Just got an Off Axis Guider

[Catanonia]

For the Doubting Thomases....

The size of the pick -off prism is 10mm which will cover the full CCD chip in a QHY5 so the area being guided on is as large as can be accommodated by the camera at the focal length of the scope. ie if you used the same guide camera on a guide scope with the same focal length you'll see the same field of view.

arrr , was wondering that myself.

I assume it is always best practice to have the prism above and along the longest length of the Imaging CCD /CMOS

Ie at the 12 oclock position to site alongside and ontop of the CCD ?

[Merlin66]

Yes, that's the way I used to set it up to get maximum guide FOV without interference to the imaging CCD.

This also usually places it in Dec just above the target object....

Ken

[daz]

I am very interested in the results here, as I want to get my 12"" OO newt up and running with guided exposures, and it seems to me to make the whole dual-bar set up unnecessary.....

Which OAG did you get Cat?

[Merlin66]

Just to jump in....

Lumicon have a great 2" Newt version of the OAG ( I should never have sold mine!) lowest profile - minimum back focus requirement of the ones I've used. Solid and top quality..... ( Jeez I wish I was on commission!!)

Lumicon Newtonian / Refractor Easy Guider 2inTelescope Accessories | Rother Valley Optics

Ken

[Catanonia]

I am very interested in the results here, as I want to get my 12"" OO newt up and running with guided exposures, and it seems to me to make the whole dual-bar set up unnecessary.....

Which OAG did you get Cat?

Lumicon 2inch OAG from Rother Valley. You can see it on their website.

Lumicon Newtonian / Refractor Easy Guider 2inTelescope Accessories | Rother Valley Optics

[Tim]

There you go Steve, told you it was flex

I usually do my par focalising in daylight if possible, if not, then look for a bright cluster like m45 or Praesepe to help with bright stars to focus with. I usually have mine set at 90° to the imaging camera so I know which way to slew to get the bright star into the prism. But once you have it set it will always be the same for your dslrs.

You need now to figure the maximum useful exposure time for a given object type, and you can do that using the histogram, But you will soon see that 10 x 20mins on a nebula gives much better results than 20 x 10mins feature wise. You'll still need around 20 odd subs to start to get the noise down properly, so you start to end up with single images that have taken 10, 20 or 40 hours each. Welcome to my world

Tim

[Catanonia]

There you go Steve, told you it was flex

I usually do my par focalising in daylight if possible, if not, then look for a bright cluster like m45 or Praesepe to help with bright stars to focus with. I usually have mine set at 90° to the imaging camera so I know which way to slew to get the bright star into the prism. But once you have it set it will always be the same for your dslrs.

You need now to figure the maximum useful exposure time for a given object type, and you can do that using the histogram, But you will soon see that 10 x 20mins on a nebula gives much better results than 20 x 10mins feature wise. You'll still need around 20 odd subs to start to get the noise down properly, so you start to end up with single images that have taken 10, 20 or 40 hours each. Welcome to my world

Tim

cheers Tim, was no doubting it was flex once I asked what flex was Rather than fight it, thought would eliminate it totally with an OAG.

Next job is either 12 or 3oclock positioning of the OAG for the focusing reason. I like to ensure guide as well as main are bang on focus with a B Mask every session.

My max so far is about 7 hours made up of 10 min subs, now I am guiding 30 mins on a semi foggy night, pretty sure this will be the norm for me now baring b**(&*( aeroplane trails

Just need some good clear nights now. My target is M78, a toughy but want to get close to Olly's rendition in DSO section, I know it was done on a CCD, but pretty sure I can get close with about 8 hours worth.

[daz]

Thanks Cat - will look into this more...

[Catanonia]

Thanks Cat - will look into this more...

No worries, will probably make an article as part of my web site and post the major parts here in a new thread for all those confused , like me before, about OAG.