Extreeeeeeeme stretching (IC 1396, nelly's nose neb)

[martin_h]

You can do the same in DSS.....reload all the data..not using masters, and make sure the flat setting is as the image below.

[MikeWilson]

You can do the same in DSS.....reload all the data..not using masters, and make sure the flat setting is as the image below.

Might be onto something here.

My flats were on Median Kappa-Sigma clipping.

[RobH]

The stacking algorithm for calibration frames should be average combine, but it isn't the end of the world if another method is used.

I've applied your flat to your non flat corrected light, using maxim, but the issue is still there.

Flats don't apply properly in Maxim unless they are bias subtracted.

Is your flat bias subtracted?

If not, can you let me have a bias master and a single sub and I'll have another go.

Cheers

Rob

[MikeWilson]

The stacking algorithm for calibration frames should be average combine, but it isn't the end of the world if another method is used.

I've applied your flat to your non flat corrected light, using maxim, but the issue is still there.

Flats don't apply properly in Maxim unless they are bias subtracted.

Is your flat bias subtracted?

If not, can you let me have a bias master and a single sub and I'll have another go.

Cheers

Rob

Hi Rob,

Thanks again :-)

"Is your flat bias subtracted?"

The simple answer is - I don't know. I've always done what DSS has asked me to do. That is, add lights, bias, flats and darks. The bias master and a single light and the dark master were in the .rar file I posted earlier for you. I'm guessing now that those didn't work in your Maxim routine?

I've uploaded a single light image, a single flat, a single bias and a single dark. Maybe these will work?

I've restacked using the Median Flat option: http://dl.dropbox.com/u/3717210/IC%201396%20RGB%20-%2006-06-2011%20stacked%20with%20median%20flat.TIF Edit: Doesn't appear to have made any difference...

And here's a file containing a single copy of each of light, bias, flat and dark. Hope this helps?

http://dl.dropbox.com/u/3717210/IC1396_SingleFrameOf_Light_Bias_Flat_Dark.rar

Thank you again for all of your help - I'm more than slightly lost at this point

All the best,

Mike

[martin_h]

I think from a previous thread that DSS does it all on the fly.

One thing tho - in DSS under the Raw/FITS DPP Settings - FITS Files, have you ticked the box for Monochrome 16 bit Fits files etc and selected the QHY8 camera?

[MikeWilson]

I think from a previous thread that DSS does it all on the fly.

One thing tho - in DSS under the Raw/FITS DPP Settings - FITS Files, have you ticked the box for Monochrome 16 bit Fits files etc and selected the QHY8 camera?

Yep, I think so.

Many thanks,

Mike

[MikeWilson]

Hi Mike,

Just a thought. You are using a QHY8L OSC CCD, did you remove the colour data from the flats (ie the bayer matrix)?

Your master flat still shows the colour data there. This can be done using a Boxcar 2x2 filter in your processing software (ie Maxim DL) before stacking to create a mono flat

Regards,

Steve

Hello Steve,

Thanks for your reply, I missed it as topic moved over to page two..

I thought that DSS would handle this automatically, since it did before when I was processing DSLR images. The colour data isn't important though since only the luminosity is used to divide the pixel values from the lights?

Or am I missing something?

All the best,

Mike

[MikeWilson]

This is interesting.

Taken from: DeepSkyStacker FAQ

is it possible to use colored flat frames?

The short answer is yes.

The overall tint of your flat frames is not really important because DeepSkyStacker is processing each channel separately and is applying the flat frames to each channel accordingly.

Of course if your flat frames are fully red only the red channel of your light frames will be properly calibrated but otherwise as long as as the peak in each channel is between 1/3 and 2/3 of the maximum you should have no problem using slightly colored flat frames.

With the CLS filter, the best I could manage was not clipping the left or the right of the histogram. One colour (I think green) is way to the left while red and blue are way over to the right. There's just no way around it.

Thanks,

Mike

[3ggman]

Hi Mike,

I had a little go at processing this, although I can't really advise you on any of the issues, here is a comparison for you anyway.

I ran the same processes on both images in PixInsight, I may have been a little more aggressive with the "No Flats" image. The one with flats is the first tiff that you posted.

There is a difference, what it means I have no idea, as I don't use flats

[RobH]

I'm afraid I won't be able to have a bash with the frames you uploaded yet Mike, as I only have intermittent net access at the moment (I'm working and travelkling daily), but will have a crack when I get some free time.

Cheers

Rob

[jsigone]

you have allot of nice data in your lights. IMO plenty to make a nice image. My version looks a bit like 3ggman's. I'd retake your flats, equal number to light files and go from there.

[MikeWilson]

Thank you Johnny, Rob and Jsigone,

Since I don't know exactly what's happening - when I next take flats I'll try a variety of exposures. I'll take the 300ms ones as usual, but I'll also over expose to 1 second as well as under exposing to 100ms to see if these produce 'better' flats? Maybe I should be doing really dim flats around 10ms? (This is for the CLS filter that I used in this RGB image).

Does this sound like a good idea?

All the best,

Mike

[jsigone]

At this point I'd take them at a few different setting and see what works. Pick the one with the histo in the middle.

[MikeWilson]

At this point I'd take them at a few different setting and see what works. Pick the one with the histo in the middle.

Hi jaigone,

This one is the one with the histogram centred.

There are two peaks. One on the left and the other larger one on the right.

Any ideas?

Should I shorten exposures to move the right hand side part to the middle (and reduce the left part) or increase exposures to move the left part to the middle and push the right hand side to max?

All the best,

Mike

[jsigone]

maybe the CLS filter is causing the second spike. Try to edit each flat to align the color channels, save a copy and take those into DSS. Not sure how fast your PC is, but just do a few of each file type in DSS to run this test. If it seems to work, do the entire set of lights & ect.