Focus locking screw

[LeaWoo]

Hi All,

We have a Skywatcher Mercury 707az telescope and hole for the focus locking screw seems to be out of line. The seller said they would send a video link but haven't as of yet.

I am hoping to get some opinions, I have attached a photo.

Have we done something wrong or is it faulty? Also, would this affect the focus in any way? The outer part of the frame won't focus properly no matter how we adapt it.

[knobby]

Not too sure from the picture but a focus lock screw shouldn't stop you from focusing, it's more likely that you have an extension price or maybe the diagonal not fitted.

[LeaWoo]

Hi thank you for replying. 

Do you mean extension piece?

The diagonal is definitely fitted and then we've attached the 10mm, 25mm and a x2 barlow and all resulting the same. 

I have attached another photo of the locking screw hole, it doesn't seem to be aligned with the hole below.

[DaveL59]

being a little off-centre shouldn't affect its function nor ability to focus, would just be manufacturing tolerances most likely. Not even sure why it needs to align to the hole below but I don't have the destructions for that scope. The focus lock should simply clamp the drawtube so it doesn't move once you have achieved focus, useful if using heavy eyepieces or a camera.

Have you tried to focus in daylight on something like trees or houses a few hundred metres away? You should be able to get a good focus across the field of view with both 25 and 10mm eyepieces tho 10mm will be dimmer and of course the image upside-down unless they supplied an erecting prism.

Arrangement should be:
eyepiece -> diagonal -> scope focuser

or with the barlow
eyepiece -> barlow -> diagonal -> scope focuser

That said you might be able to reach focus without the diagonal but would need to rack the focuser out a few inches more than with it.

 

Edited November 16, 2020 by DaveL59

[LeaWoo]

Thanks for your reply.

I believe it is supposed to go through the hole below to clamp the drawtube, but as it is out of line it is not locking.

We haven't had the opportunity to try during daylight now it is getting dark at 4pm. Will give it a go at the weekend and see if it makes a difference.

[DaveL59]

is that hole part of the moulding of the focuser body, or a separate plate under the bump? Will it move at all if you jiggle it with a small screwdriver for example?

[Peter Drew]

The locking screw definitely needs to go through the misaligned hole to perform its function, at the moment it would be locking on to the fixed casting.  It may be that there is a floating plate that the hole is in that can somehow be repositioned properly.  However, as pointed out, this should have no affect on the focusing assuming that the drawtube actually moves in and out whilst turning the focus knobs.      🙂

Edited November 16, 2020 by Peter Drew

[LeaWoo]

I tried that and it is solid, looks like a manufacturer fault most likely 

[Peter Drew]

That's a pity. however you shouldn't need to lock the focuser for visual use.    🙂

[LeaWoo]

I thought so to be honest, we are going to try and focus in the day light to see if there is any difference. Thanks.

[Ricochet]

When using it at night on celestial targets, remember that in order to focus the telescope you must turn the focuser knob to make the image smaller. When whatever you are looking at is at its smallest, it is properly focused.

[LeaWoo]

On 18/11/2020 at 17:56, Ricochet said:

When using it at night on celestial targets, remember that in order to focus the telescope you must turn the focuser knob to make the image smaller. When whatever you are looking at is at its smallest, it is properly focused.

Thank you, that helps.

You still can't really tell it's Mars though and maybe our hopes were too high for this scope. The hole for the focus screw is way out any way so we are going to return it and find a better quality scope.

[DaveL59]

What sort of view are you hoping for, as Mars will look small in most scopes as will the other planets. You might be able to discern some detail in a larger aperture longer focal length scope but it'd still be a small disc. If your main interest is planets then perhaps something like a MAK like the SW127 would be a better bet tho it'll cost more.