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New AT 6" and 8" Classical Cassegrain

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#1376 pweiler

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Posted 16 September 2021 - 11:34 AM

I know this is a long thread. probably read 1/2 of it all.

 

Just received my Orion CC8.   I am setting this up for planetary Photography with a ASI462Mc camera.

I was finally able to achieve focus using all three extensions (4") and racking the focuser out to 45mm of the 50mm  travel.  The was NO barlow or diagonal used.

 

This just does not seem right to me,  I took a not so good picture of my secondary.

 

 

Will measure later today but I would say the gap is closer to 5mm where you can see the threads.

I am not sure exactly what screws to loosen so I can screw in the lock ring to bring my focus in with out so many spacers.

Brand new scope from Orion, have actually thought about just sending it back.

 

If I read and understand all this correctly my mirrors may be too close to each other.

If this CC8 photo helps…I have collimated the scope, but never changed the secondary spacing. This is what it’s been since shipped from Orion. If you zoom in you can count the screw threads.

 

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#1377 BobW55

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Posted 16 September 2021 - 01:55 PM

Hi Bob,

I think the 6 and 8 CC are quite similar..At the 6 CC you can just loosen the fixing ring of secondary baffle size and screw the whole baffle on its circumference towards the end.

On the other hand, why should they sell the device with an unappropriate mirror distance? And it's strange you need all extensions. A 2 inch dagonal makes a big difference, guess you'll avoid 3 extensions. What are you focusing at? true star or sth nearby? When you're ready, I'd like to know the mirror distance....I refer to No. 1361.. all those data, if you like

EDIT: 

Measured 4.5mm

 

Thanks I will let you know actual distance later on.

Was focusing on actual stars.   I now understand why I could never get good focus on some trees 1/2 mile away..

Because I am an imager and would like to save the weight of all the extension tubes, may try to move the 2nd mirror enough to do that.


Edited by BobW55, 16 September 2021 - 02:11 PM.


#1378 BobW55

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Posted 16 September 2021 - 02:37 PM

So if I am understanding this.  I can loosen the large center screw, 

tighten the large outer ring (increase the distance between the mirrors).

 

Could I use the old point the scope towards a bright window and use a tissue as a screen at the back side and move it in/out till the image shows up 

to get myself into a rough focus point?

 

Andi have no clue why someone would sell a scope so far out.  I call it the luck of Bob.



#1379 quilty

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Posted 16 September 2021 - 03:22 PM

Look at No. 1337, that's from the 6 inch size. Locking ring and baffle, not the central screw. any mm more mirror distance yields about 15 mm less backfocus.

I still think you could use a diagonal. As the former discussion says, a major distance shift might take the scope out of optimum spherical correction



#1380 BobW55

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Posted 16 September 2021 - 04:03 PM

Look at No. 1337, that's from the 6 inch size. Locking ring and baffle, not the central screw. any mm more mirror distance yields about 15 mm less backfocus.

I still think you could use a diagonal. As the former discussion says, a major distance shift might take the scope out of optimum spherical correction

There lies my problem is how much correction.

Secondary2C
Secondary2B

 

I see the three culmination screws, just not sure what the center screw and locking ring does.  The locking ring is tight.

Is it the locking ring by its self that adjust the distance?


Edited by BobW55, 16 September 2021 - 04:05 PM.


#1381 quilty

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Posted 16 September 2021 - 04:13 PM

Hi Bob,

It's collimation screw. Again I think, the mirror distance is right in terms of spherical correction. But to increase the distance you can turn the locking ring counter clockwise to the bottom, and then follow with the secondary baffle. 4.5 mm more distance might yield 3 inch less backfocus. No need to touch the big central screw. Keep the actual gap width in mind, when you'll find poor imaging due to poor correction ou can easily go back to the former position



#1382 BobW55

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Posted 16 September 2021 - 04:28 PM

Hi Bob,

It's collimation screw. Again I think, the mirror distance is right in terms of spherical correction. But to increase the distance you can turn the locking ring counter clockwise to the bottom, and then follow with the secondary baffle. 4.5 mm more distance might yield 3 inch less backfocus. No need to touch the big central screw. Keep the actual gap width in mind, when you'll find poor imaging due to poor correction ou can easily go back to the former position

Ahh ok... now I understand.   was afraid to force the knurled ring around the mirror.

I may just send the whole thing back

 

241480848 1466012810438653 1982587188992624820 N

 

I use ASIAIR to image with.  This is a screen grab.  The elongation is due to the DEC being out of balance from all the extensions



#1383 BobW55

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Posted 16 September 2021 - 06:23 PM

Ok  figured out how the secondary moves.  

Kept going in 0.5mm steps (Reducing the gap, started at 4.5mm)  

 With a single 1" spacer, and the focuser racked to 50mm  I can almost focus a distant tree.

This is a vast improvement from where I was, and I have remove 3" of extensions.

Am going to stop here till it gets dark and make sure I can rack the focuser in enough to focus a star.

 

Thanks for all the help so far.

I shoot a ton of DSO's so I know what a bad star looks like.  If I still have issues tonight Orion will be getting the scope back.  Should not have to do all this to a new scope IMHO.



#1384 Russkiy

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Posted 17 September 2021 - 02:48 AM

Please let us know if the image quality is good after you have increased the distance between the mirrors. And if you return the telescope to the seller, what will you replace it with? It is compact, judging by the reviews - high image quality, open design, which gives fast thermal stabilization. And I also believe that nothing prevents you from using a diagonal mirror. It is unlikely that this will greatly worsen the picture.


Edited by Russkiy, 17 September 2021 - 02:49 AM.


#1385 quilty

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Posted 17 September 2021 - 05:12 AM

Hi Bob,

before sending back the scope, please perform the most easy torchtest as described above in No. 1361. Can't wait for some reliable data for central obstruction and true aperture of the CC8, guess as many of us. 



#1386 BobW55

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Posted 17 September 2021 - 08:13 AM

Please let us know if the image quality is good after you have increased the distance between the mirrors. And if you return the telescope to the seller, what will you replace it with? It is compact, judging by the reviews - high image quality, open design, which gives fast thermal stabilization. And I also believe that nothing prevents you from using a diagonal mirror. It is unlikely that this will greatly worsen the picture.

 

 

Hi Bob,

before sending back the scope, please perform the most easy torch test as described above in No. 1361. Can't wait for some reliable data for central obstruction and true aperture of the CC8, guess as many of us. 

Got clouded out last night..  

Going to switch over to my 294MC pro camera, the smaller pixel size will do better.   I did notice I knocked the culmination off some, no surprise there.

I will attempt a torch test later on. and document the results.

I really don't want to send the scope back, It would be costly.  Just **** me off that people don't make quality instruments.  

This scope just ticks many boxes for planetary imaging.

Thanks for all the help so far.



#1387 quilty

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Posted 17 September 2021 - 11:47 AM

Hi Bob,

I still think there's nothing wrong with your scope except it might not be a full 8 inch size scope and many observers are pleased with it, nevertheless



#1388 pweiler

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Posted 17 September 2021 - 12:09 PM

Hi Bob,
I still think there's nothing wrong with your scope except it might not be a full 8 inch size scope and many observers are pleased with it, nevertheless


I haven’t been following this entire thread, but the specs for my Orion CC8 have listed from day 1, D=200mm, which is 7.874 inches.

#1389 quilty

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Posted 17 September 2021 - 03:21 PM

If it was that easy, just reading the specs and believe in advertising stuff



#1390 BobW55

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Posted 17 September 2021 - 03:32 PM

Hi Bob,

I still think there's nothing wrong with your scope except it might not be a full 8 inch size scope and many observers are pleased with it, nevertheless

Not worried about the size,  just  very disappointed that it would not focus with out some user intervention.   FL2400mm and F12 will be great for planetary Photography.

Teams up nice with my Redcat51 and AT130 EDT..



#1391 pweiler

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Posted 17 September 2021 - 03:42 PM

If it was that easy, just reading the specs and believe in advertising stuff


If you’re not happy, sue them for false advertising. Make it a class action.

Edited by pweiler, 17 September 2021 - 03:42 PM.

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#1392 quilty

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Posted 17 September 2021 - 05:43 PM

Sure I'm not happy because they're cheating. But first of all I'd like to know the true data, simple as that, waiting for Bob or anyone else owning a CC8 to provide them. 



#1393 hyia

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Posted 18 September 2021 - 12:07 AM

Not worried about the size,  just  very disappointed that it would not focus with out some user intervention.   FL2400mm and F12 will be great for planetary Photography.

Teams up nice with my Redcat51 and AT130 EDT..

Hi Bob,

 

If I understood your first post correctly, it would focus if you used the extensions.  I think that the idea with the scope was that without any extensions, you might be able to use a binoviewer.  Using just one extension you could use a 2" diagonal.  Two extensions probably work for a 1" diagonal.  Three extensions needed for your case where you are using none of those.  I'm just guessing?  I've been thinking about getting this scope, but don't have it.

 

I think the mirror spacing is set to minimize some aberrations.  If you don't detect any when moving the mirrors, great.  As far as not wanting to use all the extensions, I can see that especially if you are hanging something heavy on it.  I do think that is the way GSO intended it however.  Perhaps they can be faulted for trying to make it a "jack of all trades"?

 

Anyways, please post some of your pictures taken with the scope if you get the chance.

 

Edit:  For those who do want to adjust the mirror spacing, post #8 in the following thread may be of interest: https://www.cloudyni...cing/?p=6541606


Edited by hyia, 18 September 2021 - 08:22 AM.


#1394 BobW55

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Posted 18 September 2021 - 09:53 AM

Hi Bob,

 

If I understood your first post correctly, it would focus if you used the extensions. 

 

My problem was I could not get focus with all 3 extensions in place, even using a diagonal did not help. 

After looking at the few pictures I could find of the secondary mirror, I discovered mine was about 2.5mm CLOSER to the primary mirror.

Once I understood how to adjust the distance, I move the mirror away I was able to achieve focus using just 1 of the 1" extensions and my camera.  No barlow or diagonal used.

Due to clouds I have not been able to adjust the culmination (which was good before I adjusted the mirror)

I have NOT touched the primary mirror adjustments.

Being able to remove one 1" extension and one 2" extension, I have removed 14.2oz  (403g) of weight from the rear of the scope.   This makes me very happy.


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#1395 quilty

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Posted 19 September 2021 - 06:23 AM

Hi Bob,

that's quite a success, isn't it? You say, your secondary was 2.5 mm closer to the primary mirror, compared to what? Do ou know the "correct" distance? That's no critisizing, just for interest.

Stephan



#1396 BobW55

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Posted 19 September 2021 - 08:46 AM

Hi Bob,

that's quite a success, isn't it? You say, your secondary was 2.5 mm closer to the primary mirror, compared to what? Do ou know the "correct" distance? That's no critisizing, just for interest.

Stephan

Who knows what the correct distance "SHOULD" be.  Not published in the manual.  In fact it makes no mention about moving the secondary to primary distance.

I do which there was a published distance +- that would still provide acceptable results.

Just glad I learned another interesting lesson in Optical mirrors.



#1397 quilty

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Posted 19 September 2021 - 10:41 AM

But still. your sec was 2.5 mm closer to the primary, compared to what? The published distance, which is how much?



#1398 BobW55

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Posted 19 September 2021 - 07:01 PM

But still. your sec was 2.5 mm closer to the primary, compared to what? The published distance, which is how much?

As stated....NO ONE KNOWS




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