blue cast on pictures

[graham.hobart (Graham stevens)]

greetings, I took some piccies with my new (second hand, purchased from IIS trades!) 450D and a clip in CLS CCD filter. There was really no light pollution I could deal with but my neighbour has a massive screen TV which leaks light underneath the blinds and across about 30 metres to me. I was facing the other way but my photos seem to have more of a blue cast than usual. This picture of about 8 minutes stacked with dark frame calibration of Eta with cluster NCG 2393 and emission nebula 3324 a case in point. I 'capped the green' in Star Tools but what do I do next?
Graz

[graham.hobart (Graham stevens)]

PS my wild duck cluster/NGC 6218/6281/M8 /20/M4/Dumbbell taken on the same night all have the same hue to them. Is this a facet of taking longer exposures with an unmodified camera?
Should I be thinking of investing in an OIII filter and will this work Ok on an unmodifed cam?
Another question, what's a good (free or cheap) software to use to make mosaics?
Regards
Graz

[irwjager (Ivo)]

Hi Graham,

Wow, you're progressing fast! Seems like that filter is throwing off your color balance (which is to be expected).
Did Wipe's 'Cast' preset do anything for you? Else, the Color module is your friend.

Capping your green a-la PI's SCNR, HLVG or StarTools 'Cap Green' is only recommended once you have gotten your color balance right (and only if you're sure your object should not have any green in it).

Not sure about a program that does mosaics... Maybe someone else can chime in?

Cheers,

[graham.hobart (Graham stevens)]

Hey Ivo, firstly before I forget- these were processed on my Sony 32 bit lappy and it was pretty quick using Star Tools. No worries there about cross platform usage.
I thought about the colour module but was unsure how to push it but I will try and increase red above the blues/greens. I think it is the filter as with the older camera 350D) and shorter exposures sans filter I was still getting more reds.
The other thing I noticed is the download speed, even with no pics saved on computer (just on SD card) the camera was busy for about 20 seconds after each exposure which seems a lot longer than than 350D (8MP Vs 10MP)
This is using Astrophotography Tools as the control and capture programme.
Each baby step is one faltering foot towards the the pinnacle of astro-imaging -having an image of the week on IIS!!

[graham.hobart (Graham stevens)]

Tried again to get more reds in the mix...
As always, cabbages thrown at the usual address!
Graz

[NorthernLight (Max)]

hey mate,
i had the same problem but found that postprocessing is not the answer.
do this:
in perfect broad daylight put a sheet of copy paper (white) on the floor. attach your normal camera lens and take a picture of the paper only whilst having the filter installed.
next step is setting this picture as your custom whitebalance. done.
you get better results using a real greycard as copy paper is too white but it will do you the trick.

cheers

[graham.hobart (Graham stevens)]

sounds like a good plan-will try it. Thanks.
Also anyone know how to use Astrophotography Tools to get a histogram for adjusting Flats?