Astro Mod help Shims!!

[yelsac]

Hi

Ok over the past few months through a process of elimination its seems I have a sensor tilt on my astro modded 450d which is causing focus problems for astro use.

After some investigating & discussion with the chap who did the mod two of the three shims (I'm assuming from the Gary Honis mod page there are 3 shims) fell out during the mod leaving maybe only 1 shim left, so my question is if I opened it up & took the last shim out hence hopefully stopping the sensor tilt would that sort the focus problem or would it make it worse?

by the way I don't want to use the camera for daytime use only astro so don't need the autofocus.

thanks

[SkyBound]

The shims are there to retain autofocus with a lens, if a couple have come loose form one side , then it's possible that is your issue, if you remove the other it may well SORT the problem, but if the sensor is loose enough for the shims to fall ou, then there is another problem that need addressing.... it will need securing properly.

but if you don't need autofocus then there is no need to shim the sensor.

[yelsac]

1 hour ago, SkyBound said:

The shims are there to retain autofocus with a lens, if a couple have come loose form one side , then it's possible that is your issue, if you remove the other it may well SORT the problem, but if the sensor is loose enough for the shims to fall ou, then there is another problem that need addressing.... it will need securing properly.

but if you don't need autofocus then there is no need to shim the sensor.

I think the shims came out while the camera was being modded & they forgot to put them back in or something rather than them falling out so I assume the sensor is securely screwed down.

I just wanted to know if there would be other focus problems if I removed the remaining shim because it would obviously move the sensor closer to the front of the camera

[SkyBound]

Well normally during the Astro mod, the person doing the mod will shim the sensor as a matter of course, for autofocus reasons, as there is a filter being removed, it alters the focus point, hence the shims to take place of the space left by the removed filter...

so they were not there before the mod, as you thought...

[Dr_Ju_ju]

You don't say who modded your camera, but I've had two of mine done by Juan @ http://cheapastrophotography.vpweb.co.uk/ He may be able to fix it for you...

[yelsac]

29 minutes ago, SkyBound said:

Well normally during the Astro mod, the person doing the mod will shim the sensor as a matter of course, for autofocus reasons, as there is a filter being removed, it alters the focus point, hence the shims to take place of the space left by the removed filter...

so they were not there before the mod, as you thought...

It was only a diy mod by a user on here who then sold it to me & I think he didn't intend to leave out the two shims but as the camera was to be used only for astro & hence autofocus was not needed thought there wouldn't be a problem.

I just really wanted to find out if I'd have further problems gaining focus through my scope if I removed the third shim myself to alleviate the apparent sensor tilt (basically would it be worth taking it all apart in the hope my original focus problem would be sorted)

[michael8554]

If you remove the remaining shim there's a good chance you will get a flat field again.

And as LiveView focus doesn't get affected by the removal of the filter in the mod I assume the main image sensor and the Live View sensor will still be congruent.

Michael

[yelsac]

On 12/12/2016 at 23:49, michael8554 said:

If you remove the remaining shim there's a good chance you will get a flat field again.

And as LiveView focus doesn't get affected by the removal of the filter in the mod I assume the main image sensor and the Live View sensor will still be congruent.

Michael

On 12/12/2016 at 10:14, SkyBound said:

The shims are there to retain autofocus with a lens, if a couple have come loose form one side , then it's possible that is your issue, if you remove the other it may well SORT the problem, but if the sensor is loose enough for the shims to fall ou, then there is another problem that need addressing.... it will need securing properly.

but if you don't need autofocus then there is no need to shim the sensor.

Thanks for all your advice

Took the camera apart & found four shims when there should have been 6 (2 in three places) removed the remaining four (as autofocus was not needed) & low & behold the tilt is gone & focus looks good.

So chuffed Thanks to all for your helpful comments

[michael8554]

Glad you got it sorted, and we've all learned something into the bargain.

Michael