OAS Executive Committee 

President- Dave Dunn

Ph. (801) 544-7705

Vice Pres- Lee Priest

Ph. (801) 479-5803

Secretary- Bob Tillotson

Ph. (801) 773-8106

Treasurer- Doug Say

(801) 731-7324

The regular meeting of the Ogden Astronomical Society will be held this Thursday October 12, 2000. Members will come together in the Ott Planetarium on the Weber State University campus at 7:30 p.m.

A Show-and-Tell activity is planned for this meeting. Members are urged to bring your recent projects, observations, photographs and the like. The upcoming star parties and Messier Marathons will be discussed as well.

New Executive Committee Elected

at the September "Annual" Meeting

At the September meeting, the attending membership cast their vote for club officers for 2000 - 2001. The results are:

President - Dave Dunn

Vice Pres. - Lee Priest

Secretary - Bob Tillotson

Treasurer - Doug Say

These officers are interested in hearing from you, the membership. You are encouraged to call, write or visit with the club officers and tell them what directions you would like to see the club go. What kind of meetings do you want? What activities do you like more, or less of? Your input is critical to the success of our association.

Saturday October 21, 2000 will be the club's last scheduled public star party on Antelope Island State Park. This final event will give members the opportunity to show the public the planets Jupiter and Saturn. These beautiful objects have been hard to reach due to their late rising but as the season progresses Jupiter and Saturn now rise early enough that we should be able to get a 'scope on them before most the people get cold and decide to leave. This star party is also scheduled near the peak of the Orionid Meteor shower.

Please try to have your equipment assembled before dark. Call your Executive Committee members if you have questions.

President's Corner

I want to thank everyone for showing their confidence in me and asking me to serve as president. I am looking forward to the fun meetings, star parties

and friendships that we will have this year.

We are planning some private star parties for this winter. I think that these will be a lot of fun and will help us get out of our warm houses and see some of the neat winter sky. We want to hold these close to home in an area that isn't too badly light polluted. If anyone wants to host one of these or knows of a good location, please let me know.

Also, remember that this is your club and if there is anything that you would like to do for our meetings or special star parties, let me know. I hope that we can have a lot of fun and learn together this year.

Dave Dunn

MINUTES

Ogden Astronomical Society

September 14, 2000

At 7:00 p.m. OAS members and visitors assembled around the Weber Sate University's observatory. Dr. Sohl assembled several telescopes, including Dr. Bob Neill's new Coronado H-alpha filter system. Everyone had the opportunity to view the solar prominences and faculae that can only be seen with this type of system.

At 7:40 p.m., the meeting was opened in the Ott Planetarium by club president Ron Vanderhule.

Ron raised the subject of the recent auroral displays that have been seen in our areas.

Ron then discussed the probability of a repeat Swap Meet to be held sometime in October. Various options for the 'Meet were discussed.

A Messier marathon will be planned for October 27 and 28. The location is still to be determined.

Several astro-items for sale were described.

Bob Tillotson is taking orders for Astronomy magazine's 2001 wall calendar. They are being offered for half price through the club.

Elections for the new club officers were conducted. Nominations from the floor were requested. None were offered.

John Sohl took the floor for the evening's meeting on solar filter systems, their function and the physics behind their function. It was a very interesting presentation which involved everyone present.

The meeting adjourned at 9:30 p.m.

Bob Tillotson, Secretary

As discussed at last month's meeting, an October Messier Marathon is set for Friday night and Saturday morning October 27 and 28, 2000. The location has been narrowed to the Golden Spike Monument or Lee Priest's property near Tremonton, Utah. The final decision will be announced at the October 12 meeting or contact Dave Dunn for more information.

Jim Seargeant's - Images
- M 57 -

This is the first color shot I've ever done.* Actually, two of Adam Johnston's WSU students, Shane Cheshire and Brenda McQueary, took the images on 15 Sep 00. They took with them a brief attempt at combining the images into a single color image, but this is a result of more careful processing. They should have this image by now.

There are two approaches to getting color with CCD cameras. Some cameras are capable of "one-shot" color; their imaging chips take red, green, and blue images together with one exposure. This is similar to the way many video cameras operate. Its simpler but resolution is lost. Other CCD cameras use imaging chips that take pictures only in black and white, so three separate pictures are taken, one each using red, green, and blue filters, and then combined. (Other color combinations are also used.) This is the sort of camera I have. As a variation on this approach, a high quality grayscale picture can first be taken, then simpler, lower quality images can be used to add the three color layers. The grayscale image is used in the "luminance" layer. (Again, alternative approaches are available.)

For this M57, five images were taken using the 12" Meade LX200 operating at f/10 and SBIG AO7, CFW8, and ST7. Two unfiltered images were taken at 60 sec, medium resolution. One shot each filtered by red, green, and blue were taken at 60, 90, and 160 sec respectively. Each of the images were calibrated using bias and dark frames. Flat frames were not available. The two grayscale images were aligned and median combined to form a reasonably high quality luminance layer. This image and each of the color shots were processed using maximum entropy deconvolution to improve resolution and bring out the fine detail within the ring. Each of the color frames were then aligned to the luminance layer and combined to from the final you see here.

I make no claims that this shows "true" color. The CCD chips are not equally sensitive across the visible spectrum and are quite sensitive in the infra-red. The first problem is handled by offsetting the exposure times as you see above, but those ratios are probably not optimum. An infra-red filter would deal with the sensitivity to that part of the spectrum, but I don't have one fitted just yet. So - the color may be pretty, but it's not the real thing. (If there is a "real thing" in astronomical colors.)

This image can be improved by taking many more images before combining them. I'd like to take at least 10 monochrome images to form the luminance layer and 5-10 images of each color. I'd also like to try it at f/20 using a barlow to increase the scale. It would also be interesting to see just how deep and exposure I could get. The shots that went into this image were limited in exposure by the bright field stars; any more exposure and the brightest would start to bloom. Using f/20 would exclude the brightest stars and any blooming of the nearby stars could be repaired in post processing. The objective is to see how much additional detail in the rings could be picked up.

Color is much more exacting and tedious than monochrome, but the results appear to be interesting.

The SEDS web site at www.seds.org has links to many more images of M57.

It also includes the following:

"The famous ring nebula M57 is often regarded as the prototype of a planetary nebula, and a showpiece in the northern hemisphere summer sky. Recent research has confirmed that it is, most probably, actually a ring (torus) of bright light-emitting material surrounding its central star, and not a spherical (or ellipsoidal) shell, thus coinciding with an early assumption by John Herschel. Viewed from this equatorial plane, it would thus more resemble the Dumbbell Nebula M27 or the Little Dumbbell Nebula M76 than its appearance we know from here: We happen to view it from near one pole.

This is contrary to the belief expressed e.g. in Kenneth Glyn Jones' book. There are even indications from investigations of deep observations such as George Jacoby's deep photos obtained at Kitt Peak National Observatory that the overall shape might be more that of a cylinder viewed along the direction of the axis than that of a ring, i.e., we are looking down a tunnel of gas ejected by a star at the end of its nuclear-burning life. Eventually, these observations have given evidence that the equatorial ring or cylinder has lobe-shaped extensions in polar directions, similar to those found in deep images of M76, but even more resembling other planetaries like NGC 6302 (see e.g. the review by Sun Kwok in Sky & Telescope for July 2000, p. 32).

The deep observations also show an extended halo of material extending off to over 3.5 arc minutes (Hynes gives 216 arc seconds), remainders of the star's earlier stellar winds. The halo was discovered by J.C. Duncan in 1937 (ApJ 86, 489).

Our color photo (taken with the 200-inch Hale telescope at Mt. Palomar) shows that the material of the Ring is exposing a decreasing ionization level with increasing distance from the 100,000 to 120,000 K hot central star. The innermost region appears dark as it emits merely UV radiation, while in the inner visible ring, greenish forbidden light of ionized oxygene and nitrogene dominates the color, and in the outer region, only the red light of hydrogene can be excited.

The central star was discovered by the German astronomer F. von Hahn in 1800, with a 20-foot FL reflector. This object is a planet-sized white dwarf star, which shines at about 15th magnitude. It is the remainder of a sunlike star, probably once of more mass than our sun, which has blown away its outer envelopes at the end of its Mira-like phase of evolution. Now over 100,000 K hot, it will soon start to cool down, shine as a white dwarf star for a while of several billions of years, and then eventually end as a cold Black Dwarf.

As for most planetary nebulae, the distance to the Ring Nebula M57 is not very well known. In case of this nebula, however, attempt was made to relate its angular expansion rate of roughly 1 arc second per century with its radial expansion velocity. These results, however, were based on wrong assumptions of the geometry of this nebula, presuming a spherical shape. So, a good value for the distance still needs to be determined (e.g., parallax by Hubble Space Telescope). Recent values were given at 4,100 ly (K.M. Cudworth 1974; Mallas/Kreimer), 1,410 ly (Kenneth Glyn Jones), 2,000 to 2,500 ly (Vehrenberg), 2,000 ly (Sky Catalogue 2000.0), "more than 2,000 ly" (Murdin/Allen's Catalogue of the Universe), 5,000 ly (Chartand/Wimmer's Skyguide), 3,000 ly (WIYN), 2,300 ly (STScI/Nasa Jan 1999), 1,000 to 2,000 ly (Sun Kwok, S&T 7/2000).

As most planetary nebulae, the Ring is much brighter visually at magnitude 8.8 than photographically at only 9.7 mag; a consequence of the fact that most light is emitted in very few particular spectral lines (see the discussion in our planetary nebulae page)."

Jim Seargeant, et al.

* Due to cost, The Star Diagonal regrets the photograph can only be reproduced in B&W. Visit the OAS web site for the color version of this incredible photograph.

Crossword Challenge

by Jeremy Mathews

"Elements"

As promised at the September meeting, Ron Vanderhule has arranged for another astronomy Swap Meet. The date has been set for Saturday October 14 but the location has not yet been decided upon. Watch your e-mail for updates and details will be available at the October 12 meeting.

The Star Diagonal is looking for an OAS member(s) willing to make a monthly contribution to the newsletter. We are looking for someone willing to prepare a "What's Up" column that would describe the skies for each month. Here is an opportunity for someone to contribute to our publication, become the club authority on things in the sky during the month and learn more about astronomy at the same time. This could be your chance to make a difference for the club.

You would need access to the Internet and must have e-mail for transmitting your work to the editor. The articles would have to be submitted in their completed form within a specific time frame. Graphics are always welcome and they add a great deal to the subjects and descriptions.

Contact Bob Tillotson at (801) 773-8106 or e-mail to:

bob@skyplanner.com

Editor

FOR SALE

SBIG ST7 CCD camera - $1950. Anti-blooming chip. Latest DOS based software (Runs fine under Win98.) 1 1/2" and 2" nosepieces. Cabling, power supply, instruction book, relay box for connecting to the telescope, everything needed to attach it and start taking pictures, plus all the coaching you can stand. Can be upgraded by SBIG to latest enhanced chip ST8E and two-stage cooling system for $300 less than the cost of a new ST8E.

SBIG CFW8 filter wheel - $500. Includes RGB filters mounted on the carousel, cables, instruction book, infrared filters, etc. Still more coaching.

Together, $2350.

Reason for selling, I got the two together in a package deal when I was trying to get the CFW8. Now I don't need the ST7 and I've decided I want to sell the CFW8 so that I can save up for either a bigger chip for my other ST7 or for a 2" OPTEC filter slider (many $ for either).

Contact Jim Seargeant at 801-479-4050 or JimSarge@aol.com.