TS 9mm OAG

[PaulB]

I bought a TS 9mm OAG to use with my Orion Optics 200-800 F4.

I tired using this for the first time last night, and spent most of my time out side trying to figure out why, I couldn't see any stars with my QHY5 guide camera.

The QHY is connected to a turret, where there is a tiny prism below it, that intercepts part of the light path from the secondary mirror

The main imaging camera, a Atik 16ic focuses OK. And I have it attached to a BS Astro filter wheel which is then attached to my OAG.

My question.

Doe's anybody here use a similar TS OAG or another OAG with a short focal length Newtonian.

And how do you find the correct focus point with you're guide camera with an Off Axis Guider.

[Merlin66]

Set up the scope during the day and focus on a recognisable distant object; centre and focus the imaging camera then find the section of the image where the pick off lies - move the scope if necessary to pick up a recognisable part of the object to confirm the offset and then independently focus the guide camera.

Once this is done - its done. You don't need to reset the distances unless you change the cameras.

There was a great thread last year? on OAG (Blue Astra??) well worth finding and reading.

Edit: found it!

http://stargazerslounge.com/equipment-discussion/90916-orion-oag-first-light.html

[PaulB]

Thanks Merlin,

My problem is- I don't have anything distant to focus on. I have a garden, that is largely covered with tree's. These trees prevent me from focusing on any distant object.

At the moment I am not impressed with this OAG. The prism is only secured with a tiny cap head screw and when I opened the OAG last week-end. The prism fell out!

Why TS didn't glue this I don't know. Now I have some tiny, but noticeable blemishes on the surface of the prism.

I think the simplest answer is to use our Moon, to find the focus balance.

[PaulB]

Since writing this. I have a replacement Turret complete with Prism on it's way to me.

When it arrives.

I will measure the distances from the main camera CCD chip, to the prism. And then measure the same distance again, from the centre of the prism to the QHY CCD, and use spacers to position the QHY5 at the same distance, as the Atik is from the prism.

In theory. When I focus the Atik camera on the Moon or bright field star. My guide camera should also be focused.

[Psychobilly]

Kens your man on this one he helped me out no end... he even sent me a really usefull pic of what I needed to measure up...

I can send you some solder tipped grub screws to replace the thum screws that comw with it they are a lot kinder on the prism assembly and make fine focus adjustment a lot easier ... the standard scres tend to chew up the prism arm making small adjustments a nightmare...

PM me you postal addy if you want some and i'll get them in the mail to you...

The moon is quite a handy target for setting up the spacing and focus of the guidecam...

Billy...

[PaulB]

Thanks Phsychobilly,

I'll PM you when I have the replacement turret. Do you also use a TS OAG?

How did you set up the focus balance of your guide camera?

And-am I correct, because the prism fell out and I didn't notice how it was seated.

It isn't correctly seated in the housing, with the correct depth and tilt. And this is why it didn't pick up Pollux or any other surrounding bright stars, during last week-ends test?

I was expecting to see a large out of focus star.

Also-how much of the secondary should the prism see? All of it, or just one tiny portion. And; would a fast, short focal length Newtonian. Effect the OAG's ability to pick up stars with my QHY5 guide camera?

I'm sorry to be asking, these questions. But I am new to OAG's

[MikeWilson]

Hi Paul,

Did you find an answer to your questions? I too am looking to embellish my fast newtonian with an OAG (I'm currently looking at the SX filter wheel + OAG) and I'm trying to find out the answers to the same questions that you were:)

All the best,

Mike