Failed meridian flip with NINA

[Richard_]

I've been using NINA for a couple of months and up until now I haven't experienced any issues with my meridian flips. I have been shooting M101 Pinwheel galaxy over three past few nights and every time I shoot it I get problems after the meridian flip which stops the imaging session unless I intervene. I've imaged other targets in this region of the sky (M81, UGC 7306) with the same (mostly default) meridian flip settings without issue. I've increased the settle time after flip and also the time to wait after passing the meridian before flipping but I still get failures. The only thing I can think of is that M101 is very close to the zenith (87°) whilst M81 and UGC 7306 are lower down (73° and 72° respectively) so perhaps my mount has some safety limits in the EQMOD ASCOM driver which is preventing it from doing the flip? Is there something I'm missing?

Details

On the first night, the autofocus routine appeared to keep looping and never achieving focus. Focus was OK all night (HFR did not change more than 10% from first autofocus). I disabled the forcing of autofocus after the meridian flip and set out for the second night of imaging.

On the second night, the meridian flip was performed but the plate solving failed (ASTAP) as the image had star trailing present. I could only assume that the mount was still slewing while it was taking the plate solve image. The screenshot below shows NINA when I checked it at 6am the following morning. I increased the scope settle time from 30s to 90s thinking that 30s was not enough time to settle and I also increased the time after meridian from 5 minutes to 10 minutes.

On the third night I woke up to find another failed meridian flip with star trailing observed on the images for plate solving. So it looks like upping the settle time and time after meridian did nothing.

• Software: NINA v2.0 BETA
• Mount: Skywatcher EQ6-R
• Plate solver: ASTAP

 

 

 

[Ibbo!]

What have you set the exposure to in plate solving?

 

I have increased mine due to similar problems with the RC IIRC I set it to 30 secs -I'm using CCD.

 

 

[Richard_]

1 minute ago, Ibbo! said:

What have you set the exposure to in plate solving?

 

I have increased mine due to similar problems with the RC IIRC I set it to 30 secs -I'm using CCD.

 

 

2s using a OSC CMOS camera using just a UV-IR filter (sorry for lots of acronyms). This works perfectly fine when plate solving outside of the meridian flip part. The star trailing I see is excessive, each star traverses halfway across the screen.

[david_taurus83]

If it was working fine before I would suggest updating NINA. Current nightly version is 056 and you have 045 in those screenshots.

[scotty38]

Did you focus after the flip as the HFD seems low and not many stars detected? Just a thought as to why the solve may have failed????

[Richard_]

2 minutes ago, scotty38 said:

Did you focus after the flip as the HFD seems low and not many stars detected? Just a thought as to why the solve may have failed????

Looking at the screenshot I posted, this appears to be the final image taken before it gave up on the second night. My HFR was just under 4.0 and as you can see in the background behind the NINA error messages, it stayed pretty flat all night (it didn't even trigger an autofocus). The HFR is high in the plate solve image due to some very slight star trailing so in actual fact it appears that the 90s settle time and 10 minute post meridian wait time are enough, it just looks like the mount has stopped tracking.

[sloz1664]

The areas around M101 & M51 are not a great area of sky for stars. PlateSolve needs around 30 stars to work correctly. I am currently using a f/l of 1700mm and a PlateSolve 50s. Any lower and it fails. To prove you are obtaining the amount of stars to PlateSolve successfully take an image with your 2s exposure and check the amount of stars you can see, if needed, increase your exposure until thr required star count is met. With regards to your excessive star trailing, increasing the mount settling time should help.

 

Steve 

[Realtimedoctor]

Hey,

Can I ask what scope your are using? 

I wonder if the problem is being caused by your equipment striking the mounts tripod. As there are legs on the east pointing west side of the EQ6R-Pro tripod, it's possible that with such high altitude of almost 90 degrees, your equipment is hitting one of the legs and not completely flipping. 

That would explain the exorbitant star trails as the mount keeps trying to finish the slew to the flip side. Or worse yet, stops tracking momentarily/completely due to excessive stress on the motors. 

90s is a lot of time to settle. Even with a lemon of a mount and massive backlash, you'd have the gears engaged and tracking by the 90s runs out. 

 

 

Cheers, 

Nish 

Edited March 29, 2022 by Realtimedoctor

[Padraic M]

I get the same problem from time to time with NINA. Quite significant star trailing in the platesolve subs after a meridian flip. It's not related to the settle time - I now use 8 seconds as default, and mostly have no issues. My second choice plate solver is astrometry which has as an advantage that the platesolve subs are saved online in your account, so you can see the subs used for platesolving. Astrometry can normally solve even with badly-trailed stars, so as an interim fix, you could try that.

While it could be a bug in NINA, I suspect that it could alternatively be related to PHD2 settings - if PHD2 can't select a suitable guide star after the flip, guiding will stop. I had that issue earlier this week when I upgraded PHD2 to the latest version, and some of my guiding and camera settings changed (constantly getting "Star Lost" messages). Reverting back to the old version with the old settings fixed the issue. It doesn't explain why the star trails are so long without guiding, as the mount should still be tracking at sidereal rate. Even if the mount wasn't tracking at all it still shouldn't cause trails this long in 8 seconds (my default exposure for platesolving). 

 

Here's an example of a platesolving sub that Astrometry couldn't solve, and a second example of a trailed sub that Astrometry solved successfully. 

Success:

 

If I get a chance later tonight, I'll calculate how long those trails are in arc-seconds and compare that to sidereal rate.

Edited March 29, 2022 by Padraic M

[Clarkey]

On 29/03/2022 at 19:09, Richard_ said:

I've been using NINA for a couple of months and up until now I haven't experienced any issues with my meridian flips

I had my first flip failure with NINA the other night. I looked through guide logs and error logs and could find no reason. I put it down to the clocks going forward - but it was a guess. There was no plate solving errors. I also had a similar problem with the autofocus routine running for ages and by the morning the focus was a mile out. Oddly, I am still running the old version of NINA so mine was not a bug in the Beta software.

I was at a loss, so for now I have put it down as a one off glitch. (Interestingly I had two imaging rigs at different FL's out on the same target - one failed one worked fine). Same computer running both scopes (mini PC's)

[StarryEyed]

I'm not in front of the computer but from recollection there is a setting in plate solving for retries and a delay between them. I have used this and it resolved this problem for me. Didn't stop the trailing but allows you to get past it. As I don't guide I also break the session down into twenty minutes duplicate the session so NINA preforms another goto the same target and recenters. Not much time lost other than a couple of minutes for plate solving and a small slew. Keeps things centred and makes everything almost self checking. 

[scotty38]

44 minutes ago, StarryEyed said:

I'm not in front of the computer but from recollection there is a setting in plate solving for retries and a delay between them. I have used this and it resolved this problem for me. Didn't stop the trailing but allows you to get past it. As I don't guide I also break the session down into twenty minutes duplicate the session so NINA preforms another goto the same target and recenters. Not much time lost other than a couple of minutes for plate solving and a small slew. Keeps things centred and makes everything almost self checking. 

With NINA's advanced sequencer you can have triggers set that will automatically force recentres should the target drift by a predetermined amount.

[StarryEyed]

I noticed this in the beta version which I recently switched to. Is the same functionality in the sfandard version? I wont be going back to the standard version the exoplanet plugin is just so easy to use its a  game changer. 

[scotty38]

No I don’t think the concept of triggers exist in the basic sequencer but I’ve not used it in ages anyway. 

[Rallemikken]

On 29/03/2022 at 20:09, Richard_ said:

I've been using NINA for a couple of months and up until now I haven't experienced any issues with my meridian flips. I have been shooting M101 Pinwheel galaxy over three past few nights

 

Done M101 myself recently.  It was almost straight above my head, and guiding was a nightmare. Can't this be at least a part of the trouble?

[Richard_]

Sorry for the delay in responses. I've had a little play around with my mount limits and in NINA I put a 10 minute delay before and after meridian. Next time I image M101, it'll be interesting to see if this has resolved my issues. I'll also need to check out the advanced sequencer as there may be a smarter way to resolve the issue specifically for this target rather than setting general rules! Thanks for all your suggestions

 

On 29/03/2022 at 20:59, Realtimedoctor said:

Hey,

Can I ask what scope your are using? 

I wonder if the problem is being caused by your equipment striking the mounts tripod. As there are legs on the east pointing west side of the EQ6R-Pro tripod, it's possible that with such high altitude of almost 90 degrees, your equipment is hitting one of the legs and not completely flipping. 

That would explain the exorbitant star trails as the mount keeps trying to finish the slew to the flip side. Or worse yet, stops tracking momentarily/completely due to excessive stress on the motors. 

90s is a lot of time to settle. Even with a lemon of a mount and massive backlash, you'd have the gears engaged and tracking by the 90s runs out. 

 

 

Cheers, 

Nish 

Hey Nish. I'm using a William Optics FLT120 (120mm refractor). My mount limits are default so haven't been changed in any way. I checked them out yesterday morning and they are a little generous side. I opened them up a little bit my slewing the mount in RA until the camera was close to the tripod leg (about half an inch) and slewed the declination back and forth to ensure they didn't contact. I then registered these new positions on West and East side of the tripod (see "Before" and "After" images below). I'll double check these are correct on the next night before letting it perform a meridian flip unattended.

Before - Default limits

After - New limits set

 

On 29/03/2022 at 21:38, Padraic M said:

I get the same problem from time to time with NINA. Quite significant star trailing in the platesolve subs after a meridian flip. It's not related to the settle time - I now use 8 seconds as default, and mostly have no issues. My second choice plate solver is astrometry which has as an advantage that the platesolve subs are saved online in your account, so you can see the subs used for platesolving. Astrometry can normally solve even with badly-trailed stars, so as an interim fix, you could try that.

While it could be a bug in NINA, I suspect that it could alternatively be related to PHD2 settings - if PHD2 can't select a suitable guide star after the flip, guiding will stop. I had that issue earlier this week when I upgraded PHD2 to the latest version, and some of my guiding and camera settings changed (constantly getting "Star Lost" messages). Reverting back to the old version with the old settings fixed the issue. It doesn't explain why the star trails are so long without guiding, as the mount should still be tracking at sidereal rate. Even if the mount wasn't tracking at all it still shouldn't cause trails this long in 8 seconds (my default exposure for platesolving). 

 

Here's an example of a platesolving sub that Astrometry couldn't solve, and a second example of a trailed sub that Astrometry solved successfully. 

Success:

 

If I get a chance later tonight, I'll calculate how long those trails are in arc-seconds and compare that to sidereal rate.

Thanks for the suggestion on the second plate solver, Padraic. ASTAP was set as my primary but I've now assigned Astrometry as my blind solver!

 

10 hours ago, scotty38 said:

No I don’t think the concept of triggers exist in the basic sequencer but I’ve not used it in ages anyway. 

You are right, Scotty. Although I have the option of using the advanced sequencer I've continued to use the basic sequencer which doesn't have triggers. I may look into figuring out how to use the advanced sequencer if it means I can put a "pause" time between meridian flip and make it a bit smarter.

 

1 hour ago, Rallemikken said:

Done M101 myself recently.  It was almost straight above my head, and guiding was a nightmare. Can't this be at least a part of the trouble?

During setup I perform my guiding calibration towards the south, pointing upwards towards the zenith. In my scenario, I don't see any bigger challenges guiding this high above as I do for other targets in the vicinity. See below quote from PHD guiding which may help.

Quote

 In general, the best practice is to get a good calibration within about +/- 20 degrees of the celestial equator and high enough in the sky to avoid major seeing (turbulence) problems.

https://openphdguiding.org/man/Basic_use.htm#Automatic_Calibration

 

Edited April 3, 2022 by Richard_

[Rallemikken]

46 minutes ago, Richard_ said:

 

48 minutes ago, Richard_ said:

During setup I perform my guiding calibration towards the south, pointing upwards towards the zenith. In my scenario, I don't see any bigger challenges guiding this high above as I do for other targets in the vicinity. See below quote from PHD guiding which may help.

Not using NINA. Im an Ekos/INDI user. In Ekos the internal guider does a complete calibration after each slew. Done in two minutes. And it is done pointing to the target you soon are to image......  Picks up perculities regarding unbalance, wind etc. After guiding is active, I give it half a minute to "settle", the curves tends to flatten out a little. If you are imaging 2-3 hours, this is well worth your time.