cwchan

There are two versions of DCA for Swarovski ATM/STM telescope, namely DCA-fixed (model number 49306) and DCA-zoom( model number 49206). The former is for its 20X, 30X & 45X eyepieces, while the latter is for the zoom  eyepieces. However, with the popularity of using the zoom eyepieces in the telescope and less people using the fixed eyepiece, Swarovski stopped the production of DCA-fixed a few years ago.

However, if you use the scope for taking photos and you ask for the better image quality, the 30x eyepiece is still the best among the eyepieces that Swarovski produced. Unfortunately, if you fit the DCA-zoom to a 30X eyepiece, there were a lot of problems. The most obvious is that the upper half of the DCA will not slide all the way down to the proper locking position on the bottom half of the DCA. The end result is that the eyepiece ocular opening is not on the axis with the opening of the upper half of the DCA. To solve these problems, our friend Chan C-fu modified the upper half of the DCA by replacing it with a longer tube so that the DCA upper half can now slide all the way down to the locking position . The whole system is now working properly on the 30X eyepiece as the old DCA-fixed system.

Anyone who need this modified tube for their DCA-zoom , please PM me, I understand Chan C-fu still has four units in stock. Of course, you have to pay for it.

dick

A nice DCA tube, it helps a lot.

cwchan

Quote:

Original posted by dick at 13/07/2011 12:49
A nice DCA tube, it helps a lot.

You are the most suitable one to give the comment since you are the first user to try it out.

lwingkay

I have sold the DCA(Zoom). When I used it, I used two adaptal rings* to lengthen it. I usually used a Nikon P5100 along with the DCA.

With the measure taken, I was able to get vignet free images for the zoom range from 28mm to the telephotographic end of this superb camera.

The way I controlled the length of the depth of the two adaptal rings was to incorporate the thread that held the glass of a lens filter in position into screw furrows of one of the adaptal rings. If I want to shorten the depth of the two adaptal rings, I screw in; if otherwise, then I screw out.

The ring-like thread will be held in position when you screw in to have the adaptal ring pressing against the thread. The shortcoming of such a makeshift measure is that there is only a short distance for the thread to move in and out, so the depth you can play around with is pretty limited.

But, in digiscoping, a few millimeters of manuvering distance is often good enough to have the vignetting problem resolved significantly.

I have seen Master Chan's product. It is a very good device to resolve the problems arising from the short height of the DCA(Zoom). Thanks Chak Wing for sharing what he has designed with us here.

Regards,
Peter

Postscripts
*  Here, the adaptal ring refers to the one that either steps up or steps down a filter to make it screwable onto a lens.  An example is the one that converts a 62mm filter to be a 52mm.

[ Last edited by lwingkay at 14/07/2011 16:20 ]

OhioBirding2012

I am very interested in this DCA modification.  If anyone can provide more information on how to obtain one or if one is still available - please contact me at:   glencrippen@hotmail.com


THANKS!!

Glen