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UV Filter. Any benefits when using a DSLR for Astrophotography?

Canon EOS Ra Filters UV/IR Cut
Camera Lens Astrophotography •8 replies•221 views
Richard Rice avatar
Richard Rice avatar
Hi. I have just bought a Canon RF 35mm f/1.8 to use with my Eos Ra. During the day it makes a fine walk around lens and so I have a UV filter (lens protector) on it. My instinct is to remove it when shooting a night, every photon counts and all that, however I'm not sure. I can see from the specs that not only does it cut the UV at one end of the scale but also the longest IR at the other end of the scale.
Is there any benefit to be had from leaving it on?
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Tom Gray avatar
Tom Gray avatar
Hi Richard, I’m not sure about DSLRs or CMOS, but CCD imagers often us a UV/IR cut filter to reduce starbloat; I’m sure other DSLR users will advise.
Richard Rice avatar
Richard Rice avatar
Hi Tom. Thanks for the advice, I had a feeling it would not be a simple yes or no. As you've probably gathered, I am quite new to this and it's certainly a steep learning curve.
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Tom Gray avatar
Tom Gray avatar
Richard:
Hi Tom. Thanks for the advice, I had a feeling it would not be a simple yes or no. As you've probably gathered, I am quite new to this and it's certainly a steep learning curve.

It most certainly is - lifelong learning, but such fun 😀
Marzo Varea avatar
Marzo Varea avatar
Hi! I have found that at least some of my lenses let pass enough UV to make blue or purple halos around hot stars in my Nikon D7000. However my comparative tests with good enough quality filters have been... mostly just this one:

Test: Hoya UV(0) filter on Nikkor 200 mm f:4

I think the filtered image is noticeably better. I have yet to test an astrophotography UV/IR cut filter, which I expect would be the best (although not available in aperture over 2" minus its ring).  Of course, I suppose YMMV.
Richard Rice avatar
Richard Rice avatar
Hi Marzo,
  Thanks very much for your reply and the pictures for comparison. That would certainly be a reason to try leaving the filter fitted. 
  When the clouds finally clear for long enough I will attempt a similar set of pictures for comparison. 
 Thanks again. Clear skies.
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Gernot Schreider avatar
Gernot Schreider avatar
When shooting Pleiades with my SONY Alpha 6000 with Zeiss telelens 300mm attached I noticed quite significant blue and purple halos around the stars.
I did not test using a filter but I will definitely check this out. Thanks for highlighhting this.

Cheers
Gernot
Marzo Varea avatar
Marzo Varea avatar
Richard:
Hi Marzo,
  Thanks very much for your reply and the pictures for comparison. That would certainly be a reason to try leaving the filter fitted. 
  When the clouds finally clear for long enough I will attempt a similar set of pictures for comparison. 
 Thanks again. Clear skies.


Hi, Richard
No problem! Clear skies
firstLight avatar
firstLight avatar
Gernot Schreider:
When shooting Pleiades with my SONY Alpha 6000 with Zeiss telelens 300mm attached I noticed quite significant blue and purple halos around the stars.
I did not test using a filter but I will definitely check this out. Thanks for highlighhting this.

Cheers
Gernot

I suspect blue and purple halos around stars are usually issued by CA (chromatic abberation). This happens mostly on the sides and in the corners of an image, at least there appearance is worst, there. The origin is not UV radiation but the always increasing light refraction (like a tiny prism would do) along the eges of any lens.

UV radiation shouldn't hurt anyways, because all DSLR sensors have a built in UV cut filter applied.

HTH,
Frank aka firstLight
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