Category: Astronomy

Exploring the cosmos

Kaʻohe Observing Site

Looking for a site that is a bit closer to home than driving all the way to the Mauna Kea VIS? Maybe not quite as high up the mountain, not as cold or windy? There is not a lot to choose from on Mauna Kea, much of the land is controlled access, either DLNR or private ranch land. Locked gates are the standard solution around the island.

Hualālai from Kilohana
Looking towards Hualālai from Kilohana, a heavy layer of vog sits just below

There is a gate that is generally not locked. The hunter check-in station at Kilohana that provides access to the Kaʻohe game Management Area. Starting at 5,700 feet from the Old Saddle Road the R-1 road climbs the mountain from here.

The actual spot I use is a staging area used by DLNR crews, hunters and the ATV riders who normally frequent the area. From the neat lines of pine trees it looks like the site was once a homestead or ranch house of some sort built high on the side of the mountain. It is about 1/4mile above Old Saddle Road and the Kilohana hunter check in station and directly adjacent to the R-1 road.

As usual you need to obey DLNR rules for access to the site. The R-1 road is designated a public access trail under the Nā Ala Hele trail system, so a permit should not be required. You must not be “camping”, this is defined by the DLNR as being in possession of “camping paraphenalia”, like sleeping bags, tent, etc., during the hours of darkness.

There is a sign in and out form at the hunter check-in station. The DLNR states that 4WD is required to use the R-1 road, but in reality the old homestead could be reached by any vehicle, the first part of this road is quite nice, basic gravel, the rough stuff is far higher up the mountain.


The site has many advantages. It is just far enough off the Old Saddle Road as to avoid vehicle headlights. Not that there is much traffic on the old road, the new road has accommodated most of the across island traffic and it is miles below the site.

One of the best features of the site is shelter from the strong trade winds that sweep across the island.  The trades are generally from the northeast, while the site is on the southwest flank, sheltered in the lee of a 14,000ft mountain.  I have seen days when the trades were howling in Waimea and Waikoloa, while it was dead calm at Kaʻohe.

You can get some fog and dew here in the evening. At 5,800 feet elevation you are just at the top of the inversion cloud level, sometimes just below. When it is clear it is glorious here, but you can get evening fog until the cooling night allows the sea breeze to wane and the cloud level to subside. You can always pass the site up and head on to the VIS if the cloud tops are higher.

Obsession at Kaʻohe
The 20″ Obsession telescope being set up at Kaʻohe, on the side of Mauna Kea

As with any site on the slopes of Mauna Kea, air currents around the mountain can cause some seeing issues. The site should be less susceptible to cold down slope flows than the VIS area as it sits upon a ridge line, not a depression.

The game management area can occasionally be closed to access by the DLNR for one reason or another. You can check the DLNR website or the Nā Ala Hele trail system webpage. Closures should also be marked at the hunter check-in station.

The site is most easily reached from the new Saddle Road (Daniel K. Inouye Highway) in the valley below. Turning up the old road near milepost 42 and driving one mile up to Kilohana. If you see the girl scout camp you missed the turn by a bit.

I have used the site many times, and have also observed from the nearby Kilohana Girl Scout Camp, and been very pleased with the observing. I suspect I will use the site again in the near future.

Directions from Waimea

The gate into the Kaʻohe Game Management Area and the start of the R-1 road at Kilohana
The gate into the Kaʻohe Game Management Area and the start of the R-1 road at Kilohana
  • Drive south on the Mamalahoa Highway towards Kona
  • 6.2 miles from the Lindsey road light you will reach the old Saddle Road intersection, turn left uphill
  • Proceed 10.2 miles to the Kaʻohe GMA entrance with a sign and yellow gate, the signs also say Kilohana Hunter Check-In Station
  • Proceed 0.2 miles on the dirt road to the site, the site is on the left in front of the pine trees

Directions from Kona

  • Drive 24 miles north from Kona on the Mamalahoa Highway (upper road)
  • Turn right on Saddle Road (Daniel K. Inouye Hwy.)
  • Proceed 9.6 miles on Saddle to the Old Saddle intersection
  • Turn left onto the Old Saddle Road
  • Proceed 1.1 miles to the Kaʻohe GMA entrance with a sign and yellow gate, the signs also say Kilohana Hunter Check-In Station
    Proceed 0.2 miles on the dirt road to the site, the site is on the left in front of the pine trees

Directions from Hilo

  • Drive across island on Saddle Road (Daniel K. Inouye Hwy.) to near milepost 42
  • Turn left up the old Saddle Road
  • Proceed 1.1 miles to the Kaʻohe GMA entrance with a sign and yellow gate, the signs also say Kilohana Hunter Check-In Station
  • Proceed 0.2 miles on the dirt road to the site, the site is on the left in front of the pine trees

Solved! 40 Year-old Mystery on the Size of Shadowy Galaxies

W. M. Keck Observatory press release…

Using the world’s largest telescopes, researchers discovered ancient cold gas clouds larger than galaxies in the early Universe. The discovery was announced today at a press conference at the 227th meeting of the American Astronomical Society in Orlando, Florida.

Gas Cloud Measurement
Artists impression of the power of background galaxies to measure the size of gas clouds as compared to the conventional method of using quasars. Credit: Adrian Malec (Swinburne University) and Marie Martig (Max Plank Institute)
The discovery, led by Associate Professor Jeff Cooke, Swinburne University of Technology, and Associate Professor John O’Meara, St. Michael’s College, has helped solve a decades-old puzzle on the nature of gas clouds, known as damped Lyman alpha systems, or DLAs.

Cooke and O’Meara realized that finding DLA gas clouds in the line of sight to background galaxies would enable measurements of their size by determining how much of the galaxy they cover.

“Our new method first identifies galaxies that are more likely to have intervening DLA gas clouds and then searches for them using long, deep exposures on the powerful Keck Observatory 10m telescopes on Maunakea and deep data from the VLT 8m telescopes in Chile,” Cooke said. “The technique is timely as the next generation of giant 30m telescopes will be online in several years and are ideal to take advantage of this method to routinely gather large numbers of DLAs for study.”

DLA clouds contain most of the cool gas in the Universe and are predicted to contain enough gas to form most of the stars we see in galaxies around us today, like the Milky Way. However, this prediction has yet to be confirmed.

DLAs currently have little ongoing star formation, making them too dim to observe directly from their emitted light alone. Instead, they are detected when they happen to fall in the line of sight to a more distant bright object and leave an unmistakeable absorption signature in the background object’s light.

Previously, researchers used quasars as the background objects to search for DLAs. Although quasars can be very bright, they are rare and are comparatively small, only a fraction of a light year across, whereas galaxies are quite common and provide a 100 million-fold increase in area to probe DLAs.

“Using the galaxy technique, DLAs can be studied in large numbers to provide a 3-D tomographic picture of distribution of gas clouds in the early Universe and help complete our understanding of how galaxies formed and evolved over cosmic time,” O’Meara said.

Mercury at Inferior Conjunction

Today Mercury will pass through inferior conjunction. The planet will reappear in the dawn during the last week of January.

There will be a lovely conjunction with Venus starting in early February with Mercury and Venus staying fairly close, less than 5° most of the month. On the morning of February 6th the pair will be joined by a crescent Moon for a lovely trio. As this occurs around maximum elongation for Mercury the conjunction will be about 25° from the Sun and well up in the dawn sky.

Mercury Events for 2016
  Date UT Separation Magnitude
Morning Feb 7 25.6°W +0.2
Evening Apr 18 19.9°E +0.4
Morning Jun 5 24.2°W +0.7
Evening Aug 16 27.4°E +0.6
Morning Sep 28 17.9°W -0.2
Evening Dec 11 20.8°E -0.2
 

Source: Mercury Chasers Calculator

Observing from Kaʻohe

A beautiful night on the side of Mauna Kea!

GyPSy in the Night
The 11″ NexStar GPS telescope, GyPSy set up at Ka’Ohe
I have been observing from the driveway quite a bit lately. But I really wanted to escape the neighborhood lights and get some real dark time. Add the vog factor, a thick layer was dimming the stars as seen from lower elevations. A few thousand feet of altitude would solve a lot of problems.

I needed some altitude! But I did not want to go to the VIS, it was cold and windy up there. A compromise was decided upon, if the clouds proved low enough I would go to the Ka’ohe site on the old Saddle Road. Only 5’800 feet elevation is a compromise between getting above the clouds, it is usually just high enough, and staying warm. On the west face of the mountain the winds are usually mild. This is only the second time I have used the site. Not that the site is new, I had noted this place as a possible observing site many years ago, it is only recently I have begun using it.

I have also been working on the ‘scope a bit. Now over a decade old the 11″ NexStar is in need of some TLC. A replaced GPS battery, a new power connector in the base, a little lube in the slip rings, a repaired solder connection also in the slip rings, etc., etc. She is working pretty well now, the GOTO system hitting target after target with precision. Thus I was looking to use the 11″ instead of the 18″, though this limited my magnitude a bit. I set up my observing lists for a maximum magnitude of 13.

What to observe? Just query my observing list generator for a list of whatever I have not observed in the area. I usually work in 30° x 2 hour section of the sky. This evening would see me south of Orion in Lepus, Eridanus, and Columba. What I did not expect is that everything I had not observed down there was a small, dim 12-13 magnitude galaxy! Everything!

NGC1993 Small, very faint, round 1′ in diameter, stellar core

NGC2089 Small, faint, round 1′ in diameter, stellar core

So it went, galaxy after galaxy, the variation was usually some version of faint… “Faint”, “Very faint”, “Quite faint”, to the limit of my vision “Averted vision required with the 28cm”. A bright star or another galaxy in the same field was exciting!

Normally when working a region of the sky I find quite a few plain objects, the usual slew of dim galaxies when off the galactic plane, open clusters in the plane. Usually there is the occasional gem sprinkled in to liven the observing session. Not tonight!

Still, it was very nice to be out under the stars. It was a completely dark night, the sky brilliant with Orion and Canis Major high overhead. I was sitting just at the top of the cloud deck, the cars far below me on Saddle Road creating a dim glow in the clouds. Across the top of the clouds I could see Mauna Loa and Hualalai lit by starlight and skyglow.

A solid three hours at the eyepiece, three pages of notes, and I was out of hot tea. I put down the unending list of dim galaxies and just spent a bit looking up some old favorites. The Orion nebula was stunning in the eyepeice, R Lep is still very, very red. Finally breaking down and heading home, I was in bed about midnight.

A Precipitation Sensor

Getting rain or snow on the primary mirrors is bad.

Open Dome
The Keck 2 primary mirror
The normal method of detecting conditions that might lead to rain or snow is by monitoring the humidity or dew point. If the dew point approaches the current temperature, to within a few degrees the operators must close the domes. This is much the same thing as the humidity approaching 100%. Thus I have installed several new humidity/dew point/temperature sensors over the last few years. These replaced some old and troublesome equipment that had been in place for over a decade.

The problem… You can have both rain and snow occur with low humidity. Moist air above the telescope can produce rain or snow which falls into drier air at the summit level. This can catch the operators by surprise, a situation we have observed on a number of occasions.

To help detect this you can deploy a precipitation sensor, something some of the neighboring telescopes have done. The engineers over at CFHT were kind enough to show me the units they had installed during their remote operation project.

Keck Weather Mast
Various instruments atop the Keck Observatory weather mast
Yes, I just went out and bought one. Not just any old unit either… The best precipitation sensor I could locate on the market, a Vaisala DRD11A. The sensor uses a capacitive detection method. Moisture on the top of a plate will change the capacitance and trigger the sensor. The plate is tilted to allow rain to run off and heated to melt snowflakes and sleet. testing on my work bench showed this to be pretty effective and quite sensitive. Yes, you can visualize me sitting at the bench dripping water on a sensor… It worked.

Not that the project was finished there… The new sensor does not come with any sort of network interface. Rather surprising given that just about everything else Vaisala sells has either a serial interface or an ethernet interface. This sensor has just a couple simple outputs… A logic level indication of precipitation, an analog output representing roughly how much, and a frequency output representing the same thing. I needed to interface this unit to the network. As I have installed a terminal server in the rack below the weather mast, at the minimum I needed a serial port.

While I was at it there are a couple other little devices I want to install on the weather mast. These need a network interface as well. May as well put together another little PIC controller and assemble it all together in one neat little package. a few evenings of coding and I had my solution, an interface that allowed remote computer control and status read-back. How many microcontrollers do I have performing little tasks at the summit now? Quite a few.

Cassini’s Optics

I have always enjoyed learning about the history of astronomy, it is a science whose roots can be traced continuously back to the dawn of human history.

One of my Facebook friends is a bit of an old telescope nut, even more so than myself, regularly posting photos of historic observatories and in particular old refactors. I too have a soft spot for these historic instruments, going out of may way to visit Greenwich Observatory in London, to drive up Mt. Hamilton to see the beautiful old refractor at Lick Observatory, or flying across the country to see one of William Herchel’s telescopes on display at the Smithsonian.

Ovidiu Cotcas recently posted a link to a fun research paper analyzing the telescope optics of Cassinni’s telescopes. These instruments were state of the art in the mid-1600’s, a period when the first telescopes were being used to provide the first good look at astronomical objects, revolutionizing our understanding of the universe. Only five decades after Galileo astronomers across Europe were attempting to build ever better instruments to provide views of the planets that had only recently been nothing but moving lights in the heavens. These early telescopes showed that planets were worlds, opening a whole new realm to observation and study.

Paris Observatory XVIII Century
Paris Observatory in the times of Cassini during the late 1600’s showing the very long focal length refracting telescopes of the day. Credit: Wikimedia Commons
Prior to the invention of the achromatic doublet in 1758 the main limitation of refracting telescopes was chromatic error. A single lens is also a prism, focusing the different colors of light at different focal lengths. The only solution to this was to make objective lenses with very long focal lengths. Today’s telescopes use compound lenses of two or three elements in the objective with different types of glass. This combination of lenses can be cleverly arranged to cancel out chromatic error resulting in an achromatic lens.

The long focal lengths of those first singlet lens telescopes appear absurd by modern standards, huge instruments with long tubes suspended from masts or with the objective lenses mounted upon tall towers while the observer and eyepiece were at ground level. Telescopes were thirty or even a hundred feet long. Unlike today’s convention of referring to a telescope’s aperture, telescopes were referred to by focal length. Cassini’s primary instruments had focal lengths of between 17 and 40 feet, with one having the incredible focal length of 150ft! As familiar as I am with using small telescopes I shudder at the challenges of aligning and aiming such an instrument, much less tracking a target across the sky.

Continue reading “Cassini’s Optics”

Venus and Saturn

On the morning of January 8th and 9th Venus and Saturn will be quite close in the dawn.

Moon and Mercury
The Moon appears as a thin crescent beside the planet Mercury, photo taken from the summit of Mauna Kea on 12Oct2007
Tomorrow morning the two can be seen rapidly closing upon each other, less than 3° apart. A slim crescent Moon will be only 4° above Venus making for a lovely trio in the dawn. The morning of the 7th will also feature a nice trio, with the Moon now below the pair, closer to the horizon.

As the pair rises on the morning of the 8th they will be only 32′ apart, easily close enough to fit in the low power field of most amateur telescopes. The morning of the 9th will see the pair again close, only 34′ separation. They will slide past each other much closer, about 5′ apart, but this will not be visible from the central Pacific as it occurs around 11:42 HST on the 8th, while the planets are below the horizon.

Moon, Venus and Saturn

Tomorrow’s dawn, January 6th, will see the Moon, Venus and Saturn in a nice conjunction. A beautiful 12% illuminated crescent Moon will be a bit over 4° above Venus shining brightly at -4 magnituide. Saturn will be another 3° below Venus. As an added accent the bright star Antares will be 6° south of the trio.