Astronomik CLS filter

[skysurfer]

I received this filter today so I 'dry tested; it, i.e. on street scenes and with high pressure sodium and metal halide lamps to test its performance. Because of cloudy and moonlit skies I cannot test in real life yet.
It looks really promising: the ubiquitous yellow sodium light is dimmed for at least four stops while daylight / starlight is dimmed for only one stop.

Here my preliminary test report: http://www.northsouthsky.com/astronomik-cls.php

[alistairsam]

Those are some very good results. the spectrum illustrates the bandpass/cut-off nature beautifully.
I did use one of these for some DSO imaging from my backyard and the red skyglow was almost nil with the filter. only issue was colour balance. it shifts it quite a bit, but I believe if you use a grey source as the white balance point, colours get corrected??
what you could add on would be a 5 min exposure of the night sky with and without the filter, should show a large difference.

[troypiggo]

What a simple but clever idea! Never thought of testing with terrestrial shots like that.

[stevous67]

Well done and congrats on the nice presentation of your analysis. :thumbsup:

I have the Astronomik CLS 2" filter for my STL, and I can confirm that imaging galaxies is totally possible from my suburban home in Melbourne [35km from CBD].

I've attached an example of NGC1365, taken in Feb last year, and I think it was 5x10min subs Bin1x1, with the GSO 10" RC.

I have bright street lighting around me, and when I look up on a moonless night, I can just see Eta Carina [NGC3372] naked eye as a slight and faint smudge, I can no way see the Magellanic Clouds, and I think I can see to about apparent mag 2 [a guess]?:confused2:

Apart from using narrow band filters, I cannot capture RGB channels without influence of the city lighting.

On a separate note: I read in peoples captures that they image in "heavy light pollution", and I am amazed by the colour definition achieved - but this is not a product of their advanced optics, but more the relativity of one’s opinion of what "heavy light pollution" is. If I go to a regional town, say Somerville VIC, and I'm at my mother-in-laws home, which is situated in the middle of town, I look up and are amazed how improved the darkness and contrast is.


Back onto this thread, thanks again - very interesting. :thanx:


Cheers,

Steve

[2stroke]

Most lights around my place are mercury vapor i think, will have to look into this ad the spectrum in nm. Great review BTW :)

[Screwdriverone]

Great review Skysurfer,

This certainly cements in my mind the importance of getting one of these for my EOS 1000D.

Love the review and the comparison pics, really shows you its effectiveness.

Ping Mike Salway and get him to convert your page (with your permission of course) to a review article to be posted here on IIS, it would certainly be a great addition to the list as it is a very comprehensive report and informative.

I'm now thinking of shelving the new CCD camera idea and sticking with the EOS with a cool box and one of these to save cash and get better results with what I have, this saves me a lot of research and pain with trial and error.

Well done!

Cheers

Chris

[skysurfer]

Good idea, but I have to wait for a clear moonless night to get real sky results. Yesterday I tried on a thin waxing gibbous (1 day after FQ) but skyglow was too much and filtered exposures were bright blue (and unfiltered yellow). I just posted the results on the page.