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C8TriColor vs C8 sand cast

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#26 bob midiri

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Posted 24 September 2019 - 10:09 PM

Well we had a fun time tonight at Mt Cuba with Dave Groski who was kind enough to take the time and DPAC these two telescopes. The most difficult part was actually trying to photograph with our cell phones and I-pads the the results. I started getting the hang of it with the photos, especially with the C8 sandacst as you can see here, we tested the TriColor C8 First and experimented on taking pictures, that didnt come out great but was a fair representation of what we saw, Got some what better with the photos of the C8 Sand cast which are included in this post see below. The long and short of it  is that both of these C8's have very nice figures, both exhibiting straight lines on the DPAC, the Sand cast version might have an over tightened Corrector plate putting a little stress on that corrector, but Dave was quite happy with what he saw. He felt that after we got the Sand cast version more closely collimated that the over figure was a little smoother then the tri-color, but that the overall correction of the TC was a little better, but that could change once i check the corrector plate, the centering of the secondary and get the collimation right on. The few times I have hd the chance to observe, it was clear to me that these two scopes were quite good, Dave tested my TriColor before and thought it one of the better C8's he had tested. Im sure Dave will elaborate more on what we saw tonight. Overall it was a fun and educational experience. Ill post picture of the Tri color in next post, images too big for this post

Attached Thumbnails

  • dpacC8SC1.jpg
  • DPACC8sc2.jpg
  • dpacc8SC3.jpg
  • dpacc8sc4.jpg

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#27 bob midiri

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Posted 24 September 2019 - 10:14 PM

Here is the DPAC of the C8 TriColor, we had more trouble getting pictures of what we saw, to me visually the DPAC was looked better then these, all the lines looked equal, but as Dave told me the Sandcast version the lines looked smoother , the  pictures are a fair representation, but I did not see that thickness in the second line from the right while looking visually, it was difficult trying to hold our phone at the right angle and elevation to get a picture

Attached Thumbnails

  • dpacc8TC1.jpg
  • dpacc8TC2.jpg
  • dpacc8TC3.jpg
  • dpacc8TC4.jpg

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#28 DAVIDG

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Posted 25 September 2019 - 09:19 AM

 Nothing like taking some measurements with a system that has reduced the variables so one can compare the results with confidence. So it was  great to see Bob again and test his two C-8 to see what the optical quality was in both scopes. 

    To summarize,  both scopes were well corrected for spherical aberration. No problems there. The tri-color C-8 had good collimation , well corrected for spherical aberration, but showed a small amount of roughness.

   The sand cast C-8 was also well corrector for spherical and smoother optics then the  Tri-color by a little bit  but the collimation was off a little. We tuned it up and got it better but not 100% perfect. When I have seen this in the past I've found the secondary not perfectly centered. So I told Bob to check that and then see if he could get it perfect. When the collimation is fixed both of these C-8 will give  excellent images  and any difference will not be from the primary optics.

  So within a few minutes of bench testing we knew what the quality of the optics were, with no guessing. 

 

             - Dave  


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#29 VictorMG

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Posted 01 August 2022 - 08:58 PM

Definitely holes in the forks are far superior, from my experience.  I've owned at least 10 of them. Currently,  I three C'8's, with holes in the forks, and a couple tricolors. I also own 2 hole in the forks, C5'. I have owned a couple orange,  solid fork c8's and the optical quality was inferior to those with holes.

 

The tricolor seems to be a bit superior. Unfortunately,  they are usually in bad shape. They are also very heavy. It is hard to find a descent one

 

One of my 3 orange, holed ones is especially great, refractor like sharp. This particular one came from the university of Ohio.  It seems Celestron sells universities the best of the best.

 

I would put any of my orange hole in the forks, c8's against hd's,  any day. 



#30 CHASLX200

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Posted 02 August 2022 - 05:53 AM

Never had a holes in the forks C8 but had many other types of all ages from the 70's to around 2004 and only one was what i would call freaky sharp. It was a black 1984 C8.  Wished you could have tested my 2004 made C8 as it was the worst ever.




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