This web page is meant to help new observers conduct observations of exoplanet systems. However, it is already superceded by my book Exoplanet Observing for Amateurs, which should be available for purchase in the Fall, 2007. Since this web page does cover some of the basics it may have value for beginning exoplanet observers and I will leave it up for now. Until the book is available for purchase you can preview some of the more advanced concepts at my other exoplanet observing tutorials, listed below:
          XO-3 observations (coming as soon as RA/Dec coordinates are in the public domain)
          XO-2 observations
          XO-1 observations
          Artificial Star Photometry
          Interpreting Transit Light Curve
          Transit Systematics (similar to what's in forthcoming book)   

Links internal to this web page:

    Overview for Observing Strategy
    Reference Stars
    Flat Frames
    Hardware Considerations
    Observing Procedure
    Data Reduction
    Dealing With Interfering Stars
    Data Analysis
    Non-Transit "Wander" Observations
    Example Results: TrES-1
    Miscellaneous Links


Exoplanet observing involves "differential photometry" of a star field for a series of closely-spaced images taken during many hours, and perhaps repeated for several nights. The objective is to measure the ratio of the exoplanet star's brightness relative to one or more "reference stars" (also referred to as "comp stars" by the AAVSO). The relative brightness of the exoplanet star is plotted as magnitude versus time (a light curve) with the hope that this plot will show a slight fade, such as 1.4% (HD209458) or 2.5% (TrES-1), during the expected time an orbiting planet transits in front of the star. The transit event may last ~2 hours.
It has been shown that telescopes as small as 4 inches can be used to detect such transit fades. I had no trouble detecting HD209458 in August, 2001 using a 10-inch Meade LX200 and SBIG ST-8E CCD camera. I now use a Celestron CGE-1400 (14-inch Schmidth-Cassegrain) and a USB-upgraded ST-8XE CCD. With the 10-inch Meade I was able to achieve 20-minute precision of ~3.4 milli-magnitude, whereas with the 14-inch Celestron I now can achieve 1 or 2 milli-magnitude precision for 5-minute averages. Since these precision values are much smaller than the predicted fade of 19 milli-magnitude (HD209458) and 25 milli-magnitude (TrES-1) it is definitely possible for an amateur with modest hardware to detect and even characterize the shape of exoplanet transits.

(For a quick peek at my TrES-1 transit light curves go to http://brucegary.net/TrES-1/x.htm  )

Overview of Exoplanet Observing Stragegy 

My philosophy for observing exoplanet transits can be summarized with the following two rules:

    1) have a good flat frame, and
    2) keep the star field at the same approximate location on the imaging chip for the entire observing session.

If Rule 2 could be observed perfectly, Rule 1 would not be necessary. Since you should assume that there will always be some drift of the star field, even at the level of a few pixels, it is prudent to observe Rule 1.

Conversely, if Rule 1 could be observed perfectly, Rule 2 would not be necessary. But since it is not humanly possible to obtain a perfect flat frame it is prudent to observe Rule 2.

The over-riding concept for these two rules is to maintain a constant observed ratio between the target star and all reference stars for the condition when the target and reference stars do not vary.

I suppose I should add Rule 3, which is to use a filter. This will minimize any extinction-related effects, due either to air mass changes or atmosphere changes. If all reference stars and the target star had the ssame color then this rule would not be necessary. But since all stars have different colors it is prudent to observe this Rule 3. 

Reference Stars

It's not necessary to strive for good absolute accuracy of an exoplanet transit if your goal is to detect the light curve using your own equipment. It's only when your measurements are to be combined with those by others that an attempt to achieve moderately good photometric accuracy is helpful. Here's an image showing three reference stars for exoplanet TrES-1 when an R-band filter is used.

 Photometric sequence

Figure 1. Example of stars suggested for use as reference stars when using an R-band filter for differential photometry of TrES-1.  FOV = 10.8 x 12.7 'arc, north up, east left.

Notice that for this exoplanet all refernce stars are about as bright as TrES-1. If only one reference star were used it would add ~40% additional "stochastic noise" to the brightness measurement of TrES-1 compared with the situation of using a much brighter reference star. Therefore, for this exoplanet it is important to make use of at least these three reference stars. This will reduce the stochastic component of TrES-1 brightness uncertainty to almost that which could be achieved by having a much brighter reference star.

So far there are only two exoplanets with known transits (that are observable by amateurs), and for each one there are calibrated reference stars nearby. If a future exoplanet is discovered that does not have suitably calibrated reference stars it will surely be supported by all-sky photometrists quickly, so lacking suitable reference stars is not likely to be a problem for amateur exoplanet observers.

Flat Frames

Flat frames is an art that every photometrist should attempt to master. I don't know if anyone is capable of mastering this art, but I'll give some tips.

My favorite flat frame trick is to use a "Double T-shirt Cover" that fits over the aperture and point to zenith at sunset for a series of flat frame exposures. The T-shirts allow long exposures without the nuisance of stars showing up. One T-shirt was inadequate, so I use two. The telescope's f-ratio will determine when exposures can be made. You want to keep the maximum counts for each flat frame within the linear region to avoid saturation effects. For my SBIG non-anti-blooming gate CCD (non-ABG) that means keeping the maximum counts below 40,000. To maintain good SNR for the fflat frames I keep adjusting exposure time as the sky darkens so that the maximum counts is above 25,000.

For my prime focus f/1.86 configuration I begin B-filter exposures 5 minutes after sunset and end 22 minutes after sunset. This is a  17-minute window, and it allows for exposures that range from 1 second to 20 seconds. (Avoid exposures shorter than ~1/2 second because the shutter can't open and close in a way that exposes all pixels for the same duration when exposure times are short; in other words, using a very short exposure time for a flat frame will introudce a false flat pattern unique to the mechancis of how the shutter opens and closes.) The V and R-filters have windows of similar length, and with start times that are slightly later than the B-filter start time. Therefore, if more than one filter is to be used (which it won't for exoplanet work) you would have to alternate flat frame exposures to accommodate all filters. Since an exoplanet observing session will employ just one filter, such as V or R, the flat frame session will be easier to perform than for other observing projects.

One more thing about flat frames deserves comment: "To dark, or not to dark." I always use darks, but biases should also be adequate. Sure, darks add noise to the difference image, but if long exposures (such as 20 seconds) are used for flat frames then the dark current levels begin to matter.

The prime focus configuration has one surprising payoff for exoplanet observing: prime focus flat frames don't have dust donuts! They are surprisingly smooth, which means that you can tolerate bigger errors in star field placement whenever a re-pointing has to be performed (when the autoguider loses its guide star). It also means that you can perform a smoothing to a flat frame image that is noisy and not lose structure that should be preserved. My prime focus flat frame has a "sweet spot" slightly off-center, with a response 5.3% down half way to one long axis edge and 1.5% down on the other side. The next figure illustrates the result of flat-frame calibrating a set of 3 even-numbered flat frames (exposure times ranging from 1.0 to 2.5 seconds) using for a flat frame correcing image four odd-numbered flat frames (exposure times ranging from 1.0 tp 4.0 seconds). For this set of images there was a residual flat frame error of -0.01% on the left side (half-way to the edge) and 0.06% (half-way to the right edge). This means that a refernce star at the two off-center locatiosn would cause errors for the target star at the center that were +0.0001 magnitude and -0.0006 magnitude (left and right sides, respectively). This is far better than necessary, from which I conclude that my flat frame procedures are adequate.

 Flat frame results

Figure 2. Result of flat-frame calibrating even-numbered flat frame images using odd-numbered flat frames for creating the flat from correction image (2004.10.08) showing excellent removal of vignetting effects that require several % flat frame corrections. The first frame shows where readings were taken.

Hardware/Software Considerations: Context for Remaining Tips

The remaining tips are somewhat hardware and software related. So let me state what I'm using and each observer can modify their procedures to fit the hardware and software to be used.

I have a Celestron 14-inch (CGE-1400) Schmidt-Cassegrain telescope. Given that for the IL Aqr observations require a large FOV in order to include several reference stars on the main chip I employ a prime focus configuration which many Celestrons are capable of (they call this feature Fastar). My prime focus transition lens (for coma reduction and flat fielding) is Starizona's HyperStar, which affords a fast f-ratio of 1.86. If you can't use a prime focus configuration then you may need to use a focal reducer lens to achieve a large FOV (i.e., larger than 8 x 12 'arc,.and preferably ~16 x 24 'arc).

My CCD camera is a SBIG ST-8XE (9-micron square pixel dimension) and I use a SBIG CFW-8 filter wheel with photometric filters. This configuration produces an image scale of 2.81 "arc/pixel and the FOV is 72x48 arc. Since the "atmospheric seeing" typically is 2.5 to 3.0 "arc (FWHM), the prime focus configuration point-spread function is much larger than the "seeing" limitation; my observed FWHM is ~7.5 "arc. The only time this FWHM changes is when I fail to update the focus setting (using plots of focus setting versus temperature, with lines plotted for each filter - since my photometric filters are not parfocal at prime focus).

The telescope is located in a sliding-roof shed 50 feet from my house, and it is controlled using 100-foot buried conduit cables from my house office (separate conduit for AC power and control cables). I use MaxIm DL 4.0 to control the telescope pointing, CCD camera, filter wheel and wireless focuser.

I change focus using a wireless product Starizona sells (called MicroTouch) that connects to the shaft of the mirror focus knob. The wireless device works fine for all telescope orientations, and it is supported by MaxIm DL.

For pointing I must use MaxPoint, a Cyanogen Ltd. product that is similar to TPoint (TPoint can't be used with MaxIm DL but MaxPoint was sritten by the MaxIm DL people so they work great together). MaxPoint overcomes the bugs that afflict some of Celestron's CGE-series mounts that render them incapable of reliable pointing). Since the darned CGE's have to be flipped when crossing the meridian I have MaxPoint coefficient files  for the eastern half of the sky and the western half of the sky. The appropriate MaxPoint coefficient file has to be loaded before observing begins.

Observing Procedure

A typical observing night starts with observing schedule planning before an early dinner. Tranist ingress and egress times dictate the start and end times. It is absolutely necessary to allow for a set of sky flat frames that begin at sunset and end 1/2 hour later (for my f-ratio). My use of a "Double T-shirt Cover" for zenith sunset exposures is described above.  All dark frame images (for each filter, if more than one filter was used) are then averaged. The CCD cooler is then set to a value that can be sustained (about -18 C at this time of the year at my site). During CCD cool down I check telescope pointing and verify focus on a star in the region of interest.

Observations of the exoplanet are preceded by another focus check and a star field position placement that provides a suitably bright star on the autoguider chip. The exoplanet is almost always placed at the center of the FOV since with the prime focus configuration the autoguider chip almost always has suitably bright stars present. My goal is to maintain this placement of the star field with respect to the main chip for the entire duration of the night's exoplanet observations. This is an important observing goal since errors in the flat field are an important source of systematic changes in exoplanet brightness. Exposure times for the exoplanet images are kept short enough so that none of the reference stars are saturated (maximum counts below 40,000). For TrES-1 and R-band this exposure time could be as high as 60 seconds for my system, but so far I have used only 30-second exposures.

When focus and pointing have been checked it's time to start the autoguider. I try to keep a post-it record on the monitor showing whether the last autoguider calibration was for one side of the meridian or the other. This is useful for German equatorial mount users since a meridian flip requires a "flip" box to be checked on the autoguider set-up menu when observing on the other side of the meridian from when calibration was done. Once the autoguider is running it's good practice to monitor the small autoguider image window for awhile to make sure the autoguiding is working right. Once autoguiding seems to be working I take a deep breath and start the long series of sequence observations. The hope is that the autoguider will not "get lost" and drive the telescope far away, which would require a time-wasting re-pointing procedure. If this happens, the main loss is time coverage, not target star magnitude offsets related to use of a slightly different part of the flat frame for reference and target star. I have shown that with my system in the prime focus configuration re-positionings that are 5% of the FOV different do not have any noticeable effect on the target star's magnitude solutions. This might not be the case for Cassegrain focus, where the flat field has more structure.

I use MaxIm DL's "sequence" observing feature to take many sets of 10 "light" images and one "dark" image. My focusing is not automated, so I monitor FWHM "on the fly" by quickly calibrating a sequence image while another is being exposed. If the FWHM trend convinces me that a focus adjustment is needed the sequence can be halted and a focus adjustment can be made manually. It's important to not waste time with elaborate focusing procedure while monitoring an exoplanet, so it's important to "know thy instrument" and ake good estiamtes of what focus adjsutment is likely to be needed (based on temperature).

I'm a firm believer in using an Observing Log with a ball-point pen. Obseving log notations should never be capable of erasure, as they may be invaluable when trying to reconstruct what happened at a later date when memopry has faded. All post-observation notations on the Observing Log should bemade in pencil. My OL is probably more meticulous than most observers are willing to do, but that's the  philosophy I developed from several decades of field observations in a related field before my retirement. For each observing sequence I note the UT start time, sequence number, filter, exposure time, whether there's autoguiding or not, focus setting, telescope tube temperature, outside ambient temperature, wind seepd and direction. During the sequence I note FWHM from "on the fly" readings of an unsaturated star while another exposure is in progress. Every telescope pointing change for re-centering is noted, as are the new indicated coordinates. At the end of the night's observing I note my subjective impressions of how well things went that night (whether goals were met, lessons learned, etc).

Data Reduction

My data reduction procedureis not automated, and I don't use a second computer with a LAN to perform reduction analyses during an observing session. Therefore, what I shall now describe may seem painfully "primitive."  The concepts of what I do are probably more sound than my procedure for implementing them, so bear with me.

I use MaxIm DL's Photometry Tool for photometric analysis of groups of images. I manually load 5 images at a time, calibrate them (flat field and dark), and save the median combined (or sigma-clip combine) image. I am very wary of cosmic ray effects creeping into light curve analyses, so I always use median combined (or sigma-clip combined) images for my photometric analyses. After several groups of 5 raw/calibrated images have been processed to produce "clean" images I perform a photometric solution for several clean images using the MaxIm DL Photometric Tool. The exoplanet "object" is chosen, and several "reference stars" are also chosen and their magnitudes are entered in to the Photometric Tool. The choice of signal aperture radius, gap width and sky reference annulus width are important, and for the prime focus configuration I usually use 5, 2 and 4 pixels. The stars typically have FHWM = 2.7 pixels, so use of 5 pixels for the aperture radius is "conservative" in the sense that for images when the FWHM is larger than for other images there will be minimal effect on the "intensity" reading. Occasionally a star field has interfering stars near a reference star and this requires a different choice for aperture/gap/sky reference. Here's a rule that should never be violated: Thou shalt not use different signal aperture size for different images! Absolutely all images of the exoplanet should be processed using the same signal aperture radius, gap annulus width and sky reference annulus width. The Photometric tool creates a CSV-file containing a Julian Day time tag and magnitudes for the object and reference stars.

There's a slight adjustment that is needed for the time tags when using MaxIm DL Photometry Tool to create CSV-files. The time tag does not correspond to the middle of all image exposures. I don't know why this is so (should be easy to program), but every user should determine if a time tag offset is needed. This is done by manually calculating mid-exposure time and comparing with the time tag in the CSV-file (or whatever file your image processing software createts).

These CSV-files are imported to an Excel spreadsheet and processed in a straightforward manner. Checks are usually performed to validate constancy of the reference stars with respect to each other, which is another way of using these stars for the role of "check stars." Outliers data is dealt with by referring to the observing log (as when I sometimes change focus setting during an exposure, a bad habit which I'll admit to trying). Any unexplained outlier is subjected to Pierce's Criterion (1876), which can be briefly summarized as "when a suspected outlier is X standard deviations away from where an average trace predicts it to be, where X is chosen to be appropriate to the number of observations, REJECT the data and repeat the search for more outliers." Instead of using an average trace you can use nearest neighbors to assess population SE and reject data using the same concept in Pierce's Criterion. I believe in averaging (after rejecting outliers), and there's an art to appropriate averaging - which isn't worth belaboring here.

Dealing With Interfering Stars

There's one problem with using *119 that everyone should be aware of. There's a faint star ~17 "arc to the NNE (pa = 327 degrees) of *119 (see figure, below). The faint star is 3.0 magnitudes fainter than *119 using a V-band filter. My photometry of *119 excluded the nearby faint star by employing a technique that would horrify most observers; I used a pixel editing feature to "remove" the faint star from the image (using a copy of the original for the horrific deed), then performed the photometry using that edited image. (I'm practised in this from my faint asteroid light curve work, where an asteroid is always going near faint stars during the course of an evenning's observing.) I didn't have the option of changing the "aperture radius/gap annulus width/sky reference annulus width" settings because doing that would render my equation predicted magnitude (described in the next paragraph) unusable for those changed settings. The way I recommend handling this faint interfering star for exoplanet monitoring is to set the signal aperture so that the faint star is entirely within or entirely outside the signal aperture (and not withni the sky reference annulus). The effect of completetly including the faint star within the signal aperture is to merely introduce a slight offset in the exoplanet magnitudes, and provided all images are reduced with the same aperture settings this will not cause changes in the exoplanet light curve.

 Nearby star

Figure 3. This is the preferred way to set aperture radius, gap width and sky reference annulus so that the neaerby interfering star does not affect the measured intensity of a reference star.  FOV = 6.0 x 5.8 'arc, north up, east left.

I suppose that I should mention that I employ a novel scheme for converting measured star intensity to magnitude (described at http://brucegary.net/AllSky/x.htm). It involves solving for coefficients in an equation that allows extinction and star color. In my opinion it is simpler and superior to the standard "CCD Transformation Equation" (derived and described in all its gory detail at http://reductionism.net.seanic.net/CCD_TE/cte.html). My all-sky procedure involves noting each reference star's "intensity" (having units of "counts") and entering them in a spreadsheet. When the user completes an iterative solution for two key coefficient values it is possible to convert any star's intensity to an "equation predicted magnitude." When this is done for the Landolt reference stars (of known true magnitude) it is possible to compute an RMS difference between equation predicted and true magnitude for the Landolt stars. This method of assessing RMS accuracy can be used to predict the accuracy of equation predicted magnitudes of any other star for which an intensity has been measured. Based on the RMS scatter of the 14 Landolt star magnitudes used for deriving the IL Aqr reference star magnitudes I conclude that the B- and V-magnitudes listed in the table above have an SE uncertainty of  0.033 and 0.022 magnitude. The B-V entries are therefore subject to an SE uncertainty of 0.040 magnitude.

Data Analysis

Data analysis is what you do after data reduction. That's where real thinking and real fun begins. For example, data analysis would include 1) deciding whether extinction that affected reference stars differently than the exoplanet star could have produced a trend versus air mass, 2) deciding whether it's appropriate to average one transit data set with another, and 3) modeling the effect of the transiting planet's size in an attempt to determine the star's limb darkening.

Non-Transit "Wander" Observations

To satisfy my curiosity about how big instrumental "wander" features can be for my system I observed TrES-1 for 3.4 hours on a non-transit night (2004.11.04) to see what level of variations would be observed using the same observing hardware configuration, observing technique and the same data reduction procedure that was used for the transit observations.  Here are those observations for TrES-1 and a nearby check star with approximately the same brightnesss.

 4B04 LC avg line
Figure 4. Measured R-magnitudes on a non-tranist night for TrES-1 (red) and a check star (green) using same hardware and procedures as during the transit nights.  Three stars served as reference ("comp").

 4B04 5-min trace

 Figure 5. Light curve plot of same data as in previous figure. A 5-minute running average is shown. The observations began with air mass = 1.10 and ended when airmass = 2.32. The RMS deviations from the running average increase with air mass from 3.07 to 3.84 milli-magnitude for the check star and they increase from 6.85 to 8.58 milli-magnitude for TrES-1.

TrES-1 exhibits an RMS variation about the 5-minute running average trace that is greater than for the check star. For example, at low air mass the two RMS values are 3.07 milli-magnitude (check star) and 6.85 milli-magnitude (TrES-1). The RMS fluctuations are in the ratio 2.22 instead of the expected 1.12 (based on brightness ratios). I don't understand this.

The 5-minute average trace for the check star exhibits a range of variation of ~6 milli-magnitude, whereas the range of variation for TrES-1 is about 10 milli-magnitude. Clearly, for my transit observations features similar to those in the above figure should not be believed. Specifically, a 5-minute feature with an amplitude of 2 milli-magnitude is too subtle for me to detect with one observing session (especially when TrES-1 is at a high air mass).

 4B04 5-min independent groups
 Figure 6. Light curve plot of same data as in previous two figures. 5-minute independent group averages are shown. The 5-minute group averages for the check star exhibit an RMS about their ensemble average of 0.88 milli-magnitude at low air mass to 1.56 milli-magnitude at high air mass. For TrES-1 the RMS deviations from the ensemble group average is 2.25 milli-magnitude at low air mass and 2.42 milli-magnitude at high air mass.

The check star 5-minute independent group average of 0.88 milli-magnitude at low air mass agrees well with the value expected from the 10-second individual image RMS of 3.07 milli-magnitude (0.89 milli-magnitude). The check star's high air mass RMS is slightly higher than the expected value, 1.56 versus 1.11 milli-magnitude. I interpret this to be evidence that high air mass observing conditions produce systematic errors that wander by amounts greater than the stochastic uncertainty (for my system). This appears evident in the check star's 4 milli-magnitude "fade feature" at about -575 to -555 minutes. TrES-1's 5-minute independent group averages undergo a greater fluctuation than the check star, as predicted from their greater RMS for individual 10-second images. The TrES-1 5-minute groups exhhibit approximately the expected RMS values for both low and high air mass, being 2.25 versus 2.00 milli-magnitude for low air mass and 2.42 versus 2.48 milli-magnitude for high air mass.

Using the 5-minute independent data groups it is possible to predict the level of features that can be expected to appear during a real transit event, assuming stochastic SE and systematic wander characteristics are the same both observing nights. TrES-1 and the check star tell the "same story": we should expect to see non-real 10-minute features with amplitudes ~2 milli-magnitude at low air mass and ~3 milli-magnitude at high air mass. Given the better stochastic behavior of the check star (than TrES-1) these systematic error wanderings will be more apparent for a star that is stochastically well-behaved (like the check star was). For a star with poorer stochastic behavior (like TrES-1) the systematic error wandering will be less apparent (although it is approximately the same as for the stochastically well-behaved check star).

Another way to approach the question of whether to believe features in an exoplanet light curve is to perform a transit simulation using non-transit observations. This is done in the next two figures.

 Simulated transit ChkStar

  Figure 7. Simulated light curve using measurements of a nearby check star and adjusting them using a hypothetical transit light curve with TrES-1 properties.

 Simulated using TrES-1 obserations

  Figure 8. Simulated transit light curve using TrES-1 non-transit observations and adjusting them using a hyothetical transit light curve with TrES-1 properties.

The two figures, above, were created from the non-transit measurements of 2004.11.04 by applying a hypothetical transit light curve shape adjustment to the non-transit observations. These plots show what can be expected when observing a transit. If the "eye" detects features in these light curves then the "brain" should intervene and say "no, they're not real; they're roduced by systematic error wander." Indeed, in the second of these simulated transits (based on TrES-1 non-transit observations) note the apparent "bump" before ingress. There is no corresponding brightness bump after egress, and in fact there appearsto be a fading after egress. The first of these "features" must be attributed to systematic error wander and the latter feature may be due to wander associated with high air mass.

The "message" from this simulation is that instrumental anomalies having amplitudes of ~3 or 4 milli-magnitude should be expected from an observing system (and analysis procedure) used by the author of this web page. If other observers want to argue for the "reality" of their anomalies then it may be instructive for them to conduct a simulation using non-transit observations similar to what I have described on this web page. As an alternative light curves obtained by several observers could be combined to see if all of them, or most of them, show the same anomalies. That analysis will be performed for the TrES-1 2004 October/November observations by Aaron Price (AAVSO) in the near future.

In the above two figures notice the better "behavior" of the check star compared with TrES-1. As stated earlier, I do not undersxstand why TrES-1 has a higher stochastic SE than the check star (whose brightness is only 12% greater). It may have something to do with nearby faint stars with PSFs whose edgtes wander in and out of the signal aperture or sky reference annulus. Or maybe the three reference stars were better located for removing flat field errors (i.e., the reference stars "surrounded" the check star better than TrES-1).

This exercise illlustrates some of the considerations and supporting observations that can lead to improved understanding and performance in exoplanet transit monitoring.

Results for TrES-1

The following results were obtained for exoplanet TrES-1during October, 2004.

 TrES-1 ingress

 Figure 9. Each datum is from a median combine of five 30-second exposures, and represents an observation taken within a 200-second observing window (which allows for image download time). A photometric R-band filter was used. The first observations were made just after transit and the observations end when the elevation was 19 degrees (m=3.1). Two "outliers" occur (near 5.0 hours) when I was negligently changing the focus setting. The residuals from an average trace have an RMS = 0.0038 magnitude (excluding the two "outliers").

 TrES-1 merged light curve

 Figure 10.  All data from three transit observing sessions are combined in this graph. The average trace is for 20-minute chunks of data. The vertical offsets were subjectively chosen. I estimate that the 20-minute averageshave a precision that ranges from ~1.8 millimagnitude for most of the pre-ingress data to less than that for the mid-transit section.

Miscellaneous Links

Artificial Star Photometry
XO-1 observations
AAVSO home web page is at http://www.aavso.org/
AAVSO CCD observer's manual is at http://www.aavso.org/observing/programs/ccd/manual/
My TrES-1 observations of three transits is at http://brucegary.net/TrES-1/x.htm
My HD209458 observations of one transit (in 2002) is at http://reductionism.net.seanic.net/HD209458/ExoPlanet.html
AL Aqr (GJ 876) reference stars
My general interest AstroPhotos web page with many links is at http://reductionism.net.seanic.net/brucelgary/AstroPhotos/x.htm
My observatory in Hereford, AZ is shown at http://reductionism.net.seanic.net/brucelgary/AstroPhotos/m_hardware.htm
and you can reach me at the following e-mail address:  b r u c e g a r y 1 @ c i s - b r o a d b a n d . c o m 



This site opened:  October 11, 2004 Last Update:  June 25, 2007