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C8TriColor vs C8 sand cast

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#1 bob midiri

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Posted 08 September 2019 - 06:09 PM

Well Im all set up outside to do a little comparison between my C8 TriColor of known optical quality (Thanks to David G DPAC) vs a new family member a C8 sand cast. Today I made a chord for the newer member with a cinch jones plug, both scopes are set up outside acclimating, and of course the clouds have rolled in, so this may need to be done on another day. But at least the pictures looked good

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#2 bob midiri

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Posted 08 September 2019 - 06:10 PM

2nd picture

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#3 bob midiri

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Posted 08 September 2019 - 07:18 PM

Oh well got about 5 minutes in between both scopes before total overcast,  it looked close using 24 panoptic and 13mm t6 Nagler,  will need a longer session to check collimation etc before a fair eval can be accomplished


Edited by bob midiri, 08 September 2019 - 07:51 PM.


#4 CHASLX200

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Posted 09 September 2019 - 05:19 AM

Oh well got about 5 minutes in between both scopes before total overcast,  it looked close using 24 panoptic and 13mm t6 Nagler,  will need a longer session to check collimation etc before a fair eval can be accomplished

Maybe the first few years were the best C8's ever made?  Every orange C8 i had was not that good, but made after 1977. I never had a holes in the forks C8.


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#5 bremms

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Posted 09 September 2019 - 07:41 AM

I have two orange ones. A Sandcast from 74 and one made in early79.  Both are the best examples of C8's Ive owned or even used. funny thing is that I had the mirrors recoated on the 79 and was very careful with reassembly. The 79 has very good spherical correction and is reasonably smooth. The 74 has just a hair of undercorrection, but it is very smooth for a C8. The 79 is good enough that it makes me think about selling some other mid size scopes.


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#6 kansas skies

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Posted 09 September 2019 - 07:11 PM

I have two orange ones. A Sandcast from 74 and one made in early79.  Both are the best examples of C8's Ive owned or even used. funny thing is that I had the mirrors recoated on the 79 and was very careful with reassembly. The 79 has very good spherical correction and is reasonably smooth. The 74 has just a hair of undercorrection, but it is very smooth for a C8. The 79 is good enough that it makes me think about selling some other mid size scopes.

I feel pretty much the same about the '78 C8 I purchased a few years back. I still can't believe the amount of scope I got for the money. As I've mentioned before, when the time comes to pare down, this scope (along with my Celestron/Vixen C80 refractor) will be the last to go.

 

Bill


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#7 Joe Eiers

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Posted 10 September 2019 - 12:11 AM

I just let go of a 1974 C8 and the optics were excellent.  So far, in my experience the sand cast scopes have always been at least very good or better.  I saw plenty of the late 70's early 80's that varied, but generally were quite good.   My 75' C14 is outstanding.

  Joe


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#8 scopelover

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Posted 10 September 2019 - 12:55 AM

My ‘74 C14 is also outstanding ..... Some of the very best planetary viewing I’ve ever had, including very large refractors ....

...Only outdone .... so far, and rather in the extreme... ... by Lockwoods personal 20” f/3 !!!!!!! a few years back at WSP!!!!

I've NEVER seen Saturn like that before or since , and his scope SMOKED every optic .... obliterating 10” TMB’s and 7” AP’s ...

Yep, superb optics and aperture can’t be beat !!!

 

in the meantime, my C14 is terrific.


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#9 CHASLX200

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Posted 10 September 2019 - 05:09 AM

Big Newts with super optics will always win out over smaller APO's and SCT's.



#10 MJB87

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Posted 10 September 2019 - 07:51 AM

Let's stay on topic. If you want to have a discussion of relative optics of Newtonians vs. APOs vs SCTs I suggest you create a new topic in the appropriate forum. Thanks.


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#11 Terra Nova

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Posted 10 September 2019 - 09:37 AM

I’ve had three of the orange tubes, my keeper and the best one I’ve ever had is my 2nd Quarter 77 early diecast.


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#12 Joe Eiers

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Posted 15 September 2019 - 09:49 PM

Still anxiously awaiting for more data!  

  Joe



#13 bob midiri

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Posted 16 September 2019 - 02:43 PM

Me too Joe, as soon as Im off this bad stretch of night work, ending Next Monday and some clear skies !! Believe me haven't forgot and quite anxious to get my two Classics under the stars again!!



#14 DAVIDG

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Posted 16 September 2019 - 03:05 PM

 These comparison are interesting but just remember your comparing only one example of each type. So I would caution one in drawing conclusion that in general one type  is better than another.  In my opinion a better comparison would be to provide the optical bench tests results. That would tell you exactly the quality of the optics with no influence from seeing, eyepiece type, diagonal, cool down time, personal bias etc etc.

   Bob brought his TriColor up to Mt Cuba Observatory were I tested via Double Pass Autocollimation about a year ago. It was one the best C-8 I have tested.  So if it falls short  against the sand cast version I sure would like to see what the quality of those optics are when benched tested. The same is true if the sand cast turns out to be not as good as the tri-color since that would show exactly what the issue is. If it is tie again bench testing would show if  they really do have the  same quality of optics or for some other reason they tested the same on the sky. 

  So again just be cautious on exactly what is being proven out when you read about the results of one of these comparisons using what is seen in the eyepiece, since there are many variable that can skew the results. 

 

                               - Dave 


Edited by DAVIDG, 16 September 2019 - 04:54 PM.

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#15 rolo

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Posted 16 September 2019 - 03:21 PM

I've had three 72's. One was like Bob's, the best I've DPAC tested. The other two did not test as good by considerable margin. You just gotta test them to know what you got. SCT's are like box of chocolates...you never know what you're going to get.


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#16 bob midiri

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Posted 16 September 2019 - 03:22 PM

Dave maybe some evening next week or week after I can bring them both down to you,. One thing I have noticed with the sand cast is there is very minimal focus shift, and the optics are sharp the few times I had a chance to compare to the TriColor. Bob


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#17 rolo

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Posted 16 September 2019 - 03:31 PM

I've had and tested dozens of Celestrons and I found no consistent anything between them. Everything varies, optics, mechanics, focus shift etc. Buy, test, repeat. 


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#18 John Higbee

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Posted 16 September 2019 - 08:04 PM

Mine is from second quarter 1976, right at the point that Celestron shifted from sand cast to die cast mounts.  One of the options that Celestron offered at that point was an optical test report on the scope, using an interferometer, autocollimation (the "3 bars on the Ronchi screen"), the diffraction disk both inside and outside the point of focus, photographs of the tests, and test explanations/analyses for each test, specific to my C8 (ser # 256666)...signed by Tom Johnson (President, Celestron).  I still have it today.

 

Sent a copy of the report to DavidG and Ron Midiri...David looked closely at it, pointed out some exaggerations in the text, and factors shown by the photographs, and said that despite the report exaggerations, its optics were still around 1/8 wave...which bore out the superb views it has given me for almost 44 years!

 

C8 v1.jpg

 

vinemoon (3).jpg

 

vinemoon (5).jpg

 

(Moon pictures were taken Saturday 7 August, at prime focus, with a Galaxy S8 phone).  


Edited by John Higbee, 16 September 2019 - 08:08 PM.

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#19 rolo

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Posted 17 September 2019 - 07:01 AM

Mine is from second quarter 1976, right at the point that Celestron shifted from sand cast to die cast mounts.  One of the options that Celestron offered at that point was an optical test report on the scope, using an interferometer, autocollimation (the "3 bars on the Ronchi screen"), the diffraction disk both inside and outside the point of focus, photographs of the tests, and test explanations/analyses for each test, specific to my C8 (ser # 256666)...signed by Tom Johnson (President, Celestron).  I still have it today.

 

Sent a copy of the report to DavidG and Ron Midiri...David looked closely at it, pointed out some exaggerations in the text, and factors shown by the photographs, and said that despite the report exaggerations, its optics were still around 1/8 wave...which bore out the superb views it has given me for almost 44 years!

 

attachicon.gif C8 v1.jpg

 

attachicon.gif vinemoon (3).jpg

 

attachicon.gif vinemoon (5).jpg

 

(Moon pictures were taken Saturday 7 August, at prime focus, with a Galaxy S8 phone).  

Post the report please. I'd like to see what it looks like.


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#20 Bonco2

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Posted 17 September 2019 - 03:28 PM

Not all of the early sandcast C8's were good. Mine purchased around 1973 was a dog. don't know why. Collimation was spot on.
Bill
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#21 CHASLX200

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Posted 17 September 2019 - 05:52 PM

I've had and tested dozens of Celestrons and I found no consistent anything between them. Everything varies, optics, mechanics, focus shift etc. Buy, test, repeat. 

You got that right.  I think that is why i bought so many as it was a crap shoot if i would get a mush dog or a winner.


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#22 CHASLX200

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Posted 17 September 2019 - 05:53 PM

Mine is from second quarter 1976, right at the point that Celestron shifted from sand cast to die cast mounts.  One of the options that Celestron offered at that point was an optical test report on the scope, using an interferometer, autocollimation (the "3 bars on the Ronchi screen"), the diffraction disk both inside and outside the point of focus, photographs of the tests, and test explanations/analyses for each test, specific to my C8 (ser # 256666)...signed by Tom Johnson (President, Celestron).  I still have it today.

 

Sent a copy of the report to DavidG and Ron Midiri...David looked closely at it, pointed out some exaggerations in the text, and factors shown by the photographs, and said that despite the report exaggerations, its optics were still around 1/8 wave...which bore out the superb views it has given me for almost 44 years!

 

attachicon.gif C8 v1.jpg

 

attachicon.gif vinemoon (3).jpg

 

attachicon.gif vinemoon (5).jpg

 

(Moon pictures were taken Saturday 7 August, at prime focus, with a Galaxy S8 phone).  

That looks good.  My seeing would tell the story if i had a 9+ nite.



#23 John Higbee

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Posted 20 September 2019 - 12:36 AM

Post the report please. I'd like to see what it looks like.

PM sent.



#24 bremms

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Posted 20 September 2019 - 08:06 AM

You got that right.  I think that is why i bought so many as it was a crap shoot if i would get a mush dog or a winner.

Yes.... There are a lot of MUSH DAWGS out there.



#25 bob midiri

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Posted 24 September 2019 - 02:09 PM

Well tonight is clear, but actually should have some real definitive info from being inside and bench testing tonight!! 




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