USA
IPAD
Celestron AVX
ZWO ASI 1600MM pro
ZWO EFW

My issue is with the focal length in preview and trying to plate solve. My OTA is a ASKAR fra 400 with an FL of 400MM. I have used 0MM and 400MM as the focal length. Each time I plate solve it defaults to a focal length of 79533MM. Of course with that setting plate solving fails.

I have tried restarting every thing, camera, AAP, Mount etc. Nothing changes still defaults to the 79533 FL.

Suggestions please

I have a screen shot that i cannot seem to get to upload.

  • w7ay replied to this.

    rfulen01 I have used 0MM and 400MM as the focal length. Each time I plate solve it defaults to a focal length of 79533MM.

    From my observations, ASIAIR will always start with the focal length that is entered into the Focal Length field in the Main Camera Setup window.

    When plate solving succeeds, it will update that field. If you enter zero (the preferred way if you are not 100% certain of the focal length to a couple of percent) ASIAIR will search a larger set of asterisms.

    Be sure to tap on the focal length field to select it, then clear the field, and then type a single zero, and then type Enter on the virtual keyboard after you have selected the camera. To be certain, leave the Main Camera Setup window, and open the main camera window again to check that the field is still zero.

    Then capture an image of the stars and execute a plate solve. Be sure that your focus is tack sharp, and that the skies are fully dark, with no objects (tree branches, chimneys, etc) that cast a dark shadow into the frame.

    For this season, M45 is a good place to plate solve at to get an initial focal length from zero, since the Pleiades has a nice tight, distinct asterism with moderately bright stars to make plate solve easy.

    If ASIAIR is still starting with some ridiculous focal length, there is some weird ASIAIR bug concerning what it thinks the pixel size of your sensor is, but I haven't read of any ASI1600 specific plate solve problem. You may need to clear any ASIAIR app preference after removing the app from your iPad, then re-download a new copy of the ASIAIR app. If you have a second iPad or iPhone, you can also start fresh from there.

    If you do not start from zero focal length, make sure you factor in the Askar's reducer. It is best to start with zero, especially with a reducer since any small change to the back focus will change the true focal length by a lot.

    Chen

      I did do each of those with the exception of deleting and redownloading the APP. Also this was during a full moon so do you think the excessing light could have been an issue?

      • w7ay replied to this.

        rfulen01 Also this was during a full moon so do you think the excessing light could have been an issue?

        In general, the answer is yes (the Moon will reduce the signal to noise ratio and thereby make star detection problem more difficult). A narrowband filter will often improve it, as long as you bump the exposure time up to capture sufficient stars.

        However, from your description, ASIAIR is plate solving by starting with a ridiculous focal length. It seems that plate solve does not even have a chance to start with a focal length of 0.

        Have you tried sending the captured image to astrometry.net? There is a web tool at astrometry.net to plate solve. It will accept virtually any image format (from JPEG to PNG to TIFF to FITS). It takes a little longer (sometime a few minutes, when their computer is overloaded), but if astrometry.net will not solve, practically nothing else will.

        astrometry.net will not return the focal length since it does not know what sensor/camera you are using. It will return a plate scale, and from there, knowing your own camera's pixel pitch, you can derive the true focal length.

        However... if ASIAIR did not take "0" as the starting focal length, it also may not take the focal length that you derived from astrometry.net.

        It seems that your root problem is not being able to start plate solving at some reasonable focal length (or zero).

        Check carefully again when ASIAIR is plate solving. When it is trying it, you will see an intermediate screen. That screen will show the focal length ASIAIR is starting at.

        If the intermediate screen is showing zero, then ASIAIR is always solving to some silly focal length instead of starting at some silly focal length.

        One reason could be that there is some hot pixels that ASIAIR is mistaking for a known asterism of stars (you can check if it is doing that by capping your telescope, even in the daytime). But I am under the impression that ASIAIR should be rejecting bad pixels (easy to do) before it plate solves. You have to be really unlucky (like winning the lottery type of chance) that hot pixels form a known asterism of real stars.

        It would be better if you could post an image we can look at. Without the image that you are trying to solve, I am really flying blindly making guesses. With an image, we can at least narrow down the thousands of possibility why plate solving failed for you.

        Chen

          Hi folks
          I try yesterday few things to understand why the plate solving do not work at all with my RC 2000/254 with my asi 294 mc pro Asiair non pro.
          I spend nearly 3 hours to find out what's wrong.
          I used my redcat 51mm with the same mount a CGX and it works fine due of a large quantity of stars to detect.
          So I try different exposure time and official focal length and the 0mm focal length.
          It does found in average 180 stars with the gain on max and the exposure time on 10 sec!
          Strangely for any reason rarely it get a plate solve in less a sec with 210 stars found. This is all about to use the PA in that area are less stars indeed. For any reason it found a solution after 8.4 sec of plate solving to know where it is and did the 60° tilt of the mount and after it was lost again it could not solve any plate anymore. I stopped after 2 hours of testing focal length and exposure time but nothing. That one was a chance just because it found in the area enough stars.
          But it should recognise the patern of the stars too what it did before without problems before this upgrade.
          So for shure there is a patern issue with the plate solving on larger telescope specialy on longer focal length.
          The POV is 0.55° x 0.37°
          I hope this helps Zwo to find a solution.

          Kind regards.

          • w7ay replied to this.

            kellimtai Asiair non pro.

            According to the ASIAIR User's Manual, the original ASIAIR only supports Plate Solving for an FOV that is greater than 0.4º .

            When you are just outside the 0.4º range, it may sometimes work and sometime not work, depending on the number of asterisms that it finds in your camera's FOV. Sometimes, changing the camera angle will give it more asterisms to work with.

            Unfortunately, you will need to either use the v2 ASIAIR, a reducer for your telescope, or a camera that has a larger sensor.

            Chen

                I have an 8se with a focal length of 2080. Plate solving works most of the time if the sky is clear. So the focal length is not a problem. I find that bin4 works well as it makes the stars smaller.

                Rog

                  w7ay hi thx for the info.
                  Well I do some analyses and of course putting a reducer will more make trouble to my images. So I need to stay as much native as possible. The idea of a biger sensor is a solution. So the best will be to pass to the Asiair pro but what is the minimum FOR with it?
                  Then this could me my next item.

                  Kind regards

                    Plate solving requires sharp round stars.. With such long focal lengths the stars can get bloated and cover many pixels. The software then rejects them as stars (DSS will also reject them). By binning, the star size is reduced and made sharper and any noise wont be mistaken as a star,
                    I notice that you are using full gain. Try dropping it to cut down on noise and false stars.

                    Rog

                      The object I try to get is located at 12h26' +12°33'
                      So you will understand why I need native equipment.

                      • w7ay replied to this.

                        kellimtai The object I try to get is located at 12h26' +12°33'
                        So you will understand why I need native equipment.

                        Yeah, the skies near NGC4388 has few stars to use for plate solving. Lots of small, dim galaxies in that region, but they cannot be used for plate solving (they are not even in star databases).

                        As a last resort, GOTO a part of the sky nearby that has more stars and do a plate solve there, then sync your mount before doing a blind goto to your final target. With good mounts, good polar alignment, and good leveling of the mount, you should end up quite close to your target.

                        As a really, really last resort, take an image and submit to astrometry.net to plate solve after doing an initial GOTO with ASIAIR. Then apply the difference in RA and Declination that is obtained from astrometry.net to the ASIAIR for a blind GOTO.

                        Good luck,
                        Chen

                            w7ay yes it was the idea to do it that way but unfortunately the wather conditions changed fir tonight so will have to do it a other day. In case I couldn't catch it with the RC I got the option to use my newton 200/1000 and try it with that it do open twice the size of opening.

                              Have you tried the Detect Star option to find out how many stars Asiair it is detecting?

                              Maybe Chen could explain to us how many and of what magnitude are necessary to be able to make a correct platesolve (or a correct stack, too)

                                elpajare hi
                                I shared 2 pics just above to show how many stars it get if I put my gain at max and the exposition time at 10sec.
                                In average I get in that configuration 180 stars if it is at a right place with a lot of stars but due of the little window i get with the RC it shrinks to get enough stars in a combination but what's strange is, it's before I got the possibility to catch the PA without problems still using the first gen Asiair.
                                But if the VW Asiair is more capable with a more little window of course it will be my next investment. But also consider I need ZWO to investigate in a little camera like the asi174 but with integrated GPS to do my work in asteroid ocultation. It need to be very precise at the frame per integrated time.
                                Well this is of course not for the RC it's more for a fast newton. 😉
                                Actually I will test some proposition tonight the sky is a bit shitty but should be enough for testing.
                                If it runs well tomorrow I will get a good weather condition to try it again and do my work elsewhere I have to use the 200/1000 newton.

                                Thx to Chen and the other, I will replay my test later.

                                  I am more concerned with the magnitude than the number of stars. It would be interesting to know what the limiting magnitude is for Asiair to take them into account.
                                  I also have problems with platesolving and stacking.

                                  • w7ay replied to this.

                                    To better understand each other, I am using an RC 203/1824 with the ASI294MC and my preview is 5 seconds with maximum gain.

                                    elpajare I am more concerned with the magnitude than the number of stars. It would be interesting to know what the limiting magnitude is for Asiair to take them into account.

                                    Like you, I do not have source code to look at. Its a shame, because many of the outstanding bugs would be found in a few hours by cloud sleuths.

                                    However, from casual observations, the Detect Star tools and the Plate solve tools appear to use different number of stars. It makes sense because the former cannot use saturated stars to estimate the HFD (notice it leaves out saturated stars), while the latter has to admit every star to create the asterisms (check out astrometry.net's document; ASIAIR has to be using something similar).

                                    Brighter star magnitudes are important of course, due to better signal to noise ratio. But there are other factors too, sensor read noise, sensor gain vs exposure time, sky background (SQM or Bortle), filters, tracking stability,...

                                    I also suspect that it is better to have many stars with similar magnitudes, instead of a couple of very bright stars, and the rest too dim to use.

                                    I don't know how ZWO picks stars to include in the ASIAIR plate solving database. If it were me, I will not pick a fixed magnitude to include in the database, but pick stars so that the star density (or more accurately, the density of asterisms) remains moderately constant (dimmer threshold in star-poor areas of the sky). This will keep the database small, while being less finicky with camera angles and where in the sky you are plate solving, and it may give a smaller FOV on average (why include as many stars in the middle of Cygnus, for example).

                                    Chen

                                        w7ay

                                        FYI, ZWO use Astrometry to do offline plate solving. The code is open source.
                                        The command ASIAIR sends to Astrometry is this with solvetmp.fit being the image to solve (ignore the values):

                                        solve-field --timestamp --use-sextractor --overwrite --no-plots --no-verify --no-remove-lines --uniformize 0 --corr none --match none --new-fits none --rdls none --solved none --index-xyls none -H 0.21 -L 0.17 -3 96.405 -4 -52.712 -5 180 --fits-image /tmp/zwo/solvetmp.fit > /tmp/zwo/solve_output 2>&1:

                                        These are the plate solving files included in the ASIAIR Pro:

                                        What I suggest can be done is when a plate solve fails on the AAP, store the image and later upload the image to:
                                        http://nova.astrometry.net/upload
                                        to see if it can actually be solved by the online solver there.
                                        If it cant solve, then maybe the image quality is poor.
                                        If it can solve, then check which index file it used to find the match and see if it is included with the AAP. If it is then maybe a ZWO problem. If it isn't then your FOV is too small.

                                        Steve

                                        • w7ay replied to this.