First off, let me apologize for not having replied to many posts by astrophotographers I follow on Astrobin.  I play in a praise band at my church and when Easter rolls around the music gets strongly emphasized in the services and I play in a lot of them and have to attend all of the accompanying rehearsals, not to mention hours of practicing.  I hope to catch up on looking at everyone's images in the near future.  

On to this post.  Tom Gray recently posted a very nice image of M3, a beautiful globular cluster in Canes Venatici and noted that it contains a large number of variable stars.  My four inch scope is probably not capable of detecting the globular variables without really extended exposures, so I though I'd at least image the cluster and see what else is in the vicinity that might be a brighter variable.  I attempted to capture the images on 4/8/2022 and had a really rough time with bad winds and tracking that didn't work so well when challenged by wind shudders.  I ran two sets of images, the second being better because I bumped up the aggressiveness of the tracking.  Overall, I acquired a total of 105 minutes of actual exposure spread over 2.21 hours of time.  For M3, I had to hand select images that weren't completely awful due to wind shudder, ending up with sixteen that I stacked and processed, which amounts to 48 minutes of integration.  I used every trick I know to produce a cluster image that was not so bad that it would crack the computer screen due to ugliness.  I was able to make the stars rounder with StarTools healing and other deconvolution algorithms and did my best to pull out color and detail while having a dark sky background.  Really, though, the cluster image is necessary to the post due to the real success of the endeavor:  finding an interesting variable star with Muniwin named RV CVn (RV Canum Venaticorum n), the position of which I could then indicate on the cluster image (arrowed).  I have to say that Muniwin did an amazing job of handling pretty sketchy images to generate a very nice light curve!

RV CVn is a contact (the stars literally touch one another) eclipsing binary of the W UMa-type that apparently is not frequently imaged.  In fact, the variable star index of the AAVSO has no observations listed for this star system.  Zasche et. al. report in a 2014 paper that reliable light curve data for RV CVn were not available until the study undertaken by this group generated the data that led to the paper.  In addition, changes in the period and brightness variations of the star system were observed through data acquired by the team and previous literature data.  Part of these changes is certainly due to mass transfer between the stars, but another factor is involved, namely, the stars orbit a center of mass such that both stars move rather than one remaining essentially stationary.  Depending on the orbital elements, the dual motion of the stars can manifest changes in the brightness variations.  In fact, the research team investigated the possibility that a third member of the system might exist that, while not bright enough to affect the light output of the system, might have sufficient mass to perturb the orbital motions.  Basically, the results suggested that a third member is not present, but there was some uncertainty in this conclusion.  The light curve of binary stars like RV CVn has brightness decreases that are very similar for both the primary and secondary eclipses because the stars are very close in surface temperature.  I hope to get in one or two more runs on the RV CVn system and and get enough data to put together a complete light curve.  The portion of the light curve posted here is about 1/3 of a full cycle.