Polemaster

[Carole]

Due to my injured knee I acquired a right angled finder which worked well the first two times I used it but wouldn't stay in place at Kelling, I decided to get Polemaster.

What a brilliant piece of kit that is, I used it last night for the first time and could not believe how simple it is.  (Used the HEQ5 on the lawn).

Normal PA is fine for those without neck, back or knee problems and those young and fit, but no thought has gone into improving this task that many people find a real chore, by Skywatcher, thank goodness for QHY.

Roger and Roy are also using it and having seen them demonstrate and me having problems at Kelling made me press the button.  Could not believe it was so easy.

Carole

[The Thing]

Dont want to be a party pooper but you can do the same for free with Sharpcap 2.9 and now PHD2 has an even better tool both using your existing guiding setup.

[ApophisAstros]

Just wondered how they can be as accurate when they are not positioned on rotational axis of scope , would your first alignment star ever be near centre of FOV, to me that shows how close to perfect PA is, thats what i find with mine.
Roger

[The Thing]

Irrelevant. The maths takes care of it when the centre of rotation of the mount is determined and related to the field of view.

[NoelC]

I noticed a 30' offset from one alignment to repeated alignment on SharpCap.
PHD seemed to come within 15' on the second alignment.
Duncan: have you tried repeating alignments?
Would be interested in repeated alignment data on PA as well Roger.

But on the face of it 30' is pretty good I think.

Noel

[ApophisAstros]

Not sure of what your asking for?
Roger

[The Thing]

30arcsec is better than you should be able to achieve unless you have a very top end mount. With my HEQ5 and neq6 mounts 2.5arcmins is all I can achieve with a fixed pier. The adjustments are too rough and lazily engineered.
Also I find that the alt axis changes between sessions as the is no way of locking the position, the standard bolts slip and flex. For guided AP 2.5 arcmin is easily good enough.

Slightly varying results on different runs can be due to seeing change, tiny amounts of flex, algorithm inaccuracies, centroid calculation etc.

[Carole]

Roy gave me and a friend a demo at Kelling and I recall he said he could get to 30 arc sec and he has an HEQ5.

Where do I find this info on Polemaster?

Carole 

[ApophisAstros]

I`ve posted my last PHD2 log on dropbox , surely how accurate PA is has a direct effect on guiding?
Within 1 Arc minute for 3 hours.
https://www.dropbox.com/s/prnequp8v8olz2b/Guiding%206%20Octjpg.jpg?dl=0
Roger

[NoelC]

Very nice guiding Roger.
But the 1' figure you give there is for guided tracking isn't it?
Have you tried the drift alignment on PHD to estimate how close you are? - just wondered.

QHY say that "Precision (arcsec) = 6 * drift (arcsec per hour)" or that 3arcsec per hour is equivalent to an alignment accuracy of 18arcsec. On that basis, 30' alignment error should be around 6' per hour drift. If thats true I should be able to turn Dec alignment off or down very low (I've not tried - only installed Sharpcap the other day).

My mount is on a pier, but as you say the nuts and bolts are very rough and ready, and there appears to be a huge amount of backlash on the Az adjustment (oddly).  My adjustment bolts are M12x1.75 (i.e. course threads). I just tinkered with the alignment until it came in as close as I could get it. (Cloud was advancing rapidly - hence the multiple alignments).

When I first installed Sharpcap it said my alignment was 15arcmins (which was achieved using polarscope and PHD).

[Carole]

Noel, you and Mark would make a couple of bookends when it comes to statistics, are you sure you need to come to imaging sessions.   

Carole

[NoelC]

Sorry; but I'm quite good at tinkering.
Not so good at imaging (yet).

Noel

[The Thing]

Hi Noel et al.

Last night I used the latest version of PHD2 2.6.4dev3 (I think there may be a dev4 now!) to polar align using the static alignment tool (SPA) after the Guiding Assistant said I was 89 arcmin out!!! I can only assume that the previous version of SPA was not quite right. It's now easier to see what adjustments to make, just put the target circumpolar star in the calculated circle (I just used Polaris). I got to within 2.5arcmins in 30seconds and then checked it with the Guiding Assistant and then repeated SPA which showed it was still spot on. I'll check it again next time I image as I am sure my Alt axis moves, the pivot bolt is a lousy fit and the adjustment bolts bend and slip where the put pressure on the casting. Rebuild looming.

BTW I'm using a 75mm fl gudescope at 10arcmin/pixel, a longer focal length would be more accurate for this but at the end of the day my mount is limited by its adjustments which are rough to say the least so I'm happy

HTH

[Carole]

Duncan, I don't have a Polemaster adapter for my NEQ6 which has been on the pier for several years now and not moved, but I do think it is time I re-checked the polar alignment which I originally fine tuned using Alignmaster. 

What version of Sharpcap do I need and is it simple for us mere mortals not so IT/techie minded as yourself?   It would save me buying the Polemaster NEQ6 adapter for what could be a one off or rare use.

Carole

[The Thing]

Hi Carole

With your existing guiding setup you can use either Sharpcap 2.9 which is still free (v3 costs) or phd2 2.4.6dev4 or higher from the beta section on openphdguiding.org. Don't worry it's says beta!

I much prefer the phd2 static alignment method as it's quicker, the mount rotates much less the Sharpcap version which needs a 90 degree movement and has to platesolve at each position which can be hit and miss. Also with the Sharpcap method you have to watch numbers which tell you which way to still need to move after each adjustment rather than just move one star into one circle once.

Hth