New Vixen VMC260 open tube cassegrain OTA?

Robert_T · #1 28-08-2007, 12:44 PM

Hi All,

Well I dissappear for months and then turn up with dumb questions...

I just saw this OTA advertised in the latest S&T, had a quick search here but couldn't find any related threads - apologies if I've missed them and am rehashing this.

Of course my eye's lit up and wondered whether this might be a substitute for a Mewlon 250 at nearly half the price. It has a respectable F ration at 11.5 for planetary imaging, but wondered if the correction lenses would ruin it for this.

Anyone have one or and opinion on this for planetary imaging?

cheers,

Rob

iceman (Mike) · #2 28-08-2007, 12:51 PM

Hey Rob, nice to see you back!

Not been doing any imaging lately? You missed the whole Jupiter season!

Why don't you forget these Cat's for planetary imaging and get a big newt

Robert_T · #3 28-08-2007, 01:32 PM

Quote:

Originally Posted by iceman

Hey Rob, nice to see you back!

Not been doing any imaging lately? You missed the whole Jupiter season!

Why don't you forget these Cat's for planetary imaging and get a big newt

Hey Mike, yeh, it's been a long slack period. I don't know why, but I just couldn't get motivated with Joop... I don't want to let Mars slip by though

The images you guys get with Newt's are amazing. Reckon I'm just too damn lazy though for the size of the things... I spent most of my formative astro years coveting Cats but couldn't afford them and now I can I don't want to give them up.

cheers,

Rob

ausastronomer (John Bambury) · #4 28-08-2007, 08:26 PM

Hi Robert,

These are sinilar to a mak cass but use a design known as Klevtsov. Where a conventional Mak Cass uses a Maksutov corrector at the front of the tube, the Klevtsov uses a mangin lens placed in front of the secondary mirror to correct for spherical aberration. These are similar to the TAL Cassegrains. They are quite a good scope for planetary imaging but they are not a Mewlon.

Cheers
John B

Dennis · #5 28-08-2007, 08:49 PM

Hi Robert

I have an old VC200L which is the Vixen 200mm f9 VISAC that uses a built in three element corrector located in the baffle near the eyepiece end.

It is a very nice ‘scope (or was until fungus got onto the primary and corrector) but it falls some way short of the Mewlon 180 in terms of star testing and contrast.

Cheers

Dennis

Alchemy (Clive) · #6 28-08-2007, 09:28 PM

i have still got a vc200l it is not a great planetary scope, to large a central obstruction. i presume the central obstruction is similar 40% ish, the vc200 strength is its flat field at normal lenggth.. though suprisingly add a reducer and flared stars at edges, i went the 12inch newt and 4x powermate.. it blew the vc200 away....

Starkler (Geoff) · #7 28-08-2007, 10:22 PM

Quote:

Originally Posted by Alchemy

i have still got a vc200l it is not a great planetary scope, to large a central obstruction. .

And also very thick molded spider vanes.

Terry B · #8 28-08-2007, 10:26 PM

Here is a review http://www.astromart.com/articles/ar...article_id=339

Dennis · #9 28-08-2007, 10:26 PM

Quote:

Originally Posted by Starkler

And also very thick molded spider vanes.

From memory, the VC200L vanes are approx 6mm wide. That is, the side facing the incoming light!

Cheers

Dennis

Robert_T · #10 29-08-2007, 08:12 AM

thanks guys, did some further googling myself and it does appear to be a less than ideal planetary scope...optimised for edge of field correction which isn,t really needed for planetary. And Dennis is there any bit of astrokit you don't have stashed away! ;-)