Tuesday, May 29, 2012

Yesterday's Sun...

Keeping with the astronomical theme as I prepare for the Venus/Solar transit next Tuesday I decided to do a little experimenting with different ways of photographing the sun. Of course all the methods shown here involve different methods of attaching the camera to the telescope but the one thing they all have in common is safe filtering. Please do not attempt to look at, photograph or in any way magnify the image of the sun without proper solar filtering.

The view through the spotting scope which is also solar filtered.This was taken by simply holding my small P&S camera up to the eyepiece and snapping the shot.
This first shot is one that will be familiar to anyone that read my post on the May 20th annular eclipse. This is the view through the spotting scope that is attached to the main scope. It's a simple straight through 8x finder used for broad pointing of the main scope. When an object is in the wide field crosshairs of the spotting scope it's generally dead center of the telescope eyepiece of the two have been properly aligned.

My rig set up in the backyard. That's my Canon 5DMII with the 100-400 lens piggybacking on top. Yes, It's filtered as well. Not too happy with the results from that setup.
In this shot you can see the camera is piggy-backed on top of the scope. The lens is a 100-400mm f4.5-5.6 with a 1.4x extender. The long end of the focal length being a 560mm f8 effective lens.
I really couldn't get a decent shot with this configuration besides the weight was just too much to be carrying on the top of the scope without any counter-balance.
My two trusty dogs had to get in the shot too. That's Sirius laying in the shade behind the scope and Bellatrix or Bella walking around the scope. She just wanted a view too....

Bonus for the first commenter to tell me the reason for my dogs names. I'll send you an 8x10 of either the annular eclipse composite or the composite I'm going to create from the Venus transit!

The camera attached via eyepiece projection. Images are soft. Need more patience....
This shot shows the camera attached to the telescope in a method called "eyepiece projection" because there is an actual eyepiece between the camera and mirror which adds to the magnification of the image.

There are advantages and disadvantages to photographing using this method. The big advantage is the extra magnification so you do not have to crop and zoom in on images to get decent closeups of objects like sunspots.

05-28-2012 - A closeup of one sunspot region using eyepiece project. It's sharp enough to tell the umbra and penumbra apart.05-28-2012 - Panning down from the previous shot to show more sunspots.05-28-2012 - Panning down from the previous shot to show more sunspots.
The biggest disadvantage is that it makes it extremely difficult to focus and the slightest breeze or bump completely blurs the image. You can only use this method when conditions are absolutely perfect. The magnification is so high that even the mirror moving up to allow the exposure will cause a slight vibration that will blur the image. For that reason we use a method called "mirror lockup" where the mirror is actually raised shortly before the shutter is fired.

Another method is called "prime-focus projection" where the camera is attached directly to the telescope without the magnification of the eyepiece or diagonal mirror. This basically gives the widest possible image through the telescope even though it's not very wide. With this setup I am effectively shooting at 3048mm f/10.

05-28-2012 - Prime focus at the telescope shows about 80% of the solar disc.
Even at the widest possible setting I am not able to get the entire solar disc in the frame.

05-28-2012 - Approx 3:30pm local time. Two images stitched together to show the entire disc of the sun.
By combining two images shot at prime focus and using a stitching program I'm able to create this full disc image. The really cool thing about this image is that with the way I adjusted the contrast and brightness of the image a solar phenomenon known as "faculae" are visible in a couple areas around the 10 and 5 o'clock positions of the limb or edge. It's the areas that appear as "white spots" instead of the usual dark sunspots.

05-28-2012 - Prime focus with the 1.4x extender attached at the camera shows about 50% of the solar disc.
This final image is sort of a cross between the previous two methods. I used the 1.4 extender and attached the camera directly to the telescope. I'm not sure what this method would be called because I've never seen it done.

I'd like to encourage anyone that is able to SAFELY view the sun next Tuesday to do so. The transit of Venus is a very rare event. In fact, it's one of the rarest astronomical events. The last time this happened was a relatively recent 2004 but prior to that the last time was in 1882 and the next time it happens is not until 2117. That's 2117, not 2017, so needless to say, none of us are going to be around for the next time it happens. If you are unable to SAFELY view the sun then please visit this site for a live webcast of the event. If you do have a SAFE method for viewing the sun then check out this site for details on where and when it will be visible at your location.

Hopefully you get a chance to see this spectacular event but if not, as Jack would say, "Keep Looking Up!"