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C14 with good optics?

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#201 CHASLX200

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Posted 21 September 2016 - 07:12 PM

It's in Cail and pickup only so that is out unless you wanna go pick it up and buy it back from me if i turn my nose up at it if it can't do 850x.



#202 rolo

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Posted 21 September 2016 - 07:23 PM

So, buy the optics then buy the cheapest OTA and your 1/10000 is a reality. BTW, I would buy it but my C14 tests the same way with a 250lpi Ronchi so I'm good. I still can't say my C14 is 1/10 wave from a Ronchi on a star though. I would need an interferometer for that kind of claim.

 

Ask the seller if he would take it back if it wasn't better than 1/10 wave.


Edited by rolo, 21 September 2016 - 07:24 PM.


#203 ATM57

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Posted 21 September 2016 - 07:37 PM

So, buy the optics then buy the cheapest OTA and your 1/10000 is a reality. BTW, I would buy it but my C14 tests the same way with a 250lpi Ronchi so I'm good. I still can't say my C14 is 1/10 wave from a Ronchi on a star though. I would need an interferometer for that kind of claim.

 

Ask the seller if he would take it back if it wasn't better than 1/10 wave.

Not trying to start a poop storm (been down that road) but concerning Ronchi testing, I will repeat this quote from Tom Johnson (Celestron founder) who was a master of optics and used interferometers. He stated: "If one is seeking to determine whether or not an F/10 telescope is diffraction limited, he would use a 150-line grating (lines per inch) with 3 to five shadow bands intercepting the converging cone of light. If all of the bands appear straight, the wavefront error is less than 1/10th wave."

 

I have used a 250lpi grating and the bands are straight from core to edge at two bands. The star test is very good. I have not had seeing good enough to do critical testing but the star test holds up very well even at 650x. So well in fact that I agree with the Ronchi test results as far as spherical aberration is concerned.

 

Scopejunkie


Edited by ATM57, 21 September 2016 - 07:38 PM.


#204 CHASLX200

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Posted 21 September 2016 - 07:52 PM

So, buy the optics then buy the cheapest OTA and your 1/10000 is a reality. BTW, I would buy it but my C14 tests the same way with a 250lpi Ronchi so I'm good. I still can't say my C14 is 1/10 wave from a Ronchi on a star though. I would need an interferometer for that kind of claim.

 

Ask the seller if he would take it back if it wasn't better than 1/10 wave.

I'm not going thru all that trouble.  I am not looking for a C14 anymore.



#205 rolo

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Posted 21 September 2016 - 08:01 PM

 

So, buy the optics then buy the cheapest OTA and your 1/10000 is a reality. BTW, I would buy it but my C14 tests the same way with a 250lpi Ronchi so I'm good. I still can't say my C14 is 1/10 wave from a Ronchi on a star though. I would need an interferometer for that kind of claim.

 

Ask the seller if he would take it back if it wasn't better than 1/10 wave.

Not trying to start a poop storm

 

Scopejunkie

 

Me neither. You can claim whatever you like. But, if you give me a money back guarantee if it doesn't test at 1/10 wave or better after I have it professionally tested. I'll buy the optics.



#206 ATM57

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Posted 21 September 2016 - 08:13 PM

 

 

So, buy the optics then buy the cheapest OTA and your 1/10000 is a reality. BTW, I would buy it but my C14 tests the same way with a 250lpi Ronchi so I'm good. I still can't say my C14 is 1/10 wave from a Ronchi on a star though. I would need an interferometer for that kind of claim.

 

Ask the seller if he would take it back if it wasn't better than 1/10 wave.

Not trying to start a poop storm

 

Scopejunkie

 

Me neither. You can claim whatever you like. But, if you give me a money back guarantee if it doesn't test at 1/10 wave or better after I have it professionally tested. I'll buy the optics.

 

I would give you a money back guarantee on the optics even if they were not professionally tested. Check my Amart ratings. I have always done this on ALL my astronomy transactions but, I had no plans of just selling the optics.

 

Scopejunkie



#207 rolo

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Posted 21 September 2016 - 09:32 PM

After consulting with a couple telescope opticians, I'll keep my C14 as is. Good luck with your sale....



#208 CHASLX200

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Posted 22 September 2016 - 05:12 AM

After consulting with a couple telescope opticians, I'll keep my C14 as is. Good luck with your sale....

My rings for a C14 are almost done. But i can't see paying for a C14 then buying another to use the optics from the first C14 to put in the 2nd C14.  Just as well buy new at what it would cost me. I am gonna wait until next April then jump on a C14 once jupiter is out.



#209 TG

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Posted 22 September 2016 - 01:11 PM

A simple way to check if Tom Johnson's assertion of using Ranchi for 1/10 wave holds merit is to increase back focus a couple of inches and then see if you can see the change in spherical aberration in the bands. I do have a 250lpi grating but diffraction effects make it hard to determine whether mild spherical aberration is present.

Tanveer

#210 Patrick

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Posted 22 September 2016 - 04:23 PM

 

Good luck with that approach.  Let's see...no specs and no way of actually measuring anything--just a statement that you want a 1:10,000 scope, you want a guarantee that it will make you happy, and that you are really picky..  I don't care how much you are willing to pay, I personally wouldn't waste my time with anyone who came to me with that proposal.  I hate to sound harsh but you come across as the kind of 1 in 10,000 customers that the folks at Celestron hate dealing with.

 

John

Too bad i guess for you. I am picky and have the best seeing in the country and i expect the best optics in a OTA that i buy.  I have owned one C8 that was a dead sharp and i know there is a lucky C14 out there.

 

Tampa has the best seeing conditions in the country?  A quick Wiki search shows quite a few of the large observatories are located in the western US on tops of large mountains.  I could be wrong, but I think those areas may have better seeing conditions than Florida.  I'm not saying that Florida doesn't have good seeing...just saying maybe not the 'best'.  If you don't care anything about light pollution and can live on the coast, then ok, at least Florida doesn't have to worry too much about the jet stream. 

 

Patrick



#211 CHASLX200

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Posted 22 September 2016 - 05:41 PM

 

 

Good luck with that approach.  Let's see...no specs and no way of actually measuring anything--just a statement that you want a 1:10,000 scope, you want a guarantee that it will make you happy, and that you are really picky..  I don't care how much you are willing to pay, I personally wouldn't waste my time with anyone who came to me with that proposal.  I hate to sound harsh but you come across as the kind of 1 in 10,000 customers that the folks at Celestron hate dealing with.

 

John

Too bad i guess for you. I am picky and have the best seeing in the country and i expect the best optics in a OTA that i buy.  I have owned one C8 that was a dead sharp and i know there is a lucky C14 out there.

 

Tampa has the best seeing conditions in the country?  A quick Wiki search shows quite a few of the large observatories are located in the western US on tops of large mountains.  I could be wrong, but I think those areas may have better seeing conditions than Florida.  I'm not saying that Florida doesn't have good seeing...just saying maybe not the 'best'.  If you don't care anything about light pollution and can live on the coast, then ok, at least Florida doesn't have to worry too much about the jet stream. 

 

Patrick

 

I'm not in Tampa . But lived there for 41 years and our seeing is about the best. I am talking steady seeing, not dark skies. Now i am 25 miles northwest of Tampa on the gulf and have less good seeing nites than i did living on the Bay.




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