symmetal

You can experiment on getting the best framerate indoors with just the camera on its own sitting next to the PC. You don't need an actual image to be seen. I use Firecapture for video imaging though Sharpcap as mentioned is just as good. Your maximum framerate possible is dependent on the exposure time. Aim for the shortest exposure time you can manage. The shorter the exposure the more likelyhood of getting a sharp image as you capture short moments of good 'seeing' For the moon you should manage 5mS or less and still get a bright image. Max framerate = 1 / (exposure time in seconds) Exposure = 100mS. Max frame rate = 1 / 0.1 = 10fps Exposure = 5mS. Max frame rate = 1 / 0.005 = 200fps However your actual max frame rate achieveable is limited by your hardware and how fast it can mange the data rate coming from the camera. You need a short good quality USB3 cable, (less than 3m) to get the maximum out of USB3. I assume your netbook has USB3 ports. If you have to use USB2 then that would limit your maximum framerate more. Having plenty of RAM and/or having an SSD drive helps with longer videos. Running out of RAM during recording and then relying on writing 'direct' to a standard hard disk drops your frame rate right down. Disabling, or limiting the update rate, of the preview screen during recording can give more processing power to the actual video capture if you have a lower spec processor. If your subject doesn't fill the frame then select a ROI (region of interest) in the capture software that just covers the target. This will reduce the amount of data needed to be sent per frame so hardware limiting is less critical. Very useful for planets where 200fps can be achieved. (The usual maximum limit of ASI 'planetary' cameras.) Having a high framerate isn't required to get a higher quality stacked image. (Still keep the frame exposure as short as possible though to hopefully 'freeze the seeing' conditions.) It just means your recording time for each video is reduced to get the necessary number of frames to stack. This means less likelyhood of the subject image changing throughout the recording (particularly for solar, and to a degree Jupiter due to its fast rotation), and/or clouds, leading to a more blurred stacked image. For the moon or solar you can double the camera framerate by doing two recordings of the top and bottom half and stiching them together. Select a ROI that covers half of the target. Only the height of the ROI affects the camera frame rate not the width so you can keep the width at maximum if you wish. For the moon you can record for 5 mins or more as long as it doesn't drift outside the ROI or clouds pass by. Alan

If you unscrew the adapters at each end of the ADC you can see two compression rings with four holes to insert a 'key' to tighten. I found one of the rings of mine wasn't pushing against the glass holder. When the glass thumbscrews were tight it still rattled when shook, which was the compression ring rattling. I just did the ring up half a turn pushing with my fingers until it felt resistance and the rattling stopped. I assume they're done up tight enough to stop the glass twisting but not enough to stop it rotating with the levers. When you have the tightness right a dab of silicone on the edge of the ring should keep it from un-doing again. This might be your problem. Alan

I just took the 5" as the diameter and didn't add on the extra bits. Therefore using the 750 ohm resistors means spacing them at 1.14cm or using the 2x330 ohm means spacing at 1.3cm. In reality you could just space the rungs at 1cm and add a few more resistor rungs to get the 48cm length. This means overall it will be around 9W with the 750 ohms and around 10W using the 2x330 ohms. Whatever method takes your fancy. Alan

That's just a full stop to separate the values. Poorly written I admit as it could be confusing. They are max 8A rated. Alan

You don't want to run the resistors near their maximum rating as they will be too hot to touch in free air and could cause localized hot spots around the scope. To dissipate 0.2W per resistor (using 0.25W resistors) rearranging Ohm's law R = V^2/W = 12* 12 / 0.2 = 720 ohms. 750 ohms is the closest preferred value which would dissipate 0.19 Watts. If you have a stock of 330 ohm resistors you want to use up, you could put 2 in series for each 'rung' of the ladder where each rung would dissipate 0.22W (that is 0.11W per resistor). If using 750 ohm resistors for each rung to dissipate 8W in total (from the above chart) you would need 8/0.19 total resistors = 42 If using 2 x 330 ohms in series for each rung, you would need 8/0.22 rungs = 36 rungs. So 72 resistors in total. A 5" scope has a circumference of around 16" which is 40cm. So the 750 ohm resistors would then be spaced 40/42 cm apart or 0.95cm apart. Using 2 x 330 ohm rungs each rung would be spaced 1.1cm apart. Alan

If your active USB extension cable is in reality a hub with a single output then no it won't work in reverse. USB requires a connection from a host to a device. With a normal 4 port hub your PC is the host and the connection on the hub it normally connects to is a device. The 4 hub outputs then become hosts to whatever device is plugged into them. When first plugged in the host initiates the communication and the device responds. With your extension cable reversed you would have a host connected to a host and a device to a device. USB3 also has separate wire pairs for transmit (TX) and receive (RX) (unlike USB2) so the hub hardware would be designed to receive on one pair and transmit on the other. If you reversed the hub you would have the PC TX connected to the hub TX and RX to RX. A TX has to connect to an RX for it to work. I assume the power required for the active extension in 5V. It would be fairly easy to connect a 12V to 5V buck converter to your 12V at the mount to give the 5V needed for the extension cable. You would need a DC connector lead to plug into the extension cable and it looks smaller than the standard 2.1mm x 5.5mm connectors. I would just chop the existing wire off your extension power supply and use that, but you may not wish to do that. A cable shorter than 15m could very easily work at a higher speed. It depends as to how the hardware in the extension cable sets what speed it wants to work at to give a reliable connection. I suspect it connects at a lower speed than what the host speed negotiation initially tries but I could be wrong in that. Halving the length of the cable could well double the speed up to say 120Mb/s but there's no way to tell for sure unless you try. Alan

Ah! That makes sense. You had me intrigued as to its purpose. Alan

Astroberry is a suite of linux programs for installing on to a Raspberry Pi single board computer located near the scope as an alternative to a Mini-PC or similar doing the same job using Windows. You need to learn a bit of the linux operating system to understand it all. Image downloading is the only thing that taxes the USB connection rate really. All the other operations are fairly insignificant as far as data bandwidth goes. Your guide camera downloading every couple of seconds or so is probably the second biggest user of bandwidth but these are small images. I'm not sure what Juicy6 uses the SSD to USB3 device for at the scope, but it plugs into the USB hub as another device just like your camera. They would all be 'before' the active/repeater cable which connects between the hub and your PC indoors. Reading and writing to this SSD device would be done over the active/repeater USB3 cable like an external USB drive connected to your PC. The read/write speed to the SSD drive would be limited to what your USB3 extension cable can deliver. In Juicy6's case that's 60MB/s to the SSD drive while also doing normal imaging stuff. Unless your doing video imaging with a USB3 camera as I mentioned above, 60MB/s or so downloading images to your PC should be OK. Alan

I expect the active extension cables force the USB3 connection to work well below the theoretical maximum speed which is why they work. My ASI cameras worked fine on 3m but were unreliable on 5m USB3 cables. The speed negotiated for working at 5m was likely too high. Juicy6's speed of 60MB/s is only 1/10 the maximum USB3 speed and is close to the top speed for USB2. Juicy6's happy with that speed so no problem. Using a gigabit ethernet link instead is a theoretical maximum transfer rate of 120MB/s , still below the USB3 theoretical maximum of 640MB/s. This is probably only really noticeable on doing solar/lunar video imaging using full sensor size or large ROI when you notice a lower frame rate. So I'd say that active extension cables will work if your system and you are happy at the reduced data rate. Alan

James has pretty much said it all but I'll add my tuppence worth. 3) USB3 spec doesn't actually specify a maximum cable length as unlike usb2 it communicates in both directions simultaneously (asynchronously) and the receiving end can tell the transmitting end to pause if it's getting overrun with data. However as the USB3 data rate is so much higher than USB2 the cable quality is the limiting factor rather than the length (due to signal timing delay) as in USB2. 'Standard' USB3 cables over 3m will generally degrade the signal quality too much to allow full USB3 speeds. USB3 will work with longer cables but at a reduced speed. The maximum workable speed is determined when the device is connected by a series of signal pulse tests. However this reduced speed may not be compatible with a device which can only transmit at a higher speed. As active USB3 extender (or repeater) cables are just a bus-powered single port usb hub and the cable quality looks no different to a standard cable I'm surprised why they are claimed to work at full USB3 speed when they are greater than 3m long. If that was the case all hubs would have the 'magic repeater' built in and would then work at full speed over 10m or even 25m without problems. You can daisy chain up to 5 hubs between the computer and the final device in the chain. Your camera hub counts as 1 and your Orico as another so theoretically 3 repeater/active cables in series could be used in your case. As each repeater consumes power from the PC this reduced power limit as you go down the cable may cause issues. A 10m active cable may work for you (at less than full USB3 speed) without problems but you have to try it to find out. 4) You would use a short male-A to male-A USB3 cable as James mentioned to join your Orico hub to the socket on the active extension cable at your tripod leg. Alan

You don't need to redo flats if the camera goes back on with the same orientation as it was before. I've only taken one set of flats and darks and the camera is off and on the scope all the time. I always have the long side of the camera image parallel to RA so its orientation is easy to repeat. Platesolving checks the camera angle, but if you don't do that, to get the camera orientation to within 0.5 degrees, swing the scope in RA until the counterweight bar is horizontal, (using a spirit level), then lock the RA clutch. Move the scope in Dec until it's horizontal, (by eye is sufficient as it's not too critical) then hold the spirit level against the base of the camera and rotate the camera until the lettering on the camera rear is parallel to the level hand held spirit level base. You'll need to bend down to see. That works for all the ZWO cameras I have. The Atik One is easier as it has flat sides to place the spirit level on. Darks don't need to be redone if the temperature is the same as that used when taking the darks. You boiler room solution sounds like it should work. It's worth getting some humidity meters, (they're very cheap on Amazon) just to check the humidity in your boiler room is low. Alan

The anti-dew doesn't stop the sensor icing up, it just stops dew possibly forming on the outside of the camera front glass due to the sensor cooling removing heat from the front glass. Your image effects are too 'in-focus' to be the front window I would think. Dew would cause loss of contrast and large diffraction effects on bright stars. My Atik One often suffers from dew on the rear of the field flattener and internal filter in damp conditions. It doesn't have a heated sensor window. I never found cooling the camera more slowly helped. If the humidity is very near the threshold of ice forming it might do. It's worth just storing the camera in a box with desiccant as I mentioned even if you don't remove the access plug on the side. Now mine has thoroughly dried out internally, I don't remove it now either. The fact that the internal tablets do get damp implies the camera chamber isn't airtight anyway so spending days in a very dry environment can only help keep the internals from absorbing moisture. Alan

My 071 suffered from bad icing when I first got it, at any set temperature below zero. I did open up the camera and replaced the desiccant tablets though I could have dried the existing ones in the oven/microwave. As I found out the desiccant tablets will release their moisture at room temperature if the surrounding humidity is lower than they are, to save opening the camera remove the access screw plug on the side of the camera under the black plastic disc. Just gently lever the disc off to reveal the screw. Then place the camera in an air tight food container with a bag of fresh desiccant crystals, like those sold for use in drawers or small cupboards. It'll take several days to work, but the internal tablets should dry out to match the humidity of the air around the large bag. I keep my 071 like this when it's not in use (pretty much forever at the moment ) and just replace the plug in the side of the camera to make it airtight (hopefully) again when you take it out to use it. Haven't had icing problems since. I keep a humidity meter in the food box and it reads about 20% all the time. Zwo used to supply a little container that screwed onto the access hole in the camera and contained two tablets. This wasn't sufficient to dry out the tablets inside and Zwo don't seem to supply it with the 071 anyway. Alan

It's an optical problem with the lens, and is showing coma in TR and BL corners. Normally it appears in all corners but it depends on how well the lens elements are aligned. At f2 it's not too bad really. Some Samyangs are better than others and it's luck whether you get a good one. At least it is on the wide angle lenses. Stopping down the lens should improve the coma effect but that means longer exposure or higher gain. Spacing isn't critical as long as you can actually go through focus but it's preferable if the lens is indicating near infinity when the stars are in focus as then you get the full focus/distance range if needed. Alan

Hi Alan, This image isn't as good as those you posted since you used the focus lock. The spacing is wrong as you say so there is noticeable 'coma like' smearing towards the edges particularly on the left, different for each colour, and misshapen stars, again different between red and blue on the right. Green is the best focus overall and the red has 'halos' all over, not out of focus as such, as the star shows brighter in the middle of the halo. I assumed the bayer pattern was the same as the 071. I just lifted the blacks to avoid too much star clipping. I think the spacing error is the root cause of these effects so it's hard to be sure about other causes. View the image below at full size. Alan

The temperature probes in my Lakeside focusers are a DS1820 1-Wire sensor. It has 9 bit temperature resolution. This device is now discontinued, so getting one can be problematic. A drop in replacement is the DS18S20 which is a 'doctored' version of the now common DS18B20. The DS18B20 has programmable 9 to 12 bit resolution and defaults at 12 bits. The DS18S20 is effectively a DS18B20 fixed at 9 bit resolution. DS18B20 Datasheet DS18S20 Datasheet Application notes describing the differences between the devices. If you search online for a DS1820 datasheet you get directed to the DS18S20 datasheet. Externally they function identically, though internally they are different. I can upload an actual DS1820 datasheet if you wish. I made an Arduino based dual focuser for 2 Lakeside focusers and can switch between using 9 bit data if connected to the Lakeside DS1820 temperature probe, or 12 bit data if connected to a separate DS18B20. The Lakeside D9 connections are pin 6 = Gnd, pin 7 = data, pin 8 = +5V. All three devices mentioned here have the same pinout. The latest Lakeside focus units may well have DS18S20 temp probes installed. I bought mine several years ago, which used DS1820 devices. Hope that helps. Alan

Hi MalVeauX. Didn't realise you'd posted an extra tutorial until today. I like your opaque bag method for getting flats when the Sun doesn't fill the frame. I get the full disc with my ASI178 and Lunt 50 so hadn't taken flats up to now. I'll give your method a try. I agree with your method about not using gamma when recording, just while focusing etc. I use Firecapture too. An extra bonus of not using gamma is a significant increase in frame rate especially when recording full frame as it takes a fair amount of real time processing to apply gamma to every pixel. I was wondering one time why my frame rate was so low when recording until I realised I'd had left gamma on after focusing. Turning gamma off (or just leaving it at 50) made the frame rate much higher again. I've found recording video in 16 bit makes no difference to recording in 8 bit. I was wondering why, and found this article by Craig Stark The effect of stacking on bit depth. As long as there is noise in each frame, stacking not only reduces noise but increases bit depth. He concludes CMOS cameras used for planetary/solar imaging are generally 12 bit. The camera output is just multiplied by 16 to give 16 bits. Stacking just 100 8-bit images which contain noise, (as astro images invariably have) will give you quantization noise equivalent to 12.1 bits. As we normally stack more than 100 frames we've already improved on the 12 bit quantization error on the 16 bit recording. Also recording in 8-bit generally doubles your frame rate if recording full frame so another bonus. Alan

Hi Alan, Your 071 Master flat is again almost totally white clipped so would have no effect on combating vignetting. I loaded yours and my 071 flat into APT (as that's what you use) to show what the histogram should look like. The APT histogram seems to only display from the min to max ADU values in the image and not the full histogram from 0 to 65535 ADU which is a bit annoying. Maybe there is a way to show the full histogram but I couldn't find it. Here are yours and my 071 flats in APT. Note your flat shows a peak but the range is 64076 to 65034. The peak is all squashed up at an average value of 65004. As it's a colour camera there should be three peaks corresponding to the response of the three colours and the actual colour of your light source. Note my flat has a range of 17358 to 47490, which is in the middle of the full range of 0 to 65535 so no clipping of data. The width of each colour hump indicates the amount of vignetting in the image. The wider the hump the more the vignetting. Here are your and my flats loaded into SGP which has a full 0 to 65535 top histogram display. Your flat doesn't really show on the top histogram as it's all effectively crammed into a single vertical line on the right. If I move the black point slider under the top histogram to the right the bottom histogram shows the values from 61503 to 65535 similar to what APT shows. My flat on the right shows the three colour humps nicely sitting in the middle of the full histogram. When taking flats you always really just want to see the full histogram and not have to analyse what the range values are and interpret the real result from them. Note that APT seems to debayer the preview image so it shows as green being brightest (the right hump of the three). SGP doesn't debayer the images so always shows the image as grey. I should ignore the APT flat helper, as it doesn't seem to help, and just vary the exposure until you get three humps similar to what mine shows. Also check the range ralues are at least 5000 ADU (ideally more if you can), from the limiting end values of 0 and 65535. If you're still too overexposed at 0.5 second exposure put some sheets of paper over the front of the lens, or in front of the light box if you're using one. Your latest single image is pretty good focus wise. Here it is debayered (rough colour balance), and just black lifted, not stretched, to avoid clipping too many stars. Just the stars on the left are slightly elongated (on all colours) showing very slight tilt or the camera not fully on axis. As the vignetting was generally on one side I would suspect the latter. However the image here shows no vignetting. The red is still slightly less focused overall compared to the green and blue but not enough to cause too much worry. The focus on all three colours does hold well into the corners though so the scope is good in that respect. Hope this all helps Alan. Alan

Hi Alan, The flat of the 071 you posted is totally over exposed and white clipped, ADU 65528 over the whole frame, so would have had no effect on correcting any vignetting from your scope. Maybe you posted the wrong file, but post the master you used just to be sure. You didn't waste my time with the old darks. I didn't analyse them properly. The newer 183 darks posted are similar to your previous dark though the newer 3min one doesn't have the halo. Actually examining the original ADU values of the highly stretched image the white 'star' like pattern coming in from the right probably is just amp glow and is in reality only just brighter than the rest of the frame. For your newest 3 min 183 dark, the average ADU on the left is 640 while the brightest part of the the 'star' pattern on the right is 704 ADU. Not much difference really. It's shape led me to think it was light leakage and I didn't go any further. I should have checked the ADU values before assuming it was light leakage. Not sure what the cause of the halo on the older darks was though it could just be slight 'amp glow' from components on the sensor which are masked by the longer dark to the point where they are not significant. Also, the newer longer dark has lower ADU values so reducing the temperature has been beneficial. It just looks more noisy because it has been stretched more. So I'd say the 183 and 071 darks are fine. Just need to see a proper 071 flat now. Older 183 2 min dark (range 800 to 1070 ADU) Latest 183 3min dark (range 640 to 704 ADU)

Ahh OK. Zero gain is fine as you have much more clear skies generally than us in the UK so can use longer subs without running out of time. Your offset won't be zero though but I'm sure it's right if you haven't changed it. Here are your darks heavily stretched. The 071 dark looks fine showing a slight sign of amp glow top and bottom. The 183 Dark is something else though. I think you had some light leakage while taking them and it should have made your 183 images exhibit a dark diffraction pattern from the centre right as well as a slight dark halo in the centre. 071 Dark 183 Dark It's worth posting the 071 flat you were using as I'd like to know what's causing the right darkening on the 071 images. Alan

Do you really mean zero gain and offset or did you mean to say unity gain (the default option I believe). The 071 unity gain is gain 90 with offset 65. Clicking on the camera Ascom driver setup icon in your capture software should let you check. You probably need to click the 'advanced' tick box in order to view the offset. If your offset actually was zero that would give black clipping. As your Borg has a 2" filter drawer that rules out the filter causing vignetting. There is a slight amp glow on the 071 on longer exposures but it's generally along the top and bottom rather than the right. The Flaming Star/Tadpoles 071 image looks like the 183 darks have been applied instead of the 071 darks if the 183 has amp glow on the right. The darks are subtracted from the lights, so a dark with amp glow will subtract more where the glow is. As they are different resolutions the stacking software shouldn't allow that though. You could recalibrate your Flaming Star 071 image without using darks and see what results. Or post your current dark and flat masters here. Alan

The 77EDII is claimed to cover full frame sensors, so the M42 rear fitting should be fine for the 071. What size Astronomik filter are you using and where is it fitted. They do an M42 version which would possibly cause vignetting if fitted significantly in front of the camera. Or do you have a 2" filter fitted in the scope which would be fine. If your flats were also showing the same darkening on the right, then when calibrating with them it should have corrected the problem. The result of excessive vignetting calibrated with same vignetting flats should still be a flat frame. The visible effect after calibration should be increasing noise seen on the right as more gain is effectively applied there to correct the light loss. That is as long as the flats or image are not clipped to black anywhere on the right side. Likewise check the darks aren't black clipped anywhere too. The default offset on the 071 is fairly high at 65, and I've checked mine and they are well clear of black clipping at that offset value. Check your value hasn't been changed inadvertently. If the focuser was tilted by not using the locking screw I would have thought the focus across the frame would be more sevely affected than the vignetting. The focus on your last post is pretty even over the whole frame and doesn't show significant tilt effects. Alan

That's actually pretty good focus wise. The red focus is actually similar to green and blue. The jpg compression does make assessment more difficult. Have you used flat frames as that would normally take care of the right side darkening. The right hand side has ended up being over processed as the bright blue stars have red halos clipped to black and the top right nebula has green clipped to black. Overall it's a good image though. What diameter extension tubes have you used? With my 071 with the WO Redcat51 or ZS61 I've used M48 extension tubes (as that's the thread on the rear of the scopes, and put the M48 to M42 adapter right next to the camera. With your fast borg scope M42 spacers several cm in front of the camera may cause more noticible vignetting. it's just a thought. Alan

Yes, vlaivs settings are good general values. If you want simple then unity gain (and a fixed offset) for everything. The gains/disadvantages of using different gain values are relatively small. I use unity gain (139) for all, offset 56, 60s for L and 180s for RG and B, along with as long as convenient for NB, normally 480s or 600s. I expose until the sky background swamps (significantly exceeds) the read noise and these are good exposures for my Bortle 3 skies. If you have higher LP then shorter exposures are more beneficial. Alan

The easiest way to check on whether you have zero value ADC outputs is to take a bias frame and load it into fits liberator or your capture software to display the histogram. You may need to apply a log stretch to show the black end more clearly. The image 'hump' in your histogram corresponding to your bias frame data should not be clipped off on the left hand side, that is the full data distribution of the hump should be above a value of zero. Dead/bad pixels may give a zero value so ignore spurious spike values well away from the bias hump. Alan