How do I focus with an OAG

[Johnboy2011]

Hi,

I am planning to use a Meade OAG with a Canon 1000D, 6.3 focal reducer on a C9.25. I am guessing that to focus the guide cam I will have to move it up and down the barrell of the OAG but as it is the cheap Meade I am guessing this will only give me minimal adjustment.

Is this the correct way to focus and will I have enough adjustment?

Regards,

John

[MartinB]

Yes, this is the correct way. Different designs allow you to make the adjustment in different ways but commonly you release a set screw to allow you to move the camera up and down. Can't comment on the Meade I'm afraid but given that you are using a very popular camera your dealer ought to be able to give you this info.

[Johnboy2011]

Thanks Martin. I should have been clearer, it is a very basic Meade OAG and a QHY5. Do you think there will be enough adjustment with this to achieve focus?

Thanks,

John

[Merlin66]

You may need an extension piece in the guide port - a 1.25" x 25mm spacer?

Set it up on a distant object - focus the DSLR first then play with the QHY until you get an image. A parfocal ring can help to get that final tweak and locks in the position of the nosepiece.

[steppenwolf]

I have reviewed the cheap Meade version OAG and it has quite a high guide camera turret which I found quite useful. Adjustment is by sliding the guide camera's 1.25" nosepiece up or down the turret and securing it with the retaining bolt. If there isn't enough upwards movement, try a cheap Barlow lens with the lens removed to give you a spacer. If you can't get it down close enough to the OAG body, add a spacer at the imaging camera end.

[BlueAstra]

Set the equipment up in daylight. Focus camera on a distant object, eg pylon, using zoomed liveview if available. View the guidecam output with its software and move it up and down to focus on the same target. Note the guidecam field of view may be outside the camera fov depending on the oag orientation. That should put you close enough so you can fine tune it at night, maybe with a focussing mask.

[Johnboy2011]

Thanks. that all sounds senesible!!