what should i look for with a off axis guider

[red dwalf]

morning all,

I bought an off axis guider from the bay of fleas the other day, looks exactly like the Skywatcher offering but less than half the price, in the info it said the prism was 12.5 mm but having received it i measured it as it looked smaller and sure enough it`s only 8mm x 8mm, so my question is would that be big enough for light grasp and a descent size field of view to be able to pick up stars.

having not used one before i`m interested in your thoughts and recommendations.

the width of the guider is only 15mm and comes with 5 different length T2 adapters so thought it would work very well with my imaging train, just not sure regarding the prism size.

  

[glider]

Yep, sounds right to me Rob, my Brightstar, which is basically a Celestron OAG is about 8mm too.

[red dwalf]

thanks Noel,

another question regarding PHD 2, in the "brains" settings of PHD 2 you can put in focal length of guide scope and pixel size of guide camera and it`ll work out your calibration details, my current altair guide scope is 225mm focal length, but if your using a off axis guider what focal length would you put in ? would it be the same as the imaging scope ?

 

guider looks to be exactly the same as this one, 

http://www.firstlightoptics.com/off-axis-guiders-oag/off-axis-guider.html

Edited November 18, 2014 by red dwalf

[glider]

I'd use the same focal length as the imaging scope.

Edited November 18, 2014 by glider

[philjay]

Ive used an off axis guider a couple of times, its a bit of a faff to set up but once done its fine, Having said that if Im using the short fl scope I am guilty of sticking with the finder guider which Im used to. Thats interesting about phd2 and entering scope fl I must try that when I use the oag at f7.5 which is the main reason I got it.