108 replies to this topic

[deSitter]

Smoothness? You mean the focuser?
I compared it also with an uncoated Prinz 76mm F16. I rate this scope highly.
However the Chinese refractor gave a much sharper image - it was pretty obvious.
Perhaps it was just luck - will try again another night.

No, the optical figure. You can see it in the out of focus diffraction pattern. Smooth optics will show a very smooth outer ring. Rough ones will show "hair". It gets more involved, but that's a good start.

 

My 80mm f/11.4 Vixen could hardly be any smoother. It's up there with my AO scopes.

 

-drl

[Princess Leah]

Thanks again. I will check that out. That's very interesting.

[Princess Leah]

No, the optical figure. You can see it in the out of focus diffraction pattern. Smooth optics will show a very smooth outer ring. Rough ones will show "hair". It gets more involved, but that's a good start.
 
My 80mm f/11.4 Vixen could hardly be any smoother. It's up there with my AO scopes.
 
-drl

I just tried it at 70X on tree branches / silhouettes. No CA. Even with a 60mm F15 I see a very small amount of CA. Strange. The image was still bright despite the small exit pupil.

[Princess Leah]

Tried it again on Saturn/Jupiter. This time CA was virtually the same. However the Chinese made C80 was sharper - quite stunningly so, and brighter too.

 

I think there was a period in the 90s when Chinese optics reached a peak, before everything was made cheaper and more economical . I've noticed this also with the very early ST102s (F5).

[dave253]

I just had my ~1993 Vixen 80 on Jupiter; with a Japanese shorty Barlow and the generic 8-24 zoom,

excellent views with ca only barely visible outside focus. 
 

It’s a known good one though.

[Steve Allison]

My Chinese sourced C80, purchased at Goodwill for $10, is quite sharp and displays good spherical correction. Pretty close to the Celestron/Vixen version I used to own. But…the chromatic aberration seems noticeably worse.

 

Not a bad telescope for the price.

[navillus]

I recently got a used (very good condition) black Firstscope 80 "Made for Celestron in Japan".  It's on a nice Vixen alt-az mount with hardwood legs.  The optics are very sharp.  For me, it's the ideal grab-and-go telescope.  It is very light weight, so I can hold the whole kit and caboodle with one arm while opening and closing doors with the other.  I'm tempted to try it on a Polaris mount, but that would make it heavier and take away some of the portability.

 

For me, the only downside is the small (~25mm) finder.  Even with the legs fuly extended it's a bit hard on the neck pointing to objects above an altitude of about 40 degrees.   I think there was (is?)) a holder for a laser pointer.  I believe that would be a nice improvemt.  I'd like to hear comments form anyone who uses a laser pointer on the Firstscope 80.

 

Phil 

[Princess Leah]

Maybe use a 6x30 right angled finder?

[HagglePig420]

I own 3 of these, the optics in all are outstanding. Almost as sharp their big brother, my C102 fluorite but just with CA. One of the nicest 80mm achros out there. And that black tube and orange lettering is beautiful.