Drift alignment and 3 Star alignment

[nsavage (Nick)]

Hi,

Sorry I realise in advance that this is quite the amateurish question. I am still getting the hang of polar and drift alignment (very almost there) however the next part that puzzles me (and is often not mentioned in the drift alignment guides) is whether I should be doing a 3 star alignment as well and at what stage. I am using PHD for the drift alignment and I am connecting to the mount using EQMOD. I assume you can do a 3 star alignment with EQMOD as well is that right?

Appreciate the assistance

[Startrek (Martin)]

Nick
EQMOD does have a polar alignment feature which requires the use of your polar scope ( I don’t use this )
As far as star alignment for Goto functions , EQMOD has a sync based algorithm in its pointing model when used through your planetarium ( Stellarium or Cartes du Ciel etc... )
The 2 algorithms available are 3 point plus nearest and nearest point which you can select
I use 3 point plus nearest which is excellent
It would be helpful for you to read up on EQMOD
The manual is available on their website
www.eq-mod.sourceforge.net
Don’t know if this answers your enquiry

[nsavage (Nick)]

Originally Posted by Startrek

Nick
EQMOD does have a polar alignment feature which requires the use of your polar scope ( I don’t use this )
As far as star alignment for Goto functions , EQMOD has a sync based algorithm in its pointing model when used through your planetarium ( Stellarium or Cartes du Ciel etc... )
The 2 algorithms available are 3 point plus nearest and nearest point which you can select
I use 3 point plus nearest which is excellent
It would be helpful for you to read up on EQMOD
The manual is available on their website
www.eq-mod.sourceforge.net
Don’t know if this answers your enquiry

It certainly does to a point.

So am I correct in assuming that I should perform a drift alignment first and then follow with one of the star alignment options?

[Startrek (Martin)]

I don’t use PHD2 drift alignment so can’t comment on that procedure
Don’t get confused between Polar Alignment ( Drift or other methods ) and Star Alignment , they are 2 different things
Polar alignment adjusts your mount in Altitude and Azimuth to align or centralise your mounts axis with the polar axis
Star alignment is used so your mount has a pointing model of the night sky ( via 1, 2 , 3 or more alignment stars ) and can Goto selected targets by use of a hand controller, or planetarium software
In some Polar alignment routines , Star alignments are used to plate solve or map the polar alignment Star ( eg Synscan Polar Alignment routine using hand controller. This is what I use )
Hope the above makes sense
Maybe some others can comment and explain further

[RobF (Rob)]

Originally Posted by Startrek

I don’t use PHD2 drift alignment so can’t comment on that procedure
Don’t get confused between Polar Alignment ( Drift or other methods ) and Star Alignment , they are 2 different things
Polar alignment adjusts your mount in Altitude and Azimuth to align or centralise your mounts axis with the polar axis
Star alignment is used so your mount has a pointing model of the night sky ( via 1, 2 , 3 or more alignment stars ) and can Goto selected targets by use of a hand controller, or planetarium software
In some Polar alignment routines , Star alignments are used to plate solve or map the polar alignment Star ( eg Synscan Polar Alignment routine using hand controller. This is what I use )
Hope the above makes sense
Maybe some others can comment and explain further

+1
So even if your pointing model allows your scope to slew to the target, without decent polar alignment, the scope will have to constantly track in both RA and continuous DEC to keep the object in the FOV, however there will also be rotation of the object (unless you employ some sort of de-rotator).

When the scope is properly PA'd, only RA movement should be necessary with very minimal DEC corrections, and negligible field rotation....

[nsavage (Nick)]

OK so maybe I did not articulate my question very well.

I know why a polar alignment or drift alignment is and why it is used and I know what a 3 star alignment (or similar) is and why it is used.

I understand that for imaging good polar alignment is required and that a lot of people use drift alignment to gain a more accurate polar alignment. What I am unsure of is whether a 3 star alignment is necessary for imaging and if so at what stage of the setup process would it be performed.

[mynameiscd (Andy)]

Hi Nick,
I have the same questions well.
Heres my routine
Do a rough visual polar alignment.
Then a 3 star just to help to find stars for focusing etc.
Then turn on sidreal tracking and do a full drift alignment
Then do another 3 star alignment.
Dont know if its the correct process but it seems to work for me.
Cheers
Andy

[doppler (Rick)]

3 star alignment is just for your goto to improve pointing accuracy. If your polar alignment is out the goto will still work but the image will slowly drift in the dec axis (for visual and when only tracking), guiding will be working hard to keep up and you will get field rotation in long imaging sessions.

Good polar alignment is needed so your mount doesn't need to make a lot of adjustments to the dec axis so you get smoother guiding and sharper stars.

[redbeard (Damien)]

,

Originally Posted by doppler

3 star alignment is just for your goto to improve pointing accuracy. If your polar alignment is out the goto will still work but the image will slowly drift in the dec axis (for visual and when only tracking), guiding will be working hard to keep up and you will get field rotation in long imaging sessions.

Good polar alignment is needed so your mount doesn't need to make a lot of adjustments to the dec axis so you get smoother guiding and sharper stars.

Hi,

After you have polar aligned, you then do the 3 star alignment. The reason for doing the 3 star alignment is so your scope will find objects by using its goto system. If you don’t do the 3 star..... then you will still be fine to image, it’s just the object will be harder to initially find without accurate goto.

Cheers,
Damien

[Startrek (Martin)]

Nick
If your mount is controlled by EQMOD you should take advantage of its capabilities and use a free planetarium software ( like Stellarium or Carts du Ciel ) to navigate across the night sky
With EQMOD you not need to do a mandatory 3 star alignment to align your mount to the night sky
I usually align and sync to the first star and my pointing accuracy is good enough to slew to objects after that , just minor adjustments to centre objects
Obviously the more stars you sync , the more accurate the Goto and centering becomes
EQMOD is an extremely accurate tracking , Goto and pointing system when coupled with your planetarium
Cheers

[nsavage (Nick)]

Awesome - thanks for that everyone.

I am currently using Cartes du Ciel with EQMod and thinking about installing Stellarium as well (Stellarium seems a bit easier when starting out although I am getting the hang of Cartes du Ciel now).

[RobF (Rob)]

Actually depending on your software, if you're a diehard imager you'll soon reach the point of not ever doing 1, 2 or 3 star alignments. Most modern astrophotography software will incrementally adjust your pointing to your chosen target through plate solving.

You can do a single alignment at the start of the night, but its not really necessary. Most packages will fail over to a "blind" solve if the inital field solve fails.

Mastering plate solving is an awesome step up and definitely something to start playing with if you haven't already.

What software are you using for data collection currently?

[nsavage (Nick)]

Originally Posted by RobF

Actually depending on your software, if you're a diehard imager you'll soon reach the point of not ever doing 1, 2 or 3 star alignments. Most modern astrophotography software will incrementally adjust your pointing to your chosen target through plate solving.

You can do a single alignment at the start of the night, but its not really necessary. Most packages will fail over to a "blind" solve if the inital field solve fails.

Mastering plate solving is an awesome step up and definitely something to start playing with if you haven't already.

What software are you using for data collection currently?

I was watching a video where plate solving was used earlier tonight and immediately realised that that was the direction to look to move towards as it appeared to significantly speed up the process of getting going.

So far I only have SharpCap Pro. I am guessing the next step is to look at plate solving integration with something like AstroTortilla?

It has taken me a considerable time to get going to be honest.

I bought a 200PDS and mount initially and went straight to an OAG. This only caused frustration and I quickly found excuses to be busy doing other things and therefore did not invest the amoutn of time in to the hobby. I recently bought an ED80 scope and even then found that getting use to the OAG was not easy so I went ahead and bought a 50mm Guidescope as well.

The first night with the guidescope was like night and day compared to the OAG. For the first time I got a proper polar drift alignment done with PHD2. I then moved to try and do a drift alignment for practice however By that time I got to that stage however it was too late to continue. Since then it has been cloudy most nights which is mess than ideal. I am confident now however that the next night I get out I will actually capture some images. Hopefully that will be this weekend however we are in the throes of preparing to move house so that may eat in to my free time.

A huge lesson learnt in biting off more than one can chew though. The 8 inch reflector is a big scope and a challenge in itself, throw in trying to learn how to use an OAG as well as all of the software etc. and it became extremely overwhelming extremely quickly. I did get very close with the reflector in hindsight however the frustration was enough to set me back mentally for a while.

Next challenge is going to be how small the yard is at the new place and I am still not sure if I will be able to see the southern pole but now that I have the basics down and an idea of how to get the drift alignment done that is not much of a concern anymore. Another advantage of the small yard is that it will encourage us to get out more and head to some nice dark sites (we are lucky as we are relatively close to dark skies here in Adelaide).

[Sunfish (Ray)]

If you are looking to integrate ASCOM control with Stellarium or Cartes du ciel read this tutorial first. Makes it all very clear. You may need Stellarium scope also.

https://www.lightvortexastronomy.com...s-du-ciel.html

Plate solving is integrated in Sharpcap if you have Plate solving installed. Although it has not worked for me yet , it is well down the list of priorities.

[nsavage (Nick)]

Originally Posted by Sunfish

If you are looking to integrate ASCOM control with Stellarium or Cartes du ciel read this tutorial first. Makes it all very clear. You may need Stellarium scope also.

https://www.lightvortexastronomy.com...s-du-ciel.html

Plate solving is integrated in Sharpcap if you have Plate solving installed. Although it has not worked for me yet , it is well down the list of priorities.

I have Cartes du Ciel talking to ASCOM etc. that was pretty easy to set up. Have not setup Stellarium yet although that seems pretty straightforward as well.

[Startrek (Martin)]

Nick
I can send you a procedure to set up Stellarium with EQMOD using Stellarium Scope ( this is the correct way ) Stellarium by itself using “plug ins” is limited in its function and operation of Goto
NB: the Vortex Astronomy way is not entirely correct in certain areas and is missing some vital information particularly with drivers
Let me know
Martin

[nsavage (Nick)]

Originally Posted by Startrek

Nick
I can send you a procedure to set up Stellarium with EQMOD using Stellarium Scope ( this is the correct way ) Stellarium by itself using “plug ins” is limited in its function and operation of Goto
NB: the Vortex Astronomy way is not entirely correct in certain areas and is missing some vital information particularly with drivers
Let me know
Martin

That would be greatly appreciate thanks Martin

[The_bluester (Paul)]

One thing to be aware of (I have seen people chase issues if they do not realise this)

No matter what sort of star alignment you do. One, two or three star via a hand controller, sync on a star in Stellarium etc. If you do that alignment to make the scope point automatically and then drift align or move the axis alignment by any other means like a Polemaster (You don't need to do a star alignment before using a Polemaster but I have seen it done) make sure to redo your star alignment after you have done that.

If you don't you will chase goto errors until you do it as it aligns the mount electronics to where the sky was before you moved the mount.

[Startrek (Martin)]

Hi Nick,
Here’s the procedure ( if you don’t use a DSLR to image then ignore that section )

EQMOD and Stellarium
(Using Stellarium Scope as the interface platform)
Telescope Control for Synta mounts eg: Skywatcher HEQ5, EQ6 and EQ6-R mounts
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Please find below and attached documentation to get you up and running with EQMOD telescope control
*
Note 1: If your using a DSLR, I strongly recommend you buy and download Backyard EOS ( Classic Edition ) from O’Telescope Canada as it will allow easy use of EQMOD and more importantly more accuracy with Polar Alignment, Star Alignment and Goto ( you can control everything from your laptop position – the only time I get up of my butt is to check location of the first alignment star in my finder scope to bring it into view on BYEOS and adjust the AZ and Alt bolts on my mount for PA ) You can also use Cartes Du Ceil planetarium software or any other that supports EQMOD but I prefer Stellarium as its extremely good and easy to use and navigate
Note 2: The information I provide is based on “my set up” using my HP Omen Laptop PC running Windows 10 Home version ( Not to sure about the set up if your using a MAC ?? )
*
Software Required
Ascom ( ascom-standards.org )** Ascom Platform 6.4SP1* latest *( Free )
EQMOD (eq-mod.sourceforge.net )* Eqmod version dated 14/5/18 *( Free )
Stellarium Scope ( welshdragoncomputing.ca ) latest release dated 26/12/16* ( Free )
Stellarium* (stellarium.org )* version 0.18.2* ( Free )
Note : Above software versions may have been upgraded since I wrote this procedure always use the latest
Shoestring Astronomy Virtual Com Port ( VCP driver for FTDI chip )* for your Bintel ( Shoestring Astronomy) USB2EQ5 cable ( www.shoestringastronomy.com ) This is the most important item and allows your Laptop to find and connect to the mount .Hopefully your operating system is on the list for the VCP driver ( Go to The Shoestring Astronomy Store then downloads then Virtual Com port drivers for USB2EQ5 ( VCP Driver for FTDI devices ) your USB2EQ5 cable has a FTDI device in the USB end
If your using a Canon DSLR, Backyard EOS for Canon Cameras ( www.otelescope.com ) latest version* ( Costs about $65 + exchange rate etc.. *they send you licence to install within 24 hours )
Canon driver for your Canon EOS camera ?? If your Camera wont connect, BYEOS can tell how to install driver etc..( as long as your camera was manufactured after 2007 it should be OK )
Cables Required
Mount ( Synscan handcontoller port ) to Laptop – USB2EQ5 cable ( available from Bintel ) you will also need a 2m or 3m USB2 extension cable as the USB2EQ5 cable is only 1.8m long
If using a DSLR ( DSLR to Laptop ) 5m USB2 ( A to Mini B 5 pin ) *cable
*
Synscan Polar Alignment and 2 Star Alignment
As I have no view of SCP at both my Sydney and South coast locations so I still use the hand controller to perform 2 star alignments and the Synscan polar alignment routine ( after 2 or 3 iterations I can get down below 15 arc sec error which is pretty good. This is because I use BYEOS, defocus the star into a donut and set my polar alignment tool in BYEOS with the exact cross hair width and nail the star to perfect centre each time ) Process takes me between 15 and 30 minutes depends on seeing conditions.
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EQMOD Set Up and Goto Procedure
Once Software is down loaded and drivers are established here is the basic procedure* -
1/ Ensure you set up and run Stellarium a couple of times ( this creates the initialization files to allow the systems to work )
2/ Park Scope, switch off mount and disconnect Synscan hand controller ( if you still use Synscan HC *to Star align and Polar align )
3/ Connect the USB2EQ5 cable RJ45 plug end into hand controller port on mount then plug the other end which is USB into a 2 meter long USB2 extension cable , then connect this to your USB port on your laptop
4/ Switch on your mount ( Very important – I sometimes forget and wonder why my Com port wont connect )
5/ Check USB serial cable virtual com port (VCP) appears in Device Manager of your Laptop under Ports ( Com and LPT )
6/ Open Stellarium Scope and click on “Select Mount” button. This launches the Ascom Telescope Chooser Box window ( move the Stellarium Scope window over to the right hand side )
7/ Select EQMOD Ascom EQ5/6 then click “Properties” and then “OK” the *Ascom Set Up window now appears
8/ In the Ascom Set Up window enter your location data in the “Site Location” section ( this must exactly correspond to the data entered in the Stellarium *location window )
9/ In the Ascom Set Up window ensure “Mount Type” is Synta EQ
10/ In the Ascom Set Up Window ensure EQMOD Port details are – Time out 1000 , Retry 2 , Baud 9600
11/ In the Ascom Set Up Window leave all other settings as default
12/ In the Ascom Set Up Window click on the Port Button ( Binocular icon ) if port and driver are located , the word “Found” appears and the Com port number ( same as com port number in Device Manager in Laptop ) appears in the red box
13/ In the Ascom Set Up Window click “OK” at bottom
14/ In the Stellarium Scope window click the “connect” *box button and the EQMOD HEQ5/6 window will be launched. Minimize Stellarium Scope but do not close it otherwise you will close EQMOD
15/ In the EQMOD HEQ5/6 window click on the “Spanner’ icon to expand the whole EQMOD window and then check the “Site Information” section again to ensure it corresponds with the Ascom Set Up window and Stellarium location window
16/ In the EQMOD HEQ5/6 window Alignment/Sync section ensure User Interface is set to *“Append on Sync” , Alignment Behaviour is set to “ 3 Point + Nearest Point” , Point Filter set to “All” and 3 point Selection is set to “Best Centre” All other settings are default
17/ Click on the “spanner” icon again which minimises and just leaves the smaller EQMOD control pad window ready to use the slew control buttons, tracking and parking the mount
18/ Maximise Stellarium Scope which should read at the bottom “ Scope Connected ” then minimise it again for convenience but don’t close it.
19/ Open Stellarium and your ready to use the Goto functions via your laptop keyboard which is CTRL 1 for slewing , CTRL 3 for Sync and CTRL 5 for cancel
Note : For better Goto accuracy use EQMOD, Stellarium and BYEOS *
In Stellarium use at least 3 or 4 sync points ( Stars ) surrounding and in the vicinity of your intended imaging target ( you don’t have to be really close , I’ve used stars 30 to 40 deg away and its works fine but as close as you can )
Click on the 1st sync point star, press CTRL 1 on keyboard ,mount will slew to that star but not exactly centred, centre your star using EQMOD slew control buttons and view in BYEOS then hit CTRL 3 on keyboard. Star will be re centred automatically and a sync point count will appear in the EQMOD window. Note: you may have to minimise the EQMOD control pad window first and then press CTRL 3 to allow the sync function to work properly.
Repeat process for another 2 or 3 sync point stars surrounding the vicinity of your intended imaging target, then click on your intended target , the Goto accuracy should be very good if not bang on target
The above seems like a long winded procedure but after a while you get quicker and quicker ( much quicker and more accurate than your hand controller could ever achieve) The more sync points you use the more accuracy you achieve but I have found 3 or 4 to be enough ( The hand controller can only use 2 or 3 stars for limited accuracy , where as EQMOD can use 3, 6, 10 , 20 or more syn point stars with more sophisticated algorithms in a triangulation or trapezium format.
I have EQMOD control pad window open, Stellarium window open and BYEOS window open ( Stellarium Scope is always open and minimised ) and I minimise between Stellarium scope and BYEOS to perform the Goto* as my Laptop has only a 15.6” screen
I would recommend you set up and play around with Stellarium for a while and get use to it before jumping straight into EQMOD ( I used it to navigate the night sky for a year or so *before jumping into EQMOD )
Stellarium Time Settings (version 0.18.2 )
Found in Chapter 4 ( The User Interface ) of the Stellarium User Manual
Setting Your Location in “Location Window”
Eastern Standard Time
Time Zone should be UTC+10
Tick Custom Time Zone
Untick enable daylight saving time
*
Daylight Saving Time
Time Zone should be UTC+11
Tick Custom Time Zone
Tick enable Daylight saving time
Main Screen “ Configuration” Spanner icon
Click on “Time”
In Start up date and time click on bullseye System date and time
*
Stellarium Location Setting
Refer Chapter 4.2
You can set multiple locations as your default ( I have 2 set up , so I just click on either location in the huge alphabetical world list and the location info is all set up for me
For more information read the EQMOD Project website, Stellarium Scope website and Stellarium website
Hope this gives you a good head start on this great software and telescope control
Good luck and enjoy
Regards
Martin
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[Sunfish (Ray)]

Yes Martin that is a very comprehensive list and much more detailed than the Light Vortex tutorial which does miss a few issues for Stellarium, as I think it concentrates on Cartes.

Well done and great tips.

Stellarium and Stellarium scope does work very nicely on Ascom for me with HEQ5 , PHD , Sharpcap and Nebulosity once I had the EQmod cables drivers , etc etc. so well worth the effort.

I will have to see why my Plate solving in Sharpcap is unhappy . Finds the installed plate solving and has a whirl but no result. Perhaps I just need more ram