fredvanner
Well-known member
Equipment:
Telescope: Evoguide 50ED (f=242mm nominal, 268mm astrometric) with field flattener
Mount: HEQ5-R Pro
Camera: ZWO ASI2600C (pix 3.76um)
Capture software: APT
Location: Back yard, Wells, Somerset, UK
Date: 4-5 Jun 2021
120 x 60s lights (dark x 20, flat (Aurora EL) x 50)
Calibrated, integrated, drizzled (x2) and post-processed in Pixinsight.
Full xisf here
With a brief two hour window of summer darkish-ness, I decided to try out my Evoguide guidescope as an imaging scope. With the S/W field flattener fitted I can't see any easy way to get a filter into the optical path (it all screws together at matched imaging distance), so this is without my usual LP filtering.
I processed with standard integration, CFAx1 drizzle, and CFAx2 drizzle.
I calculate the Rayleigh angular resolution to be ~2.8" (which is probably close to the seeing on the night). The pixel size is ~2.89" (undrizzled), ~1.45" (x2 drizzle).
Processing with FWHMEccentricity, the averaged FWHM is:
This shows that even if the image looks undersampled, drizzle can't beat the basic system angular resolution limit.
Telescope: Evoguide 50ED (f=242mm nominal, 268mm astrometric) with field flattener
Mount: HEQ5-R Pro
Camera: ZWO ASI2600C (pix 3.76um)
Capture software: APT
Location: Back yard, Wells, Somerset, UK
Date: 4-5 Jun 2021
120 x 60s lights (dark x 20, flat (Aurora EL) x 50)
Calibrated, integrated, drizzled (x2) and post-processed in Pixinsight.
Full xisf here
With a brief two hour window of summer darkish-ness, I decided to try out my Evoguide guidescope as an imaging scope. With the S/W field flattener fitted I can't see any easy way to get a filter into the optical path (it all screws together at matched imaging distance), so this is without my usual LP filtering.
I processed with standard integration, CFAx1 drizzle, and CFAx2 drizzle.
I calculate the Rayleigh angular resolution to be ~2.8" (which is probably close to the seeing on the night). The pixel size is ~2.89" (undrizzled), ~1.45" (x2 drizzle).
Processing with FWHMEccentricity, the averaged FWHM is:
| process | FWHM(pix) | FWHM (arcsec) |
| Integrated: | 4.429 | 12.8 |
| x1 driz: | 4.276 | 12.4 |
| x2 driz: | 8.277 | 12.0 |
This shows that even if the image looks undersampled, drizzle can't beat the basic system angular resolution limit.