RGB Pain and Frustration

[steve2310]

Hi all

I really hope one of the lovely SGLers can come to my rescue?

I have had an Atik 383L for about 5 months now and having 'played' around with some narrowband imaging (just in ha) I thought it was about time that I got to to grips with some (L) RGB colour.

Having grabbed about 8 hours of luminance of M81+M82 I made my first attempt at imaging some RGB data earlier last week with the Atik attached to my equinox 120ed. Binning 1 x 1 at the same length as my luminance subs (15m) I managed to produce an RGB image that was distinctly ORANGE.

These images were captured with Artemis software but all stacking and combining was done with Maxim DL. Scratching my head and feeling rather puzzled (and disappointed as I spent ALL night obtaining the images) I decided to have another go.

This time I decided to bin the images 2 x 2 but set the subs to 5m. The images taken on this night I thought would be far superior as I had NO MOON to contend with, much better visibility etc etc.

Today I have combined the data and found the image to be MASSIVELY ORANGE!!!!!!

Being totally confused and soooooo frustrated I presumed that I had put the filters in incorrectly in the EFW2 filter wheel so I had that apart this afternoon but noooo, everything in the right place.

Being new to Atik 383l and RGB I balanced out the colours as 1:1:1 in Maxim and I took an equal amount of each colour (12).

What have I done wrong guys? Why is my colour so badly wrong? Orange? Why orange?

Any help would be great and yes, I am now drinking beer in vast quantites!

Cheers! Steve

[Earl]

Have you tired background neutralization in Pix Insight?

http://pixinsight.com/videos/index.html

The first tutorial on the page goes into this in detail.

[kookoo_gr]

1. do you image at an LP area? Is there a floodlight/streetlight nearby? LP tends to give an orange color at imaging. I imaged the horsehead nebula a few months ago from an LP area and the image was orange

2. when you combine the data do you assign the correct stacked frames at each color?

3. try combining the images without any calibration frames just in case you got any bad calibration frames.

4. try a g2v calibration

[Mark72]

Steve,

Could you stop drinking beer for a moment and post you final calibrated RGB, perhaps in tif format. I also image with the same camera and filter wheel but have not seen such an effect.

Mark

AstroBin - Mark's gallery

[steve2310]

Cheers guys for the input and advice - I'm very grateful.

Earl: I dont currently have Pixinsight although I have 'played' with it in the past. I will have a look at a similar function in Maxim.

Kookoo and Mark: I spent a number of hours hunting the net for tutorials, tips, examples etc and came across a number of imagers who discussed the colour ratios for RGB and how CCD's are sensitive to certains colours say, red and green but considerably less so with blue.

Having read how to adapt the RGB ratio in Maxim, I played around with various ratios and found that if I increase the blue, changing the RGB ratio to 1:1:1.4, the combined image looked sooooo much better. I know that at some point I should dedicate some time to do a g2v calibration but for now I am happy to keep moving forward knowing that I am not going totally mad.

Mark: Really interested to see you also have an Atik 383L. Which software do you combine/stack your images in? Any particular tips or pitfulls you have come across? I love the Atik but I am finding CCD imaging quite a challenge but surely that's part of the fun??

Thanks again guys for taking the time to reply.

Steve

[NickK]

The data sheet for the KAF 8300M is a good starting point.

Google "KAF-8300LongSpec.pdf" then on page 17 is the QE vs wavelength for both colour and mono versions (figure 6 for the mono).

Page 38 gives an example of schlott glass transmission (i.e. only worry for wavelengths under 350nm.. i.e. don't bother!).

Then apply the Baader LRGB transmission for each wavelength....

[Mark72]

Steve,

I capture in Artemis and stack in PixInsight.

I do not see your image to help you more. I have just one LRGB with this camera - AstroBin - M100 in Coma (Mark)

LRGB is not a challenge. It was rather 11 hours with Canon which did not produce much but noise. Going to mono CCD with filters proved to be the most promising purchase.

Mark

AstroBin - Mark's gallery

[steve2310]

Thanks Nick and Mark:

Mark - I'm currently in the back garden trying to capture some more colour but it seems that the cloud might defeat me tonight (bah!!) Once I have captured some more data I'll upload an example.

Nick:

That is REALLY useful so thank you so much! I'll check out the pages you specify.

Cheers again guys.

Steve

(Now off to pack everything away!!)