Presumably DSS in some sense measures transparency. Same object, same exposure on DSLR unmodified - one night registration score 18000 another night score 33 at which DSS says "only one frame will be stacked do you wish to continue? [you idiot!]"
But the data is there when I wind down the slider bar at top right of screen (contrast? luminance? adjustment).
How do I get DSS to detect that data? I have star detection threshold set at lowest i.e. 2%. All registration and stacking settings standard as far as I can see.
Any suggestions greatly appreciated.
I have never ever changed any DSS settings from the standard. I have very rarely seen that message regarding only one frame to stack. Have you run the sub files through the Image Grader first, to assess the relatively quality?
BTW star detection threshold should not be that low, try 25% min. But it depend on the target and relative population of stars in the field of view. Your effectively selecting the number of stars to register against.
When in the advanced tab start out with the star detection slider set at about 60 or 70%, [not 2%], compute, and if you get a huge number of stars detected [hundreds or thousands] go to a higher percentage and compute again, repeat until you have around 50-100 stars detected; that is all DSS
needs. The more stars detected the slower DSS will run, at 2% it will quite
possibly not even attempt to align and/or stack such vast numbers of stars,
and even if you have a premium computer it will run at glacial speed, like
many hours to stack say 50 subs, as opposed to minutes. Hope this helps.
raymo
Thanks for the replies.
I probably made my question too complicated.
My problem is DSS will not recognise more than 3 stars on frames that show dozens when viewed on any normal photo viewer software.
Is there any adjustment I can set on DSS?
Thanks for the replies.
I probably made my question too complicated.
My problem is DSS will not recognise more than 3 stars on frames that show dozens when viewed on any normal photo viewer software.
Is there any adjustment I can set on DSS?
yes, the star detection threshold
slide it to the right or left and see if it makes a difference
it's in the settings
It's in "advanced" .. when you go to stack...I used it years ago and could not understand why recently I could not find it..it's not anywhere on the left...I notice mine is at 60 but I suggest you select say 8 light frames to stack , even five, and try it from 15 up to 70 and see if you can notice a difference...good luck.
Alex
I have tried every available setting. Attached file are the one frame that DSS lets me stack - tried RAW and JPEG. Why can't I stack the other 39 similar ones??
Maybe Ryan but this is my focus image with mask. DSS will register it just won't stack more than one frame presumably because it scores them all in single digits. It is something to do with the where it puts the lights on the luminance curve, which in turn is something to do with the atmospheric conditions I think.
Maybe Ryan but this is my focus image with mask. DSS will register it just won't stack more than one frame presumably because it scores them all in single digits. It is something to do with the where it puts the lights on the luminance curve, which in turn is something to do with the atmospheric conditions I think.
Well that looks absolutely bang on. Is there any chance your focuser slipped after focusing ? I could be wrong but just going off the images you posted that is exactly what it looks like with doughnut stars.
You didn’t happen to leave the focuser in the same position from the previous night that worked ? That focus shot was from that particular session ?
I don't know if the mask is perfectly symmetrical, but the spike 6.30am
to 12.30pm has in its lower half a smaller gap to its right than to its left,
but in its upper half the gap difference is much less obvious, in fact barely
detectable visually. Whatever the reason, the stars are definitely out of focus,
but not enough IMHO to prevent DSS from doing its thing.
raymo
P.S. I just thought, the image is extremely noisy, I wonder if that could be enough to
confuse DSS, for example, the noise on the target itself looks like hundreds of pinprick stars,
and that pattern would be different on each sub; but maybe I'm overthinking it.
Last edited by raymo; 11-11-2020 at 12:47 AM.
Reason: more text
I have tried every available setting. Attached file are the one frame that DSS lets me stack - tried RAW and JPEG. Why can't I stack the other 39 similar ones??
Zooming in on that image (in post #8) shows that the stars are out of focus and exhibit coma tails. Did you grade those subs like I suggested? There are regions of the Image where the stars look like donuts. Have you looked closely at more of the subs? I would be closely eyeballing each one, and grading the stack.
Alex, I set the slider at 2% the lowest available. It isn’t that; it is as if DSS is saying: “Nah, the image is too dark”. The stars are there but you have to wind up the contrast to see em. Interestingly, the faint outline of the galaxy (NGC55) is visible on the camera screen as well as the stars so my theory (built on near total ignorance of digital photography – I learned photography in the old silver halide days) is that DSS requires some minimum level of contrast between sky and stars to do its thing. But then my site does not have any light pollution as such. What it does have is a location with surrounding hills and the Murrumbidgee River about 5kms away: fogs are not all that common but otherwise clear nights can certainly sometimes look “murky”, my best astrophotography has been done on winter nights in drought.
I agree about the focus issues and I should probably do more masked test shots each night. Even with a 2X magnifier on the viewfinder my tired old eyes (even the good one) struggle to get sharp focus and sometimes even tightening of the focus lock seems to shift the focus slightly. Again, I wonder whether these bad seeing and transparency nights might create some distortion in 30s subs.
However, as Raymo says, out-of-focus doesn’t stop DSS stacking just gives you an out-of-focus stack (which is very annoying when it happens).
In summary I guess what I am asking is can I force DSS to stack light frames which have a score below its self-imposed minimum, or somehow pre-process the RAW images to push them up the luminance curve or is there some other software to try? I hate to throw away data from my relatively rare moonless and cloudless nights (proximity to the High Country gives us more cloud than further West). I apologise to city astrophotographers who have more difficulties for my whinging.
Hi Kevin
Please try this.
Take only five frames as this is a test and proceed to stack them but before you do go into the advanced setting on one of those squares that appear in the middle of your screen that has "advanced settings" go in there and change your star number settling to say 50 % and try that..irrespective of your various observations that 2% should work I hope you will find 50% does work and you will find all five frames stack...if they do try again using all your subs.
I have found that the lowest setting simply does not work..you must change it ...
Alex
As frustrating as it is, if you have to throw out an entire night because something went wrong, sadly it won’t be your last. We’ve all done it. It isn’t a total loss because you can learn from it.
Second, begin with the end in mind ( steven covey ). If you stack out of focus subs, you won’t get a good image anyway.
There will always be other nights. The universe isn’t going anywhere
Kevin, I should slap myself on the forehead. At 2% DSS is set on its minimum
sensitivity, so no wonder it is not detecting enough stars to do any aligning or stacking. Please start at around 60 or 70% as I said before, and all should be well. As I said 50 to 100 stars is plenty.
raymo
What others have said: move the threshold up.
The question have been asked multiple times now: how many stars did DSS tell you if "sees" after moving the threshold?
I am stacking at the moment and unable to read what DSS says about the threshold but I do recall that it to me was misleading in that I tried a low setting as that seemed the best idea in view of the DSS notes however I found it really seems the reverse to how I read the notes...I know at the time I thought it seemed contrary to the DSS notes but I finally set it at 70%..I don't know why at the time I went with 70% but I have not changed it to this day and after I have never got the can only stack one frame message.
Looking at the image you posted I can tell you that I have stacked worse...I will bet you ten bucks that at 70% you will have all frames stacked...well no cause I can only take your money.
If I can I will post a photo of the box where it shows "advanced" and also a picture of my setting at 70%...at the moment I am unable as I am stacking 308 light frames of the Spider thru the 80mm with the Nikon.
