Observing session : light glow filter test

A few nights ago I managed to find 90 minutes of clear sky after the sun had set. I had thought the sky would have been mostly cloudy but was surprised to see that even though the sun was only just setting, there was not a cloud in the sky.

So I took my telescope out into the garden and set it up. And then I saw a few clouds gathering in the west. I decided not to collimate the telescope and set it up as it was so when darkness fell I would be ready.

Jupiter was in the west…about 31 degrees over the horizon. Neptune was in close proximity about 29 degrees high over the horizon. My focus was in Jupiter though as it was the only object visible at that stage and I wanted to conduct a test before the clouds in the west blocked the planet.

I had huge problems with the scope at that stage and was unable to see Jupiter through the eye piece. I then discovered that was because I was using a 2.5 inch lens and that had no hope of seeing anything that night.

So I replaced the lens with my zoomable lens and focused on Jupiter. All 4 of Jupiter’s larger moons were out with Io fairly close to the planet.

Sirius (Click to Enlarge)

After I had looked at Jupiter and it’s moons for a while, I then added the CLS light filter I had purchased 3 or 4 weeks ago so I could see the difference between Jupiter with and without the filter.

With the light filter in place, there was without doubt a much darker background seen through the lens. Jupiter and it’s moons were a shade bit fainter to see and perhaps had a greenish tint to their color. But this was what I expected. The trick before buying new bits and pieces for the scope is to research the items you are buying , specifically looking for reviews. This way you get to see the good aspects and the bad aspects so you have an idea of what you might expect to see.

With the current camera I am using ,there would be no way that I would be able to take pictures using the filter without the ability to use time exposures. This is why I am looking at a camera upgrade very soon.

But with the light pollution in the area  a few nights ago, I was pleased with the light filter and it does need to be tested further. When I get a new camera and start taking pictures, I will be able to bring out the light in the back ground of stars that will have being reduced by the filter. Processing afterwards is an important step if I have the filter in the scope.

I didn’t get too much of a chance to test the filter as clouds suddenly rolled in from the south. I did however manage to do a filter test on Sirius which had an apparent magnitude of -1.47.

Sirius was still shining brightly even with the filter attached and I was happy with the result.

More testing needs to be done , specifically in a less light polluted area…. but so far the CLS light filter meets my expectations.

~ by sydneystargazers on January 4, 2010.

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