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symmetal

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symmetal last won the day on December 21 2019

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About symmetal

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  1. Great image. Nicely framed with the clouds. Alan
  2. I assume you're referring to using a field flattener or coma corrector, and the optimum correct distance between it and the image plane. You set the back distance to get round stars at the corners of the image and this should hopefully be the same distance to get best overall focus as well. You can get good focus near the centre of the image at any spacing distance, but as you move further from the image centre the spacing distance becomes more critical which is why the corners of the image show the spacing errors the most and are used after making small distance corrections to see if they look any better. Field flatteners give elongated stars at the image corners at incorrect spacing while coma correctors will still show some coma when incorrectly spaced. I've never used a coma corrector so assume that's what you'll see. If you have tilt in the imaging train then you'll find not all corners show the same star shape errors. One corner may look good while another has misshapen stars. Altering the distance will improve the misshapen stars corner, but the previously 'good' corner may then start showing errors. Alan
  3. Varying offset values for different gain settings is more trouble than it's worth. Just use one offset value that avoids black clipping at any of the gain values you may use. The gain in dynamic range by using a smaller offset value is negligible. Alan
  4. By USB Speed do you mean using USB2 vs USB3 or the USB Speed setting in the driver. The latest cameras use memory in the camera to read out and store the images quickly before transferring them to your PC via USB. Earlier cameras without this memory had issues with excessive amp glow using USB2, mainly with short exposure imaging. So now USB2 just means it takes longer to download the image and doesn't affect the quality. The USB speed setting in the driver is to avoid sending the data too fast that the PC can't cope. If set too high you may get dropped frames or no image at all. As many CMOS camera have 'amp-glow', (the later more expensive ones don't) bias frames are not very useful as you need to use darks to calibrate your lights and flats. The darks already contain the bias signal so using darks takes care of bias and amp-glow. The position of the peaks in the histogram don't need to match the lights. The light peaks will always be higher than the darks as extra light is entering the camera causing the peak to move to the right with increasing exposure. The offset needs to be the same setting for all your images, lights, darks, flats, and bias (if used). The offset value used is to avoid getting any image values at zero which means clipped data. If different offset values are used then you can't calibrate the data correctly. Alan
  5. Thanks David. I didn't notice the little platesolve and autofocus icons at the top right of the imaging tab. That certainly helps. Having a separate 'slew to target' button would be a convenient option for me to save having to go by CdC. The 'Framing' tab has a slew option but the coords need filling in beforehand as they are not necessarily related to the current target. Alan
  6. I've been looking at NINA for my Dual ZS-61 rig as it has synchronized dither while SGP still doesn't. It looks impressive, with comprehensive features but I can't see how you slew and centre on a target, or run auto-focus, without them being part of a sequence. Using SGP I normally load a sequence and then select slew, centre and auto-focus, before running the sequence. I tend to stick to one target for a session and if I stop and start the sequence for any reason I don't want it re-centreing or focusing each time. In NINA I can run a sequence with those options enabled and then stop the sequence, disable them and then restart the sequence, but it would be nice if I didn't have to do that each time. Alan
  7. Thanks for the replies and confirmation. I'll have a go at soldering it on today. Alan
  8. Making my first surface mount PCB and the TSOT23-8 IC has these markings only. There are no beveled edges or cut-outs/indents to indicate pin 1 and the manufacturer states a dot is used. As you can see it's tiny , with 0.65mm pin spacing and I can only assume the arrow indicates pin 1. Web searches haven't helped, so before I attempt to hand solder it on the board it would be nice to know for sure. If anyone can confirm it's pin 1 it would be helpful. It's a LTC4365, overvoltage, undervoltage and reverse supply protection controller and thought it's worth checking it out as protection for an imaging setup against faulty supplies which could be costly. It's only available in this package size. Alan
  9. Clutching at straws, but try unplugging your Lynx Astro cable from the PC and in Device Manager select 'View/Show Hidden Devices' and expand the Ports section. There will probably be some greyed out entries corresponding to allocations from previous devices that were plugged in, including the Lynx Astro Cable. Right mouse select the greyed out entries one by one and select 'Uninstall Device' and they should disappear. Then plug the Lynx Astro cable back in. It should re-install itself and still be allocated to COM3. When devices are unplugged the COM ports they used should be cleanly de-allocated, but that isn't always the case which is a reason the number of 'hidden devices' can grow and you get 'COM port in use or unavailable' messages even when they should be free. Perhaps a previous device on COM3 didn't clean itself up properly. Alan
  10. I've not tried it but according to this CN topic it looks like you can. Alan
  11. With the Star Adventurer getting good polar alignment is important. If you have to polar align before mounting the scope and camera you can easily knock it off alignment while you're fitting the scope and camera. A big benefit of having a guidescope is being able to use Sharpcap's polar alignment tool with the Star Adventurer, which makes PA very easy, and can be done once everything is fitted to the mount. If your PA is good then Dec drift is not such a problem, though there will still be periodic error in the mount which could cause an issue using the 250mm Redcat with longer exposures. Guiding would also remove this periodic error problem. I use a Zwo Mini Finder with ASI120 on my dual ZS-61 scopes on an HEQ5 and it works perfectly with Sharpcap's PA tool. It will mount on the Redcat's finder shoe bracket easily. A further benefit of a guidescope is you can manually dither if you wish by looking at the PHD2 image and see how far the star actually moves for each dither, rather than guessing how much to move the mount Dec and RA controls. Can you not run 2 instances of PHD2 on the laptop to control both mounts? Alan
  12. Hi Graham, Happy to help. If you select the B.Cu layer before taking your screen shot it'll show the green tracks on top of the red. Alan PS. It's Gerber
  13. Rather than using a brute force approach to disable the power supply I would personably go for a more subtle approach of a separate unit on the PSU output which just cuts its output if the input voltage range exceeds preset limits. Something based on the LTC4365 or similar. With suitable mosfets the output current can then be higher than the 3A circuit shown in the examples. There are also modules available which use a relay to disable the output like this or perhaps this which may be worth looking into. Switch mode PSUs normally have over-voltage protection built in. The Mean Well ones certainly do. Alan
  14. The OPs power supplies are linear supplies using large transformers. The transformer has to supply sufficient voltage such that at maximum current draw the minimum voltage on the unregulated dc reservoir capacitors doesn't fall below the regulated output voltage plus the dropout voltage of the regulator stage, so an off load unregulated dc of 28V is fairly typical. On a basic regulated DC supply the only thing keeping the unregulated DC from the output are the transistors mounted on the large heat sinks on rear of the power supply. These transistors, along with their control circuitry, form a series regulator whose effective resistance varies depending on the current drawn to maintain the constant output voltage. These transistors dissipate the excess power due to the difference between the unregulated voltage and the stable output voltage. If one of them goes short circuit, often due to running too hot for too long, then the scenario experienced by the OP occurs. More expensive power supplies will incorporate over-voltage protection, current limiting etc. but there's no guarantee that the protection circuitry won't fail too. I too use Meanwell SMPSUs from Farnell. The original 100W versions I bought had been bench tested at full current by the manufacturer for 100 hours prior to sale and were about £45 each. The latest ones I bought were identical but hadn't been bench tested for 100 hours, and were £20 cheaper. I've never had any issues with them. Alan
  15. If you had noiseless images, (or very low noise) then the 16 bit image would be better. As soon as you stack a few images containing a "reasonable" amount of inherent noise then the inherent noise quickly becomes the dominant factor and overwhelms the quantization error 'noise'. From Craig Stark article for his test camera which had a noise Standard Deviation of 1.87, "The quantization noise in a 10-length stack of 8-bit images is smaller than the inherent noise in a 200-length stack of 16-bit images" From his graphs, as long as the Standard Deviation of the inherent noise is greater than 0.4 the inherent noise dominates the quantization noise for a stack of at least 50 frames when comparing 8 or 16 bit images. I suppose it's worth measuring the noise of your camera of a dark frame at your usual gain and exposure, for 8 and 16 bit and see what the Standard Deviation is. That would indicate whether it's worth using 16 bit images when stacking. Alan
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