29 replies to this topic

[thesti]

Hi,

 

I am new to AP, and just got my gear not long time ago. I used NINA for the image acquisition software (along with other PHD2, Aztap, Green Swamp Server).

I have watched some videos and have connected the equipment successfully, I have done polar alignment by using the TPP in NINA. This is the result of the polar alignment, I hope it is not that bad. It shows 00degree, 11mins, 44secs of total error:

 

 

After that I try to go to some of DSO object, first I try the M31 since I have visibility of where it is located during my session as I check in SkySafari. So I pick that object in the SkyAtlas, Set for Framing Assistant, and then since I don't have any internet connectivity from my imaging place, I used the "Offline Sky Map" as the image source, then I click "Slew and Center". The mount start slewing but then it stopped at a different location then the one I checked in SkySafari, I tried a different method by getting the RA DEC location from Stellarium, but it still stop at a different location (same location as the previous). 

 

Then I try to verify this by trying to goto Jupiter as I have visibility of Jupiter on the sky. So, I took the coordinate of Jupiter from Stellarium, and it stopped at the different location of where Jupiter was. This is the image, the dot on the sky is the Jupiter but you can see the scope is pointing to another location:

 

 

What went wrong here? What should I check? 

 

List of my gears, in case needed:

SWSA GTi, Askar FMA 230, ASI 533mc, Svbony 30mm guide scope, ASI 120mm min

 

 

Thank you.

Edited by thesti, 25 September 2023 - 10:57 PM.

[NovaAstroFog]

I don't know about NINA, but when I PA, I like to get within 30" of error before I consider myself polar aligned. I then slew away from North to take an image > Plate Solve > Sync Mount. Not sure that's what others do, but GoTo centers object every time after that.

[D_talley]

Polar alignment only aligns the mount with the rotation of the Earth. It does not tell the telescope where the stars are.  You need to align the mount with the stars next. A simple way, is as mentioned above, is to Plate Solve and Sync Mount. 

[thesti]

Polar alignment only aligns the mount with the rotation of the Earth. It does not tell the telescope where the stars are.  You need to align the mount with the stars next. A simple way, is as mentioned above, is to Plate Solve and Sync Mount. 

 

Noted, checking on that. Thank you.

 

 

I don't know about NINA, but when I PA, I like to get within 30" of error before I consider myself polar aligned. I then slew away from North to take an image > Plate Solve > Sync Mount. Not sure that's what others do, but GoTo centers object every time after that.

 

Hi,

 

Thanks for the reply. Sorry, I am quite new to this, what image acquisition software do you use? What does this Sync Mount actually do?

And also "GoTo centers object"? What does that mean?

Edited by thesti, 25 September 2023 - 09:58 PM.

[Sheridan]

11 minutes is a pretty good size error I normally try to get my polar alignment to < 1 minute. After that I do a plate solve that lets the mount know where it's at.The first slew to a target is not always exactly accurate and it takes a couple of times for it to actually center. Give that a try see if it works better for you.

[NovaAstroFog]

Noted, checking on that. Thank you.

 

 

 

Hi,

 

Thanks for the reply. Sorry, I am quite new to this, what image acquisition software do you use? What does this Sync Mount actually do?

And also "GoTo centers object"? What does that mean?

GoTo is the same as Slew to Target, meaning my mount accurately moves to the target and puts the target in frame. I use AsiAIR for DSO images, but that shouldn't be a factor. 11 minutes of error is the main factor, and is probably why your image above shows that amount of error in RED. I would not consider your mount to be polar aligned, and it doesn't look like NINA does either. I would start there.

[Robert7980]

It’s the mount not NINA… 11 minutes off on polar alignment isn’t great, but probably your issue is with your ground station GPS coordinates and altitude of where the mount is sitting…

 

Having your GPS coordinates, Altitude and Polar alignment and the local time to the second accurate should get you within the cone error of the scope, it’ll never be perfect… 

 

So I’d verify you don’t have an error in your location data, like a missing (-) sign or something like that or the clock set a hour off, things like that in the settings they will be in Green Swamp Server (Telescope is what NINA refers to it as). You also need to set the mount to the home position. Pointing towards Polaris… 

 

Plate solving is a way to fix it so it takes a picture then aligns itself precisely, not sure how that works for planets I’ve never tried… But for sending coordinates from a planetarium software you’ll need everything setup precisely… 

Edited by Robert7980, 25 September 2023 - 10:39 PM.

[thesti]

11 minutes is a pretty good size error I normally try to get my polar alignment to < 1 minute. After that I do a plate solve that lets the mount know where it's at.The first slew to a target is not always exactly accurate and it takes a couple of times for it to actually center. Give that a try see if it works better for you.

 

 

Polar alignment only aligns the mount with the rotation of the Earth. It does not tell the telescope where the stars are.  You need to align the mount with the stars next. A simple way, is as mentioned above, is to Plate Solve and Sync Mount. 

 

 

It’s the mount not NINA… 11 minutes off on polar alignment isn’t great, but probably your issue is with your ground station GPS coordinates and altitude of where the mount is sitting…

 

Having your GPS coordinates, Altitude and Polar alignment and the local time to the second accurate should get you within the cone error of the scope, it’ll never be perfect… 

 

So I’d verify you don’t have an error in your location data, like a missing (-) sign or something like that or the clock set a hour off, things like that in the settings they will be in Green Swamp Server (Telescope is what NINA refers to it as). You also need to set the mount to the home position. Pointing towards Polaris… 

 

Plate solving is a way to fix it so it takes a picture then aligns itself precisely, not sure how that works for planets I’ve never tried… But for sending coordinates from a planetarium software you’ll need everything setup precisely… 

 

Hi all,

 

Thanks for the reply, regarding this plate solving, I think I get a better understanding now. So next time once I am polar aligned (try to get down to around 30secs of total error), I will pick any location/stars/DSO that is within my visibility, "slew and center" in NINA, the first time it might not be correct but as long as NINA is able to plate solve, then it would be able to adjust the location until it locates the correct location of the object. Once this is done, the mount is considered as "synced". Is this correct?

 

And after that "synchronization", once I moved to a different object will it be more precise? Or this synchronization process will always have to be done every time we move to a new target?

Thank you.

 

 

 

Edit: As for the GSS location, I have tried to follow the location from my Stellarium (laptop) and SkySafari (mobile phone). I have set the latitude, longitude and elevaton following  the SkySafar though. I think that is all that needed for the location? I will check on that again in my next session.

Edited by thesti, 25 September 2023 - 10:54 PM.

[thesti]

GoTo is the same as Slew to Target, meaning my mount accurately moves to the target and puts the target in frame. I use AsiAIR for DSO images, but that shouldn't be a factor. 11 minutes of error is the main factor, and is probably why your image above shows that amount of error in RED. I would not consider your mount to be polar aligned, and it doesn't look like NINA does either. I would start there.

Alright, noted. This was my first time getting polar aligned, I kinda forget the total error that would be considered as a good alignment. Next time I will try to get around 30secs or total error. Thanks

[rj144]

Here's what I do in Nina... pick a random part of the sky and then plate solve and sync.  Then I do a PA.

Edited by rj144, 25 September 2023 - 11:23 PM.

[Dan Finnerty]

Here's what I do in Nina... pick a random part of the sky and then plate solve and sync.  Then I do a PA.

rj144, What is the purpose of your solve and sync before polar alignment? It seems to me that by physically moving the RA axis to polar align, you have invalidated the mount pointing model you just set up with the prior point and sync. You still need to follow up the polar axis align with a new point and sync to establish the new mount pointing model.

 

Thesti, is the difference between polar align and mount align clear to you? They are two entirely different but complementary things. Polar align mechanically (via the azimuth and elevation adjustment bolts) aligns the mounts mechanical polar axis precisely parallel to the earth's polar axis. But the mount still has no idea where it is pointed to in space. Thats what the slew and sync does. The mount software guesses where to point from its assumed position when you first turned it on, assuming a correct polar alignment. THe s/w then takes an image, plate solves it and determines where it is actually pointed. It can then issue corrected pointing commands to accurately get to your target. A second solve and sync would be smart to enforce the most accurate parameters into the mounts pointing model.

 

Sorry if you already know this stuff, but confusing Polar vs. Mount alignment is a very common beginner mistake.

Edited by Dan Finnerty, 25 September 2023 - 11:50 PM.

[rj144]

rj144, What is the purpose of your solve and sync before polar alignment? It seems to me that by physically moving the RA axis to polar align, you have invalidated the mount pointing model you just set up with the prior point and sync. You still need to follow up the polar axis align with a new point and sync to establish the new mount pointing model.

 

Thesti, is the difference between polar align and mount align clear to you? They are two entirely different but complementary things. Polar align mechanically (via the azimuth and elevation adjustment bolts) aligns the mounts mechanical polar axis precisely parallel to the earth's polar axis. But the mount still has no idea where it is pointed to in space. Thats what the slew and sync does. The mount software guesses where to point from its assumed position when you first turned it on, assuming a correct polar alignment. THe s/w then takes an image, plate solves it and determines where it is actually pointed. It can then issue corrected pointing commands to accurately get to your target. A second solve and sync would be smart to enforce the most accurate parameters into the mounts pointing model.

 

Sorry if you already know this stuff, but confusing Polar vs. Mount alignment is a very common beginner mistake.

I don't move anything.  I PA from the current position in NINA.

[thesti]

rj144, What is the purpose of your solve and sync before polar alignment? It seems to me that by physically moving the RA axis to polar align, you have invalidated the mount pointing model you just set up with the prior point and sync. You still need to follow up the polar axis align with a new point and sync to establish the new mount pointing model.

 

Thesti, is the difference between polar align and mount align clear to you? They are two entirely different but complementary things. Polar align mechanically (via the azimuth and elevation adjustment bolts) aligns the mounts mechanical polar axis precisely parallel to the earth's polar axis. But the mount still has no idea where it is pointed to in space. Thats what the slew and sync does. The mount software guesses where to point from its assumed position when you first turned it on, assuming a correct polar alignment. THe s/w then takes an image, plate solves it and determines where it is actually pointed. It can then issue corrected pointing commands to accurately get to your target. A second solve and sync would be smart to enforce the most accurate parameters into the mounts pointing model.

 

Sorry if you already know this stuff, but confusing Polar vs. Mount alignment is a very common beginner mistake.

 

Ok, I think I starting to understand. The concept of mount align is something that I just knew from this topic. 

So, in order to align the mount in NINA, I need to use the turn on the option of "Sync" and "Reslew to target" on the plate solving tab? Like in this screenshot.

 

And also in the same screenshot, it shows "Error Distance", "RA Error", "DEC Error". Does it mean the plate solving still not on the correct target?

 

 

Here's what I do in Nina... pick a random part of the sky and then plate solve and sync.  Then I do a PA.

 

Ok, plate solve first before PA? Interesting. 

[DanMiller]

Hi,

 

I am new to AP, and just got my gear not long time ago. I used NINA for the image acquisition software (along with other PHD2, Aztap, Green Swamp Server).

I have watched some videos and have connected the equipment successfully, I have done polar alignment by using the TPP in NINA. This is the result of the polar alignment, I hope it is not that bad. It shows 00degree, 11mins, 44secs of total error:

nina-tpp.png

 

 

After that I try to go to some of DSO object, first I try the M31 since I have visibility of where it is located during my session as I check in SkySafari. So I pick that object in the SkyAtlas, Set for Framing Assistant, and then since I don't have any internet connectivity from my imaging place, I used the "Offline Sky Map" as the image source, then I click "Slew and Center". The mount start slewing but then it stopped at a different location then the one I checked in SkySafari, I tried a different method by getting the RA DEC location from Stellarium, but it still stop at a different location (same location as the previous). 

 

Then I try to verify this by trying to goto Jupiter as I have visibility of Jupiter on the sky. So, I took the coordinate of Jupiter from Stellarium, and it stopped at the different location of where Jupiter was. This is the image, the dot on the sky is the Jupiter but you can see the scope is pointing to another location:

 

 

What went wrong here? What should I check? 

WhatsApp Image 2023-09-26 at 10.01.16.jpeg

 

List of my gears, in case needed:

SWSA GTi, Askar FMA 230, ASI 533mc, Svbony 30mm guide scope, ASI 120mm min

 

 

Thank you.

Total error needs to be under 5, I go for under 3. The first 2 numbers are what is causing the total error.  My suggestion is to get the degrees close to 1, as you adjust this.  It also adjusts the elevation.  When adjust the elevation if it is still high.  Tweak after that. 
 

But, again.  TOTAL error is the number you need to worry about.  Look at the image with the upper left. You will see a circle and a line which indicates how good your polar alignment is.  When you get the line within that circle, then it is saying acceptable.   That circle represents an error of 5 or less. You want it at the very minimum to be within that circle.  But I like to be close to the middle then half way out.

 

Now, I don't think that is the cause of slewing to target not being accurate.  I would think that your settings in plate solving are too high for tolarance.  I would sugest lowering the tolarance number to see if that helps resolve it.  I think I have mine around 2? Mine is set to 5.

Verify that you have the correct focal length for your telescope.

 

And then also check your tollarance on the plate solving tab.

 

 

Edited by DanMiller, 26 September 2023 - 07:00 AM.

[thesti]

 

Total error needs to be under 5, I go for under 3. The first 2 numbers are what is causing the total error.  My suggestion is to get the degrees close to 1, as you adjust this.  It also adjusts the elevation.  When adjust the elevation if it is still high.  Tweak after that. 
 

But, again.  TOTAL error is the number you need to worry about.  Look at the image with the upper left. You will see a circle and a line which indicates how good your polar alignment is.  When you get the line within that circle, then it is saying acceptable.   That circle represents an error of 5 or less. You want it at the very minimum to be within that circle.  But I like to be close to the middle then half way out.

 

Now, I don't think that is the cause of slewing to target not being accurate.  I would think that your settings in plate solving are too high for tolarance.  I would sugest lowering the tolarance number to see if that helps resolve it.  I think I have mine around 2? Mine is set to 5.

Verify that you have the correct focal length for your telescope.

 

 

And then also check your tollarance on the plate solving tab.

 

 

 

 

Ya, I think I need to get a more precise polar alignment. And yes, I have tried to align the location (latitude, longitude, time and elevation in Green Swamp Server with my SkySafari, but I will check on that again. For now, I feel the problem is the plate solving is still not correct/pointing to where it should be as in this screenshot it shows a big error distance?

[jml79]

I haven't used GreenSwamp, but I set my Lat, Long in NINA as well as EQMOD. My quick start is;

 

Set focus to about right,

take a 2x10 second light and plate solve the second

then polar align (within 5 minutes or better)

Slew to target and centre.

Focus with filter I'm going to use.

 

The reason some people (including me) take an quick image or 2 and then plate solve something (anything) before anything else is a lot of cameras seem to make a mess of the first shot and then a mess of the first plate solve. I have 4 cameras and 3 of them have very low ADU on the first shot which then makes it fail the plate solve. Taking 2 x 10s shots and then plate solving the second seems to get everything primed, offset set, database loaded into memory etc. Then everything runs smoothly all night. 

[D_talley]

There are two of you, RJ144 and JML79 that plate solve and then polar align. That is a waste of time because you need to move the mount to polar align, which as Dan states, invalidates your plate solve.  There is no way around doing a polar align without moving your mount.  

The best way is to do a polar align, lock down your mount and then plate solve.  

[jml79]

There are two of you, RJ144 and JML79 that plate solve and then polar align. That is a waste of time because you need to move the mount to polar align, which as Dan states, invalidates your plate solve.  There is no way around doing a polar align without moving your mount.  

The best way is to do a polar align, lock down your mount and then plate solve.  

I am completely aware. As I explained, I manually take 2 images and perform 1 plate solve to get things working/verify functionality. If I dive straight into a polar align or slew and centre without, then the first plate solve usually fails and NINA times out for 2 minutes and tries again. Both of my QHY cameras have this issue and 1 Sony DSLR, using different drivers on different computers and different software and even different OS's. It seems that the offset/gain is not set on the first shot resulting in a very low ADU and that a manual plate solve loads the DB into memory for ASTAP.

 

If I PA in Sharcap then I don't notice the issue because Sharpcap just throws out the first bad shot and quickly takes another. In this case, I don't do anything before PA but I still have to take 2 shots and a plate solve when I switch to NINA because I change modes and gain in my camera between Sharpcap and NINA.

 

It may be completely different for ASI cameras.

[Yerman]

Something I’m not seeing in these posts is initial alignment of the scope. After the tripod is setup and visually pointing North the scope then needs to know where it is. This is usually done by aligning the markings on the ra and dec axis. Align the markings then move the tripod until Polaris is near the centre. Note it’s about .75 degrees off. Regardless get it near the centre. Then in your scope settings there should be a setting called “set home”. Now your scope has an idea of where things are in the sky. Polar alignment and plate solving comes after all of the foregoing. Note these proceedures must be re done every time the tripod is moved. If you are on a fixed pier or mount you do it once.

[jml79]

Something I’m not seeing in these posts is initial alignment of the scope. After the tripod is setup and visually pointing North the scope then needs to know where it is. This is usually done by aligning the markings on the ra and dec axis. Align the markings then move the tripod until Polaris is near the centre. Note it’s about .75 degrees off. Regardless get it near the centre. Then in your scope settings there should be a setting called “set home”. Now your scope has an idea of where things are in the sky. Polar alignment and plate solving comes after all of the foregoing. Note these proceedures must be re done every time the tripod is moved. If you are on a fixed pier or mount you do it once.

I have never even heard of that. The rings on my RA and DEC actually move so how would I do that?? I set my scope vertical and centre (yes pointed in the general direction of polaris) and then plate solve on my first move or before I had that, star align with the hand controller.

 

With my "observatory" I don't even do that. The mounts remember where they were parked and can hit home or a target pretty close on first move.

[thesti]

Thanks all for the replies. I finally able to locate and goto M31 this evening. In NINA on the pate solving, I use the sync and reslew to center option to sync with the mount. Then it will reslew to the correct target after a few adjustments. I finally understand the different of mount syncing and pollar alignment. 

 

 

Something I’m not seeing in these posts is initial alignment of the scope. After the tripod is setup and visually pointing North the scope then needs to know where it is. This is usually done by aligning the markings on the ra and dec axis. Align the markings then move the tripod until Polaris is near the centre. Note it’s about .75 degrees off. Regardless get it near the centre. Then in your scope settings there should be a setting called “set home”. Now your scope has an idea of where things are in the sky. Polar alignment and plate solving comes after all of the foregoing. Note these proceedures must be re done every time the tripod is moved. If you are on a fixed pier or mount you do it once.

 

This might be the case, seems like when it starts, the mount expects that it starts from north pole location? Because I always start with the mount position is straight and the counter weight is pointing downward. So it will back to this position when I park the mount. But after sync in plate solving, the park position is changed, I assume the park position after sync is facing polaris. But, I am just guessing.

[unimatrix0]

 

 

 

This might be the case, seems like when it starts, the mount expects that it starts from north pole location? Because I always start with the mount position is straight and the counter weight is pointing downward. So it will back to this position when I park the mount. But after sync in plate solving, the park position is changed, I assume the park position after sync is facing polaris. But, I am just guessing.

Here is what you do to avoid this problem.  Make your mount /scope  face roughly North. Just do your best.  Before you do your NINA 3 point plate solve alignment, slew  near zenith, either a bit off towards East or West, your preference.  It doesn't have to be Zenith, could be towards SouthEast or whatever sky you got available for you. Leave room for the 3PPA doing the 3 point slews, I use only 15 degrees difference in NINA.

The key thing is to slew, and not moving the mount manually by unlocking the clutches. The mount loses the position if you unlock clutches and aim your scope to somewhere else.

Great help here if you got Stellarium installed and your mount connected in there, so you get an idea what to target to get to that position.  (you can also use the flat wizard, it has the slew to zenith option). 

Now do your 3 point polar alignment.  The whole point of doing this- instead of manually /unlocking the clutches- is that you did start off roughly from pointing to North/Polaris and the next time your mount parks, it will park towards facing Polaris.   

Your parking might not be perfect, since you started off with an error, but at least it's gonna point roughly towards North and CW-down when it shuts down,. 

Edited by unimatrix0, 26 September 2023 - 12:48 PM.

[Yerman]

On other thing you can do after you have got everything working synced etc. Instruct the scope to “Home” not park. The scope should point to the North Star. If it’s off just loosen the clutches and manually move the scope to point at Polaris. Lock the clutches and try a few more goto’s plate solve and sync. Now if you select Home the scope should point to Polaris. Parking is something different. Park is where you decide you want the scope to park. It can be in any position. You typically slew the scope to a convenient position using the buttons or program. Then you select “Set Home”. You would normally use these settings if you have a permanent observatory where the home points tge scope too high to get the roof closed. If you pack up after every secession then the last thing you do is “Home” the scope then tell it to “Hibernate “ then turn it off. On the next secession you mount the scope in the home position pointing at Polaris and your off.

[Yerman]

Correction in my last response I said “SetHome” it should have been “Set Park”

[rj144]

Yeah, in retrospect, I should probably plate solve after the PA, but it hasn't mattered one bit when I slew to my targets.