DSS problem with flat files made by Sharpcap

[tiziano]

Good morning everyone

I have a weird problem with DSS (maybe I'm doing something wrong)

- I add the image files
- I add the flat files (for convenience made the day after keeping the focus the same and the gain equal the inclination of the tube equal the same temperature)

neither dark nor bias files added (camera QYH183c photos taken at -5)

when I do from DSS *** 'Align selected images' *** I get this error message

*** 'DeepSkyStacker: the selected images are not compatible (width, height, number of colors, number of channels, only one master dark, offset and flat) ***

if I remove the flat files there are no problems the final image is displayed correctly

I can't figure out where what am I wrong?

can you help me ?

Thanks Tiziano

[tiziano]

Hi Robin

Can you help me ?

Thanks
Tiziano

[admin]

Hi,

have a look at the flat files in something like FITS liberator to compare their properties to the light/dark files. DSS is telling you there is a mismatch, either in

* resolution
* bit depth
* number of colour channels

And it can't cope with that. SharpCap on the other hand can cope with some mismatches between the two, for instance...

Using a monochrome flat on a RGB 3 channel image is fine in SharpCap - SharpCap will just apply the flat to all 3 channels.

Once you have figured out what the difference is that DSS is complaining about you can decide how to deal with it - for instance perhaps convert the flat frames to make them agree with the other ones.

cheers,

Robin

PS. Using SharpCap generated darks/flats in DSS can work nicely, but some people have also had issues which they found hard to resolve. In general, my advice is to try it if you want, but remember that the best way to guarantee good/easy results is to do all the processing in one application - that is to capture individual darks/flats and let DSS do the master dark/flat creation.

[tiziano]

Hi Robin
I checked the flat and light files with FITS Liberator

pixel width and height = 5544 x 3684,
color depth = 16 bit

i don't know where to check the
'number of color channels'

but i found this difference in the FITS Header
COLORTYP = 'RGGB' ---> in the FLAT file
And
COLORTYP = 'RGB' ---> in the LIGHT
could this be the problem?
if this is the problem how can I fix it

I also remind you that I took the two types of files (flat and light) in the same way that is
- Color space: RAW16
-Capture area: 5544x3684
-Binning: 1x1
-Output format: FITS files
-Debayer Preview: ON


I don't know where I'm wrong
Tiziano

[tiziano]

Hi Robin

for safety I am attaching screenshots
of how I make the flat file

Tiziano

[admin]

Hi,

If you look in the image headers in FITS liberator, look for NAXIS3, which is the number of colour planes in the image. A mono or RAW image will have NAXIS3=1 (or NAXIS3 missing entirely). An RGB colour image will have NAXIS3=3, and I think this is what you have got for your light frames.

The question is, how did you create the light frames that you are trying to stack? SharpCap does not normally save 16 bit RGB frames direct from the camera (possible exception of some ASCOM cameras that might provide the image in that format). Were the light frames actually saved SharpCap live stack images as that is one way to get a 16 bit full RGB image saved by SharpCap?

cheers,

Robin

[tiziano]

Hi Robin

The Light files I created via Sharpcap 'Live stacling' using these settings:

-Color space: RAW16
-Capture area: 5544x3684
-Binning: 1x1
-Output format: FITS files
-Debayer Preview: ON

Also this morning I took a test

I created LIGHT files (total 1 minute) using 'Live Stacking'
using the settings written above
I am attaching the two files for your knowledge
-a camera settings text file
-a text file containing FITS Hedear Light file created
as you can see in the text file it says RAW16
and in the FITS Header there is
NAXIS3 = 3
COLORTYP = 'RGB'

immediately after i created FLAT files from Capture ---> Capture Flat
with the same settings
I am attaching the other two files created for your knowledge
a camera settings text file
a text file containing FITS Hedear Flat file
in the FITS header flat file unlike the light files there is
COLORTYP = 'RGB'
but there is no NAXIS3

ciao
Tiziano

[admin]

Hi,

OK, so the issue that you have is that you *must* do flat/dark correction in SharpCap if you are going to do this trick of saving images from a number of separate stacks and then stacking those images later (making a stack of stacks). If you try to do flat/dark correction in the secondary phase then you will either hit problems like this, or if you work around those then the results will be incorrect anyway.

This is because SharpCap live stacking aligns the separate frames with each other as each new frame arrives, meaning that any pixel in the final image is made up of a mixture of information from various different pixels from different sub-exposures. This means that dark/flat correction will not work at all correctly if applied after stacking, they must be applied before.

The one exception to this is if you turn off alignment in SharpCap live stacking, but overall that doesn't really make sense as an imaging strategy, so very few people do it.

cheers,

Robin

[tiziano]

I Robin,
Sorry but I didn't understand,
how can I do / apply flat files to light files
made by sharpcap through 'live staking'

Tiziano

[tiziano]

Hi Robin

I did some tests on the fly, and I saw that
shooting with Sharpcap via 'Live Stacking'
setting
1- Align Frames (NO Check)
2- Raw Frames (Save except when Paused / Dithering)
In this way, all individual light files are saved

then from Capture ---> Capture Flat, I capture the flat files

then I take all the light files and flat files created under Sharpcap,
I give them to DSS and this way everything works and there are no errors from Deep Sky Stacker (DSS)

As soon as I can I do some tests in the evening ... weather permitting and I'll let you know

I believe it is the correct solution

What do you think ?

Tiziano