The Variable Star Section CCD Target List has been formed to encourage CCD observers to begin to contribute to specific projects of interest, and to provide a common set of targets as a focus for discussion, as we learn. The CCD list will be updated at intervals to reflect the interests of section members, and to take account of feedback received during this initial period. The projects have been deliberately divided to fall into four categories, described below, of increasing difficulty. It is suggested that new observers might wish to begin work on projects in the Basic CCD Data category, and progress to the subsequent levels as they become confident in each level. Note that the VS section has a CCD advisor (see Officer list), who is happy to assist with queries.

Projects in this category are designed for CCD observers who want to use their CCD cameras to do useful work, but who are not ready to use filters, or to do transformations to convert their magnitudes to a standard system. This means that projects in this category are aimed primarily at the detection of magnitude changes from one night to another, and to alert other observers.

For projects listed in this category, the emphasis is on obtaining measurements with accurate recording of the time at which the measurement was made. Projects in this category will usually involve taking a continuous series of measurements of one object, that might be expected to show changes during the period of observation. It would also be good practice, and useful in the analysis of the data, if an estimation of the error on the time can be made. No filter is required for these projects.

This category of projects is for those CCD observers who are able to use an appropriate V filter which, when combined with their CCD camera response, puts the derived magnitudes approximately on the standard Kron-Cousins system, without transformations being necessary. Potential observers who would like advice on filter/CCD camera combinations should contact the section CCD advisor. Data from this category, can be combined with that of other observers to build up a useful set of data for analysis. It would be good practice to attempt to estimate the errors of the magnitude and time measurement.

This category of work is aimed at the experienced CCD observer who is not only happy to use a filter, but who is also confident at applying the correct transformations to his reduced magnitudes, in order to precisely transform those magnitudes to that of the standard Kron-Cousins system. It would be good practice to include error bars on all measured quantities.

All Sky Photometry

No projects have been suggested for this category yet, as all-sky photometry is the most challenging to do, and it is uncertain how many observers will be interested in pursuing photometry at this level. Projects can be developed if there is sufficient interest in a future version of the list.

Comparison star sequences suitable for CCD photometry, will be provided by the Variable Star Section for all of these projects, and will be placed on the VS web page for easy access, together with more information about these projects.

It is hoped that the data that is obtained from these projects will help the VS in its formation of a CCD database, but the formation of such a database needs great care and consultation, and will necessarily take some time. In the first instance, please inform the Director, Roger Pickard, of the acquisition of data, in order that a log may be kept of data taken. The data will be requested from the observer in the required format, as the database becomes available for the receipt of data. Additionally, any comments, suggestions or ideas regarding the new CCD database, should be passed on to the Director, for discussion at the next CCD Database Working Party meeting, the minutes of which will also be placed on the web pages, and published in the circulars, in order that all interested members may be kept informed of the development process and may contribute.

If any observer requires any further information after consulting the web pages, or has any feedback, please contact the Director, Roger Pickard.

V1363Cyg
This star is classed as a UGZ star, but there have been only two positive detections in 10 years; one of these was at 15.9mv in 1996, and one at 14.8 in 2002. It might be the case that the UGZ classification could be in error, and this star could possibly be of VY Scl type (anti-dwarf novae) that spend most of their time in a high state, periodically dropping into a low state, during which time there is very little dwarf nova activity). The aim is to detect V1363 Cyg at minimum, and to detect any rise in brightness over short or long time scales.  If it is a VY Scl star, then the current low state may end at some point. If it does show outbursts we can learn how frequent they are, and what amplitude the outbursts are.

Only one outburst of this suspected UGSS class CV has been detected (in 1996 at 13.6mv).  CCD observations might reveal fainter and more frequent outbursts.

We have no positive observations of this possible UG system at all, in the database!  The aim is to monitor outbursts to reveal their approximate amplitude cycle (an <82d cycle has been suggested in IBVS 5124).

V650Ori
There are no recorded outbursts of this possible UG object which is extremely poorly studied.  There has been only one possible CCD observation (in early 1996 at magnitude 18-VSNET).  The aim of this project is to try to image the variable at minimum and to check for faint outbursts outside of the range of visual observers i.e. <16.0.

This eclipsing dwarf nova system has an estimated orbital period of 3 hours, but this is only approximate, and needs refining by taking measurements at around a rate of one frame per minute over periods of 3 hours or more. The key issue here, is the detection of possible superhumps and/or eclipse dips. A check star trace should be taken and reduced along with ES Dra.

These two eclipsing dwarf novae systems have unknown orbital periods and are under-observed! They present a good opportunity for careful work, which should be of the same specification as for ES Dra, but as the orbital period is unknown, the runs should be for as long as possible; it is also worth looking to see if there might be superhumps, the signature of an SU UMa type system.

This ZCam type CV needs to be examined for the existence of eclipses. Its orbital period is known to be 6.252 hours, therefore long observing runs are required on this object.

Chris Jone’s observations of this Mike Collins star, suggest that this is a Mira. However, during the 2000 apparition it faded from mag 11.7 to mag 15 in 87 days, and during the 2001 apparition it faded from 11.5 to 13.5, in more than 120 days. So are these two data sets in conflict, or is there some other answer? From good CCD images we should be able to determine what the rate of decline of this star really is, and find the minimum magnitude.

This project requires good time resolution with photometry of very faint stars – not for the faint-hearted! There has been some speculation that eclipse time ephemerides may vary over a period of time. Eclipse ephemerides have been examined for variation over a time period, using occasional measurements from large professional telescopes, but there has been no long term systematic monitoring of these times; this is therefore an ideal project for the more ambitious amateur. Who knows what this work may turn up!

Two eclipsing binaries, NSV4441Cnc (GO Cnc, mag 8.3-8.8) and NSV 4031 Lyn (8.0-8.8) have no ephemerides, and reduced photometry of these systems would enable them to be calculated. Images should be taken whenever observing conditions permit, together with the time at which the image was taken.

Scientists at Leicester University have constructed a theoretical model for an SS Cyg-type system, which predicts that the inner part of the accretion disc only, may sometimes go into outburst; there is a hint that this kind of behaviour may take place in visual observations, but in order to test the models, precision multicolour observations of SS Cyg, taken continuously through the night, over a number of nights (consecutive if possible) are requested. There is most interest in the results that are obtained using a U or a B filter (where the quantum efficiency of the CCD camera will allow), although observers with a filter wheel could take images sequentially through more than one filter, or observers could work together on the same nights, with one using a B filter, and one using a V filter.

Tim Bedding (Univerisity of Sydney, Australia) and Albert Zijlstra (UMIST, Manchester) have recently published their work, in which they use Hipparcos data for a number of Miras and semiregulars that have known periods, and parallaxes measured to better than 20%; they identify period-luminosity sequences for such stars. As distance indicators such stars are far more numerous than Cepheid variables, and the nearer stars have calibrated distances. An understanding of the P-L relationship also provides much information on how these stars pulsate and how they evolve. However, several of the Hipparcos stars that have good parallaxes still have unknown periods. CCD measurements of these stars, leading to an estimation of their periods would provide useful additional data to add to the sequence. The three stars selected below, are such stars. They are extremely bright, and the amplitude variations are very small and may be irregular, so they may need to be monitored for some considerable time. They would be ideal for a CCD camera with a camera lens attached, but the measurements must be made with a V filter, as these stars are very red, and it will be difficult to combine measurements from different systems otherwise. These present a challenge!

VZ Cam is around V magnitude 4.9, with a variation of < 0.2 magnitudes

CO UMa is around V magnitude 5.8, with a variation of > 0.2 magnitudes

AT Dra is around V magnitude 5.5, with a variation of > 0.2 magnitudes

GY Cnc is a deeply-eclipsing dwarf nova with the potential to reveal in detail how dwarf nova outbursts begin. Accurate, fast (1-4 frames per minute) V-filtered photometry of this system at the beginning of an outburst should aim to cover eclipses or even complete orbital periods of 4.21 hours. A bonus would be parallel V and R/I band measurements. Successful observations of the evolution of the eclipse profiles up to the outburst maximum would show whether outburst development is inside-out or outside-in; a key question for theoreticians modelling dwarf nova outbursts is whether this direction is correlated with the rise time of the outburst.