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New AT 6" and 8" Classical Cassegrain

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#1051 quilty

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Posted 09 August 2020 - 09:03 AM

torch test

I see no point why the torch test schould be failing on both, co and aperture, so I completely trust in it.

Maybe I did some mistake when assessing the real cc's focal length. First, repeatedly readings of true magnification with eyepieces of certain focal length yielded somewhat between 2 and 2.1 m.

In the last weeks I read true fov angles through the same eyepieces after measuring their proper fov angles. The real angles were given by known star distances (by angle) for instances pleiades offer a goot variety of star distances to fit a certain eyepiece. Did the same on the moon, when the exact distance was known, and it perfectly fitted into the 15mm 66° eyepiece yielding a focal length of 1.8 m thus much more consistant to the data provided by supplier. Haven't got a clue yet, why this discrepancy because the same eyepieces were involved.

And did a third approach by measuring star passing times thru a 4 mm 60° eyepiece compared to the Bresser 102/460 short refractor. Result: supposed the Bresser 460 mm are correct, the CC yields 1.80 m, the Mak 2.0 m. 

 

Last weeks and days provided Neowise and Saturn and Jupiter and warm nights. That's my time. But I watch again and stll through Bresser 127 mm Mak and skip the CC. I'm even using the original (but mechanically improved) Bresser plastic diagonal. Why? Because this combination weighs just half of the CC + 2 inch 1/10 lambda 99% reflective diagonal and provides more detail, resolution and contrast than the latter. At least at the state when I stopped collimation procedure because I could not improve any more. 

Saw structures and Moon shadow on Jupiter Friday night like never before. Also M13 and similar are more brilliant thru the Bresser. When watching doubles two airy spots are easily to tell apart surrounded by little side maxima. Thru CC the side maxima are way brighter than the star itself, if I can find it at all. My CC is able to do nothing which the Mak isn't doing better except the now fixed mirror flop. And CC takes longer acclimatisation time, well not now at nights warmer than 20 °C.

Light catching area Mak: 108 cm², CC: 122 cm², not worth to go there for this 13% plus of light. When the light doesn't appear where it belongs.

 

Well I'm completly visual, taking pics might change a lot.



#1052 Thandal

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Posted 31 August 2020 - 08:40 PM

Especially fun if you have a way to mount your future CC6 side-by-side with your 6" Newtonian.  I think it would be fun to be able to look into one eye piece at f/4.5 and then move my head to a different eye piece at f/12.  I can almost get there, but have to change secondary mirrors on my Parks HIT.

I have almost this exact set-up on my iOptron AZ Mount Pro.  (Loving this mount, btw, despite its idiosyncrasies.)

 

My f/12 Orion-branded CC8" (just upgraded from an Orion CC6" I purchased a year ago by swapping with another CN member) is sitting side-by-side with my f/5 Orion 130mm newtonian.  So I have compared both the CC6" and CC8" models to the newt.

 

It's... interesting.  As the optometrists ask, "Which is better?  #1?  Or #2?  Better? Or just smaller and darker?"  For the past year the nights here along the mid-Atlantic coast have offered very few opportunities for long observing sessions, when they've offered anything at all. So I haven't taken detailed notes.  But overall, the optics (not to mention the aperture!) of both CCs are better, with the obvious improvements in detail and contrast.  And as I'm an exclusively visual observer and my main observing targets are in the solar system, that's important.

 

But for sheer "Wow!" in the initial field of view of both the recognizable solar system objects, (Moon, Jupiter, Saturn) and and the brighter DSOs, the f/5's wider picture (depending on EP, of course) is worth a lot.  Hopping between the two instruments isn't as much fun as I had thought it might be, and of course it limits the second one to the same target as the primary.  So most of the time I set-up each 'scope on its own mount and look at different (or the same) targets.

 

Which is better?  Maybe just "smaller but brighter."  lol.gif


Edited by Thandal, 31 August 2020 - 08:42 PM.


#1053 Cosmosaurus

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Posted 31 August 2020 - 11:18 PM

So I have compared both the CC6" and CC8" models to the newt.

Could you compare CC6 and CC8 ? (views with same x, mechanical management, focuser, ...), please ?

 

Cheers



#1054 Thandal

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Posted 01 September 2020 - 12:17 AM

Could you compare CC6 and CC8 ? (views with same x, mechanical management, focuser, ...), please ?

 

Cheers

 

tl;dr:  Observing report:  I've only had the 8" out once (last night) and seeing was poor, as it's been all year for things low to the horizon.  And the remnants of Laura have only added to the problems.  But I did get brief looks at Jupiter, Saturn, the Moon, and several double-stars during breaks in the clouds.  Even caught the beginning of a transit of Io before the clouds rolled-in completely for the night.

 

The 8" provided noticeably better views than the 6" of details on Jupiter, and the Cassini Division and ring shadow(s) on Saturn.  The Moon showed a similar increase in detail, but it was hard to spend much time determining exactly how much because the brightness overwhelmed and I was too lazy to dig out my moon filter.

 

Can't do a direct comparison.  Since I swapped the CC6" for the CC8" I never had both at the same time.

But here's what I can say from memory:

 

Obviously the 33% increase in aperture, with all that provides, is the big reason to go to the 8".  But that comes at a cost in weight (50% more, 18 lbs. vs. 12 lbs.) and, well... cost.  Almost 100% more $$ at retail.  lol.gif

 

The other differences are minor.  They are all noted in the (Orion) descriptions, and in the User's Manual itself.  (It's one manual for both models, available on-line for free.)

 

  • 8" has a slightly smaller central obstruction (by %)
     
  • 8" has 50mm of focuser travel, the 6" has 35mm.  With the 6" I needed to add another one of the (supplied) extension rings and/or an eyepiece extender tube to reach focus with a Barlow.  The manual already notes that visual observers generally need to add the 2" ring to begin with.  I haven't tried with the 8" and it's longer focuser travel yet.
     
  • 8" has a more robust focuser with a linear bearing.  I didn't find that to be an issue with the 6", but I'm attaching no more than a diagonal and an eyepiece.  (Ok, and sometimes a filter as well.)
     
  • 8" has both a Losmandy and a Vixen dovetail bar.  They can be swapped (the mounting screws are in the same relative locations, top and bottom.)  The 6" only has the Vixen bar.  I *think* that the 6" had the same mounting screws on top, just no bar.  So one could add another if desired with minimal work.

 

And that's about it.  The designs are identical, and the optics appeared (to me) to be of the same quality.  I presume it's the same GSO manufacturing line making all of these, so that was no surprise.  Star testing indicated good collimation and the expected Airy disk patterns.

 

The only reason I didn't get the 8" to begin with was that I didn't want to have to get a better mount than the one I already had.  Thought that one could carry the 6".  It couldn't.   crazy.gif

 

Bottom Line: At f/12 these are designed for the kind of work I enjoy; lunar and planetary visual observing.  They would also be excellent (on the right mount) for AP.  I am very pleased with both models, and would recommend either.  The choice between them comes down to individual needs/wants regarding size, (the 8" is considerably larger in every dimension) and as always, budgetary considerations.  waytogo.gif


Edited by Thandal, 01 September 2020 - 12:24 PM.

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#1055 CCD-Freak

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Posted 01 September 2020 - 11:07 AM

I love the idea of the 8", at least everything but the weight. I wouldn't need the Losmandy D-style mounting rail and would want to switch it out for the Vixen rail. Getting rid of the wide D rail would shave about two pounds off the weight. Anyone know if this is possible without physical alterations? The radius blocks on the bottom would need center holes to do so and Losmandy plates usually mount with two bolts at each end rather than one. Given that the effective aperture is less than the actual, the 8" has become much more appealing.

If the Classic Cass uses the same mechanics as the RC scopes you should have no problem.  I swapped the vixen and Losmandy rails to make the label right side up.  The hole patterns were the same and I figure the AT8CC is most likely the same.  ADM sells vixen rails for the AT scope last time I looked.

 

AT6RC_CI-700.JPG

 

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#1056 jgraham

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Posted 01 September 2020 - 02:48 PM

Yep, you can swap the rails on the 8" CC; I have done that with mine. If you want to save weight you can remove the extra rail and install bolts to secure the tube to the end rings. That should eliminate any structural issues.
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#1057 Terra Nova

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Posted 01 September 2020 - 03:42 PM

Yep, you can swap the rails on the 8" CC; I have done that with mine. If you want to save weight you can remove the extra rail and install bolts to secure the tube to the end rings. That should eliminate any structural issues.

That is exactly what I wanted to hear. I would put the Vixen rail on the bottom and a simple, flat 1” wide aluminum plate with a handle on top. I would think that would also reduce the weight by atleast a pound. Now I’m even more intrigued. After mulling a 6” over for a long time, the 8” is the only one that really makes sense IMO. Especially after Larry Carlino’s fine review and your comments. If I ever talk myself into another scope, I think an 8” CC might be just the ticket. Particularly since you indicate it does well on an LX70 GEM which I have.



#1058 jgraham

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Posted 01 September 2020 - 04:52 PM

Indeed is does...

 

LX70 GSO CC8 (8-1-2020)-2.jpg

 

...mine is the GSO version of the scope. They were out of stock at Astronomics when I was hunting around for one and Agena had a couple of the GSOs in stock.

 

Being easy to set up and quick cool-down this has become one of my favorite grab'n go scopes for a quick look at Jupiter and Saturn on a work night. :)

 


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#1059 teechinghong

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Posted 03 September 2020 - 08:15 AM

Hi owners of CC6 or CC8 f/12, you guys tried this telescope on planetary imaging? How's the performance?

I just haven't seen anybody post it anywhere ... be it in Youtube ... Instagram ... or even this forum. 



#1060 Cosmosaurus

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Posted 03 September 2020 - 08:33 AM

https://www.cloudyni...ic-cass-8-inch/



#1061 TerryB

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Posted 03 September 2020 - 09:38 AM

Astrobin.com is a reasonably popular site for astrophotographers to showcase images, and it has a search page.  Try "GSO Cassegrain".

 

Hi owners of CC6 or CC8 f/12, you guys tried this telescope on planetary imaging? How's the performance?

I just haven't seen anybody post it anywhere ... be it in Youtube ... Instagram ... or even this forum. 

 



#1062 Thandal

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Posted 03 September 2020 - 08:15 PM

Astrobin.com is a reasonably popular site for astrophotographers to showcase images, and it has a search page.  Try "GSO Cassegrain".

Several more pics show up if the search term is: "Classic Cassegrain".  Most were taken with the GSO 6" model.

 

(I did see a fair number of SCT shots mixed in with the results.  undecided.gif )



#1063 Terra Nova

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Posted 04 September 2020 - 08:55 AM

Indeed is does...

 

attachicon.gifLX70 GSO CC8 (8-1-2020)-2.jpg

 

...mine is the GSO version of the scope. They were out of stock at Astronomics when I was hunting around for one and Agena had a couple of the GSOs in stock.

 

Being easy to set up and quick cool-down this has become one of my favorite grab'n go scopes for a quick look at Jupiter and Saturn on a work night. smile.gif

That’s a gorgeous setup!



#1064 quilty

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Posted 08 September 2020 - 04:33 AM

I love the idea of the 8", at least everything but the weight. I wouldn't need the Losmandy D-style mounting rail and would want to switch it out for the Vixen rail. Getting rid of the wide D rail would shave about two pounds off the weight. Anyone know if this is possible without physical alterations? The radius blocks on the bottom would need center holes to do so and Losmandy plates usually mount with two bolts at each end rather than one. Given that the effective aperture is less than the actual, the 8" has become much more appealing.

This is a question I had some pages ago. They care about acclimatisation an thermal expansion and therefore use quartz mirrors. Once again, thermal expansion of the mirror considering the overall length of the part is just a fraction of the expansion of steel (tube) and alloy (vixen and losmandy). And it is still when you substract steel expansion from alloy expansion. As the connecting rails connect directly the bottom plate to the sec bearing ring like a bridge there is the question if thermal expansion might shift the scope not just out of focus but out of collimation when there's just one rail. I think a 20° shift yields a 0.1 mm length difference between alloy and steel on a 40 cm length. So, when we suggest the connection of the mirror beraring parts to the steel tube is strong enough to overcome any shift in he alloy part everything is fine. Otherwise I think a 0.1 mm shift on just one side of the front ring is enough to spoil the collimation.



#1065 macdonjh

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Posted 08 September 2020 - 09:14 AM

This is a question I had some pages ago. They care about acclimatisation an thermal expansion and therefore use quartz mirrors. Once again, thermal expansion of the mirror considering the overall length of the part is just a fraction of the expansion of steel (tube) and alloy (vixen and losmandy). And it is still when you substract steel expansion from alloy expansion. As the connecting rails connect directly the bottom plate to the sec bearing ring like a bridge there is the question if thermal expansion might shift the scope not just out of focus but out of collimation when there's just one rail. I think a 20° shift yields a 0.1 mm length difference between alloy and steel on a 40 cm length. So, when we suggest the connection of the mirror beraring parts to the steel tube is strong enough to overcome any shift in he alloy part everything is fine. Otherwise I think a 0.1 mm shift on just one side of the front ring is enough to spoil the collimation.

I haven't seen this in practice.


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#1066 Thandal

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Posted 08 September 2020 - 10:14 AM

This is a question I had some pages ago. They care about acclimatisation an thermal expansion and therefore use quartz mirrors. Once again, thermal expansion of the mirror considering the overall length of the part is just a fraction of the expansion of steel (tube) and alloy (vixen and losmandy). And it is still when you substract steel expansion from alloy expansion. As the connecting rails connect directly the bottom plate to the sec bearing ring like a bridge there is the question if thermal expansion might shift the scope not just out of focus but out of collimation when there's just one rail. I think a 20° shift yields a 0.1 mm length difference between alloy and steel on a 40 cm length. So, when we suggest the connection of the mirror beraring parts to the steel tube is strong enough to overcome any shift in he alloy part everything is fine. Otherwise I think a 0.1 mm shift on just one side of the front ring is enough to spoil the collimation.

 

I haven't seen this in practice.

 

Nor have I. 

 

Thermal equilibrium is essential for eliminating air currents within the instrument, but once that has been achieved I haven't noticed that there's any appreciable change in the image due to thermal expansion/contraction of the tube itself.  My assumption (presumption?) is that any such effect is overwhelmed by that of the air currents and would have subsided long before those.

 

NOTE:  Obviously collimation is best performed only after equilibrium has been achieved, so regardless of the source of any thermal effects they would be irrelevant at that point.


Edited by Thandal, 08 September 2020 - 10:17 AM.


#1067 macdonjh

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Posted 08 September 2020 - 11:58 AM

Nor have I. 

 

Thermal equilibrium is essential for eliminating air currents within the instrument, but once that has been achieved I haven't noticed that there's any appreciable change in the image due to thermal expansion/contraction of the tube itself.  My assumption (presumption?) is that any such effect is overwhelmed by that of the air currents and would have subsided long before those.

 

NOTE:  Obviously collimation is best performed only after equilibrium has been achieved, so regardless of the source of any thermal effects they would be irrelevant at that point.

Imagers have experienced changes in focus due to thermal growth or contraction large enough to spoil images.  That's one reason for the use of carbon fiber in telescope OTAs.  

 

I read quilty's post to be asking about distortion of the OTA due to differential thermal growth between the OTA and the dove tail bar.  In theory, since a steel OTA will grow/ shrink less than an aluminum dove tail bar with the same change in temperature, not only would the focus point of the telescope change (due to changing separation between the primary and secondary mirrors), but collimation would be spoiled as the growing/ shrinking dove tail bar bends the OTA.  

 

In practice, I think the differential growth is either so small it isn't noticed, even by a camera; or the mounting rings slide that small fraction of a millimeter on their felt liners relieving the stress induced by differential thermal growth.



#1068 Thandal

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Posted 08 September 2020 - 12:44 PM

<snip>

In practice, I think the differential growth is either so small it isn't noticed, even by a camera...

 

^^^ THIS ^^^ wink.gif



#1069 AstroKerr

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Posted 09 September 2020 - 09:51 AM

CC6 in cart. Nice size & weight, great for test drive. Viewed with Evo 8 - hmmm - CC8 in cart, CC6 out. But I have the Evo 8 and it's wonderful & no spider - hmmm - CC8 out, 180 Mak in. Oh, yeah, wanted fixed mirror. Mak out, CC6 back in - nice size & weight for test drive of a classic cass... see if I like Classic Casses. <click> done.


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#1070 mclewis1

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Posted 09 September 2020 - 11:48 AM

AstroKerr, I just heard about a good deal on a .... oh look SQUIRREL!

Uh, now what was I saying?

 

Sorry, couldn't resist lol.gif

 

 

Your post is a perfect example of the very popular condition seen around here - AADHD (astro ADHD)

 

The reality is that most folks would be very happy with any of those choices, great views and the differences will generally be minimal.


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#1071 Peter Besenbruch

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Posted 09 September 2020 - 04:04 PM

CC6 in cart. Nice size & weight, great for test drive. Viewed with Evo 8 - hmmm - CC8 in cart, CC6 out. But I have the Evo 8 and it's wonderful & no spider - hmmm - CC8 out, 180 Mak in. Oh, yeah, wanted fixed mirror. Mak out, CC6 back in - nice size & weight for test drive of a classic cass... see if I like Classic Casses. <click> done.

Lovely. Thanks for the laugh.



#1072 AstroKerr

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Posted 09 September 2020 - 06:53 PM

Lovely. Thanks for the laugh.

Oh, that went on with variations for 4 days and the CC8 kept winning. But I really did want a GnG size first, as a test. And it entails less lashing / thrashing from Sybs if she doesn't like it...

 

 I run the Evo 8 'fixed mirror' most of the time with an added focuser and love it - but it is not a CC, so I really do need test run. I think BB had an idea to add a flat plate to the front and ditch the spider (I like that idea), and then everything else mentioned here and there has me wanting to try one seriously. If it seems suitable, then I think a larger one, maybe a DK, will go on the ' Dark Homesite' list.

 

So for now, I get some scope and ep testing out of the way and get ready for the Dark Homesite out on the Rez for mid 2022 or so. These CC threads are an amazing help - Thank You, all!

 

ya wait, ya hope, ya try waytogo.gif


Edited by AstroKerr, 09 September 2020 - 08:34 PM.


#1073 Peter Besenbruch

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Posted 09 September 2020 - 10:25 PM

ya wait, ya hope, ya try waytogo.gif

And good luck with it.


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#1074 AstroKerr

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Posted 10 September 2020 - 12:45 AM

Should go well. I run numbers on the side for most things - effective this, equivalent that, CO, max, min, expected such and so, add in in-depth fiddlings as found in this thread (and others), cogitate, order and then get eyes on. Until you get your eye, an ep and the scope all together, it's all oughta be / could be / maybe.

 

This ~6" f/~12+ will tell me where I need to be for aperture and focal ratio in a folded sedentary mirror design for visual Planetary / Lunar at a nice, dark site. I have a good idea already from reading, but no 'eyes on'. This one doesn't have to 'rock', just verify a few things and point the way.  



#1075 Bomber Bob

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Posted 10 September 2020 - 06:32 AM

Should go well. I run numbers on the side for most things - effective this, equivalent that, CO, max, min, expected such and so, add in in-depth fiddlings as found in this thread (and others), cogitate, order and then get eyes on. Until you get your eye, an ep and the scope all together, it's all oughta be / could be / maybe.

 

This ~6" f/~12+ will tell me where I need to be for aperture and focal ratio in a folded sedentary mirror design for visual Planetary / Lunar at a nice, dark site. I have a good idea already from reading, but no 'eyes on'. This one doesn't have to 'rock', just verify a few things and point the way.  

I think you'll find it to be a very competent instrument.  My latest restore removed the finicky parts from my antique Tinsley 6" F20, so now I can enjoy enjoy it as a compact reflector.  The 3000mm Focal Length really helps with lunar / planetary -- 100x with a Swiss-made spectros KE 30mm with a big 35mm barrel size.  At 1800mm, yours is multi-purpose compared with mine.  I was surprised at how well these CCs do on DSOs.  I can zoom in on M31's dust lanes, or crack the larger globulars wide open.  I just have to be patient, and slowly push up the power.  IOW:  They're more than a one-trick pony.


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