Autofocusser + ASI1600, focus slipping

[Lee_P]

Hi SGL Hivemind,

I'm using a SkyWatcher Auto Focuser (https://www.firstlightoptics.com/skywatcher-focusers/skywatcher-auto-focuser.html) on my 80ED, and an ASI1600MM-C camera + filter wheel. When imaging objects nearly overhead, I've noticed that the focus slips. I think this is because the weight of the camera is too much for the focusser. Does anyone else have experience of this? Is there something that can be done to help?

Thanks,

 - Lee

[DougM43]

Have you tried locking the focus lock screw? ( underneath the scope between the focus wheels)

[Lee_P]

I think so, but maybe I should try tightening it up. Presumably the autofocusser will still be able to move?

[DougM43]

Not once you've tightened the lock screw I don't think.

[Lee_P]

That's a pickle then, because surely there's not much point in having an autofocusser if it can't actually move? Maybe the lock screw needs to be tightened a bit, but not so much that it stops the autofocusser from doing its thing..?

[Lonestar70]

1 hour ago, Lee_P said:

Hi SGL Hivemind,

I'm using a SkyWatcher Auto Focuser (https://www.firstlightoptics.com/skywatcher-focusers/skywatcher-auto-focuser.html) on my 80ED, and an ASI1600MM-C camera + filter wheel. When imaging objects nearly overhead, I've noticed that the focus slips. I think this is because the weight of the camera is too much for the focusser. Does anyone else have experience of this? Is there something that can be done to help?

Thanks,

 - Lee

Hi Lee,

You need to increase the tension on the focuser drive shaft.

Look underneath and you will see 3 small grubscrews in a line along the centre of the focuser... the centre one adjusts the tension so tighten it in small increments until the slipping stops.

Make sure the lock screw is undone before making these adjustments.

Don't touch the 2 outer grubscrews as they are for adjusting the pressure plate tilt and should not need any attention.

I had to do this on my ED80 and I have a heavy DSLR camera and a field flattener/focal reducer hanging on mine with no slippage regardless of scope orientation.

I use a home built stepper motor focuser driving mine, however, the skywatcher autofocuser unit will be more than capable once you get the tension sorted out.

I hope this helps.

Clear skies and good luck.

Sandy.

[Lee_P]

On 1/7/2018 at 00:07, Lonestar70 said:

Hi Lee,

You need to increase the tension on the focuser drive shaft.

Look underneath and you will see 3 small grubscrews in a line along the centre of the focuser... the centre one adjusts the tension so tighten it in small increments until the slipping stops.

Make sure the lock screw is undone before making these adjustments.

Don't touch the 2 outer grubscrews as they are for adjusting the pressure plate tilt and should not need any attention.

I had to do this on my ED80 and I have a heavy DSLR camera and a field flattener/focal reducer hanging on mine with no slippage regardless of scope orientation.

I use a home built stepper motor focuser driving mine, however, the skywatcher autofocuser unit will be more than capable once you get the tension sorted out.

I hope this helps.

Clear skies and good luck.

Sandy.

This sounds perfect, thanks! One quick question for clarification, which one is the lock screw?

[Lonestar70]

Hi Lee,

The locking screw is the larger knurled silver thumbscrew so be sure this is slackened off before any adjustments are made.

Keep Happy

Sandy.