Criterion RV-6 with drive on AM
Posted 15 May 2007 - 10:24 PM
I wonder if my Vixen SP mount could handle this tube?
Regards and clear skies,
Posted 16 May 2007 - 07:27 AM
Posted 16 May 2007 - 12:53 PM
I have an RV-6 and I imagine an SP mount could handle the OTA, it is quite light, about 8 pounds without the rings.
However $800 is way, way over priced IMHO. I have purchased two of complete RV-6's in the past couple of years locally. Both were around $100. On AM, I see them in the $300 range. Nice scopes as a vintage scope, I would expect the 6 inch F/8 Discovery to be as good optically and a bit more modern and a whole lot more reasonably priced.
Posted 16 May 2007 - 01:01 PM
One question in my mind about them :
The mirrors must be old, so surely there is some degradation of the coatings? How good are the mirrors typically in these old scopes (assuming one was well cared for), and how much would it cost to have one re-coated if necessary?
(ok, two questions!)
How good is the stock focuser in the RV-6?
(ok, one more!)
How big is the secondary?
Regards and clear skies,
Posted 16 May 2007 - 03:03 PM
They were pretty good.
The stock focuser is useable if you are not picky, definitely not something to write home about.
I think there were a variety of secondary sizes, mine I think is around 22% an nice place to be.
Posted 16 May 2007 - 03:21 PM
I think I am going to keep an eye out for a cheap one and pick it up to experiment with.
Where does one send the mirrors for a recoat?
Maybe I could piggyback my 4" achro on it!
Regards and clear skies,
Posted 16 May 2007 - 04:02 PM
I've had a bunch of RV6s and RV8s. Some of them have really, really good mirrors in them. I kept one for years that was absolutely the best one I'd seen. I sold it to one of my fellow club members last year and he loves it. I would recommend that if you run across one reasonably that they're worth picking up and restoring if you have the time to devote to it. Other than recoating the mirrors, the only other thing that usually needs doing is re-blackening or flocking the inside of the OTA to increase contrast.
I would replace the stock focuser. It's okay, but it's not great. My friend used a JMI mini-DX on his, which worked very well. Lower profile, plenty of travel.
I'm not sure I'd put it on an SP mount (moment arm, not weight) but it would work okay on one. I *definitely* wouldn't piggyback your 100/600 on it on that mount. I'd use something beefier...
Posted 16 May 2007 - 04:07 PM
The RV-6's are spherical mirrors that deliver superior performance. At f/8 its not imperative for a six inch to be a parabaloid. Most with original coating will need recoating. My Super Polaris mount easily handles it but the tube impacts the legs at high viewing angles. The focuser is primitive but usable.
Posted 16 May 2007 - 04:18 PM
$800 did seem a bit steep, given the much lower prices I have seen for these scopes.
I thought it was high too...but it has some interesting accessories like the original inverter and the factory add-on dec control. Now, the deal breaker for me is tacking on the shipping. In reality, a person could pay over $1,000. $800 including shipping is probably what it would currently sell for.
I have a 3" mirror from the late 60's/early 70's that in all likelihood came out of the same factory as this Criterion's (Universal Precision). It is virtually unblemished. With proper storage its very possible to have quality coatings last this long.
Posted 16 May 2007 - 04:26 PM
My 1961 original was recoated sometime in the early 80's and the coatings are fine. I bought a 70's vintage RV6 with original coatings and it very much needs a new coating. Until one sees the mirror you'll not know if it's needed. However coatings are not expensive for a 6 inch.
Posted 16 May 2007 - 04:38 PM
Never heard that one before.... ???
Posted 16 May 2007 - 04:40 PM
Posted 16 May 2007 - 04:42 PM
The 1/4 wave 'Rayleigh criterion' is met at f8.2 with a 6" mirror. Parabolizing does help. f/10 or f/11 is in actuality where spherical mirrors begin to excel.
Posted 16 May 2007 - 05:31 PM
Posted 16 May 2007 - 06:03 PM
I bought another RV6 a few years ago and took it to the St. Petersberg Fl mirror making group and had it tested. These guys are experts concerning mirror grinding, figuring, and testing. They have very good test equipment and software. The mirror showed no significant flaws and was spherical. The tester said all the RV6 mirrors he has tested were spherical. He also added that 6 inch at f/8 is very forgiving and will provide excellent results spherical...Don't try that with a shorter focal ratio or a larger mirror. Me thinks one reason the RV6 has such a reputation for fine optics is that the sphere is easy to produce with consistancy and at f/8 the results are impressive. Also no doubt helped to keep the cost down.
Posted 16 May 2007 - 06:57 PM
A Refractor Guy? Not I. I have a very multicultural scope collection. I luv all scopes.
Keith (Except the big squat orange ones with those black hockey pucks on the front...begins with a 'C'...Celestial, or something like that. )
Posted 16 May 2007 - 07:05 PM
Posted 16 May 2007 - 07:22 PM
Posted 16 May 2007 - 07:31 PM
I've written this before but its appropriate for this discussion. The absolute best views of Jupiter I've ever had have been with my RV6. They have been superior to my Custom Delux 10 inch F/6 Cave. My humble RV6 sat in a closet for about 2 decades as I had larger and "better" scopes. A neighbor came by while I was observing with my 1989 AP 6 inch f/8 Refractor...a semi APO with a beautiful triplet oil spaced lens.
He told me he had an RV6 scope and asked me to help him get it into shape. I did and a few days later he set up next to my AP and we compared views of Jupiter...Wow!! I was shocked, the RV6 was its equal or in truth better. Now this is not to diss the AP triplet but to express the quality of RV6 optics. Long story short, I sold the AP and restored my 1961 RV6. I'm still amazed with its planetary and double star performance. Like I've written the focuser is marginal,same for the mount, however optically its performance is first class.
Posted 16 May 2007 - 07:34 PM
I just got my Criterion and didn't use it before sending the mirror out. I suspect it will be much better than the Meade.