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Fixed a major source of shakes in my C4-R

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#1 RAK on Tour

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Posted 02 September 2019 - 05:57 PM

So way back when, (2007), Celestron was discounting the C4-R with black CG-4 mount to make way for the XLT 102. I purchased one for $249 shipped. Like many, I found the scope/mount combination prone to vibration, especially when focusing or even in a slight breeze. Having had a 120 F/8.3 Skywatchers on a CG-5 mount with the same aluminum legs, I chalked the vibrations up to the legs on the CG-4 mount and long moment arm of the

OTA. But I was unwilling to substitute the aluminum legs with either wood or steel due to the extra weight. 

 

Last week, while setting the scope back in its storage location, I took hold of the OTA at the lens end and noticed that there was movement NOT at the legs, but at the base of the mount where the adjustment for latitude is made! I knew immediately that I needed a shim to remove the play at that location. 

 

After removing the OTA, counterweight and shaft, I removed the mount from the latitude adjustment base. I found four thin, clear plastic "washers," two on each side. I needed something thin to take up the slight gap that remained. Fortunately, there was a thin piece of aluminum scrap on the floor, thin enough to be cut with an ordinary pair of scissors. I drilled a hole in a piece cut to match the plastic washers and inserted it between the two washers on one side of the mount. It was a BEAR getting everything aligned to get the bolt back through the hole to rebuild the mount, but I finally got the bolt to go, and got the whole scope and mount back together.

 

The result? NO source of wiggles from the newly-shimmed mount. Focusing is MUCH easier, with most of the vibration eliminated. And to think I went 12 years thinking it was the aluminum legs! Yes, replacing those legs would help even more, but had I replaced those legs first, I might not have noticed the real source of the greatest amount of vibration, and would still be frustrated with that vibration.

 

Roger


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#2 punk35

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Posted 02 September 2019 - 07:10 PM

I bought the same thing. The C4R is a great scope. It was my main scope until last year when I got the AT102ED.

 I regret selling the cg4 and the C4R. I wish I still had them both   



#3 treadmarks

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Posted 03 September 2019 - 09:02 AM

How is the view of Jupiter in this scope? I have the F/6.5 version, its only major downfall is that it muddies the disk of Jupiter with CA. If the F/10 could present the disc relatively cleanly, I could be tempted to make a frivolous purchase...



#4 RAK on Tour

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Posted 03 September 2019 - 09:13 AM

How is the view of Jupiter in this scope? I have the F/6.5 version, its only major downfall is that it muddies the disk of Jupiter with CA. If the F/10 could present the disc relatively cleanly, I could be tempted to make a frivolous purchase...

The view is pretty clean. Minimal CA. But I've never looked through an APO, so I can't really say how "clean" the image is. Perhaps an APO would show me what a clean image really is.

 

Roger


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#5 treadmarks

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Posted 03 September 2019 - 12:17 PM

The view is pretty clean. Minimal CA. But I've never looked through an APO, so I can't really say how "clean" the image is. Perhaps an APO would show me what a clean image really is.

 

Roger

Well you've got a few Newtonians, those all show color-correct images. How does it compare to them? Especially at higher powers >150X



#6 RAK on Tour

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Posted 03 September 2019 - 02:20 PM

Well you've got a few Newtonians, those all show color-correct images. How does it compare to them? Especially at higher powers >150X

Good point! The image is pretty much comparable to my Newtonians as far as color correction. I have two 114mm F/8 Newtonians where the images are surprisingly close at lower power. When I start getting into the 150x range, my skies start to limit the view. But I do see SOME CA on the C4-R, but not much. Keep in mind I have 70-year-old eyes, and age is supposed to diminish the effects of CA.  

 

Roger


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#7 treadmarks

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Posted 03 September 2019 - 03:13 PM

Thanks. I can tolerate violet halos but when Jupiter goes from a white planet to a purple one, that I cannot accept. Sounds like the 102mm F/10 might be the scope for me.



#8 RAK on Tour

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Posted 03 September 2019 - 03:47 PM

Thanks. I can tolerate violet halos but when Jupiter goes from a white planet to a purple one, that I cannot accept. Sounds like the 102mm F/10 might be the scope for me.

Through the C4-R, Jupiter is definitely not purple! I enjoy what image it puts up.

 

Roger



#9 RAK on Tour

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Posted 07 September 2019 - 09:48 AM

Last night I had another opportunity to observe with my "fixed" CG-4 and the C4-R optical tube. In the past, any breeze would cause the scope to vibrate and wiggle, making the image in the scope dance annoyingly. Last night there was a light breeze, and while viewing I suddenly realized I was not getting any vibration from the breeze! No - it wasn't blowing hard, but even a light breeze in the past was problematical. Now, the shakes were gone.

 

In the past, when a breeze came up and the image started moving around, I would think, "Darn that aluminum tripod!" Now I realize that it was never the source of the problem, and it only took a thin aluminum shim to fix.

 

Roger


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#10 texcoco

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Posted 01 December 2019 - 02:23 AM

Roger, I just secured a C4-R and have been looking for relevant information for the new acquisition...thank you for sharing!

 

Any other tips for a new C4-R custodian?



#11 RAK on Tour

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Posted 01 December 2019 - 07:36 PM

Roger, I just secured a C4-R and have been looking for relevant information for the new acquisition...thank you for sharing!

 

Any other tips for a new C4-R custodian?

texcoco,

 

There's a TON of info in this old, archived thread: https://www.cloudyni...nced-refractor/. It's 28 pages and 677 entries long.

 

I don't know what came with your acquisition, but if it's basically stock, I'd suggest a 50mm RACI finder to replace the stock straight-through 6x30. I'd also suggest a single-axis drive for the right ascension axis. I don't feel a drive for the declination axis is necessary. That also seemed to be the consensus in the thread linked above. Another article I found of great value was this one: https://www.cloudyni...he-c102-hd-r409. It's about the model that preceded the C4-R, The only difference between the C102 and the C4-R seems to be the C4-R has a collimateable lens cell. Especially helpful in the article is info on improving the focuser.

 

These changes will make your experience with your scope more enjoyable. You've got yourself a great scope!

 

Roger


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#12 grif 678

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Posted 01 December 2019 - 09:10 PM

The older C102's, made in Japan by Vixen, are so much better, almost like a fluorite. If you can find one of these ( they do come occasionally ) I would try to get it.



#13 clearwaterdave

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Posted 02 December 2019 - 06:53 AM

Hi Roger.,you gotta love it when something simple works.,I make very simple no frills pipemounts and once in a while I get an idea or like you I just happen to notice something.,and waalaa.,NOW it works all good.,thanks for the links.,cheers.,

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#14 RAK on Tour

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Posted 02 December 2019 - 12:28 PM

Hi Roger.,you gotta love it when something simple works.,I make very simple no frills pipemounts and once in a while I get an idea or like you I just happen to notice something.,and waalaa.,NOW it works all good.,thanks for the links.,cheers.,

clearwaterdave,

 

I've read many of your posts and enjoy the photos of your crutch pods and pipe mounts. Some clever engineering there! 

 

Roger


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