Rambling travelogs from a world traveler

Wednesday, June 6, 2012

Yesterday's Solar Transit of Venus

 "It is better to ask some of the questions than to know all the answers." ~ James Thurber

Gentle Readers and Loved Ones,

As I've said before, I like amateur astronomy.  Yesterday's solar transit of Venus gave me an opportunity to exercise my inner geek. My 8" Orion Dobsonian Reflector has sat gathering dust for years now.  Yesterday, we resurrected it.  Katie helped me dust it off, clean the primary mirror and wipe the cobwebs out of the tube. Then we took it outside and started testing the solar projection method to view the transit.


Gentle readers, I am about to describe a process that is a very safe way to observe the sun.  However, if you don't know what you are doing, you can permanently blind yourself.  If you look at the sun through a pair of binoculars or a telescope directly, it will burn through your eye, out the back of your head and kill your neighbors.  Don't do this.

My telescope is a Newtonian reflecting telescope. It has an 8" diameter mirror at the base of the tube.  The surface of the mirror has been precisely ground to focus the light it collects into an image. There is a point in the tube where all that light is focused down into a point.  If you think a little magnifying glass will start a fire, you ain't seen nothing like an 8" disk focusing the sun. However, you can safely point the scope at the sun and hold a screen a good distance away from the eyepiece and it will project an easily viewed image that you can see even in bright sunlight.  In fact, I quickly learned I needed to go get my sunglasses to cut down on the dazzle. I checked frequently and the scope never got much more than warm.  The secondary mirror was the warmest part.

We started setting up about an hour before the transit started.  Our slashed together viewing screen using a cardboard box and some paper was a dismal failure as you can see here.

Then I remembered that I have a 30 year old movie projector screen rusting away out in the garage.  So I got it out and it worked great for people to look at visually.  However, I discovered the weave of the screen really makes for bad photos.  You'll just have to trust me that it looked really good in the bright sunlight to people.  I got it setup just in time to capture the beginning of the transit.  The little cut out at left center is Venus just moving in front of the sun.

This picture above is a close up of the first picture in this post. 

It was about this time that neighbors started noticing what I was doing and came over and asked to see.  This would continue until sundown. After about 20 minutes, Venus moved fully into view and we saw this.  Note the sunspots at the right edge of this picture. There are six of them.

Here is a closeup.  I'd love to tell you that the colors around Venus are an artifact of the sun shining through Venus' atmosphere but it really is just that my telescope mirror is old, oxidized and not collimated correctly.

The transit progressed and Venus moved across the sun.  I took some more pictures.

In this next picture, some clouds moved in front of the sun.

Once the sun moved behind the trees on the west side of the house, I had to move the scope out near the street.  By this time, we had called friends and family and we had a fun group watching the screen.  It is my sad fault that I did not think to get any pictures of the group.  We even had various joggers and dog walkers stop to look.

This is a closeup of the above shot.  Note the sunspots.

As the sun sank lower, the scope began pointing at the airplanes taking off and landing at MSP International.  Twice the crowd oooohed as a jet went directly in front of the sun and for a fleeting moment you could see it silhouetted.  None of use were quick enough or lucky enough to get a picture.

Later, just before sunset, the sun's image began to take on a sunset glow and Katie got this nice picture.  Soon after, the sun sank below the clouds you see and we were done for the night.

Prepare yourself for this next picture.  Katie says I look like a High School Science Fair geek posing uncomfortably for his parents.

On that happy note, I remain,

Dad / Geoff