Tuesday, April 26, 2016

This Year's Star Parties

It's once again time to start planning which star parties are worth the travel expense and time to attend. A big attraction of nearby star parties is their skies which can be much darker than those nearby, which are marginal at best or abysmal (like my back yard). But that's only one attaction. Let's look at the most important factors:
  • Sky darkness
  • Open horizons
  • Light domes
  • Programs
  • Amenities
  • Downsides

I would list ambience as a factor, but the truth is I've never been to a star party where the people have been anything less than great.

Here are some information about the ones I plan to attend this Summer and Fall:

Nebraska Star Party


I put off attending this because of the comments about heat and storms. What a mistake!
  • Sky darkness: Dark gray (the darkest zone possible). 
  • Open horizons: Excellent in all directions; the observing fields are surrounded by low hills. 
  • Light Domes: Only one dome worth mentioning, and it's a feeble one from Valentine (population 2700, 26 miles to the northeast.) The dry air seems to suppress domes.
  • Programs: Exellent. The Wednesday talks at the local high school are top notch with nationally known speakers.
  • Amenities: Campgrounds are available, as is primitive camping on the observing fields.  The observing fields are essentially "bring whatever you need," providing only mowed land with three pit toilets. There's no power or water (drinkable or otherwise). There are catered suppers on three nights; the food is basic but very good. Door prizes that range from very good to grab-bag stuff you'll donate to your local club.
  • Downsides: Prickly pear cacti will puncture unguarded feet and tent floors that aren't protected by ground covers. By day there are occasional biting flies and just enough mosquitoes to provide distraction. DEET up and it's fine. And don't forget the possibility of withering heat and violent thunderstorms packing lightning, wind, and hail. 
  • Hints: If you're concerned about the heat, make the half-hour drive to Valentine where the public library has WiFi and A/C! A great place to cool off. Also be sure to visit the showers at the nearby campground (bring quarters).
Summary: I'm going for the third time, despite never having won a door prize! If you don't mind the primitive conditions, heat, and threat of storms you should make the pilgrimage to NSP at least once.

Iowa Star Party


This is a personal favorite of mine, in part because I was a charter member of the host club and did my graduate study in nearby Ames.
  • Sky darkness: Light blue
  • Open Horizons: Excellent if you set up in the middle of the field.
  • Light Domes: There's a significant dome from Des Moines (population 611000, 50 miles to ESE). During humid conditions a few others can be seen. To the south, nothing.
  • Programs: Usually there's a talk by a scientist from one of the nearby universities and another by a host club member. These are given in an old barn which can sometimes be stiflingly hot and humid. 
  • Amenities: There's no power or water at the observing field, but power for recharging batteries can be had at one of the nearby buildings. There are a limited number of cottages and houses for those who want to sleep in comfort, and one is kept open during the day for those who seek respite from the heat. Saturday night there's a home-cooked supper that's always terrific. Door prizes that vary in quality from year to year.
    If you like hiking, horseback riding, and wildlife there's a lot to do during the day.
  • Downsides: Summertime heat and humidity have been insane the last couple of times I've attended. This year it's on the Labor Day weekend, so maybe it will be cooler. Pests are usually not a problem.
Summary: A nice sub-regional party with dark sky and pleasant surroundings

Heart of America Star Party


I've only been to this once, but it's a really well organized event with a lot of things going for it. Unfortunately the one time I attended it rained all three nights so some of my information is incomplete.
  • Sky darkness: Light blue
  • Open horizons: Excellent
  • Light domes: I think there may be one to the north from Kansas City (population 2 million, 50 miles N) and probably from Butler, MO (population 4100, 12 miles E)
  • Programs: Substantial--usually at least one speaker of national significance, another visiting from a university, and members' talks. These take place in a building with good A/V adjacent to the observing field.
  • Amenities: Limited field power; showers set up nearby, and good food aplenty. Food and drink are available throughout the night, as are activities (movies and bingo) for cloudy nights. Very nice door prizes.
  • Downsides: People like to pack together on the observing field, but there's ample room.
Summary: A superb gathering, well organized and attended. Usually in October, so it doesn't conflict with other major parties and is unlikely to be subjected to hot weather.

Saturday, April 23, 2016

Back into Planetary Imaging

I've been doing so much deep sky imaging over the last few years that I've neglected the solar system for almost three years! Last night I decided to do something about that and went out and imaged Jupiter.

One of the problems I'd had when planetary imaging was getting the mechanics of it to flow smoothly.

My polar alignment was never good enough, causing targets to drift and making it tough to use region of interest (ROI) imaging. ROI imaging lets you use a small portion of your sensor and get higher frame rates. For example, my Point Grey Research Chameleon gives only 15 frames per second (fps) at its full resolution. When that's reduced to 640 by 480 pixels it provides 24fps, and further narrowing of the ROI can get it up to 30fps.

One way around polar alignment problems is to use autoguiding. To make autoguiding work in this way you need to have a rough alignment (and I do mean rough: north and level is good enough unless you want to use very long focal lengths.) You also want to use the planet as your guide star. Doing so causes the rotation due to rough polar alignment to be around the planet's center. This keeps it fairly minimal over the time span of most captures.

This is based on about 230 frames out of 2300, processed using AutoStakkert 2.6 and Registax 6.1. FireCapture 2.4 was used for acquisition, and it worked much better than the version that was available in 2013. The scope was a C 9.25 with a 2X TeleVue Barlow (f/20, FL 4700mm), and the mentioned PGR color Chameleon. It's only a so-so image and has a number of issues caused by one or more (probably all) of the following:
  • Misalignment of optics
  • Rotation of Jupiter and motion of the moons (the video spanned a little over 1.6 minutes)
  • Poor seeing (which it was)
  • Lack of experience using AS!
Despite these problems it was good to get a not-awful image. What pleases me most about this image  is the natural color it has without the need for any tweaking. Back in the old days of using my TouCam colors never seemed quite right.

Saturday, April 16, 2016

Reducing Laptop Power Consumption

As I found out in an earlier post, my laptop uses about 2.1A when its battery is fully charged and about 5.6A when the battery is depleted. At typical lead-acid battery voltage (~13V) these translate to about 27 and 73 watts, respectively. This makes a laptop one of the largest drains on a battery when imaging. Is there a way to reduce this significantly?

The answer is definitely yes!  Let's start with a review of laptop power consumption as measured by another blogger. He found these amounts for a laptop very similar to mine:
  • Laptop off, battery charging: 54w
  • Laptop on, idle (display at full brightness, WiFi on, power management "balanced": 20w. 
Notice that an idle laptop that's also charging the battery will consume 74w, essentially the same amount I found. Your laptop may have different power use, but it will probably be in the same area.

Next he tried a few methods of reducing the power use with the following results:
  • Set screen brightness to dimmest setting: 4w reduction
  • Turn off hard drive: no reduction
  • Disable WiFi: 2.5w reduction
It's possible to completely turn off the display saving a little more (the specifics in in a moment). My guess is that powering down the display will reduce power by about 6w.

The total reduction by turning off the display and disabling WiFi is therefore about 8w or so. That's about 2/3A when running off a 12V battery, and over a four hour imaging session it will amount to 2.7Ah. That's not a big amount, but it's not insignificant. Recall that my summer star party standard was 16 hours of imaging. The saving in that amount of time is 10.7Ah.

So how does one turn off the laptop display? Luckily there's a tiny program for Windows that does just that. It's appropriately called "Turn Off LCD" and it can be found here. Unzip it, put the exe file on your desktop and double click it whenever you want to shut off your display. This does not affect any programs that are running; guiding software and image downloads will continue normally. To restore the display just move your cursor or hit a key.

You can assign the program to a key stroke if you wish. The way I've done this is to use AutoHotkey. Here are the steps needed to do that if:
  • Download and unzip Turn Off LCD, then move the exe file to the folder of your choice.
  • Download and install AutoHotkey
  • Right click your desktop and choose New / AutoHotkey Script. If this options isn't available it's probably because AutoHotkey isn't running; start it using the Start Button / All Programs / AutoHotkey / AutoHotkey
  • Add your hotkey specification after the script's boilerplate. As an example, here's my script for binding Turn Off LCD.exe to the key combination of the Windows key and s:
         run, TurnOffLCD.exe

    Note that I've renamed the exe file to omit the blanks because I don't like file names that include blanks (I was raised in the era of DOS 3 world of 8.3 file names, what can I say?) You may need to specify a path to the exe file--it's just prepended to the exe file name.
    You can bind the exe to any key you want; more information is provided in the AutoHotkey help. Read it and learn.
  • Save the script file with a name that makes sense to you. I called mine ScreenOff.ahk
  • Right click it and choose Compile Script. This will create ScreenOff.exe.
  • Move the compiled script to the Windows Startup folder so that it will be loaded every time your start your laptop.
  • Hit Windows + s to turn off the display. Move the cursor or hit any key to resume.
Remember to disable WiFi and Bluetooth if you don't need them.

Any software that you don't need should be disabled or turned off, as it will only make your CPU, HDD, and graphics adapter work harder and consume more power. Software that should be disabled while imaging includes all security software, Windows Update, and Windows Defender. If you're not on a network none of that is needed or useful.

Unless your laptop's CPU is slow and feeble you can change its power settings to run slower and use less power. Windows usually supports three modes: High Efficiency, Balanced, and Power Saver (the one you want.) Be sure your laptop's battery is fully charged before you take it into the field.

Do all this and you may be able to reduce your laptop's power consumption by 1/3 to 1/2.

Sunday, April 10, 2016

Messier Marathon Night Results

"Mission Accomplished!" to use a cliched phrase. "Goal Reached" might be a little better, or maybe "Dumbness Overcome."

This was one of my first attempts to use my DSLR in quite a while, and I managed to make a lot of mistakes early on:
  • Forgetting to return to ISO 1600 from the composing setting of 6400
  • Forgetting to set the shutter control to bulb
  • Forgetting to increase the number of frames on the DSLR controller from the dark frame to light frame counts
And so on. The evening began with starts and restarts, but once it got going it went well. The time I lost meant I wouldn't go after the dimmer planetary nebula I had included on my object list in the last post, but that was okay.

All the hardware worked perfectly, although some went untested. The dry air and the gusty to breezy conditions meant the dew preventers weren't needed. It was only around 2 A.M. that frost began to appear, and my scopes stayed clean until the end a little before 3 A.M. The DSLR power supply worked perfectly and the 35Ah battery was barely tested running that and the mount. I used my laptop for PHD with its power supplied by it's own battery augmented with a Duracell 600 battery pack. The Duracell ran down pretty far in the five or so hours, so this might not be a good option for multi-night imaging. For more power conservation I need to find a way to turn off the laptop's display, not simply dim it.

The evening tally was six Arp galaxies and one planetary. In terms of Messier objects it was 9 1/2. Let's see some marathon images:

Leo Triplet (clockwise from NGC 3526 at top, M65, and M66) Together these are Arp 317. M66 is Arp 16.

M49 (right of center, Arp 134)

M60 (left of center, Arp 116) and M59 (right of center)

M87 (Arp 152)

M90 (Arp 76) and M89 at bottom edge

M97 (Owl Nebula) and M108 at bottom edge

All the images are based on 10 three minute exposures with a Canon T2i (at ISO 1600) riding on a TV 102 operating at f/7--except the image of M90, which was 5 three minute exposures at ISO 6400 (see list of mistakes above). These were calibrated with 20 dark frames collected throughout the night as the temperature fell from around 30°to 20°F. They obviously haven't been flatted. I reprocessed them to include synthetic flattening, and now they look a lot nicer!

An inspection of single light frames shows that they surpass visual observations, so why not bring back the idea of an Imaging Messier Marathon? Three minutes at ISO 1600 is about the same as 45 seconds at ISO 6400. 3/4 minute times 110 objects is only 82 minutes; out of a six hour marathon night that leaves four and a half hours for acquisition and composing images. Definitely doable.

That aside, the evening bumped my Arp list count to 26 and my planetary list count to 23. Both lists are about 1/4 done!

Onward to warmer weather!

Thursday, April 7, 2016

Messier Marathon Plans

Tomorrow night is Messier Marathon night and it looks like it may actually be clear!

Considering what we often see for the MM, this will be relatively balmy (wind chills in the teens above zero) and dry (the observing field is a little mushy, but there's no snow). It helps that this year it's being held in April even if that's not best for getting a high count.

Having gone over to the imaging side, that's what I'll be doing. To keep in the spirit of things I'll do mostly Messier objects.

Because the Ms are fairly bright I'll be using my DSLR. The targets will be taken from the two Astronomical League lists I'm working on, Arp galaxies and planetary nebulae.

Here's the list, Galaxies first:
  • M49
  • M60
  • M65
  • M66
  • M87
  • M90
These all have surface brightness between magnitude 21.3 and 22.3, so I think they can be imaged fairly quickly for modest quality results; it is a marathon night. Because M65/M66 occupy the same field of a TV-102 and DSLR, they require only one image. So for the six galaxies I'm expecting four to five hours of clock time including time for acquisition, composition and dark frames.

Next the planetaries and their surface brightnesses:
  • M97 (22.3)
  • Abell 21 (24.9)
  • Abell 36 (25.5)
  • Abell 35 (26.2)
  • PN G164.8+31.1 (26.6)
You can see why the last four are not Messier objects; they're not very easy to see. Abell 21 is about three times larger than M97, making it a good target for the relatively short focal length TV-102 (700mm). Given its location in Gemini it might be the evening's first object and will get up to two hours of photons. The other dimmer objects will probably get passed over.

Sunday, April 3, 2016

A Battery Box Addition

The Battery Box got one refinement over the last couple of weeks: A built-in 7.5VDC power supply.

I had intended to use an external supply, but the little Drok unit gets good reviews and is much smaller than the adjustable supply I had planned to use. It was perfect for mounting within the box. All it needed was an output plug. For that I went with the same sort of plug used on many mounts, a lockable panel-mount socket and plug. (Both were purchased on eBay.)

Drok 12VDC to 7.5VDC step-down converter
5.5x2.1mm socket and plug
A built-in converter presents two problems if it's left connected to a battery: A continual power drain (0.1 to 0.12W) and possible interaction with a smart charger. The drain doesn't sound like much, but it equals about 7Ah per month; that's a lot for a 35Ah battery. To prevent these problems I isolated the converter using a rocker SPST switch. As a reminder to turn off the converter when it's not needed I added a tiny LED that draws a minuscule 3mA. Here's the switch and LED:

Switch and indicator light

As I said, it's a tiny LED! It's just bright enough to let you know that the converter is active.

12V sockets (above) and new 7.5V socket (below).
I made an extension patch cord that fits the plug and the power cord from the camera's dummy battery; this will permit me to use other power supplies.

One other add-on is intended to make this easier to use: An accessory cable for my charger that will let it charge through one of the sockets. Because this is a small battery it can be charged at a relatively low amperage of 1.1A. While I haven't yet recharged it from a state of deep discharge, I'm hoping that it will remain cool during charging even when left in the box. It's my hope to never need to remove the cover.

NEXT UP: It's the Messier Marathon, April 8 or 9! I plan on imaging some Messier galaxies as a part of the Arp galaxy imaging project. There are six Messier/Arp galaxies I haven't imaged yet: 49, 60, 65, 66, 77, 87, and 90. Only 77 is badly placed; it will set too soon for imaging. Because it's a marathon night, I'll shoot only luminance with my ST-8300M, and probably only an hour apiece at most using my TV102. Last year the MM had only so-so skies. Here in Minnesota we're overdue for some good Messier luck.