Observing with Street Lights

Observing with Street Lights
Dark sky sites not always necessary to see the Milky Way (This image was taken ouside of a B&B in Julian, CA)

Sunday, July 16, 2017

Astrophysics: The Violent Universe; Picked up new Li-ion mount battery from OC Telescope; Picked up new Sol-Searcher and filter; Used drift method to monitor sunspot field rotation observed with a alt-az camera tripod; Double check drift assessment with actual measurements


Greetings from Palmia Observatory


Well this week has again been a week of not much nighttime observing, with a little bit of daytime solar observing, not because of weather, but because of other commitments.  For the past half dozen months we could not observe a Black Star canyon due to weather, but now its because of other commitments this time season theater tickets.  Yes, we could exchange our tickets and find ourselves perched up in the nosebleed seats on the new date, but we chose not to do that.  Besides, I would have had to disassemble my rolling tripod assembly and pack up the scope and mount and I still haven't had a chance to go outside and try the whole thing out yet.  But, some exciting things have happened like,
getting new equipment accessories and making some solar measurements.

Before getting into all of that I should mention again that the free course on the internet on Astrophysics: The Violent Universe is back again.  If you want to get a little more into astrophysics, and do a few calculations on orbits and such, check it out at: https://www.edx.org/course/astrophysics-violent-universe-anux-anu-astro3x-0
You can watch the videos at your own pace and take some of the little quizzes at your own pace.  The website asks if you want to pay and get credit for the course, but just say no and audit the course for free.  The course mostly uses just high school math but you still get to do some pretty interesting calculations and find out for yourself how many of the really neat conclusions about astronomical objects are determined.  In the first lesson, we learned how Bessel in the 1840's determined that Sirius, among many other observed stars, had an unseen companion and how the calculations we performed in class are used to determine the mass of the companion based on the observed orbital period and assumed velocity in an assumed circular orbit.  Of course, Bessel, who for many of use have a love/hate relationship because of his darn so-named Bessel functions,  had to solve the real problem with elliptical orbits and such, but it is neat to follow in his footsteps with our simplified version of the problem.  Check it out, you might be amazed and excited about the next lessons!

One of my errands for the day included running by Polly's Pies and picking up a fresh peach pie.  Yes, it is that time of the year so if you enjoy fresh peach pie, go out and get one!  Anyway, on the way back from Polly's, on N. Main St., it was just a few blocks further down to OC Telescope in Santa Ana.  I've always enjoyed stopping by and seeing Mike Fowler and checking out the latest scopes and accessories in his recently expanded store location.  One of the things that I wanted to check out was the new, very small and lightweight Li-ion battery that Retired Semiconductor Physicist, John, had got at OC Telescope for the Revolution Imager that he won at the OCA Banquet last year.  So, I stopped by and talked with Mike and decided to get the new battery for my telescope mount to replace my other heavy lead acid battery.

Hey, it just occurred to me that maybe Polly's can offer flyers for OC Telescope and they in turn can offer flyers for Polly's or maybe special deals.  Why not make you chore into a grand loop and get both done at the same time!  Or, maybe this idea is why I didn't make it as a marketer and had to make it as an engineer!

Anyway, OC Telescope, Kenny, helped me out and showed how small this new battery is and the kit comes complete with wall charger and power cables.


Stopped at OC Telescope and Kenny showed off this Li-ion battery
Stopped at OC Telescope and Kenny showed off this Li-ion battery (and I just had to buy it!)

When paying for the battery and filling out the invoice, I used my business card for the details and Kenny appreciated my title, Resident Astronomer, Armchair and Observational Cosmology and showed me his own business card where he is titled "Skyintist".  Hey, I like it! Thanks Skyintist, Kenny!

Ok, so here you can see just how small this new battery is in this photo.  Its about the same size as a modern IPhone and just a bit heavier.  The battery kit includes the wall charger and a straight plug for the connection to the mount.  My Ioptron mount requires a right angle power cord, which did not come with the battery, but my friends at Amazon shipped me one within a couple of days


Just received my right angle power cord for the new 9.8 Amp-Hr  Li-ion battery

Well, I still haven't found the time to schedule taking out the new battery for telescope and rolling tripod assembly, but I did squeeze in a couple of 5 minute observing sessions of the sun.  As you know, last week I used a homebuilt solar filter that easily slides over the telephoto lens that I plan to use to take at least one photo of the eclipse in August.  It turned out that I had not thought through all of the details of how I might want to adjust the focal length and especially adjust the focus and had to cut extra holes in the cardboard tube to accomplish that, so I just bit the bullet and purchased a more user friendly, easily removable slip on solar filter.  See below how the filter just slips over the telephoto lens and the setscrew can be used to lock it in place if necessary but this should be really easy to remove, without disturbing the camera setup and position, during the eclipse.

Also you can see a new accessory I am trying out and have it taped to the lens.  This Sol-Searcher by Tele Vue uses a pinhole in the front, facing the sun, to project the sun's image on a translucent screen.  This device makes finding the sun much easier than my previous approach of just sort of squinting and aiming the camera and panning and tilting in trial and error attempt until the sun shows up in the camera Liveview screen.  This new tool enables me to find the sun in under a minute rather than the several minutes it took me the other way.  I still have to tilt and pan the camera but it much easier to find the sun, especially sometimes when in bright sunlight I can't see the dim sun, due to not being in focus, on the Liveview screen.  Now I'm investigating a mounting accessory that let's me mechanically attach the Sol-Searcher directly to the camera hot shoe rather than use tape.


New (purchased) solar filter and Sol Searcher (taped on the lens) Source: Palmia Observatory
New (purchased) solar filter and Sol Searcher (taped on the lens) Source: Palmia Observatory 

Ok, for this new setup, I took the whole thing outside for a 5 minute observation of the sun.  Luckily, it turned out that there was a large sunspot visible during this observation.  Our previous post of June 22 described how it is possible to assign cardinal direction points to your photo images based on the drift method.  Unfortunately the images of the sun on June 22 did not have any visible sunspots, so the incorporation of cardinal directions did not mean as much.  Remember the drift method is where you turn off the telescope mount drive, or in this case with just a camera tripod, do nothing, and watch the direction in which the object moves across the screen.  This direction is west!  Based on this and assigning the other directions according to how many reflections occur in your telescope optics, which in this case is north direction will be 90 degrees counter clockwise from west.  The image with a visible sunspot and assigned cardinal directions is shown below.  This photo was taken with camera mounted level and pointed directly at the sun, so it is just like the image you would see with your own eyes if you could look at the sun.



Used drift method to establish cardinal points for sunspot image taken with an Alt_Az non-tracking mount (Source: Palmia Observatory)
Used drift method to establish cardinal points for sunspot image taken with an Alt/Az non-tracking mount

Ok, now let's look at the same type of image taken later in the afternoon.  Wow, look how the sunspot now appears in a completely different location.  Did the sunspot move that far during this period of about 5 hours?  No, not really.  We are seeing just plane old field rotation of the image that occurs due to the rotation of the Earth.  Using the drift method again we can see that the cardinal points have moved around so that the sunspot is still located pretty much where it was observed earlier.



No, the sunspot did not move that much.  Note cardinal points show image rotation with/Az non-tracking mount (Source: Palmia Observatory)
No, the sunspot did not move that much.  Note cardinal points show image rotation with/Az non-tracking mount

Again, the sunspot location is just where you would see it with your own eyeballs if you could look at the sun.  But if we had used a polar aligned mount, the effects of frame rotation would not have been noticeable.

Now, we should get a little bit into the science part this observation and post.  Careful readers might notice some discrepancy in the listed cardinal points and locations.  These points were identified by just my eyeball guess as to the direction that the sun moved across the screen.  To measure the drift more accurately, I took one other image at one minute later at 15:55.  Then with both images brought into Photoshop I could measure the actual drift in terms of pixels per minute in both the x and y directions.  Wow, as it turned out, my eyeball guess was off by about 37 degrees.  The real direction of west in the 2nd image should be positioned about 37 degrees counterclockwise to the listed position.  Probably my eyeball guess of drift for the 1st image was similarly off by some unknown amount and unfortunately it didn't occur to me to take a 2nd image at that time.

So, how much did the sunspot actually move?  I don't know but did try to measure how far the sunspot was from the center of the sun.  For each image, I measured the center of the sun's image, assuming it is as shown as a flat circle.  Of course the sun is not a perfect sphere and the location of the sunspot is on a sphere and the measured distance on the flat image is not going to represent the real situation.  But, given all of these assumptions, my measured distance agreed between both images.  So, some of you more ambitious amateurs can do the full calculation while I wait inside in my air conditioning and armchair.

Until next time,
Resident Astronomer George





1 comment:

  1. An interesting post about astrophysics and its associated history. This post will appeal not just to history but also to science enthusiasts. I definetly recommend a read.

    ReplyDelete