[lazjen (Chris)]

Originally Posted by Jon

I've got a very similar setup to yours - G11, with a Canon 60Da and a SCT10" (mines 2540mm focal length f/10, you are at 2000mm f/8). I started imaging about six months ago so I guess I'm a bit further up the learning curve. So some thoughts:

Always good to hear from more people, especially those with similar situations.

Originally Posted by Jon

1) Polar alignment - I never found the polar alignment helper much help in the Gemini system. Do a good drift alignment and leave the tripod exactly where it is if you can. I keep mine on a balcony under a tarp. Obviously, I take the mount itself off the tripod!

I have no such luck. Although I have a reasonable sized backyard, I'm really constrained in my location due to street lights, roads, etc to a very small suitable area. And it's not a place I can leave setup permanently. Last night I got to setup again, and I "nailed" PA to a similar level very quickly. I've just setup again tonight and have already done some PA to probably close to the same level. I'm waiting for the camera battery to charge (because I forgot to recharge it earlier *sigh*) to check further.

Originally Posted by Jon

One of the side benefits of getting set up for autoguiding is that you can use PhD to do a quick polar align. It's easy as pie. See here: http://njstargazer.org/PolarAlignment.asp at the bottom of the page.

I'll keep this in mind when I get to that point. I know I'll be referring back to this thread as I change/add things.

Originally Posted by Jon

Try to set the time as accurately as you can, but you've got plenty of leeway. If you have a field of view of 5 degrees in your finder scope, that equates to 25 mins of sidereal time; in other words, if everything else is bang lined up, the time you enter can be more than 12 mins off and the object should still be in your finder.

Checked the time tonight - it's certainly within a minute now, maybe 40sec.

Originally Posted by Jon

BTW, a word on finders: if I'm honest I have more than once been caught out cursing the "unpredictable GOTO alignment" or whatever, before I've realised that the finder isn't lined up with the main scope. It's easily bumped out of place, especially if you are packing the scope up every night. The very FIRST thing you should check, once you've got the first alignment star in the centre of an eyepiece, is that the star is also in the dead centre of your finder, and if not, adjust it. I have to adjust 4 night out of 5.

Oh yes. Much cursing the first night I setup when I forgot to line up the finder scope with the main scope. I do a rough alignment just after I balance the scope by pointing off to some distance rooftops. Then, like you've mentioned, fix that up when I align the star.

Originally Posted by Jon

Finally, as you mention, once you attach the camera, the star that was nicely centred in your eyepiece/diagonal view is way off or nowhere to be seen in the camera live view. Move the scope back so the star in in the centre of the camera view and his Align->Synchronize on the Gemini handset. Or build the model using the camera from the start.

I've got better with this part now and do a couple of alignments with the handset to help me out. Useful for helping with focus too.

Originally Posted by Jon

2) Focus

I'm a bit unsure what you mean by "zooming in" on the target. BackyardEOS, which I use and would heartily recommend, will allow you to select and view in close up any stars on your image, to help with focus. But I think you are doing the right thing by focusing on the moon or a bright star first, then going to your target.

Yes, it was just a but difficult to recognize the focus point vs what you see when there's a huge moon surface to see. I think I'm starting to get this a bit better, but the problems remain.

Originally Posted by Jon

I have a motorised focuser that is controlled via USB. It's not cheap ($300 for my focuser plus USB controller) but it is a boon. Allows very precise focus control without all the jumping about you get when you touch the focus knob. Plus, it means I can sit inside and control the scope and camera from the PC! The G11 is a breeze to control with the Ethernet cable.

Ok, this sounds awesome. Is the USB controller connected to the Gemini unit?

And yeah, loving ethernet control of the G11. Played with the web page, plus I've messed around with Stellarium Scope/Stellarium.

Originally Posted by Jon

3) Errors and limitations

Get into autoguiding! As all the others have said. It's not that expensive, and not that complex. Something like this: http://www.bintel.com.au/Astrophotog...oductview.aspx is all you need. I have the larger version http://www.bintel.com.au/Astrophotog...oductview.aspx as the extra precision helps with the long focal lengths. You and I jumped in the deep end with our setups - starting off imaging with a $400 5" f/4 reflector or somesuch atop the G11 would be a *whole* lot easier. You could probably get 1-2 minute unguided subs with such a setup and an f/4 scope is going to collect a whole lot more light an that time than your big slow f/8. However good my polar alignment, I've not been able to comsistently get a usable unguided sub longer than 30" with a 10" SCT on the G11.

For your setup, there's really no choice but to bite the autoguider bullet.

I am convinced, do not fear. I will be looking into this in greater detail very soon!

Originally Posted by Jon

The good news is, it's not that hard, at least to get going. With something like the Orion starshoot autoguider camera in the links above, you just fit the camera into the finder scope, plug a cable from the camera to the Gemini autoguider socket, plug a USB cable from the camera to your laptop, fire up PHD ("Push Here Dummy") free autoguider software, and four mouse clicks later you're off.

As I was reading today I noted that APT can work with PHD, so that's cool too.

Originally Posted by Jon

I'd also recommend you get a focal reducer when you can afford it. (see this thread: http://www.iceinspace.com.au/forum/s...d.php?t=103278 ). Not only do they create a larger field (without one you won't fit much of Eta Carina onto the image at 2000mm f/8!) they also effectively make the focal ration faster: you're getting more photons per pixel, so your subs can be shorter. So the larger field and smaller objects mean you can take loner subs without tracking/guiding errors showing up; but you need less time to get the same level of brightness. So you're getting a bonus both ways.

I have a focal reducer already - a 0.5 2" GSO - but I can't get it to focus with the camera. I think it's too far away from the sensor. I had troubles focusing with the eyepiece as well, until I put the eyepiece right up to the reducer.

Originally Posted by Jon

So don't worry about zoom. If anything, you want to go in the opposite direction - make the image smaller. You've got 5472 x 3648 pixels to play with - do the "zooming" in Photoshop afterwards by just cropping the bit of the image you want.

Yes, I'll not worry about it for now until I see the effects of all the other changes I need to make.

Thanks again for the info.