Re: Servo Cat moves after goto completes.
Ok, It will be the end of January before we get to use it again. I am almost certain that it is Gen3. I just wish it didn¡¯t do the second movement.? A little over a year ago one of the spur gears came lose inside the Alt drive. We were able to slide it back into place and get it going again. At that time, we tested all the setscrews both internal and the capstan. All were good. Bob ?
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From: [email protected] <[email protected]> On Behalf Of K9RX - Gary via groups.io
Sent: Wednesday, January 8, 2025 5:20 PM
To: [email protected]; [email protected]
Subject: Re: [ServoCAT] Servo Cat moves after goto completes.? Sorry - I think you missed the point. IF it is the latest version firmware then my point is a) that is why you are seeing a lower value and yet it moves again and b) there is indeed a last mover after that...? so if there's slippage in the drive rollers that would account for it.? Also: the fact that it is getting worse suggests strongly it is a loose drive roller.? But I would suggest you check the version. If it powers up and the red AUX light comes on before the green SLEW light (ignore the HC light for this) then it is the latest version. (if you have a Gen2 it might show the yellow SPm light before the green SLEW light) ------ Original Message ------ Subject Re: [ServoCAT] Servo Cat moves after goto completes. No, it goto¡¯s essentially almost 0¡¯s. Then moves and ends up something like 0.30:0.55. ?Back when we first noticed it, the numbers were around 0.10 :0.10. I might suspect the gears are getting play in them except after nearly getting it right, the motors wind back up and it moves decidedly away. Firmware has not been updated in years. Probably should do that first. Bob ? ? The algorithm is designed, assuming you are using the latest version firmware, to always end up in the direction of sidereal tracking. So - it does a GOTO. Then it gets the offset again from the DSC and does a 2nd GOTO. If after the 2nd one the distance to the object is still more than ... I think it was 0.04¡ã, it will do a third one, if it is within that it will not do another.? But it then checks to see which direction the last move was - was it in the direction of sidereal or not. If not it will move the axis away in the direction opposite sidereal, more than the backlash value (typically 0.7¡ã or so)... and then it will do one final GOTO. THIS should put it both at 0.00 on each axis as well as tracking immediately (no backlash to unwind).? Thus you could and would see behavior like you are describing - but it should still end up < 0.05¡ã away.? ------ Original Message ------ Subject Re: [ServoCAT] Servo Cat moves after goto completes. Gary, Thanks for the reply. I will check the drive rollers. It seems to split the error between the axes. I will check both. ?Hadn¡¯t really thought about it being slipping as it goes to the target stops for about a half second then motors past. It is pretty much acquiring the target in the initial goto. No overshoot or undershoot there. Just immediately after acquisition, the motors start back up and drive past. I is like it has built in offset. Bob ? ? Forgive me - I saw this and forgot to respond to it ...? So - this sounds like a drive roller is slipping due to a loose grub screw. Check to see which axis is off first - then focus on the drive roller for that axis.? ------ Original Message ------ Date 1/2/2025 10:26:17 PM Subject [ServoCAT] Servo Cat moves after goto completes. I am asking on behalf of my clubs SC install. It is a 40" with a Nexus (not Pro). All GOTO's are via the Nexus. A couple of years ago just after a GOTO finished the SC would motor about 10 arcminutes from the target. Display on Nexus indication something like `0.10. It has progressively increased over the past year or so. Last outing it was nearly 1 degree. I can issue another GOTO and it will zero in a little better. Strange thing is it will nearly zero the target stops then proceed again to a position now that is 50+ arcminutes. Anybody got any ideas what the issue is? We are calling it overshoot. In it is acquiring the target then moving away.
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Re: Servo Cat moves after goto completes.
Bob,?
Sorry - I think you missed the point. IF it is the latest version firmware then my point is a) that is why you are seeing a lower value and yet it moves again and b) there is indeed a last mover after that...?
so if there's slippage in the drive rollers that would account for it.?
Also: the fact that it is getting worse suggests strongly it is a loose drive roller.?
But I would suggest you check the version. If it powers up and the red AUX light comes on before the green SLEW light (ignore the HC light for this) then it is the latest version. (if you have a Gen2 it might show the yellow SPm light before the green SLEW light)
g.
------ Original Message ------
Date 1/8/2025 6:24:51 PM
Subject Re: [ServoCAT] Servo Cat moves after goto completes.
No, it goto¡¯s essentially almost 0¡¯s. Then moves and ends up something like 0.30:0.55. ?Back when we first noticed it, the numbers were around 0.10 :0.10. I might suspect the gears are getting play in them except after nearly getting it right, the motors wind back up and it moves decidedly away. Firmware has not been updated in years. Probably should do that first. Bob ? ? The algorithm is designed, assuming you are using the latest version firmware, to always end up in the direction of sidereal tracking. So - it does a GOTO. Then it gets the offset again from the DSC and does a 2nd GOTO. If after the 2nd one the distance to the object is still more than ... I think it was 0.04¡ã, it will do a third one, if it is within that it will not do another.? But it then checks to see which direction the last move was - was it in the direction of sidereal or not. If not it will move the axis away in the direction opposite sidereal, more than the backlash value (typically 0.7¡ã or so)... and then it will do one final GOTO. THIS should put it both at 0.00 on each axis as well as tracking immediately (no backlash to unwind).? Thus you could and would see behavior like you are describing - but it should still end up < 0.05¡ã away.? ------ Original Message ------ Subject Re: [ServoCAT] Servo Cat moves after goto completes. Gary, Thanks for the reply. I will check the drive rollers. It seems to split the error between the axes. I will check both. ?Hadn¡¯t really thought about it being slipping as it goes to the target stops for about a half second then motors past. It is pretty much acquiring the target in the initial goto. No overshoot or undershoot there. Just immediately after acquisition, the motors start back up and drive past. I is like it has built in offset. Bob ? ? Forgive me - I saw this and forgot to respond to it ...? So - this sounds like a drive roller is slipping due to a loose grub screw. Check to see which axis is off first - then focus on the drive roller for that axis.? ------ Original Message ------ Date 1/2/2025 10:26:17 PM Subject [ServoCAT] Servo Cat moves after goto completes. I am asking on behalf of my clubs SC install. It is a 40" with a Nexus (not Pro). All GOTO's are via the Nexus. A couple of years ago just after a GOTO finished the SC would motor about 10 arcminutes from the target. Display on Nexus indication something like `0.10. It has progressively increased over the past year or so. Last outing it was nearly 1 degree. I can issue another GOTO and it will zero in a little better. Strange thing is it will nearly zero the target stops then proceed again to a position now that is 50+ arcminutes. Anybody got any ideas what the issue is? We are calling it overshoot. In it is acquiring the target then moving away.
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Re: Servo Cat moves after goto completes.
No, it goto¡¯s essentially almost 0¡¯s. Then moves and ends up something like 0.30:0.55. ?Back when we first noticed it, the numbers were around 0.10 :0.10. I might suspect the gears are getting play in them except after nearly getting it right, the motors wind back up and it moves decidedly away. Firmware has not been updated in years. Probably should do that first. Bob ?
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From: [email protected] <[email protected]> On Behalf Of K9RX - Gary via groups.io
Sent: Wednesday, January 8, 2025 4:02 PM
To: [email protected]; [email protected]
Subject: Re: [ServoCAT] Servo Cat moves after goto completes.? The algorithm is designed, assuming you are using the latest version firmware, to always end up in the direction of sidereal tracking. So - it does a GOTO. Then it gets the offset again from the DSC and does a 2nd GOTO. If after the 2nd one the distance to the object is still more than ... I think it was 0.04¡ã, it will do a third one, if it is within that it will not do another.? But it then checks to see which direction the last move was - was it in the direction of sidereal or not. If not it will move the axis away in the direction opposite sidereal, more than the backlash value (typically 0.7¡ã or so)... and then it will do one final GOTO. THIS should put it both at 0.00 on each axis as well as tracking immediately (no backlash to unwind).? Thus you could and would see behavior like you are describing - but it should still end up < 0.05¡ã away.? ------ Original Message ------ Subject Re: [ServoCAT] Servo Cat moves after goto completes. Gary, Thanks for the reply. I will check the drive rollers. It seems to split the error between the axes. I will check both. ?Hadn¡¯t really thought about it being slipping as it goes to the target stops for about a half second then motors past. It is pretty much acquiring the target in the initial goto. No overshoot or undershoot there. Just immediately after acquisition, the motors start back up and drive past. I is like it has built in offset. Bob ? ? Forgive me - I saw this and forgot to respond to it ...? So - this sounds like a drive roller is slipping due to a loose grub screw. Check to see which axis is off first - then focus on the drive roller for that axis.? ------ Original Message ------ Date 1/2/2025 10:26:17 PM Subject [ServoCAT] Servo Cat moves after goto completes. I am asking on behalf of my clubs SC install. It is a 40" with a Nexus (not Pro). All GOTO's are via the Nexus. A couple of years ago just after a GOTO finished the SC would motor about 10 arcminutes from the target. Display on Nexus indication something like `0.10. It has progressively increased over the past year or so. Last outing it was nearly 1 degree. I can issue another GOTO and it will zero in a little better. Strange thing is it will nearly zero the target stops then proceed again to a position now that is 50+ arcminutes. Anybody got any ideas what the issue is? We are calling it overshoot. In it is acquiring the target then moving away.
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Re: Servo Cat moves after goto completes.
The algorithm is designed, assuming you are using the latest version firmware, to always end up in the direction of sidereal tracking. So - it does a GOTO. Then it gets the offset again from the DSC and does a 2nd GOTO. If after the 2nd one the distance to the object is still more than ... I think it was 0.04¡ã, it will do a third one, if it is within that it will not do another.?
But it then checks to see which direction the last move was - was it in the direction of sidereal or not. If not it will move the axis away in the direction opposite sidereal, more than the backlash value (typically 0.7¡ã or so)... and then it will do one final GOTO. THIS should put it both at 0.00 on each axis as well as tracking immediately (no backlash to unwind).?
Thus you could and would see behavior like you are describing - but it should still end up < 0.05¡ã away.?
g.
------ Original Message ------
Date 1/8/2025 5:29:29 PM
Subject Re: [ServoCAT] Servo Cat moves after goto completes.
Gary, Thanks for the reply. I will check the drive rollers. It seems to split the error between the axes. I will check both. ?Hadn¡¯t really thought about it being slipping as it goes to the target stops for about a half second then motors past. It is pretty much acquiring the target in the initial goto. No overshoot or undershoot there. Just immediately after acquisition, the motors start back up and drive past. I is like it has built in offset. Bob ? ? Forgive me - I saw this and forgot to respond to it ...? So - this sounds like a drive roller is slipping due to a loose grub screw. Check to see which axis is off first - then focus on the drive roller for that axis.? ------ Original Message ------ Date 1/2/2025 10:26:17 PM Subject [ServoCAT] Servo Cat moves after goto completes. I am asking on behalf of my clubs SC install. It is a 40" with a Nexus (not Pro). All GOTO's are via the Nexus. A couple of years ago just after a GOTO finished the SC would motor about 10 arcminutes from the target. Display on Nexus indication something like `0.10. It has progressively increased over the past year or so. Last outing it was nearly 1 degree. I can issue another GOTO and it will zero in a little better. Strange thing is it will nearly zero the target stops then proceed again to a position now that is 50+ arcminutes. Anybody got any ideas what the issue is? We are calling it overshoot. In it is acquiring the target then moving away.
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Re: Servo Cat moves after goto completes.
Gary, Thanks for the reply. I will check the drive rollers. It seems to split the error between the axes. I will check both. ?Hadn¡¯t really thought about it being slipping as it goes to the target stops for about a half second then motors past. It is pretty much acquiring the target in the initial goto. No overshoot or undershoot there. Just immediately after acquisition, the motors start back up and drive past. I is like it has built in offset. Bob ?
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From: [email protected] <[email protected]> On Behalf Of K9RX - Gary via groups.io
Sent: Wednesday, January 8, 2025 2:23 PM
To: [email protected]; [email protected]
Subject: Re: [ServoCAT] Servo Cat moves after goto completes.? Forgive me - I saw this and forgot to respond to it ...? So - this sounds like a drive roller is slipping due to a loose grub screw. Check to see which axis is off first - then focus on the drive roller for that axis.? ------ Original Message ------ Date 1/2/2025 10:26:17 PM Subject [ServoCAT] Servo Cat moves after goto completes. I am asking on behalf of my clubs SC install. It is a 40" with a Nexus (not Pro). All GOTO's are via the Nexus. A couple of years ago just after a GOTO finished the SC would motor about 10 arcminutes from the target. Display on Nexus indication something like `0.10. It has progressively increased over the past year or so. Last outing it was nearly 1 degree. I can issue another GOTO and it will zero in a little better. Strange thing is it will nearly zero the target stops then proceed again to a position now that is 50+ arcminutes. Anybody got any ideas what the issue is? We are calling it overshoot. In it is acquiring the target then moving away.
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Re: Servo Cat moves after goto completes.
Hello Bob,
Forgive me - I saw this and forgot to respond to it ...?
So - this sounds like a drive roller is slipping due to a loose grub screw. Check to see which axis is off first - then focus on the drive roller for that axis.?
Gary Myers StellarCAT
------ Original Message ------
Date 1/2/2025 10:26:17 PM
Subject [ServoCAT] Servo Cat moves after goto completes.
I am asking on behalf of my clubs SC install. It is a 40" with a Nexus (not Pro). All GOTO's are via the Nexus. A couple of years ago just after a GOTO finished the SC would motor about 10 arcminutes from the target. Display on Nexus indication something like `0.10. It has progressively increased over the past year or so. Last outing it was nearly 1 degree. I can issue another GOTO and it will zero in a little better. Strange thing is it will nearly zero the target stops then proceed again to a position now that is 50+ arcminutes. Anybody got any ideas what the issue is? We are calling it overshoot. In it is acquiring the target then moving away.
Bob
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Re: SOLVED: Re: Problem tracking with ArgoNavis and ServoCat on my 20" f/4
Mike,
Indeed you can "control" the scope using Stellarium or Sky Safari (also Cartes du Ciel). Control here meaning you can see where the scope is pointed and you can do a GOTO to an object you select. Note in Sky Safari they are using the latest version of planetarium coms (from ServoCAT/AN) which includes a much higher resolution in both directions. I don't think Stellarium has implemented that (and in their defense I don't remember them ever being asked to do so). The ASCOM driver, I don't believe, has been updated to include this higher resolution mode either.?
It does not allow for plate solving. It is being done - Mickey does it I know and I believe Alex does as well. It does require that a DSC, specifically either the Argo Navis or the Nexus, is in use.?
There are behind the scenes efforts on adding to and improving these capabilities.?
Nice work! I'm doing 1 - 12 second subs, mainly and usually 2-3 seconds to limit the impact of seeing (Lucky Imaging). I unfortunately didn't get 'in to' AP until after I sold the business and moved to a 55+ community here in Richmond VA. Then realized after I started working on it and helping out Bill (the new owner, BBAstro) ... that I can't do it well because I have no backyard to leave a rig setup. I'm working on trying to resolve that as well. I'm also working on adding a guide camera with ST4 capability to try to keep a rough centering of the images due to mount error/user error during alignment.?
Gary Myers
------ Original Message ------
Date 1/8/2025 8:50:52 AM
Subject Re: [ServoCAT] SOLVED: Re: Problem tracking with ArgoNavis and ServoCat on my 20" f/4
Hi,
everything is working ok for me at present (20" f/4 classic Obsession, Paracorr field flatenner with ServoCat and ArgoNavis) and as I explained before I use SharpCap Pro's live stacking feature (2s exposures, ASI294MMPro camera gain 450, T=0C, 4x150 calibrated stacked frames per LRGB filter).? I also use the same set up to take lunar and planetary pictures with an ASI224MC camera and various TeleVue barlows (videos captured with SharpCap).
?
Here is a link to some of my images posted on the British Astronomical Association website gallery:
?
?
However, I am still interested in finding out if it is possible yet to control my scope from my laptop using a program like Stellarium or Cartes du Ciel (or Sky Safari, or other planetarium program).? It's not essential but it might be more convenient than just using the AN control pad.? Also, separately, I use for my SkyWatcher mount and triplet refractor a program called APT (astrophotography tool) that has plate solving incorporated which I find very useful.? Usually I can visually spot the target through the eyepiece of my Obsession after a GOTO and get it centered, but again if plate solving could be used to finesse the alignment and centering and confirm that I do indeed have the object that would be great.
?
So my question is with the current state of developments can either of these things be done, and if so is there any available documentation that would guide me on how to achieve this?
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Re: SOLVED: Re: Problem tracking with ArgoNavis and ServoCat on my 20" f/4
Mike,
I have the ServoCAT - Argo Navis driving my UC18. ?I loaded the ASCOM driver for ServoCAT and have been remotely observing inside my house. ?The key for my system was mounting a NUC type PC (Eagle 4S) on the telescope to run all the software
and I remotely log in with MS Remote Desktop. ?Stellarium running on the NUC slews to the target. ?I added a focus motor for remote focus (from Primalucelab). ?I built a remote control filter strip motor system to change filters. ?Some folks on this site have
figured out how to avoid a 2 star alignment for truly remote control and plate solve. ?Plate solving is on my todo list.
Richard
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Hi,
everything is working ok for me at present (20" f/4 classic Obsession, Paracorr field flatenner with ServoCat and ArgoNavis) and as I explained before I use SharpCap Pro's live stacking feature (2s exposures, ASI294MMPro camera gain 450, T=0C, 4x150 calibrated
stacked frames per LRGB filter).? I also use the same set up to take lunar and planetary pictures with an ASI224MC camera and various TeleVue barlows (videos captured with SharpCap).
?
Here is a link to some of my images posted on the British Astronomical Association website gallery:
?
?
However, I am still interested in finding out if it is possible yet to control my scope from my laptop using a program like Stellarium or Cartes du Ciel (or Sky Safari, or other planetarium program).? It's not essential but it might be more convenient
than just using the AN control pad.? Also, separately, I use for my SkyWatcher mount and triplet refractor a program called APT (astrophotography tool) that has plate solving incorporated which I find very useful.? Usually I can visually spot the target through
the eyepiece of my Obsession after a GOTO and get it centered, but again if plate solving could be used to finesse the alignment and centering and confirm that I do indeed have the object that would be great.
?
So my question is with the current state of developments can either of these things be done, and if so is there any available documentation that would guide me on how to achieve this?
|
Re: SOLVED: Re: Problem tracking with ArgoNavis and ServoCat on my 20" f/4
Hi,
everything is working ok for me at present (20" f/4 classic Obsession, Paracorr field flatenner with ServoCat and ArgoNavis) and as I explained before I use SharpCap Pro's live stacking feature (2s exposures, ASI294MMPro camera gain 450, T=0C, 4x150 calibrated stacked frames per LRGB filter).? I also use the same set up to take lunar and planetary pictures with an ASI224MC camera and various TeleVue barlows (videos captured with SharpCap).
?
Here is a link to some of my images posted on the British Astronomical Association website gallery:
?
?
However, I am still interested in finding out if it is possible yet to control my scope from my laptop using a program like Stellarium or Cartes du Ciel (or Sky Safari, or other planetarium program).? It's not essential but it might be more convenient than just using the AN control pad.? Also, separately, I use for my SkyWatcher mount and triplet refractor a program called APT (astrophotography tool) that has plate solving incorporated which I find very useful.? Usually I can visually spot the target through the eyepiece of my Obsession after a GOTO and get it centered, but again if plate solving could be used to finesse the alignment and centering and confirm that I do indeed have the object that would be great.
?
So my question is with the current state of developments can either of these things be done, and if so is there any available documentation that would guide me on how to achieve this?
|
Daniel, Yes - shouldn't be a problem. On my 12" Obsession used for astrophotography I am running the camera and the camera cooler as well as an Ryzen R5 miniPC - and of course the ServoCAT and Argo Navis.?When controlling the camera using SharpCap, running the Pegasus UPB and running Stellarium on the mini-PC the peak currents are over 5A.?
Gary?
------ Original Message ------
Date 1/8/2025 7:35:52 AM
Subject Re: [ServoCAT] Powered ground board
Gary,
Thank you for the reply. Will the 12v socket supply enough current for 2-3 dew heaters on low (eyepiece, secondary and maybe telrad? Other than that I might keep the 12v female socket on the scope.
Also is the polarity the same as in a car with tip being positive? I use Anderson power poles on everything and I have an adapter that should work.
Daniel V
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Gary,
Thank you for the reply. Will the 12v socket supply enough current for 2-3 dew heaters on low (eyepiece, secondary and maybe telrad? Other than that I might keep the 12v female socket on the scope.
Also is the polarity the same as in a car with tip being positive? I use Anderson power poles on everything and I have an adapter that should work.
Daniel V
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Hello Daniel,?
?
There are two different types of connections at the foot of the ground board. The earliest version was a male cigarette lighter plug embedded in a hole in the foot at a right angle to the front of the foot. So not visible unless you get down a bit to see it. Yu'd just need a 12V cigarette lighter cable male to female. I'd try to get at least 18 ga, and not go longer than 10 - 12'. Nothing larger than 14 ga is needed at the current levels involved (and an 18 ga is just fine for a 12" Junior system). This you can get in a good number of places.?
?
The other one, I don't remember exactly when I changed to it but I believe it was around 2005, is an XLR connector, 3 pin. The foot has a male socket that is visible at the end of the foot. This requires whatever connection you need at the power source end (as would the first one) ---- but we always supplied a 12V cigarette plug --- and the scope end has an inline female plug. You can get this from BBAstro if you want a premade one, send a note to Bill if that is the case.?
?
regards,
?
Gary Myers
StellarCAT
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I have a 12.5 obsession classic from 2004(serial number 1)
I am wondering what power connection it has at the time of production.
I was told its just a female 12v socket. I am unsure if that is correct.
I am not in front of the scope til Friday/Saturday so an answer before I look at it would be appreciated so I can order a cable
Daniel Vrolijk
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Servo Cat moves after goto completes.
I am asking on behalf of my clubs SC install. It is a 40" with a Nexus (not Pro). All GOTO's are via the Nexus. A couple of years ago just after a GOTO finished the SC would motor about 10 arcminutes from the target. Display on Nexus indication something like `0.10. It has progressively increased over the past year or so. Last outing it was nearly 1 degree. I can issue another GOTO and it will zero in a little better. Strange thing is it will nearly zero the target stops then proceed again to a position now that is 50+ arcminutes. Anybody got any ideas what the issue is? We are calling it overshoot. In it is acquiring the target then moving away.
Bob
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I have sent you an email.
BC
?
?
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So the buttons on my hand pad have started to stick. I have removed the back to clear any dust (there does not appear to be any). Looking at the yellow buttons, they seem to be "clip-on" buttons, but I see no way to remove them to try and clean them to stop them from sticking.? I am open to suggestions, replacement, or going to the GEN3 hand pad if there are any available and if they work with the older GEN2.
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Re: Interesting Alt/Az driver rate calculators
Mickey,
?
According to SharpCaps Robin Glover you should raise the gain untill the steep drop in read noise ends since raising the gain beyond that gives very little benefit pherhaps a loss in dynamic range even.
?
For my DSLR i can change ISO. When going from ISO 200 (best dynamic range) to ISO 1600 the read noise drops quite a lot to 2.05 electrons. But if I continue raising the ISO the read noise decreases very little.
?
I already use ISO 1600 so would ony have to take shorter subs!
?
I imaged yesterday without Astrolock and with 60s settle time for the mount.
?
It slewed and centered within 1 arc minute 3 times during the session (!) and tracking was perfect for 5 hours. I even slept 3 of those hours. When doing the 2-star i was very careful to make sure the mount had settled, since I can platesolve with 1 second, it can trick me in to believing that the mount has settled though it is still moving.
?
Gabriel?
?
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Re: Interesting Alt/Az driver rate calculators
Thank you Gary, I have always heard of atmospheric refraction and I have roughly understood the concept but this is the first time someone explains everything the way you just did, very interesting. Argo Navis is quite something. Someone on CN mentioned that it's all sky model you can create and use is as advanced as the one Software Bisque uses or if it was another high end AP mount manufacturer.
?
Gabriel?
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Re: Interesting Alt/Az driver rate calculators
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On Fri, Dec 27, 2024 at 06:27 AM, Gabriel Wiklund wrote:
With my EQ mount tracking at a constant rate with smooth guiding i just take it for granted, I don't even think about it.
Hopefully, if your equatorial mount is doing the ideal thing, its tracking rates aren't constant either.
?
This is because of atmospheric refraction.
?
The problem is that for any given elevation in the sky, the ?amount of ¡°lifting¡± to a star caused by refraction is different when compared to a star at some different elevation.
?
What¡¯s more, as the star advances across the sky in elevation, the amount of ¡°lift¡± is continually varying.
?
Plus within the FOV, points in the sky that are at lower elevations are ¡°lifted¡± more than those at higher elevations. The wider the FOV, the more the ¡°compression¡± within the image.
That also means there will still be some field rotation within the FOV on an equatorial telescope.
?
So the fact that your equatorial mount moves around its polar axis in a perfect circle can, in some ways, be considered a mechanical compromise, as the stars don¡¯t circle the sky in perfect circles.
?
Since the ?amount of ¡°lifting¡± to a star caused by refraction is different when compared to a star at some different elevation, that also means ideally the tracking rate will continually vary.
?
This also implies that the notion of a "perfectly polar aligned" mount is a myth. There is no magic part of the sky to which you can align an equatorial mount in azimuth and elevation and not get some field rotation.
?
Better to get off Earth where there is no pesky atmosphere and annoying Earth rotation. :)
?
Professional astronomers worked on various solutions and compromises to the atmospheric refraction problem with regards astrophotography as far back as 1893.
But fast forward to today, it is something many amateur astrophotographers haven't wrapped their heads around.
?
I bring this all up to simply enforce the point that there are additional subtleties beyond the fact that in alt/az mounts, like Dobs, the tracking rates need to continually vary.
Argo Navis even takes into account the additional subtle effect that the tracking rate is also changing irrespective of the mount type, because of atmospheric refraction as well.
?
?
--
Gary Kopff
Managing Director
Wildcard Innovations Pty. Ltd.
20 Kilmory Place
Mount Kuring-Gai NSW 2080
Australia
Phone +61-2-9457-9049
sales@...
https://www.wildcard-innovations.com.au
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Re: Interesting Alt/Az driver rate calculators
Thanks Gabriel and give Deep Sky Lucky Imaging a try. 1-3 sec exposure, I use max gain with my IMX 294c Astro camera, I am not sure how to set a dslr. Take at least 1000 frames minimum, the more the better.?
Mickey
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On Dec 27, 2024, at 9:33?AM, Gabriel Wiklund via groups.io <gabriel.wiklundholeshot@...> wrote:
? Hello Mickey,
?
Yes I agree as well, makes sense! Fingers crossed you get some clear weather soon. Aside from the new firmware I tried the latest Meade Generic driver and it works just like the one Serge first recommended.
?
Gabriel?
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bobrose500
Sam Selig
Gabriel Wiklund