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RA spikes during guiding with a new iOptron CEM40EC

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#1 Sasho_Panov

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Posted 18 July 2019 - 07:17 AM

I was testing my brand-new iOptron CEM40EC during the last few nights. 

Due to the rattling of RA axis (which is well described here on CN and on other forums) I have installed the new beta firmware upgrade from iOptron and this issues was reduced almost completely, so the RMS values of both RA and Dec axes are now simillar and pretty low (less than 0,4 arces with full Moon and poor seeing).

 

But, analyzing the guide logs, I noticed that other issue existed even before the firmware upgrade and that it continues after the upgrade: unexpected and intermittent large spikes of the RA axis.

 

Namely, RA axis made occasional spikes spending from 20 to more than 60 pixels. It is completely random, and as you can see from the attached logs, it happened once during one longer guiding session (more than 1 hour), but sometimes few such spikes happened during just 5 minutes of guiding.

It is happening using classic laptop-based PHD2 guiding and with ZWO’s AsiAir (also PhD2-based) control of the mount, so it is not related to the guiding software. I have also changed the USB cable with a new high-quality golden-plated contacts USB cable and it happened again.

It is very important that the guiding improved with new firmware, but those RA spikes were present in the guiding logs using the original firmware (190422), too, so it is unrelated tot he firmware upgrade. It is some electronic malfunction or other serious issue?

Last session, the RA spikes didn’t happened at all during more than an hour and although the RMS values were low (under 0.4 arc-sec) for both RA and Dec axes, the two guiding curves were completely separated: RA curve never reach zero baseline.

I am attaching a guide-log from the last night and a screenshot of PHD2 showing an isolated RA spike.

Since I am very upset with this issue, I will appreciate your opinions and suggestions. 

 

Let me say that, apart from that issue, I am very satisfied with the new CEM40EC.


Sasho

Attached Files



#2 gotak

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Posted 18 July 2019 - 07:39 AM

Was it even guiding at all? My experience with the test firmware was that it was not reacting to guide inputs. It did fix all the SDE and regular oscillations but it also does do as you describe, the large 12" spikes every so often. 

 

They are now avoiding providing beta as they feel people reacted very badly. Well, ok but I think the state of that firmware qualifies more as an alpha. 

 

They appears to have a handle of one problem. If only they can resolve the guiding and spikes they'd have a very good product.



#3 Sasho_Panov

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Posted 18 July 2019 - 07:54 AM

Was it even guiding at all? My experience with the test firmware was that it was not reacting to guide inputs. It did fix all the SDE and regular oscillations but it also does do as you describe, the large 12" spikes every so often. 

 

They are now avoiding providing beta as they feel people reacted very badly. Well, ok but I think the state of that firmware qualifies more as an alpha. 

 

They appears to have a handle of one problem. If only they can resolve the guiding and spikes they'd have a very good product.

Hi, thanks for the replay. It seems that there is a guiding and I succeeded to image a 900 seconds exposure with really round and nice stars.

But those RA spikes are driving me crazy although during the last session they doesn't appear for more than a hour.

I also worry why RA curve constantly float above the Dec curve.

 

Sasho



#4 Stelios

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Posted 18 July 2019 - 12:25 PM

I don't know anything about your issue. However, you have extremely low aggression which makes recovery from spikes take longer than it could. It could also explain why (not shown on your graph) RA never came back once separated. 

 

What I will say definitely is--don't put up with it! I had similar (but of unrelated cause) issues with DEC spikes on my AVX, and the only thing that fixed it, months later, was a replacement mount. If you can't get a satisfactory answer from CS, don't hesitate to send the mount back.



#5 rgsalinger

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Posted 18 July 2019 - 12:35 PM

If it does jumps up that much and there are no other problems then send it back. Many people use this mount and do not experience this. It's not periodic error, that's for sure. 

 

However, what looks odd to me is that you have set the guide scope focal length to 645 millimeters. Are you sure that's correct.

 

This kind of problem is more often than not caused by cables snags, passing clouds or wind gusts. It's really hard to picture software that would run for an hour giving excellent guiding and then suddenly mess up. You need to post the actual log produced by PHD so that there's more data for folks to look at. 

 

Rgrds-Ross


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#6 Sasho_Panov

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Posted 18 July 2019 - 12:59 PM

I don't know anything about your issue. However, you have extremely low aggression which makes recovery from spikes take longer than it could. It could also explain why (not shown on your graph) RA never came back once separated. 

 

What I will say definitely is--don't put up with it! I had similar (but of unrelated cause) issues with DEC spikes on my AVX, and the only thing that fixed it, months later, was a replacement mount. If you can't get a satisfactory answer from CS, don't hesitate to send the mount back.

Thank you for the replay, Stellios. I bought the mount in neighboring Greece, so it is not easy to return it back and for them to send it back to iOptron. Those things doesn't go easy in Europe, especially in the Southern smile.gif.

 

The mount seams very good manufactured, though. I really don't know what to do. The successfully captured images are really nice with low eccentricity. It is a huge improvement to my LX85 (with which I have produced some nice images.

 

If you have some advice, please tell, me. It was very your opinions that I read about here on CN forums that lead me to my decision that is is time to upgrade to a better and more sophisticated mount.

 

Best regards,

Sasho



#7 Sasho_Panov

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Posted 18 July 2019 - 01:02 PM

If it does jumps up that much and there are no other problems then send it back. Many people use this mount and do not experience this. It's not periodic error, that's for sure. 

 

However, what looks odd to me is that you have set the guide scope focal length to 645 millimeters. Are you sure that's correct.

 

This kind of problem is more often than not caused by cables snags, passing clouds or wind gusts. It's really hard to picture software that would run for an hour giving excellent guiding and then suddenly mess up. You need to post the actual log produced by PHD so that there's more data for folks to look at. 

 

Rgrds-Ross

Hi Ross,

 

Thanks for replaying. The guiderscope focal length is correct since I use OAG so the original FL of the scope (805 mm) reduced  0.8X by the focal reducer/field flattener = 645 mm. The AsiAir reported the actual FL as 645 mm.

 

I noticed that I can't place attachments in my replays (as this one) so I can't send PHD2 guide and debugger logs.

 

All the best,

 

Sasho



#8 John Miele

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Posted 18 July 2019 - 01:45 PM

Sasho,

 

Many people DO experience this RA spike issue, myself included. Although not quite to this extent, I have seen RA spikes it on my CEM60EC and they have nothing to do with poor seeing, wind, cable snags, or bumping the mount. There are several looong threads on the mount forum trying to debug the CEM60EC mounts from a myriad of problems such as rapid RA oscillation, overreaction to guide pulses, divergent RA guiding, and these random RA spikes. And now apparently the CEM40EC is beginning to exhibit encoder issues as well. ioptron seems to be working hard to develop software/firmware fixes to correct these problems, but so far the problems are real and are present in many of these mounts. They better get it together real soon, or their EC sales are going to tank. Personally I have been waiting months for a fix that has still not arrived and I'm getting darn tired of it.

 

John



#9 Sasho_Panov

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Posted 18 July 2019 - 03:38 PM

Sasho,

 

Many people DO experience this RA spike issue, myself included. Although not quite to this extent, I have seen RA spikes it on my CEM60EC and they have nothing to do with poor seeing, wind, cable snags, or bumping the mount. There are several looong threads on the mount forum trying to debug the CEM60EC mounts from a myriad of problems such as rapid RA oscillation, overreaction to guide pulses, divergent RA guiding, and these random RA spikes. And now apparently the CEM40EC is beginning to exhibit encoder issues as well. ioptron seems to be working hard to develop software/firmware fixes to correct these problems, but so far the problems are real and are present in many of these mounts. They better get it together real soon, or their EC sales are going to tank. Personally I have been waiting months for a fix that has still not arrived and I'm getting darn tired of it.

 

John

Many thanks for your support, John. I really don't know whether to wait for new updates or to return the mount. It is not easy to ask for replay, considering I bought it in other country, and I am not sure that the new one would be better than this. Otherwise, it is surprisingly good manufactured and very good looking mount, though.

 

Regards, Sasho



#10 Sasho_Panov

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Posted 18 July 2019 - 03:45 PM

If it does jumps up that much and there are no other problems then send it back. Many people use this mount and do not experience this. It's not periodic error, that's for sure. 

 

However, what looks odd to me is that you have set the guide scope focal length to 645 millimeters. Are you sure that's correct.

 

This kind of problem is more often than not caused by cables snags, passing clouds or wind gusts. It's really hard to picture software that would run for an hour giving excellent guiding and then suddenly mess up. You need to post the actual log produced by PHD so that there's more data for folks to look at. 

 

Rgrds-Ross

Hi Ross. The moderator move the parallel thread that I posted to Mounts forum and merged to this one, so now the PHD2 guide and debagger logs that I have originally posted are available. I also forget to add that it was a windy night indeed. Thanks


Edited by Sasho_Panov, 18 July 2019 - 03:49 PM.


#11 rgsalinger

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Posted 18 July 2019 - 04:32 PM

First of all, spikes of 12 arc seconds after an hour of good guiding are vastly more likely to be caused by something in the environment than they are by a defect in the mount firmware. So, I'd be looking at that more than anything else. 

 

Second, these guide logs don't match the picture in the other thread- even the focal length is different.

 

If this were my system the first thing I'd do is make certain that I was running the mount at .5 sidereal guide rate. I'd set aggression in both axes to 70 or 80 percent. If using an OAG make sure that every connection is tight and that the OAG is very well focused.

 

The calibration looks completely wrong to me. I think that the mount may have tracked to the meridian and then stopped - that's what it looks like. That would lead to a really bad guiding result. To avoid this, calibrate just WEST of the meridian (PHD doesn't care).

 

Rgrds-Ross 



#12 Sasho_Panov

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Posted 18 July 2019 - 04:49 PM

First of all, spikes of 12 arc seconds after an hour of good guiding are vastly more likely to be caused by something in the environment than they are by a defect in the mount firmware. So, I'd be looking at that more than anything else. 

 

Second, these guide logs don't match the picture in the other thread- even the focal length is different.

 

If this were my system the first thing I'd do is make certain that I was running the mount at .5 sidereal guide rate. I'd set aggression in both axes to 70 or 80 percent. If using an OAG make sure that every connection is tight and that the OAG is very well focused.

 

The calibration looks completely wrong to me. I think that the mount may have tracked to the meridian and then stopped - that's what it looks like. That would lead to a really bad guiding result. To avoid this, calibrate just WEST of the meridian (PHD doesn't care).

 

Rgrds-Ross 

Thanks once more for your analysis, Ross. I didn't want to write too much details and didn;t mentioned that I was using two scopes: one 115mm Apo triplet with FL 805 mm (645 with reducer) and other 70mm Apo quad Astrograph with FL 350 mm. ASI1600MM pro and ZWO filter wheel was used for imaging (controlled either by PHD2/SGP or ASIAR) and ZWO OAG with ASI174MM Mini for guiding. That is the reason why FL values differ in the PHD2 logs.

 

Calibration was performed on the cross of Meridian and the Equator, CW to east. This is perhaps problematic since it is just "before" Meridian flip.

 

I was using those scopes and imaging train with Meade LX85 for more than 8 months, so I have pretty much experienced with the setups and some good looking images are already on astrobin, here on CN gallery and Telescopius.

 

I thought that some bug in the firmware causes sudden, unpredictable RA spikes, but last session (more than 45 min) during the last night was without any of those peaks.

 

The seeing was very bad with full Moon and intermittent clouds and light gust, too.

 

I will really appreciate more suggestions. Thanks in advance, Sasho



#13 John Miele

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Posted 18 July 2019 - 05:40 PM

Please post your continued results here so we can see if it was just your environment or an actual issue with the CEM40EC. I hope your CEM40EC is not anything like the CEM60EC. TheCEM60EC problem is so far unsolvable and all  information related to ioptron encoder guiding is important. I'll keep an eye on this thread and go back to monitoring the other CEM60EC threads for progress.

 

One thing about your spikes is odd (to me)...why would a bump to the scope or other environmental factor only affect RA tracking and not DEC at the same time? That huge RA spike has no associated DEC spike...???

 

Thanks...John


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#14 Sasho_Panov

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Posted 18 July 2019 - 05:42 PM

Please post your continued results here so we can see if it was just your environment or an actual issue with the CEM40EC. I hope your CEM40EC is not anything like the CEM60EC. TheCEM60EC problem is so far unsolvable and all  information related to ioptron encoder guiding is important. I'll keep an eye on this thread and go back to monitoring the other CEM60EC threads for progress.

 

One thing about your spikes is odd (to me)...why would a bump to the scope or other environmental factor only affect RA tracking and not DEC at the same time? That huge RA spike has no associated DEC spike...???

 

Thanks...John

Thank you John. I will certainly post my new guiding logs and imaging results on CN. I hope it is not some electronic or mechanical defect in the mount and that some future firmware update could resolve the issues. The overall guiding is very good. Best regards, Sasho


Edited by Sasho_Panov, 18 July 2019 - 05:43 PM.


#15 OzAndrewJ

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Posted 18 July 2019 - 06:30 PM

Gday Ross

First of all, spikes of 12 arc seconds after an hour of good guiding

More like over 100 arcsecs, but im not sure i believe anything yet, and not sure they are "spikes" :-)

I downloaded the 2 sessions in post 1.

The long portion in log 1 shows quite ragged data for RA, ( with a lot of unidirectional guiding ) but the second section of log 2 shows really weird data, almost like a pattern that repeats at 170secs ( ie 2.33x worm )

I dont know what gearing is in the drivetrain, but also, i didnt understand why it didnt show in log 1.

I then loaded both datasets into PEMPro viewer and used his "remove guiding" function to show what the unguided plots would have looked like. I know this is only a reverse engineering approximation, but the results were remarkable :-)

Have attached what it shows for "calculated" raw tracking.

( edit! The PHD viewer analyse screen also does this sort of calc, but it removes the underlying drift )

I have no idea what has happened, and have never seen anything like it

For the second plot, the slope of each step adjust comes out "roughly" to sidereal rate, almost as if the mount had stopped tracking. 

Absolutely weird assuming the encoder was working

 

Andrew Johansen Melbourne Australia

Log1_Lastrun.jpg Log2_Lastrun.jpg


Edited by OzAndrewJ, 18 July 2019 - 06:46 PM.


#16 Sasho_Panov

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Posted 18 July 2019 - 06:34 PM

Gday Ross

More like over 100 arcsecs, but im not sure i believe anything yet, and not sure they are "spikes" :-)

I downloaded the 2 sessions in post 1.

The long portion in log 1 shows quite ragged data for RA, ( with a lot of unidirectional guiding ) but the second section of log 2 shows really weird data, almost like a pattern that repeats at 170secs ( ie 2.33x worm )

I dont know what gearing is in the drivetrain, but also, i didnt understand why it didnt show in log 1.

I then loaded both datasets into PEMPro viewer and used his "remove guiding" function to show what the unguided plots would have looked like. I know this is only a reverse engineering approximation, but the results were remarkable :-)

Have attached what it shows for "calculated" raw tracking.

I have no idea what has happened, and have never seen anything like it

For the second plot, the slope of each step adjust comes out "roughly" to sidereal rate, almost as if the mount had stopped tracking. 

Absolutely weird assuming the encoder was working

 

Andrew Johansen Melbourne Australia

attachicon.gif Log1_Lastrun.jpgattachicon.gif Log2_Lastrun.jpg

Hi Andrew, I was OP and it is a brand new CEM40EC mount. I am not sure if the guiding has stopped. As I already mentioned above, the RA spikes occur unexpectedly and if they don't, the guiding is very good with a RMS below 0.4 arsec. I have attached a screenshot of AsiAir-based guiding in this message. Here, no spikes occurred.

 

I will appreciate very much your opinion. Regards, Sasho

Attached Thumbnails

  • Screenshot_20190718-020037_ASIAIR.jpg

Edited by Sasho_Panov, 18 July 2019 - 06:52 PM.


#17 OzAndrewJ

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Posted 18 July 2019 - 07:09 PM

Gday Sasho

Just for info, can you do say a 10min unguided data grab at your current settings ( no need for hi freq yet )

This will at least give a baseline of the tracking, as other mounts have shown that when unguided, the encoder feedback works well, but guiding can really hurt it.

Some of your guides in the second log ran for 2.5 seconds and i have no idea what that would do to the encoders, as between the woofs, the mount ran quite well in several regions ( ie 0.25 to 0.35 and 0.41 to 0.54 )

Very very strange ( if the data is correct )

 

Also the logs posted so far are all guided and all show a heavy bias in the RA guiding, ie you have a lot of RA drift.

Your latest screenshot also shows RA is guiding in one direction only.

An unguided plot will show if that is real of an effect of guiding.

 

Andrew Johansen Melbourne Australia



#18 Sasho_Panov

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Posted 18 July 2019 - 07:15 PM

Gday Sasho

Just for info, can you do say a 10min unguided data grab at your current settings ( no need for hi freq yet )

This will at least give a baseline of the tracking, as other mounts have shown that when unguided, the encoder feedback works well, but guiding can really hurt it.

Some of your guides in the second log ran for 2.5 seconds and i have no idea what that would do to the encoders, as between the woofs, the mount ran quite well in several regions ( ie 0.25 to 0.35 and 0.41 to 0.54 )

Very very strange ( if the data is correct )

 

Also the logs posted so far are all guided and all show a heavy bias in the RA guiding, ie you have a lot of RA drift.

Your latest screenshot also shows RA is guiding in one direction only.

An unguided plot will show if that is real of an effect of guiding.

 

Andrew Johansen Melbourne Australia

Hi Andrew,

 

Thank you for your response. I will setup my scope tomorrow evening and I will record a unguided log, too. It is much easier to do that with AsiAir, and even this device actually use PHD2 in its operating system, the logs include only guiding, not debugger logs. Regards, Sasho



#19 rgsalinger

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Posted 18 July 2019 - 09:39 PM

"it happened once during one longer guiding session (more than 1 hour)" is just not something that is due to a poor encoder implementation, IMHO. Also, I am convinced that the calibration run started just east of the meridian as the mount was tracking to the west. Then when the mount hit the meridian it stopped but PHD just keep trying to move it. So the calibration in the run that I looked at was useless.

 

If you are not physically present at your mount so that you can see the odd passing cloud, dragging cable and/or wind gust, it's unlikely that you will ever figure out what's going on from a log. So, I definitely endorse any simplification that can be applied to the situation. It's important to isolate any mount problems from any environment or user issues because if it's the mount it needs to be returned if possible for replacement or repair. One other thing - you have not mentioned how you polar aligned the system. 

 

Rgrds-Ross



#20 Sasho_Panov

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Posted 19 July 2019 - 03:28 AM

"it happened once during one longer guiding session (more than 1 hour)" is just not something that is due to a poor encoder implementation, IMHO. Also, I am convinced that the calibration run started just east of the meridian as the mount was tracking to the west. Then when the mount hit the meridian it stopped but PHD just keep trying to move it. So the calibration in the run that I looked at was useless.nstalled

 

If you are not physically present at your mount so that you can see the odd passing cloud, dragging cable and/or wind gust, it's unlikely that you will ever figure out what's going on from a log. So, I definitely endorse any simplification that can be applied to the situation. It's important to isolate any mount problems from any environment or user issues because if it's the mount it needs to be returned if possible for replacement or repair. One other thing - you have not mentioned how you polar aligned the system. 

 

Rgrds-Ross

For polar alignemend, I was using the new preinstalled iPolar that was claimed by iOptron to be very precisse



#21 Sasho_Panov

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Posted 21 July 2019 - 06:54 AM

It seems that the culprit of RA spikes was guiding calibration.

 

Namely, if at the guiding calibration the scope was positioned at the intersection of celestial Equator and Meridian (duo to South), the beginning of guiding session is full of RA spikes that eventually calm down, but RA curve constantly “floats” above or under the zero line of PHD2 graph. More importantly, after 30 – 45 min, occasional, large, single RA spike occurred (PHD2 screenshot). The screenshot of PHD2 guiding assistant recorded at the end of that session is attached, too.

 

However, if guiding calibration was performed at the celestial position of the object that was to be tracked, or near it, the eventual guiding is almost perfect, considering Moon phase (84% illumination), seining and intermittent wind gusts (AsiAir screenshot).

 

The RA spikes doesn't occurred at all after that.

Due to the file upload restriction, I will attach the PHD2 logs (from both PHD2 and AsiAir) in the separate posts.

 

I want to thank to all of you that tried to help me and have sent your opinions and suggestions to me. I will keep you informed for further news.

 

Best to all,

 

Sasho

Attached Thumbnails

  • PHD2 guding with wrong calibration.jpg
  • PHD2 guding assistant after wrong calibration.jpg
  • ASIAIR_good calibration.jpg

Edited by Sasho_Panov, 21 July 2019 - 07:02 AM.

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#22 Sasho_Panov

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Posted 21 July 2019 - 06:59 AM

Here are the PHD2 guiding logs: one with "wrong" calibration in PHD2 and the second one after "good" calibration using AsiAir (also PHD2 in fact).

 

The PHD2 debug log is too large (>4 MB) so I can't attach it here. It will be interesting to see what trigerred the single, very large and short RA spake to East (down) during the 45 min session after the "bad" calibration.

 

Sasho

Attached Files


Edited by Sasho_Panov, 21 July 2019 - 07:19 AM.


#23 John Miele

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Posted 21 July 2019 - 01:40 PM

Interesting. It is normally recommended to calibrate pointing due south on the meridian. That is sort of a PHD2 best practice...confused1.gif



#24 gotak

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Posted 21 July 2019 - 01:47 PM

Are you running at sidereal or other rates?

And you know maybe a repeat experiment is required. It's very odd that calibration can make it better by being done in the not so great position.

#25 Sasho_Panov

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Posted 21 July 2019 - 02:09 PM

Are you running at sidereal or other rates?

And you know maybe a repeat experiment is required. It's very odd that calibration can make it better by being done in the not so great position.

Now, after recommendation from one of the posters, I changed the guiding rate from 0.9x to 0.5x. Maybe the celestial position is making the things better or worse. I will try different targets tonight.




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