Light pollution and a DSLR

[dawson]

When using just a DSLR and lens to do widefield imaging, how do people filter out light pollution?

Thanks.

James

[Doc]

Darker skies or a light pollution filter.

[dawson]

But how do you mount a light pollution filter on a camera lens? I've only ever seen 1.25" or 2" light pollution filters and i think my true wide angle lens has a 72mm or 78mm screw thread.

Darker skies aren't an easy option.

James

[Guest Kheldar]

As above, my weapon of choice was a Hutech IDAS V2 LPS filter and a drop down adaptor to convert the lens thread to M48 (2" filter thread)

[Guest Kheldar]

Alternatively the clip in version goes inside the camera body (forgot that)

[xanthic]

If you are just suffering sodium pollution, can you fix it in Photoshop?

[dawson]

You can show me how to do that sometime leigh, i get bored of playing with images in photoshop, i find it so tedious!

Jd

[Guest Eddy]

You can kinda fix it in PS but you lose a lot of detail and it's a long process

[dawson]

Stuff "long process"

This thread was inspired by one on SGL, a guy there has given me a link to the clips which fit inside the camera: i like that option as it means i could use various lenses. It's just confusing which filter type i'd need as there appears to be many of them.

James

[Guest Kheldar]

http://www.teleskop-express.de/shop/product_info.php/language/en/info/p1923_Hutech-CLIP-IDAS-Nebelfilter-LPS-P2---fuer-Canon-EOS-DSLR.html

 

http://www.modernastronomy.com/filtersAstronomik.htm#aCls (CLS or CLS-CCD for modified camera)

[dawson]

What do CLS and CCD stand for in these situations?

Jams

[dawson]

Looks like the CLS (whatever that stands for) eos clip is about £108; that's a considerable investment.

I might just have a play with a stepper ring on a smaller lens and borrow a 2" light pollution filter off someone first to see what impact they make.

Thanks.

James

[xanthic]

I've got a 1.25". I know it won't fit, but look through it and you'll see the difference. I'll bring it over.

[dawson]

Ok, thanks. I've sent you a private message anout ABS too, check your inbox.

Jd

[Brantuk]

I think it stands for chemiluminescence : http://en.wikipedia.org/wiki/Chemiluminescence

 

And CCD is charged couple device.

[dawson]

So is there much difference between the CLS and the CLS-CCD filters?

I'll look out for one on ABS.

James

[Brantuk]

I'm just guessing here but I would think the cls filter for a scope is for observing, and the other is for the ccd camera chip. Both do the same or similar job which is to reduce the effects of street lights.

[Guest Kheldar]

As I said up there, CLS-CCD is for modified (or CCD) cameras that don't have inbuilt IR cut

Regular (non modified cameras) can use the CLS version

[dawson]

Link to a thread about this on SGL:

http://stargazerslounge.com/topic/83387-astronomik-cls-v-cls-ccd/

Thanks for the link Leigh.

James

[dawson]

Super, thanks stephen and others; it is the CLS one i'd need for my canon.

Night.

James

[+Ibbo]

I think gilder has a method for this

 

Steve

[Orion]

James. Look up didymium (or dydimium) filters.  There may be some info on those which you may find interesting.  They are a special glass that contains certain lanthanide elements.  They have an absorption spectrum that will take out the yellow sodium D line emitted by sodium street lamps, but I think the sodium street lamps have a wide emission spectrum and not all the light will be taken out by the didymium filters.  I saw an interesting demonstration of this filter.  Shine a white light source onto a wall. A projector is good.  Insert into the beam, a prism so that the light is split up into a rainbow. Now, insert the dydimium or other filter into the beam and look at the rainbow spectrum on the projection wall and see a dark line (or lines) which shows which light wavelengths have been absorbed by the filter - generally a black line in the yellow part.   

[dawson]

Thats interesting; i've seen there are neodymium filters bit never really thought about the science behind it.

Thanks

James

[Antares_Paul]

Clips filters can't be used with an EF-S type lens (they extend further into the camera body). The older EF are ok.

 

FYI.

 

Regards.

[+RonC]

As Paul says; I have a CLS clip filter fitted in my modded 1000d, I cannot fix the original 18-55 lens on but I can fit my Sigma 70-300 lens. The filter works very well and my photo's are the evidence!

 

Cheers

Ron