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Old 13-07-2020, 03:42 PM
Cyberman (Rob)
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Polar Alignment

Hello, Iím new to this hobby and have lots of questions. I have been mainly doing visual but would like to consider doing some astrophotography. But my first problem is polar alignment. I have read a few suggestions here. I have a skywatcher EQ6R and have been trying the synscan polar alignment method. I was able to get to 30 seconds error in both alt and azimuth early in the evening using Hadar (polar alignment star) and miaplacidus. Beginnerís luck. Later in the evening I used atria (polar alignment star) and Hadar and wasnít able to get better than 1 min 30 sec error in either alt or azimuth after multiple tries. Every time I went back to the alignment star atria, the star was already centred and I could not make further adjustments to alt or azimuth . I can only see the southwest quarter of the sky from where I set up. Is this the best I can do or am I making mistakes? Do I need to update the synscan firmware? Any suggestions would be greatly appreciated, Rob.
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Old 13-07-2020, 03:52 PM
kens (Ken)
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Anything under 5' error is good enough for most situations.
The Field Rotation Calculator is a good tool - field rotation being the main issue with PA error when doing AP.
http://celestialwonders.com/tools/ro...ErrorCalc.html
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Old 13-07-2020, 04:07 PM
Startrek (Martin)
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Rob
Use a star thatís closer to the south meridian line and higher in altitude ( ideally the polar alignment Star should be between 40deg and 65deg in Altitude)
If your using Hadar and Atria ( I used Alpha Centauri or Rigel Centaurus and Atria last week ) use Hadar as your polar alignment Star. Both alignment stars obviously must be on the same side of the meridian
Also are you using Software and laptop to polar align or at the scope using an illuminated reticle eye piece in the focuser ? Either way defocus your alignment Star a little bit into a small donut to achieve more centering accuracy. Anything below 1 arc minute error using the Synscan routine is pretty good. Generally Iím around 20 to 40 arc seconds on both Alt and Az but make sure error on Alt and Az are reasonably close ( not like 1.80 Alt and 0.20 Az )
Sounds like your on the right track
For visual use you only need to get error down to a few arc minutes ( depending on your focal length and magnification) But for imaging you will need to get down to 0.30 to 0.50 arc minutes but not critical as your autoguiding will correct the remainder
Cheers
Martin
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Old 13-07-2020, 04:33 PM
Cyberman (Rob)
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Thanks Ken and Martin,

I will try Hadar as alignment star next time if the clouds ever clear here. I think atria was closer to the meridian last time as they were both just west of south,
thanks, Rob
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Old 13-07-2020, 04:41 PM
Startrek (Martin)
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No problem Rob
Another tip
Donít be concerned about doing up to 3 to 5 iterations to get the error down , on nights of poor seeing it can take up to 6 goes at it to get down below 1 arc minute
Also another tip if you get your error down below 1 arc minute and want to go lower , on your next iteration donít undo the Az or Alt bolts , just try to squeeze and turn the black bolt knob a bit tighter. Sometimes it works and you end up lower other times it doesnít, just give it a try. The bolts on the EW6-R are so chunky that even a squeeze on the bolts changes your Az and Alt by arc seconds
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Old 14-07-2020, 06:43 PM
Cyberman (Rob)
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Thanks ,Martin. I will try that also. I also have a canon 600d and was using its live view with grid pattern to centre the stars. That may not be accurate enough and will have to try a reticule eyepiece. I don't have a guidescope or or guide camera. My telescope is a skywatcher 250 F4. A guidescope might add too much weight to my setup. I have just been trying 30sec to 1min subs, but often get some elongation of my stars. thanks, Rob.
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Old 14-07-2020, 07:14 PM
Startrek (Martin)
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Gee Rob thatís a big scope there, and f4 too which are certainly more difficult to collimate compared to an f5
Any particular reason why you went or this scope for visual ?? This scope is primarily an Astro graph for imaging (it can be used for visual but primarily for Astrophotography with a coma corrector)
This scope on its own without imaging gear ( 15kg) is slightly over weight for Long exposure Astrophotography on an EQ6-R Mount
My EQ6-R carries my 200mm f5 newt and with all imaging gear and dew control etc.. at 14.5kg pretty much on the limit for AP but I can guide under an arc sec and push 5 minute subs ok with precise balancing etc..
If I upgraded to a 250mm Imaging newt I would definitely have to upgrade my mount to something like an EQ8-R pro
I recommend you buy an Orion 20mm 70 degree illuminated reticle eye piece for your star alignment and polar alignment centering, they are a great tool and well worth the expense
I still use mine for alignment on my 12Ē Goto visual dob as they work so well, good optics, nice wide field and plenty of eye relief
Cheers
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Old 17-07-2020, 04:41 PM
appiice (Ed)
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Hello Rob

Sorry to butt in here, my suggestions would be, 1. to buy a licence for Sharpcap, it's 10 pounds a year.
2. A free option would be N.I.N.A., it has a Polar alignment routine ( I haven't used it yet ).

I have found NINA very easy to get a grip with, I'm using a Edge 1100HD with a Hyperstar ( F1.9 )and doing 20 second subs, I have a guide scope but am not using it as the stars are crisp at that exposure time.

Given how easily the rest of NINA works I'll give the PA routine a go soon, I'm only using Sharpcap to do PA's with so if NINA does it easy enough, I'll save my Au$18.00 a year.

Hope this helps.

Ed
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Old 18-07-2020, 10:50 AM
nik_ozskyman (Nishant)
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I have used Polar Finder Pro. Seems to be easy one so far
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Old 23-07-2020, 03:00 PM
Craig_
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SharpCap Pro will make your P.A routine relatively straight forward.
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Old 10-08-2020, 09:21 PM
Cyberman (Rob)
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Thanks Martin, I did try a reticule eyepiece and polar alignment was easier to get under 1 minute. I was able to get reasonably good tracking on most exposures up to 1minute. A few where a bit elongated stars and occasionally looked like double stars. I tried hard to get good balance. If I were to try guiding, I might try off axis as this would probably be lighter. But not sure which OAG or camera would suit. Probably would also need a coma corrector.

Thanks Craig, Nishant and Ed. Iíll look into those programs but I havenít used a laptop yet with the telescope.
Rob
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Old 10-08-2020, 09:46 PM
Startrek (Martin)
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Hi Rob
Yes the illuminated reticle eye piece is a great tool to improve your alignment centering accuracy
If your going to image with a DSLR ( Canon or Nikon ) can I strongly recommend using BYEOS or BYNIKON
Itís a tremendous frame , focus and capture software ( includes Planetary imaging as well ) it also have a drift alignment tool for PA which I use inconjunction with the Synscan ( no more bending my head over an eye piece ), I just sit at my laptop 1.5m away and carry out my Synscan Star and PA alignment with less iterations and more accuracy than the illuminated reticle could ever do. I only get up off my stool to tweak the Alt and Az bolts , with the laptop screen live view only 1.5m away , so easy and comfortable
The accuracy is improved because you can 3 x zoom the Star plus defocus your Alignment stars and PA star into a small donut and really nail the alignment with great accuracy
Iím usually Polar Aligned with 2 or 3 iterations in about 10 minutes

Glad your achieving some tighter PA now

All the best
Martin
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Old 11-08-2020, 11:59 AM
Spidy (Phil)
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Quote:
Originally Posted by appiice View Post
Hello Rob

Sorry to butt in here, my suggestions would be, 1. to buy a licence for Sharpcap, it's 10 pounds a year.
2. A free option would be N.I.N.A., it has a Polar alignment routine ( I haven't used it yet ).

I have found NINA very easy to get a grip with, I'm using a Edge 1100HD with a Hyperstar ( F1.9 )and doing 20 second subs, I have a guide scope but am not using it as the stars are crisp at that exposure time.

Given how easily the rest of NINA works I'll give the PA routine a go soon, I'm only using Sharpcap to do PA's with so if NINA does it easy enough, I'll save my Au$18.00 a year.

Hope this helps.

Ed

Ed, I thought NINA's polar alignment routine only works for the Northern Hemisphere?


Have you actually tried in the South? If so, I'd love to hear your impressions of the feature; easy/hard/accurate, etc.
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Old 11-08-2020, 12:03 PM
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Merlin66 (Ken)
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Guys,
You can use the SharpCap freeware V2.9 for PA.
(The latest V3+ is payware)
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Old 15-08-2020, 04:25 PM
Cyberman (Rob)
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Thanks Martin, Ken and Phil. Is there much difference between classic or premium BYEOS. Rob
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Old 15-08-2020, 08:03 PM
Startrek (Martin)
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From my experience Classic is more than adequate
I think from memory Premium has only a few additional features like a more detailed Histogram which you can adjust / stretch , some Ascom control of focusers and the Capture plan has some additional functionality like deleting a plan with one button
Cheers
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Old 17-08-2020, 11:26 PM
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Swagman105 (Geoff)
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Hi Rob.
I know there is merit in using classical means of polar aligning as a means of understanding the whys and wherefores of polar alignment. I came back to astronomy as an older citizen with poor eyesight, bad neck and back, poor urban seeing conditions and a fair dose of impatience. Whatever skills were I ever to develop in classical PA would always be compromised.
After persevering for a year or so with unsatisfying efforts I decided to splash out and buy a QHY Polemaster and have never regretted it.
Admittedly it is quite expensive but makes the whole exercise so much easier and I am up and running so much faster. As a permanent piece of my gear with the right adaptor it can be transferred across many mounts except that my most recent upgrade, an Ioptron CEM70 mount had their own version called an Ipolar built in to replace a polar scope.
I will be keen to see how the Ipolar and Polemaster compare once I have my new mount set up.
Cheers Geoff
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