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StellaLyra Classical Cassegrain & Ritchey-Chrétien Telescopes


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You can now buy Classical Cassegrain & Ritchey-Chrétien telescopes at FLO 🙂  StellaLyra Classical Cassegrain & Ritchey-Chrétien telescopes Manufactured by Guan Sheng Optical in Taiwa

Lyra meet Mira. 😁

Just pulled the trigger on a Stellalyra 6” f12 CC. Ooops!   Now to decide which scope must go to make space for it? 🤔

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17 minutes ago, Stu said:

You think you’ve got problems with three eyes Jeremy

You probably did not notice that there is finder scope in that image as well :D

 

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5 minutes ago, JeremyS said:

When you say launch, do you mean the lifeboat at the stern?
🙂

 

Yeah, it was a pun attempt :)

More seriously if the 6''CC is as good as the 8inch CC it will be a killer for the Skymax 150: they have almost identical specs, but the CC is so much cheaper and may turn out to be slightly better optically. As far as I see the Maks have just one advantage: no need for regular collimation. Compare to the advantages of the CC: fast cooldown, better focuser and no mirror shift. Skywatcher should up their game!

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The CCs don’t need regular collimation either. Not had to recolimate my CC8 since I bought it. They hold colimation really well. 

Not sure if they hold collimation as well as a mak bit certainlty won’t need doing very often.

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I just came across very important point for 8" CC if it is indeed stopped down to 7.3".

Secondary obstruction is 68mm and primary is 186mm. That makes secondary obstruction almost 37% rather than 33%.

 

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On 08/10/2020 at 23:42, vlaiv said:

I'm going to assume couple of things here:

- C8 has 97% reflective coatings and two air glass surfaces - 99.5% each, 64mm secondary obstruction, 8" / 203mm diameter

- CC has 96% reflection on mirrors, CC has ~7.3" mirror (186.5mm) and 58mm secondary obstruction

- 150mm refractor has decent AR coatings (which really means x4 air glass surfaces with 99.5% coatings).

Let's compare the three:

150ED: 75 x 75 x 0.995^4 = ~ 5513.341

C8: (101.5 x 101.5 - 32 x 32) x 0.995^2 x 0.97^2 = ~8642.825

CC: (93.25 x 93.25 - 29 x 29) x 0.96^2 = ~7238.765

Ratio of brightness between 150ED and CC is x1.313 and ratio between CC and C8 is x1.194

If explanation was that mirror is stopped to about 7.3" and all other specs are fine, one would not be able to conclude that 150ED is about the same brightness as CC and that CC is FAR dimmer than C8

@vlaiv,

I think we now know the secondary obstruction is 68.5 not 58.
If you rework the cc8 figures you get ~6289.92.

Ratio of brightness between 150ED and cc is 1.14  i.e. not noticeably different.

Ratio of brightness between cc and c8 is 0.73  i.e. quite a bit dimmer.

So if the mirror is stopped to 7.3” then it looks like the reviewers conclusion on brightness would be about right?

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4 minutes ago, globular said:

I think we now know the secondary obstruction is 68.5 not 58.
If you rework the cc8 figures you get ~6289.92.

I'm now getting 6932.736 :D

Just to make sure there is no error, let's do it step by step

CC: (93.25 x 93.25 - 34.25 x 34.25) x 0.96^2 = (8695.5625 - 1173.0625) * 0.96^2 = 7522.5 * 0.96^2 = 6932.736

Mak150 to CC = ~25% increase in light

CC to C8 = ~25% increase in light

This time it sits pretty much in between the two.

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23 hours ago, johninderby said:

Now the wait for the CC6 begins. 😁

067BD591-A42B-499A-89DF-2B8187F5E0FF.jpeg

Well, should be arriving pretty quickly today. Estimated between 9:19 and 10:19, so delivery no; 16 on the list. 😁

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Thing to remeber about the SCT is it’s focal length and effective aperture changes as it is focused and then there is mirror flop of course and cool down, dewing and the very rarely seen perfectly collimimated one. 

I wouldn’t go back to a C8 as for me the CC just has too many asvantages. 🙂

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36 minutes ago, johninderby said:

Worth waiting for. 🙂👍🏻

Arrived 1 minute early. 😁

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Hoping for clear skies which I got unexpectedly last night after midnight. 🤞🏻

Edited by Knighty2112
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Finderscope fitted and roughly aligned on farthest chimney! 👍🏻🧐

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 Now testing to see how focuser holds up with EP pulling down on it.

Edited by Knighty2112
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