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GSO 6inch F12 Classical Cassegrain It’s A Winner!

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#26 macdonjh

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Posted 14 April 2019 - 08:59 AM

Oh, and with 6" of aperture, I think, "just different" explains why somebody would buy a classical Cassegrain over a Maksutov, SCT or Newtonian.  I think somebody else earlier in this thread has a reasonable explanation for why it's being offered in the first place: proof of concept.


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#27 Axunator

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Posted 14 April 2019 - 08:53 PM

Oh, and with 6" of aperture, I think, "just different" explains why somebody would buy a classical Cassegrain over a Maksutov, SCT or Newtonian. I think somebody else earlier in this thread has a reasonable explanation for why it's being offered in the first place: proof of concept.

waytogo.gif In Finnish language we have an often-used saying, ”vaihtelu virkistää” - ”variation refreshes one’s mind” (sounds better and more convincing in Finnish tongue2.gif ).

I think it’s great that GSO brought these to market. I don’t own one, but I can certainly see why someone would choose one of these over the good ol’ SCT or MCT; especially if SCTs and MCTs belong to ’been there, done that’ department for them. I would get one too, just out of curiosity if nothing else, if I had unlimited storage space and funds (although these are really competitively priced) for gear hoarding crazy.gif

I wouldn’t recommend one for a beginner, though, regardless of the price...

Edited by Axunator, 14 April 2019 - 10:26 PM.


#28 gustavo_sanchez

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Posted 14 April 2019 - 09:08 PM

By the way, what happened to the AT8CC? I can't see it on the Astronomics website anymore.

#29 macdonjh

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Posted 15 April 2019 - 07:32 AM

waytogo.gif In Finnish language we have an often-used saying, ”vaihtelu virkistää” - ”variation refreshes one’s mind” (sounds better and more convincing in Finnish tongue2.gif ).

I wouldn’t recommend one for a beginner, though, regardless of the price...

Agreed, on both counts.  I think "variation refreshes one's mind" sounds better in Finnish to me because "I've been there, done that in English".

 

I wouldn't recommend a classical Cassegrain to a beginner, either.  I've seen too many posts here by people wanting to buy their first scopes who were nervous about collimating SCTs and Newtonians.  


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#30 terraclarke

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Posted 15 April 2019 - 08:52 AM

Oh, and with 6" of aperture, I think, "just different" explains why somebody would buy a classical Cassegrain over a Maksutov, SCT or Newtonian.  I think somebody else earlier in this thread has a reasonable explanation for why it's being offered in the first place: proof of concept.


I have ten refractors, a Newtonian, an SCT, a Mak, and a dedicated solar scope. If I break down and get one (the 6”), that would be the reason. As they used to say on Monty Python’s Flying Circus: “and now for some completely different” . It’s not a bad idea actually. Trying and doing different things is what keeps life interesting!
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#31 macdonjh

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Posted 15 April 2019 - 01:13 PM

I have ten refractors, a Newtonian, an SCT, a Mak, and a dedicated solar scope. If I break down and get one (the 6”), that would be the reason. As they used to say on Monty Python’s Flying Circus: “and now for some completely different” . It’s not a bad idea actually. Trying and doing different things is what keeps life interesting!

If you do get an AT6CC, please post your impressions about the differences between it and your SCT and Mak.  That would be interesting.


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#32 terraclarke

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Posted 15 April 2019 - 02:53 PM

If you do get an AT6CC, please post your impressions about the differences between it and your SCT and Mak.  That would be interesting.


My Mak is a 3.5” Questar and my SCT is a 1977 orange tube C8 so it would fit right in the middle, alongside my 6” F4.5 ATM Newtonian.
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#33 Thandal

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Posted 17 April 2019 - 10:21 PM

Well, I just ordered the Orion CC6 f/12 OTA.  (Yeah, not shipping until the end of April...)

 

Since my observing is strictly visual, (mostly planetary and lunar) and portability (and budget!) were definitely important factors, I had almost convinced myself to get their 150mm f/12 Mak-Cass OTA when I got the email about the CC.

 

Did some research, and the differences (for me) boiled down to these:

 

Pros of the Orion Classic Cassegrain vs. (same size) Orion Mak-Cass

No front corrector plate, so no (or very little chance of) dewing -- Summers are very humid here

Open tube -- much faster thermal equilibrium

Mirrors fixed in place -- no (chance of) mirror flop

Lower useful magnification -- 22x vs. 50x (in this case)

Dual-speed (10:1) Crayford focuser -- need all the help I can get

Potentially better light transmission -- no lens, just mirrors (but depends on the quality of their coatings!)

 

Cons of the Orion Classic Cassegrain vs. (same size) Orion Mak-Cass

Larger central obstruction -- +5% by area (in this case, so does that cancel the last point above?)

Diffraction spikes -- secondary spiders do that (but only for point sources)

Heavier -- +0.25kg (steel vs. aluminum tube in this case, and will be at my mount's rated limit)

Collimation -- may be needed (but I have lots of newt. exp.)

 

Will report first impressions after first light.

 

[EDIT: Of course now I'm in the market for a 2" diagonal and eyepieces!  lol.gif ]


Edited by Thandal, 17 April 2019 - 10:45 PM.

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#34 SeattleScott

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Posted 18 April 2019 - 12:26 AM

My insulated iOptron 6” Mak Cass;
Also no dew generally, although I haven’t done extensive testing without dew shield, and Seattle isn’t overly humid.
Closed tube- faster thermal equilibrium because you can insulate it.
Spring loaded focuser, no mirror flop.
Lowest Useful magnification - 50x, ok you got me there. How do you get 22x out of a classical Cassegrain? Does it vignette?
10:1 dual speed focuser-yeah I got that too with the stock focuser.
Light transmission-spider vanes block about 1% of incoming light, roughly the same as a meniscus lens.

So other than this apparent ability to use the CC as a 22x rich field scope or whatever, I still don’t really see what the CC offers that the iOptron Mak doesn’t, other than simply variety. But certainly curious to hear observing reports.

Scott

#35 kim.davis

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Posted 18 April 2019 - 12:49 AM

Another curiosity is the light transmission between CC and Mak. CC has quartz mirror with at least 95-96% reflectivity but they dont describe coatings.

Would like to see visual difference for planets.. would diffraction spike in CC bother?

#36 Kevin Barker

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Posted 18 April 2019 - 12:56 AM

As stated above the 8 inch GSO CC does produce very beautiful diffraction spikes on brighter stars. Would these be bothersome for planetary?? Not sure.

But I suspect the 30% CO will still deliver very nice images.

 

I did notice the 8 inch GSO did cool faster than my Intes Mak 603.


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#37 Vondragonnoggin

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Posted 18 April 2019 - 02:20 AM

My insulated iOptron 6” Mak Cass;
Also no dew generally, although I haven’t done extensive testing without dew shield, and Seattle isn’t overly humid.
Closed tube- faster thermal equilibrium because you can insulate it.
Spring loaded focuser, no mirror flop.
Lowest Useful magnification - 50x, ok you got me there. How do you get 22x out of a classical Cassegrain? Does it vignette?
10:1 dual speed focuser-yeah I got that too with the stock focuser.
Light transmission-spider vanes block about 1% of incoming light, roughly the same as a meniscus lens.

So other than this apparent ability to use the CC as a 22x rich field scope or whatever, I still don’t really see what the CC offers that the iOptron Mak doesn’t, other than simply variety. But certainly curious to hear observing reports.

Scott

Scott - do you have pictures and descriptions in a thread somewhere on the insulation for the mak? I have two of these scopes. The first I modded and the second I bought used off CN classifieds and the previous owner painted everything blue. Optically they are both identical and have very good mirrors and can exceed 50x per inch on good seeing nights, but I would be interested in insulating the blue one I have. It was only $275 in the classifieds and was a whomping good deal for how it star tests. They normally take a long time to cool unless I use my Lymax cooler on it. Would be fun to have one insulated I could take out and use immediately at higher powers.



#38 SeattleScott

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Posted 18 April 2019 - 05:55 AM

I just did the usual Reflectix thing. Bought a roll at the hardware store for $10. Bought self-adhesive Velcro for $4. Cut the Reflectix to fit around the tube, with cut outs for dovetail and finderscope. Cut it with a little overlap so I could use the Velcro to keep it on snug. Some people also insulate the dew shield or do multiple layers of insulation, possibly with different materials. But the standard recipe of a single layer of Reflectix has worked well for me. As a result a couple buddies have insulated their 8” SCTs, but I cannot get my friend with the 6” TEC to cover up that logo.

Of course don’t use the Lymax cooler with an insulated scope.

The nice thing about using Velcro is it makes it easy to take the insulation on and off. Potentially you could take it off in summer, for example.

Scott
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#39 macdonjh

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Posted 18 April 2019 - 08:13 AM

Another curiosity is the light transmission between CC and Mak. CC has quartz mirror with at least 95-96% reflectivity but they dont describe coatings.

Would like to see visual difference for planets.. would diffraction spike in CC bother?

Diffraction spikes don't bother me, on stars or planets.  I've only seen "planetary diffraction spikes" on Jupiter and they were short and faint.  I'm sure Venus produces them, too, but I don't observe Venus frequently.  I like the diffraction spikes from brught stars, but then I've never missed splitting a double star because diffraction spikes get in the way.

 

For what it's worth, I noticed the first diffraction ring produced by my 4" Maksutov when it was my main scope, but that didn't bother me, either.


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#40 SeattleScott

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Posted 18 April 2019 - 11:14 AM

Diffraction spikes are a personal thing. They certainly don’t enhance planetary viewing but many excellent planetary scopes have diffraction spikes, so they don’t automatically make a scope a poor planetary scope. Personally I normally don’t notice them but if I look for them they are definitely there. Diffraction spikes drive some other people nuts. Just depends on how well you can “tune them out.”

Scott
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#41 Vondragonnoggin

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Posted 18 April 2019 - 11:38 AM

I’m not a fan of diffraction spikes or collimation. It’s why I have refractors and a mak. Both of my iOptron mak 150’s have not needed collimation ever. Even after taking one apart and modding it. I marked the tube and corrector rim before pulling it apart. When I put it back together and lined up the mark, it tested perfect again. 7 years for that one. Two of my refractors needed collimating once each, but haven’t again. Two others have never needed collimating.

 

That said - I bought my mak after selling an AR127 refractor to a friend which had replaced my 8” dob. I wanted to try something different and was not disappointed! Trying a new scope is pretty fun and always a learning experience. 

 

I say say go for it on the Classical Cassegrain if you are looking to try something new. They look like nice scopes.


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#42 Tyson M

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Posted 18 April 2019 - 06:54 PM

I have ten refractors, a Newtonian, an SCT, a Mak, and a dedicated solar scope. If I break down and get one (the 6”), that would be the reason. As they used to say on Monty Python’s Flying Circus: “and now for some completely different” . It’s not a bad idea actually. Trying and doing different things is what keeps life interesting!

I agree!

 

Whatever gets you outside and observing the stars! 


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#43 Tyson M

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Posted 18 April 2019 - 06:57 PM

Diffraction spikes are a personal thing. They certainly don’t enhance planetary viewing but many excellent planetary scopes have diffraction spikes, so they don’t automatically make a scope a poor planetary scope. Personally I normally don’t notice them but if I look for them they are definitely there. Diffraction spikes drive some other people nuts. Just depends on how well you can “tune them out.”

Scott

100% agreed. They are barely noticeable, except on brighter stars.  Actually look aesthetically pleasing to me in my Tak newtonian at low power.

 

I know that's subjective, but you would be hard-pressed to find a single person who thinks a Mewlon is not a sharp scope, or is of poor quality.....


Edited by Tyson M, 18 April 2019 - 06:58 PM.


#44 memento

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Posted 19 April 2019 - 02:42 AM

I just discovered these new scopes on the Teleskop Express website and then run a forum search to find this thread.

 

I currently use a 90mm refractor and a C5. Interested in a new toy, I thought about getting a 4" refractor – most of my observing actually is the Moon and planets. However what I like about the C5 over a 3.5" or 4" refractor is that, at any given magnification, it gives brighter views with a bigger exit pupil. Much easier for my eyes, just a more comfortable viewing experience.

 

So a 6" Cassegrain sounds like an interesting idea actually. The 8" would be too heavy for my mount. I could just go for a C8 as it is very light-weight, but they have cooling and dew issues. I'm not the greatest fan of modifying scopes, I like if it works well out of the box. And yes, I've had an 8" SCT already, so that's really "been there and done that" territory.

 

I am not sure if the spikes on planets would drive me nuts though. A pity that they did not design curved spider veins. But I don't have any personal experience with this.

 

I do like that it's an f/12, as this means that fairly long f/l eyepieces will be useable for high magnifications. I would have even preferred if they made it an f/15 or something, actually.



#45 ScottW

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Posted 19 April 2019 - 06:03 AM

Weight!

 

My mount is rated for 13lbs.  The CC is at this and I think the 6" Ioptron is around 22Ibs.

 

Scott



#46 Vondragonnoggin

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Posted 19 April 2019 - 06:24 AM

Weight!

 

My mount is rated for 13lbs.  The CC is at this and I think the 6" Ioptron is around 22Ibs.

 

Scott

6” iOptron is 14lbs



#47 ScottW

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Posted 19 April 2019 - 06:55 AM

I just checked the Ioptron site and it listed it at 22lbs.  Strange.

 

Scott  



#48 Vondragonnoggin

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Posted 19 April 2019 - 07:12 AM


I just checked the Ioptron site and it listed it at 22lbs.  Strange.

 

Scott  

Shipping weight.

 

I have an AT152 v.1 refractor that the OTA is 24lbs - the iOptron isn’t even close.

 

OTA weight: 13.4 pounds - https://www.bhphotov...ft=BI:514&smp=Y


Edited by Vondragonnoggin, 19 April 2019 - 07:15 AM.


#49 memento

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Posted 19 April 2019 - 07:13 AM

FWIW the German astroshop.de website lists the iOptron at 6 kg and teleskop-express.de the 6“ Cass at 5.4 kg. I would have thought that the Mak corrector would cause a bigger difference. But then you never really know how what’s included in these quotes (rings, bar, etc.)

#50 SeattleScott

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Posted 19 April 2019 - 01:36 PM

The classical Cassegrain has a heavy steel tube apparently instead of aluminum.

The classical Cassegrain will absolutely have cooling issues. A 4” refractor or an insulated Mak/SCT, not so much. The classical Cassegrain will cool faster than a non-insulated Mak/SCT. Keep in mind it cost me $14 and half an hour with a pair of scissors to insulate my Mak. Any modification that doesn’t require a screwdriver isn’t much of a modification in my book.

Note the CC6 has baffles. Read reports about Mewlons and see how that wreaks havoc on cooling time. Have to leave the tube pointed straight up for an hour or so to let the heat escape the baffles. And hope bats and birds don’t dive bomb the mirror. You really aren’t gaining a significant advantage in cooling time with a CC over a Mak/SCT, and you lose the ability to eliminate cooling time by insulating. Just saying. Not saying the CC is a bad scope. But just don’t buy it for fast cool down times.

Scott

Edited by SeattleScott, 19 April 2019 - 03:51 PM.

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