OAS Star Diagonal, January 2003

I hope the holidays were good for everyone; ours was great. We don’t have much going on for January except the meeting on the 9^th. We have been working on the star party schedule and other activities for the coming year; all the dates and activities should be included in the February newsletter. For those that need to do advance planning, the Monte Christo star parties will be July 25, 26 and August 22, 23 and the Lowell Observatory trip will be September 8, 9, 10.

Patrick Wiggins, our NASA Ambassador announced that on February 1^stearly morning, there might be a chance to view a shuttle reentry crossing over southern Utah. To see it we will need to travel south to about Beaver. We will discuss it at the January meeting; anyone interested can contact David Dunn or me.

I know of at least 4 of us that have reservations at Dead Horse Point State Park for the April 4,5 star party. As of now, there are no sites available at Dead Horse. The Park does allow extra vehicles and up to 8 people per site so we should have room for a few more people. Anyone wanting to go that doesn't have reservations can contact me and we will find a place for you.

Several OAS members will attempt to view the Geminids on Saturday morning, 14 December at Trapper’s Loop, weather permitting.

Several exchanged comments on observations of the Leonids and plans to view the Gemenids on Saturday, weather permitting.

The Beginner’s Astro Class held on 6 Dec 02 was discussed. Cliff Peterson gave a presentation on telescope lore to about 12 guests - a pretty good showing for a first try and (ahem) about 11 more than SLAS pulled for a similar event. A name of “Astronomy Workshop” seems to fit the event, but it will evolve to suit the needs of the public.

Several of the events planned for 2003 were discussed, see The President’s Message. The Grand Canyon star party is set for 21 - 28 June 03.

Dave Dunn brought a supply of Brent Watson’s books for sale, even though Brent couldn’t make it himself.

Wayne Sumner volunteered to collect subscriptions to Guy Ottwell’s Astronomical Calendar 2003; enough joined in to get the “5 or more” rate.

A plea for help from a frustrated LX200 owner was met by soothing comments along the line of “they all do that” from some of the old Meade hands present, along with offers for more substantial assistance.

Lee then introduced the night’s program, a DVD featuring the Apollo 11 mission provided by Dale Hooper.

The January OAS meeting will be held at the Ott Planetaruim on the 10^th starting at 7:30 PM. Jim Seargeant will present a description of CCD image processing using M57 as an example. See Images, below.

How many would be interested in receiving the Star Diagonal by e-mail? It would save on copying and postage if we could e-mail to some of our members. It appears that distribution in PDF would work. Let me know if any of you are willing and I’ll try to set it up.

A member’s list is included in this newsletter. It should be scrubbed down to show only current members. Please check to see if your information is correct and if I’ve missed anyone.

One of the very first deep sky images that I learned to find (and back in the Dark Ages, the term GoTo was unknown, let me assure you) was the beautiful Ring Nebula in Lyra - M57. With my Meade 10" LX5, I often had trouble juggling bifocals, finder scopes, star charts, and eyepieces to find the dim fuzzies, but I could always locate M57 quickly, bracketed as it is by Sulafat and Sheliak, gamma and beta Lyr.

So when I started CCD imaging, the Ring is one of the first objects I tried, and tried again with the color filter wheel. I was surprised to see the level of detail that could be picked up with exposures of even moderate length.

I eventually upgraded my SBIG ST-7 CCD camera to Kodak’s KAF-0401E imaging chip with improved sensitivity to light in the blue end of the visual spectrum. This graph [click on it for a larger image] from SBIG’s web site shows the relative quantum efficiencies (QE) of the older Kodak chip and the blue-enhanced version. The old chip was nearly blind to blue; the “E” chip offers QEs of 30 to almost 50 percent in the 400 to 500 nanometer wavelengths transmitted by the blue filter. The result is greater overall sensitivity (shorter exposure times) with no filter and much greater sensitivity (much shorter exposure times) when shooting through the blue filter.

With the new chip installed and the Summer Triangle overhead, I returned to the old favorite, M57, determined to get the best image I possibly could of this object. I set up my 12" LX200 to shoot at f/10 and, attached the camera/filter wheel/AO7 directly to the OTA to get the most ridged mounting possible, collimated the telescope carefully, and waited for a good night. Well, the clouds and work schedule care little for the urge to image and it was September before I could get a series of shots - and then it wasn’t until a business trip left me sitting at the airport for a couple of hours that I was able to process the images.

In processing CCD, or any other digital images, there are all sorts of tools that can be applied to “enhance” the result. The trouble is, these tools can often add things to the images that aren’t supposed to be there. If, for instance, stars appear very sharp-edged with dark haloes around them, then the enhancements were applied with too heavy a hand. When I arrived at this image, I was concerned that I had overdone the sharpening, deconvolutions, and other tools that Mira and AIP provide. Nothing I could find after a quick search for M57 on the internet matched my image very well. Then I tried the Astronomy Picture of the Day (APOD), searched for M57, and found a Hubble image that showed that I had come pretty close after all. I rotated, cropped, and resampled my image to match and this is the result.

Now comparison between any image that I can take and Hubble’s verges on silly; just look at how finely Hubble resolves the stars! The seeing from Ogden wasn’t really all that good at about 2.8 arcsec full width half max. Seeing is a term that probably doesn’t apply at all to the Hubble. And of course, aperture will always tell. What is interesting here is that some of the really fine detail, for instance around the central star, comes through pretty well.

M57: The Ring Nebula

Credit: H. Bond et al., Hubble Heritage

Team (STScI /AURA), NASA

Don’t judge by these printed pictures. See http://antwrp.gsfc.nasa.gov/apod/ap010729.html for this Hubble image and APOD’s writeup on M57.

See http://physics.weber.edu/oas/oas.html for color versions of both images with this newsletter.