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Power Wheel Barlow.

Posted by Mike Jones   04/29/2006 07:00AM

Power Wheel Barlow.
I have had ample opportunity now to give my new Powerwheel a go around the block in my ED80 and 6" Newt. I must admit that I seem to gravitate towards my refractor for most viewing so you will notice that the Newt is only mentioned in passing.

When I purchased the Powerwheel I originally got the 1.5x, 2x, and 3x configuration which after trying it out was nice, but didn't seem to be the best swing in magnification for my small refractor. 1.5x didn't seem much different than x1. I immediately sent for an additional element that would allow this to be configured for 1.9x, 2.6x and 3.3x which has turned out to be an extremely versatile combination. I say this because this magnification works extremely well with single eyepieces and the swing is quite dramatic between powers. You really can tell you have moved up in magnification. But these 3 magnifications also accomodate the use of my Burgess bino in the same scope. I was using a 1.25" diagonal in my Orion and I found that I could easily go from single eye viewing to binoviewing without even having to remove the powerwheel and the magnifications stayed extremely usable. I should say at least two of the magnifications did. The highest one seemed to be too overpowered for my ED80 which is understandable because of the additional distance the binoviewer introduces. First I will start with the single eyepiece setup and then move on later to the binoviewer uses. I will mention that the powers of the PW are marked with glow in the dark dots. The documentation explains that this method is easier to use since the wheels are configurable and the values can change. So marking them x2 and the like won't work. There are 1,2 and 3 dot markings consecutively around the wheel. One dot being the lowest power setting. This setup actually works very well in the dark since the dots are easy to see in any light conditions.

I used my Burgess 20mm and a 10mm plossl's for all measurements for the sake of making this easy. My ED80 has a 600mm focal length. So with the Powerwheel at 1.9x is 57x. Since these eyepieces are 60 degs., this is roughly 1 deg. of sky. This looked about right on the near full moon a few nights ago. This means I could have fit 2 moons in the fov. This was a wonderful sight although very bright in a single eyepiece even for an 80mm. Unfortunately very little shadow was left on the moon so very little crater detail was seen on the moon. But very little false color was seen which is par for this scope. At 1.9x the moon was extremely sharp no matter where I panned it in the fov. This seems to indicate that the optics used in the Powerwheel are of very good quality. The optics also introduce no ghosting and there were no other optical irregularities to report.

Setting #2 or 2.6x the wheel rotates smoothly and locks positively in place snapping a considerably larger image in place. Surprisingly little focus was required for this high a jump in magnification. At this magnification I was at 78x. The moon now takes up roughly 3/4 of the fov. Detail that was too small before starts to become noticeably larger and easy to see. As before the seeing very easily handles this boost in magnification. At this point I decided to swing over to Saturn for something different. Saturn was not completely straight up in the sky, but not terribly low either. So a very decent image was seen. It is still not large enough to see some of its finer details. At 100x Saturn was just starting to take on a pleasing appearance and was large enough to start seeing detail. The Cassini was holding steady with a single eyepiece so I knew the night was decent.

Now it was time to see just how much power on this night my scope could take. So I racheted down the magnification and started with a more powerful eyepiece which was the 10mm. This started me out at 114x. The magnification once again made a noticeably larger image, but since my seeing appeared to be 8 out of 10 it was time to go up to 2.6x again for a magnification of 156x. Technically my scope should not handle much more than this. I was more than satisfied with the image scale. It was still sharp. The Cassini was obvious and some of the lower band was visible. So I figured I would try the last magnification to see what it would do to my image. Flipping up to 3.3x was 198x. This is a little bit over the 50x per inch of aperture but on something as bright as Saturn you would never know it. The image was superb and did not show noticeable breakdown. I would say that this particular range for the Powerwheel was a perfect match for my ED80.

Having tried the Powerwheel in my Newt. the range seemed to work very well. It has a focal length of 685mm's. This does not change things very much except it has slightly higher resolving power that I have really never been able to see. This is a testimony to the quality of my Orion APO.

Here is a short excerp about the Powerwheel's use with the binoviewer. Technically this optical set that came with the Powerwheel is for single eyepieces, but upon using it with my Burgess binoviewer I was surprised that I was able to get all three magnifications to easily focus with lots of room to spare in the Orion. The first setting at 1.9x was extremely useful with the 20mm eyepieces. The magnification seemed to stay the same as a single eyepiece or maybe a hair more. This magnification, I would guess, was roughly 60x. The change came with the next power up. No problem with focus, but I would guess my power at no less than 3.5x, possibly 4x. At 4x my magnification was up to 120x. This was completely useful with the Burgess binoviewer. In fact the extra magnification jump would be a plus, I would guess for some people since the 20mm's could be used for higher power viewing. The last magnification setting I am guessing from my calculations on the moon and then back to Saturn was about 6x. The extra distance the binoviewer added seem to make a much bigger difference in the higher two settings than the first setting. The first setting seemed to stay the same. At 180x I felt that I was over magnified for Saturn. As a single eyepiece this worked, but not with the binoviewer in place. This was easily fixed by going to a pair of 25mm's in this setting, which I have. The magnification was now 144x and the image had recovered enough light to be contrasty again.

The ability to use a binoviewer was not stated on the Siebert Optics' barlow page, but it is certainly an added plus. The optics that were replaced with this configuration will be sent back for a refund. So my overall price will end up being $199 in the end which I feel was certainly worth it considering the ability to easily change magnifications without disturbing my scope's setup.

To sum it up, I found the Powerwheel to be as useful as I had hoped. I found nothing specifically disappointing with it's operation or it's fit and finish. The optics seemed well coated (although I am no expert). I mainly judge this by the fact that I had no problems with ghosting or reflections. I was at first concerned about the alignment of the optics in an optical device that rotates or changes the position of the position instead of having fixed optics. I did not see anything problems that might be associated with an optic out of collimation. Looking directly through the changer without any eyepiec in place the optics in relation to the eyepiece holder. These are just a few of my observations. I did not find anything that might be a negative, but this does not mean that you won't. So although these are my observations ymmv.

Mike Jones