Hi all,
After processing almost 40 hours of data from a Bortle 4 sky of M106, I expected way more details to appear in the galaxy.
This image has been processed using BlurX, LHE, MLT and unsharp mask on the L layer before combining to HaRGB but zooming in, I find the galaxy still too blurry for all the hours of exposure I gave it.
The acquisition went smooth, with good seeing and no wind during all nights of capture (total RMS during guiding always below 0.7).
Convinced I can do better on the processing part, I am now investigating ways to pull out more details from my images and will attempt to drizzle my data before reprocessing it.
From my understanding, in order to drizzle, I need :
- to dither frequently (I do every 3 frames by 5 pixels)
- to be undersampled
The camera is use is the ASI2600 MM pro (pixel size of 3.76 microns, resolution of 6248 x 4176) and the scope is the Esprit 120 (120 aperture, 840mm focal length, f ratio :7 ; no reducer used in this example).
According to Astronomy.tools using this formula : ( Pixel Size / Telescope Focal Length ) X 206.265
With this setup, the resolution is about 0.92"/pixel, so slightly oversampled.
If applying the reducer (x0.77), the resolution is 1.21"/pixel, so no over -nor under- sampling.
According to RC-Astro MTF analyzer, I am undersampled in both setups, which convinced me to try to drizzle and then compare results (drizzle x2, crop factor 0.9). Once done, I believe I have to resample the image at x0.5.
For those unsing the Esprit 120 and ASI 2600, do you drizzle all of your pictures ? If no, when do you ?
Finally, regarding RC-Astro MTF analyzer, one component that has an impact over the sampling are the seeing conditions (from 0.5 to 4.00 arcsec).
I don't know how to calculate this but have read it is often defined by the FWHM.
How do I calculate it ?
In PI, I would extract the L component of a channel then run FWHMEccentricity analysis script on the stacked image (after running WBPP in non-drizzle mode) and then use this value to set up a manual PSF in BlurX. But should I run the script on a single frame (before stacking) to obtain a seeing value to input in RC-Astro MTF analyzer ?
Thanks in advance for any tips and insights!
After processing almost 40 hours of data from a Bortle 4 sky of M106, I expected way more details to appear in the galaxy.
This image has been processed using BlurX, LHE, MLT and unsharp mask on the L layer before combining to HaRGB but zooming in, I find the galaxy still too blurry for all the hours of exposure I gave it.
The acquisition went smooth, with good seeing and no wind during all nights of capture (total RMS during guiding always below 0.7).
Convinced I can do better on the processing part, I am now investigating ways to pull out more details from my images and will attempt to drizzle my data before reprocessing it.
From my understanding, in order to drizzle, I need :
- to dither frequently (I do every 3 frames by 5 pixels)
- to be undersampled
The camera is use is the ASI2600 MM pro (pixel size of 3.76 microns, resolution of 6248 x 4176) and the scope is the Esprit 120 (120 aperture, 840mm focal length, f ratio :7 ; no reducer used in this example).
According to Astronomy.tools using this formula : ( Pixel Size / Telescope Focal Length ) X 206.265
With this setup, the resolution is about 0.92"/pixel, so slightly oversampled.
If applying the reducer (x0.77), the resolution is 1.21"/pixel, so no over -nor under- sampling.
According to RC-Astro MTF analyzer, I am undersampled in both setups, which convinced me to try to drizzle and then compare results (drizzle x2, crop factor 0.9). Once done, I believe I have to resample the image at x0.5.
For those unsing the Esprit 120 and ASI 2600, do you drizzle all of your pictures ? If no, when do you ?
Finally, regarding RC-Astro MTF analyzer, one component that has an impact over the sampling are the seeing conditions (from 0.5 to 4.00 arcsec).
I don't know how to calculate this but have read it is often defined by the FWHM.
How do I calculate it ?
In PI, I would extract the L component of a channel then run FWHMEccentricity analysis script on the stacked image (after running WBPP in non-drizzle mode) and then use this value to set up a manual PSF in BlurX. But should I run the script on a single frame (before stacking) to obtain a seeing value to input in RC-Astro MTF analyzer ?
Thanks in advance for any tips and insights!