The Grim must have a significantly larger field of view, and there are many objects that are just to large for it, it bet the 70 has a longer list.
The trib article mentioned that Mike seemed a little surprised by the small field of view with 1st light. As a preference I prefer the faster optics like f4 rather than f6. Ah, I get it. I was referring to the theoretical resolution of an
unobstructed aperture, wheras you and Erik were talking about the effects of diffraction caused by a secondary obstruction. But if you assume the 40-inch in the argument to be of the same optical configuration, with a similar sized secondary by percentage of aperture, we are back on an even playing field. And calling effectively a 41 inch aperture is misleading without specifically referring to resolution.
I consider myself schooled on this point. Thanks, Brent.
The Grim does have the same limitations of field of view, but because it is driven, that limitation isn't so bad. Large objects still cannot be seen in a single FOV. One of the penalties of long focal length, with generally comes with large aperture.
On Tue, Oct 29, 2013 at 2:39 PM, Brent Watson <brentjwatson@yahoo.com>wrote:
The 41 inch aperture comes from the rule of thumb that resolution is approximated by the diameter of the primary minus the diameter of the secondary.
Utah-Astronomy mailing list http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy
Send messages to the list to Utah-Astronomy@mailman.xmission.com
The Utah-Astronomy mailing list is not affiliated with any astronomy club.
To unsubscribe go to: http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy Then enter your email address in the space provided and click on "Unsubscribe or edit options".