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New Celestron C6 SCT, still has diamond ring shinny light baffle issue

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#1 aa6ww

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Posted 17 August 2019 - 02:56 PM

I just picked up a new C6 SCT from a CN's member at a great price who didn't wanna deal with the diamond ring effect on bright objects he had on the first night he set up his scope. 

I'm surprised that over the years, Celestron continues to have this issue unresolved.

Regardless, I got a great deal on a new little lightweight C6 SCT I wanted as my larger Grab and Go scope for my CG-4 mount, since my C8 is too much weight for the CG-4. 

First night I checked the scope looking at Jupiter and sure enough, as I moved the planet into the field of view, I saw the huge ring move into the field of view. As the planet got centered, the ring disappeared. 

 

Instead of removing the corrector, I just removed the 4 screws that hold the entire front cell on the scope and everything just lifted off exposing the inside of the scope. 

I had some black sticky back felt from a local fabric store and cut half inch strips 3.5" long and lined the front of the light baffle with it, leaving about 3/4 of an inch out so i could fold it over the front of the baffle. This entire process took about 5 minutes. I was careful to make sure each strip was agasint the other so the inside of the baffle had a smooth ring of felt material inside the tube. 

 

Afterwards, I thought id flock the inside of the OTA since the scope was already opened and I had plenty of the sticky back felt left. I unscrewed the 4 screws holding the bottom of the tube to the lower cell and detached the body of the scope from the bottom cell. I cut 3 strips the full length of the tube and attached them in place. It was a quick process without having to worry about the primary mirror or light baffle in place.

 

After this, I put the scope back together. The tube had no wiggle installed all the screws so I was hoping it would maintain its collimation. 

From start to finish, this took about an hr.

 

I put the scope on my mount and looked again at Jupiter. The diamond ring effect was completely gone and the collimation was dead on. I could see the GRS on the surface of Jupiter, despite the mediocre seeing conditions. I did a high power star test on Vega and the culmination was spot on. 

 

Now I have a great little grab and go scope with 6" of aperture. Since I use my focal reducer on the scope, I have under 1000mm FL so i can go fairly wide using my 1.25" Explorer scientific eyepieces.

 

Too bad Celestron doesn't fix this problem. Many wont go through the trouble of fixing their C6's and just buy something different.

 

...Ralph in Sacramento.


Edited by aa6ww, 17 August 2019 - 06:40 PM.

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#2 Xeroid

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Posted 17 August 2019 - 03:42 PM

Nice work!

 

I thought I had read here on CN where the problem was due to a shiny baffle tube, at the opening closest to the corrector?



#3 petert913

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Posted 17 August 2019 - 03:58 PM

Yes, I slipped some rolled up flocking paper into my C6 baffle tube and that cured the diamond ring for me.


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#4 mclewis1

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Posted 17 August 2019 - 05:23 PM

My 2006 black tubed C6 has a factory flocked baffle tube (so Celestron has been aware for at least 15 years, and has tried to deal with it). I see no diamond ring effect but the flocking edges don't come together (small gap) and that leads to some slight diffraction artifacts in bright stars (so no big deal). If the inside of the baffle tube is a little reflective adding flocking at the top does indeed help but you need to be really careful as anything that narrows the baffle tube at the top (even a very small amount) gets into the light path.

 

Flocking the inside walls of the ota generally doesn't do much at all for modern SCTs (they tend to be quite well baffled).

 

Oh and it's collimation. wink.gif


Edited by mclewis1, 17 August 2019 - 05:26 PM.


#5 Auburn80

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Posted 17 August 2019 - 05:48 PM

My recent vintage C6 - circa 2016 - has that issue. I bought it new and there is no flocking in the baffle tube.

#6 aa6ww

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Posted 17 August 2019 - 06:37 PM

The fabric store I went to had various thicknesses of black felt with sticky back on them. Some was thick and fuzzy. I got the thinnest material I found which wasn't much thicker then the paper it was attached to. It worked well on the rim of the light baffle closest to the corrector. On the front rim of the light baffle, you can see the shinny ring where it just wasn't painted properly. 

 

Last time I had a C6 I did this also to it. First I tried repainting the rim of the light baffle with flat black paint but it didn't seem to get rid of the diamond ring effect completely but it helped. 

 

This time I just went straight for the flocking. As far as flocking the rest of the tube, the inside of the tube is painted a flat gray, not black. I just didnt seem right. Plus I noticed plenty of screw hole burrs where shinny aluminum shavings were sticking out from the screw threads just enough to be annoying.

The scope was opened so i just covered the entire inside of the scope with this same black felt. Whether it helps or not who knows, but i know now when I look down the tube from the corrector end, I can no longer see the walls of the scope with out putting a flashlight down it. For the few minutes it took to do this, it was well worth it since I don't like being inside these scopes for any reason.

 

Unlike other larger SCT's, the C6 is such a small OTA that it just has 4 screws holding the front cell in place and 4 holding the back cell in place so it literally takes 2 minutes to disassemble the scope completely.

 

The mirror is so small that I saw no Image shift at all, at just over 200x. The C6's I've looked at and owned in the past have all had very sharp optics. My last C6 I sold because I thought I wanted a larger SCT so I replaced it with a C8. 

 

Since Id say 90 percent of my observing is with my CG-4 and small refractors, (FC-60 and AT-92) I wanted a light weight OTA that the CG-4 can  handle effortlessly but I wanted as much aperture that the scope could handle. The C6 seems to be that scope. Now I can resolve most of the tiny globulars in the south without having to grab a larger scope and mount.   

 

...Ralph 


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#7 Astrojedi

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Posted 19 August 2019 - 08:46 AM

The C6 is a very nice portable size. I used it for a couple of my Astro trips. This issue with the C6 baffle has existed for a while but puzzling that seems to effect only some OTAs. A black XLT version I got couple of years ago did not have this issue but an orange SE version did. Maybe there is this one guy in the factory who does not believe in flocking. Jokes aside Celestron should address this.



#8 Auburn80

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Posted 19 August 2019 - 09:49 AM

The C6 is a very nice portable size. I used it for a couple of my Astro trips. This issue with the C6 baffle has existed for a while but puzzling that seems to effect only some OTAs. A black XLT version I got couple of years ago did not have this issue but an orange SE version did. Maybe there is this one guy in the factory who does not believe in flocking. Jokes aside Celestron should address this.


And mine is the black model. <shrug> Apparently, all the improvements in quality touted in other threads are still lacking. It is an excellent package that I'll fix and use as a lighter weight travel scope in moderate temps.

I had about talked myself into disassembling from the front so the OPs description is heartening. Great job!

#9 Astrojedi

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Posted 19 August 2019 - 10:06 AM

And mine is the black model. <shrug> Apparently, all the improvements in quality touted in other threads are still lacking. It is an excellent package that I'll fix and use as a lighter weight travel scope in moderate temps.

I had about talked myself into disassembling from the front so the OPs description is heartening. Great job!

 

This is a very C6 specific issue. I would not extrapolate or generalize using this.



#10 Auburn80

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Posted 19 August 2019 - 11:32 AM

This is a very C6 specific issue. I would not extrapolate or generalize using this.


I don't. I'm expecting delivery of a Mak 180 today so I'm still keeping an open mind.

One does have to ask the hard questions though. Why is this still an occasional problem even if limited to the C6?

#11 Astrojedi

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Posted 19 August 2019 - 12:09 PM

I don't. I'm expecting delivery of a Mak 180 today so I'm still keeping an open mind.

One does have to ask the hard questions though. Why is this still an occasional problem even if limited to the C6?

Very likely cost. C6 is one of the lowest priced SCTs in the line up (priced even lower than a C5 on a standalone basis). The larger SCTs are more popular and more profitable. So if I was running the business it would make sense for me to focus my limited QA dollars there - especially the flagship EdgeHDs as they are the premium scopes in the line up and likely the most profitable.


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#12 aa6ww

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Posted 19 August 2019 - 12:43 PM

Last night I had the little C6SCT out since the moon didn't come up till 10pm. Even in my back yard mediocre skies, I was still able to make out every Messier object I looked for and a few NCG open clusters.
There is quite a selection of globular clusters around Sagittarius and Scorpio. M4, M80, M19,M62, NGC 6388, NGC 6441, M54, M70,M69,M28,M25,M18, M17, M16 all were right there in the South between Jupiter and Saturn and fun easy targets last night.

Its a great little grab and go for being so light with 6" of aperture, with crisp optics. Its not my APM-152ED with about the same aperture, but it also doesn't take me an hour to set up and another hour to tear down also, and regarding the objects I saw last night, it definitely got the job done without stressing my back also.

I use my focal reducer to reduce the Focal length down to less then 1000mm FL. It works great for giving me a wide enough field of view so objects are easy to find.

Pretty fun, and very light weight and a great set up for just being out side for a few hrs.

...Ralph

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  • C6SCT on CG4.jpg

Edited by aa6ww, 20 August 2019 - 12:50 AM.

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#13 azure1961p

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Posted 19 August 2019 - 01:17 PM

Glad it worked out. A little flocking and it's a nice performer.  I did the inside of the primary baffle, secondary baffle and tube.  Same with my C90 which had equally ruinous glare due to little or no real flocking.  Now it's a contrasty scope even in daytime spotting.

 

Pete



#14 aa6ww

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Posted 19 August 2019 - 02:01 PM

I've had an orange tube C6 that did not have this issue, it was from a single arm GoTo complete package. Two black tube ones I have had now, both had this issue.

So I see no consistency.

...Ralph


The C6 is a very nice portable size. I used it for a couple of my Astro trips. This issue with the C6 baffle has existed for a while but puzzling that seems to effect only some OTAs. A black XLT version I got couple of years ago did not have this issue but an orange SE version did. Maybe there is this one guy in the factory who does not believe in flocking. Jokes aside Celestron should address this.



#15 Astrojedi

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Posted 19 August 2019 - 07:26 PM

I've had an orange tube C6 that did not have this issue, it was from a single arm GoTo complete package. Two black tube ones I have had now, both had this issue.

So I see no consistency.

...Ralph

 

I agree... I did not mean to imply that the black OTAs are somehow better QA than the orange OTAs. I think besides the color they receive the same QA (or not!)



#16 aa6ww

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Posted 19 August 2019 - 09:18 PM

I was trying to think that maybe the C6SE packages had a higher level of quality control, thinking that maybe the Orange tube models that had the side mounted dovetails had the better light baffles. It doesn't seem to be the case however from hearing others who have had both models with baffle issues.

 

Fortunately, the entire front of the scope can just lift off by removing 4 screws, (and the dovetail) to resolve the problem. In my case, putting it back on after the simple fix caused no collimation issues.

 

...Ralph




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