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New AT 6" and 8" Classical Cassegrain

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#751 skywolf856

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Posted 18 July 2019 - 07:36 PM

I still don't understand why AT began the sales talk of these telescopes before anyone else came up with there copies (GSO, Orion) for sale and Astronomics still doesn't have any to sell while it seems everyone else has them in 6" & 8" sizes white and black?  And Astronomics still after all this time can't even give us a sales page showing anything on the 8" version.

What's up with that???



#752 mclewis1

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Posted 19 July 2019 - 08:50 AM

I suspect that there's more going on than simple shipping issues. I believe that given the volume of business and past relationship that Astronomics carries more weight with GSO than just about any other distributor, so not having these CC scopes suggests to me there's more to the story.


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#753 starman876

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Posted 19 July 2019 - 05:39 PM

Not sure yet. To be honest those two sizes were a surprise.


Sent from my iPad using Tapatalk

So how would the cassegrains in this thread stack up optically against the ones from this company?

 

https://cfftelescopes.eu/reflectors/



#754 Starlease

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Posted 19 July 2019 - 08:31 PM

GSO vs. Zambuto or Takahashi Mewlon, a really big difference.

But most people are interested in lowest cost so they will never know what a difference optical quality makes.


Edited by Starlease, 19 July 2019 - 08:31 PM.

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#755 starman876

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Posted 19 July 2019 - 11:31 PM

GSO vs. Zambuto or Takahashi Mewlon, a really big difference.

But most people are interested in lowest cost so they will never know what a difference optical quality makes.

I understand, but curious how reviews of these new cassegrains have compared to other makes available.  



#756 Ala Shahin

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Posted 08 August 2019 - 12:32 AM

I have found a detailed and interesting review on a Japanese site of Kasai Trading's GS-150CC telescope which is essentially the same as the GSO, AT, TS, Orion (USA) 6" F12 Classical Cassegrain. Google translation does a decent job of making it an easy enough read:

 

http://reflexions.jp...019/06/05/8917/

 

I thought it may prove interesting and useful to some and hence I am sharing it.

 

Ala


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#757 gwlee

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Posted 08 August 2019 - 11:19 AM

GSO vs. Zambuto or Takahashi Mewlon, a really big difference.

But most people are interested in lowest cost so they will never know what a difference optical quality makes.

Some people have compared  Zambuto and Mewlon side-by-side to less expensive imports for months and found the differences were subtle under their seeing conditions. 


Edited by gwlee, 08 August 2019 - 11:24 AM.

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#758 aneeg

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Posted 08 August 2019 - 11:26 AM

Isn`t about time to see some images taken with these new CCs?

 

Arne



#759 Astrojedi

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Posted 08 August 2019 - 11:39 AM

Some people have compared  Zambuto and Mewlon side-by-side to less expensive imports for months and found the differences were subtle under their seeing conditions. 

Yes, for larger apertures the differences are very subtle in typical observing conditions. Where premium optics shine are in smaller apertures in all conditions and in larger apertures in excellent observing conditions.



#760 davebl

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Posted 08 August 2019 - 11:45 AM

Here's an image taken with the 8" CC. M63 LRGB 4 hours of 5 minute exposures using the AP CCDT67 reducer.
Dave
I did replace the focuser with a Moonlite for better collimation.

Attached Thumbnails

  • M63_2.jpg

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#761 gwlee

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Posted 08 August 2019 - 01:11 PM

Isn`t about time to see some images taken with these new CCs?

 

Arne

Astronomics hasn’t started shipping them yet according to Michael’s last report here. 



#762 Tyson M

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Posted 12 September 2019 - 03:34 PM

With the relentless dew this summer, the idea of owning one of these is becoming better and better.

#763 aa6ww

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Posted 22 September 2019 - 03:58 PM

Just a quick comment about the secondary obstruction percentage vs the secondary mirror obstruction percentage terms.

 

When the Edge HD 8" first came out, some of the advertisements claimed a secondary mirror obstruction of 31 percent which got some people excited, but it was true, the mirror itself was at 31 percent. The actual secondary obstruction was however 34 percent. 

 

I see this play on words again with the Orion CC8 8" f/12 Classical Cassegrain Telescope on their home page claiming a 34 percent Secondary "mirror" obstruction. Maybe its all the same thing, but maybe it isn't?

 

In the end, it really just maters how it performs, but some have said the actual central obstruction is larger.

 

Has anyone actually measured their secondary obstruction size of an 8" F12 CC? Again, this is just a number game which we all play out here but I do notice how marketing tends to find these loopholes in terms for those who live and die and even debate by the numbers.

 

My appologies if this has already been brought up. This is a long fun thread but very difficult to read unless its done over a few days or weeks. Ive become more interested because one of my friends just ordered an Orion 8" CC F/12 and is pretty excited about it. So I'm kinda jazzed for him also. 

 

In the next few weeks he and i will be viewing together, since I have a C8 Edge HD and absolutely love the pristine optics, especially now that I exclusively use my 2" diagonal and 2" 100 deg eyepieces. 

 

Finally, I read the other day about two refractors of the same aperture comparing contrast, and the end results were both refractors had to be at the same magnification on the same object at the same time for the comparision to be fair. This should also be the case when comparing two cassagrains of the same aperture with different focal lengths.

 

...Ralph


Edited by aa6ww, 22 September 2019 - 04:01 PM.

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#764 doug mc

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Posted 22 September 2019 - 06:30 PM

This will be good, keep us posted.



#765 mclewis1

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Posted 23 September 2019 - 07:55 AM

Yes, but there will be a bit of apples to oranges in the comparison.

 

Using an 8" EdgeHD with a 2" diagonal and 100° eyepieces to me means DSO observing where a small difference in the obstruction % isn't going to be very visible. Planetary observing is where any differences in optical performance is more likely to be noticed, and even there only under very good conditions.

 

Don't get me wrong, I love the idea of a bit of a side by side comparison between the scopes and also look forward to the discussion ... but unless you reduce the variables (for example by using the same diagonal and eyepiece, and waiting for really good seeing conditions) it's not really going to tell you too much about the critical differences in optical performance beyond a possible small difference in background contrast.



#766 luxo II

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Posted 24 September 2019 - 05:50 AM

It isn't just the CO. Straight from the horses mouth: https://celestron-si...English_web.pdf

 

Start with figures 4 and 5 which suggest that while the standard SCT's were OK on-axis their performance deteriorates rapidly off-axis. Conversely while the EDGEHD isn't exactly perfectly corrected on axis, it's a lot better off-axis. The spot diagrams are disclosed at pp17-20.

 

Then there is Figure 2 which is I expect is from the marketing department. It implies the EDGEHD scopes should be better than the standard SCT's across the whole field, both on-axis and off axis. But the top row also concedes the standard SCT's were never particularly well-corrected, even on-axis.

 

An as for Appendix A.. its suggesting the seeing lists the resolution most of the time ergo the resolution of the SCT's doesn't need to be any better than that. So their design was lazy from the outset -  never aiming to to deliver the resolution possible if you were lucky enough to be blessed with that one night of the year with rock steady seeing.

 

If you have a good one, consider yourself lucky.

 

But the well-made gregory maksutovs are corrected on-axis to 3rd order, limited only by 5th order SA and residual spherochromatism (and thats less than that in SCTs), and off-axis are a lot better. And the Rumaks are even better corrected. And may have rather smaller CO (depending on the particular design). But a good one costs more than an SCT... in some cases a LOT more.


Edited by luxo II, 24 September 2019 - 06:05 AM.


#767 Astrojedi

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Posted 24 September 2019 - 03:08 PM

It isn't just the CO. Straight from the horses mouth: https://celestron-si...English_web.pdf

 

Start with figures 4 and 5 which suggest that while the standard SCT's were OK on-axis their performance deteriorates rapidly off-axis. Conversely while the EDGEHD isn't exactly perfectly corrected on axis, it's a lot better off-axis. The spot diagrams are disclosed at pp17-20.

 

Then there is Figure 2 which is I expect is from the marketing department. It implies the EDGEHD scopes should be better than the standard SCT's across the whole field, both on-axis and off axis. But the top row also concedes the standard SCT's were never particularly well-corrected, even on-axis.

 

An as for Appendix A.. its suggesting the seeing lists the resolution most of the time ergo the resolution of the SCT's doesn't need to be any better than that. So their design was lazy from the outset -  never aiming to to deliver the resolution possible if you were lucky enough to be blessed with that one night of the year with rock steady seeing.

 

If you have a good one, consider yourself lucky.

 

But the well-made gregory maksutovs are corrected on-axis to 3rd order, limited only by 5th order SA and residual spherochromatism (and thats less than that in SCTs), and off-axis are a lot better. And the Rumaks are even better corrected. And may have rather smaller CO (depending on the particular design). But a good one costs more than an SCT... in some cases a LOT more.

 

I agree with you that the impact of central obstruction on visual contrast is overblown. This is the point I make in these forums all the time. Optical quality is a primary factor but there are many more factors impacting contrast which are completely ignored.

 

But a few corrections - figures 4 and 5 compare "Coma Free" SCTs to EdgeHD... "Coma Free" being a reference to Meade's ACF scopes.

 

You are also drawing some strong conclusions without too much support. In figure 2 the top row does not imply that performance is poor. In fact if that spot diagram is correct , over 85-90% of the light is being concentrated within the central spot which is very very good. The EdgeHD scopes deliver an even tighter spot size. In fact the flat field performance of the EdgeHD is quite incredible given the price point.

 

Appendix A is pointing to the fact that even in almost perfect seeing you will capture almost all the information there is using imaging cameras. In fact the optics are diffraction limited even in 1" seeing. I don't see how that is evidence of lazy design.

 

I would like to see the CC manufacturers provide a whitepaper similar the Celestron EdgeHD whitepaper and stand behind their claims. I am not saying the CCs are bad scopes but I have more confidence in the typical quality of EdgeHDs - having looked through 20+ samples than I have in the CCs.


Edited by Astrojedi, 24 September 2019 - 03:13 PM.


#768 aa6ww

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Posted 29 September 2019 - 04:43 AM

Had a chance to look through my friends new Orion 8" F/12 Cassegrain last night. The conditions were poor, we were on his driveway with street lights nearby, clouds were in the sky, poor conditions but it didn’t mater, the scope was new and we were out using it.

First impression is the scope is just outright beautiful just to look at. Glossy black paint, excellent robust focuser. It’s like a load bearing GSO  focuser. It had no issues supporting a heavy ES 25mm 100 deg mammoth.

The mount the scope was on was just junk. A wobbly twilight 2 Alt Az mount. Very difficult to locate anything with, even with a laser pointer.

Moving past that, right out of the box, the scope was horribly out of alignment. In focus stars looked horrible.

OK so let’s realign the optics. Fortunately, the secondary uses Allen head screws, so someone did it right. The optics were way off, more than any SCT I’ve ever seen ever. I doubt it was even aligned at the factory. Regardless, with me at the eyepiece, and my friend with the Allen wrench, about 4 minutes later the out of focus donut was excellent on Vega at well over 200x. The screws were all turned mostly tightening the secondary, not loosening them so alighment should hold fine with no problem.

 

Clouds were rolling in fast. Contrast was excellent, despite the streetlights in our face. Using the 25mm ES 100 deg eyepiece, the back ground skies were dark and stars focused sharp. In focus, Vega had the 4 spikes from the secondary vanes. It looked very cool, The spikes were just barely there but you could see them and it didn’t distract from brilliant Vega at all. It made Vega look picturesque.

 

I managed to find the ET Cluster in Cassiopeia. The views were as good as any I have seen in an 8" Cassegrain. Stars were very sharp and focused tight. Moving the cluster to the edge of the field of view didn’t affect the sharpness at all. Very nice dark skies, maybe all those light baffles were working as expected.

 

I moved the scope over to M15. The cluster was beautiful. At 211x, it was large and induvial stars in the cluster were easy to detect. Focus was excellent, the external focuser was doing a great job as expected.

I tried to move the scope over to M27 which was directly overhead but the clouds were moving too fast and in minutes, the entire sky was covered in clouds.

 

My Initial impression was, I see zero issues with anyone wanting this scope as a visual only telescope, even over the highly over rated Edge 8 HD. I didn’t notice cool down issues since the scope was out for about 2 hrs. before I even showed up.

 

Contrast was excellent, the back ground skies were much darker than I had thought they would be. The focuser was perfect how it operated and rotated. Adjustments were easy with the tension knobs underneath. Stars were sharp across the entire field of view.
What more can you ask for in a reasonably inexpensive 8" Cassegrain. Both the Vixen and D series mounting bars were well made and sold, not like the cheap orange brackets you get from Celestron, more like the ones you would get from ADM, at least on the Vixen mounting bar.

 

The black paint was excellent, very glossy. The scope was noticeably longer then an 8" SCT.  At least regarding stars and how they view in this scope, the views were excellent. Sharp focused stars, exactly what you would want in a new Cassegrain.

The OTA is noticeably heavier than the Edge HD 8, maybe up to 5 pounds heavier. Still, a very light scope for any GP5 size mount.

 

How it compares to my Edge 8 HD, at least at this point, I don’t see how it would mater. If you bought this scope and had this type of initial performance, I wouldn’t care how someone else’s scope performed. I’d be proud to say I have this one and its working beautifully and use and enjoy it.

 

Next time out, I'll measure the central obstruction, but again, at this point, it wouldn’t mater, the scope performs beautiful and looks stunning.

 

...Ralph


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#769 Bill Barlow

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Posted 29 September 2019 - 11:27 AM

Thanks for the report Ralph, sounds like the CC scope performs very well after collimating it.  Would be interested in how it performs on Jupiter and Saturn.  I see the Agena Astro also sells these CC scopes, but they will take the time to do optical checks and align the optics if needed before shipping it to you for no extra charge.  I might be interested in the 6” model at some point.

 

Bill



#770 aa6ww

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Posted 29 September 2019 - 10:27 PM

This year was terrible for seeing condtions for observing both Jupiter and Saturn. I didnt see one 5/5 day of observing all season based on our clear sky clock. I feel sorry for anyone who bought a scope this year specifically for observing Jupiter and Saturn. Hopefully they used it for other reasons once they realized this was the worse year ever for observing the gas giants, at least over here in California. 
  Little scopes under 4" I think did ok since they are visually limiting anyways and are more forgiving to medoicure conditons. 
 
...Ralph
 
 

Thanks for the report Ralph, sounds like the CC scope performs very well after collimating it.  Would be interested in how it performs on Jupiter and Saturn.  I see the Agena Astro also sells these CC scopes, but they will take the time to do optical checks and align the optics if needed before shipping it to you for no extra charge.  I might be interested in the 6” model at some point.
 
Bill


Edited by aa6ww, 30 September 2019 - 07:47 PM.

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#771 John59

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Posted 30 September 2019 - 09:08 AM

 This year was terrible for seeing condtions for observing both Jupiter and Saturn. I didnt see one 5/5 day of observing all season based on our clear sky clock. I feel sorry for anyone who bought a scope this year specifically for observing Jupiter and Saturn. Hopefully they used it for other reasons once they reaslized this was the worse year ever for observing the gas giants, at least over here in California. 

  Little scopes under 4" I think did ok since they are visually limiting anyways and are more forgiving to medoicure conditons. 

 

...Ralph

Ralph, 

Great report!

I too have the Orion CC8 since they first came out.

I have had all summer to try various eyepieces and cameras.

Mine also arrived out of collimation but not as bad as your experience.

I practice EAA and only use an iOptron AZ Mount Pro.

The results are stunning with this telescope.

My primary targets are Planetary Nebulas and this telescope excels at them. 

I use it at my primary residence in town under Class 7 bordering on 8 Bortle  skies with decent results.

However, under my retirement property in West Texas bordering between Class 2 and 3 the views and imaging is stunning.

This has become my goto telescope to get good details of the smaller objects such as planetary nebulas.

With Globulars such as M5, M22 etc. it is as if you are looking into them and not at them.

The star resolution is excellent!

Seeing as well as imaging gives great results on the structure and actually seeing individual stars in the globs.

Having different SCTs in the past I am very glad to have this CC8 and quite honestly if I still had the SCTs I would use this one over them.


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#772 michiel

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Posted 30 September 2019 - 09:10 AM

Hi Ralph,

thanks for the report.Looks promising. I am considering the 8 inch version from TS- teleskopservice.

You said " How it compares to my Edge 8 HD, at least at this point, I don’t see how it would mater. If you bought this scope and had this type of initial performance, I wouldn’t care how someone else’s scope performed. I’d be proud to say I have this one and its working beautifully and use and enjoy it."

 

As a matter of fact it does matter to me at least , I am familiar with the C8 and I am wondering whether  the CC performs at the same or at a different level concerning deep sky (pinpoint stars) and planets/moon. It could change my opinion on purchasing one, or maybe consider a celestron c 8 edge or even a celestron c9.25.

So If you still want to compare them, I would be interested in your opinion.

regards

Michiel



#773 Bill Barlow

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Posted 30 September 2019 - 09:49 AM

Is it true that you have to keep changing the extension adapters to allow longer focal length eyepieces to come to focus?  This would be a big turn-off for me having to do this frequently.  I would think with this focusers ample amount of backfocus you wouldn’t have to do this at all.

 

Bill



#774 aa6ww

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Posted 30 September 2019 - 10:54 AM

We went from using my friends ES 25mm 100 deg eyepiece down to his 8.8mm ES 1.25" using the same 2" diagonal and everything focused just fine with no issues. We even inserted his 2" ES Extender into the diagonal and there was still plenty of focus range using other eyepices he had also. He just used one additional extension tube on his scope then installed the focuser. He probably didnt even have to use that. 
 
Honestly, it never crossed our minds about whether the scope was going to reach focus, it just did. 
 
...Ralph
 
 

Is it true that you have to keep changing the extension adapters to allow longer focal length eyepieces to come to focus?  This would be a big turn-off for me having to do this frequently.  I would think with this focusers ample amount of backfocus you wouldn’t have to do this at all.
 
Bill


Edited by aa6ww, 30 September 2019 - 07:48 PM.

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#775 aa6ww

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Posted 30 September 2019 - 11:22 AM

I have a C8 Edge HD and have been enjoying it. Last Saturday when I was at my friends house trying out his new scope and helping him set it up, I didnt bring my scope so we could focus on getting his set up and trying it out and seeing how it all worked on his mount.

My initial evaluation on his scope vs my Edge HD is that his scope is every bit as sharp and precise as my Edge HD. I have absolutely no noticible image shift in my focusing and despite that, the focuser on his scope is naturally more precise.

This is really not a good year for evaluating optics on planets but side by side on the same night should say something one way or the other.

 

If the weather holds out, we may get under some open horizons and do some observing together, him with his new scope and me with my Edge 8, maybe. He has a very busy life style and schedual, and astronomy is not high on his list of priorities.

 

I'll do my best to see what I can do for a comparision between the two.  Next saturdays weather is looking promissing over here, despite the moon in the sky.

 

For the record, I wouldn't give up my C8 for his CC, only because my scope is considerably lighter then his and i perfer the close tube design and compactness of my scope. If I wanted a 19 pound 8" cassagrain, id just get a C9.25 Edge. but Im not sure my mount could handle the weight and be as stable as my C8.

 

...Ralph

 

 

 

Hi Ralph,

thanks for the report.Looks promising. I am considering the 8 inch version from TS- teleskopservice.

You said " How it compares to my Edge 8 HD, at least at this point, I don’t see how it would mater. If you bought this scope and had this type of initial performance, I wouldn’t care how someone else’s scope performed. I’d be proud to say I have this one and its working beautifully and use and enjoy it."

 

As a matter of fact it does matter to me at least , I am familiar with the C8 and I am wondering whether  the CC performs at the same or at a different level concerning deep sky (pinpoint stars) and planets/moon. It could change my opinion on purchasing one, or maybe consider a celestron c 8 edge or even a celestron c9.25.

So If you still want to compare them, I would be interested in your opinion.

regards

Michiel


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