Guidescope and main scope view

[AstroNebulee]

Hi

I'm asking about the views through my guidescope and main scope so excuse me if this is a stupid question or seems muddled. I've fitted my zwo mini guidescope onto the fs bracket on my  evostar 72ed with my zwo asi120mc-s screwed onto it, then I've put my main imaging source, my Canon 600D onto the scope via my field flattener, when look through the guidescope via sharpcap or atp, what is in the centre of my dslr isn't quite in the centre of my guidescope, but when I manually tilt the front of the guidescope down towards the ota I can get both images the same, so my question is should I shim up at the back of the guidescope bracket to give me this view or is it OK to have the slight difference in views. I shan't be platesolving just yet and want to get to know my guiding with phd2 and pa with sharpcap better first and just use my dslr via an intervalometer. Thank you for reading and my baffoonary. 

 

Clear skies 

 

[PeterCPC]

It does not have to match up exactly - just be in the same general area.

[AstroNebulee]

2 hours ago, PeterCPC said:

It does not have to match up exactly - just be in the same general area.

Thank you Peter. It is roughly in the same area just a little bit higher up as you'd expect being in the fs bracket on the scope. 

[AstroNebulee]

Just an update to my earlier topic here. I've included some images taken wurh my guidescope and dslr set up. Still not been able to get it out in anger so this is a test through the window. One image shows my dslr screen and the next two images are one as it sits on the findershoe on the scope and the last one shows it with a little bit of a shim on the back end of the shoe and bracket. Is the one with the shim better in anyone's opinion 

[ollypenrice]

There is no need for close alignment between guidescope and main scope. For years I've been using guidescopes bolted down hard onto main scopes with no means of aligning them. I prefer that to using adjustable guide rings because what really matters is the stiffness of the connection between the scopes.

Remember that adjustable guidescope rings were not invented to allow you to align guidescope to main scope: they were invented for precisely the opposite reason, which was  to let you set your guidescope off axis to find a guide star in the days when insensitive guide cameras struggled to find them. That problem no longer exists.

If you have a literally perfect polar alignment (unlikely) you will see no difference whatever between an aligned and a not-aligned guidescope. In the real world what you will see is that polar misalignment will cause your imaging camera pictures to rotate around the guidestar, wherever that guidestar is. It may or may not be in the frame of the main image, depending on where your guidescope is pointing. I suppose that, with a truly awful polar alignemnt, you'd be best off with the guidestar in the middle of the main image. In reality, with a decent but imperfect polar alignment it really doesn't matter if your guidestar is off axis. The longer your subs the more it matters but I often use 30 minute subs with a randomly aligned guidescope and a decent but not obsessive polar alignment. I can't see any field rotation in half hour subs and five minute subs would obviously give six times less - so this is a non-problem.

Olly

[AstroNebulee]

Thanks Olly, a very good informative answer, I really appreciate it, so the first image with the shim under it should be plenty enough with a decent polar alignment then. Wow you get 30 min subs I'd just love to get 5 min subs guided, I'd bd delighted with that as I've only had 30 sec max before without pa and guiding. Just need to clouds to disappear so I can't test it all out. Thank you again.