Briefly. The images I took using long exposure noise reduction (LENR) which were then subject to flat division and by necessity bias subtraction were evidently clipped while the stacked image with background extraction in Siril "looked OK".
I compared this to a stack calibrated traditionally in Siril and as expected processing in ST was uneventful. AutoDev and Wipe producing predictable results with default settings.
The LENR images on the other hand could not be stretched and appeared posturised / binarised in AutoDev. The best I could do was to import the Siril background extracted stretched image into ST and use tools that avoided other than minor tweaks. Noting that colour calibration in Siril was also unable to produce an acceptable result.
No. I will not be using LENR again.
LENR with a Fuji XT-1
Re: LENR with a Fuji XT-1
There's another reason, why one may not want to use LENR: valuable imaging time gets lost when taking darks after each image.
AFAIK taking darks is not a common practice when imaging with a DLSR, because it is difficult to match sensor temperature. Instead it is possible to use bias and flat-darks only. For me, taking flat-darks had no noticeable benefit, therefore I simply use bias frames instead of flat-darks most times.
Best regards, Dietmar.
AFAIK taking darks is not a common practice when imaging with a DLSR, because it is difficult to match sensor temperature. Instead it is possible to use bias and flat-darks only. For me, taking flat-darks had no noticeable benefit, therefore I simply use bias frames instead of flat-darks most times.
Best regards, Dietmar.
Re: LENR with a Fuji XT-1
Quite right, Dietmar. And post processing is limiting apart from any data improvements that LENR may have to offer otherwise. I prefer to take darks and flats for longer exposures wirh the XT-1 with bias frames to calibrate only the flats. A failed experiment with an interesting twist.
Re: LENR with a Fuji XT-1
Hi,
Using mostly 30s - 90s Subs, I'm taking 100 darks when dismantling the scope after the session, so the DSLR has got something to do:-) The sensor temperature is not so much of an issue. It takes 7K sensor temp difference to result in doubling the noise level, but usually the sensor temperature will remain pretty stable within 2 K, once settled after a few exposures. An average of 100 Darks provides a decent Master dark which includes the BIAS but also allows the stacker to identify hot pixels for a bad pixel map. If You're doing longer exposures, at least 20-30 Darks should do.
Using mostly 30s - 90s Subs, I'm taking 100 darks when dismantling the scope after the session, so the DSLR has got something to do:-) The sensor temperature is not so much of an issue. It takes 7K sensor temp difference to result in doubling the noise level, but usually the sensor temperature will remain pretty stable within 2 K, once settled after a few exposures. An average of 100 Darks provides a decent Master dark which includes the BIAS but also allows the stacker to identify hot pixels for a bad pixel map. If You're doing longer exposures, at least 20-30 Darks should do.
Re: LENR with a Fuji XT-1
True. I haven't taken that many darks since cooling my old 450D. And while there is a tendency to think that darks are unnecessary with cooled data they are useful for removing hot and cold pixels- as few as 3 is enough for that purpose. On occasions a single dark has done the job.
The Fuji is remarkably good for short exposures but develops a horrible temperature gradient otherwise. Fortunately, the sensor is mounted metal to metal and with an aluminium body stripped of the grip material a cooling fan taped to the base of the camera is all that's needed to remove the residual heat. The results are acceptable with dithering.
The Fuji is remarkably good for short exposures but develops a horrible temperature gradient otherwise. Fortunately, the sensor is mounted metal to metal and with an aluminium body stripped of the grip material a cooling fan taped to the base of the camera is all that's needed to remove the residual heat. The results are acceptable with dithering.