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AAVSO ALERT NOTICE 341  (September 4, 2006)


The AAVSO/CWST NGC 6811 Deep and Wide Field Campaign has begun. The Case-Western Schmidt Telescope (CWST) at Kitt Peak began observing the field on the evening of Sep. 1, 2006. This campaign is being coordinated with Dr. Steve Howell (NOAO). Background information and the scientific justification is available in AAVSO Alert Notice #339 located at this URL:

The CWST field of view is centered on the following coordinates:
RA: 19:37:17 Decl. +46:23:18 (J2000) The field dimensions are 1.5 degrees East-West and 0.75 degrees North-South.

Every night for the next 30-40 nights they will be observing the entire field as long as possible. They will take a single frame in B and V and the rest of their observations will be using a Sloan R filter. They will saturate around magnitude 13.

AAVSO CCD observers are asked to observe any portion of the field every night, for as long as possible, using a Cousins R filter. If you do not own a R filter then use V. We need 1% precision for all the stars in the field from magnitude 9-13. So set your integration time such that it won't saturate on the magnitude 9 stars. During data reduction, those frames can be stacked later to achieve the needed precision for the fainter stars in the field.

In addition, there may be times when CWST is clouded out and we ask observers to observe the fainter (>13 mag) end to compensate. Stay tuned to the AAVSO-Photometry Discussion Group for such announcements.

Use the AAVSO Automated Chart Plotter (ACP - currently in beta testing) to plot charts for the field. It is available at the following URL:

Comparison star values in B and V are currently available. The Sonoita Research Observatory will be used to calibrate the field as soon as weather conditions permit. When calibrated, we will add additional comparison stars to the charts - including stars with Rc band measurements.

** International Observers Needed! **

We could also use observations of the field while CWST (in Arizona) is in daylight. If you can observe anywhere within the 12:00-02:00 UT window then please observe in Rc and focus on the *faint* end, magnitudes 13-18. Your data may fill in the CWST's gaps. In addition, try to get a single R band snapshot each night in the mag 9-13 range for use with the brighter AAVSO datasets.

Since the CWST field of view is likely larger than any of our observers' fields, coordination of observing fields would make this campaign more efficient. Therefore, before you begin observing for the evening we ask that you post a message to the aavso-photometry discussion group telling us the center of your field of view (J2000) and your field of view dimensions. Feel free to use this example as a template:

FOV Center: 19:37:50.6 +46:35:23.1
North-South Dimensions: 15'
East-West Dimensions: 21'
Start Time: 05:00 UT
Estimated Stop Time: 08:30 UT
Filter: R
Target Magnitudes: 12-13

When possible, plan your field of view to slightly overlap someone else's. That way you can act as a systematic check on each other throughout the observing run.

If you are not a member of the AAVSO-Photometry Discussion Group feel free to send your plan to and Aaron will post them on your behalf. However, realize this may cause a significant delay in their posting.

The AAVSO IRC Chat Room is open throughout the campaign. Feel free to stop by and coordinate with other observers (and also to pass the time during these long runs!). Login info is here:

This campaign will generate an immense amount of data. In order to handle it we will need some special data reduction and submission procedures.

1. KEEP YOUR FITS IMAGES & PACE YOURSELF. It is entirely possible that data will have to be reduced multiple times. This is an open cluster in Cygnus, thus is a very crowded field. Also, a campaign of this length and magnitude has not been attempted by the AAVSO before. As a result, expect some errors. The nice thing about this campaign is that speed is not important - accuracy is. So don't cut corners to save time.

2. SEND THE AAVSO YOUR FITS FILES. Send the AAVSO CDROMs or DVDROMs consisting of your dark and flat frame calibrated FITS images. We will make these available to Steve Howell and his colleagues. Send the media to:

NGC 6811 Campaign AAVSO 25 Birch St Cambridge MA 02138

International observers and those who cannot mail media to us can contact to setup a mechanism for uploading your FITS images to the AAVSO FTP server.

3. SUBMIT DATA ON AAVSO PROGRAM STARS. If a star has an AAVSO designation, we request that you reduce and submit data on them using the traditional AAVSO channels. A list of such stars is available on the NGC 6811 Campaign web page. Please upload data on these stars through E-mail or WebObs so they may be placed in the AAVSO International Database.

4. SUBMIT STAR LISTS (if possible). Some of you have access to software that can generate photometry files that include RA, Decl., and photometry on every star in the frame. This is the preferred way of submitting data to Steve Howell and his colleagues. If you can make such a list, please upload them to our FTP server:

Host: Username: REMOVED Password:

Put your observer code in the starlist filename. (Ex: PAH1.txt,PAH2.txt...).

This program will be coordinated through the AAVSO-Photometry Discussion Group. Please post questions there as other people will likely have the same questions as you. In addition, a web page for the campaign has been setup at the following URL.

Additional information is available there, including links to the AAVSO-Photometry Discussion Group archives (so you can read it without subscribing).

This is a new and challenging campaign for all of us. But the science rewards and amount of data obtained may be unparalleled. In addition, this likely will be the prototype for many similar campaigns in the future as other sky surveys go online. So it is a wonderful learning opportunity as well. Remember to enjoy yourself. And, above all, don't let the weight of immense data reduction overwhelm you. The important thing right now are getting the observations. Data reduction can be done at a leisurely pace.

Again, make sure that you're having fun!

This campaign is being coordinated by: A. Price

This Alert Notice was prepared by: A. Price


Information on submitting observations to the AAVSO may be found at:

If you cannot access this URL, please contact us for submission details. You may also use our charge-free number (888-802-STAR = 888-802-7827) or our fax (617-354-0665) to report your observations.


An Alert Notice archive is available at the following URL:

Subscribing and Unsubscribing may be done at the following URL:

AAVSO 49 Bay State Rd. Cambridge, MA 02138 617-354-0484