OAG Help

[alan potts]

Right I am considering trying some shots with my 2700m Mak from SW, it hasn't seen light for a long time. Now I believe to use this type of focal length an OAG is required. Now I am looking at the Zwo OAG purely for value but there is no real reason why I could not buy one of the others FLO offeres. I have a Zwo 290mini that I guide with at the moment.

Basically am I on the right path and will any of the OAG's fit the 2 inch visual back that is fitted to the scope. I don't want to waste too much money if this proves next to impossible to image with, and selling unwanted gear out here is almost impossible too.

Alan

[Jkulin]

Hi Alan,

I’ve been evaluating OAG’s and have been using the Celestron for a couple of years now and it really is very good and solid....but it’s 46mm thick and will mess up your back focus if you need a specific measurement.

I have ordered and messed around with the following: -

Orion Thin OAG - this appeared OK, but didn’t arrive with all the right fittings so was sent back without testing.

Starlight Express Thin OAG - looked good but uses a mirror rather than a prism, and glue present untidily all over the place.

ZWO OAG - Good value for money but tiny prism

Moravian OAG -Absolute rubbish, the biggest waste of money that I have ever spent on a piece of Astro equipment.

QHY Medium OAG - Absolutely superb workmanship, I had to make my own adapter to fit the Moravian 7 position 2” filter wheel, but it really is solid and a pleasure to use.

I had to make a revised adapter as I needed the OAG to be closer to the primary, easily rectified though.

you can pickup a QHY for around £90 secondhand and so far I am really impressed.

Hope that helps.

 

[alacant]

On 09/08/2019 at 06:28, alan potts said:

I don't want to waste too much money if this proves next to impossible

Hi

+1 to all of @Jkulin...

Whatever you get, I'd recommend a proper focuser for the guide camera, e.g. this one, which just works. Push-pull focus over 2700mm is going to be near on impossible and I think you'll also need to bin -as in the sensor- your 290 to get stars.

Cheers and good luck.