My experience is that if you have the sensitivity percentage about right and DSS counts a few hundred stars it should stack 100% of the images if that is set. Raw frames should be stacked and set up correctly. The only circumstance that it will not do that is if the guiding has allowed the frame to move so much that there is too much out of frame or you have selected a bad frame as the reference frame. Make sure you select the frame with the most stars as the reference frame and open each frame and zoom in to check your object is really clear in there and not obscured by noise or cloud or movement.
In the register screen if you check advanced and change the percentage you can quickly compute the number of stars. With my OSC shots , increasing the percentage reduces the number of stars computed in DSS.
My experience is that if you have the sensitivity percentage about right and DSS counts a few hundred stars it should stack 100% of the images if that is set. Raw frames should be stacked and set up correctly. The only circumstance that it will not do that is if the guiding has allowed the frame to move so much that there is too much out of frame or you have selected a bad frame as the reference frame. Make sure you select the frame with the most stars as the reference frame and open each frame and zoom in to check your object is really clear in there and not obscured by noise or cloud or movement.
Hi Ray...you really have to go overboard for DSS not to work because of poor framing...these days I don't worry about getting the following nights framing anyways near perfect...and remember I don't use goto just eyeball objects from memory ..I get a half inch off or more on the lap top screen..for Sharpcap ..which is half a lappy screen...I have images upside down to each other stack...mind you I do crop a quarter of most finals because of poor framing...but they stack.
My stack has an hour more but I may have to go out but I will post those photos before midnight hopefully.
Alex
Perhaps a sub from a different night has been included accidentally and set as the reference frame. If the sub has been checked to have a good image of the object and the highest number of stars and is right clicked it can be set as the reference frame.
OK my poor old head is starting to get around some of this. Registration is just that: aligning the frames or rather the stars in the frames. So Alex and Raymo you are right: changing the registration threshold has no effect on my stacking problem, despite the cryptic message from DSS on the "only one frame to stack" warning. The second part of that says "and help DSS find a transformation between the reference frame and the others" which is Greek to me but seems again to apply to registration only.
So, if I stack the one frame I find the RGB/K window shows an S curve and a tall, narrow bell curve right at the bottom left hand end. If I move the bell curve up to the lower point of inflection of the S curve (which is my standard practice with stacked images anyhow) extra details pop up (which is the standard result).
All of which brings me back to the original problem: the registration process has not found enough stars to allow the stacking process to proceed. Is this perhaps a "fail safe" function to avoid stacking possibly misaligned frames?
Thus my question: can I override that and stack more than one frame because visual examination of the individual frames and the registration scores (low as they may be) does not indicate any alignment problem.
Kevin..please just act on my last post and your problems will just disappear.
The solution is simple you just need to do what I suggest...please just try it.
Alex
If the threshold for star detection is too high (ie: 2%) it will not detect enough stars to frame & therefore cannot align & register frames as it has no point of reference. The 2% figure is not a descriptor of low threshold it is setting a percentage of stars to use. Too low & it has insufficient point of reference.
Set the percentage higher (50% or more) as others have recommended & your problem should be resolved.
If the threshold for star detection is too high (ie: 2%) it will not detect enough stars to frame & therefore cannot align & register frames as it has no point of reference. The 2% figure is not a descriptor of low threshold it is setting a percentage of stars to use. Too low & it has insufficient point of reference.
Set the percentage higher (50% or more) as others have recommended & your problem should be resolved.
Thanks Alex and Carlton but you are missing the point. It doesn't matter whether the threshold is set at 2% or 98% or anywhere in between, DSS cannot find more than 4 stars on any of the frames and none on most. It appears to be something to do with the amount of (lack of?) contrast. Consequently, DSS decides there are insufficient points of registration and therefore it should not proceed with stacking.
Cheers
Thanks Alex and Carlton but you are missing the point. It doesn't matter whether the threshold is set at 2% or 98% or anywhere in between, DSS cannot find more than 4 stars on any of the frames and none on most. It appears to be something to do with the amount of (lack of?) contrast. Consequently, DSS decides there are insufficient points of registration and therefore it should not proceed with stacking.
Cheers
Kevin.
What is your current threshold setting?
Have you changed it up from 2% to 50%?
It can't get points of registration if you are at 2%.
DSS identifies stars as points of light where the center is the brightest point and the brightness reduces from the center outwards. If your stars are enough out of focus, the center of the star is not the brightest point. It is true that sometimes the smaller stars that are out of focus are so small that the darker center of the star is not resolved and therefore can still be detected as a star but that is not the case with the subs that you posted. This is why DSS cannot find enough stars to align the frames and hence why it refuses to do it. It doesn’t matter what percentage of doughnuts you tell it to look for, they’re still doughnuts.
DSS identifies stars as points of light where the center is the brightest point and the brightness reduces from the center outwards. If your stars are enough out of focus, the center of the star is not the brightest point. It is true that sometimes the smaller stars that are out of focus are so small that the darker center of the star is not resolved and therefore can still be detected as a star but that is not the case with the subs that you posted. This is why DSS cannot find enough stars to align the frames and hence why it refuses to do it. It doesn’t matter what percentage of doughnuts you tell it to look for, they’re still doughnuts.
Cheers
I replied to Kevin in the 3rd post and mentioned one of the main reasons why DSS won’t stack is due to stars being out of focus
Another problem could be you have tracking issues or coma issues with your stars if unguided or even guided
Your stars could be elongated slightly or odd shaped so DSS will reject them
DSS has a very rigid algorithm for assessing good and bad stars ( out of focus stars, eggy stars, slightly elongated stars etc....... )
It could be just poor data that’s causing rejection ??
Another thing to check , have you ticked the box rejection of hot pixels in the set up ??
Cannot think of anything else ?
Thank you everyone for your input. I detect a level of frustration with me commensurate with the frustration I am having with DSS!
The out-of-focus idea I shall have to follow up with past data. In fact Martin, I recall you pointed out that my stars in the images I posted on IIS a while ago were out of focus and elongated. However, DSS registered and stacked those without any problem.
I am holding on to my theory about lack of contrast for now and will contact the DSS developer about that. The thing that should counter that theory is that I would have thought it would be a constant problem for photographers in light polluted sites, but perhaps you all use LP filters or some other technique?
I suppose I should try re-installing DSS in case I have accidentally reset some basic function.
Cheers
Kevin
Here’s my DSS procedure I’ve been using for nearly 4 years in light polluted Sydney and dark skies South Coast using both DSLR and Cooled OSC cameras with and with out narrowband filters ( not light pollution filters )
Deep Sky Stacker basic procedures
Open Deep Sky Stacker
All tasks and settings are on the LHS column
“Open pictures files” and load your Raw (Cr) files or Fits files from your PC ( make sure you select the correct file type in the drop down to load into DSS )
Open “dark files” and load your darks
Open “flat files” and load your flats
Open “offset/bias files” and load them
Press Check all ( all files will be ticked or checked in the file list at the bottom ready for registering
Press “Register checked pictures”
Register Settings box opens up
“Actions tab”
Tick box - already registered picture
Tick box - Automatic detection of hot pixels
Tick box - Stack after registering
Select the best 90% to 95% pictures and then “untick this box” so you can check your Stacking Settings later ( I prefer to check later )
Under “Advanced tab”- star detection threshold make sure you tick the box “Reduce the noise by using a Median filter”. Then move the Star detection slider to 10% at first but try other settings like 30% or 50% as there may not be enough stars for DSS to detect and align. In some cases where you have poor data due to focus issues or bad tracking you may have move slider down to 5% or even the lowest setting at 2%.
I recommend between 50 and 150 stars , so increase or decrease the star detection threshold to achieve enough stars
NB: if your stacking FITS files from a dedicated Astro CMOS camera then you will find that Star Detection will be low say 50 to 100 stars when the star detection threshold is set at its highest or 2%
This will be worse when you use a narrowband or light pollution filter with your camera. As long as DSS detects at least 8 or 10 stars then it will register the frames and stack for you
“Recommended Settings button”
DSS give you the recommended setting highlighted in green based on the number and type of files to stack
“Stacking Parameters button”
Intermediate files
Only check FITS files box and Use all available processors box
Leave other check boxes clear or unchecked
Press OK then DSS will start registering files
After files are registered main screen will be blank then press “Stack checked pictures”
Stacking Steps box appears
Recommended Settings button
DSS gives you the recommended setting for stacking highlighted in green ( you can change them if you want to )
“Stacking Parameters”
Result tab - check Standard mode
Light tab - check Kappa Sigma clipping
Alignment tab - check Automatic
Intermediate Files tab - check FITS files
Cosmetic tab - don’t do anything
Output tab - check Create Output file, check Append a number to avoid file overwrite, check Create Output file in the folder of the reference frame
Check Use available processors
Press OK
Now Press OK in Stacking Steps
DSS will now stack files based on selected settings
After stacking, DSS will create an output image ready to save
“Important” - do not use DSS RGB level adjustments , leave stacked image as it is ( untouched linear stacked image )
After stacking, in “Processing section” click “Save picture to file” option
Save as window appears , select where you want it saved in your computer and file name etc
Save as type will be FITS image ( 32bit integer )
Under “Compression” below leave as none
Under “Options” below , bullet check - do not apply adjustments to the saved image
Click save and stacked fits file should be saved to your file location ready for Startools or other processing software
Martin and I ( amongst others ) have and still do image in Bortle 8 skies. Both with 8” newts at f/5 and f/4. Yes I use filters but have without and until recently Martin has not. Contrast is not the issue.
I will admit to a level of frustration yes. I’m trying to not to come across rude and my assistance is to serve no other purpose than to help a fellow astrophotographer.
Thank you everyone for your input. I detect a level of frustration with me commensurate with the frustration I am having with DSS!
The out-of-focus idea I shall have to follow up with past data. In fact Martin, I recall you pointed out that my stars in the images I posted on IIS a while ago were out of focus and elongated. However, DSS registered and stacked those without any problem.
I am holding on to my theory about lack of contrast for now and will contact the DSS developer about that. The thing that should counter that theory is that I would have thought it would be a constant problem for photographers in light polluted sites, but perhaps you all use LP filters or some other technique?
I suppose I should try re-installing DSS in case I have accidentally reset some basic function.
Cheers
My frustration turns on the fact you will not answer my simple question which I will repeat...
What is your setting ...the threshold setting???
Have you tried a stack at 50% at all or are you still stuck on "2% is ok"?...
I looked at your images you posted and even though you have stars that are out of focus I am confident there are sufficient "good" ones that DSS will register...to register you need a higher threshold than 2%..It has nothing to do with contrast.
All I would like from you is a simple reply to my question...if you insist on 2% then contacting DSS will confirm your view re contrast is wrong...
What is your threshold setting? Have you tried a stack with the setting at 50%?
If you do not give me a direct answer I will take it that you are trolling and wasting everyone's time...if you are genuine change your setting..
Perhaps it is time to let this thread go, as all the questions have been answered and reasonable advice provided. If there is a lack of understanding at the OP end getting upset is not going to fix that. Let it go.
because of poor framing...but they stack.
