Tag Archives: telescope

Transit of Venus from My Back Yard

So,  yes…I am a little late in posting this.  On June 5, Venus (the planet and not the hot looking goddess) cleverly positioned itself directly between the Earth and the Sun causing itself to be seen as a little black spot on the Sun (cue music…) from various lucky locations on the Earth.   Now I happen to own a rather nice little telescope, so I decided to set it up in my backyard and check out the event. Apparently this is a rather rare event relative to the lifespans of human beings and won’t happen again until the year 2117 so I seriously doubt I will see it again. Yes, the smaller black dots are actually sunspots. Click on the pic for a high-res version.

OK…so a few technical details. The telescope. It is a Meade LX200 8″ Schmidt Cassegrain reflecting scope (which means it is short and squatty) as opposed to one of those LONG Newtonian reflector telescopes or one of those even longer refracting telescopes. The specifications (for those who are so inclined) are as follows:

  • Clear Aperature: 8″ (203mm)
  • Focal Length: 2000mm
  • Focal Ratio: f/10
  • Eyepiece: 1.25″ diagonal prism
  • Resolving Power: 0.570 arcseconds

To take the pictures of the event, I used my old trusty Nikon D100 digital camera. Yes…it is OLD and by today’s standards not very high resolution (coming in at a whopping 6 megapixels!!!) It is however, a Digital SLR and it works with all my old Nikon glass (lenses) and connects like a dream to my LX200.   It works fine and I like it. So there. Specs are as follows:

  • Sensor: CCD, 23.7 x 15.6 mm
  • Total Pixels: 3110×2030 (6.31 megapixels)
  • Lens Mount: Nikon F
  • Focal Length Multiplier: 1.5X
  • Storage: CompactFlash Type I/II
  • Sensitivity: ISO 200 – 1600
  • Shutter Speed: Bulb, 30 sec – 1/4000 sec

The first pictures I took were by simply holding the D100 with a 35mm lens up to the 28mm lens mounted in the telescope and moving the camera around until I could see the transit because I was too lazy to hook the camera up to the telescope directly (like above) and “dial it in” – which can be a pain sometimes.  The pictures came out kind of like you would imagine – not very good.  This was at the start of the event and you can see that Venus is on the lower left corner of the picture because the image is “inverted” when using a standard lens set up. After a few rather poor pictures it became clear to me that I should stop being lazy and use the camera adapter and directly connect the D100 to the optics of the telescope.

I then set the D100 to manual mode and simply adjusted the shutter speed until the pictures I took made sense.  I had to adjust the focal length of the camera adapter “barlow tube” and use the “focus” knob on the scope to get clean focus.  This took a little while.  Luckily the transit took several hours so I had plenty of time. Since there isn’t an “aperture” to speak of in a telescope set up (kind of fixed at F/10) the shutter speed and ISO settings are all you really have to work with.  I set the ISO to 800, which results in very little CCD noise and has good light gathering sensitivity.

Oh yeah…important safety tip.  I obviously had a solar filter installed on the telescope. This was important because a) you wouldn’t be able to see Venus without it due to the glare, b) you would go blind almost immediately and c) the telescope optics would melt.  Sighting in the scope was kind of interesting…since I didn’t have a solar filter on the “spotting scope” to see where to aim the scope to begin with.  Believe it or not, even with an object as big in the sky as the sun, training the optics to be precisely lined up with the sun is tricky when you can’t really look through the spotting scope.  This resulted in me using my hand and projecting the image of the spotting scope (in shadow) and the sun (bright spot on my hand through the spotting scope optics) and getting the bright dot in the middle of the shadow.  Sounds weird but it worked perfectly.

Here is a quick snap of my telescope set up in the backyard.

Now…for some of the pics I took with this setup. Hope you enjoy. The stuff that looks like “smoke” in some of the pictures are actually clouds. Enjoy the Transit of Venus! Most of us won’t see it again…