Help with guide scopes

[AdrianF]

I need to get a guide scope for my refractor. What criteria should I be looking at in regards to size, aperature and f length? Is bigger better?

It will be used on a 127mm f7.5 refractor and used with digicam at first but will be replaced with a dedicated GuideCam eg Orion cam when I can.

Adrian

[Bassnut]

Thats a wide field OTA, pretty much anything would do the job. I use and would recommend an ST80, cheap and light. I use it with a 3m FL OTA with excellent results. 1.3 kg and $219 from Bintel, 80mm F5. You would only need more apature and FL with WAY longer OTA FL.

[mrsnipey]

Adrian. I made my own guide scope using an 80mm lens from the SurplusShed and a piece of pvc piping - cost about $100 including rack-and-pinion focuser from Andrews. It's f/12.5 (not sure if that makes any difference) but it works excellently with my QHY5.