Regulus! The M-31 Atlas

The M-31 Atlas

John A. Blackwell johnb@regulusastro.com:
Concept, images, text, design, and graphic labels.

G. Todd Miller glenn.miller@sun.com
Graphic Labels and design.

Paul Hodge
My sincerest thanks go to Paul Hodge for sending me copies of his original plates used to make his atlas of M-31.

The Atlas Key Chart

References

Introduction:

Note: This is a work in progress. Labels are still being added to the images.

CCD imagers offer a whole new world to amateur astronomers. There are so many projects that one can adopt that a lifetime could easily be spent just studying what a CCD can do! Recently, I decided to put the world of CCD imaging to the test. I have been doing the obligatory pretty- picture taking, doing CCD astrometry and photometry. I even dabble in spectroscopy. All of these projects were made possible by CCD technology. I just cannot imagine using film for all of this. Of course, this is just what astronomers had back in the early days: large telescopes with film cameras. I remember having seen the many images of the Andromeda Galaxy that Edwin Hubble had taken. He took plate after plate of photographs, using a 100" telescope. Some of these photos were taken over multiple nights! Imagine if he had access to a CCD imager! Thus was born this project.

The goal of this effort was originally to take many overlapping images of M-31 and generate a high resolution chart of the area. I thought that there was little scientific value to this, since my 212mm telescope cannot resolve individual Cepheid variables like a 100" telelscope can! In the end there will be an image large enough to make a poster: another high-tech pretty picture (grins). The data made available in chart form will allow amateurs to locate and identify various objects of interest in the M-31 galaxy, including globular clusters, open clusters, and nebular associations.

How it All Started: Night One

Night one started out without having this project in mind. The night was the 8-9th of September 2002. I set up the observatory to image a couple of asteroids and to image some deeper objects like the Veil and such. We had a spectacular aurora show that evening as well. When M-31 came up, I decided to take of shot of it... just to see. I centered its companion galaxy M-32 into the CCD frame and took a 5 minute integration. It looked pretty good, so I took another. Adding them together created a lovely shot with dust lanes and all. I noted that there is another section of the southern M-31 arms which has a cluster with nebulosity. This is NGC 206. Conveniently, an image of this would just overlap the image I just took of M-32. Ok - I took the image... two more 5 minute integrations. The results were clear: I was on my way to imaging the entire galaxy. The project was born.

The results of the first night's efforts. This is a mosaic of the two images of M-32, NGC 206 and the outer arms of M-31. Each was an addition of two 5 minute integrations. Select this image for the high resolution image.

Night Two

The second night of imaging came on 28-29 September 2002. The night was just calming down from a frontal passage. Autumn was in the air, and it was getting cold. The CCD was easily held to -15C throughout the evening. I finished off 6 more sections of the galaxy, each an addition of two five-minute integrations. At this point, the southern side of M-31 is complete, but more than half of the galaxy needed to be imaged before the Moon started interfered.

The results of the second night's efforts. This is a mosaic of thirteen images of M-31. Each was an addition of two 5 minute integrations. Select this image for the high resolution image.

Night Three

Night three was very satisfying. 66% of the galaxy had been imaged, and the mosaic grew to a stage where the file size has become difficult to manage without a strong computer!

The results of the third night's efforts. This is a mosaic of eight images of M-31. Each was an addition of two 5 minute integrations. Select this image for the high resolution image.

Completion:

The imaging side of the project had been completed before the end of the year. The rest of the project has only begun. Now, the images had to be processed and labeled in such a way as to be useful to the amateur. I chose to treat each image exactly the same. Each image had the appropriate dark frame subtracted, followed by a linear stretch. Images were then saved as jpegs for the web. Annotations were completed using a rather time-consuming technique which involved comparing the images against the Hodge's Atlas of the Andromeda Galaxy and using software to add the labels. A member of the local NH Astronomical Society, Todd Miller, volunteered to do a lot of the labeling activity and also helped with design and presentation of the atlas. Strict rules were followed such that only 100% verifiable objects were labeled. Anything that was questionable was marked with a question-mark (?) and either identified later or not labeled at all. The images were then reduced astrometrically using Canopus software, a popular software for the measurement of asteroid positions. It can also be used to do plate measurements which proved very helpful. The images were then marked with RA and Dec tick marks to assist in their use.

Future Plans:

In the future, the original FITS files will be made available as a part of this atlas to allow others to make astrometric and/or photometric use of them. Every effort has been made to insure the data's integrity and usefulness.

Instrumentation:

The instrumentation used to take these images includes:

Takahashi CN-212 Reflecting Telescope in Newtonian Mode with field flattener.
SBIG ST-7 non-E non-ABG CCD imager.
SBIG CFW-8 Filter Wheel with V-photometric filter.
Losmandy G-11 mount with Gemini GOTO.
A laptop computer for CCD and mount control.
The Northwood Ridge Observatory.

All equipment was left permanently attached and unmoved throughout the duration of the project so as not to disturb the rotational settings of the imager. North is as close to "up" on each plate as possible.