Focuser problems

[sologuitarist61]

Hi everyone, I would be grateful for some advice.

I have a SW 120 Star Travel and when I use it with my Baader zoom, or camera (or both if I am using it for eye projection) I have trouble with slippage of the rack and pinion focuser when the object is high in the sky. I get the object in focus, take the picture, and then find it has slipped out of focus. The tensioner screw doesn't seem to help much either as focus has gone by the time you tighten it

Now a friend of mine has a the SkyWatcher dual speed electric focuser and says that holds focus quite steady; whilst I was thinking along the lines of the Skywatcher Crayfors focuser as an upgrade. What would be best to get taking into consideration the weight that may be attached to it.

Any thought?

[Stephen]

I wouldn't consider anything less than a Steeltrack with that load on it

[sologuitarist61]

The problem is, can you retro fit that to my scope? From what I have read so far, it isn't a direct replacement.

[Stephen]

From memory (you need to check this) the ST120 has the same size flange (96mm) as the ED80 .... and the Steeltrack (with the adaptor that FLO include with it) fits the ED80.

[sologuitarist61]

Thanks Stephen will give it a look.

[umadog]

If you're after a cheap solution that won't require replacing your focuser, then you could use an elastic strap to support the weight of the eyepiece. Tie one end to a fixed position on your scope and slip the other over the setscrew for holding the eyepiece in place.

[sologuitarist61]

I like it!!!! and it might just do in the short term!

[John]

You can increase the tension by i) adjusting the two small hex screws on the top of the focuser, one either side of the large tension screw and ii) by adjusting the 4 screws that hold the pinion onto the rack on the underside of the focuser. You will need to experiment to see how much adjustment is needed to get the desired tension. I've used a similar R&P focuser to hold a 2" diagonal plus a 31mm Nagler eyepiece in the past - that's around 1.5kg of weight !.

[sologuitarist61]

You can increase the tension by i) adjusting the two small hex screws on the top of the focuser, one either side of the large tension screw and ii) by adjusting the 4 screws that hold the pinion onto the rack on the underside of the focuser. You will need to experiment to see how much adjustment is needed to get the desired tension. I've used a similar R&P focuser to hold a 2" diagonal plus a 31mm Nagler eyepiece in the past - that's around 1.5kg of weight !.

Didn't know that, will have a look in the morning when I have more time and give it a go - at the moment the rack and pinion is quite loose. Thanks for the tip

[knobby]

This might be of interest

http://www.astronomyshed.co.uk/forum/viewtopic.php?f=42&t=580&start=0

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