Saturday, July 15, 2017

International Space Station

If you are in the right place at the right time you might be able to catch a glimpse of the International Space Station (ISS) as it passes in front of the Sun or Moon. These types of events are called "transits" and are fairly uncommon.

Transits are hard to see and easy to miss. The ISS orbits between 205 and 255 miles above the surface of the Earth, and moves at over 17,000 miles per hour. At that distance and speed, lunar and solar transits only last about one second or less and are only visible from a relatively narrow strip of land on the Earth's surface.

But finding a good viewing spot and time is relatively easy with ISS Transit Finder. This site lets you specify an area and a date range, and will calculate when and where the ISS will pass in front of the Sun or Moon.

A solar transit occurred on July 14, 2017. The center of the centerline of the transit was located in Lake Raven in Huntsville State Park, which is not far from where I live. I set up the ShortTube 80 with a full-aperture glass solar filter along the shore of the lake, and caught the transit using the Mallincam SkyRaider camera. Here is a composite image of the transit:

International Space Station transit of the Sun, July 14, 2017. Sunspot group AR2665 is located on the right.

The frame rate of the camera was not consistent, which is why there are gaps in the image sequence. The original monochrome images have been colorized to approximate the view through the solar filter.

The following video shows the transit in fairly close to real-time. Note that there are TWO transits! The first is probably an insect that either flew in front of the telescope or crawled across the objective lens.

On a side note, one of the lessons that I learned from the Venus Transit was that good polar alignment is critical for good results. This is difficult to do in the daytime, though, unless the mount has some kind of "magic" hardware and software for figuring out its exact position. My '80s-tech Vixen Super Polaris EQ mount does not have any fancy alignment features, but I was able to get a decent polar alignment using my mobile phone.

I plan on trying to image more ISS transits in the future when the opportunities arise. I would really like to get a lunar transit now.

Sunday, July 2, 2017

Mallincam SkyRaider

I just acquired a (almost never) used monochrome Mallincam SkyRaider Autoguider. And since the skies magically cleared shortly after the previous owner and I made the exchange, we decided to hook it up to one of my scopes and try some lunar imaging.

The results, in my opinion, were fantastic!

Moon, July 1, 2017; Mallincam SkyRaider w/Baader Contrast Booster; ST80 on Vixen SP
Click here for full-size image
98 images were stacked in RegiStax 5.1, with wavelet sharpening applied. The sharpness and contrast are better than any other image of the moon that I've taken previously, I think.

The camera can also do long exposures, but the images are very noisy.  The included software has a "dark field" feature that removes a lot of the noise, but the number of hot pixels on the sensor make it impractical for imaging deep sky objects.  Here is a single frame of Messier 4, with a bonus airplane thrown in just for fun:

Messier 4; Mallincam SkyRaider w/Baader Contrast Booster; ST80 on Vixen SP. This is a single 2-minute exposure with a dark frame applied.
Next, I want to try solar imaging with the ST80 and the glass solar filter. If that works out well, then I plan on using that combo for imaging the August 21, 2017 solar eclipse.

Stay tuned!