symmetal

I mentioned focusing as a small variation in focusing can affect corner star shape as well as focus. Manually focusing on the 'thirds' can give improved corner star shapes without affecting the centre to any degree. With autofocus you're dependent on what method your software uses as to whether it goes for best average focus over the frame, or weights it towards the centre. At one stage I found that after autofocusing, if I told the focuser to move out by 5 steps, the corner stars were improved without noticibly making the centre worse. This was a problem in automated runs as it wouldn't find optimum focus. Using a Gerd-Neumann tilt adjuster on the 6200 seemed to solve this problem. With a sensor that size a tilt adjuster is most likely needed. They are more expensive than standard push/pull adjusters as found on the cameras but easier to set up. Alan

It's possible your adjustments to reduce backlash have moved the worm gear closer to the wheel, and it's binding slightly at some positions. When I adjusted the backlash on my AZ-EQ6, I put an ammeter in the power supply feed and measured the current taken as it slew throughout its operating range. Although it looked and sounded fine, at one section the current taken doubled meaning more effort was required to move the mount at those sections. I backed off the backlash grub screws very slightly and the problem cleared. You end up with slightly more backlash but the mount doesn't run the risk of sticking at certain points when guiding. Alan

Hi Lee_P, All three images are pretty much the same, regarding corner star shapes, and better than your previous post so increasing the FF dist has helped. Top-left is pretty much spot on. Top-right and Bottom-left show slight radial elongation (towards the centre), while bottom-right is showing a tendancy towards tangential elongation, (rotating about the centre), although it's a bit of a mixture of the two. It's worth increasing the FF a little more, about 0.5mm say to see if the top-right and bottom-left improve, without the top left getting noticeably worse. The bottom right is in a bit of a halfway house at the moment so may improve with the increased 0.5mm or get tangentially slightly worse elongation. Worth giving it a try. The CCD Inspector plots show slight differences but small variations like this can easily happen between successive frames in an imaging run. For a more consistant analysis you generally need to take several images (6 to 8 or so) at each position and stack them. You had varying thin cloud on your images which can affect the measured results too. Did you refocus between rotations and did you manually focus or use autofocus for the images. The central hump you had on your first posted image has gone which is good as it implies your central stars are now a bit sharper. There is an indication of very slight tilt from left to right, for which you may want to try using the camera tilt adjustment (as it's not affected by camera rotation) but it's very small and you may make it worse. Before doing that though, it's best to check an image from the other side of the meridian to check that it's not just very slight focuser droop possibly causing this. You may find after stacking many images in normal imaging that the slight corner aberrations are masked out by the slight star 'spreading' due to rotations and shifts during stacking, so your setting as it currently is may be fine. 😀 I used up several rare good imaging nights trying to improve the corner stars on my ASI6200 (full frame sensor) but accepted that it wasn't going to get any better, and real stacked images were actually very good, especially when binned 2x2 😀 Alan Edit. Rechecking CCDI analysis results, the 0 deg had 650 stars analysed, while the other two only had 350 or so stars used for analysis which could explain the slight variation. The clouds probably obscured more stars on these. I would take the 0 deg image as the best one to use here as an indication.

I ran your image through CCD Inspector and it reports very little tilt, and the fall off towards the corners is fairly even, reporting the FWHM better in the corners than the centre. This implies the focus has favoured the corners more than the centre. I think just increasing the FF spacing by around 1mm or so should give you better results. You invariably find the best distance is never exactly as calculated, so a little bit of fiddling is needed. At least you probably don't need to worry about tilt. 😀 The second 3D image doesn't imply that the image centre is 'closer' than the edges, it just indicates worse centre FWHM results as a more positive Z value. The brighter the colour, the worse the result. Most results show the corners rising up in the Z plane, but yours is pretty good in that respect. CCD Inspector should be used more as a guide than an absolute analysis as it seems to rely on its determined FWHM values, and errors like coma and other star 'smearing' effects don't seem to affact the calculated results as much as they ought to. Alan

Yes the protect window is the 2mm thick glass plate on the front of the camera. The manufacturers FF spacing distance is quoted for just air between the FF and the sensor so it usually has to be increased when used with most cameras, and any filters, if used. It's quite possible there is a bit of tilt causing your corners not to be the same. The camera has a tilt adjusting plate on the front which is handy if the screws aren't blocked by filter wheels or the like. First determine as to whether your current corner stars indicate the FF spacing needs to be increased by increasing it by a significant amount as I mentioned. If they now exhibit elongations at 90 degrees to their current direction, tangential elongation as compared to your current radial elongation then you've gone through the optimum FF distance. The stars may show little 'wings' instead of just being elongated. If you can't find a distance where they are all equally good then it indicates tilt which is normally a bit of a pain to correct as you're not sure where in the imaging train the cause is. As the tilt adjustment pushes the camera further away at the adjustment point you want initially the FF spacing to show one corner good and the other corners showing stars towards the centre, assuming towards the centre means that edge of the camera is too close. Give one tilt adjustment screw a fairly large turn and make a note of the effect on a test image. Put that screw back and try another tilt screw, and then the third one so you know what effect each screw does and on what sides of the camera image they effect. Before you make any tilt adjustments it's worth taking an image with the camera rotated at 90 and then 180 degrees to the current orientation to see if the image corner stars affected stay the same or whether they change corners as the camera is rotated. If they stay the same it implies the camera sensor is tilted relative to the rotation point, and if they don't it implies the focuser is tilted off axis. A tilted sensor can be corrected with the tilt adjustment screws, while a tilted focuser will only be corrected by the tilt adjustment screws at that one camera orientation. I think that's the right way around but it's easy to get your mind in knots. 😀 A tilted focuser is most likely focuser droop under gravity so it's best to try and correct that problem at source, rather than using the tilt adjuster to correct, as a meridian flip will probably mean it droops in the other direction and your previous tilt correction adjustments will then make the result worse. Alan

Your calculations are correct but I'm not sure why you needed calipers to set the adjustable FF as you just read the scale on the FF. Have you set the correct piece to the 1.8mm mark. Here's where the adjustment is made. It's a different flattener, but the principal is the same. The one below is set to 11.8mm using the rear section, and the smaller ring in front of it is then tightened against it. You also need to add around 1/3 the thickness of any glass between the FF and the sensor to the 56.8mm to get the correct distance. Any filters and the 2mm thick protect window both need to be added on. Without any filters you need to add another 0.7mm, giving you a 57.5mm setting required. Corner stars pointing towards the centre tends to indicate the FF spacing needs to be increased but that's not always true. Try moving the FF adjustment out by a large amount, like 5mm and see what the result is. The new star shapes and type of distortion should give an indication of where your optimum distance would most likely be close to. Alan

You shouldn't plate solve at the NCP especially if your platesolving is syncing the telescope position, as a minor error in RA positioning may generate a very large RA error when syncing, as at the NCP any RA position is actually correct, and one half of the image is effectively rotated 180 degrees compared to the other half, so establishing image rotation is more a matter of opinion rather than a useable value. 🙂 Alan

It's basically a built in EQ-Direct module so you can connect it to your computer with a USB2 cable and control it using EQMod etc. It appears as a COM port on the PC when connected just as if you were using an Eq-Direct cable connected to the handset port on the mount. I believe it works at a higher baud rate than normal, 115,200 baud, so you need to set that in the COM port settings on the computer and in EQMod setup. Alan

The extension reel won't be the issue here. It's 10A rating is for the 240V mains. Your 10A 12V SMPSU at around 90% efficiency, uses around 0.8A from your extension reel. Not a problem, and being partially wound doesn't matter at such low currents. The main issue is I expect the voltage drops from your 12V PSU to the equipment via the DC Hub. I assume they are all using 2.1mm DC connectors and not very thick cable, which will cause significant voltage drops. It's the main reason that 13.8V PSUs are often used, to reduce the chance of the voltage falling below 12V at the equipment and causing issues. Your dew heater making it worse confirms this. The easiest solution is a 13.8V supply. The alternative is either to upgrade all the DC wiring/connectors which isn't easy, or possibly use a DC boost converter on your 12V supply to generate 13.8V or thereabouts. Not very elegant but it should work. Alan

That seems to be the case, though I don't know if that was the intention. Whether having the whole mask with just grooves would be just as good as the grooved and slotted one I don't know, but I imagine WO did tests and found what worked best, and decided on a slotted and grooved mask as the best all rounder I suppose. 😀 Alan

I find the WO transparent mask the easiest to use as it produces very useable sharp spikes on relatively dim stars, where a standard mask does almost nothing. The WO61 mask also works well on the Zwo 30mm mini guider scope when only the centre grooved lines are pretty much all that's in view. I tried a standard black 60mm mask which i bought before WO made the transparent ones and that did nothing on the guide scope. 😀 Alan

I should have realised you had a Mac when you mentioned Thunderbolt in your first post. 😀 The USB2 ports will be OK for normal imaging, just a slower image download time, the frame buffers in the newest ZWO cameras sorted the USB2 transfer issues. For video of course they will be limiting the frame rate quite a lot with a sizeable ROI. A thunderbolt to USB3 hub should work fine I imagine, though I have no experience of using one. Hopefully someone else who has one can confirm. Your solution otherwise looks good. 🙂 Alan

Yes, I have a mini PC and power interface mounted next to the scope so they move around with the scope and almost all the cables attached to the scope and accessories don't need to dangle down to a box attached to the mount and possibly get entangled. Just the main DC power cable and an ethernet cable goto a small interface box fixed to the mount which I connect to, along with an EQDirect cable from the scope PC to the mount. 🙂 I use Windows Remote Desktop to connect from indoors or there are several other ways to do it, like TeamViewer as you say, though some people have had the Teamviewer free connection option disabled as it was suspected it was being used for commercial purposes. 😒. I also use TightVNC for remote control of those PCs not using Win 10 Pro. The ASiair uses a Raspberry Pi running Linux so is a bit more involved controlling it from a Windows PC, but several here do that and can give you more information if you need it. Alan

The maximum data transfer rate for USB3 is much faster than can be achieved using Wi-Fi or even wired ethernet. USB3 is 5Gb/s while gigabit ethernet is 1Gb/s. These are theoretical maximum speeds and you won't normally achieve them in real life. 3m of good quality USB3 cable is generally accepted as the maximum length to allow its maximum speed. You can get active extenders, up to 15m or so, to get USB3 to work over longer distances but these greatly reduce the actual data speed, even though they claim speeds 'up to 5 Gb/s'. A member here did tests with 5m and 15m active extenders, and they both limited the speed when transferring hard disk data to the same value of 60MB/s. This is 480Mb/s, 1/10 the speed of USB3 limit and the same as the upper limit of USB2. For normal imaging, and not planetary using video, this is not too much of a problem and works fine. For planetary imaging this will be a bottleneck and limit your maximum framerate. In your case you could do normal imaging from the conservatory, and planetary imaging from the shed. 🙂 Having a small computer at the scope, like the ASIair or a mini PC, to do the imaging, connected via Wi-Fi or ethernet to your indoors computer removes these imaging data transfer constraints, as the scope computer can record at full speed and transfer the data to the indoors computer later, at a slower speed, when required. Alan

Platesolve 2 seems to prefer narrow FOVs, and often fails with DSLRs with lenses. The APT forum mentions this too. As bottletopburly says download ASTAP and the G17 star database. In SGP control panel platesolving tab select ASTAP from the drop down list. I believe it then asks you to then select where ASTAP was installed, or you may have to select settings to do that. You should find it platesolves your wide angle views much better. Alan

Yes, if it's easy to display the info in 12 bit you might as well do it that way. 🙂 As you used 0 offset above there's a direct correlation between ADU level and exposure so your optimum exposure would have been 26/65 * 600 = 240s. I agree it's awkward displaying equations on the forum in a readable format. 😐 Alan

Hi Viktiste, Your calculation is correct apart from the x4 multiplication at the end. Converting from 12 bit (1600 camera) to 16 bit (usual format for capture program info and fits files) you append 4 zero value bits to the least significant end of the 12 bit data. So a 12 bit white pixel in binary of 1111 1111 1111 becomes 1111 1111 1111 0000 in 16 bit. Every bit you append multiplies the result by 2, so appending 4 bits multiplies the result by 16. You need to replace the x4 in your equation by x16 so your optimum sky background ADU is 1262 and not 316. This should give you more useful exposure durations. In my bortle 3 sky I use 60s for L and 180s for R, B and B to achieve around a sky background of around 1262 ADU. With higher LP you may find 45s for L and around 135s for R, G and B gets you nearer to 1262 ADU. For narrow band imaging, expose for as long as is practical, as you won't achieve that sky background ADU unless you expose for a few hours. I normally use 600s for narrow band imaging with the 1600 at unity gain. You can opt to use higher camera gain for narrow band to enable shorter exposures and you need to put the new read noise figure and gain in -e/ADU in the equqtion for your new camera gain. At 2 x unity gain (camera gain 200) your sky background level works out at 1473 ADU. Hope this helps you out. 🙂 Just for info, in computing, for normal mathematical working, when changing the bit depth used to represent integer numbers, you append or remove bits from the most significant end of the number, to avoid the actual number changing in value. If this was done with astro images the image would appear very dim when viewed in 16 bit and the stars would be clipped at 1/16 of the full 16 bit histogram range. Alan

The USB3 interface includes a USB2 interface on the same connector which uses different pins, so yes the USB3 camera will work in a USB2 socket though as happy-cat says it will run only at USB2 speeds. Alan

The image does indicate that the spacing is slightly incorrect. Stars pointing towards the centre generally suggests the spacing needs to be increased, but this isn't always the case. CCD Inspector may be getting confused by the bayer matrix where the star brightness is varying between one pixel and the next due to the filters and so there isn't a steady fall off in brightness away from the star centre. Alan

The manufacturers info does say that for fast systems and/or using luminance filters, sheets of paper need to be used to reduce the brightness. This implies that the panels light output is not continuous but switches or varies at a high frequency, due to the oscillator driving the inverter, used to generate the high voltages needed to drive the panel. Similar effect to many led panels using PWM to control brightness. The panel inverter input voltage can be reduced to dim the panel to some degree but using sheets of paper is preferred. At your AV exposure setting the exposure is very short and the camera is effictively 'freezing' these brightness variations. With longer exposures these fluctuations will even out over the duration of the longer exposure and you'll get a smooth flat. Alan

I did initially order a replacement set of tablets from FLO and opened up the camera to replace, them but icing occurred again when I next tried to use the camera after a couple of weeks. It's not worth taking the trouble to open the camera to replace or dryout the tablets, and potentially let in dust. The little screw on tube with a couple of tablets which Zwo used to include with the 1600, which fitted on the access hole I mentioned above, isn't supplied with the 071, or other cameras now I believe, but the access hole is still there on the side of the camera. The little tube was not effective as the volume of desiccant it contained was not enough, which I why I assume it's not included now. Alan

I assume you've cooled the camera as that looks very much like ice forming on the sensor. Try taking flats without cooling and I expect they will be fine. My 071 had the same problem the first time I used it. The flats show it clearly, but individual subs look fairly normal. It seems the 071 sensor chamber is not as airtight as other cameras and the desiccant tablets quickly get saturated. When not in use I keep my 071 in an airtight food container with a big bag of desiccant, and remove the screw on the side of the camera (under the black plastic sticker) which allows outside air to enter the chamber. This allows the internal tablets to transfer their moisture to the large bag outside. The humidity meter in the container reads 9% all the time. I haven't had any icing problems since. I've had it in use for several nights in a row with no icing issues, but when it looks like there will be no imaging for a while I put the camera back in the food container. 🙂 Alan

Do you find that the focuser value for what it believes is optimum focus tends to move in one direction. In other words each time you focus with the same filter the focuser position result tends to be a little less than previous optimum focuser position values, and that this trend continues from previous sessions. This indicates that the focuser is sometimes not moving as far as it should. The gull shaped final step indicates that for that final step, the focuser only travelled around half as much as it was commanded, either due to too much friction or possibly, but unlikely, slipping under gravity as the stepper motor wasn't powerful enough to hold it. There is no feed back from the motor to the control software so the focuser position values are just counts of the pulses sent to the stepper. It has no idea as to whether the focuser actually moved as commanded. If the focuser didn't move as far as was thought on the last step, then when the focuser moves outwards to the supposed optimum position for the final validation step it actually ends up further out than it 'thinks' it is. The focuser thinks it is at position 3860 but is actually at the physical position corresponding to say 3880, so the validation HFR is worse than it should be, hence the poor quality value. From the graph the optimum HFR should be around 1.3 but your validation is most likely significantly higher than that. I find that my validation HFRs are very close to the optimum HFR, and often slightly better, and the quality is 99 to 100% each time, so haven't experienced re-runs. With a smaller step size you will find that the fitted curve matches the lower values better as it likes to see a shallower bottom V shape rather than a sharp one. Alan

You can get 2 core stranded cable from many sites on ebay like this up to 4.5mm. At £22 for 10m it's not too pricy. 😀 Alan

I use ASTAP with SGP now, and it's much better than PS2 when your slews have missed the target by more than half a degree or so. If PS2 finds it in its first region of search it's a similar time to ASTAP, but ASTAP seems to solve in a couple of seconds even if you're several degrees away from the target. For the same error PS2 would take several minutes at best. I had PS2 set up to abort and blind solve if it didn't solve after about 10 regions. The only time ASTAP fails to solve and reverts to blind solving is when I leave the cap on. 😁 Alan