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6" Newtonian Reflector made by vixen in Japan for

Started by robert garces, 10/18/2005 05:07PM
Posted 10/18/2005 05:07PM Opening Post
6" Newtonian Reflector made by vixen in Japan for celestron
Diameter=150mm Focal Length=750mm F ratio f/5
anyone have expierience with these scopes ?
just wondering how they fair, the optical quality of these OTA's ?
anyone have any astroimage examples of what this scope can do ?
I want to get something for wide field views and astrophotography,
and i have a chance to pick up one of these. but want some info before
I do.. thanks.
Posted 10/19/2005 05:08AM #1
Hi:

I can't really comment on this specific scope. However, there are some things to consider when thinking using a scope like this for widefield viewing.

Does it have a 2 inch focuser? If not then the maxiuum field of view will be 2 degrees and you will not be able to use a paracorr.

Do you have a Paracorr or are you prepared to buy one?

What sort of widefield eyepieces do you have, are they decent at F5?

Is the secondary large enough to give a well illuminated field of view at low magnifications?

Jon

Posted 10/19/2005 11:08AM #2
hi Robert

I have one of these scopes. When I bought it (new) about 15 years ago it was known as the SPC6 since it came on the Super Polaris mount.

First off, I have to say that I have had lots of great views through this scope. I do visual observing only, so I don't have any astrophotos to show you that I have taken through the scope.

There are a few things that you should know, however. The focuser is of the "sled" type and only accepts 1.25" eyepieces. It is a sliding plate that has the secondary attached to it via a wide, single stalk. To focus, this sled moves the secondary towards and away from the mirror.

The sled does tend to slip when the scope is pointed near the zenith, and this is only with an eyepiece and a barlow. It does have a tension/locking screw, which works for me, but this might be more of an issue with a camera attached.

One thing to note is that I did try to attach an SLR to it once via a T-adapter, and the camera would not reach focus. The focuser has tubes of different lengths which screw into the sled, but even with the shortest one supplied it would not reach focus.

As well, it has a huge 2" secondary. This maybe be fine for imaging, but is not so great for visual observing as far as diffraction effects and decreased aperture are concerned. And it is not an easy matter to swap in a smaller secondary due the size and design of the secondary single stalk support.

Finally, I think the main mirror is astigmatic. This is obvious during a star test. When the mirror cell is rotated, the star test image rotates with it, so it's not the diagonal. One thing I wonder about is that the problem might be with the moving secondary. The focuser is simply bolted to the tube; if it is not properly aligned the secondary will not be moving along the optical axis during focusing. One thing I'd like to try is shimming the focuser to ensure that it is moving the secondary on-axis.

Anyway, a bit long-winded but I hope this helps.

steve
Posted 10/19/2005 02:35PM #3
I've owned two 1980's black Vixen- Celestron 6" F/5's, both were very good even at higher powers! They come with a 1.25" focuser.


Chas
Posted 10/20/2005 05:09AM #4
thanks guys, very helpful, I was gonna get it for imaging
but decided not to deal with the flaws of this scope
i'll have to spend more on something a bit slower but i think i'll be happier.

robert