Skywatcher AZ GTi + Polar Scope?

[herne]

Hi all,

Keen to make the most of my AZ GTi mount with wedge in EQ mode for astrophotography (with DSLR, unguided), thoughts turn to better polar alignment.  At present I'm merely pointing my set up at Polaris and centering it in my camera's screen - I'm aware this can be improved.

Without wishing (at this stage anyway) to get into guiding and electronic means of polar aligning, I've been considering how to make improvements.  My first thought was to buy a red dot finder and use that to align my scope and Polaris.  However as I'm already centering Polaris in my DSLR screen I don't really see any tangible improvement (correct me if I'm wrong).

So then I thought perhaps I could mount a polar scope (such as this Skywatcher polar scope) onto my telescope (a William Optics Z61 II, so there is a mounting shoe on top available) using a mounting bracket such as this bracket I found on eBay.

Is this feasible or am I barking up the wrong tree and this "solution" would be unsuitable for the mount?

Thanks.

[EntropyTango]

Sounds like you went straight for astro-photography

My advice is to always do at least 6 months of visual observing before plunging into AP

That will teach you to align and find objects and what to expect when you are imaging

The red dot finder probably won't do much.

And the WO scope is great for wide field AP but not that good for observing most astronomical objects

Just wondering if you have a diagonal and any EP's?

[herne]

5 hours ago, EntropyTango said:

Sounds like you went straight for astro-photography

My advice is to always do at least 6 months of visual observing before plunging into AP

That will teach you to align and find objects and what to expect when you are imaging

The red dot finder probably won't do much.

And the WO scope is great for wide field AP but not that good for observing most astronomical objects

Just wondering if you have a diagonal and any EP's?

I did as that's my primary interest and have been a keen (amateur) photographer for years.

I have a long term "road map" planned out for (hopefully) steady improvement of both experience and gear.  The mount was my first investment and I deliberately chose the AZ GTi as I like the compactness and multiple powering options.

The scope was my second upgrade (and a significant upgrade at that lol), chosen to compliment the lightweight set up I have in mind.

Interestingly (and perhaps surprisingly) I am yet to buy a field flattener.  Whilst curvature is an issue, pictures without an FF still allow me to assess the capabilities of my current DSLR before deciding whether that also needs upgrading and if so which route I want to take.  I'm actually pleasantly surprised so far, so a new camera can be put on ice while I assess different priorities.

Which leads me back to bumping up the priority to making possible improvements to my polar alignment, and whether it's possible to use a polar scope or if I'm barking up the wrong tree.  I've been noticing some drift (could be caused by using old AA batteries in the mount!) and trailing, even at relatively short 60 sec subs.  I'm not expecting to start taking 5min+ subs, nor am I aiming to, but I'm sure there is room for improvement here.

Anyway, in answer to your question, no I don't have a diagonal or any EPs.  I have however been trying to find my way around the stars, repeatedly practising a 3 star alignment process using different stars when I can and studying star maps, Stellarium, a couple of phone apps and making visual comparisons to the night sky aided by a pair of small binoculars.  Still a very long way to go but I'm already quietly impressed with how many more stars and constellations I can find and name than ever before.  It's been great fun.

[Shimrod]

On 12/03/2021 at 10:00, herne said:

I did as that's my primary interest and have been a keen (amateur) photographer for years.

I have a long term "road map" planned out for (hopefully) steady improvement of both experience and gear.  The mount was my first investment and I deliberately chose the AZ GTi as I like the compactness and multiple powering options.

The scope was my second upgrade (and a significant upgrade at that lol), chosen to compliment the lightweight set up I have in mind.

Interestingly (and perhaps surprisingly) I am yet to buy a field flattener.  Whilst curvature is an issue, pictures without an FF still allow me to assess the capabilities of my current DSLR before deciding whether that also needs upgrading and if so which route I want to take.  I'm actually pleasantly surprised so far, so a new camera can be put on ice while I assess different priorities.

Which leads me back to bumping up the priority to making possible improvements to my polar alignment, and whether it's possible to use a polar scope or if I'm barking up the wrong tree.  I've been noticing some drift (could be caused by using old AA batteries in the mount!) and trailing, even at relatively short 60 sec subs.  I'm not expecting to start taking 5min+ subs, nor am I aiming to, but I'm sure there is room for improvement here.

Anyway, in answer to your question, no I don't have a diagonal or any EPs.  I have however been trying to find my way around the stars, repeatedly practising a 3 star alignment process using different stars when I can and studying star maps, Stellarium, a couple of phone apps and making visual comparisons to the night sky aided by a pair of small binoculars.  Still a very long way to go but I'm already quietly impressed with how many more stars and constellations I can find and name than ever before.  It's been great fun.

I have recently asked some questions about the AZ GTI and EQ setup in the mounts section. One of the questions was about polar alignment aids, and so you may find some ideas in this thread

[PEMS]

Seems thjat you are polar aligning the scope and you should be polar aligning the mount not the scope. If you had or get an equitorial mount you can polar align the mount (which is what you want and need to do) without a scope on the mount.

As the Az GTi is really an Alt/Az mount there seems that there is no accurate option incorporated for accurate polar alignment that I can see on one. It was never it seems intended for such.

[Avocette]

You could indeed add a polarscope to your AZGTi but you’d need a lot of precision mechanical skills, and the cost would not be trivial. However you have already got the makings of an electronic polarscope - with the help of some software on a laptop or a Raspberry Pi. Astroberry.io (open source - no cost) software package on an inexpensive RPi4 has transformed the precision of my AZGTi polar alignment, and also GoTos using plate solving.

[herne]

1 hour ago, PEMS said:

Seems thjat you are polar aligning the scope and you should be polar aligning the mount not the scope. If you had or get an equitorial mount you can polar align the mount (which is what you want and need to do) without a scope on the mount.

As the Az GTi is really an Alt/Az mount there seems that there is no accurate option incorporated for accurate polar alignment that I can see on one. It was never it seems intended for such.

Thanks.  Yeh I appreciate it's the mount to align rather than the scope however something I don't understand - I see people doing an initial rough (or even accurate) polar alignment using the polar scope built into their EQ mount, then a much more accurate polar alignment using their guide scope + camera which is attached to their main scope using Sharpcap (for example).  So why not just attach a polar scope to the main scope?

I appreciate there would be an alignment issue between polar scope / main scope, but there would be for finder scope / main scope too though.  Noob questions I know but I feel like I'm missing something 🤔.

16 minutes ago, Avocette said:

You could indeed add a polarscope to your AZGTi but you’d need a lot of precision mechanical skills, and the cost would not be trivial. However you have already got the makings of an electronic polarscope - with the help of some software on a laptop or a Raspberry Pi. Astroberry.io (open source - no cost) software package on an inexpensive RPi4 has transformed the precision of my AZGTi polar alignment, and also GoTos using plate solving.

Interesting thanks, something to look into.  There's bound to be some guides somewhere 🙂.

[Avocette]

41 minutes ago, herne said:

Thanks.  Yeh I appreciate it's the mount to align rather than the scope however something I don't understand - I see people doing an initial rough (or even accurate) polar alignment using the polar scope built into their EQ mount, then a much more accurate polar alignment using their guide scope + camera which is attached to their main scope using Sharpcap (for example).  So why not just attach a polar scope to the main scope?

I appreciate there would be an alignment issue between polar scope / main scope, but there would be for finder scope / main scope too though.  Noob questions I know but I feel like I'm missing something 🤔.

If the mount is polar aligned, then the main telescope, guidescope or finder scope are all polar aligned. The mount is simply reversing the rotation of the earth from all perspectives! Of course you would like the telescope to be aligned close to the polar axis and likewise the guidescope and finderscope, but if not, the mount is still aligned. You can polar align using your DSLR but it’s more convenient with an astro camera which might be your guidescope camera. 

[StevieDvd]

You can use on of the computerised PA methods, in no particular order of preference:

Laptop - using Sharpcap (£10 paid for update for PA). This uses a PA routine that is made for aligning from a camera not on the mount axis. It will ask you to take a few inmages which are then plate-solved and Sharpcap does the maths to work out your mounys axix point versus what it should be for polar alignment.

Raspbery Pi - from the free Astroberry to the paid for versions such as Stellarmate & ASIair Pro (£300 plus) - have similar routines as Sharpcap.

I have recently obtained a used AZGTi setup and will be using a Raspberry Pi solution for PA and image capture, if all things go to plan.

 

 

[Owmuchonomy]

In order to satisfy your desire for long exposure astrophotography you have to remove all the artefacts produced by the Earth’s rotation, for example, star trails. To do that you need a device that is perfectly aligned to the Earth’s axis and rotates at the same pace as the Earth. That device is an EQ mount. The mounts are often fitted with polarscopes perfectly aligned to their axis. The orientation of other attachments such as cameras and telescopes is largely irrelevant. ‘Attaching’ a polarscope won’t give polar alignment. Your best bet is to invest in a decent EQ mount or try one of the electronic methods described above and see how it goes. If you have fixed focal length TP lenses eg 300mm try those first.

[AstroNebulee]

This may seem like the daftest question. I'm going to try and fit a eq5 polar scope via rings onto a bracket. Most of the placement positions I've seen for the polar scope are mounted onto the actual mount. So when the mount moves in the RA axis the polar scope will also. So is it better to fit the polar scope to the wedge instead as this doesn't move with the scope, it stays fixed on polaris. I hope this makes sense and a complete silly question. Also another silly question or if using say sharpcap or any other laptop software to polar align or plate solve does the software have yo keep running throughout the whole imaging session or can it be turned off once polar aligned or plate solved. I'm just trying to find a minimal non electronic way of polar aligning this mount to save pulling all sorts of laptops and such along with it. Clear skies 

Edited April 29, 2021 by AstroNebulee

[StevieDvd]

Polar aligning with a scope is normally done on the axis of the eq (wedge in this case), though a camera on the scope will suffice for the software PA software.  You won't need to keep the PA software running once aligned, but if imaging you may as well use the platesolving for centering and repeat positioning of your chosen targets.

 

 

[AstroNebulee]

4 hours ago, StevieDvd said:

Polar aligning with a scope is normally done on the axis of the eq (wedge in this case), though a camera on the scope will suffice for the software PA software.  You won't need to keep the PA software running once aligned, but if imaging you may as well use the platesolving for centering and repeat positioning of your chosen targets.

 

 

Thank you for the information. So it's best to mount the polar scope to the wedge and not the mount then? I may try my planetary camera for PA at some point. Like I said just want to try a no fuss non electronic PA set up as portability is key for me in my situation. I understand the plate solving is best kept going and I only generally image one target in a session with my dslr. Clear skies and thank you again.