Polar aligning an Az GtiX

[LondonNeil]

It's raining again so my mind turns to working out solutions to problems and as a newbie still trying to get to grips with the basics I've plenty of those!

I have an Az GtiX.  I've aligned the 2 shoes and can then mount a st120 on one side and mak127 on the other.  Currently this is just for visual. 

I happened to pick up a skywatcher eq wedge cheaply (I was the only bidder on ebay), and when I get more confident/experience I would like to try a bit of imaging. So I'm trying to work out how to set up equatorially.   Let's assume I've got the s/w uploaded and the mount in eq mode, what are the steps to the physical set up?

1. Stick the tripod out with one leg pointing north by eye,  using a compass (no need to worry about magnetic vs true.... it seems they are less than a degree out Currently)

2. Level the tripod 

3. Mount the wedge on the pier extension,  tilted appropriately.  For the skywatcher wedge that's 90⁰ - local attitude. Wedge pointing to North by eye. 

4. Add the az gtix 

5. I now need to dial in the polar alignment.  Yes? And here lies problem one,  the mount has no polar scope. 

Okay....if I can align the shoes to point the scope 'straight up' the axis of the mount then I can use a scope mounted in either shoe right?  I've got an illuminated Reticle,  so fit this and once the shoe is aligned I'd be able to adjust the wedge in az  and the angle on the wedge,  to align the cross hairs on polaris.  DONE!

Ahhh..... problems.  How to align the shoes/scope on the axis of the mount?    If I place a short dovetail in one shoe,  use a hole drilled in it to screw in a pointer that points across the top of the mount (towards the other shoe), if that pointer is bang on central with the axis of rotation of the shoes (big if!) And perpendicular to it, I can align the pointer with the bubble level built into the top of the gtix using it like a bullseye target,  and the shoes and scope would then be aligned with the mount axis....I think!   Getting the pointer central to the shoe axis might be tough.... getting a hole central across a dovetail is possible,  and perpendicular through the dovetail.... but does that mean the centre line of the dovetail lines up with the axis of rotation of the shoes and is not offset?  Because if it doesn't,  the shoes won't align on the axis of the mount unless my pointer's aim is equally offset.  Hmm. 

Is there another way?  Glue a finder shoe directly to the side of the mount and use a finder as my polar scope..... anything else?

I'm guessing I'm going to need to do final adjustments using the drift method,  should I just go straight from lining up to North on the compass by eye,   to drift adjustments and forget attempting to find a way to get close first?  Or is there another way to visually align the az gtix mount axis to polaris?

I recognise my explanation above may make little sense without drawings....

If you've read it,  tried to understand it,  and given up,  I thank you anyway!

[PhilB61]

Hi, what scope and camera combination are you planning to use and are you thinking of planetary or DSO imaging as they each have quite different requirements. Also are you going to use a laptop or similar to manage your sessions. If using a laptop then a rough eyeball alignment then using one of the automated PA routines in say NINA or Sharpcap will get you precise enough for imaging. If you are thinking of planetary then you could probably do that leaving the mount in Alt/Az mode and no need to worry about polar alignment. Just a note that Polaris is near but not at the NCP and aligning on it will result in drift in long exposures. Sorry can't help with other methods as I always used a laptop with my AZ-GTI and my other mount has an illuminated polar scope (although I always use NINAs 3PPA routine now)

[LondonNeil]

I've not thought that far ahead.  I was thinking I'd see what could be done with my smart phone camera on an eyepiece mount,  planetary initially I think. Dso would be great as a progession.

I thought get it aligned and running in eq and see if I could take, and process,  some long ish (well several minutes) of video.  I'd have thought it would be long enough to see rotation if working in alt az, no?  If it was enjoyable I'd have a think about a cheap astro camera but that was not the plan initially. 

I'm not sure how a s/w package would help with the alignment,  it's the wedge that needs az and alt and adjustments to polar align the mount. Does the package do drift and give you instructions?

I realised I don't need to worry about my pointer being off centre.   I would align by drift once,  at the alt on the wedge,  and make a mark on the mount corresponding to the pointer position

[LondonNeil]

For the avoidance of doubt,  this is the wedge I picked up. 

https://www.harrisontelescopes.co.uk/acatalog/star-adventurer-wedge.html?gad_source=1&gclid=CjwKCAjwwr6wBhBcEiwAfMEQs_n3aihmolvtJv_zlosEWsuV64BS4Of3LEtVpPKQFB-VnoCApB7RsxoC5qAQAvD_BwE

[PhilB61]

I started exactly the same, planetary imaging using smartphone holder at the eyepiece. It's a few years ago now and I only had a manual mount so allowed the target ( primarily Saturn) to drift through the field of view whilst taking video. Then used PIP free software to select a region of interest, convert and stabilise the image before stacking the best frames. The images where tiny but I was still amazed at what could be achieved with a basic setup. And yes the PA software takes a series of images and gives instructions on which way to move the mount, which are updated every few seconds but probably unnecessary for what you are initially trying to achieve. Some of the brighter DSOs such as Orion nebula can also be imaged taking lots of very short exposures, and stacking, use your shorter focal length telescope to reduce the impact of tracking and PA errors. 

[LondonNeil]

Cool, very useful to know in not completely misunderstanding how this works then!

Does the PIP s/w also rotate the image then to stack frames,  or were the videos short enough that the rotation could be ignored?  

Ah cool so I guess using the PA s/w speeds up alignment? I would guess that it can pick up the drift more quickly and instead of sitting there for whole subs to check for movement before adjusting the s/w can detect the movement quite quickly. 

I have read up and can see how,  with practice drift aligning manually wouldn't be to tricky.  Although if you can get close with a polar scope first that must speed things up no end. 

I'd love to get a few dso like orion in time..... I've got to get better at visual first but,  yes I can imagine a cheap imaging camera on my Christmas list in time 😁

[SteveNickolls]

Hi, interesting post. As regards polar alignment you might consider taking advantage of the fov through one of your telescopes + camera pairings when in EQ mode and directly polar aligning using SharpCap Pro's (SCPro) polar alignment tool. SCPro does require a fov between I recall 0.5 to 5 degrees. If you are intending planetary/lunar/solar imaging just don't bother trying to make an EQ set up just go Alt-Az.

Good luck with whatever you decide to do.

Cheers,

Steve