[darrellx (Darrell)]

Hi All

I have just come inside after a relatively enjoyable night of viewing. After several weeks of poor viewing weather, the Gold Coast has finally had a night of clear sky.

I have a few points I would like to clarify (in my own mind) about off-axis guiders. Tonight is the first night that I have had a chance to use mine since I purchased it, and I think I have made a few incorrect assumptions about them. So I would like to clear them up.

First, the equipment. I have a Megrez90, and have it on an EQ5 mount. The order of the equipment was: scope - oag - field flattener(vIII) - EOS400. I couldn't put the field flattener before the oag (closer to the scope) because they wouldn't fit together that way. I suspect I would need another adapter.

So, Assumption #1 - the view through the "off-axis" recepticle would be the same as that through the "on-axis" view (I am not sure if they are the right terms, but I am sure you will figure it out). Well it doesn't appear to be. The field of view through the off-axis part seems to be smaller, not just shrunk overall.

Assumption #2 - the views through both recepticles would be exactly of the same part of the sky. They seemed to be different. For example, I centred the view in the EOS on a few significant stars expecting to see the same star in the off-axis view, Sirius, then Acrux, then Alpha Cent. In each of these, the main star had to move entirely out of the field of view on-axis, to get it into view in the off-axis. I did find the two little adjustment screws at the base of the off-axis holder, but the limited adjustment they offer didn't allow enough movement to get the view the same.

Assumption #3 - if the view through on-axis was in focus, then the view through the off-axis would also be in focus. I thought the oag would have been made in such a way that the focal length of each recepticle was the same. Well, the focus was way way off for each view. So I figure that I could use a barlows in the off-axis view to help get it into focus. It didn't work. I used a 3x and yes it did bring them closer, but not enough.

Thats it. I suppose my question is this; were my first assumptions really incorrect and I have now learnt something from the experience or does it appear that I may be mis-using the equipment in some way and I need to get back out there and try again?

The focus issue in #3 is the most perplexing of the three. I would like to hear any suggestions to correct this.

Thanks
Darrell