colour of light frames with astro camera

[alacant]

Hi everyone

I just changed cameras. This is a frame from a Canon 700d with the filter (?) removed for red sensitivity by Juan at cheapastrophotography.com. It stacks OK but everything appears red. I have to colour balance the red out quite a bit. Is it supposed to be that red?

TIA

[iwols]

4 minutes ago, alacant said:

Hi everyone

I just changed cameras. This is a frame from a Canon 700d with the filter (?) removed for red sensitivity by Juan at cheapastrophotography.com. It stacks OK but everything appears red. I have to colour balance the red out quite a bit. Is it supposed to be that red?

TIA

link not working for me

[geordie85]

Are you using per channel calibration or rgb calibration in DSS?

[alacant]

[alacant]

No calibration. This is a single CR2 file. Thanks.

[ollypenrice]

I think it's pretty normal to have a huge red bias after modification. If you use Pixinsight I would just run an image through DBE. It will come out looking a lot more promising:

Bear in mind that this was just done on a JPEG screen grab with no attempt to refine the settings.

Olly

[Knight of Clear Skies]

Yes, this is normal, the camera doesn't understand that one of the filters has been removed and much more red light is reaching the sensor. The DSS colour calibration options can help but they don't work reliably, I often have to manually adjust the output. For some reason I don't understand some stacks are much easier to get right than others.

[alacant]

Hi and thanks for the replies. I too find that a stack is nearer to normal but I still end up having to use colour balance in StarTools or gimp afterwards. I find the colour the most difficult (nay, impossible!) part of the post processing. With the non modded camera I didn't need to colour balance. Now I do. Ah well. Can't win 'em all. 

[alacant]

Hi again

Here's a copy of a post I sent to the StarTools forum with an example of the fits output by dss which I thought may be of interest to us here too:

Hi everyone

I changed cameras from a normal Nikon to a Canon with the red (IR?) filter removed. OK, I can now take snaps of M8, but eveything else has got worse. Everything else is red and an absolute nightmare to colour correctly.

With the Nikon, the DSS colurs were more or less on top of each other and I hardly ever needed to touch the colour. Now, with the Canon, everything is red, especially the noise, and it much (MUCH) harder to get anywhere near the colour. Calling ST colour then makes matters worse as it's then a battle with the green as the default seems to have reduced the reduce-red slider to half way across.

I'm tempted to align the channels in DSS but I know that's not recommended. I'm uploading the fts at the moment if anyone has the time to have a look. I can attach the dss screen-snap now. As each image takes several hours to wipe and denoise (AMD E1 with 8GB RAM) any hints would be most gratefully received <self-pìty> I'm wasting days on end waiting for each image to process (sic)!</self-pity>

fts:
https://drive.google.com/open?id=0B_uUt ... 2xKeFNTMXM
TIA