Quote:
Originally Posted by Camelopardalis
So the thing you've got to bear in mind is that at f/10, the diameter of the airy disc is quite large. If you're expecting stars to be small pinpoints, you'll be disappointed. Bahtinov masks are pretty effective at getting good focus. The stars will be what they will be.
With the reducer, you'll get smaller stars...because the diameter of the airy disc is proportional to f-ratio.
The reduced focal length will probably be a little more usable, all things considered, and your exposure times will be need to be shorter to achieve a similarly bright image, compared to f/10.
A disadvantage with the reducer is that the illumination suffers across the field of view, especially with a relatively-large APS-C sized sensor.
This game is all about trade-offs  |
I think the airy disk of this particular telescope is too large for the sensor in the 7D, hence the lack of razor sharp stars. It is why I was thinking the camera is oversampling.
Seeing as the camera is becoming more troublesome from a noise and hot pixel perspective (all correctable in post), I'd need something like a 5D MkII to come close to being a better match for the SCT.