Field of View Comparison 12" vs 8" Schmidt-Cassegrain Telescope: M20
| Object | The Trifid Nebula (M20), in Sagittarius |
| Telescope (Photo) |
Top:
Meade LX200GPS 12” SCT @
f/6.3 Bottom: Celestron 8" SCT OTA @ f/6.3 on Losmandy G11 Mount |
| Telescope (Guiding) |
Top: Meade LX200GPS 12" SCT @
f/6.3 (off-axis) Bottom:Televue 85mm refractor @ f/7 on Losmandy G11 Mount |
| Camera (Photo) |
Top: Canon 20Da DSLR Bottom: Canon 50D DSLR, with Hutech filter modification |
| Camera (Guiding) | Top: Meade
DSI II Pro w/PHD Guiding Bottom: Meade DSI III w/PHD Guiding |
| Exposure Detail | Top:
excluded-average combination of 15 images After: excluded-average combination of 17 images Both: sub-images exposed at 300 seconds each, ISO3200; RAW file conversion, full calibration (flat, dark, bias, and flat-dark), and initial image processing using ImagesPlus 3.80; final image processing using Photoshop CS3 |
| Location | Cincinnati Astronomical Society's Dark-Sky Site (Adams County, Ohio) (N38.876, W83.464) |
| Date | 09/12/09 |
| Comments | The images in this sequence were taken at the same time on the same night at the same site using different optical tube assemblies (OTAs). The Canon 20Da image was resized to the same pixel dimensions as the Canon 50D image, although this affected only pixel density and not image dimensions. Next, identical crops were taken from the original images. This comparison shows how the different focal lengths of the two OTAs affects image size. |
