Telescope Reviews: Re: Dealing with RA Tracking Problems

I've stripped my ETX105 several times in an attempt to improve the pointing and tracking. The components are identical. The short version is that unless you plan to confine yourself to shallow space, you probably need to mount the optics on a new mount, and even then it will be hard work.

The drive problem arises from two places... the basic drive mechanism and the time it takes the scope to respond to guiding corrections.

The first problem is (I think) dominated by the worm wheel which is about 38mm diameter - this is way too small to achieve ~2 arcsec tracking which you need for open loop imaging. It's also possible that the gearbox introduces a lot of periodic error - but there is no mechanism for correcting this.

The second problem relates to the control bandwidth. This might be specific to my scope (or how it's set up) but I can't get the delay down to less than several seconds. This is generally not going to help correcting your drive.

A final observation might be useful - you can gain a lot against drive problems by using a focal length reducer. Depending on your chip size, reducing to f/5 _may_ be possible, and f/10 probably is. This will reduce the exposure (9x at f/5, 2x at f/10.)

Clearest
Bruce, Toronto

Modified LX200/12, FLT110, ETX105

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