Need additonal settings or controls for the meridian flip

vladi

On the ASIAIR Facebook group, I recently reported the meridian flip as working with my Sky Watcher AZ GTI and it actually still does. IMHO, an important feature is missing. What is missing is an ability to do a manual meridian flip to prevent running in the middle of a sequence or enforce the mount orientation after the meridian flip. Yesterday, my story was as following. I framed the envisioned FOV, stored its position as a custom target and setup a 2h sequence for this. ASIAIR reported an upcoming meridian flip in 30m. The meridian flip worked as such. Yet, I was unsatisfied with the FOV after the flip and decided to "go to" the original position via the stored coordinates. Surprisingly, instead of just correcting the FOV with stored coordinates, ASIAIR did not consider that the meridian flip had already happen and moved into the position prior meridian flip. Here I decided to leave it as-is in order to save time. After a while, the mount and whole setup looked really weird to me and I decided to better try to reach the after-meridian-flip orientation to avoid mechanical problem. I did a "go to" to the stored coordinates again and this time the after-meridian-flip orientation was considered. For me, it looks like almost a bug, since as user I would expect that the "after-meridian-flip orientation" should be stored for a given sector in the sky once it has been reached. It would also be great to have an option to even select which orientation to use and also enforce a flip before the scheduled time. For example, ASIAIR could ask the user "A meridian flip is needed in 30 min. Do you like to apply the new, flipped orientation now?". Am I missing something? The whole story cost me almost 1h in total yesterday night. This is quite some time... I think it would be worth adding this option

darkmatter

I'll second this request, as well as being able to set how far from the meridian the flip is performed. Not all scopes and mounts are created equal after all. Yesterday my ASIAIR would happily have run the filter wheel into the tripod leg if I hadn't canceled the goto command.

w7ay

Hi Markus,

ASIAIR v1.5 Beta has these two parameters under the Meridian Flip Settings in the Telescope Settings window:

Stop tracking x mins before Meridian

Do AMF x min after Meridian

Looks like they might be what you are looking for.

Because of smoke from nearby forest fires and now rain and clouds, I could only test the Beta indoors. Other than not completing the plate solving part of the auto Meridian flip in the daytime, it appears to work fine on my RainbowAstro mount, with both parameters set to 1 minute. The ASIAIR used to wait between 250 seconds to 450 second before doing the second step, and wasting valuable imaging time. (We will now waste valuable imaging time to do auto refocusing, ha ha -- incidentally, automatic refocusing has two parameters, Run Auto Focus in AutoRun every xº change (you need to buy the optional temperature probe), and Run Auto Focus in AutoRun every x hours).

I checked it by pointing the mount (indoors) at a star that is about to cross the Meridian, and can confirm that the ASIAIR report (in the AutoRun window) for "time before Meridian flip" agrees with the hour angle of the object in SkySafari, and it performed the two above steps (stops tracking at the first step, and issuing a GOTO to the mount to perform the second step) within a second of the correct times.

Since the Median Limit of my mount is set to 2 degrees, I could have set the first parameter to -1 and the second parameter to 0 to save even more time, but I thought that would be pushing my luck (and I wasn't sure ASIAIR would take negative numbers).

Chen

vladi

I'm glad that this topic picks up on interest! Thanks! I will see how 1.5 works, but these two new parameters do not sound to me as something related. I was watching 3-4 meridian flips in the last two month. On my Skywatcher AZ GTI, all of them worked as expected. There was never a long buffer time before the flip started. Last time, a new subframe of 150sec has been stated even though there were just 60 seconds before the flip. And this subframe was finished well too. So no complains at all in general. My impression each time is still that the FOV is not 100% the same as before the flip. Maybe, I'm mistaken - I did not do any calculations. Anyways, It would be good to get some controls as I mentioned, since if something is not correct, this will cost de-facto more time IMHO than any wait times built-in. I searched the forum before posting and there was at least one request for similar features.

w7ay

Sorry, but I was responding to Darkenergy (who I mistook for Markus (a.k.a. Darkmatter) ) about the two Meridian Flip parameters, and not to your issue.

My post Meridian flip positions has errors mainly in declination, and very little in RA. It is not something AstroPixelProcessor cannot handle, so it has not bothered me. I have been primarily using APS-C sensor sizes (ASI071 and ASI2600) so I can afford to crop with most objects, which I need to do anyway since I set my dither to 10 pixels.

If you run the public Beta of ASIAIR later, just send feedback through the iOS TestFlight app that this is an issue for you.

Chen

darkmatter

Sorry, but I was responding to Darkenergy (who I mistook for Markus (a.k.a. Darkmatter) )

Looks like you're still mistaken, since my name isn't Markus...

Anyway, it's nice to know that we might soon have more control over the meridian flip. My scope is a TS 130mm f/7 triplet apo and it's very objective-heavy. The balance point is about 2/3 of the OTA length towards the objective so the scope extends a long way at the focuser side and thus has a high risk of encountering a tripod leg. Having the filter wheel sticking out makes matters even worse.

It'll be interesting to see how accurate the meridian flip is on the Avalon Linear but so far my goto's have been quite precise. What mount are you using?

Jarno, a.k.a. Darkmatter ;)

w7ay

Hi Jarno,

I thought I was responding to Darkenergy, whose name is Markus :-).

My apologies, in any case.

The Telescope Settings in an old ASIAIR version used to have a user settable bound that it strives to achieve by successive retries after an auto centering GOTO. I no longer see it in v1.5 Beta (v1.5 only has an Auto-Center exposure time parameter), or if ZWO is using the same error limit when it does a Meridian flip.

If you are still running v1.4.4, you might want to check if the parameter is in there (it might have been an older version) and if it also applies to a Meridian flip.

I have not had the opportunity to try v1.5 Beta under dark skies yet to check out position accuracy after an auto GOTO or auto Meridian Flip. First possible opportunity is this Sunday/Monday night if the smoke from the forest fires don't keep me from going outdoors. If I find out anything interesting, I will report it to this thread. It should be easy to check by doing an extra manual plate solve when ASIAIR think it is done.

Chen

astrosatch

Another setting should be change filter for meridian flip to L. I have 3.5nm filters and often just cannot plate solve because of to dim stars. Even when exposure set to 10 seconds.

w7ay

I just tested a GOTO that includes a Meridian flip (with GoTo Auto-Center turned on) on ASIAIR 1.5 Beta (build 10) and the RA error came out to be about 1.5 minutes (about 23 arc seconds), with Declination error of about 50 arc seconds.

Whether that is excessive, depends on your situation.

The plate scale used in the above is about 3.1 arc seconds per pixel (WhiteCat51 with ASI2600). So the meridian flipped GOTO is off by something like 7 pixels in RA, and 16 pixels in Declination. Seeing that I dither by 10 pixels, the error is acceptable to me, considering the camera has over 6k x 4k pixels. It is pretty much also acceptable for my FSQ-85 (455 mm focal length) with the same camera.

If you are using a much longer focal length OTA, or use a camera that has much smaller pixels, and either not dithering, or using a small dither, it may not be accurate enough for you.

Chen

w7ay

Aha, after an auto Meridian flip (v1.5 Beta, Build 10) last night after I went to bed, the RA was off by 350 pixels (about 16 arc minutes) and Declination was off by 120 pixels.

That is a rather large error.

Chen

darkmatter

Interesting information, thank you. Doesn't the error after meridian flip also depend on the accuracy of the mount and orthogonality of the scope?

Jarno

w7ay

Hi Jarno,

Orthogonality ("cone error") should not affect the post-Meridian Flip accuracy though, as long as the ASIAIR is really performing plate solves during the Meridian Flip process.

Fortunately, I usually crop like crazy anyway on both my ASI2600 and ASI071, so being off is not a problem (yet).

I looked in v1.5 Beta and I could not find an auto-center accuracy setting any more.

When I do my own successive GOTO (without using ASIAIR's Auto Centering), I can get the plate to be within 1 arc second in both RA and DEC settings (RainbowAstro RST-135 mount). So we know that it is possible to get accuracy with repeated refinements. When I use Auto Centering, the ASIAIR claims the error is small enough even when the error is still too large for my tastes. So I have stopped using ASIAIR's Auto Centering.

Chen