Celestron 9.25 vs. Classic 1970 orange 8 CelestronPosted By Phillip MacQueen |
Hi John,
I have a Nexstar 11, have looked though a Celstron 8" quite a few times during the period I've owned the 11", and have used a Celstron 9.25 once. It's interesting to compare the 9.25" to either the 8" or 11" because it's optically different. Although they are all f/10, the 9.25" has a slower primary mirror focal ratio and therefore a lower magnification secondary mirror. This results in a flatter field of view. My one real gripe with the 11" and (even more so the 8") is that the image quality degrades in the outer field of view with longer focal length eyepieces. This is very clear with a Pentax 20 mm XW, a TeleVue 13 mm ethos eyepiece, and a TeleVue 27 mm Panoptic. Some of the image quality degradation is due to other aspects of the telescope optical design (coma, in particular). You can determine that coma is only part of the story with those eyepieces because you can focus on a star in the other field and get a much sharper image out there while the central field degrades. My one view through a 9.25" was a number of years back, but the image quality over the full field of view impressed me.
You mention image quality as being important, so the 9.25" would be a good choice given your weight limitation.
The current Celestron coatings are so superior to the coatings in your current telescope that they will help you a lot, too. You'll get more light, but you'll also get more contrast because there won't be so much scattering and stray light. High contrast is worth a lot.
Regards,
Phillip
P.S. The new Meade aplanatic catadioptric telescopes (eg. LX200ACF) have good full-field image quality and coatings, too.
I have a Nexstar 11, have looked though a Celstron 8" quite a few times during the period I've owned the 11", and have used a Celstron 9.25 once. It's interesting to compare the 9.25" to either the 8" or 11" because it's optically different. Although they are all f/10, the 9.25" has a slower primary mirror focal ratio and therefore a lower magnification secondary mirror. This results in a flatter field of view. My one real gripe with the 11" and (even more so the 8") is that the image quality degrades in the outer field of view with longer focal length eyepieces. This is very clear with a Pentax 20 mm XW, a TeleVue 13 mm ethos eyepiece, and a TeleVue 27 mm Panoptic. Some of the image quality degradation is due to other aspects of the telescope optical design (coma, in particular). You can determine that coma is only part of the story with those eyepieces because you can focus on a star in the other field and get a much sharper image out there while the central field degrades. My one view through a 9.25" was a number of years back, but the image quality over the full field of view impressed me.
You mention image quality as being important, so the 9.25" would be a good choice given your weight limitation.
The current Celestron coatings are so superior to the coatings in your current telescope that they will help you a lot, too. You'll get more light, but you'll also get more contrast because there won't be so much scattering and stray light. High contrast is worth a lot.
Regards,
Phillip
P.S. The new Meade aplanatic catadioptric telescopes (eg. LX200ACF) have good full-field image quality and coatings, too.
