C14 without corrector

[davidc135]

13 hours ago, symmetal said:

Celestron charged me £250 just for a new corrector plate for my RASA 11 after I accidently dropped it putting it on the mount. Luckily the corrector was the only part of the RASA itself that was damaged. They wouldn't let me change the corrector myself but insisted I sent it to Orion Optics to be repaired and aligned. (They sent the new corrector plate directly to OO). This is probably because the scope was still under guarantee and if I did it myself the guarantee would be void. OO did a good job and the scope is now as good as new. 😉 This repair  wasn't covered by the guarantee though.

I doubt whether correctors are matched to mirrors on mass produced scopes though. 🤔 Didn't affect the results with my replacement corrector.

Alan

That was a good price and outcome.

At f10 or so compared to the f2.2 of the RASA, sct correctors/mirror sets need to be made to more exacting standards, so Celestron only offer to replace the entire optics set, AFAIK.

But, like you, I wonder how much difference it would make to visual instruments if only the corrector was replaced.

David

[dweller25]

@Chrb1985

I would use the scope as is with the cracks blacked out initially and then contact Celestron if you are not happy with the views.

Just out of interest how did the mirror crack ?

[Chrb1985]

On 12/10/2024 at 10:49, davidc135 said:

That was a good price and outcome.

At f10 or so compared to the f2.2 of the RASA, sct correctors/mirror sets need to be made to more exacting standards, so Celestron only offer to replace the entire optics set, AFAIK.

But, like you, I wonder how much difference it would make to visual instruments if only the corrector was replaced.

David

This is really interesting. Because thee is a guy in Italy that makes correctors for c14. I sent him an inquiry, but he could not make time for any more jobs until next year. But anyway since he makes correctors, I guess it works? I think he has a good reputation? Toscana Optics the company is called.

Anyway, some day I might buy the Baader eyepiece and just try it, just for fun. I love making and trying out things.

But meanwhile I will take the advice and black out the cracks. Sounds really smart!

[Chrb1985]

On 11/10/2024 at 01:26, davidc135 said:

The SA of a C14 without its corrector would be of the order of 22 waves depending on the exact details of the mirrors. A lot worse than Hubble so you are wise to keep the corrector!

David

Okay. Thanks a million! But do you not think that the Baader eyepiece will correct anything?

[Chrb1985]

On 12/10/2024 at 11:58, dweller25 said:

@Chrb1985

I would use the scope as is with the cracks blacked out initially and then contact Celestron if you are not happy with the views.

Just out of interest how did the mirror crack ?

Hi! Hehe okay, since I'm a open book I'll share the embarrassing truth about the accident. I acctually rethreaded all the threads to metric threads and replaced alle the screws to M5. It worked really great. Except that the Celestron dewheater ring don't really fit my old C14. And so I guess it was a combination of good old "user error". At least we call it that in Norway. I can't say for sure actually what happened, but after retracing my steps, I guess that the dewheater ring went on with too much tension, and either I over tightened one screw or it "slipped" or something like that. Maby even something like a small metal fragment was trapped behind the ring.. I really don't know. But right now, Its on and it works. But I left one screw out..

This is so embarrassing, but I hope someone else can learn from my mistakes. These screws should NOT be overtightened at all and the ring should slip easy on, it should NOT be forced on like I did.. but in my head I was SURE that the ring would just press down on the cast iron and the gasket. 🤦 So this was a major blunder.. I acctually got this covered by my insurance. But since the Toscana Optics company could not help me it really did not help me at all 🤦

Please don't judge me

[dweller25]

1 hour ago, Chrb1985 said:

Hi! Hehe okay, since I'm a open book I'll share the embarrassing truth about the accident. I acctually rethreaded all the threads to metric threads and replaced alle the screws to M5. It worked really great. Except that the Celestron dewheater ring don't really fit my old C14. And so I guess it was a combination of good old "user error". At least we call it that in Norway. I can't say for sure actually what happened, but after retracing my steps, I guess that the dewheater ring went on with too much tension, and either I over tightened one screw or it "slipped" or something like that. Maby even something like a small metal fragment was trapped behind the ring.. I really don't know. But right now, Its on and it works. But I left one screw out..

This is so embarrassing, but I hope someone else can learn from my mistakes. These screws should NOT be overtightened at all and the ring should slip easy on, it should NOT be forced on like I did.. but in my head I was SURE that the ring would just press down on the cast iron and the gasket. 🤦 So this was a major blunder.. I acctually got this covered by my insurance. But since the Toscana Optics company could not help me it really did not help me at all 🤦

Please don't judge me

Good feedback warning people to not over tighten the corrector screws 👍

[Gonariu]

Here in Italy there is also Adriano Lolli who is quite well known among Italian amateur astronomers.

[davidc135]

21 hours ago, Chrb1985 said:

Okay. Thanks a million! But do you not think that the Baader eyepiece will correct anything?

The Baader eyepiece won't correct anything in this situation. Cheaper and simpler eyepieces may themselves cause spherical aberration when used with faster telescopes, even if the scope itself is well corrected. The longer the focal length of the ep, the worse the effect. Better ones should be corrected for this shortcoming.

However, slow systems like most scts are free of this anyway.

David

[Chrb1985]

On 14/10/2024 at 11:11, davidc135 said:

The Baader eyepiece won't correct anything in this situation. Cheaper and simpler eyepieces may themselves cause spherical aberration when used with faster telescopes, even if the scope itself is well corrected. The longer the focal length of the ep, the worse the effect. Better ones should be corrected for this shortcoming.

However, slow systems like most scts are free of this anyway.

David

Can't really say I understood what you ment here??

[Chrb1985]

On 13/10/2024 at 16:29, Gonariu said:

Here in Italy there is also Adriano Lolli who is quite well known among Italian amateur astronomers.

So do you know what he charges for a c14 corrector?

[dweller25]

3 hours ago, Chrb1985 said:

So do you know what he charges for a c14 corrector?

Here is his website….

https://www.adrianololli.com

[Gonariu]

6 hours ago, Chrb1985 said:

So do you know what he charges for a c14 corrector?

No, I heard Lolli is very good. If you don't find anyone in Norway, try to contact him at least by email, I don't think they have problems with English.

[davidc135]

On 16/10/2024 at 11:19, Chrb1985 said:

Can't really say I understood what you ment here??

I'll try to explain it better. All eyepieces are sold with the intention of being used with telescopes that are properly corrected for spherical aberration.

However, traditional designs of eyepieces such as Huyghenian, Ramsden, Kellner and Plossl in roughly ascending order of capability will themselves cause aberrations, both at centre of field and off axis. These problems increase exponentially with the speed of the telescope. At f10 or so, scts (with their correctors) are so slow as to be useable with any kind of eyepiece.

But with Faster Newtonians working at sometimes less than f4, modern sophisticated designs are needed for sharp images over a wider angle as well as at the centre of field, especially when low powers are used.

I think Baader are just saying that their product is doing a good job, not that it will correct the deficiencies of any telescope, let alone the insurmountable aberration of a sct without its corrector.

David