29 replies to this topic

[CA Curtis 17]

The release of the latest version of the Seestar App adds a new level of capability to the Seestar when mounted in the EQ mode. The Polar Alignment routine in the App with its straight forward feedback on altitude and azimuth deviations is extremely easy to use.  And, those on balconies not withstanding, the fact that the App plate solves at three locations near the zenith to get the PA offset means that one does not have to have a direct view of the north celestial pole.  However, one thing that is very confusing to many people, especially those brand new to astronomy, is the fact that, unlike a typical telescope setup on an EQ mount, the altitude angle of the wedge needs to be set to the complimentary angle to the latitude, not the latitude itself.  I put together a video demonstrating why this is the case followed by a live demonstration of the PA process and subsequent live stacking examples to show that we can now get stacking success rates of 100% with ease.  You can find the video here  https://www.youtube....h?v=MPuwhBSJr9w   I hope it helps folks avoid the confusion that can come with the opposite way the wedge is set up from a typical telescope.

 

Best Regards,

Curtis

[Cotts]

Set the polar axis of the Seestar to have an angle with the horizon equal to your latitude.  Period.  Get a digital level or clinometer to get yourself close.  Then the Seestar's plate solving will dial you in the rest of the way.

 

Many wedges have a numerical scale on them, like the one in your video. It measures the angle from vertical at which the wedge is set.  Don't set this scale to your latitude. 

 

Dave. (I live very close to 45º so this situation doesn't affect me....)

[CA Curtis 17]

Many wedges have a numerical scale on them, like the one in your video. It measures the angle from vertical at which the wedge is set.  Don't set this scale to your latitude. 

 

Dave. (I live very close to 45º so this situation doesn't affect me....)

This is the part which confuses people.  As we both say the Seestar measures from the horizon while a wedge measures from the vertical.

[jprideaux]

I noticed that complementary angle as well when I have polar-aligned my SeeStar. I just used whatever angle “got the job done!”.

[CA Curtis 17]

Setting the angle prior to launching the app means that you only need to do a small tweak when the stars come out.  The process works whether you preset the angle or not.  But, you might be surprised how many people get confused the fact that the Seestar asks for the complimentary angle.

[StargazerLuigi]

My Seestar does not ask for the 'complementary angle', it asks for it to be set to my latitude, which is the altitude of the NCP above the horizon. Sure, if my latitude base scale was anywhere near correct, I could set it to the complementary angle, but the Seestar knows nothing of this.

 

Tell me what I'm missing.

[bradhaak]

That's because they don't think about it for ten seconds. Consider the two easy cases and then extrapolate.

1. You're at the North (or South) Pole. Your latitude is 90°. But you don't lay your scope (Seestar or anything else) down flat at 90° from vertical, pointing at the horizon. Obviously, you point it straight up at 0° tilt or 90 minus 90° (your latitude). the answer is to tilt it 0°. This is obviously true.
2. You're at the equator, and your latitude is 0°. You want your telescope laid flat to align with the Earth's axis, so you set it to 90 minus 0° (your latitude). The answer is to tilt it 90°. Again, this is obviously true.

So, for example, I live at 37° north latitude. 90 minus 37° (my latitude) gives 53° of tilt. Guess what, that works, too! 

[groom]

This is the part which confuses people. As we both say the Seestar measures from the horizon while a wedge measures from the vertical.

This is a good point. Thank you for bringing it up.

Edited by groom, 29 March 2025 - 08:18 PM.

[CA Curtis 17]

That's because they don't think about it for ten seconds. Consider the two easy cases and then extrapolate.

1. You're at the North (or South) Pole. Your latitude is 90°. But you don't lay your scope (Seestar or anything else) down flat at 90° from vertical, pointing at the horizon. Obviously, you point it straight up at 0° tilt or 90 minus 90° (your latitude). the answer is to tilt it 0°. This is obviously true.
2. You're at the equator, and your latitude is 0°. You want your telescope laid flat to align with the Earth's axis, so you set it to 90 minus 0° (your latitude). The answer is to tilt it 90°. Again, this is obviously true.

So, for example, I live at 37° north latitude. 90 minus 37° (my latitude) gives 53° of tilt. Guess what, that works, too! 

This is obviously true, but I have learned that a lot of people just don't think about things these ways.  After all, that is one of the reasons we have this forum, to help folks who just are not getting it.

[CA Curtis 17]

My Seestar does not ask for the 'complementary angle', it asks for it to be set to my latitude, which is the altitude of the NCP above the horizon. Sure, if my latitude base scale was anywhere near correct, I could set it to the complementary angle, but the Seestar knows nothing of this.

 

Tell me what I'm missing.

As Brad showed by his examples, the Seestar asks for the angle which is the difference between your latitude and 90 degrees.  This is defined as the complimentary angle.  Of course, if your latitude is 45 degrees then it is also the complimentary angle.  If you still really don't think so, think about Brad's examples carefully.

[WillR]

Setting the angle prior to launching the app means that you only need to do a small tweak when the stars come out.  The process works whether you preset the angle or not.  But, you might be surprised how many people get confused the fact that the Seestar asks for the complimentary angle.

Honestly Curtis, I didn’t know what you were driving at. I like your videos very much, but I haven’t watched this one.

 

You are saying that on the printed scale on an adjustable wedge 0 is vertical and 90 is horizontal?

 

I am using a fluid head tripod, so no wedge, and I just tilt the head to get the reading to match the target angle in the app. Then it plate solves to check the polar alignment. At least in my case, there is nothing to be gained by presetting the angle to the latitude. I prefer to store my Seestar vertically, not at an angle, and it literally takes seconds.

 

But say someone is using a wedge and they are at 40 latitude and preset it by mistake to 50. When they open the app, it will tell them to tilt it that other 10 degrees.

 

But I have to ask, you are getting a stacking rate of 100%?! What length subs? I have gotten 75% to almost 90% with 20”subs, and I thought that was pretty good. How are you getting 100%?

[bradhaak]

Honestly Curtis, I didn’t know what you were driving at. I like your videos very much, but I haven’t watched this one.

 

You are saying that on the printed scale on an adjustable wedge 0 is vertical and 90 is horizontal?

It does vary from wedge to wedge. I have examples that say 0° is level and at least one other that says 90° is level. Set your wedge to level and see if it says it's at 0° or 90°. In the case of your photographic head, I bet it's 0° because you generally don't polar align cameras. 

 

But like you say, that's just to get it close, anyway. The Seestar will guide you in the rest of the way.

 

I made my point above to illustrate what's happening because there's a lot of confusion about how polar alignment works. I didn't do it to tell folks "the right way".

[rydberg]

I too use a pan and tilt fluid head.  I do a blind Polar alignment using the level sensor of the seestar and the compass.  The Seestar level sensor tells you that, when it is level, has an angle of zero.  Polaris, say at my location, is 38 degrees above the horizon.  To point there, I have to tilt the top of the Seestar until the level sensor tells me 52 degrees down (that’s the complentary angle folks talk about).  I the use the compass to point the Seestar at 90 azimuth.  This will put the power button up and I can start the polar deviation routine.

Usually I end up very close in altitude and a bit more off in azimuth angle.

[WillR]

I too use a pan and tilt fluid head.  I do a blind Polar alignment using the level sensor of the seestar and the compass.  The Seestar level sensor tells you that, when it is level, has an angle of zero.  Polaris, say at my location, is 38 degrees above the horizon.  To point there, I have to tilt the top of the Seestar until the level sensor tells me 52 degrees down (that’s the complentary angle folks talk about).  I the use the compass to point the Seestar at 90 azimuth.  This will put the power button up and I can start the polar deviation routine.

Usually I end up very close in altitude and a bit more off in azimuth angle.

Yeah, same here. But the Seestar tells me my latitude angle, not the angle from the zenith. 

[CA Curtis 17]

You are saying that on the printed scale on an adjustable wedge 0 is vertical and 90 is horizontal?

The printed scale is such that at 0 degrees a standard telescope optical tube will be horizontal and at 90 degrees will be vertical.  The Seestar on the other hand will be the opposite;  vertical at 0 degrees and horizontal at 90 degrees.  Hence the confusion for many people.  Not only that, with the Seestar the wedge is rotated by 180 degrees in azimuth from where it is for a standard optical tube.  This means that while we set the wedge to our latitude for a standard optical tube, we have to set it to the complimentary angle (90 - latitude) for the Seestar.  The Seestar mounts vertically while a standard optical tube mounts horizontal to the base of the wedge.  I demonstrate the difference between mounting the Seestar vs a standard optical tube in the video.  Makes it very clear that the angles are reversed between the two cases.  In the end, one will still get the feedback from the Seestar to complete the polar alignment, but many have been confused because they expected the Seestar to tell them to adjust the angle to their latitude which is standard of any optical tube.

 

 

I am using a fluid head tripod, so no wedge, and I just tilt the head to get the reading to match the target angle in the app. Then it plate solves to check the polar alignment. At least in my case, there is nothing to be gained by presetting the angle to the latitude. I prefer to store my Seestar vertically, not at an angle, and it literally takes seconds.

 

There are fluid heads that have an angle scale on the side so that you can pre-set it if you want.  Whether one uses a wedge or tilt/pan head it is up to the user whether they want to preset the angle so they are close when the stars come out.  It just makes it a little faster to get where you need to.  Similar to leveling the tripod making it faster to polar align by reducing the cross talk between the two adjustment axes.

 

 

But say someone is using a wedge and they are at 40 latitude and preset it by mistake to 50. When they open the app, it will tell them to tilt it that other 10 degrees.

 

But I have to ask, you are getting a stacking rate of 100%?! What length subs? I have gotten 75% to almost 90% with 20”subs, and I thought that was pretty good. How are you getting 100%?

Someone at 40 deg latitude should set the wedge to 50 deg which is the complementary angle.  Then the Seestar will say you are spot on for angle.

 

In the short video I only demonstrated 10sec exposures which should give close to 100% stacking rates with good seeing.  And that is what I got.  I haven't yet tested 20 and 30 sec but do not expect to get 100% and expect the actual value to be a bit fussier about the quality of the polar alignment.  I intend to test this with 2 different wedges, the less expensive Skywatcher and the more expensive Williams Optics which I just bought for this exact test.

 

The Seestar only uses 3 points very close together to build its pointing model and to achieve PA.  There is a reason that T-Point allows one to use hundreds of points all across the sky to get a very accurate PA and pointing model.  The later has much more leverage, which is why it is used on many high end mounts.

[CA Curtis 17]

Yeah, same here. But the Seestar tells me my latitude angle, not the angle from the zenith. 

The Seestar shows your latitude angle to the right in black or grey.  It shows you the angle you are at to the left of that in red.  It shows you are in the green, good angular alignment, when the wedge or your tilt/pan head is at the angle which is the compliment of your latitude which is 90 deg minus the angle shown at the right in black or grey.

[carver2011]

This is all much to do about nothing. When you begin EQ mode, SeeStar shows you the Declination for your location. Simplely move your wedge up or down to match your Declination number. No need to know from the zenith, of horizontal. There's no need to even have a numbered scale on your wedge, Simple as that. Just raise or lower the wedge to match the numbers. The numbers in this image start out as 87 degrees, at a Latitude of 31 degrees. In this case just lower the wedge from 87 degrees to match  31degrees. Numbers on wedge for a SeeStar, not even necessary. 

     Ed 

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Edited by carver2011, 30 March 2025 - 06:07 AM.

[CA Curtis 17]

This is all much to do about nothing. When you begin EQ mode, SeeStar shows you the Declination for your location. Simplely move your wedge up or down to match your Declination number. No need to know from the zenith, of horizontal. There's no need to even have a numbered scale on your wedge, Simple as that. Just raise or lower the wedge to match the numbers. The numbers in this image start out as 87 degrees, at a Latitude of 31 degrees. In this case just lower the wedge from 87 degrees to match  31degrees. Numbers on wedge for a SeeStar, not even necessary. 

     Ed 

To folks like us it is indeed "nothing", but I get questions and comments on from folks who are very much confused by this.  I have come to accept that this hobby attracts people of all sorts of experience and know how.  Again, that is one of the reasons for forums like this.

[WillR]

…..The Seestar on the other hand will be the opposite;  vertical at 0 degrees and horizontal at 90 degrees.  

Curtis, I have my Seestar on the counter (obviously pointing up) and turned it on, and went to the mount mode menu. It shows the current altitude as 89 degrees and my latitude as 41 degrees, just like Ed’s photo above with different numbers.  I then tilt it until the red number matches my latitude and go to “Get polar align deviation”.

 

Where are you getting the Seestar showing “vertical at 0”?  I don’t follow.

 

I put it out with the leg aligned with the tilt direction of the fluid head pointing roughly north. I boot it up, go to the app. Use my left hand to loosen the tightening knob on this axis and with my right hand tilt it with the long handle, which is pointing north until the  two numbers on the first screen match, and tighten it. I know my latitude, but I don’t even need to, because the Seestar knows it and displays it.

 

I guess if I had a wedge, I might want to preset it and leave it between sessions, unscrewing the Seestar from the mount.  I don’t know how much more difficult it is to loosen and angle a wedge as opposed to a fluid head.

 

I agree that leveling the tripod is probably a good idea so there is less cross talk, like you say, when doing the final alignment.

[WillR]

To folks like us it is indeed "nothing", but I get questions and comments on from folks who are very much confused by this.  I have come to accept that this hobby attracts people of all sorts of experience and know how.  Again, that is one of the reasons for forums like this.

And I want to thank you again for your great videos, especially on the Seestar. Your Seestar for Dummies was very helpful starting out. Many menu items are not obvious or easy to find.

[WillR]

Okay, I went to have a look at your video, and now I see what you are saying. Since the wedge is rotated 180 degrees in azimuth from where it would point if using a traditional telescope, the altitude adjustment angle is now the compliment.

 

If someone was used to polar aligning a regular scope, this would be confusing. But for us dummies who did their first polar alignment with a Seestar, we just use the app. 

Edited by WillR, 30 March 2025 - 08:40 AM.

[CA Curtis 17]

Okay, I went to have a look at your video, and now I see what you are saying. Since the wedge is rotated 180 degrees in azimuth from where it would point if using a traditional telescope, the altitude adjustment angle is now the compliment.

 

If someone was used to polar aligning a regular scope, this would be confusing. But for us dummies who did their first polar alignment with a Seestar, we just use the app. 

Glad you got it.  I will add, that for whatever reason, even folks who aren't used to a regular scope found it confusing.

[JonNPR]

To folks like us it is indeed "nothing", but I get questions and comments on from folks who are very much confused by this.  I have come to accept that this hobby attracts people of all sorts of experience and know how.  Again, that is one of the reasons for forums like this.

Well, I for one am now confused. And a bit worried. Because the basic Sky Watcher  Wedge is backordered, I ordered a Peterson Engineering wedge linked here several places…thinking it a very simple solution. You order it with your latitude to a tenth of a degree and just bolt the Seestar on it. Not adjustable. Reading what you have written, I think you are saying I should have ordered this made to the RECIPROCAL of my latitude. Yes?

Edited by JonNPR, 30 March 2025 - 06:20 PM.

[CA Curtis 17]

Well, I for one am now confused. And a bit worried. Because the basic Sky Watcher  Wedge is backordered, I ordered a Peterson Engineering wedge linked here several places…thinking it a very simple solution. You order it with your latitude to a tenth of a degree and just bolt the Seestar on it. Not adjustable. Reading what you have written, I think you are saying I should have ordered this made to the RECIPROCAL of my latitude. Yes?

Yes.  If you happen to live at latitude 45degrees you are Golden (90-45 = 45 for those why aren't quite there yet).  But for any other latitude you will not be able to get an optimal PA.  

 

This is precisely why I added this demo in the video.  I have been doing astronomy for a long time, but I will admit that I was scratching my head for a while on this topic before my lightbulb went off.  Sorry, Brad, it took me more than 10 seconds.  But maybe this is why I seem to connect so well with people who watch my videos.  I get confused too before I work my way out of it which helps to understand what can trip other people up.

 

Best Regards,

Curtis

[WillR]

Well, I for one am now confused. And a bit worried. Because the basic Sky Watcher  Wedge is backordered, I ordered a Peterson Engineering wedge linked here several places…thinking it a very simple solution. You order it with your latitude to a tenth of a degree and just bolt the Seestar on it. Not adjustable. Reading what you have written, I think you are saying I should have ordered this made to the RECIPROCAL of my latitude. Yes?

Since he is making them for the Seestar, it should be fine. His product is actually a piece of metal bent to an obtuse angle with the angle being your latitude plus 90 degrees. That's. what I see going to his website. If your latitude was 90, it would be a flat bar. If it were 0, it would be a right angle.

 

But give them a call if you are worried.

 

The problem is, how do you adjust the polar alignment after the Seestar gets the deviation? You will be fiddling with the tripod legs a lot. I. looked at these, but decided that having no way to adjust was a deal breaker for me.

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Edited by WillR, 30 March 2025 - 10:26 PM.