Click on the image to see a GIF video of pulsating RR Lyrae stars (there are MANY in the video - I have arrows to show some of them so you know what to look for in the video...)

M3 Globular Cluster
17-19 March 2016
AZcendant observatory, Rancho Hidalgo, NM
Takahashi TOA-130 at f/7.68
Celestron CGE
Single-Shot Color:
23 20 minute shots used to create a GIF video

The GIF video is comprised of 23 images labeled with an "A" or a "B". Each image is labeled in the upper right corner. Each image was a 20 minute shot. Both the "A" series and the "B" series cover a span of about 4 hours. The "A" images were shot on the night of 17 March. The "B" images were shot on the night of 18 March.

The upper arrow points to a star that gets brighter during each series' 4 hour span. Notice that the other nearby stars maintain about the same brightness although you can see some minor brightness variations in the "constant" stars because M3 was low in the sky (dimmer because of looking through lots of atmosphere) then brighter as it rose in the sky. So you are looking for stars that either get brighter or dimmer compared to the relatively "constant" stars in the video.

The star pointed to by the upper arrow seems to reach maximum brightness at approximately 0209 on 18 March and again on 0042 on 19 March. Assuming no intervening peak brightnesses during the times M3 could not be imaged, then the period of that star would be approximately 22 hours and 30 minutes

The lower arrow points in the direction of two stars one of which is getting dimmer and one of which is getting brighter during the "B" series images.

This is from:

"A short-period, yellow or white giant pulsating variable; RR Lyrae stars belong to Population II and are often found in globular clusters (hence one of their older names – cluster variables) or elsewhere in the galactic halo. They have periods of 0.2 to 2 days, amplitudes of 0.3 to 2 magnitudes, and spectral types of A2 to F6. Some of them have similar light curves to those of Cepheid variables (earning them the now-obsolete name of cluster Cepheids or short-period Cepheids) and, like Cepheids, obey a period-luminosity relation that enables them to serve as reliable distance indicators. RR Lyrae variables, however, are older, less massive, and fainter (with luminosities typical around 45 Lsun) than Cepheids."

I was only vaguely aware of RR Lyrae stars until Tom Polakis published a short video on Facebook showing some of them blinking in a video he created from a few frames covering a 4 hour period on 6 Feb.

This was a LOT more work than I thought it would be. :-) Putting the arrows into each frame caused me about 3 hours PhotoShop research. Also since these were made up of individual frames, cosmic ray hits causing red, green, and blue dots had to be removed by hand. Again I researched Photoshop and developed an algorithm to automatically handle most of them.

On 24 March, I updated the GIF video to also include the previous night's images. The images are each 20 minute images. There is a 5 minute or so delay between each image due to automatic telescope refocus operations using FocusMax. These are the times of each shot:

The images with A prefix in the upper right hand corner label were downloaded from the camera on 17/18 March 2016 at these MST times:

A1       2141
A2       2206
A3       2230
A4       2254
A5       2318
A6       2342
A7       0006
A8       0030
A9       0054
A10     0118
A11     0144
A12     0209

The images with a B prefix in the upper right hand corner label were downloaded from the camera on 18/19 March 2016 at these MST times:

B13     2055
B14     2120
B15     2145
B16     2211
B17     2236
B18     2302
B19     2327
B20     2352
B21     0019
B22     0042
B23     0108