symmetal

An interesting development with different cameras. 🤔 ASI071MC. The pixel dots are much closer together and only one bright spot is visible at the assumed centre of rotation. It was slightly out so adjusted with the built in tilt plate very easily. ASI1600MM with filter wheel, M42 to M48 adapter and M48 tilt adjuster. Wide spaced pixels like on the 6200MM but this time many more dots to choose from. I counted 6 around the centre, though some were very faint and while the camera was rotated they changed from all being roughly coincident to being spaced apart when rotated 180 degrees. Here it is before adjustment showing the large tilt error again. I chose the brightest spot which wasn't coincident with the pixel grid but this may not be correct and will have to do a star test to confirm. When adjusted to centre this spot the other spots still went from roughly coincident to widely separated as before. This spot was the same brightness as the pixels this time. The Baader L filter in the filter wheel may have been adding some visible reflections this time as each pixel dot had several faint spots associated with it. Maybe the Beyer matrix somehow made the OSC camera pixels appear close together for some reason. 🤔 I'll try my ASI178MM and ASI178MC cameras to see if they exhibit the same phenomena. Edit: I redid the 1600MM choosing the bright spot closest to the centre pixel spot as the one to centre on as the further bright spot is probably the front window. As they change spacing depending on rotation could imply that the front window is tilted wrt the sensor. Edit again: The 178MM and 178MC produced the same wide grid spacing though there is also a faint dot between the bright pixel dots so the Beyer matrix doesn't affect it. Alan

Thanks gorann. I've always put black tape around the outside rim of my tilt adjusters to avoid that possibility. Taking flats or darks during the day in particular would be risky having a visible gap on show. I'm surprised the filter in the path didn't seem to give a visible reflection. Maybe they are really good coatings. 😀 I think it's beneficial putting as much of the imaging train as possible on the jig to also eliminate any potential tilt errors from all the adapters and couplings. If you swap cameras a lot it's worth checking each camera on its own and then through the imaging train once on the jig just to check the train is good. Alan

Made my version of the jig and it's a great success. 😊 Cut up an odd piece of 18mm ply for the box and 3D printed a camera holder to fit a 2" nosepiece, or if you're lucky a 2" diameter 48mm extension spacer as the one on my FLT98/ASI6200MM was exactly 2" outside diameter. Also made a 3D holder for the laser pen angled at 10 degrees. I tried one at 13 degrees but it was more critical in laser placement and the 10 degree one worked fine. A clothes peg makes a handy on/off lock. 😀 Here it is with the 6200, filter wheel, tilt adjuster and a 16.5mm long 48mm spacer fitting nicely in the 3D printed adapter. The filter wheel unbalancing it had no effect on laser pointing. 🙂 The 3D adapter centre hole is 51.00mm across. I did make one with 50.90mm diameter but it was rather too stiff to turn. Here's two initial images with the camera rotated around 180 degrees between them. As you can see it was way off. There were 3 laser dots near the centre. One appears to be aligned with the pixel grid, the opposite one was much brighter, with a faint dot between them. I assumed the brightest one was the sensor cover but it didn't matter in reality as when the tilt was adjusted to optimum, all three dots stayed in the same place while the camera was rotated. I needed to put a lot of tilt adjustment with a gap on one side around 0.5mm 😲 as can be seen on the picture. The filter being in the path didn't seem to affect it and reflections from it weren't visible. It was clear this evening so went for a test image and have never had the left side stars so good. The far right hand side shows rather bad coma 🙁 but the star centres are sharp. Not bad for a full frame sensor. The coma was there before adjustment, but didn't appear so bad as the stars were more out of focus. The CCDI images look good and corners pretty similar with zero tilt reported, (first time ever). CCDI seems to ignore coma and just use the star centre for the test. Here's the corner crops of the test image. If not for the coma I'd be very happy but I don't have to keep fiddling with the tilt anymore as I know it's optimum. 😀 I tried another image rotated 90 degrees and it was very similar. I'll have to live with the coma but it's only on the far right, and binned 2x2 it won't look so bad. Wonder if Es Reid can align the scope to improve it, as I did buy the FLT98 from FLO. 😁 Alan

Since getting the 6200 I haven't really felt the need for mosaics which was the main reason for getting it. 😊 Astro Pixel Processor is highly regarded for its mosaic capabilities though I haven't used it for mosaics myself, just for stacking. I imagine it balances the mosaic panels to match, though someone who has used it can confirm. Alan

Great composition. My 6200 with the FLT98 has coma effects on 2 corners but I don't feel so bad about it now if a Takahashi has similar. 😊 With mine it's considerably worse on OIII compared to other filters. Blue is much better which seems strange, unless the triplet correction happens to be worse near a particular wavelength coinciding with OIII. As an observation, I would say the black point is set a bit high on the bottom right quadrant compared to the others which has also reduced the saturation on that panel. 🙂 It has a good 3D feel to the picture with the Crescent appearing in the foreground with the 'waves' coming towards you. 😀 Alan

Hi Paul, Here's my efforts with Startools. I did a 3x3 and 4x4 bin version to compare. Startools 'Wipe' module did a pretty good job with the vignetting, better on the 4x4 bin version. I managed to reveal the blue centre of the galaxy and some of the stars show some colour too. 😊 Side by side the galaxy colour is a bit green on the 3x3 version. 🙂 Binned 4x4 Binned 3 x 3 Alan

Much better on the noise front. If you want to post your stacked image, I could see what Startools can do to get some colour. 🙂 Alan

Good to know it's real from the galaxy, and that Startools or Photoshop wasn't taking liberties. 😊 Alan

Here's a crop of my M31 image showing M110 which may help. It's 60 mins each of RG and B and 90 mins of L under Bortle 3 skies. I don't know if the blue centre is actually from the galaxy itself or the star which happens to be in line with it. Your image has captured the two darker regions around the centre well. Alan

Well done for focusing on an overlooked object, normally relegated to being Andromeda's bland side-kick. 😊 I think you would benefit from some dithering to reduce the colour noise in the background. My image of M31 I recently completed showed a hint of blue at the centre of M110. Your image colour balance is a bit too yellow though to possibly show it. Alan

Very good. 🙂 I think you would benefit from doing some star halo removal using this tip for photoshop if you have it. It helped with my version having blue halos. The green halos are a bit jarring and the blue halos show most in the last image joining the stars together making it look like strings of star filaments. 😉 Alan

Managed to finish off collecting data the past few days. ASI6200MM and FLT98. 4 hrs for Ha and 2.5 hrs each for SII and OIII. Stacked in Astro Pixel Processor, processed in Startools, where it was binned 50%, and final tweaks in PS. The blue halos from the OIII filter were dominant again, 🙁 but found the PS Camera Raw filter/Optics/Defringe module does a great job of neutralizing them and even lets some of the underlying colour then show through. I followed this guide which is very quick to use. For very bright stars a second or third run of the Defringe helps using the eyedropper on the residual fringe to select the starting colour and then tweak the sliders to taste. I mask just the offending star for multiple defringes though I don't think it's necessary to mask it, as it doesn't seem to affect the rest of the image once their fringes are gone. 🙂 It's rotated 180 deg as i think it looks better that way. I could have got the vertical framing a bit better as I've cut off some of the bottom, (or really top). Click for full size. Thanks for looking. 😊 Alan

The brightest reflection which is close to the plane occupied by the pixels is the sensor cover plate which seems to be the one to use. The filter will be so far in front its reflections will be way off to one side I would hope. 🤔 That would certainly help but means removing the front plate of the filter wheel. Currently there is no sign of dust on the filter flats so I would prefer not to risk getting some. 😊 Alan

I'd like to try this on my ASI6200 but the camera is fixed to the filter wheel with 4 screws and to remove the camera means removing the filter wheel front cover and one of the 2" filters. Currently I have a Gerd-Neumann M48 tilt adjuster fitted before the filter wheel which I've adjusted looking at images but I think it could be better than it is. It may be that the FLT98 alignment is slightly out in covering full frame but it would be nice to know if this is the case. Can anyone see why the Olly's method wouldn't work if I kept the filter wheel and tilt adjuster attached while making the test. There will be two extra reflections from the filter surfaces and the laser may have to be a bit more on axis in order to reach the sensor. Also the filter wheel will make it lop-sided so will have to ensure the tilt adjuster front surface is kept in flat contact with the testing surface while rotating it. I could attach a counterbalance weight to correct the filter wheel inbalance for the test I suppose. 😀 Alan

Stacking in APP does take ages with lots of large files. I like to assume that at least it's doing a good job. 😀 I only use it for stacking at the moment and now run APP and Startools on my gaming PC with an i9 processor, 32GB ram and RTX2070 graphics card. Stacking around 300 images from my ASI6200 with 116MB image files can still take around 2 hours. On my usual i7 PC it would likely take around 5 to 6 hours. I used to use Astroart for stacking, which is much quicker, but found I would sometimes get strange background banding artifacts when using Develop in Startools. With APP stacking I don't, so use that now and put up with the wait. 🙂 Very impressive looking mosaic by the way. Alan

The power pinout diagram for the AZ-EQ6 is the same as your EQ8 diagram and I can confirm for the AZ-EQ6 that pin 1 is Ground. The drawn images are looking at the connectors from the front as if you're looking at the mount from the outside. It's convention to wire pin 1 to ground on multipole connectors, but not a rule. The quickest way to check is with your multimeter on continuity check and power to the mount removed, check for a short on one of the two mount power pins to the mount metalwork, (one of the screws holding the power panel in place is ideal). The pin that's shorted to the metalwork is Ground. Alan

You're right Olly that a camera on any mount can create a mosaic by pointing the camera at the celestial coords corresponding to the centre of each panel of the mosaic. My argument is only concerning the resultant orientation of the camera for each panel. Here's a Photoshop drawing showing the extreme option of a 4 panel mosaic centred on the Celestial Pole using 3 different mounts which illustrates the point. 😉 The camera isn't touched between panels. For high declination mosaics EQ mounts present extra challenges, although of course don't suffer from field rotation like the other two will. 🙂 Imaging software which generate mosaic panel coords, (at least the ones I've looked at) don't consider this feature of EQ mounts and assume mosaics are constructed as if it's just a camera on a tripod. Alan

No it's not field rotation as one image doesn't rotate during capture. The cartography problem of fitting a sphere to a flat surface is the same no matter which point on the sphere is chosen to be the centre of your flat surface. With an EQ mount , at Dec zero there is no mosaic panel image rotation if RA is changed. The effect is a consequence of the mount design rather than a surface mapping problem. 😉 Alan

Yes, It doesn't seem to be mentioned when dealing with mosaics for some reason but becomes clear when you think about it. 😀 If you keep a constant declination and move the scope in RA it follows that line of declination. As shown in the star chart below lines of RA are always at right-angles to lines of Declination, so to maintain that condition the camera has to rotate its orienation too, being locked to RA. You could always rotate the camera orientation for each mosaic image but it's too much trouble to work out how much. 🤔 Alan

A point to note is that with an EQ mount there will be image rotation between mosaic frames that differ in RA, so you need to ensure any overlap covers this. The rotation amount depends on the Declination of the target. At Dec 0 there is no rotation and it increases with an increase in Dec being very significant nearer the pole. Here's the effect at around Declination 60 Alan

It's dificult to say but I've tended to find star shapes that aren't just elongated pointing towards the centre, would indicate the spacing is too great. There may be tilt as well as the top stars show a different orientation to the bottom ones. I would make a fairly large FF adjustment at first of around 3mm or so to get an idea of what shape stars are when it's definately too far or too near and go from there. Alan

Just to add some extra friction. I got the tip from another forum topic many years ago, not sure which one. 🙂 Alan

I agree that on their own they do very little in adding friction. I put some leather washers between the bolt washer and the mount face which do add some significant extra friction. I got them from ebay for very little for a pack of 10 so have 8 left over. They are a bit oversize in overall diameter but were what came needing a 12mm centre hole. They've been on there for about 5 years so far and as it's permanently on a pier they don't get turned much, as the spider testifies. 😁 Alan

I would leave it at the spacing that gives the best star shapes even if it's way outside specification. It looks as if the flattener isn't that compatible with your scope for some reason, but by a strange quirk it works as it's supposed to at a much reduced distance, when covering your sensor size. 🙂 Yes, threading all the pieces together is the best option to help minimize any tilt issues, as long as there's still a way to rotate the camera orientation as required. Alan

I mentioned above that high speed uses a lower bit resolution depth so is quicker to convert each pixel. Your camera is 12 bit as specified so high speed would probably be 10 bit. As you record at 8 bits, sampling at 10 bit has no effect on image quality. As you're stacking many 'noisy' frames you will recover up to 4 bits more sampling resolution anyway so your final stacked image will have effectively 12 bit resolution. Your camera spec didn't specify dual sampling rates so wasn't sure if it had a high speed mode but it seems to. 🙂 USB Traffic is setting the speed at which the capture program will send the data over USB. If set too high a bottleneck in the imaging recording process somewhere may cause data to be lost so the capture program can throttle the data speed with the USB Traffic setting. Setting it to 100% or 1 in your instance means no throttling. If your capture program doesn't flag any errors you should be OK at 1. Again I wasn't sure if it had any effect over USB2 but it seems to. 🙂 A shorter cable was a last resort so probably won't affect things if your speed has increased a lot without problems. Not sending the camera data via a USB hub should still benefit you though as far as speed is concerned. Alan