The Runcam “mighty mini” system is very compact, allowing precise recording and timing of occultations of stars to 9th magnitude with your laptop PC. A picture of the complete system is below:
Runcam Mighty Mini Systems for the May 10th occultation of 14 Cancri by (363) Padua
It is an ideal system for recording the occultation of 5.7-mag. 14 Cancri by (363) Padua that will occur across the Sacramento, Phoenix, Tucson, and Monterrey areas Sunday night, May 10/11, 2020.
A picture of the star field taken from a video recording made with the system last night is below; 14 Cancri, the star that will be occulted, is the brightest star, just above and left of center; a star, only slightly fainter, is 13 Cancri to its right.
The precise time is imprinted at the bottom, generated by an IOTA-VTI GPS-driven video time insertion box. “F9” indicates that 9 GPS satellites were used for the fix (at least 4 are needed). Then the Universal Time is given in hours, minutes, and seconds (h, m, s). That’s followed by two numbers that are the ten-thousands of seconds (of the displayed h, m, s) of the start and end of the first video field of the two-field video frame. The last number is just a count of video fields since the IOTA-VTI GPS achieved lock. More about the recordings is below.
The Runcam Mighty Mini is shown better in the two images below. The Runcam camera and everything behind it (including the IOTA-VTI), up to the USB connector to the laptop, is sold by IOTA as a complete kit at http://occultations.org/observing/recommended-equipment/iota-vti/ - Ted Blank in Fountain Hills, AZ runs the “IOTA store” that sells the Runcam cameras, the IOTA-VTI’s, and the kits. The 50mm optics, from an inexpensive pair of binoculars, and the housing for it that holds the camera and the focal reducing lens in front of it, were made by John Moore, john(at)jmooreou.com; he used a 3-D printer to make the housing, which has a photographic tripod adaptor at the bottom. The tripod is an MX 350, a good small tripod used with the old mighty mini’s built by Scotty Degenhardt described at http://scottysmightymini.com/PR/Effects_miniature_optics_occultations.html . The MX 350 is no longer available, but other similar tripods are sold online, and the binocular/Runcam housing combination can be used on any photographic tripod - you may have a better one. But if you want to use the MX 350, it’s simple to operate. Rotate the stick pointing to the front counterclockwise to loosen the altitude adjustment, for coarse pointing. Rotate it clockwise to tighten. For fine control in altitude, I find it easiest to unclamp the top clamp on the tripod leg under the camera, and slowly move up and down, clamping it when the desired altitude has been achieved. For azimuth, the clamp is a collar just above the top of the tripod legs, below the rest (head) of the tripod. Like most tripods, there’s a quick-release square at the top, with the square attached to the bottom of the binocular/Runcam housing. Your tripod may use a different square; if so, you need to unscrew the MX 350 square from the housing, and attach the square for your tripod.
The housing that John Moore 3-D printed includes a small cylindrical cradle on the left side; it’s for holding a specific large-diameter laser pointer, to help point the mighty mini in the sky, but any smaller-diameter laser pointer can be pointed well there. For the Padua occultation, that helps, to initially point to Pollux, and star-hopping from there to the target using the charts that we’ve posted at http://www.occultationpages.com/events/20200511_363_Padua.html with the first few of the “telescopic view” charts being the best to use.
The electronics behind the mighty mini, everything going up to the USB inserted into the laptop, and use of the laptop with the free IOTA Video Capture software, are shown in the picture below and are described very well at https://occultationpages.com/video-package.html . That page was set up for a similar effort, with large telescopes, for the 2018 August 15th occultation of a 12th-magnitude star by Pluto. But for Padua, we are dealing with a much brighter star, allowing use of very small systems like the mighty mini. That package used the old no-longer-available Supercircuits PC164C-EX2 camera, so instead, we have the Runcam camera, whose power connection is red at the end of a long cable in back of the camera, with the video connector (RCA) yellow on that same long cable. If you remove the Runcam camera, with its front-end adaptors, including the 0.5 focal reducing lens, from the mighty mini housing, you can use it with your own telescope, any telescope with a 1.25-in. eyepiece holder. If your telescope has good Go-To capability, or otherwise can easily be navigated to a desired star field, then you are encouraged to use it that way than with the mighty mini; you could record other occultations of fainter stars that way. But if you have any doubts about finding the target with your scope, the mighty mini, with its very wide (about 3.5 by 2.5 deg.) field of view, can provide an easier way to acquire 14 Cancri, to record the occultation. I have up to six mighty-mini systems, as described here, that I want to loan to other observers across the greater Phoenix area, for those who don’t already have their own good occultation recording systems.
A word of caution when using IOTA Video Capture - sometimes when you click on the red circle to start a recording, the screen view freezes, most apparent by looking at the IOTA-VTI numbers at the bottom, which are constantly changing as time advances. If they are not changing (screen frozen), you are not recording. This may be due to insufficient free space on your PC, but we’ve seen it happen when there was adequate space. You can exit IOTA Video Capture and restart it, but sometimes, that doesn’t fix the problem. If this happens only a minute or two before the occultation, there won’t be time to restart the program. In this case, click on the black box, which will stop the recording attempt and you should then see the real-time (unfrozen) display. Use your smart phone to video record the screen of your PC; we can extract accurate time from your smart phone .mp4 video file. We actually recorded an occultation that way in December 2019, so we’ve gone through the process to analyze such a recording.
Other Runcam camera views are shown below, including the position display that you need to record sometime before or after the occultation, to record the latitude, longitude, and altitude above sea level, of the location from which you observed. There’s a switch in the middle of the front of the IOTA-VTI box that toggles between “Position” and “Time”. That needs to be in the lower “Time” position during your recording of the occultation, as shown in the picture of the star field above; the picture below is with it in the upper “Position” setting. Another view is obtained by depressing the button at the end of the short cable extending from the Runcam camera. That gives an on-screen display that you can navigate by pushing the button up or down, or left or right. When you press the button, you get the top, or “Main”, menu. Press the button when the highlighted area is over the top line, “IMAGE”, to see the camera settings as shown on the “camera settings” picture below; they should be as shown when I give you the equipment. If you use it for fainter stars, the Night Shutter (NS) setting can be increased to 3, providing some integration (8 video fields) at the expense of time resolution, but NS should be “1” for bright stars like 14 Cancri. Also, the “MAX GAIN” should always be 9; it can be decreased in case of a bright background due to twilight. Selecting RETURN at the bottom returns to the main menu. Be sure to move to and click on (press the button) “exit” at the bottom of the main menu, to turn the display off, before recording for an occultation.
An annotated version of the RunCam field of view is below, followed by an equivalent Guide8 chart showing the same field. The star labelled “RX” above and left of the target is a red (spectral type M8) variable star RX Cancri. It seems to be near maximum light now, only a little brighter than mag. 8.0, but it appears like a 6th-mag. star, fainter than 13 and 14 Cancri, but brighter than 6.6-mag. star A (SAO 79987), with the red-sensitive Runcam camera. The view shows (faintly) an 8.6-mag. star to the upper right of 13 Cancri, but it’s the brighter star, 14 Cancri, to its left that will be occulted.
The field of view appears a little clearer when viewed with real-time video; below is a 1-second clip (.avi file) showing it.
14CncMightyMiniFOVwithUTshort.avi - 1-second video, 28.6 megabytes
Some past asteroidal occultation recordings - links to a couple are below, to give you some idea of what to expect. A recent occultation was documented well by Peter Nosworthy (the Wonky Astronomer) as shown in his excellent Youtube video at:
It doesn’t just show the rather faint occultation, but goes through the whole process of finding and analyzing the asteroidal occultation. Another video that I made several years ago in Florida with a less-sensitive camera, of a 6.3-mag. star (still not as bright as 14 Cancri) is at https://www.youtube.com/watch?v=EgDTJhemkvQ; it is of interest since it was a graze, with the star disappearing twice in quick succession as the two ends of a peanut-shaped asteroid covered the star; that event was recorded at two other locations that had one occultation of the star (as usual).
David Dunham, International Occultation Timing Association and KinetX Aerospace
Version 2" on "May 5, 2020
Practicing for, and observing, the 14 Cancri/Padua event with Runcam mighty mini’s
A few additional cautions are given below. First, read everything on the Runcam mini page at http://www.occultationpages.com/events/Runcam_Mini.html and all of the links given there, especially the one at https://occultationpages.com/video-package.html which describes each item and how they connect (but the camera there is an older, no-longer-available Supercircuits camera rather than the Runcam camera described above). It includes the link to the StarTech SVID2USB23 video capture device page with the driver you need to download to run IOTA Video Capture on your laptop; it’s at https://www.startech.com/AV/Converters/Video/S-Video-Composite-to-USB-Video-Capture-Cable-TWAIN-Mac-Support~SVID2USB23#dnlds . A note - there’s a green light on the SVID that should be on when it’s working, and the VTI and camera have power.
The Runcam camera has an onscreen menu system, as described above. You should check the IMAGE menu (like that shown above, just below the IOTA VTI position display) to make sure the MAX GAIN is “9” (the highest setting); often when the camera first turns on, it’s “1” and the view is too dark.
Try to test the equipment this (Saturday) evening; it looks like it’s fairly clear now, but there are clouds to the west that are expected to increase and move in. So the earlier you can do it after dark, the better; you might be able to see more than Venus. Since the mighty mini is just on a stationary tripod, the idea is not to find the target, since then you have to adjust every few minutes to keep it in view [but with the wide field of view (FOV), it will take the about 10 minutes for a star to drift across, due to the Earth’s rotation]. Instead, point the mini to the pre-point line of declination, as shown on the labelled charts at https://occultationpages.com/events/temp/StarCharts20200511Padua.pdf, especially the charts shown on “slides” 3 (it describes the pre-point line), 4, and 5. Once you’ve pointed the Runcam Mini to the pre-point line at the time specified along it, you’re pointed at the altitude and azimuth that the occultation will occur, and you don’t have to make any more adjustments; the Earth’s rotation will carry 14 Cancri into the FOV and it should be close to the center when the occultation occurs. The best pre-point opportunity is the one at 4:50 UT (9:50pm MST), when you can center the FOV on 76 Geminorum, a 5.3-mag. star only about 3 deg. below and left of Pollux, as shown on the star chart on slide 5; the Runcam mini FOV is slightly larger than the rectangle shown there. You don’t have to wait until 9:50pm to test the pre-pointing; you could do it anytime earlier, and then you can see the target drift into the FOV about 25 min. later. You can also use the mighty mini FOV to make adjustments, to simply star-hop to the target field, to see what it looks like (should be like the 2nd image of this page).
If you use the tablet we provides, it turns on with the button on the top of the right side. It’ll take a minute or two, but IOTA Video Capture will turn on automatically. If the display is from a tablet camera (there are two, one on the front and one on the back), you need to go to options, and click on video device, and make sure the external USB device is there, which you can select, to get the view from the camera (remember to remove the rubber cover at the front of the mini).
The mini should be in focus for distance; I focused it on Mt. Ord, at least 10 miles from our office window, from which I made the short test recording. The 1.25-in. front-end of the camera is just a rather tight friction fit into the mighty mini; I don’t think you’ll have to adjust it, it’s probably good enough (don’t need perfect focus for this event, but it should be good enough to 7th and 8th mag. stars).
Also if you use the tablet, the connection of the USB-to-USB-C adapter to the tablet (the USB-C connection) is sometimes “wiggly” and can disconnect you, the display will go dark. Then you have to restart IOTA Video Capture. That’s why it’s better to use your laptop, if you can, with the regular USB connection (don’t need the USB-C adapter).
Don’t use the 8 AA cells with more than one device (that is, don’t use it with a splitter); the connection at the top, especially with the ones with the red and black wires, will smoke and melt, shorting the unit, if it tries to support the load to more than one device. I provided an extra one, in case you have any problems with the two I provided (one for the camera and one for the IOTA/VTI).
Good luck with your tests tonight; feel free to call or text if you have any questions.
David Dunham, 2020 May 9