Alignmaster + GPS dongle

[chrisshillito]

Can you provide a link please.

Complete Mount & Scope Setup. PART FIVE (Cone Error) - YouTube

(Odd google didn't find it for you -to find it all I did was type "astronomyshed cone error" into google)

Chris

[LongJohn54]

Thank you

John

[pritc]

Nooo.. 3hrs

At least you managed to see stars tonight !

Only Polaris!!

[Starjumper]

Thanks Chris

John

[malc-c]

Just wondering... if you remove the OTA after you have just spent 3 hrs resolving the cone error... then wouldn't you need to check it every time you set up as the dovetail may not be in exactly the same place !

At least for us chaps and chapesses with observatories it should be a one off exercise

[chrisshillito]

Within the contect of achieving perfect polar alignment with alignmaster yes, you would need to check your cone error each time you re-assemble - hopefully it won't change too much. Of course you may discover that you really don't need perfect alignment and that near enough is good enough in many cases (certainly for bright objects around the pole etc.)

Chris.

[MG1]

Chris, I've spoken to OV who have agreed to contact the factory regarding the dimension of the circles in the reticule. They have suggested that we should hear back early next week.

Michael

[malc-c]

Well that was an interesting few hours...

Took advantage of the 1st clear night we've had in ages to try out Alignmaster. With everything up and running I loaded up the tutorial video and used it as a walk through, pausing it as and when required.

First problem... my observing site is fairly limited in views to the west and north, partly due to houses, but also to the fact that the walls of the observatory restrict how low an object is that I can view. Hence most of the second stars of the pairs were obscured. I finally manged to find a "best" pair of Vega and Mizar.

Vega was easy to locate and was centred using the cross-hair option is sharpcap. Then it was off to Mizar.... problem number 2. Whilst Mizar was just above the observatory wall, and would be visible in the main scope, the finder was low down and thus looking at the wall. I therefore removed the web cam, inserted a wide field eyepiece and used the gamepad to place it centre in the FOV. I then replaced the eyepiece with the webcam, re-focused and then having seen it on screen, used EQMOD's NSEW buttons to centre Mizar on the cross-hair in Sharpcap. So far so good !

Right, now confirm the option in Alignmaster to adjust the Azimuth... only unlike the video, Mizar shot off way out of the field of view - I managed to find it using just the azimuth bolts I centred it on the cross-hair. Then confirmed the Alt option and again Mizar shot out of view, but not as much...... problem number 3... Expecting Alignmaster to move the mount North / South so that adjusting the altitude bolts brought it back to the cross-hairs, it actually moved it up and across in two directions... result was I had no option but to use both the azimuth bolts and altitude bolts to centre it back on the cross-hair - something that the video tells you not to do.

I then chose to run through the process again using the same pair of stars, but was pleased to find that the goto this time round was almost spot on when slewing back to Vega, and then on to Mizar, so I didn't have to faff around with swapping the eyepiece an webcam like the first time. Again, whilst setting Azimuth, I could re-centre the star using just the azimuth bolts, but on Alt the mount moved slightly in both Azi and Alt, why I have no idea as the mount is perfectly level. However as the Error corrections stated by Alignmaster was 00000 for DEC and what looked like a few arc seconds for RA I chose to leave it as it was to see what difference it made.

Well I'm pleased to say the goto accuracy through CdC and EQMOD is now what I expected... I selected NGC7331, M27, M45, and a Jupiter All were in the dSLR's field of view I then booted up PHD, and tried some tracking. I really need to tweak the calibration settings again, but whilst the graph wasn't smooth, most of the results PHD displayed were near or below that magical 25 value.

Conclusion:

It works and works well..... I was amazed at how far out my alignment was. I would like to of seen more choice of alignment stars for those like me have limited views, but then maybe that will happen in a future release. Oh and yes it's well worth the few quid the license costs, and will be a bonus for setting up in the field, assuming you have a laptop controlling your scope.

[MG1]

Great write up Malcolm. Thanks.

I didn't have much luck with the clouds tonight. Managed to get set up and aligned in around 2hrs of clear sky (laptops playing up) but then only had around 30mins before it became cloudy.

Stuck at it for a few hours but have given up for bed.

[malc-c]

Interestingly, I've received a PM from another member who experienced the same issue with the alignment of the ALT setting in that BOTH the ALT and AZ bolts have to be moved to re-position the star back on the cross-hairs.

Time to drop Dion a PM and see if he can do an update with a live view tutorial

[MG1]

Is this requirement to make adjustment in both az and alt a symptom of the mount not being 100% level?

And if so, what are the implications when it comes to adjustment?

I guess this also applies to standard drift alignment techniques?

[malc-c]

Having received a PM from Dion your assessment is 100% spot on. The issue would seem to be based on the tolerances built into the spirit level when leveling the mount / adapter.

Visually, using a decent spirit level, my adapter was spot on. But obviously at the magnification the web cam produced, the inaccuracy made it self known

[malc-c]

OK guys and gals,

I've attached an image to show you the mount adapter and the result I had in Sharpcap when I clicked the confirmation button for ALT in alignmaster.

In order to move the star left and bring the star across to the centre, I assume I need to adjust bolts B and C and then use the latitude bolts on the mount to drop the star down ??

[pritc]

OK guys and gals,

I've attached an image to show you the mount adapter and the result I had in Sharpcap when I clicked the confirmation button for ALT in alignmaster.

In order to move the star left and bring the star across to the centre, I assume I need to adjust bolts B and C and then use the latitude bolts on the mount to drop the star down ??

So when doing ALT adjustment you ONLY move the ALT bolts and make any other off centre adjustments with the Pier adaptor level??

And the same goes for Azimuth adjustment......

Is this right Malcolm??

Wayne

[malc-c]

Wayne,

That's how I interpret the statement. So when selecting the AZ correction, use the longitude bolts on the mount to bring the star over to the centre, then correct any "vertical" alignment using the pier adapter bolts. Then select the ALT correction, and used the latitude bolts on the mount to bring the star down in line with the cross hair intersection, and then use the pier adapter bolts to level up the horizontal movement :)

Dion also reminded me that you need to change a setting in EQMOd so that it doesn't make any corrections which would then give false error readings !!!

At least it's looking promising for another clear night tonight so I'm planning on running through the procedure again... no doubt I'll much things up even more than they are now !!

[pritc]

Wayne,

That's how I interpret the statement. So when selecting the AZ correction, use the longitude bolts on the mount to bring the star over to the centre, then correct any "vertical" alignment using the pier adapter bolts. Then select the ALT correction, and used the latitude bolts on the mount to bring the star down in line with the cross hair intersection, and then use the pier adapter bolts to level up the horizontal movement :)

Dion also reminded me that you need to change a setting in EQMOd so that it doesn't make any corrections which would then give false error readings !!!

At least it's looking promising for another clear night tonight so I'm planning on running through the procedure again... no doubt I'll much things up even more than they are now !!

You have to select 'Dialog mode' in EQMOD to stop any corrections.

So it certainly offers near 100% alignment if it takes out any pier mis-levelling......

I presume that with a tripod set up, you would adjust the independent leg heights to centre alignment.

A bit more awkward than a pier set up.

Wayne

[chrisshillito]

Dion also reminded me that you need to change a setting in EQMOd so that it doesn't make any corrections which would then give false error readings !!!

But Malcolm you surely knew that already - we did discuss it in detail on page one of this thread

Chris.

[pritc]

At least it's looking promising for another clear night tonight so I'm planning on running through the procedure again... no doubt I'll much things up even more than they are now !!

Fingers crossed for clear skies here tonight.

Got to treat SWMBO with a restaurant meal first......

KFC should do ....... (Not really)

Then to start over aligning again, and hopefully get Alignmaster nailed tonight!!

Wayne

[malc-c]

But Malcolm you surely knew that already - we did discuss it in detail on page one of this thread

Chris.

I'm sure I did as I also cleared any previously stored alignment points... just having a senior moment as I can't confirm if I changed this... even after your post

I've since received a PM from Dion, and I hope he won't take offense if I post it hear as it's in keeping with this thread

What I did, imagine the column mount and it's 3 feet, I make sure one of the feet is to either north or south, meaning technically, it does the same as the alt bolt on the mount (up and down) I aligned the camera so that any movement on screen makes sense with the reticule , if using an eyepiece, simply rotate it so that the directions make sense to you)

Next, do an alignmaster setup and when at the az setting, use the mount ax bolts to bring the star as close as possible to center, so that now, only alt would center it, then, center it using that adjuster foot on the mount, so in your case, from what I can see, that would be whichever bolt/s mimick alt movement.

Next, close alignmaster without completing the alignment, send mount back to home and try again, this time you 'should' find that in the az setting part, it should center by just using the az bolts on the mount, as in effect you've corrected the error previously. Next, when it comes to making the alt adjustment, if you can't center by just using alt, use the pier bolts that mimick az movement, probably a bit of guesswork here, ie move a bolt a tiny bit and see which way star moves.

Again, par mount, close alignmaster and start again, each time you do it, you 'should' find that the discrepancy is less. When it's only a tiny bit out you can always cheat and just give the alt or az bolts a tiny tweak when aligning.

Wayne... KFC.. that's a bit sophisticated, local chippy might be quicker

[chrisshillito]

Having received a PM from Dion your assessment is 100% spot on. The issue would seem to be based on the tolerances built into the spirit level when leveling the mount / adapter.

The "problem" is Alignmaster is trying to measure and amply movement in Alt and AZ on an equatorial mount that can only move in RA and DEC. At each stage of its calculations, and prior to issuing the slews used for correction, it must therefore convert between RA/DEC and Alt/Az. For these calculations/movements to be accurate the mount must be level, the site coordinates must be accurate and the PC's time must be accurate (and of course no cone error as previously discussed).

When we experimented with the original EQMOD polar alignment routine (now hidden) we compensated for a non level mounts but this significantly added to the complication of the overall process. Six alignment points were needed, three points triangulating the positions actually used for the alignment calculations. Ultimately its a far easier process to just assume the user has leveled the mount and, if they haven't, home into true alignment by doing multiple iterations such as Alignmaster recommends!

Chris.

[malc-c]

Chris, Thanks for the explanation.

I've now physicked myself up to completely run through the setting up of my mount from scratch tonight (still clear - can see Jupiter through the lounge window). This includes running through cone error, which a think might be contributing to the error as well.

I guess the only true way to ensure the adapter is perfectly level, other than star alignment is to use one of those digital spirit levels !!

[pritc]

Malcolm,

That makes sense now...

Thanks for posting Dion's reply.

One of my pier adaptor adjustment bolts faces North, so adjusting that will compensate for any Alt error in Az.

And to think I spent AGES levelling my pier adaptor,I thought it was perfect...........

Wayne

[MG1]

Following this and various other threads both here and elsewhere, I'm beginning to think that what might be handy is a definitive matrix of user interactions, mechanical characteristics and environmental conditions that impact on our ability to polar align accurately and then to track accurately.

This might help people to understand the relative impact of various tweaks, the futility of some actions and also to gain both a sense of perspective and set some realistic targets for the fettler (like myself) to aim for.

Just a thought...and maybe one for another thread?

[chrisshillito]

I guess the only true way to ensure the adapter is perfectly level, other than star alignment is to use one of those digital spirit levels !!

Personally I wouldn't worry about it too much. After all it may be quicker and easier to just run alignmaster 3 or 4 times in succession (or just drift align if its a do once operation on a permanently sited mount) than mess about getting a perfectly level mount that won't actually benefit your practical astronomy.

Chris.

[chrisshillito]

For those folks who haven't already seen them take a look at Frank Barrett's series of articles on polar alignment.

On Polar Axis Alignment

Also if you want to know how to write your own "Alignmaster" then see Ralph Pass' article on two star polar aligning http://www.rppass.com/align.pdf

Chris