Kepler

[Zac Pujic]

Here is Kepler. Not on my list of interesting lunar features, but worth photographing anyway.

http://astroimg.org/latestlunar.html

Zac Pujic
Brisbane, Australia
http://astroimg.org

[iceman]

Looks like you were affected by the seeing more on this night, Zac.

I'm guessing you've resampled this lunar image, as it's bigger than the 640x480 of your ToUcam.

Is the Wratten25A a red filter? Do you find filtering that wavelength cuts through the seeing more than any other colour?

[Robert_T]

Hi Zac, another great lunar image! Keep em coming!:thumbsup:

Like Mike asks, I'm interested in what the best colour filter is to use to reduce seeing effects?

cheers,

[Zac Pujic]

The Wratten 25A is a red filter. The rationale behind using red and infrared light transmitting filters is that scattering and refraction are less at longer wavelengths. In fact scattering is inversely proportional to the fourth power of the wavelength. This means that red light from the Moon is less affected by adverse seeing. The image produced in red light is frequently sharper than that obtained using unfiltered light.

However when the seeing is good, using a blue filter can be slightly more advantageous. This is because the resolution of an optical system is linearly inversely dependent on wavelength; the shorter the wavelength, the smaller the Airy disk and thus the higher the resolution.

But seeing is rarely good enough to warrant the use of a blue filter and the benefits of this slightly higher resolution is offset by the fact that adverse effects from scattering and increased refraction in blue light will predominate.

Stick to the red and infrared transmitting filters. Also, most wecams, like the ToUcam, have essentially no blue sensitivity, but very high red and infrared sensitivity. The noise in the blue channel will be high making use of blue filters difficult with such cameras.

Incidentally, imaging the Moon in red can sometimes change the relative constrasts of the Mare and highlands since some Mare are red and some are blue, although few people appreciate this.

Zac Pujic
Brisbane, Australia
http://astroimg.org

[ballaratdragons]

Geez Zac,

At what altitude did you fly over the Moon to get that shot!!! Very good work.

Whether the seeing was poor, filter or no filter, etc etc, I like it.

[iceman]

Thanks for the info Zac. So you suggest using an IR transmitting filter, rather than an IR blocking filter? Why is this?

Interesting regarding the Red filter too - I thought along the same lines which is why I imaged schiller in this thread (http://www.iceinspace.com.au/forum/showthread.php?t=11519) using red RGB filter, but I was also using the IR blocking filter.