Deep Sky Stacker Issues
Dec 18, 2015 22:34:53 #
Stars and DSS
It may just be my computer(s) and my experiences with DSS but I would suggest that you select a min of 40 stars....and you do not need or want more than 100 for DSS to successfully align your images.
So, when you have loaded your images and you click "Register Checked Images" the tab "Advance" is selected....and then click on "Compute The Number of Detected Stars" move the slider all the way to the left and see what you have. If fewer than 40 stars is the result. I would stop there. Even though you may see more stars in your image....DSS is looking for sharp stars than can be stacked, one on top of the other. A good well focused image will result in 1,000's of stars when the slider is to the left. Move the slider to the right gradually and compute. When you get to the range 40 to 100 put the brakes on and move on with your settings.
In my own experience - the most important support files are the flats and bias frames....esp for DSLR shooters.
For those of you who are unsure of how many and how to take these supporting files ..here is my summary
They below are called Calibration frames.
Darks - no less than 20 and 50 works well for me. Use the same settings you used for your lights (subs) change nothing. The only thing you must do is cover your telescope with a lens cap so NO light enters the scope and strikes the sensor. These darks are going reveal your sensor's noise - when your darks are added to DSS, this noise is calibrated and subtracted from your final calibrated LIGHT frame leaving a clean image. The reason for so may need DARKS is the randomness of noise both color noise and luminosity noise...the more of these you have...the great the chance this crap will be removed from your final "Light frame."
BIAS - Do not change a thing EXCEPT - select the fastest shutter speed your camera has - My Nikons have 1/8000 of a second...my CCD camera 1/15 of a second. Again, the scope needs to be covered. Unlike DARK frames, temperature is unimportant but I take these at the same time I take the DARKS....at 1/8000 of a second, you can take 50 in minutes. When you raise the ISO on your camera you increase the sensitivity of your sensor to capture light....but with this gain comes both noise and sensor signal readout - this can take the shape of banding and gradients as light does not enter the scope and distribute itself evenly across the sensor. Just get use to not excepting less than 50 and if you have a lot of banding issues up that to 200 plus. Other than storage, and calibration time, there is no limit - the more the better.
Once I have the above, I grab my laptop, put a bar-b-que cover on my kit (unless rain is expected), and I transfer the images to folders LIGHTS, DARKS, BIAS and get ready for tomorrow morning after I have taken my FLATS.
The next morning I bring a white T-shirt to cover the end of my scope (lens) and use a rubber band to hold it tight with no wrinkles. Since my scope is parked - it is facing north and ready for FLAT frams. Use Aperture priority, leave the ISO the same...Temperature is unimportant. Take a BUNCH 50 plus. If you are using a DSLR, you will have vignetting - much more than you think could occur. Also, sensors collect dust - our optical trains do as well. These support files are used to subtract this crap from your master LIGHT frame. The more you have the better. But it is important tht you do not change your scope and camera from the night before - do not change FOCUS or take camera off the kit...that is why I just cover and leave to the next morning. Start taking your FLATS and look at your LCD screen you will see the vignette...make sure your histogram has zero clipping.
Whew - guys I realize that most of you have no need for this info but lately I have been getting messaged about DSS issues and disappointments with results. So, I thought for those who have fought taking these calibration frames that I would make my case.
Just try it!
It may just be my computer(s) and my experiences with DSS but I would suggest that you select a min of 40 stars....and you do not need or want more than 100 for DSS to successfully align your images.
So, when you have loaded your images and you click "Register Checked Images" the tab "Advance" is selected....and then click on "Compute The Number of Detected Stars" move the slider all the way to the left and see what you have. If fewer than 40 stars is the result. I would stop there. Even though you may see more stars in your image....DSS is looking for sharp stars than can be stacked, one on top of the other. A good well focused image will result in 1,000's of stars when the slider is to the left. Move the slider to the right gradually and compute. When you get to the range 40 to 100 put the brakes on and move on with your settings.
In my own experience - the most important support files are the flats and bias frames....esp for DSLR shooters.
For those of you who are unsure of how many and how to take these supporting files ..here is my summary
They below are called Calibration frames.
Darks - no less than 20 and 50 works well for me. Use the same settings you used for your lights (subs) change nothing. The only thing you must do is cover your telescope with a lens cap so NO light enters the scope and strikes the sensor. These darks are going reveal your sensor's noise - when your darks are added to DSS, this noise is calibrated and subtracted from your final calibrated LIGHT frame leaving a clean image. The reason for so may need DARKS is the randomness of noise both color noise and luminosity noise...the more of these you have...the great the chance this crap will be removed from your final "Light frame."
BIAS - Do not change a thing EXCEPT - select the fastest shutter speed your camera has - My Nikons have 1/8000 of a second...my CCD camera 1/15 of a second. Again, the scope needs to be covered. Unlike DARK frames, temperature is unimportant but I take these at the same time I take the DARKS....at 1/8000 of a second, you can take 50 in minutes. When you raise the ISO on your camera you increase the sensitivity of your sensor to capture light....but with this gain comes both noise and sensor signal readout - this can take the shape of banding and gradients as light does not enter the scope and distribute itself evenly across the sensor. Just get use to not excepting less than 50 and if you have a lot of banding issues up that to 200 plus. Other than storage, and calibration time, there is no limit - the more the better.
Once I have the above, I grab my laptop, put a bar-b-que cover on my kit (unless rain is expected), and I transfer the images to folders LIGHTS, DARKS, BIAS and get ready for tomorrow morning after I have taken my FLATS.
The next morning I bring a white T-shirt to cover the end of my scope (lens) and use a rubber band to hold it tight with no wrinkles. Since my scope is parked - it is facing north and ready for FLAT frams. Use Aperture priority, leave the ISO the same...Temperature is unimportant. Take a BUNCH 50 plus. If you are using a DSLR, you will have vignetting - much more than you think could occur. Also, sensors collect dust - our optical trains do as well. These support files are used to subtract this crap from your master LIGHT frame. The more you have the better. But it is important tht you do not change your scope and camera from the night before - do not change FOCUS or take camera off the kit...that is why I just cover and leave to the next morning. Start taking your FLATS and look at your LCD screen you will see the vignette...make sure your histogram has zero clipping.
Whew - guys I realize that most of you have no need for this info but lately I have been getting messaged about DSS issues and disappointments with results. So, I thought for those who have fought taking these calibration frames that I would make my case.
Just try it!
Dec 19, 2015 00:02:17 #
Dec 19, 2015 02:49:56 #
Dec 19, 2015 08:05:58 #
Albuqshutterbug wrote:
Did it as you described.
New result posted.
New result posted.
I just saw your Orion image -> and it's impressive! Very, very, nice! The downside is - more hard drive space.
Dec 19, 2015 09:06:09 #
Another thingie....
You can build a library of Darks and Bias frames. If you have bad skies and cannot shoot - start shooting Darks at various ISO's that you are inclined to use and exposure times that you are also inclined to use. Me mindful of the temperature when you took them...folder them and label folder with TEMP, ISO, and Shutter
And after every shoot - if you take new set of Darks - add them to your Dark Library folder.
Darks_54d_ISO1250_30sec
For me...the Darks are the only ones I Library as Bias frames because of the high shutter speed can be taken in a few minutes.
Flats - never library them as dust and crap can get on your optical train and sensor from shoot to shoot. They are fast as well.
Also, i stayed up most of the night shooting (fell asleep at the computer at some time) and this morning early - first light - I went out and shot the flats (aperture priority) - if you have a SCT with a F/10 aperture or refractor at say, F/7 - then set your camera to either F/10 or F/7 and let the camera decide the shutter speed. But this morning I didn't add the T-shirt, just shot the sky bare naked and you can get buy with this....if you wait to late and the sky gets to bright - you need to add the shirt to dumb down the light some.
You can build a library of Darks and Bias frames. If you have bad skies and cannot shoot - start shooting Darks at various ISO's that you are inclined to use and exposure times that you are also inclined to use. Me mindful of the temperature when you took them...folder them and label folder with TEMP, ISO, and Shutter
And after every shoot - if you take new set of Darks - add them to your Dark Library folder.
Darks_54d_ISO1250_30sec
For me...the Darks are the only ones I Library as Bias frames because of the high shutter speed can be taken in a few minutes.
Flats - never library them as dust and crap can get on your optical train and sensor from shoot to shoot. They are fast as well.
Also, i stayed up most of the night shooting (fell asleep at the computer at some time) and this morning early - first light - I went out and shot the flats (aperture priority) - if you have a SCT with a F/10 aperture or refractor at say, F/7 - then set your camera to either F/10 or F/7 and let the camera decide the shutter speed. But this morning I didn't add the T-shirt, just shot the sky bare naked and you can get buy with this....if you wait to late and the sky gets to bright - you need to add the shirt to dumb down the light some.
Dec 19, 2015 11:03:42 #
nikonshooter wrote:
Another thingie.... br br You can build a library... (show quote)
Another tip. My cameras have a feature called auto rotate. This causes the image to always be presented right side up in the editing SW. For astrophotography, you want this setting turned OFF. If it is ON and you shoot some images, and some darks, there is a chance that the camera is rotated enough that the image rotates, and you are left with a question of whether to rotate clockwise or counter clockwise for the dark to match the image. If it is turned OFF, this problem never occurs.
Dec 19, 2015 11:07:28 #
JimH123 wrote:
Another tip. My cameras have a feature called auto rotate. This causes the image to always be presented right side up in the editing SW. For astrophotography, you want this setting turned OFF. If it is ON and you shoot some images, and some darks, there is a chance that the camera is rotated enough that the image rotates, and you are left with a question of whether to rotate clockwise or counter clockwise for the dark to match the image. If it is turned OFF, this problem never occurs.
Good point. The newer Nikons do that as well.
Dec 19, 2015 14:14:49 #
My D3300 has manual rotation....
Even if getting the shot means standing on my head. :shock:
:lol: :roll: :idea:
Even if getting the shot means standing on my head. :shock:
:lol: :roll: :idea:
Dec 19, 2015 16:08:37 #
SonnyE wrote:
My D3300 has manual rotation....
Even if getting the shot means standing on my head. :shock:
:lol: :roll: :idea:
Even if getting the shot means standing on my head. :shock:
:lol: :roll: :idea:
If you want to leave it as it is....DSS will sort out the orientation and do the rotation for you. But it is a good idea to disable this if you can....one less thing for DSS to do.
If you want to reply, then register here. Registration is free and your account is created instantly, so you can post right away.