So what equipment are you using?

[smoker]

Canon EOS20D, with IR-filter modification
Sigma 18-200
Zenitar 16mm fisheye
Leitz Telyt 180mm/f3.4 Apo
Pentax 6x7 200mm/f4 and 300mm/f4 - currently on their way, no adaptor to use them yet!

Purely used for astronomical stuff.

[AB22 Easy Tiger]

Originally Posted by smoker

Canon EOS20D, with IR-filter modification
Sigma 18-200
Zenitar 16mm fisheye
Leitz Telyt 180mm/f3.4 Apo
Pentax 6x7 200mm/f4 and 300mm/f4 - currently on their way, no adaptor to use them yet!

Purely used for astronomical stuff.

What's involved in the IR Filter Mod Smoker?

[ThankHeavenForShed 7]

Sony a200 with the kit lens

Can't wait until I finish this Masters and start working properly again..I'm going to go turn in to a proper gear nerd!

[smoker]

Originally Posted by AB22 Easy Tiger

What's involved in the IR Filter Mod Smoker?

It's the replacement of the in-built UV/IR filter with a model with much better far-red transmission. The universe is teaming with Hydrogen alpha at 656nm, but the stock Canon filter reduces this to about 5-20% depending on model. A replacement filter gives you 95%+.

The drawback of the mod is your ordinary/daytime pictures have a pink cast. You can get a filter to undo this, but you end up with a multiplicity of step rings unless all your lenses are on the same filter size! As I rarely use the camera on auto I just use Custom White Balance calibrated on a shot of white printer paper and this does a good job.

Some people have the filter removed altogether, which gives you 100% H-alpha transmission but it also passes shit loads of IR which registers as white, and therefore needs to be filtered out by a separate filter in the image path. It also stops the chip and viewfinder being parfocal!

[APB]

Originally Posted by smoker

It's the replacement of the in-built UV/IR filter with a model with much better far-red transmission. The universe is teaming with Hydrogen alpha at 656nm, but the stock Canon filter reduces this to about 5-20% depending on model. A replacement filter gives you 95%+.

The drawback of the mod is your ordinary/daytime pictures have a pink cast. You can get a filter to undo this, but you end up with a multiplicity of step rings unless all your lenses are on the same filter size! As I rarely use the camera on auto I just use Custom White Balance calibrated on a shot of white printer paper and this does a good job.

Some people have the filter removed altogether, which gives you 100% H-alpha transmission but it also passes shit loads of IR which registers as white, and therefore needs to be filtered out by a separate filter in the image path. It also stops the chip and viewfinder being parfocal!

What he said

[youmademerealise]

Originally Posted by smoker

It's the replacement of the in-built UV/IR filter with a model with much better far-red transmission. The universe is teaming with Hydrogen alpha at 656nm, but the stock Canon filter reduces this to about 5-20% depending on model. A replacement filter gives you 95%+.

The drawback of the mod is your ordinary/daytime pictures have a pink cast. You can get a filter to undo this, but you end up with a multiplicity of step rings unless all your lenses are on the same filter size! As I rarely use the camera on auto I just use Custom White Balance calibrated on a shot of white printer paper and this does a good job.

Some people have the filter removed altogether, which gives you 100% H-alpha transmission but it also passes shit loads of IR which registers as white, and therefore needs to be filtered out by a separate filter in the image path. It also stops the chip and viewfinder being parfocal!

Odds on for photo board post of year even with 10 months remaining

[APB]

Originally Posted by youmademerealise

Odds on for photo board post of year even with 10 months remaining

Can you translate it for me please?

[youmademerealise]

Originally Posted by APB

Can you translate it for me please?

No.

[AB22 Easy Tiger]

Originally Posted by smoker

It's the replacement of the in-built UV/IR filter with a model with much better far-red transmission. The universe is teaming with Hydrogen alpha at 656nm, but the stock Canon filter reduces this to about 5-20% depending on model. A replacement filter gives you 95%+.

The drawback of the mod is your ordinary/daytime pictures have a pink cast. You can get a filter to undo this, but you end up with a multiplicity of step rings unless all your lenses are on the same filter size! As I rarely use the camera on auto I just use Custom White Balance calibrated on a shot of white printer paper and this does a good job.

Some people have the filter removed altogether, which gives you 100% H-alpha transmission but it also passes shit loads of IR which registers as white, and therefore needs to be filtered out by a separate filter in the image path. It also stops the chip and viewfinder being parfocal!

Thanks for that, I take it 656nm is the wavelength? I hadn't thought about the camera having a stock filter like that.

Edit: stupid question, of course it's the wavelength. Doh!

[smoker]

Originally Posted by AB22 Easy Tiger

Thanks for that, I take it 656nm is the wavelength? I hadn't thought about the camera having a stock filter like that.

Edit: stupid question, of course it's the wavelength. Doh!

Yes. nm = nanometres.

Sorry if that was completely impenetrable, I'm used to typing this stuff for a more specialised audience.

The CMOS sensors used by DSLRs are not only sensitive to light, they are also sensitive to parts of the "invisible" spectrum like Ultra Violet and Infra Red. We don't want these in our photos so the manufacturers place a filter in front of the sensor to block this unwanted "light". Unfortunately, a lot of the stuff we want in astro shots is in the red section of the spectrum, quite close to infra-red we don't want, so unless the blocking filter has a nice sharp cut-off between the two, we lose loads of far-red light.

Hope that makes more sense.