symmetal

Using the Magic Lantern firmware you can have uncompressed video on the 6D shown on this video from about 45ses in Also according to this Magic Lantern report the 6D can use a 1920 x 720 crop mode which gives 2.85x image scale increase over standard video recording. Alan

My method is to expose until the sky background noise swamps the camera read noise, such that the sky background 16 bit ADU value is 10 x the square of the read noise. Unity gain (1 electron incoming = 1 ADU) is always a good starting gain which is gain 117 for the ASI294. However this camera uses ZWOs HSC (High Conversion Gain) mode at gain 120 and higher which claims to give the same dynamic range as using gain 0 for a much lower read noise and is only slightly above unity gain. So at gain 120, default offset which I believe is 30, you need to expose until the median 16 bit ADU value of the sky background is around 280 ADU. There is little point in exposing longer as you just end up clipping more stars for little gain in signal to noise. Start another sub when 280 ADU sky background is reached as the noise due to read noise at that point is negligible and won't significantly contribute to the overall noise. So start off with an exposure of say 2 mins on a plain star field (no large nebula areas), and see what the sky background ADU value is, either by hovering the mouse cursor over the preview image background which should give you an ADU value, or examine the image statistics and note the median value. It should be fairly close to the mean value anyway. If it's more than 280 try again with a lower exposure and if it's less try a longer exposure. As it's a OSC camera the mouse values will depend on what colour bayer pixel your over (assuming the preview is not debayered) so the image statistics median value is probably a better bet for OSC. For the same sky bortle darkness use this exposure value for all your ASI224 RGB images. It doesn't have to be exactly 280 ADU, between 270 and 290 will be fine. 🙂 That's just my suggestion, others may disagree. 😄 Alan

Yes the tilt adjuster should correct that. Depending on the cause of the tilt, (it may be more than one item in the image train causing it) you may have to keep the orientation of the camera in one position to avoid tilt re-occuring on rotating the camera. For 99% of the images I always have the image long axis parallel to RA anyway, so that isn't really a problem. Only the horsehead looks better with a 90 degree rotation. 😀 As the tilt adjuster just screws on it's a bit of luck where the adjustment screws lie with respect to the camera orientation so they most likely wouldn't be at the corners. Having three screws ensures they are always all pushing on the plate to keep it in one position. With four screws every time you adjusted one screw you would have to retighten one or two other screws to maintain the force on the plate. The lower cost push-pull screw type adjusters also generally need all the screws adjusted each time to maintain even force on the plate so are more fiddley. Yes, large cameras/filter wheels and the tilt adjuster cause extra strain on the focuser. At least my rack and pinion one is fine in that respect. 🙂 Altering the focus and being able to get good stars in the corner implies that while your quad scope is correcting the corner star aberrations well, there is some residual field curvature left. You can't cure this with tilt adjustments but you should be able to get the focus aberrations to a minimum and matched at all four corners. Auto-focus usually goes for the lowest average FWHM over the whole frame, possibly weighted towards the centre, so the corners tend to be worse off using auto-focus. I found manually focusing out by 5 to 10 steps after auto-focus will give a sharper image at the centre and possibly slightly worse corner stars. If the main subject is at the centre it can be better to do this. Alan

Hi Ken82, I ran your last posted image through CCD Inspector and it does report that the main issue is tilt as shown on the following charts: The 3D FWHM chart shows the consistant change from bottom left to top right. The aspect chart is very similar to your eccentricity plot My ASI6200 full frame camera had tilt and I found that SGPs auto-focus always focused on the top left. Manually altering the focus by 5 or 10 steps would alter the best focus point to different areas of the frame including the centre. I bought the 48mm Gert Neumann tilt unit. The 68mm one you have was a lot more expensive. They are much easier to use compared to the cheaper units with the push-pull screws. For the price they should be too. 😀 I had to get the FF spacing fairly close before the tilt adjuster had much effect. As yours is a quad you don't have that problem. You can try to work out which screw to adjust first but it's easier to give one a full turn or so, and see what affect it has. CCDI 3D plot would give me a quick assessment of the affect. Your FWHM plots can be interpreted similarly I hope, but if you want to post another image to check, I can run it through CCDI for you. 🙂 I don't know what the percentage figures for curvature, and particularly tilt actually refer to, but it doesn't really matter as the plots tell the story. 😀 FWHM Curvature Plot 3D FWHM Curvature Plot Star Aspect Chart Alan

Having had a few clearish nights recently I had another go at sorting the spacing/tilt on the ASI6200 and think I've got it as good as it's going to be. Using auto focus it always gave best FWHM results top left and the centre was always softer and getting worse across the frame, due to tilt. I gave a big turn on each of the tilt adjuster screws individually just to see the result and was surprised that they had little to no effect. I reset the tilt adjuster and took a series of images increasing the FF spacing adjustment by half a turn (about 0.3mm) until I got the minimum difference between min and max FWHM using CCD Inspector and then tried the Tilt adjuster again and this time it worked and I could get the best FWHM at the centre. The FF spacing needs to be reduced a little after this as the tilt adjuster pushes the sensor further away. Here's the final result from CCDI Here it is after a meridian flip showing a slight focuser flop but not enough to be too concerned. The FWHM difference between top and bottom is very small. Here's a single 240s L image taken after the meridian flip. Corners not perfect but I'll learn to live with it. 😄 Image scale is 1.26"/pixel. If I move the focuser out by 5 steps the centre does get sharper with little change at the edges so that would be optimum but the SGP autofocus doesn't agree. It must be averaging the whole image rather than centre weighting. This means I'm not pressured into getting my fibre optic star field project done. I bought some adhesive plastic mirror tiles to stick around the centre of the board to ensure orthoganality (if that's a word 😄) An ND filter can easily be fitted in front of the leds to dim them which should give more realistic stars I think and not be clipped at 0.01s exposure. Pity to hear you're still having problems Dave and were hoping the fibre star field might help you. I'd be happy to let you borrow it to see how it works for you, but it's a bit large and fragile to transport. 😟 The ASI6200 takes about 8s to download at 1x1 (116MB) to my Celeron based mini PC on the mount. I have to drop the driver USB speed down to 70% to guarantee getting it. At 80% it will very occasionally hang during downloading if you're also doing something else. All the other cameras work flawlessly at 100% download setting. I use the ethernet link to my main PC as the Wi-Fi is slower and transferring a block of files over Wi-Fi freezes the remote desktop. No effect if using gigabit ethernet. Alan

Are you saying that EQMod is showing the wrong coords? You will need to manually input your location into EQMod, (or use a GPS if it outputs the correct data format) and then do the same for Stellarium, so that they both then read the same. Once done they'll both remember the coords entered for the next time they're used. Alan

There's a topic on CN concerning this and it seems at the moment you have to download the ASI SDK (Software Development Kit) and move one of the dll files to the Firecapture folder to get the camera to work. Torsten has posted there (post 10) giving details. Also, the latest beta Firecapture releases now have the correct dll to work with the 462, so there shouldn't be a need to do the above if you use the beta release. Alan

These connectors don't seem to be available from any of the main component distributors, and only seem to be found on ebay, aliexpress etc. They look similar to those used in the aviation industry, hence the name, but I think plane manufacturers would use main brand components and not these ones. 😀 Alan

The connectors on Skywatcher mounts are GX12 2-pin which is what the one in your picture looks like. Measure the outside diameter of the plug fixed to the mount. It should be 12mm. GX16 are 16mm diameter and are often used on Comms equipment. I have both sizes and the GX12 fits the Skywatcher mounts. You can buy them for next to nothing for a pack of 10 from China, if you're willing to wait a couple of weeks, or pay extra for UK dispatched ones. 🙂 Alan

Win 10 has FTDI drivers built-in so installing one isn't required though it shouldn't do any harm. The EQAscom find port feature is not very reliable as identifying actual devices attached to com ports is not easy to do, if at all. If your EQAscom cable is plugged in and it isn't listed under 'Com' ports in Device Manager there may be an entry with a yellow exclamation mark under 'Unknown Devices'. If there is right click and uninstall the unknown device and then either select the menu option 'Action/Scan for Hardware changes' or just unplug and replug the EQAscom cable. The Device Manager 'Action' options don't actually appear until you've clicked in the Device Manager main window for some reason. Alan

Actually found that the accessory mounting holes seem to do the trick. They have blanking grub screws and screwing a nylon M5 screw in until it lightly touches the tube seems to do the trick. An M4 screw needed screwing in more tightly to achieve the same. Luckily a US scope didn't have UNC/UNF threads here 😀. I've ordered some M5 (and M4) 10mm knurled screws from ebay which should solve the problem, possibly with some thread lock. The right side screws are over the etched focuser scale so it's probably best just to use the M5 on the left. This will probably add some tilt but at least it should be a fixed tilt which can be adjusted out rather than a wobbly tilt which depends on where the scope's pointing. 🙂 The accessory holes are actually offset closer to 30 degrees from vertical rather than 45 degrees but it still seems to work. Alan

That's a good idea Ian. I'd need two mirrors to go either side of the central star adapter or remove the centre star. As you'll only see the objective front and not the sides of the scope (unless it's a long way off) a ring of card or similar mounted further back along the dew shield should assist in getting it spot on. I was semi-joking when I said it was money wasted as there is some correlation between the results. Real images through the atmosphere don't give sharp edges to stars while the board test images can do. On the board test a peak white pixel can sit next to a black pixel while there would be a transition over several pixels with real stars. Perhaps low pass filtering the board images (blurring) may give a better representation, though real star images are blurred before they hit the sensor. Maybe an anti-alias/low pass filter is needed in front of the scope for the board images to better imitate real stars. 🙂 Getting complicated. Or dim the board stars a lot more so that several second exposures are needed and have a heater in front the stars to atmospherically blur them. 😀 The indoor test with the wider FOV scope gave more promising (realistic) looking results so I'm not sure what's different here. I did increase the FF spacing by a quarter turn on the adjustment (0.2mm) and it was better in the corners compared to the first real star image above but then the cloud came so I had to stop. Alan

Good point. With the flat IV flattener I had before, the focuser was almost fully in so the slop was less than it is now I expect. The new WO Flat68III I now have to cover full frame, screws directly to the end of the focuser with a M92 thread so I'd need a M92 spacer which would have to be specially made I imagine. On the FLT98 the whole focuser assembly unscrews from the main scope body I believe, so looking in from the front may yield a solution. There are some accessory mounting holes on the focuser body, 45 degrees either side of the focus tension screws so nylon screws in these holes tightened against the focus tube may help. If they were offset by 90 degrees it would be ideal. 🙂 Alan

Still trying to get optimum spacing/tilt with the ASI6200 and FLT98 I noticed after a meridian flip that the apparant tilt error lessened quite significantly. There is up/down movement of the focuser barrel in the scope when lifting the camera but no left right movement. As I am imaging towards the South the scope is on its side so the two tension screws on the top of the scope above the focuser barrel are now on the side of the scope. These now stop left/right movement but there is nothing to stop up/down movement. It would be nice to have a second set of tension screws at 90 degrees to the current ones to stop slop in both directions. As scopes just seem to have the one set of screws (or screw) does anyone have any ideas on stopping movement in the up/down direction when the scope is on its side. Doing the current single set of screws up really tight reduces the up/down movement quite a bit, (when the scope's on its side), but it's then too tight to autofocus. Thin PTFE strips fixed to the barrel may help but before I order some, are there any other suggestions. 🙂 This movement was always there but with smaller sensors it didn't really cause an issue. Alan

Clear tonight at the moment so here's an image which should hopefully agree with the test image above but on inspection it doesnt really. 😬 The actual image corner stars aren't as bad as the artificial star test showed and the smearing is generally in the opposite direction. Well that was a lot of money wasted. 😁 Alan

Hi Dave. I actually did some tests last night. First time out for several weeks as it's been either rainy and/or windy. I did get some extra fibres to fill in the gaps on the board and here it is set up in the afternoon. Yes, I know the grass needs cutting. 😁 The red dust caps on the board are removed before use. I put the scope on my HEQ5 with an extra weight to balance. It's a bit overloaded but as it's not tracking it was OK. The board is 17m away and the focuser is racked out about 2/3 distance. I had recently fitted a Gerd Neumann M48 tilt adjuster as the standard tilt adjusters with the push pull screws were too much of a hassle, and the one I had introduced a lot of tilt even when fully screwed in. I hadn't tried it since fitting the new tilt adjuster so only had a measured FF spacing to start with. I found the led panels even at minimum brightness (150mA) were too bright and the stars would clip at 0.05s exposure. When used indoors I had to run at high brightness as the background was much brighter than outside. Outside, at 0.05s the background was pure black, just set by the offset value. This meant that the auto-stretch previews on SGP severely clipped the stars as they tried to raise the background. Manually adjusting the stretch in SGP wasn't much better as there was too much contrast between the stars and background. The only way to see the star shapes properly was to convert the images to tiff and load them into photoshop and use curves to greatly stretch the background without clipping the stars which was a palaver each time. Much dimmer stars are needed so that a longer exposure which gives some background level would be better. Bahtinov focusing was easily done at 0.2s exposure at current minimum led brightness. This showed one side had different focus to the other so moving one side of the panel closer by about 2cm made the focus more even though the outside stars all had a different focus point compared to the centre showing the field wasn't flat. Was this just because the centre was closer to the scope than the edges by a few millimetres. I don't think so as to get that amount of focus shift between the centre and edges needs about 3cm movement of one edge. Also, moving one side closer to even out the focusing, means I've adjusted for any tilt in the imaging train which isn't what you want really, though it could still be used to get a more correct FF spacing. An easy way to get the panel orthogonal is needed for tilt adjustments. 🤔 Here are two images showing the bahtinov focusing and a star shape exposure stretched in photoshop. The focus across the field isn't too bad, but the star shapes at the corners are quite bad. The bahtinov image also shows smearing in the corners. They are full size and you'll need to view them that way to see the detail. This is the full frame ASI6200 on the FLT98. It's possibly clear for a bit tonight so I may be able to put it on my AZEQ6 on a pillar, to get an actual star image to compare. Until I do that I can't say whether the artificial field is realistic. Bahtinov focus test: Star shape test Alan

Here's the colour response of the 224MC. The Ha filter will pass a narrow wavelength band centred around 656nm so as mentioned above the red pixels will give a reasonable output but the the green and blue pixels will give much less. Putting an IR/UV cut filter in front isn't necessary, as the Ha filter has a much narrower width pass band so will cut IR and UV anyway, as well as the blue and green wavelengths. IR/UV cut filters normally pass wavelengths between 400 and 700nm. Alan

3: 'Perfect' Diode for polarity protection and/or connecting supplies in parallel This uses the LM74610-Q1 IC to make a N-Channel mosfet behave as a diode without the forward voltage drop. The IC has no Gnd reference so the module appears as a two terminal device labelled as anode and cathode. This also enables it to be used to OR power supply outputs together such as a back-up power supply. It's a small surface mount IC only and only needs the IC, a N-channel mosfet and a capacitor to function. I used the same mosfet as before and the heat sink isn't required at currents less than around 15A. I used 2 pole connectors as they are mechanically stronger than a single pole if just soldered in. I put the 'perfect' in commas as it's perfect for 98% of the time and is a standard diode for the other 2%. The capacitor determines the duration of this cycle. Using 2.2uF it's perfect for about 2 secs then a standard diode for the next 40mS. It then repeats this cycle. This means the output voltage has 40ms 0.6V or so dips, around every 2 secs. For most uses this is not a problem. It's the momentary 0.6V standard dip across the IC which powers it for the next 2 seconds. It generates around 6V to the gate to turn the mosfet on. When this voltage drops to around 5V it turns the mosfet off and repeats the cycle. Mosfets have a body diode in their design shown as the diode in the symbol and this body diode is the diode which supplies the load during the 40mS periods. As it's used for such short periods in total this body diode can cope with high currents without overheating. Here's an application using 2 of these modules to have a back up 12V battery alongside a 13.8V supply. With a charge resistor across the battery 'diode' module, the 13.8V PSU will act as a float charger and charge the battery up to 13.8V and no more so the battery can't be overcharged. If schottky diodes are used instead the battery can only charge up to around 13.4V so can't be fully charged this way. Using a 20 ohm resistor a discharged battery at 11V will start charging at only 140mA and reduce to zero once it reaches 13.8V. A 20 ohm resistor only dissipates a maximum of 0.4W so a small 2W resistor will be fine, and it can be connected across the spare anode/cathode terminals of the battery 'diode'. Don't use a totally dead lead acid battery as the resistor will dissipate 9.5W. 🙂 Here's a dual module I used using the above circuit but 2 single modules are just as good. Alan

2: Reverse polarity protection using P-Channel Mosfet This is the simplest method which avoids the the voltage drop, and associated heat dissipation requirement of using a diode particularly at higher currents. P-Channel mosfets are generally not as efficient as N-Channel mosfets and the range of P-Channel devices are more limited. Recent developments for the automotive industry have created low on-resistance P-Channel ones so here's an example. The heat sink isn't really needed at currents below 15A or so but I have a box full of them to use up. 😁 The circuit's very simple. IPP120P04P4L-03 data sheet. P-channel devices seem to be less tolerant of higher gate-source voltages than N-channel devices so the zener diode protects the mosfet, especially when the supply is reversed. Maximum drain-source voltage 40V, max gate-source voltage limits +5 and -16V, on resistance 0.0031 ohms, max current 120A (with suitable cooling 😉). The resistance I measured on my module includes the track and connector resistances. As before, the mosfet when turned on acts as a resistor so the voltage drop depends on the current. Alan

I chose the mosfet from looking through the Farnell online catalogue for one with a low on resistance in a TO-220 package which are easy to work with and went for the PSMN2R5-60PL as it has only 0.002 ohm on resistance and 60V breakdown voltage. Its transfer characteristic shows it's fully turned on at 3.3V gate-source. I'm amazed by the current ratings of these mosfets, max drain current of 150A with a momentary peak of 1002A. 😬 The drain current flows through the source pin and I wouldn't like to put 150A through the small pins. Soldering 150A wires to them would be a bit of a challange. 😁 I used the metal tab as the drain connection and used a stainless steel M3 nut and bolt for it. On checking it said that stainless steel needs a strong acid flux to solder but I used standard tin/lead solder with rosin flux and the nut soldered fine. Here's the Kicad board layout Alan

I've made several modules to help protect circuits from power supply problems, to see how well they perform. They all use mosfets with a very low 'on' resistance, to minimize their impact on being used. 1: Over voltage, under voltage and reverse polarity protection This uses the LTC4365 IC which is only available in a small surface mount package. I first used surface mount resistors and mosfets which made a small module but found the mosfets got a bit warm over 5A as they tend to need thermal vias through the board for power dissipation which is tricky for home made boards. As size isn't a big consideration I used standard components where possible. I used 2 resistors in series for each voltage threshold to enable a more accurate voltage to be set. With the values shown if the power supply drops below 10.5V or over 15.0V the Mosfets will turn off isolating the power supply. The circuit will withstand a power supply going from -40V to +60V and only pass the voltage if it's between the threshold values. There's around 1V hysteresis after shutting down so an overvoltage trip at 15V won't reset until the input volts drops to around 14V. This avoids it rapidly switching on and off, if the volts hovers around 15V. If polarity protection isn't required then only mosfet Q1 is needed, and Q2 can be replaced with a shorting wire link. My test load is a 1.5R 100W resistor fixed to a thick aluminium plate which is why 8.8A is the test current (from a 13.8V supply). I soldered wires on the current carrying tracks to reduce their resistance but they aren't really necessary below 8A, just a thick layer of solder would do. The mosfets just act as a low value resistor so the voltage drop depends on the current. Without the wires the total resistance was 0.015R compared to 0.010 with them. The heat sinks on the mosfets aren't necessary up to 15A or so but added them as I had them. As it is at 8.8A everything stays cold as the whole module only dissipates 0.8 watts. The tiny LTC4365 is on the back of the board and I thought I'd have trouble hand soldering it but I've made around six modules using ICs this size and they've all worked. 😀 🙂 I'll add the other modules I've made at a later time. 😀 Alan

Thanks David. It is for imaging over several sessions, but as the image centre coords are saved as part of the target sequence, selecting slew and then centre will automatically point the scope correctly so there should be no need to check the framing is correct. I think it's best if, as previously suggested, I run the sequence with slew and centre enabled and then pause the sequence, and turn off slew and centre to stop it repeating if I need to stop/start the sequence later. I am just used to using SGP and hoped NINA could behave the same. 😀 I used to use auto-focus with filter offsets to save refocussing as you say, but found the offsets weren't consistant from one session to the next and some filters would not be at best focus, so I always auto-focus on a filter change now. Thanks scrufy. Yes, that's what I found. You can manually centre and auto focus in the imaging tab but not slew. There are all the work arounds suggested but they require sevel clicks and screen switches. 😬 Thanks Viktiste, Yes that'll work, but requires another click/switch/selection on top of the other requirements. 😉 I'm currently sticking with SGP at the moment as I don't have to think about what I'm doing. 😁 Alan

Oh! I agree vlaiv that the more captured frames is better. If Tippon's camera can't do video centre cut-out then the 720p at 120fps will give a very small image of the planets, and Jupiter's rotation effect likely won't be resolved even with a long video. 2 mins at 4k vs 30s at 720p would give the same 900 frames to start off with for stacking, and the 4k will give a much higher resolution image, and the rotation effect, if visible, will be small. My advice was to go for resolution if centre cut-out wasn't available and fps if it was, particularly for planets. For the Moon you may as well go for resolution as video duration is not such an issue, though depending on the accuracy of Tippon's motor drive the target may drift off frame on a long video. Alan

It also depends as to whether you camera just downscales the full sensor resolution to the specified video format, or it enables you to use centre crop video instead where the video format just uses the specified resolution cropped from the centre pixels of the sensor, ie no downscaling so no loss of resolution. Canon DSLRs can use the MagicLantern firmware to enable centre crop video, and also uncompressed video, if it doesn't have it normally. If you can't use centre crop video then 4k will give the highest image resolution. A 5000 x 4000 sensor for example downscaled to 720 means a 5 x 5 pixel area of the sensor ends up as 1 pixel on the video. For planets in particular you need the highest resolution you can use. If you can use centre crop video then use a resolution that best matches the target. Probably 720 for planets, and 1080 or 4k for the moon. 4k using more sensor may show some coma effects so 1080 for the moon may be preferable. A higher frame rate just lets you capture your 1000 to 2000 frames or so quicker, it doesn't give you a better image. 🙂 Alan

The dim frames you mentioned may have been screenshots from Windows 7, where you had much greater control over window item colours with the 'Window Color & Appearance' dialog box. Windows 8 and later removed that option and you have the default white/light grey with only the title bar and pixel wide border colour selectable by 'Settings/Personalisation/Colours'. In order tochange the other windows item colours, it seems you have to edit the registry to do it, as shown here. Alan