DSLR red bias - correction?

[ollypenrice]

I don't image with a DSLR but a former guest called round to show me some first results with an Astrodon filtered 40D (I think, or was it one of the very top end Cannons?) He's a professional photographer by day.

Done on an Astrotrak the images were incredibly sharp, great focus and tracking, but they were very, very red. Balancing in levels helped a lot but still they were hugely red. To get the red down any further would have meant black clipping it by a mile.

Are we missing something here? Or as they say in the personal help columns, is this normal??

Olly

[MickyWay]

Hi Olly

Which Astrodon filter was he using?

Where did he take the pictures?

If he has the Canon factory filter removed with no replacement

(eg a Baader DSLR filter), then the chip will see all the way up to the red end of the light spectrum. Then, if he shot in a light polluted location, without any LP filtering, this would give you the worst possible senario for 'red' images.

Sorry if you all ready know this.

Regards,

[ollypenrice]

Thanks Colin. No light pollution, he was on the top of an Alp at a star party and said it was dark. I'm afraid I don't know what fiter it was, just an Astrodon.

I have no experience of shooting in LP so don't be afraid to tell me about it!

Olly

[MickyWay]

Hi Olly,

I've attached this a single exposure image of M42, which was taken under light polluted skies here in the UK. No CLS filter was used , and the camera (Canon EOS1000D) was, at the time, unmodified.

I rather thought that your problem picture was taken under dark

skies (lucky you!). However, you can see that had this camera been modified, the red end of the spectrum would be even more evident. It would be a help if we knew the camera setup, filters etc...

[MickyWay]

I know that Astrodon do an 'Astrodon Inside DSLR' filter (bit too rich for me)

Astrodon Astronomy Filters - Astrodon Inside DSLR

[harry page]

Hi

As noted earlier dslr camera are very sensitive to red and light pollution

If you would like to see how I handle this in pixinsight have a look at this video ( sword of orion at the bottom )

http://www.harrysastroshed.com/pixinsighthomeinter.html

Its not that hard to work round

Harry

[George]

Never had the problem of the red spectrum being over sampled as the CLS seems to correct this and the blue hue is easily dealt with in photoshop.

[MickyWay]

Absolutely right George, a CLS filter is essential unless you're imaging under dark skies. We don't know if Olly's guest was using filter.

[MickyWay]

Hi

As noted earlier dslr camera are very sensitive to red and light pollution

If you would like to see how I handle this in pixinsight have a look at this video ( sword of orion at the bottom )

http://www.harrysastroshed.com/pixinsighthomeinter.html

Its not that hard to work round

Harry

You make it look so simple Harry!

[harry page]

Hi

It has to be simple for me

harry