Tuesday, 29 May 2012

A different look

From the Moon. The Lunar Reconnoissance Orbiter camera recorded the following image of the Earth with the shadow of the Annular Solar Eclipse in May 2012.

http://lroc.sese.asu.edu/news/index.php?/archives/576-In-the-Shadow-of-the-Moon.html

Even though the Sun was shining around the Moon, there is a distinct shadow seen in the cloud tops as the shadow moves across the Northern Pacific Ocean.

Coronado Telescope Photography

Taking pictures of solar eclipses and transits is a challenge. And it becomes even more challenging when using a hydrogen alpha telescope such as the Coronado PST (40mm). The problem is that you cannot simply attach the camera body to the telescope. The focal plane is below the image plane.

To fix that situation I use negative projection. A Barlow lens is used between the camera body and the telescope. The Barlow lens extends the focal plane out further (increasing the resultant magnification by making the focal length longer).

Here is what the Transit of Venus looked like in 2004 through the camera. I had only a 2x Barlow lens and the camera body attached.

Full frame view with Coronado 40mm telescope and 2x Barlow lens negative projection.


Transit of Venus 2004 in Hydrogen Alpha (Coronado 40mm)

An excellent description of negative projection is provided here.
http://www.licha.de/astro_article_barlow_lens_projection.php

What is needed is a DSLR camera body, a Barlow lens, a T-adapter, a good mount to hold it all steady, and a cable release.

Anyone attempting to use this type of set up is strongly recommended to practice as much as possible. Focus is difficult, the amount of light you see through the DSLR viewer is reduced, and the weight of the camera attached to the rear makes balancing a challenge.

So here are a couple of tips.
1) Use a dark color blanket or towel to cover your head and the view through the camera. The darker the better as it will greatly aid in focusing and centering the image.
2) Use a strong mount - as strong as you can carry to the site. And plan to add counterweights as needed.
3) Fine adjustments to focus will be needed through out the event. Check and re-check the focus.
4) Remember to adjust the etalon to see different views of the prominences and filaments that may not be clearly visible through the camera.
5) Vary your exposures and combine the images later with a computer.
6) Have fun and don't forget to enjoy the views.

A solid mount is essential when photographing. The Orion German EQ used here pushed the luggage limits.


Monday, 28 May 2012

Preparing for Travel (again)

Here we go again. Off to another location to view an astronomical event. This time, the Transit of Venus.

The Transit of Venus is a "Not To Be Missed" event that is not very spectacular, just rare. There will not be another Transit of Venus until the year 2117. That's over 100 years from now in case you missed seeing that extra one in the year date.

We are going to Polynesia. The Paul Gauguin cruise ship leaves Saturday from the island of Tahiti. On Tuesday, when the Transit of Venus is visible, we will be on the island of Bora Bora with a small suite of telescopes. I will be the on board astronomy expert.

So now we are packing in preparation to leave soon. Or more correctly, Denise is packing. I've already packed the telescope and camera gear. Since returning from California there has not been a clear sky and the equipment never got completely unpacked.

Our telescope collection will include my 40mm Coronado solar telescope and a pair of Orion Dobsonian mount reflectors equipped with solar filters. I will be running the telescope show and assisted by Denise and several crew members of the ship.

The proposed set up location is at the tendering dock where cruise ship passengers embark and disembark. While waiting for the tenders they can take a look through the telescopes and see this very rare event take place.

The location will allow us to see the ingress shortly after noon. Egress will not be visible as the Sun will have set beforehand. Hopefully we can get some good timings of the ingress event to share with others at http://transitofvenus.nl/wp/ and http://transitofvenus.org/

Clear sky!

Saturday, 26 May 2012

Next - Transit of Venus

The next shadow to cross the Sun will be that of the planet Venus. This event is similar to a solar eclipse however the shadow is a mere dot. At closest approach Venus is a mere 1/32 the size of the Sun when viewed from the surface of Earth.

The image below shows Venus crossing the Sun in 2004. A nice round dot against the solar surface. A Coronado hydrogen alpha telescope (40mm) was used with a digital camera (Canon) and Barlow lens to capture the image.


The last transit of Venus visible from Earth was in 2004. Prior to that, the last transit was in 1883. There were NO transits of Venus during the 20th century. That means no astronomer alive today had seen one prior to 2004.

Here we are, eight years later and another one is about to occur. That doesn't make them seem rare until you think about the fact that the next one will not be visible until the year 2117. That is over 100 years from now!

So if you are able to see it, do so. It is a once in a lifetime event (twice if you saw the 2004 transit). To find out what time it will be visible, visit the following web calculator site for the When given a location.

More information about the Transit of Venus can be found at: http://transitofvenus.nl/wp/ and http://transitofvenus.org/

More Pictures from Mt Shasta Lake dam

Bill Kramer sharing the view through the 40mm Coronado Hydrogen Alpha Solar Telescope

Bill Kramer, Clint Werner, and Donald Abrams enjoy the eclipse view

My eclipse "chase" started with a contact from Clint and Donald about possibly coming to California to join them for the May 20th Annular Solar Eclipse. After talking it over with my wife, Denise, we decided to go for it. It was to be a week and a half before we leave for Polynesia to see the Transit of Venus (from the island of Bora Bora, not Tahiti like Captain Cook) and the air travel didn't suit my tastes, but hey, for an eclipse? Why not?!

Off we went to California. Clint and Donald had arranged a room for us in Anderson California and we were to decide on a viewing location the night before the eclipse based on weather reports. The entire area was showing clear sky potentials so we opted for an easy place to achieve - Mt. Shasta Lake Dam. A park area is well groomed near the dam and it was a perfect location for observing the eclipse. (see previous blog entries with pictures)

Clint and Donald's friends and business associates were also invited which turned out to be a very eclectic group. We had an impromptu picnic in the park with fresh food from a variety of sources and enjoyed our new group of friends.

An annular eclipse is normally not worth flying to see. That has been my rule of thumb in the past. I'd like to modify that with a corollary: except to join a group of eclipse chaser friends with many eclipse novices. It was worth a couple hours in an airplane for that. We enjoyed ourselves immensely.

Thursday, 24 May 2012

Lots of good results

Seems that a good number of people were able to watch the eclipse on May 20th in the States. Pictures are appearing at a number of web sites and at www.eclipse-chasers.com we are seeing an increase in the number of new eclipse chasers being added to the log.

While an annular eclipse is not nearly as fascinating as a total solar eclipse, it is still a lot of fun to observe. Many of the people with us for the eclipse had never seen a solar eclipse, of any kind, that they could remember. For them, the annular was almost magical.

Now we are looking forward to the Transit of Venus. I will have some more notes about that appearing soon. Clear sky!

Monday, 21 May 2012

Great eclipse at Shasta Lake

We set up our gear with some friends at Shasta Lake near the dam that creates the lake. A beautiful setting with a nicely cut lawn, near by restrooms, and an amazing view.
Numerous friends from California joined us and we had a lovely day in the park, enjoyed a great picnic, and saw the entire eclipse.
A narrow walkway was where we set up the telescope and camera. The wall along the walkway was the perfect ledge to lean against and watch the show.

Denise took these images through the camera and 400mm lens with solar filter.






Sunday, 20 May 2012

Blue Sky

There is nothing quite like the good feeling an eclipse chaser has when waking up to a blue sky near the eclipse viewing location. We are in northern California and it looks like we will have a good view of the eclipse so long as we stay near Redding. Further north looks dicey at this point in time when using the satellite to see where the clouds are moving.

Nearest clear sky clock I could find for our location is Cottonwood. It is showing a favorable model, but the time for models is done - now is the time to be checking the sky and using satellite views to look over the horizon.

Our plans are to be at the Lake Shasta Dam however; we've heard that might be a very popular destination. We have had at least one person in the group voice the opinion that staying on the hotel grounds will be fine. The last annular eclipse I saw, we did just that - in 1994 in Toledo Ohio. Of course, Toledo Ohio doesn't offer the potential views of mountains over a lake. Location to be determined soon.

As a note to anyone looking to buy solar filters today - forget it. Unless you know someone with extras, just plan on borrowing a filter for a quick view or watch the shadows under the trees.

Friday, 18 May 2012

Weather Prospects

As we get even closer to eclipse day, weather watching becomes important. A web site devoted to weather models and information for the eclipse was put together by expert eclipse chaser Jay Anderson. You can find links to various tools and images from satellites showing cloud fronts at that site.

Watching local weather reports the day before the eclipse can sometimes be helpful. Most weather reporters are simply reading the script provided by some of the weather models and data centers in Jay's list. In all my eclipse chasing experiences only one weather reporter hit the nail on the head. That was back in 1999, in Germany, where the local weather report was horrible. There were a few patches of blue sky - but they were very few. Most of the sky was cloud. The cheerful weather reporter from Munich stated that the holes in the clouds could allow those that are lucky to see the eclipse - and we were indeed quite lucky!

Thursday, 17 May 2012

Out of solar filters?

If you waited until the last minute to try and find some solar filters for the annular solar eclipse or transit of Venus, you may have waited too long. As a favor to someone overseas who I will join for the transit, I was trying to find some material to construct simple solar filters for 10" and 12" telescopes, but could not locate any with ease.

After much asking around, I contacted High Point Scientific and they reported a few sheets left. With luck, they will arrive before we depart for the transit.

Joe Cali has written an excellent tutorial of how to construct a solar filter mount using thin solar filter film. Using foam board for large telescopes may be a bit excessive - I suspect we will use cardboard or what ever we can find on board the ship - and duct (gaffer) tape - the astronomer's best friend when it comes to securing filters to the tube.


Wednesday, 16 May 2012

Airline limits

One of the biggest hassles of travel to solar eclipses is the limitations put on luggage by the airlines. It was not that long ago one could carry 70 pounds (almost 32 kilos) per bag of any size. That made moving tripods and counter weights easy. Now - 50 pounds (25 and a half kilos) is the limit. And to make matters worse, you are charged for extra bags on most airlines --- and you cannot carry on much. Now I hear that some airlines are going to start charging for carry on bags. This presents new challenges to eclipse chasers who want to capture images.

Maybe I should just bring binoculars and solar filters.

Packing up

Getting ready to head out to the annular eclipse. Denise and I are going to California to view it with some fellow eclipse chasers. This breaks my normal rule of thumb that an annular solar eclipse is worth driving to see, but no more. We are flying to California - then driving.

Over the past few weeks I've received a number of messages from people located in southern California who wonder if it is worth the drive up to the northern part of the state to view the annular solar eclipse. If this was a total solar eclipse, the answer would be a resounding YES. But this is an annular solar eclipse. While the light of the Sun will diminish, it is nothing like a total solar eclipse - not even close. It is more of a teaser for those of us that have seen total solar eclipses.

So why drive up to see it? The only reason to consider such is if you are an amateur astronomer or a photographer who would like to see the "ring of fire" as some have called it. It is not something you can look at without eye protection, you will need the same solar filter that can be used to view a partial solar eclipse. That means that most people in the southern CA region should elect to simply enjoy a deep partial solar eclipse. If you have a solar filter, share it with others as you watch the Moon almost completely cover the Sun with a dramatic crescent shape as in the following image.


What will one see in northern California? Something more like the following image.


To make these images, in 1994, I had driven to Toledo Ohio and set up a small telescope (Questar) with a full aperture glass solar filter. The filter I used creates a pleasing orange/yellow image of the solar photosphere showing sunspots in fair to good detail when they are visible.




Monday, 14 May 2012

Location-Location-Location

Picking a location for viewing a solar eclipse is not always easy. There are several things to consider. First and foremost is a clear sky. Viewing a solar eclipse under clouds is not desired. So when selecting a location, include a back up location or two in case the weather is not cooperating. Of course, that information may not be easy to get until the day of the eclipse and then it can be too late to re-locate. So let's concentrate on the surrounding environment (working under the assumption of a clear sky).

1) Comfort - the entire solar eclipse event lasts several hours. Being outside for the entire duration requires break areas such as restrooms, shade, and maybe even refreshments. For this reason my preference is a lawn in a public park with a nice vista view in the direction of the eclipse.

2) Access - most people will not want to climb a mountain or "go bush" style for an eclipse. That said, I do know several people that enjoy that sort of eclipse chase. So this is for the majority that want to park someplace, enjoy the eclipse, and have easy access to their vehicles. Locate the viewing area with easy access to parking.

3) Shadows - the most interesting shadows occur during the partial phases. Having trees nearby that allow pinholes of light to strike the ground make for great shadows. If the shadows hit a lightly colored surface then that is all you need. Otherwise, a blanket or towel spread out under the shadow works great. Depending on the climate, having a shady spot to check out every so often is a good thing.

4) Audience - setting up a telescope in public is always interesting. Sometimes you will attract others who want to see what is up. If that is not desired, then find a place that is somewhat shielded from others passing by. Otherwise plan a queuing system if you think you will have more than one or two onlookers show up. As the eclipse reaches climax you will want to take over the optics - be sure your audience knows that in advance. There is nothing more frustrating than having someone nudge you aside for a look through the telescope at the wrong time.

5) Power - do you need electricity for your rig? If so, then selecting a location with power is paramount unless you plan to transport batteries.

6) Web access - do you need web access for your phone or PC? Finding an outside location that is not a parking lot (hot pavement) with web access could be challenging. Or plan on using a phone based service.

Wednesday, 9 May 2012

Large Sunspot Today

There is a large sunspot visible today. It is about the same size that Venus will appear during the transit. It is an excellent chance to practice your photographic set up in preparation for the transit of Venus this June.

Sunspots are darker areas visible against the solar disk. The darker areas are still quite bright, just not nearly as bright as the photosphere - the part of the Sun you normally 'see'. Hence they appear dark.

Saturday, 5 May 2012

Full Moon Perigee

This evening the Moon is full and at perigee. That means it is at the closest point in its orbit (the orbit of the moon is not a perfect circle) about the Earth. So if the Moon looks a bit bigger tonight, that is because it is bigger - about 14% bigger.

During the next new moon phase there will be a solar eclipse. It will be an annular eclipse where the Moon's disk will not completely cover the Sun's disk. The reason? The moon will be at its further point in its orbit about the Earth (the other side).

Don't do it yourself (2)

Some more solar filter myths that need busted!

1) Mylar blankets - some solar filters are made from Mylar materials. Mylar is a trademark of DuPont (more information) and not all things called Mylar are exactly alike. Mylar solar filters contain additional protection. This means you should not use Mylar unless it is designated as a solar filter!

2) Blank CDR - while mostly opaque these devices are not suitable solar filters. They allow radiation through that can damage your eyes. Don't use them, get some solar filter glasses instead.

3) Stacked sunglasses - are not a suitable solar filter. Not only is the view distorted, there is a chance of eye damage. Use solar filter glasses instead.

4) Welder's glasses - shield a lot of the visible light but not the radiation in the ultraviolet or infrared. These glasses are okay for a short glimpse of the eclipsed Sun but not for prolonged viewing. And they should never be used with optics such as a telescope, binoculars, or zoom lens.

You only get one pair of eyes. Keep them safe, use the proper viewing methods.