What have you been up to lately?

[GCoyote]

Watching it snow, sleet, and blow.
May have to adjust tomorrow's travel plans.

[SkyHiker]

Yet another wasted evening trying to get the CEM120 goto aligned. It used to be so easy. After polar alignment, just one star goto alignment, a little correction to get the star in the middle, and that's it. Now the star is not even in the view of the 26 mm 70° eyepiece. Got to check from the finder where it is and adjust as long as the star is in the middle of the 26 mm eyepiece view and press OK, to get complaints of too big errors, and at least 3-star alignment is needed. Unfortunately most of those stars that were given as additional stars, were not visible. For the 3rd star there was no useful alternative.

I checked the location, date and time settings probably 5 times. What the heck they did to it in Germany?
Too tired to start writing to them today. Maybe tomorrow...

Keep in mind that your method works so long as there is no cone error (optical axis is not aligned with the mechanical axis). Newts can have that quite easily as a result of collimation and as a result of non classical secondaries. In that case you need at least a two star alignment. If this is for AP where you must have a computer I would just plate solve it.

[SkyHiker]

Yet another wasted evening trying to get the CEM120 goto aligned. It used to be so easy. After polar alignment, just one star goto alignment, a little correction to get the star in the middle, and that's it. Now the star is not even in the view of the 26 mm 70° eyepiece. Got to check from the finder where it is and adjust as long as the star is in the middle of the 26 mm eyepiece view and press OK, to get complaints of too big errors, and at least 3-star alignment is needed. Unfortunately most of those stars that were given as additional stars, were not visible. For the 3rd star there was no useful alternative.

I checked the location, date and time settings probably 5 times. What the heck they did to it in Germany?
Too tired to start writing to them today. Maybe tomorrow...

Keep in mind that your method works so long as there is no cone error (optical axis is not aligned with the mechanical axis). Newts can have that quite easily as a result of collimation and as a result of non classical secondaries. In that case you need at least a two star alignment. If this is for AP where you must have a computer I would just plate solve it.

If you have a finder with cross hairs, align it to the mechanical axis in the daytime by rotating it around RA while also finding the right DEC position and adjusting the centering screws until the view rotates around the center of the crosshairs. With that you can do a 1 step align if the PA is perfect. Check how far off the Newts center is from that. Best done with an eyepiece with crosshairs. You can also try this on the Newt but you may not be able to center it if it has cone error.

[OzEclipse]

Yet another wasted evening trying to get the CEM120 goto aligned. It used to be so easy. After polar alignment, just one star goto alignment, a little correction to get the star in the middle, and that's it. Now the star is not even in the view of the 26 mm 70° eyepiece. Got to check from the finder where it is and adjust as long as the star is in the middle of the 26 mm eyepiece view and press OK, to get complaints of too big errors, and at least 3-star alignment is needed. Unfortunately most of those stars that were given as additional stars, were not visible. For the 3rd star there was no useful alternative.

I checked the location, date and time settings probably 5 times. What the heck they did to it in Germany?
Too tired to start writing to them today. Maybe tomorrow...

I have an iOptron iEQ45, 2012 model that I bought new in 2012. It's goto progressively became more and more ridiculous. I don't know if the encoders became faulty or something else but it wasn't any of the "usual suspects." After stuffing around with it for several years, and with the mount well out of warranty, I gave up. I didn't on-sell my troubles to some poor beginner. I kept it. The drive works accurately enough (30" p-p). I keep it fully assembled in the shed and it's light enough that I can carry it out fully assembled and use it without GOTO. Eg. as an unguided camera tracker for wide-angle and standard lenses during my astro workshops or for a quick look with one of the smaller scopes. When new, I could get it to point within a few degrees. It was never perfect. Now it tries to point to below the horizon or the opposite side of the sky.

After giving up, I bought a second hand Takahashi EM-200 in 2016. I added a SkyFi and point it through Sky Safari (SS) on my iPad. This system "just works!" I've never had any messing around. Accurate polar align with my laser aligner, then one star alignment on SS. SS only has facility for a one star alignment.

Another App, "Astromist" has 2 & 3 point models to correct for cone error. Most of my OTA's don't have enough cone error to give me much trouble. My 6"f7 Newt with its rotation rings and yokes does have cone error. It mostly causes inaccuracies with very big jumps to opposite sides of the sky. Because I prefer to use SS rather than ASTROMIST, I just use SS to jump to a nearby bright easily recognised star, then do a sync, then make a small jump to my object. A technique I carried across from my iEQ45 use, when it's pointing error was small enough that this technique worked.

Keep up the emails to iOptron, get this sorted before warranty runs out.

[turboscrew]

Yet another wasted evening trying to get the CEM120 goto aligned. It used to be so easy. After polar alignment, just one star goto alignment, a little correction to get the star in the middle, and that's it. Now the star is not even in the view of the 26 mm 70° eyepiece. Got to check from the finder where it is and adjust as long as the star is in the middle of the 26 mm eyepiece view and press OK, to get complaints of too big errors, and at least 3-star alignment is needed. Unfortunately most of those stars that were given as additional stars, were not visible. For the 3rd star there was no useful alternative.

I checked the location, date and time settings probably 5 times. What the heck they did to it in Germany?
Too tired to start writing to them today. Maybe tomorrow...

Keep in mind that your method works so long as there is no cone error (optical axis is not aligned with the mechanical axis). Newts can have that quite easily as a result of collimation and as a result of non classical secondaries. In that case you need at least a two star alignment. If this is for AP where you must have a computer I would just plate solve it.

If you have a finder with cross hairs, align it to the mechanical axis in the daytime by rotating it around RA while also finding the right DEC position and adjusting the centering screws until the view rotates around the center of the crosshairs. With that you can do a 1 step align if the PA is perfect. Check how far off the Newts center is from that. Best done with an eyepiece with crosshairs. You can also try this on the Newt but you may not be able to center it if it has cone error.

I was trying to get it good for visual.
I just wonder how there could, suddenly, be cone error. There hasn't been earlier, and the tube has been stored in a room upstairs for almost all that time, when the mount was been fixed.
I guess, I have to check that anyway.

[OzEclipse]

Juha,

Could be encoders dropping a bit or contaminated? Are both RA and Dec wrong?


Joe

[SkyHiker]

I noted several ioptron goto problems in this thread https://www.cloudynights.com/topic/5377 ... pro-mount/ related to a socalled zero point. This zero point can cause goto errors when not set correctly. This is about the IEQ45 but the CEM120 has a zero point too, see this thread, https://groups.io/g/iOptron/topic/82840242 . I suppose checking with the manufacturer is best but these IO groups can be very useful with quick responses, I am on the Losmandy, DSS and OnStep ones, very useful. BTW Joe is probably right that the cone error can't be the main issue but it can't hurt to check.

[turboscrew]

Juha,

Could be encoders dropping a bit or contaminated? Are both RA and Dec wrong?


Joe

I don't have encoders.
And if I goto zero, the axis locks go in without problems - no need to touch the tube, so It's quite accurately right.
You can also search the zero. It has sensors for that.

[turboscrew]

What I used to do is:
- engage the gears
- disengage the axle locks
- polar align
- search the zero (and check the polar alignment - usually fine)
- goto-align with one star
- start observing

Now the polar alignment fails.

[SkyHiker]

What I used to do is:
- engage the gears
- disengage the axle locks
- polar align
- search the zero (and check the polar alignment - usually fine)
- goto-align with one star
- start observing

Now the polar alignment fails.

I checked how you do polar alignment from earlier threads and suggest that you add some extra checks. After you think you are polar aligned, rotate the scope around RA and check if the NCP stays in the same place (not necessarily the center of the FOV) and that everything rotates around it. You can eyeball the NCP quite accurately from the asterism that you showed in your first report thread. This is how I used to polar align before using Ekos. I used a DSLR and a marked piece of tape on its LCD to help with it but you can do it visually too provided that you can see the asterism. There are several weak points in your PA routine that make me distrust it, without doing this check. Another way is to hook up Ekos and use its routine, or sharpcap.

If you are absolutely sure that your PA is good then try goto using the manual buttons monitoring the RA and DEC coordinates and see if you get different results using goto. Just to check if its internal model is messed up.

[turboscrew]

What I used to do is:
- engage the gears
- disengage the axle locks
- polar align
- search the zero (and check the polar alignment - usually fine)
- goto-align with one star
- start observing

Now the polar alignment fails.

I checked how you do polar alignment from earlier threads and suggest that you add some extra checks. After you think you are polar aligned, rotate the scope around RA and check if the NCP stays in the same place (not necessarily the center of the FOV) and that everything rotates around it. You can eyeball the NCP quite accurately from the asterism that you showed in your first report thread. This is how I used to polar align before using Ekos. I used a DSLR and a marked piece of tape on its LCD to help with it but you can do it visually too provided that you can see the asterism. There are several weak points in your PA routine that make me distrust it, without doing this check. Another way is to hook up Ekos and use its routine, or sharpcap.

If you are absolutely sure that your PA is good then try goto using the manual buttons monitoring the RA and DEC coordinates and see if you get different results using goto. Just to check if its internal model is messed up.

My PA for visual is usually a couple of minutes off. but it hasn't been a problem.
I have my 26 mm 70° Omegon SWAN. With my tube, the TFOV is about 1.52° which is 5460" (r = 2730").
The Polaris "orbits" the NCP with about 2635" radius = 5260" diameter. The radius error is 95" (1.6').
If the tube looks directly towards NCP the Polaris should always be in the FOV very near the edge (about 1.6' from the edge).
I've configured that eyepiece in the Stellarium ocular view.

In stellarium I go to NCP (alt-shift-N) and open the ocular view. There it shows in which direction from the center of the view, the Polaris should be, if the view is centered to NCP.
Then I go to the telescope, and adjust the alt and az settings so, that it the Polaris is at the edge in the right direction from the center of the view. If I can put it there with less than 1/16 of the circle (22.5°) error (direction), the alignment error shouldn't be very big. About 1.6' from the edge and about twice that along the arc.
Of course not nearly good enough for photographing - for that, I think, plate solving comes to picture.

It has worked well enough for visual. If, after that, I do goto-align and then slew from zero (NCP) to Betelgeuse, the Betelgeuse emerges pretty well in the middle of the FOV of my 15 mm Plössl.
Erm... did.

A 26 mm 68° eyepiece would work much better (radius error 17"), but nobody seems to make them.

[SkyHiker]

What I used to do is:
- engage the gears
- disengage the axle locks
- polar align
- search the zero (and check the polar alignment - usually fine)
- goto-align with one star
- start observing

Now the polar alignment fails.

I checked how you do polar alignment from earlier threads and suggest that you add some extra checks. After you think you are polar aligned, rotate the scope around RA and check if the NCP stays in the same place (not necessarily the center of the FOV) and that everything rotates around it. You can eyeball the NCP quite accurately from the asterism that you showed in your first report thread. This is how I used to polar align before using Ekos. I used a DSLR and a marked piece of tape on its LCD to help with it but you can do it visually too provided that you can see the asterism. There are several weak points in your PA routine that make me distrust it, without doing this check. Another way is to hook up Ekos and use its routine, or sharpcap.

If you are absolutely sure that your PA is good then try goto using the manual buttons monitoring the RA and DEC coordinates and see if you get different results using goto. Just to check if its internal model is messed up.

My PA for visual is usually a couple of minutes off. but it hasn't been a problem.
I have my 26 mm 70° Omegon SWAN. With my tube, the TFOV is about 1.52° which is 5460" (r = 2730").
The Polaris "orbits" the NCP with about 2635" radius = 5260" diameter. The radius error is 95" (1.6').
If the tube looks directly towards NCP the Polaris should always be in the FOV very near the edge (about 1.6' from the edge).
I've configured that eyepiece in the Stellarium ocular view.

In stellarium I go to NCP (alt-shift-N) and open the ocular view. There it shows in which direction from the center of the view, the Polaris should be, if the view is centered to NCP.
Then I go to the telescope, and adjust the alt and az settings so, that it the Polaris is at the edge in the right direction from the center of the view. If I can put it there with less than 1/16 of the circle (22.5°) error (direction), the alignment error shouldn't be very big. About 1.6' from the edge and about twice that along the arc.
Of course not nearly good enough for photographing - for that, I think, plate solving comes to picture.



It has worked well enough for visual. If, after that, I do goto-align and then slew from zero (NCP) to Betelgeuse, the Betelgeuse emerges pretty well in the middle of the FOV of my 15 mm Plössl.
Erm... did.

A 26 mm 68° eyepiece would work much better (radius error 17"), but nobody seems to make them.

Here you are assuming that your FOV is centered around the mechanical axis. If not, your method is worthless. I just proposed a very simple check to make sure that your PA is good regardless of whether this assumption is true. Release the clutch and rotate around RA to see if the NCP moves. We are just trying to rule out any other possibilities to make sure that the mount is to blame, not the PA.

[turboscrew]

I checked how you do polar alignment from earlier threads and suggest that you add some extra checks. After you think you are polar aligned, rotate the scope around RA and check if the NCP stays in the same place (not necessarily the center of the FOV) and that everything rotates around it. You can eyeball the NCP quite accurately from the asterism that you showed in your first report thread. This is how I used to polar align before using Ekos. I used a DSLR and a marked piece of tape on its LCD to help with it but you can do it visually too provided that you can see the asterism. There are several weak points in your PA routine that make me distrust it, without doing this check. Another way is to hook up Ekos and use its routine, or sharpcap.

If you are absolutely sure that your PA is good then try goto using the manual buttons monitoring the RA and DEC coordinates and see if you get different results using goto. Just to check if its internal model is messed up.

My PA for visual is usually a couple of minutes off. but it hasn't been a problem.
I have my 26 mm 70° Omegon SWAN. With my tube, the TFOV is about 1.52° which is 5460" (r = 2730").
The Polaris "orbits" the NCP with about 2635" radius = 5260" diameter. The radius error is 95" (1.6').
If the tube looks directly towards NCP the Polaris should always be in the FOV very near the edge (about 1.6' from the edge).
I've configured that eyepiece in the Stellarium ocular view.

In stellarium I go to NCP (alt-shift-N) and open the ocular view. There it shows in which direction from the center of the view, the Polaris should be, if the view is centered to NCP.
Then I go to the telescope, and adjust the alt and az settings so, that it the Polaris is at the edge in the right direction from the center of the view. If I can put it there with less than 1/16 of the circle (22.5°) error (direction), the alignment error shouldn't be very big. About 1.6' from the edge and about twice that along the arc.
Of course not nearly good enough for photographing - for that, I think, plate solving comes to picture.



It has worked well enough for visual. If, after that, I do goto-align and then slew from zero (NCP) to Betelgeuse, the Betelgeuse emerges pretty well in the middle of the FOV of my 15 mm Plössl.
Erm... did.

A 26 mm 68° eyepiece would work much better (radius error 17"), but nobody seems to make them.

Here you are assuming that your FOV is centered around the mechanical axis. If not, your method is worthless. I just proposed a very simple check to make sure that your PA is good regardless of whether this assumption is true. Release the clutch and rotate around RA to see if the NCP moves. We are just trying to rule out any other possibilities to make sure that the mount is to blame, not the PA.

I'll check next time I have the opportunity. I just explained how I used to do PA.

[Butterfly Maiden]

My latest product purchase will not displease the weather Gods, so you guys can relax

LED Nail Lamp

It is a replacement LED Nail Lamp (my other one wore out ). It is useful for quickly drying nail products, so is a great time-saver.

[turboscrew]

My latest product purchase will not displease the weather Gods, so you guys can relax

LED Nail Lamp


It is a replacement LED Nail Lamp (my other one wore out ). It is useful for quickly drying nail products, so is a great time-saver.

Finger oven, so to speak? :wink:

[Butterfly Maiden]

My latest product purchase will not displease the weather Gods, so you guys can relax

LED Nail Lamp


It is a replacement LED Nail Lamp (my other one wore out ). It is useful for quickly drying nail products, so is a great time-saver.

Finger oven, so to speak? :wink:

That is actually a good way to describe it Juha

[turboscrew]

My PA for visual is usually a couple of minutes off. but it hasn't been a problem.
I have my 26 mm 70° Omegon SWAN. With my tube, the TFOV is about 1.52° which is 5460" (r = 2730").
The Polaris "orbits" the NCP with about 2635" radius = 5260" diameter. The radius error is 95" (1.6').
If the tube looks directly towards NCP the Polaris should always be in the FOV very near the edge (about 1.6' from the edge).
I've configured that eyepiece in the Stellarium ocular view.

In stellarium I go to NCP (alt-shift-N) and open the ocular view. There it shows in which direction from the center of the view, the Polaris should be, if the view is centered to NCP.
Then I go to the telescope, and adjust the alt and az settings so, that it the Polaris is at the edge in the right direction from the center of the view. If I can put it there with less than 1/16 of the circle (22.5°) error (direction), the alignment error shouldn't be very big. About 1.6' from the edge and about twice that along the arc.
Of course not nearly good enough for photographing - for that, I think, plate solving comes to picture.



It has worked well enough for visual. If, after that, I do goto-align and then slew from zero (NCP) to Betelgeuse, the Betelgeuse emerges pretty well in the middle of the FOV of my 15 mm Plössl.
Erm... did.

A 26 mm 68° eyepiece would work much better (radius error 17"), but nobody seems to make them.

Here you are assuming that your FOV is centered around the mechanical axis. If not, your method is worthless. I just proposed a very simple check to make sure that your PA is good regardless of whether this assumption is true. Release the clutch and rotate around RA to see if the NCP moves. We are just trying to rule out any other possibilities to make sure that the mount is to blame, not the PA.

I'll check next time I have the opportunity. I just explained how I used to do PA.

BTW, what do you think, could that be caused by one leg of the tri-pier melting its way into the ice below (4 - 5 mm deep)?
So gradually the mount started leaning towards SW.

[SkyHiker]

BTW, what do you think, could that be caused by one leg of the tri-pier melting its way into the ice below (4 - 5 mm deep)?
So gradually the mount started leaning towards SW.

Worst case, assuming a 1 m base from one leg to the next, sinking 5 mm would lead to (180/%pi)*(5/1000)*60 = 17.2' difference. For a FOV of about 90' or 45' radius it would get it off center but not outside the FOV.

Note that the DEC position also affects the PA, who knows if that part of the zero position could that have been changed by the work in Germany? For me, I have put some markers on my driveway that let me reposition the mount. Then I use Ekos each time for PA before I do the goto alignment. I checked a few times that the NCP asterism in the PA plate solving is indeed where it is supposed to be.

I'm curious how your next PA turns out. Such a pricey mount should be working without the trouble you have experienced.

[turboscrew]

BTW, what do you think, could that be caused by one leg of the tri-pier melting its way into the ice below (4 - 5 mm deep)?
So gradually the mount started leaning towards SW.

Worst case, assuming a 1 m base from one leg to the next, sinking 5 mm would lead to (180/%pi)*(5/1000)*60 = 17.2' difference. For a FOV of about 90' or 45' radius it would get it off center but not outside the FOV.

Note that the DEC position also affects the PA, who knows if that part of the zero position could that have been changed by the work in Germany? For me, I have put some markers on my driveway that let me reposition the mount. Then I use Ekos each time for PA before I do the goto alignment. I checked a few times that the NCP asterism in the PA plate solving is indeed where it is supposed to be.

I'm curious how your next PA turns out. Such a pricey mount should be working without the trouble you have experienced.

You are right. That leg sinking can't be the reason. I don't think the zero could have been changed, because the "normal" zero position I've been using is the "folded" state. There are two fixed sensors per axis inside the mount for searching the zero position. You can set your own, but I've always used the sensor-defined zero.
I took the tube rings off wiped a bit around and put them back on. With a caliper(?) I checked that the distance from the rings to Losmandy dovetail is the same on both ends.
Let's see what the check procedure says about cone error next time I have the opportunity.
It may take some time. During the work week it's hard to find the time. The weathers are now much better, so maybe next weekend, or the one after that...

BTW, I have 300 mm Losmandy dovetail, and 0.5 mm difference at the ends would have meant less than 6'. And 0.5 mm would have shown clearly with caliper.

If the star was thrown out of the FOV, the error must have been more than 45'.

[DeanD]

My latest product purchase will not displease the weather Gods, so you guys can relax

LED Nail Lamp


It is a replacement LED Nail Lamp (my other one wore out ). It is useful for quickly drying nail products, so is a great time-saver.

Finger oven, so to speak? :wink:

That is actually a good way to describe it Juha

If you called it a "finger sauna" it would be a big seller in Finland... (go on Juha, you know you want one! )