Off axis or guide scope

daine042 (Daine) · #1 11-09-2014, 07:00 PM

I have just bought myself a gso rc 6" and eq5 pro go to mount in the hope of getting into astrophotography. I was just wanting opinions on what type of guiding you all recommend? I will be using my nikon dslr as the imaging camera and also have a meade dsi 1 and was planning to use that as the guide camera. So what to get... Off axis guider or guide scope?

Garbz (Chris) · #2 12-09-2014, 06:45 PM

I suggest a guide scope. OAG works great at long focal lengths but is better with large apertures and very sensitive guide cameras.
I suggest the Orion mini autoguider package I've used to happily guide a 2m scope though these days I use a focal reducer and am shooting at closer to 1250mm (very close to the RC6).

That said I'm sure someone will say OAG.

Amaranthus (Barry) · #3 12-09-2014, 06:47 PM

I politely disagree with Chris. OAG all the way if you want no issues with flexure, ever, and maximum utility across different setups.

I use mine successfully with an ED80 at 384 mm FL. It can work well when going wide!

glend (Glen) · #4 12-09-2014, 06:52 PM

I use a guidescope and can't see any obvious advantage of the OAG. Mine is the 60mm ZWO guidescope which is a great match for my ZWO guide camera. Its fairly foolproof running with Metaguide and there is no fiddling required. Whatever guidescope you decide on (if you go with a guidescope) get one with a focuser - I had an Orion Mini-guideer and setting the focus was a chore if you got the version that has the parafocal ring - just spend the xtra to get the focuser version.

Btw no problems with flexure on either of my scopes, a 127mm f12 1500fl iStar or my 8" imaging newt. I doubt you would have any flexure issues with that RC.

daine042 (Daine) · #5 12-09-2014, 08:09 PM

Would the guide scope cause any weight issues with the mount? The tube is around 6kg and the cameras together weigh maybe a kilo.

Rex · #6 14-09-2014, 07:13 AM

Hi Daine, congrats on your new set up mate. Your mount will hold your scope, camera and a guide scope with no problems at all. I have the same mount as you and I have an 8" reflector, with a 4" guide scope, two cameras, dew controls, straps, cables and finder scope all hanging off it and it has no problems.

As mentioned above, flexure and dew control are really the biggest issues you will have to face with a guide scope. flexure is just a matter of making sure brackets etc are strong enough and the two scopes are solidly fixed to each other. There are some issues with using an OAG as well. If your focuser isn't strong enough you can add sensor tilt because the focal train becomes longer and sticks out further, therefore your focuser may droop because of the extra leverage the camera weight has on it.

RobC (Rob) · #7 14-09-2014, 09:30 AM

I would suggest an OAG. I recently purchased one of these http://www.optcorp.com/celestron-off-axis-guider.html . It works well and I use it with all my scopes ranging in focal length from 480 mm to 2500 mm. I purchased an additional 2" inch to male M48 adapter to get more light onto the OAG prism and a female to male C adapter to mount the guide camera on the OAG

From experience the HEQ5 pro can be loaded up to about 15KG. So long as it is well balanced and your polar alignment is spot on it will track well. Another advantage of the OAG is that it reduces the amount of balance weight and is easier to balance when compared to a guide scope.

Cheers

Rob

John K · #8 22-09-2014, 07:11 PM

aghh...the old OAG vs guidescope dilemma.

Well, I think that the real issue is how well everything is bolted onto your telescope.

If everything such as the guidescope (inc. it's focuser and guide scope rings), mirror cell, focuser, adaptors, etc are bolted together really well then a guide scope could work for you.

If any of these is not 100%, then OAG is the way to go.

Went through this journey a few years ago - admittedly with a 12.5" and 80mm guidescope - OAG finally did the trick.

Most people will suggest that under 1000mm FL imaging guidescope can work well. Above this, unless you have a super deluxe mount and scope, then OAG.

Also, if you have a very sensitive guider, and imaging from a dark sky, you will never have issues finding a guide star with an OAG.

Let us know how you go.

Bassnut (Fred) · #9 22-09-2014, 08:24 PM

Quote:

Originally Posted by Garbz

I suggest a guide scope. OAG works great at long focal lengths but is better with large apertures and very sensitive guide cameras.
I suggest the Orion mini autoguider package I've used to happily guide a 2m scope though these days I use a focal reducer and am shooting at closer to 1250mm (very close to the RC6).

Yes.

orion69 (Knez) · #10 22-09-2014, 09:31 PM

Quote:

Originally Posted by Garbz

I suggest a guide scope. OAG works great at long focal lengths but is better with large apertures and very sensitive guide cameras.
I suggest the Orion mini autoguider package I've used to happily guide a 2m scope though these days I use a focal reducer and am shooting at closer to 1250mm (very close to the RC6).

No.