Attach your Guide Scope to a DSLR 

I'm a little confused about you atatement. In my understanding, the polar alignment won't be accurate only if the axis of the guidescope parallels with it of the camera lens. Would you mind telling me why the solid connectio of the guidescope and the camera matters most?

Sure, first let's talk about polar alignment. It depends on how you are doing a polar alignment. If you're using a traditional polar scope inside the mount, then the polar scope should be aligned with the axis of rotation of the mount. Then you look through it, align polaris etc... If that's how you're doing a polar alignment, the polar scope alignment matters a whole lot (with the mount, not the imaging scope), but you'll note that it's difficult to be accurate because on things like the iOptron Skyguider Pro, the polar scope can freely rotate inside the mount, so there is inherent inaccuracy because you have to 'eyeball' getting the reticle straight up and down, which is impossible on the scale of arcseconds. Because of that, a lot of people have moved away from sighting polaris down a polar scope and use electronic polar alignment. One popular way this is done is by using the guidescope (and guide camera) and a platesolving routine like in _SharpCap Pro_ and I think the _ZWO ASIair_ uses the same concept. The way this works is that the guidescope needs to be pointed in the general vicinity of the northern celestial pole but accuracy isn't all that important because of the rest of the alignment routine. The first thing it does it platesolve the image in the guidescope, which orients the software to where the guidescope is pointed in the sky. Then it will ask you to rotate your mount's RA axis through a minimum of 90 degrees and it will plate solve again. After it platesolve's the second image, the software can calculate two important things; exactly where north or south celestial pole _should_ be based on the images it just solved, and the exact axis of rotation of your mount.. Because it knows those two things, it also knows the offset between your _mount_ and the pole. Polar alignment is the process of making that offset as close to 0 as possible. Then it has you make adjustments to minimize that offset by adjusting the alt/az knobs on the mount to minimize the error. It will plate solve again and tell you how well you've done. You'll notice that at no time does the guidescope actually need to be pointed directly at the pole, or even in line with your mount, the math will figure out the offset regardless and at no point does the imaging scope or imaging camera play into this process at all. As far as actually guiding while imaging, PHD2, or whatever guiding software you're using doesn't care what you're actually taking images of. All it cares about is that it can see a guide star and keep it in the exact same spot on the screen by feeding error corrections to the mount over time. Guiding is a process that occurs between the guidescope, software, and the mount. The imaging scope and imaging camera are irrelevant. So in order for guiding to be accurate, the guidescope and the mount must be as rigidly coupled as possible over the duration of the imaging session so that the only errors the guidescope sees are the result of the mount's inaccuracies, not the results of things like a loose screw or vibrations or being bumped etc... If the guidescope is slipping over time, it will feed bad error corrections to the mount and make it move more or less than it actually needed to.

@@KnyghtErrant Thanks for your detailed explanation. At first I was considering this process with the default mind of using the sighting polar scope and concluded that the two axes of polar scope and image scope must parallel with each other. Now I realize with the help of self-correction software, the guidescop can cacalculate the offset between the guidescope and the image scope as well as where the real pole should be by comparing multiple images captured in the general northern celestial pole area. Then it will tell you how to fine the knobs on the star tracker to minimize the inaccuracy without adjust the guidescope to fix it's axis. This is truely a talented idea!

@@KnyghtErrant Can you educate me on why it doesn't matter if the scope is on your camera vs the tracker? Does the software know after polar alignment any portion of the sky? Once you rotate your camera and polar scope to the south, how does it continue to guide? TIA.

@@michaelwmcdonald Polar alignment and guiding are two independent things, so once you've polar aligned your mount (and you may be using your guidescope to accomplish this), the axis of the mount body remains fixed with respect to the celestial pole for the rest of the imaging session and never needs to be adjusted again. You are now free to move your RA and Dec axes to point your guidescope and imaging scope towards your target. The guidescope is now functioning as a guidescope, not a polar alignment tool, so it will guide like normal off of a star in the vicinity of your target.

I've got a D750 (about the same size) and like how you did it. Can you provide a link to get the bracket? (That's the same monster lens I want to use for planets.)

just pull/push your camera in and out the guidescope until your footage is focused.

Hook up the scope to your laptop in daylight and focus on infinity by sliding the camera head in/out of the scope tube. I mark this position with a thin slice of masking tape so that each time I reassemble, I quickly put the two parts together at exactly the correct distance for infinity focus. Set the exposure & gain to auto in software which will help get an image you can see to enable correct focus. Should only take a few mins.

Or mount the L up the right hand side?

Let me start by saying I am a newbie and I don’t know anything. If you are adding a tracking scope like this then you must be using a computer or asiair for tracking. Can’t same computer or asiair be used for polar alignment instead of the built in polar scope? No need to kneel on ground.

I agree! If you figured out how to do so could you pass that info. on? Thanks!

this looks like a very viable option.. seems that at some point you are going to need access to the usb and shutter control and 150 quid a for custom l bracket seems crazy

Did you figure this out? I need to know as well. 😅

Did you manage to post the files to thingiverse?

Could you explain this a little more? The dovetail bar of what - are you referring to the Tripod Collar of a lens?

Mark, the focus will be touchy insofar as vibrations blurring your image, so just loosen the locking collar of the scope and get a crude focus established such that in a preview of the camera video, you can see the stars. Then, make minute adjustments and remove your hands from the scope each time to let vibrations dampen, check the image on screen for improved focus, and repeat the adjustments until the stars look pretty cleanly focused. That done, secure the locking ring again and you shouldn't need to refocus any more.

To balance properly on Dec, i added a longer arca swiss to the L bracket of the Star adventurer so i can move it around and get it perfect

There shouldn't be. This all assumes the camera is going to be on some kind of a mount. If that mount is pan and tilt, you can just lock that axis. If it's a ballhead, just dial in a tiny additional amount of drag (a ballhead, when setup properly, lets you grab the camera and point it where you want, and it'll stay). I use an ArcaSwiss P0 and I don't bother locking down for test shots (high ISO, shorter shutter) but do so for 15 second shots. Not sure that's necessary, though. If you're having any problem with 'droop', whether you have a pointer attached or not, go rent a P0 - you'll probably end up buying it.

Yes, that's also a solution. But some of us use the hot shoe for a red dot finder.