Meridan flip failed...

philippe

Hi all,

Last night, I had a good and clear night.
I bought a new refactor and a new camera this month to replace my newton and ASI 294 Pro by an ASI 2600 MC Pro.
So yesterday, was a test night and I had planned to shoot IC1396.

My mount is an AZ EQ6, I use a Zwo OAG, a filter drawer (with Optolong L Pro), my 2600 MC Pro and an ASI 290MM for autoguiding.
My refractor is a brand new TS 102/714mm Apo Triplet I had already tested over just two previous nights.

I shoot from my observatory, and use the AA Plus to manage my sessions.

I did my P.A, I slewed to IC 3196 focused with my EAF, let my AA Plus calibrate and then autoguide, with an average RMS of 0,50.

A flip was shceduled an hour after my session started, I had planned to take 50 x 180 sec photos.

After 20 photos I came back next to my setup, I saw the countdown, and at the end of it this window opened up 😀 :

I was suprised as meridian flips were done successfully till november/december (my first 2022 semester was dedicated to the collimation of my former RC8 so didn't have opportunity for full session, and we had many months of bad weather).

I stopped the attempts as after a couple of minutes, the window kept displaying the same message, multiplying attempts...

I stopped the autorun sequence, restarted it with the last 30 photos I had planned, and the AA Plus ended the calibration that was occuring in parallell, and then proceeded with the second session !

When the first image turned up on my tablet I was surprised to find out that the system had done a "virtual" flip !

That is, my AZ EQ6 didn't move, but the AAPLus simply flipped th image !!!

The Garnet star was in the lower right part of the first part of my session, and on the remaining images, it was in the upper right part !!

The end of the session went smoothly, no issue, the AA PLus parked the mount and shutdown as planned !

I'm really puzzled, no error was logged in the log file ...

Any idea ?

Philippe

w7ay

Philippe,

Looks like (from the post-meridian screen capture) shows that the Meridian flip actually succeeded, however, the plate solve to recenter the target failed.

Take a look at the bottom of your last image: it shows that "the next meridian flip" is 11 hours 58 minutes away. This is when the target that is circumpolar passes the "other side of the" meridian (the part of the great circle between the pole and Nadir).

What this means is that the object has crossed the prime Meridian (the part of the great circle between the pole and Zenith) about 2 minutes ago, and as you described, the image is inverted, which can only happen if the camera angle has passed theough a 180º rotation (due to a meridian flip). Further, there are no trailing stars, and the guide graph is running normally, which means tracking and guiding have also been turned back on. -- that only happens after a meridian flip.

That "retrying" window will keep repeating every minute until it succeeds or give up. I don't know how many times it tries, since I do not use the auto meridian flip function in ASIAIR, and also not asking ASIAIR to auto center. I use ASIAIR purely manually.

It is not abnormal to get the retry message (for example, if the Local Sidereal Time has a small mismatch, or your mount is not perfectly level or sync'ed). However, it should finally succeed.

The failure to recenter could be caused by a failure to plate solve. Check the Mount Settings and look for the GoTo Auto-Center switch. Be sure it is turned on (if you want to recenter after a meridia flip) and the Center Exposure Time is apppriate for the filter and gain that you are using. If you are not using a narrowband filter, you can try using either 2 seconds or 5 seconds for your exposure time, since I notice you have the camera gain set to 100 (10 dB).

Chen

philippe

w7ay

Hello Chen

First of all, thank you for your quick answer.

I know what a meridian flip is, and had to go through many of them, successfully. ;-)

But anyway, your pedagogical answer will be helpful for people who don't know what it's all about. ;-)

No, my suprise comes frome the fact that, I was standing by my setup, and the mount didn't rotate and slewed to the opposite side as it used to do during a meridian flip !

It stayed still, no move, is this normal ?

Can, under some specific circumstances, a meridian flip occur without moving the mount !?

Apparently, it didn't prevent the ASIair to continue with the last 30 remaining images after I've reset the autorun session, and re-enabled the 30 remaining images, and the mount kept tracking and guiding till the end, that's the positive side.

However, all of the meridian flip I've seen (of course, I'm not always close to my setup when they occur ! ;-) ) involved a change, a rotation moving the mount head on the opposite side as said above !

Regarding the failed centering I may have an explanation Chen, however, I'm not quite sure it's the right one or the reason why it took so long: indeed, for this specific session I had manually changed with the new window (with the FOV Cross), the position provided by the ASIair to further include the Garnet star, so in this case, with a different "framing", when a meridian flip occurs, will it take into account the framing selected before the flip ?

Last question, as previously said, the ASI 2600 is brand new, this is my second session with it, the ASIair automatically selected the gain 100 when I connected to the ASIair App, and I found out that this is the maximum gain currently available that can be selected, so you confirm that till the next firmware or ASIAiar app upgrade, I can only change the exposure time ?

Philippe