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Alignmaster - what am i doing wrong?


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With a recent increase in FL and exposure times guiding out dodgy PA is causing field rotation so rather than time-consuming drift alignment I decided to try Alignmaster.

This is what i tried:

Level the tripod.

Polar align the neq6 as best as i can using my carefully calibrated RA setting circle and the polar align app.

Start up CdC and connect to the mount (over EQTooth)

Start up alignmaster and carefully enter position.

LMST checked.

Pick two stars from the 'best' list (deneb & mizar last night).

'Goto' deneb and centre deneb on the camera sensor using the NSEW controls on the ascom panel.

'Goto' mizar and do the same.

So far so good.

Then it prompts to calibrate AZ - so i got ahead and there is a second or so of slewing.

I then try and use the az bolts to re-centre mizar but although i can get it back on the sensor it's nowhere near the centre.... i would have needed to adjust the alt bolts too to get it centered.

I tried just getting it back as close to the centre as i could then doing the same for alt but the PA was miles off.

Tried this on a couple of different star combinations with the same result.

I'm obviously doing something stupid but i cant figure out what  :)

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It is probable that your problem is down to you using CdC and presumably EQASCOM to slew to the star.  The instructions say Disable any multi-star approximate alignment controls and connect the telescope mount to the computer.

You really need to let Alignmaster control the slewing and Use the handbox of the Goto mount to center the first star in the ocular cross-hairs

That way, Alignmaster is aware of where it positioned the scope i.e. it knows the RA and Dec but also knows how much you had to correct it by.  It can then construct a slew that corrects the AZ alignment error when you adjust the star back to the centre with the bolts.  Likewise for the ALT adjustment with the second star.

Hope that helps a bit.

Mike

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Thanks Mike that makes sense.

I'm now slightly puzzled how i would manually control the mount without using eqascom...

I use alignmaster to do the slewing but then to do the small adjustments to centre the star i need to use eqascom or somehting? i can't connect the synscan handset and the PC at the same time..  hmmm

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It can take a few iterations of Alignmaster, using the same pair of stars, to get good PA. It might just be that your original PA really was a long way off? Make sure that you only adjust the AZ bolts when adjusting for AZ and ALT when adjusting for ALT. Just get the star as close to the centre as possible. I find that after a couple of iterations the adjustments with the bolts will bring the star ever closer to the centre anyway.

Good luck!

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Thanks Mike that makes sense.

I'm now slightly puzzled how i would manually control the mount without using eqascom...

I use alignmaster to do the slewing but then to do the small adjustments to centre the star i need to use eqascom or somehting? i can't connect the synscan handset and the PC at the same time..  hmmm

I have always used the control panel in the EQMod window with no problem. As you say, the handset is in PC Direct mode so can't be used for slewing.

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It can take a few iterations of Alignmaster

ok - maybe I'll try a few more iterations - after a couple it just seemed to be getting worse....

My initial PA isn't 'bad'  --  the polar scope is pretty carefully collimated to the mount and the RA setting circle is set up carefully. Before starting i can fire off 1min unguided subs @ 1300mm FL and they look OK.

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I think you can use EQASCOM to nudge the star into the centre but you need to make sure your Align Data is cleared - there's a button under Alignment / Sync.  Its possible I am wrong but I think that data is a mapping between RA/Dec and the position of the "cogs" within the mount.  That is the part that will confuse Alignmaster.  The table is only updated when you sync.

PhotoGav is correct re taking iterations to get good PA but I've found that even simply using a compass for azimuth and relying on the mount's altitude still being more or less correct from the previous time I used it, just one iteration gets me close.

Incidentally, PHD2 has a drift alignment wizard that you could also consider trying (I've not tried yet but it looks interesting).

Mike

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I had sort of the same problem when using skywatchers own polar alignment routine within the handset. I figured out the problem though, my alt bolts slipped a bit while adjusting az (or randomly during the evening) even though I replaced my bolts with a better quality ones.

I did the 'Gunnar mod' and now it's all rock solid.

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Cheers Baffa - the 'Gunnar Mod' looks like a good upgrade (esp if you're a bit further north and need to point lower at polaris!) but i dont think that's my problem. I've got an upgraded ratchet alt bolt and i've never known it to slip.

Just been over all my alignmaster setting again and it's all fine....   maybe it is a case of clearing out my align data.

Forecast clear for tomorrow so will have another try

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Well tried it last night - just ran alignmaster before starting CdC or anything else and everything worked fine - got v accurate polar alignment after 3 iterations.

I think MikeP was probably right that CdC (or something else I happened to have running) had align data in it that was confusing things.

Thanks all.

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Thanks!

yeah -stunning - one of the best nights for ages - was imaging dumbell neb and the data looks great. Was scanning with the binos/naked eye while the imaging rig was running and I think it was the clearest night this year. The fact it rained all day helped i think!!

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I normally use Alignmaster for PA on a tripod, but when I put my pier in last year I could not get "perfect" alignment. I then read that unless the base is totally level, Alignmaster can miss a bit - my pier head adjustment was still a bit less than a degree off level after constant fiddling. So I used the PHD method and got spot on.  See the posts at http://stargazerslounge.com/topic/81943-phd-drift-polar-alignment/

Allan

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I've tried AlignMaster on the Obsy mount a couple of times & still been out unable to get more than a couple of mins subs without trailing. EQMod needs to be in "dialog mode" not append on sync BTW. Even setting by eye using the polar scope gets me 900 s subs ok.

So far my best PA is using EQMOD 's polar alignment method.

Would be nice to get A M working though as it does seem to work for others & I like the simplicity of using the app without touching the scope/CCD setup.

Sent from my iPhone using Tapatalk

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I normally use Alignmaster for PA on a tripod, but when I put my pier in last year I could not get "perfect" alignment. I then read that unless the base is totally level, Alignmaster can miss a bit - my pier head adjustment was still a bit less than a degree off level after constant fiddling. So I used the PHD method and got spot on.  See the posts at http://stargazerslounge.com/topic/81943-phd-drift-polar-alignment/

Allan

Thanks - yes I levelling my tripod with a small spirit level but i doubt it's amazingly accurate - I will definitely give the PHD method a go.

I've tried AlignMaster on the Obsy mount a couple of times & still been out unable to get more than a couple of mins subs without trailing. EQMod needs to be in "dialog mode" not append on sync BTW. Even setting by eye using the polar scope gets me 900 s subs ok.

So far my best PA is using EQMOD 's polar alignment method.

Would be nice to get A M working though as it does seem to work for others & I like the simplicity of using the app without touching the scope/CCD setup.

Sent from my iPhone using Tapatalk

Thanks - that's interesting - I think I've got the hang of EQMod (and other software) not interfering with A M!

Which of your fine range of scopes are you getting 900s subs with just setting by eye? If it's the c9.25 I'm v impressed :)

Will certainly try the EQMOD PA routine if you reckon it's the most accurate.

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Hehe.. I wish. No not the C9.25, I've got the Esprit 80 & the GT81 on there in a side by side at the moment.

I went through the EQMod PA last night. I'm going to check it again with Alignmaster to see if I can work out why it gives me so different results. I don't like to be beaten.. or at least I like to know why I've been beaten :laugh:

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