User_2 = -
User_3 = -
User_4 = Y2KYear = 2000
Filter = None
Readout_mode = 0
Track_time = 100
Sat_level = 65535

This page last updated on May 20, 2001 Contact Michael Purcell

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