Category: Astronomy

Exploring the cosmos

Restoring an Orange Tube Celestron C8

It looked horrible! The paint was coming off everywhere with heavily corroded aluminum underneath. Most of the screw heads were small balls of rust, with hopefully enough remaining to fit a screwdriver to and remove. For a precision optical instrument this small telescope was not very encouraging.

Orange Tube Corrosion
Looking at what remains of the paint on an old Celestron C8 orange tube telescope
On the bright side the optics looked to be in decent shape. While there was some dirt and mold on the corrector, the primary looked almost perfect. Not bad considering the condition of the metal parts. Maybe, just maybe, this telescope is salvageable.

The telescope in question is an old orange tube Celestron C8. Thousands of these little telescopes were manufactured in the 70’s and 80’s. It was the C8 that set the standard for amateur telescopes at the time. The C8 is still in production forty years later, but the tubes are no longer painted orange as they were originally. Compact, yet offering decent performance, these telescopes were well regarded and hold a special place in the memories of many amateur astronomers. I have seen these little orange telescopes at dozens of star parties, even bolted to the side of huge professional telescopes for use as finders.

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Gravitational Waves

The confirmation of gravitational waves is simply a huge moment for science. A lot of people have spent their lives building instruments in hope for this day. From one who maintains another great scientific instrument to those who built LIGO… Congratulations!!

Not to understate the magnitude of the achievement, this is a huge discovery, but as usual XKCD puts a fun spin on the moment…

Gravitational Waves
gravitational waves by XKCD Randall Munroe, creative commons licence

Total Solar Eclipse March 8, 2016

On March 9, 2016 a total solar eclipse will sweep across Indonesia and into the central Pacific. This will be an late afternoon eclipse, with maximum occurring just before sunset at around 17:37 HST (5:37pm HST).

1999 Total Solar Eclipse
The 1999 Total Solar Eclipse from France, image credit Luc Viator
The path of totality passes well north of the Hawaiian Islands, just south of Midway Island. If you want to see this eclipse as a total your best bet is an eclipse cruise. For the islands this will be a deep partial eclipse, ranging from about 67% for Kauai and the around 55% for the Big Island. Of course, the exact amount of the Sun covered by the Moon will depend greatly on your location. See the table below for predictions and timing for your location.

Note, you might be confused by some references that state the eclipse occurs on March 9th. It does occur on the 9th! For our islands greatest eclipse occurs around 03:30 on March 9th universal time. If we convert to Hawaiian Standard Time this will be the 17:30 (5:30pm) on the afternoon of March 8th. You must remember that universal time is ten hours ahead of Hawaiian Standard Time.

Eclipse 20160309
Diagram of the March 9, 2016 Total Solar Eclipse
There are several cruises scheduled to intercept this eclipse. Most look to observe the eclipse somewhere near Indonesia, where the eclipse will be at its maximum. This is where you will find the hardcore eclipse chasers, including a few island folks I know. Most of us will just have to settle for seeing this eclipse as a partial, including myself. The information presented here covers viewing the eclipse from the islands.

A deep partial can be very interesting. Even people not expecting the eclipse may notice a dimming of the Sun and an odd, subdued nature to the sunlight. Even a quick glimpse of the Sun will reveal that half of the disk is covered. Eclipse glasses or a welding filter will provide a nice image of a partially eclipsed Sun. Tree leaves and other makeshift pinhole cameras will show crescent images of the Sun on the ground. For best viewing a small telescope with a solar filter, or a pinhole camera will allow excellent images of the eclipse. My standard eclipse viewing setup is a 76mm refractor with a Baader film solar filter. I assembled this gear for the 2012 Venus transit and it has seen several eclipses since.

Solar Eclipse Data for March 8th, 2016
  Mag Begin Max End
Hilo 55% 16:37 17:37 18:32
Honolulu 63% 16:33 17:36 18:33
Lihue 67% 16:31 17:35 18:33
Kahului 60% 16:35 17:37 18:33
Kona 56% 16:36 17:37 18:32
Mauna Kea 56% 16:37 17:37 18:32
Midway Is 97% 16:04 17:20 18:29
 

All times HST
Source: EclipseWise Interactive Map

 
The table at the right gives the eclipse timing for a few locations across the Hawaiian Islands. All times are given in Hawaiian Standard Time, just remember that 17:36 is 5:36pm in 12 hour time, just subtract 12.

As you can see the magnitude of the eclipse increases notably the closer you are (further north in the main islands) to the path of totality. The timing does not vary by nearly as much, with maximum eclipse occurring around 17:36 for the islands.

If you would like to see precise information for your location, or for someplace other than the islands, just use the interactive map and click on your location for data.

Partial Solar Eclipse
A partial solar eclipse from Kawaihae, 9 May 2013
Observing a partial solar eclipse requires proper eye protection. If you can not look safely, do not look! Even dimmed by 50% or more the Sun can cause permanent eye damage if viewed without proper protection. A solar filter is required for telescopic or binocular use. A good view can be had without magnification simply using a welding filter (shade 13 or darker) or solar viewing glasses to look directly at the Sun. A pinhole camera can be made out of things lying around in your kitchen that provides a very good image. Read my Guide to Safe Solar Viewing for a lot more information on viewing the Sun safely.

There are no further solar eclipses near the Hawaiian islands until 2031 and 2035, the path of totality for both of which pass well south of the main islands. There is also an annular eclipse in 2024, for which the center line also passes well south of the islands.

Safe Solar Viewing

You have heard it before, but it really is true! Looking at the Sun for longer than a few brief moments with an unprotected eye can lead to permanent damage. Looking at the Sun with any sort of optical deceive that has not been properly filtered can lead to instantaneous eye damage.

Sunspot AR2192
The complex sunspot AR2192 visible on 24 October, 2014

Discussed below are the only safe methods I am aware of to view the Sun. There are some dodgy methods out there. Take chance with your irreplaceable eyesight? I think not. Be careful and do it right if you want a look.

For the unaided eye there are a couple options to view the Sun safely…

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Cherry Blossom Festival Sidewalk Astronomy

It was a perfect day to do an astronomy outreach event. Of course as it was a daytime event, only one star is available for viewing in the telescopes… The Sun. Set up a few solar telescopes for an astro outreach event.

Josh Showing the Sun
Josh showing the crowd our Sun in the telescope
A simple plan… Set up in the lawn in front of Keck Observatory headquarters and wait for the crowds around the telescopes. Not that I have any illusions about our little outreach event drawing huge crowds. There is a method to my plan, we do this on the same day as Cherry Blossom Festival!

The festival guarantees a huge crowd of people for an outreach event, no advertising needed. The main part of the festival takes place along church row where the cherry trees are, next door to Keck headquarters. Much of the available parking is at the shopping centers on the other side of headquarters. There is a steady stream of hundreds of people right through our lawn. All we needed to do was to set up and be ready for a crowd.

A few friendly looking telescopes, a couple signs with the prominent word “free”… We had a crowd! As one would expect they came in surges, for four hours it varied between a few people at each telescope to a good sized line at every telescope, with up to fifty people gathered around at at time. We had three telescopes operating, two eight inch telescopes with white light filters and the Coronado PST providing a hydrogen alpha view.

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