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iwols

fixed mount drift alignment but not as we know it

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Posted (edited)

hi in the coming weeks im hoping to get my obsy/mount complete and will be starting from new ,always manually set my polar alignment reasonably well most of the time and never done drift alignment which got me wondering.With it being a fixed mount could i manually keep tweaking dec/ra settings so polaris goes round the reticule circle (its the clock type) perfectly if that makes sense thoughts as always appreciated

Edited by iwols

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I dare say you could...but it would be a massively tedious task...for which life is to short! imho.

Why bother when there are great tools out there to make life easy for you...

Steve

 

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whats your favourite tool steve

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I was reasonably successful using the polar alignment feature of PHD2, which is a drift based tool, so it does take a little time to establish a base line etc.

However just last week I had a go using the tool in  Sharpcap and was very impressed. Its very quick and easy to use......

Steve

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thanks steve might have a look at the sharpcap version ,any more recommendations guys

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my only thought on asking this question was ,there no calculations ect,ect,what you see is what you get and once set up will be easier and quicker to just take the reticule cover off and have a look to make sure your polar aligned and hopefully saving time just my simple thoughts:icon_biggrin:

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Have a look at the DARV method.

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A lot of the software uses an iterative method which just gets more accurate with each run.

Can't beat a permanent drift aligned mount!

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Try the Polar Drift Aignment method in the latest development snapshot of PHD2. You point at the pole, select any star then press the button. After a short time  it setles and shows on the screen where you need to move the star to (using  the alt and az knobs). Its good down to about 10 arc minutes error. Once you are there you should calibrate and then any of the other tools are easier to use to get more accurate PA. The other new tool in PHD2 is Static PA  which also operates near the pole with an algorithm similar to Polemaster but using your guide scope or imaging scope and, where possible, automated slewing of the mount. But the classic Drift Alignment is the most accurate of all. 

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Posted (edited)
10 hours ago, Tim said:

A lot of the software uses an iterative method which just gets more accurate with each run.

Can't beat a permanent drift aligned mount!

I agree. I've tried various tools including PHD2, but I've always found drift alignment to be just as effective and often more simple. I use the "DARV" variant - which is just drift alignment with a camera, but it's given me great results pretty quickly. Here's what I think is the original article by Robert Vice, on CN:

https://www.cloudynights.com/articles/cat/articles/darv-drift-alignment-by-robert-vice-r2760

And here's a SGL thread about the same, with some useful discussion:

https://stargazerslounge.com/topic/205355-drift-alignment-the-darv-method

It's not for everyone, but it suits the way I work. Worth a look.

Nigel

Edited by NigeB
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My mount now has a built in routine which is super accurate and easy to use.

However I genuinely miss the sessions spent drift aligning just with an eyepiece. I used to pick partly cloudy nights, and it was always a little thrill to have a large bank of cloud pass over, return to the EP and see the star still there in the centre 5, 10, 30 minutes later.

With a properly polar aligned mount I have taken exposures 3 hours long without rotation errors or guiding issues. Really is worth doing it right :)

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I've tried just about every method short of those that require pointing at the pole (my imaging train impacts mount anywhere near north). I've had the best success with the DARV method. Although I've probably managed a more accurate PA by classical drift alignment, DARV appears to achieve a good enough PA in a much shorter space of time for me and time is precious as I tear down every night.

If I had a permanent setup I'd go with classical drift align any day though. Takes all moving scope parts out of the equation.

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Polaris is a bad star to use. In RA it describes a tiny circle during the sidereal day so the resolution of information is as bad as it gets. I'm a great fan, with an observatory mount, of the classical drift method which provides a software-free direct observation of that which needs observing. My opinion? Just do it.

Olly

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Okay...confession time!

I have never attempted a classical  drift alignment ( ahh....I feel better for getting that off my chest😬).

Until last year I had neither an Eastern nor a Western horizon...our house blocks the west completely and trees blocked the east, so the process as far as I understand it wasn't possible. Last spring we had the tree surgeon round who removed the offending Leylandi jungle! So although I had a bunch of extremely unhappy neighbours, I do at least now have a reasonable view of the Eastern horizon. It's only since then, that I have been able to perform a PHD polar alignment, requiring an eastern or western horizon.

Having followed this thread, I reviewed the classical,drift alignment process, which admittedly does look pretty easy. Question is...how accurate would it be for me as I can not see a western horizon?

Steve

 

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Posted (edited)

You can use East or West, in fact you can use pretty much anywhere it's just that the drift is fastest at the points generally recommended.

When aiming south it's a good idea to start east or west of the Meridian rather than cross it and do a Meridian flip while drift aligning as the drift alters direction.

Dave

Edited by Davey-T
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8 hours ago, Davey-T said:

You can use East or West, in fact you can use pretty much anywhere it's just that the drift is fastest at the points generally recommended.

When aiming south it's a good idea to start east or west of the Meridian rather than cross it and do a Meridian flip while drift aligning as the drift alters direction.

Dave

Thanks Dave....

Would you recommend investing in an illuminated reticule eyepiece for this or could I use a camera? 

Steve

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I've used a proper graduated illuminated reticle which is the best thing and also has other uses, bit pricey though.

Just using PHD with guiding off rather than using its drift aligning option, works well if you get North up on screen.

You can use any imaging software that has crosshairs on the screen really.

Dave

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2 hours ago, SteveA said:

Thanks Dave....

Would you recommend investing in an illuminated reticule eyepiece for this or could I use a camera? 

Steve

Have a look at DARV to use your cam.

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well just looked at sharpcap and decided to purchase a licence just for the use of the polar alignment tool,not had chance to try it yet though

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iwols,

You don't need the licence version to use the Polar Alignment Tool. The $$$ version only adds a "live view" adjustment capability.

 

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The most recent version of SharpCap requires a licence for the Polar Alignment tool in my experience - I was blocked from using it until I upgraded.  However, the licence fee is small and, given how good the tool is, well worth shelling out for in my view. 

The Polar Alignment tool in SharpCap is really, really simple has made a material difference to my set up time, having only a semi-permanent setup outside (mount), which tends to get knocked each time the scope is put on.  I can get a very good polar alignment in a matter of 2 minutes and move on to the next challenge.

I also find that SharpCap is a useful tool just for testing things and don't begrudge the payment in the slightest.    

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I could never get the sharpcap polar alignment to work. I know its only cheap firstly I am not prepared to waste money on something that will potentially not work and I felt a bit like I was asked to check out the beta and report any faults to help develop it only to find I then had to pay. I do appreciate that someone has put in time and effort . 

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21 hours ago, Jbro1985 said:

The most recent version of SharpCap requires a licence for the Polar Alignment tool in my experience - I was blocked from using it until I upgraded.  However, the licence fee is small and, given how good the tool is, well worth shelling out for in my view. 

The Polar Alignment tool in SharpCap is really, really simple has made a material difference to my set up time, having only a semi-permanent setup outside (mount), which tends to get knocked each time the scope is put on.  I can get a very good polar alignment in a matter of 2 minutes and move on to the next challenge.

I also find that SharpCap is a useful tool just for testing things and don't begrudge the payment in the slightest.    

Well at but £10 I thought ide take the gamble just hope it works with my guide camera which is a st80 with a focal length I believe of400 and qhy 5l hi mono camera cheers

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On 16/03/2018 at 16:31, spillage said:

I could never get the sharpcap polar alignment to work.

Well - if you do get it to work, it makes life a lot easier.  It's a bit like having a pole master without paying £260+

Not sure what the issue might have been.  As long as sharp cap is getting the image and you're pointed roughly at the polar north, you rotate 90° on the RA, it uses a plate solving technique and tells you the adjustment to make and you're done.  Perhaps if you post the troubles you were having (have you already?) they might be resolved?  Given that it works for a huge number it sounds like user or hardware error.

I would like to say, this hobby is made world's easier by amatuers producing programmes, drivers and software. Often all is requested is a little help and a thank you.  Sometimes, when work is complete, a small sum may be requested.  I find the attitude of not wanting to be involved in testing something but wanting it to be perfect and free or perfect and really cheap a little regretful.  

I am fairly new to imaging, and I am blown away by the community and the help and assistance provided at all levels for little more than a thankyou.

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