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NexStar 6" planets are not clear?

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#1 Pitu

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Posted 03 December 2022 - 09:18 PM

Hi.

I got Celestron NexStar 6" tube from my friend to test it and first night out I see my planets are not clear as my Meade LX200 AGF 8".

However when I tray same 6" on the stars or clusters as Pleadis, stars look ok and sharp. I didn't have chance to check the Moon it was moonless nights. 

My guess will be the collimation but look like the mirrors are in line.

It is something I don't know about orange tube or I have doble check the collimation?

Cheers

Pitu



#2 Asbytec

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Posted 03 December 2022 - 09:22 PM

The usual suspects for bad images are thermal stability, collimation, and seeing conditions. That is presuming the scope is in focus and the optics are descent (which they very likely are). So, check the first three conditions. 



#3 Pitu

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Posted 04 December 2022 - 08:44 AM

Thank you.
I have to take out agan and Chek.
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#4 Eddgie

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Posted 04 December 2022 - 11:11 AM

"not clear as" Is somewhat subjective. The difference in aperture does not seem like that much, but it is actually enough to make a meaningful difference combined with the fact that the C6 also has a larger secondary obstruction (by percentage of diameter). 

 

Also, the tendency among testers is to compare the view at the same power. I don't know if you did this, but if you did, and you used a power of maybe 200x, this would greatly favor the larger scope because the bigger exit pupil will let the eye work better due to the added image brightness.  For this comparison, using the same power in the smaller scope puts it at a disadvantage if the power is in the 1x per mm of aperture category. 200x In the 8" might still look good but in the 6", it might just be too much.  

 

As others mentioned, it could be thermal, but seeing would have favored the smaller scope so that should be ruled out if they were compared side by side.

 

Collimation could be an issue as well, but no offense intended here, if you are going to compare two SCTs, it would be important to check things like that before starting. 


Edited by Eddgie, 04 December 2022 - 11:12 AM.

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#5 Pitu

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Posted 05 December 2022 - 10:13 PM

I try last night again on 3 targets. Moon, planets and Stars.

Moon can be seen clear view up to 20mm eyepiece.  More power and can't focus clear, moon is not clear. Not bad but not crispy clear.

Planet same thing, on Jupiter try to focus on the moons, can't focus them as a small dot.

Stars same thing. Less power is okay not perfect but more power and the stars are as egg somehow.

Collimation looks ok. 

The OTA is both used, Can be previse owner to take out corrector plate and not put back as spouts to go?  



#6 Asbytec

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Posted 06 December 2022 - 10:18 AM

Did you get any clear moments on the moon where detail popped just for a second or two? If so, seeing is probably the cause. If they were blurry all the time, then probably either collimation or thermal issues. Thermal issues tend to calm down with time, and the other good news is you can control collimation accuracy.

Edited by Asbytec, 06 December 2022 - 10:19 AM.


#7 12BH7

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Posted 06 December 2022 - 11:05 AM

 Do you have a 27mm EP that came with the scope? Use the lowest power EP you have and retest.

 

If you look a the craters on the moon  and they are in any way "soft" then you're clearly out of collimation. They should be RAZOR sharp.



#8 Pitu

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Posted 06 December 2022 - 07:48 PM

Hi Asbytec.

So I setup telescope outside. Normal from home out and you are right have no time to cool down because it was short window for clouds to move in. 

Yes i have clear view on the moon whit 24mm but not with 13 and 8mm . All eyepieces are Baader Hyperion. Goin back on 24 again clear moon.

I have to find some one around me to check collimation I don't have experience whit this tubes I'm dob guy.

 Secund I'm going to leave the tube in to de observatory and take it out to be same temperature as outside.  

And last I'm going to keep the hammer next to me if nothing work hammer will do the job  lol

sheers.

Did you get any clear moments on the moon where detail popped just for a second or two? If so, seeing is probably the cause. If they were blurry all the time, then probably either collimation or thermal issues. Thermal issues tend to calm down with time, and the other good news is you can control collimation accuracy.



#9 Pitu

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Posted 06 December 2022 - 07:56 PM

Hi 12BH7.

i don't have 27mm but i have 24mm Baader. Hope next time I'm going to have more time clear sky to test  collimation. 

Just question, if previous owner have take corrector plate out and assembled beck wrong what happen to the OTA? Image is blurry or something ells?

Thanks.

 

 Do you have a 27mm EP that came with the scope? Use the lowest power EP you have and retest.

 

If you look a the craters on the moon  and they are in any way "soft" then you're clearly out of collimation. They should be RAZOR sharp.



#10 Asbytec

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Posted 07 December 2022 - 07:55 AM

 

Yes i have clear view on the moon whit 24mm but not with 13 and 8mm .

 

 

Don't apply the hammer technique just yet. :)

 

Yea, as expected, lower magnification can appear more crisp (or crisper depending on grammar check). At higher magnification you begin to see the blur. What I meant was, at higher magnifications did you get a clear "snapshot" or two? If so, that was probably seeing calming down for a moment allowing a cleaner (or more clean) view.  If so, then seeing is the likely cause. If not, then something else like thermal equilibrium or miscollimation is the most likely cause. . 


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#11 Bill Barlow

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Posted 07 December 2022 - 11:59 AM

I also own a C6 and have it collimated very well.  It puts up very sharp images of the moon, planets and stars and still looks sharp most nights at magnifications above 200X.  Since your scope puts mushy views at magnifications above 100X, your optics might have issues.  These scopes vary in optical quality from sample to sample so yours might be not diffraction limited.  

 

Bill



#12 ictus

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Posted 13 December 2022 - 06:38 PM

Hello

             I own  127 mac took it outside from a warm house and the views were also not clear

             I,am also a dob guy I have a 10''and its cools faster then the mac.I did not have the mac out

             long since it was clouding up,How long does a mac take to cool down?and how hard is to collimate?

                                                                                                      

                                                                                                                                                  Thanks Anthony



#13 Pitu

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Posted 13 December 2022 - 09:08 PM

Hi Anthony.

I can't tell you how long take to Mac to cool down because I'm also Dob guy. 

On my last test whit my SCT I left OTA in the observatory for from day before and view was no much different from before . I play little bit whit collimation and got better view on the planets and stars.

Take time to learn to collimate properly but whit have patience and it will get positive results on the and.

Wach some videos on youtube 

Good luck.

Pitu.

P.S. I still work on my, nothing done for now.

Hello

             I own  127 mac took it outside from a warm house and the views were also not clear

             I,am also a dob guy I have a 10''and its cools faster then the mac.I did not have the mac out

             long since it was clouding up,How long does a mac take to cool down?and how hard is to collimate?

                                                                                                      

                                                                                                                                                  Thanks Anthony




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