One of the exercises in a CHOICE course on how to use VStar, a neat variable star analysis tool provided by the AAVSO, was to use the Leavitt's Law plugin to calculate the distance to Delta Cephei. The following was my response, and it led to an interesting study of how we use Cepheid variables to compute distances to star clusters and galaxies. We might expect this to be cut-and-dried in our era of space-based astronomy, but it turns out to be "not so".
I downloaded data on Delta Cep from the AAVSO data download portal, not from the VStar menu that loads data from the AID, mainly because I wanted to store the raw data file locally. That means there was no associated period information from the VSX. With my new skills at determining periods with DCDFT, it was easy to narrow down on the period, first between 2 and 6 with resolution 0.01, which reported a top hit of 5.37 days, and then with a narrower search from 5 to 6 with resolution 0.001 days, which reported a period of 5.366 days. Using that with Leavitt's Law yielded a distance of 273.16 parsecs.
To find the distance of Delta Cephei, my Patrick Moore's Data Book of Astronomy was my first choice, but that didn't list a distance, only magnitudes and period. My next choice was Cartes du Ciel, the star mapping and planetarium software that is my favorite. It didn't list the distance either, but provided a link to Simbad. The Simbad page loaded lots of information on the star, but not the distance, until checking the distance box in the Measurements area yielded the following: 0.244 kpc, which is 244 parsecs. This compares fairly well with my calculation using Leavitt's Law, to within about a 12% error. That seems somewhat excessive, especially since Del Cep is the prototype star for this class of variable.
The problem seems to be calibrating Leavitt's Law to absolute distances, not the relationship itself. That is assuming you are using the right type of Cepheid, as there is a difference between two "overtone modes". This website explains how the Hubble Space Telescope used highly precise parallax measurements to determine distances to 10 nearby Cepheids to better calibrate Leavitt's Law. This sounds paltry, but Cepheids are relatively rare and there just aren't many that are close enough to measure by parallax. Hubble measurements claim an accuracy of better than 10%, though. Hubble also measured 10 Cepheid variables in the Large Magellanic Cloud and found the slope of the linear relationship between logarithmic period and luminosity to be very close, assuming that all of those variables are at about the same distance from Earth. The calculated distance to the LMC is about 49.4 kpc, which puts it outside the diameter of the disk of the Milky Way Galaxy, which is about 100,000 light years, or 30,674 parsecs, calculated by dividing 100000 ly by 3.26 parsec per ly.
Since Leavitt's Law calibrates to absolute distances via an assumed distance to the LMC, this can lead to a rather knotty problem of chicken-and-egg origins. Current estimates of distance to the LMC from various sources, described in this excellent lecture notes webpage, put the distance from about 44 to 51 kpc, a variation of about 15% from the average of the two estimates. So now we see where the uncertainty comes from. We just can't do any better for now.
Wyoming has been wonderful this summer, but here in the high plains of Laramie there are signs of fall in the air. Actually, the sign was on the ground this morning. On my way to my rebounder in the backyard of the apartment building there were frost-rimmed leaves on some of the broad leafed plants in the lawn. It was a pretty sight, but somewhat chilling, in a double sense. Like a true snowbird, my thoughts turned to escape for when the truly cold weather arrives, along with the snow and ice. Of course, Laramie is fairly high in elevation, over 7000 feet, so the rest of the state, and Story in particular, probably won't see frost for another 3 or 4 weeks.
The summer has been busy with handyman work and maintenance tasks. There were numerous small tasks to complete on my sister Sylvia's rental properties in Sheridan to get them ready for external painting and new renters. There was repair work to be done on my RV parked on my property in Story. My car needed new tires after the long road trip to Arizona and New Mexico. Also, my friend Janell in Laramie had several remodeling, repair, and cleaning tasks that could use my help. My telescope system needed some attention, too.
It all started when my music instructor invited me to present my final composition to him and a fellow student in early May. Leaving Laramie that morning (the 11th) gave me just enough time to drive to Sheridan, although it turns out the meeting was one half hour later than expected, and the other student didn't show up (spaced it out, he said later). After my presentation, which a few onlookers from another class watched along with the instructor, Chris Erickson, another class presented their music technology capstone projects, and the instructor for that class invited me to stay and evaluate the presentations. That was fun, as there were some interesting ideas for recording engineering, band promotion, and recording educational videos. The last project was closest to my current interests, as that is one of my goals for the observatory and data collection that has become so important to me.
Ever since my sister Shirley had told me a few weeks before about the tree trunk that had fallen on my RV roof, visions of a crumpled roof had occupied my imagination. Upon returning to Story the RV looked remarkably good from the outside, considering the size of the trunk that had broken off a dead pine tree next to the RV and had fallen perhaps 20 feet before impact. Inside was a different story, though. Water had seeped in despite Shirley and Jim's efforts to patch the roof, and many items on my drafting board and underneath on the breakfast nook seating area were saturated. That included many of my music books (boo-hoo). There was nothing to do but haul out the wet and moldy stuff and dump it on the rock pile beside my front door. (Remember, my place in Story is still a construction site, with big excavation pits and thousands of cobblestones piled in various places.)
Even my old digital camera (Sony CyberShot) got soaked. Luck was with me, though, as it still powered up and worked once allowed to dry out. Funny, that camera would have been handy for my trip to Arizona, since my cell phone camera pictures only look good on a small screen or in a website blog (like this one). In my rush to leave Story in January, that camera among other items got left behind. Oh, well.
It took several days to unpack and acclimate myself to Story again. Of course one of my first destinations was the Public Library, where everyone greeted me after my winter absence. It was good to ride my bicycle up the Fish Hatchery Road again, and resume my schedule of spending Sunday afternoons with my sister Shirley. We also took another quick day trip together, along with her husband Jim, to Bozeman Montana for a memorial gathering dedicated to my late Aunt Nora. That was a pleasant drive in the spring greenery and it was fun to meet some of my cousins and aunts again, having seen them perhaps nine months earlier at the Jenkins-Allen family reunion in Buffalo the summer before.
Work commenced on my sister Sylvia's rental properties in Sheridan, and both my pickup and car provided transportation for the 18 mile commute from my place in Story. The truck started right up after sitting for over 9 months, thanks to my having it hooked up to a battery maintainer all winter (along with the Volkswagen Rabbit parked next to it). After many interesting conversations with Erin Adams, the property manager for Sylvia's rentals, we got the house and apartment buildings ready for the painter, who started his crew on the job in early June. My role was just to provide support, since Erin was handling the contract. We provided feedback to the roofers that were repairing some of the siding that was damaged due to splashback from dormer and porch roofs, and evaluated the new roofing on the apartment. Everything was on track and proceeded smoothly.
Sylvia arrived for a short visit in late June and we had several long visits, which helped us clarify our feelings about the apartment renovation job that was now complete. Sylvia validated all my hard work on that project by saying she thought it was money well spent, and it was best to do things the right way. She seemed in good health after her three year teaching adventure in Saudi Arabia, and was glad to be done with that and was looking forward to retirement. Of course, there were new concerns associated with making that transition, not the least of which was how she would adjust to a reduced income.
My promise to return to Laramie kept being put off for various reasons. The discovery that my astronomy camera didn't work when testing the new observatory control computer my son Jason built for me, way back in May before returning to Story, required me to send it back to the manufacturer for repair. It turned out to be a fried component in the USB circuit, probably caused by a bad ground connection. It must have been disconnected improperly in April when the system was being disassembled, as it worked fine during the last observing run. Of course, the manufacturer said that wouldn't have happened with the supplied power supply. Having rigged up my own power system from my batteries, there was no room to argue and it cost $300 to get it fixed, plus the $60 to ship it out to Missouri and another $35 to ship it back. So my attempt to save power by eliminating the inverter and using buck converters to obtain the proper voltages cost me almost $400 in the end. That was lesson number one in the School of Hard Knocks.
The other lesson turned out to be the tires on my car. They had been making noise for several years, ever since my starting to use it to haul my tools into Sheridan for the apartment renovation job, but the tire store said they couldn't detect any abnormal wear and thought the noise was coming from a bent wheel. That didn't sound too serious and my plan was to drive the car with the existing wheels until the tires needed to be replaced, and then buy new wheels and tires simultaneously. Well, that day came on the last day of the apartment job, just before my anticipated return to Laramie. Coming up Tunnel Hill not more than a half mile from my driveway the car started vibrating, and turning into my driveway a quick look confirmed that the left rear tire was flat and ruined from driving on it.
Upon closer inspection of the wheels and tires, after purchasing a floor jack to lift the car safely, showed both rear tires were completely worn out, with the steel belts showing on the inside edges. Evidently my loading the car down with tools and telescope gear took its toll on the tires. The extra weight must have changed the camber on the axles to splay the wheels outward on the bottom, causing the insides of the tires to wear prematurely. No way will that happen to my new tires! From now on the car will only haul people and their luggage, and not be handled like a lumber wagon.
It turned out that my new wheels and tires, ordered online from Discount Tire Direct (a set of luscious Vox Torino aluminum wheels and Pirelli P4 FourSeasons Plus tires) were delayed, plus the centering rings they sent were the wrong size, so there was nothing to do but wait. Ah, but there was something to do: take a hiking trip with my daughter Keely to Penrose Park, and visit Tongue River cave. Both of those adventures were great fun, and it was wonderful to spend time with Keely before her flight to San Francisco and the beginning of her graduate studies in chemistry at UCSF.
Keely is a great outdoor adventurer, and we had a good hike up to our camp spot at Gin Creek (with water so clear it looks like gin, or that the cow punchers that used to camp there always brought gin, who knows). Upon arriving at the camp site, about five miles and a couple thousand feet in elevation from Story, we decided to hike another five miles with minimal packs to Penrose Park, a high alpine meadow about three miles long and one mile wide, with spectacular views of Penrose Peak, Black Tooth, and Cloud Peak toward the west. On our way up Long Draw, we saw a herd of elk, which ran up the draw beside us for perhaps half a mile. We even got to see a calf nursing from its mother! At Penrose Park, the skies were alternately sunny and cloudy, with afternoon thundershowers brewing. We stayed maybe a half hour, taking panoramas with our phone cameras, and headed back just as the rain started to sweep across the park. Luckily, there wasn't any close lightning, and we both had our rain gear, so we were fine walking back. The biggest challenge for me was to keep my legs from cramping, which required me to keep moving.
Upon returning from our camping trip, we stopped at my sister Shirley's house for a wonderful afternoon meal and an evening of conversation. About a week later Keely suggested we visit Tongue River cave, having only seen the beginning part years before when she and Jason, my nephew Tom Pearce, and I made a spur of the moment excursion there. That time we ran out of time, since Jason had a music lesson in town to attend, and we didn't have proper lights or protective clothing anyway. This time we were better prepared, with coveralls, gloves, hard hats, and helmet lights. It also required a permit, which Keely procured online. We drove my truck to the canyon and began our hike into the cave at around 1 PM, exploring the nearly one mile underground route down into the Rain Room, the Bat Crawl, the Mouse Hole (a tiny squeeze where the wind blows past you), the Subway Tunnel, the Corkscrew (a 3/4 twist that takes you down into the Boulder Room) and all the way back to the underground river and the Falls. By the time we got back out it was early evening. We spent a good five hours in there, with a few 5 to 10 minute breaks for utter silence and darkness. The rest of the time we were climbing, crawling, and walking in the 55 degree cave environment.
Keely left for San Francisco a few days later, and my truck packed with tools and my telescope took me to Laramie. Check back later for a continuation of my adventures with Janell and her son Adrian, and my good friend Suzanne.
The Arabs did it. The Polynesians did it. Almost anyone who traveled in the wilderness probably did it at some time. How else would you find your way in a featureless landscape, especially at night when visibility is limited to maybe 20 feet at best? Well, now I can say that I have entered that club, because the stars are what got me back to camp early this morning.
It started at 4:45 AM when I had to, ahem, take care of some urgent business, and walked some distance from camp with only my red headlamp for a light. The light wasn't much good except for dodging creosote bushes and avoiding rabbit holes. I wandered off in a general direction I usually take for such business, and wound up in an area indistinguishable from myriad other areas near my camp. It was dark and the stars were bright, the Moon having set hours ago.
After taking care of said business, I started back for camp. I walked for what I thought was the right distance and guess what? No camp. Hmm. That was embarrassing. How could I possibly get lost in the desert not more than 200 feet from camp? Well, it turns out to be surprisingly easy when there are creosote bushes every 10 feet and my light is only good for about that distance. The landscape was relatively flat, so there were no clues from slopes or drainages.
Standing in the dark in the early morning, not knowing where I was or which way to go, was an unnerving experience. It would be hours yet before sunrise. I didn't want to wait that long to find camp. I couldn't just keep walking, though. I could wind up miles from camp. That much was clear.
Then I looked up and saw all the constellations. Scorpius had been high in the sky outside my tent window. What direction was that, southeast? Oh, it was the opposite direction from which I started walking away from camp not ten minutes ago. Okay, there was the Dipper and the North Star. So East was to my right. Let me think. My camp was south of Highway 9, on a gravel road that ran pretty much north-south. The dirt two-track to my camp branched off the gravel road towards the west. If I could intersect this two-track that would lead me either to the gravel road, or to my campsite which was only 20 feet or so off the track.
I had walked northwest for my business appointment, so I needed to walk southeast to return to camp. If I overshot, I would hit either the two-track or the gravel road. Sure bet. Start walking toward Scorpius. Okay, there's the two-track. Turn left and follow it. Okay, there's the gravel road. Ah, too far. Turn around and follow the two-track back the way I came. Top the slight rise and go down into the bowl ahead. Yay! There is the reflection from my car's taillight. Home in sight!
The moral of the story? Don't think you can't get lost just because you are close to your camp. You could miss it by 40 feet in the dark and brush. Stop when you realize you are lost. Use the most powerful tool that you have: your mind. Reason out your directions and make a plan. Then act on the plan. If your thinking was sound, you will be back in camp cooking breakfast before long.
Thanks to Jerry, Susan and Sylvia for checking in with me. It makes me feel like someone cares about me, although I know that all of my other friends and relatives care, too. Susan has written me a few letters, but I may not have gotten the last one as it could be in Tucson. I haven't gone back there to get my mail, and probably won't take the trouble to do it even when it is time to go back to Wyoming. My most direct shot will be to go east to Las Cruces and then north to Albuquerque and Santa Fe.
I haven't gone anywhere since Jerry left except to Animas a few times for water and groceries. I thought about driving to Deming or Douglas, but decided that the 3 or 4 hours and gasoline it would take wasn't worth having fresh produce. I am getting by with rice and beans, potatoes and onions, and some of my dry goods like flour and sunflower seeds. I still have enough for breakfast and I make waffles for supper. (New Improved Waffle Recipe!) I figure I can hold out for a while this way and still have enough to eat.
I am thinking about heading back to Wyoming in a couple of weeks, once the dark cycle is over. The weather might be getting decent up there in three weeks or so and I would like to start working around on my place, cleaning it up and finishing a few projects, like the cottage and root cellar. I also want to spend a few days in Laramie on my way back to visit Jason and a few friends.
The weather has been pretty severe in the last week or so, with a couple of bad wind storms, some rain, and cold temperatures. Lets just say the wind was something to get through, and not at all a good time. It was hard on my tent and astronomy equipment, and even knocked my tripod and telescope over during a particularly hard gust. Luckily the counterweight and outer rim of the telescope tube took most of the impact, and I don't think it actually fell that far. One of the tripod legs telescoped back in under the extreme pressure and it overbalanced the system. Now I crank those telescope leg screws down as tight as I can get them.
So far it looks like everything still works, although there is a 3 inch diameter shallow dent in the side of the telescope tube where it impacted the tripod head. Amazingly, the telescope seems to still be collimated. I am really impressed with this scope. It is built like a tank and is completely trouble free. Other than that there are no signs of other damage. The mount still works flawlessly (with occasional RA dropouts) and the camera and focuser are fine.
The tent is definitely taking a beating. The rain fly has duct tape in three places where rips were starting to form. One of them is about two feet long, where there was a seam over the control room side of the tent. One of the tent poles snapped when the telescope went over and I stuck it back together with a spike and some duct tape. There are several new holes in the yellow inner tent from rubbing on stuff during wind gusts and the zippers are difficult to work, even after lubricating them with soap. (The spray lube didn't work, and wasn't really dry like it said. It attracted dust and discolored the fabric on the tent. Also, the spray nozzle was broken and it leaks like crazy at the can. I think I will take it back when I get to another Wal Mart.)
At one point during the storm the tent was almost flattened, and all I could do was slouch way back in my chair with my feet under the table. The tent ceiling was pressing down on my head and I felt like a giant was stepping on me. There wasn't anything to do but read my Designing Sound book and listen to the deafening wind noise and flapping of my tent. The wind even continued through the night, calming sometime in the early morning, only to begin again when the Sun came up. I am definitely out here with the elements. That is one of the "benefits" of tent camping versus being in a motor home.
So I am fine out here and I still am enjoying it when the weather is good. Last night was clear but I was busy finishing a music class assignment, so I didn't do any observing. The night before I did my own double star marathon, and logged maybe 20 or so observations. It seems I can just barely see two image circles when they are about 8 or 9 arc seconds apart. Some of them are challenging, in that there is a wide magnitude difference. I got one pair that was about a mag 7 and mag 15. The dim one was just a ghost of a star and the bright one completely overexposed, but I at least got it. I didn't bother saving the images, but I did record my observations in my AstroPlanner program.
I am contemplating my next observing run, perhaps tonight if the weather holds. I might do more star clusters, or perhaps some asteroids. I need a good goal with some science behind it. I did set up a rudimentary variable star observing plan a week ago and got one set of observations, but most are long period variables and probably don't need another set of observations right away. I'll have to wait until my data usage counter resets on the 4th before I can do any more research on candidates for another variable star run. Right now I am trying to squeak under the wire at 5 GB, and I only have about 100 MB left for today and tomorrow, when it will reset.
What I really need to do is get my system so it will run unattended, or at least while I am in my sleeping bag staying warm. Night before last I got so cold that even when I did go to bed at 1:30 AM I couldn't sleep. My feet and legs didn't warm up until morning when I got up and cooked breakfast. Last night was better, as I bundled up and the weather wasn't so cold. Still, I was tired at midnight when I finally finished my assignment and I decided to turn in while I at least had the chance for some sleep.
I am getting cold feet on driving out to New York for Keely's graduation, and doubt I would want to fly. Devona will be there to watch the commencement, so Keely will have some family even if I don't go. I had thought of stopping in St. Louis for the AAVSO annual meeting in early May, but I don't think I would want to haul my equipment all the way out there and back if I went directly from New Mexico, and once I am back in Wyoming I know I won't want to go anywhere for a while, unless it is for a camping trip to the Red Desert. I am anxious to see what the dark sky is like down there. Even here in New Mexico there is a definite sky glow. I guess there is no escaping it, unless I go to Chile or Africa. (Now the Kalahari Desert in Botswana has me interested.)
Over the past few weeks it has been creeping into my consciousness that static electricity might be disrupting my telescope. Not only does Windows 8.1 make its sad little USB disconnect chime every time I get near the computer, but the mount starts acting up. It stops tracking during the middle of an exposure and the mount software even crashes, as does Maxim DL. I was pulling my hair out.
Yesterday in a desperate attempt to get control of this problem I researched static electricity problem solutions. I looked at anti-static mats, fabrics, meshes, straps, and booties. None of those ideas were immediately accessible to me. One writer suggested that those methods won't even work that well if a static spark does occur, since a spark is composed of high frequency spectral energy and any kind of wire will have a high impedance at those frequencies, and it is likely that the energy will jump through air to the nearest convenient conductor (like my mount or my camera) rather than take the wire to ground.
Finally I came across something I could try right away: fabric softener. Hey, even the Dollar stores in Quartzsite sell that stuff. I just mixed some with water in a spray bottle and started spraying all fabric surfaces, including the tent floor and the carpet under my desk / table. I also got some of the sheets you throw in the dryer, thinking those might be good wipes for the equipment.
When I started up the observatory last night, I took the extra time to spray all the tent walls and floor with this mixture, and to wipe down all the equipment. (It needed it, as there was quite a dust accumulation.) I wound up using a paper towel sprayed with the water / softener mix, since the sheets seemed to be leaving particles of some sort behind. It took maybe a half hour to get everything clean.
As expected, there were some hiccups getting all the equipment up and running. Try as I might I could not get the camera to connect in Maxim. I began wondering if I had zapped its electronics, but decided to do a complete power cycle on everything. I pulled the plugs on the mount and power supply and turned the computer off so everything was down to zero. Then I powered everything up and booted Windows. After a few unplug and plug cycles, everything was online, including the camera!
I went for broke and started up all the software: both observing planners, my focuser program, Maxim DL, MaxPoint, the mount software, and my planetarium program. All of it seemed happy and connected just fine. The mount was even reading the GPS time, after weeks of complaining about not being able to do that. (A few days earlier, I had figured out how to switch this feature on in the program.)
I loaded my pointing file for the western half of the sky and indexed on Alpha Peg, then Sigma Peg, and then over to Auriga where my first target would be, NGC 1960. Everything seemed to be working smoothly. I started a series of exposures at 40 seconds and just sat back and watched it go. Every time I got up to check something, I carried a damp rag with fabric softener with me and touched the tripod, floor, desk, chair, etc. before touching any equipment.
The data just kept coming in, one filter after another, and soon it was time to look for another object. That was easy because I had a few candidates loaded in Deep Sky Planner, so just a click and slew and I was on to the next cluster. This time I tried a 70 second exposure, the longest one yet, and was surprised at how circular the star images were. They were maybe a little elongated, but not bad. All the images were good and there were no tracking issues. The mount software just kept running smoothly in the background.
Finally, after a couple more targets, this time through AstroPlanner, I was getting tired. It was only 11:00 PM, and the Moon wasn't due to rise until 2:30 AM, but I had been up since about 5:00 AM that morning and even sitting at the computer was more than I wanted to do. So I decided to power everything down, this time in the right order, rather than as damage control in a crash landing. I made sure to save all the settings in my mount software and all my observations in my planning programs, and buttoned up the observatory for the night before midnight.
A few surprises: Little did I know that two of the clusters I was imaging were M36 and M38 in Auriga. I was just seeing their NGC numbers in the planning software, but I knew they were special once I got my first images, because they were so rich. There must have been hundreds of stars in my images. During the afternoon I had downloaded data from the AAVSO Photometric All Sky Survey (APASS) and noticed that NGC 1960 had over 800 stars in the downloaded file. Now I have to figure out how to handle all of that data. I certainly cannot do that by picking them one at a time, like Maxim and even AIP4Win wants me to do.
Negative results on the static experiment would be encouraging, but to really nail it I would have to deliberately induce static by violating the anti-static regimen. Well, I did that accidentally by pulling on a sweater and then sitting down without touching the floor and table first. Sure enough, Windows complained. Luckily none of the equipment dropped out, but just the same that was a warning.
So I am happy with the way the night went, even though there were a few good hours left in it by the time I quit. I am optimistic that I can recreate this "golden" session by attention to details and careful procedure. Slowly my confidence in my tools and in my abilities is returning.