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CCD Views #330

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C C D V I E W S #330
February 7, 2005

Table of Contents

1. Introduction
2. Address from the New AAVSO Director, Arne Henden
3. VV Pup Mini Campaign In Support for Keck Observations
4. CCD Timing Recommendations and Pitfalls
5. The Recent BZ UMa Outburst Campaign
6. High Precision Photometry Workshop at AAVSO Spring Meeting
7. Infrared Filter Grants Available
8. New Scintillation and Airmass Calculators on AAVSO Web Site


In the last few months our CCD program has been very active. Campaigns have been run on CVs, blazars and exoplanet transit objects. In fact, we've had so many campaigns that we created a web page to keep track of it all: . The page includes a timeline of all our active campaigns along with those in the recent past and upcoming campaigns. When planning the next few days of observation we recommend stopping by that page for new projects.

We opened the AAVSO Chat Room during the BZ UMa campaign to test its usefulness as a coordination mechanism. It seemed to be very popular with people logged in almost all the time during the entire week of the outburst. While the chat room is open to the public every Thursday, we plan to open it for longer periods during future campaigns.

The AAVSO Photometry Discussion Group has also been active with discussion about other types of campaigns and how often we should run them. The response I gathered from the discussion was: Bring it on! It seemed that the only limiting factor in observing activity is weather. So be careful what you ask for, you just may get it. :) Stay tuned for a very exciting and eventful 2005! And it doesn't hurt that we now have one of the world's best photometrists ON STAFF! (see below)
Clear skies,


Obviously, I come from a technical background and welcome the rapid increase in quality of both telescopes and CCD cameras in the commercial world. The US$1000 barrier for CCD cameras has been broken by several vendors, CMOS cameras are just around the bend, and I forsee the day when cameras are given away like eyepieces with every telescope purchase. We see amateurs obtaining millimag precision; others imaging GRB afterglows at 21st magnitude. I think one of the roles of the AAVSO will be to provide instruction, through tutorials and workshops, so that amateurs and professionals alike can learn how to obtain scientifically usable data.

We will always have visual observers in the AAVSO - they are the life and blood of the organization. The century-long timeseries on Miras and other variables, the dense coverage on CV outbursts, are all suited to visual studies. CCD observers expand on this base and attack other problems - very low amplitude variables, targets where color information is important, high time resolution, etc. Our goal in the AAVSO should be to support all observers, no matter what technique they use to obtain their data, in such a way as to get the highest possible precision and maximal scientific content.

CCD observing is still in its amateur infancy. We will be running more pro-am campaigns to show both professionals and amateurs what can be done with this photometric technique, and will pursue new directions such as whole-earth 24-hour campaigns, exoplanet transits, quiescent studies of cataclysmic variables and ground-based support for high-energy space missions. It is going to be a fun future!

- Dr. Arne Henden

Dr. Steve Howell, WIYN Observatory & NOAO, has requested observations of the polar VV Pup to coincide with observations being done at the Keck Observatory on February 16, 2005 (UT). Time series observations for as long as possible in BVRI are requested from 00:00 UT February 15 - 23:00 UT February 17, 2005. VV Pup is quite faint and also near the quarter Moon during the observing window. So we recommend the following observing plan:

1) Observe it in one filter instead of alternating between filters. Set your exposure time to get an SNR > 20. You may need to stack images to reach this SNR.

2) Small and moderately sized telescopes should observe in Ic first and in Rc if you don't have an Ic filter or someone else is currently observing in Ic. This will lessen some of the effects of the Moon and also lower exposure time (this is a field with heavy extinction). Those with larger apertures should go for V and B photometry.

3) Post to the aavso-photometry discussion group and tell us what filter you are using and the expected start and end time of your observation run. This way someone else can use a different filter if they are observing at the same time.

We currently have very few observations of VV Pup. So baseline observations prior to and immediately after the observing campaign would be very useful.

The AAVSO Chat Room will be open for this event! Join us during the campaign at .

The VV Pup chart is here: [link removed - please use our Variable Star Plotter to create an updated chart]

Our observations of VV Pup are minuscule!! We desperately need some photometry. Our latest observations of VV Pup:
VV PUP JAN 01.4960 <15.3 SRX Visual
VV PUP DEC 31.8280 17.2 CCD MLF Unfiltered
VV PUP DEC 28.4424 16.305 CCDI CTX ERR: .03
VV PUP DEC 23.4785 18.38 CCDV CTX ERR: .027
SRX - Rod Stubbing, Australia
CTX - Tim Crawford, Oregon, USA
MLF - Berto Monard, South Africa

There are two main sources of error when it comes to CCD image timing. The first source is the accuracy of your computer clock. We recommend that you sync your clock with either WWV via a short wave radio or use one of the US Naval Observatory's NTP Internet servers:
Many deluxe GPS systems can now be purchased with an interface to your computer which will update your system clock with the GPS signal.

Regardless of the system you use, please update your clock before *each* observing run.

Another source of error is in unknown recording of the time into the FITS header by your camera control software, especially when stacking images. It has been reported that some software records the time of the first image, the last image, an average of the images, etc. What should be reported to the AAVSO is the midpoint of the observation.

At the URL below I have put online 4 FITS images. [Link removed] Please download the four images and stack them in your software. Post to the AAVSO Photometry Discussion Group (or e-mail me if not subscribed) the time that your software recorded in the final image.
Send us:
1. Software Name
2. Software Version (usually found in the "About" menu)
3. Time listed in the FITS header of the stacked image.

In the next issue of CCD Views I'll post a list of the various software packages and how they handle the timing of stacked images. We will use that to recommend ways to compensate for the peculiarities of various photometry packages.

BZ UMa went into outburst again on January 16, 2005. The AAVSO commenced a high intensity observing campaign for the duration of this short outburst (~5 days). AAVSO observers did a fantastic job building a solid light curve with complete coverage for almost 24 hours when the outburst peaked. The light curve, data and notes on the outburst can be found here: [link removed]

This outburst follows on a campaign the AAVSO conducted on a BZ UMa outburst in February, 2004 which resulted in an IBVS publication. A subsequent quiescence campaign was conducted in April with inconclusive results. We hope the addition of this new, large and high quality data set will help shed light on this enigmatic system, which is yet to be classified. We will be working with the data in the coming weeks and will post updates to the aavso-photometry discussion group. So far superhumps are still missing but some interesting features in the decline may give us a few clues.

Arne will be holding a high precision photometry workshop at the upcoming 3rd High Energy Astrophysics Workshop for Amateur Astronomers being held alongside the AAVSO 94th Spring Meeting. The goal of this workshop is to follow up on previous workshops at AAVSO meetings with a more advanced program focusing on high precision photometry of faint objects. The additional training is important as we expand into fainter categories of stars (blazars, quiescent CV photometry) and stars that need ultra high precision photometry (exoplanet transits).

Also, during the AAVSO paper session an introduction to IRAF will be presented which we hope will lay the groundwork for an IRAF workshop at the AAVSO Annual Meeting in October. A limited number of travel grants are available for meeting attendees. Visit the following URL to apply: [link removed]

P/S: Arne and Brian Warner will be giving a workshop about using Canopus software for photometry on May 24, 2005 in Big Bear, CA. This workshop is not affiliated at all with the AAVSO but many AAVSO observers do use Canopus. For more info visit: [link removed]

The AAVSO has received a generous grant from the Curry Foundation to purchase CCD filters for use by members of the AAVSO International High Energy Network. We have 15 Iz (SDSS z') and 10 Ic filters available for semi-permanent loan.

The Iz filters are intended for use in GRB afterglow hunting. The Ic filters are intended for use in monitoring blazars for the High Energy Network but can also be used for other variable star projects. If you would like to receive one of these filters please fill out the application at the URL below. [link removed]

We have put online a tool to automatically do airmass and scintillation calculations for you. It can be accessed at this URL: [link removed]
The results page will give you the airmass of an object and (optionally) the scintillation. The computation is a rough approximation but should be good enough for most photometry calculations. A table of projected airmass and scintillation for the next ten hours is also displayed. The algorithms used for both approximations are referenced at the bottom of the results page.


An archive of "CCD Views" is available at

An archive of "Eyepiece Views", a similar newsletter intended for visual observers, is available at

The AAVSO has many free online publications. To learn more and subscribe visit:

Good observing!
Aaron Price, AAVSO Technical Assistant (PAH)
Gary Walker, Chairman of the AAVSO CCD Committee (WGR)
Copyright 2005, American Association of Variable Star Observers

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