GSO f/12 Classical Cassegrain

[Marke (Mark)]

Dont know if these have been mentioned already ? but another offering from GSO possibly coming here soon .
https://www.astronomics.com/astro-te...scopes_c2.aspx

[doug mc]

The most versatile scope I had in the past was a C8. Just loved the ergonomics. Unfortunately where I live, dewing up of the corrector was a pain. I went back to a newt. Will be keeping an eye out for one of these.

[casstony]

I worry about the difficulty of collimating these; I guess it will be similar to the GSO RC. Mirrors and focuser have to be squared up on the same optical axis and the distance between the mirrors has to be correct.

Have people found a reliable method for collimating the RC's?


On another note, GSO no longer provides dielectric coatings on their RC mirrors according to Astronomics. I had visions of putting the garden hose up the tube to wash the mirrors but I guess not

[Marke (Mark)]

My understanding with these scopes it the primary is fixed and collimating is with secondary only and at f12 it shouldnt be too touchy . Heard they are working on a 10" and 12" also. Makes a nice planetary scope .

[Wavytone]

A cheap and nasty way to undercut SCT prices - and the target market is noobs who don’t know what happens to exposed mirrors after a couple of years.

The whole point of a classical cassegrain is to be a planet killer, primarily for visual, which implies a CO well under 30% and ideally 24%. Yet they’ve crippled these with a big CO, 33%, and with an open tube the coatings will have to be cleaned and recoated from time to time.

A cheap SCT is a better buy - the OTA is closed by the corrector and the mirror coatings will last far longer.

And with similar CO to SCTs I’d expect the image quality to be much the same.

[Marke (Mark)]

Originally Posted by Wavytone

Large central obstruction though. Pity about that.

The whole point of a classical cassegrain is to be a planet killer primarily for visual, yet they cripple it with a big secondary.

Yep thats the issue I think they are using the same secondary as the RC scopes and a slightly different primary or maybe the other way around .
Still be interesting to see how they go as they are sure to cheap.

[doug mc]

What's to complain about, a casegrain that doesn't dew up at GSO prices ( at least not with a dew shield). There is a long thread on CN. on these scopes. Early days yet though.

[billdan (Bill)]

From the thread on CN, I believe the primary is F4, so you could modify the top end and turn it into a newt for a wider field of view.

[Marke (Mark)]

Originally Posted by billdan

From the thread on CN, I believe the primary is F4, so you could modify the top end and turn it into a newt for a wider field of view.

You can already buy an f4 GSO newt tho

[croweater (Richard)]

You could have 2 interchangable secondary mirrors like the old Parks HIT series and have both worlds. Cassagrain or newt. Cheers Richard

[Marke (Mark)]

Originally Posted by croweater

You could have 2 interchangable secondary mirrors like the old Parks HIT series and have both worlds. Cassagrain or newt. Cheers Richard

Yes except for the big hole in the primary

[croweater (Richard)]

Originally Posted by Marke

Yes except for the big hole in the primary

Wont the secondary block the hole

[Marke (Mark)]

Originally Posted by croweater

Wont the secondary block the hole

Nope smaller secondary then you have the issue of collimating without a centre spot on the primary . Simpler to just get a second f4

[croweater (Richard)]

Originally Posted by Marke

Nope smaller secondary then you have the issue of collimating without a centre spot on the primary . Simpler to just get a second f4

I think you're right. It would be a headache. Cheers Richard.

[doug mc]

Just put a centre dot on the focusor dust cap maybe.

[glend (Glen)]

Aren't these GSO scopes very similar,(or slower copies) of the rather well regarded Vixen VC200L?

[LewisM]

More or less Glen, they are. The VC200L is exceptionally capable (apart from the darned massive spider vanes - but that does ensure basically NEVER recollimating. Thinning the vanes is done quite regularly - I had mine reduced to 1.5mm).

I note the GSO's have many tube baffles - a great thing. I was GOING to do the same to my most recent VC200L before I sold it. Contrast on these can be a bit muff without doing so.