Jump to content

SkySurveyBanner.jpg.21855908fce40597655603b6c9af720d.jpg

Tom OD

Members
  • Posts

    1,620
  • Joined

  • Last visited

  • Days Won

    2

Posts posted by Tom OD

  1. On 13/08/2022 at 19:07, ollypenrice said:

    That's a very interesting problem to have, an observation which might, quite reasonably, encourage you to throw a brick in my direction! :grin:  But I say it because, having made huge numbers of mosaics with up to 35 panels, I've never had it. I've had plenty of others, but not that one, yet I see straight away what you're talking about. Just for background info, I'd have a look at Rogelio Bernal Andreo's image of a similar field just to see if you spot anything comparable.

    Did you combine the linear panels then stretch? It's nice to do so and sometimes it works, but what to do when it doesn't? This is what I would do: partially stretch all the individual panels till the background sky value is the same in all of them and the histo peak similarly located. While we might want to end up with a background brightness of 23 in Ps units, we might settle for 15 at this stage. Next, look at the star count in the dark panels and their neighbours., especially where they overlap. What happens if you pin the background in the dark panels and stretch only above that? Can you get the star count to resemble that of the neighbours in the overlap regions? If not, you'll have to re-shoot them, I think.

    Personally I like attacking these problems in Ps because I can put one panel next to its neighbour and say, 'That one needs to mesh with this one, so what do I need to do?'

    Olly

    I ve had this same issue and it’s ended in a re shoot in a few occasions. It’s worth going through each of your 30 subs and checking the background values. Maybe sone passing thin cloud in a few frames has messed up the overall stack. Certainly shooting with a moon about won’t help, but it might be a rogue frame or two. 
    I can’t remember if I found an issue when I had this problem. I can think of three times it occurred, so as I said I m afraid I reshot the panel in question. 
    Tom 

    • Like 1
    • Thanks 1
  2. On 22/07/2022 at 02:17, symmetal said:

    Glad to hear you're happy with the results Tom. Odd that you're having trouble with the flats as I just use the light panel at full brightness with no paper sheets or ND filter, and end up with around 0.01 secs for LRGB and around 0.5 secs for narrowband. They all look good, and calibrate fine. The newer cameras don't have the short exposure issues that some earlier cameras did.

    Hope you get around to contacting Atik at some time. 😉

    Alan

     

    On 22/07/2022 at 09:04, GalaxyGael said:

    Good to see Tom, and nice form factor for this size sensor. Might even be possible to use this with a RASA8, as the 2600 and 6200 ASI versions are too bulbous.

    The brightness of your light source might help to get the flat exposure times down to tenths of a second. These chips IMX 571 and 455 work very well with short exposure flats and bias (darks if you wish), rather than the longer flat darks and flats of the ASI1600 variants and some other camera.

     

    side note: On flats, I have found that sharpcap's flat option is useful sometimes in one regard. You can obtain a single master flat, or save of each frame if your stacking software requires it. But, you can get the flat in monochrome, with CFA bias signal included. That really helped with color balance issues in flats and the bias is corrected with the master bias. normal flats still work fine, but I found the monochrome flats to be stable in every situation.

    Olly put the light panel on the scope, and at its lowest brightest setting. When I started taking pics, it was giving white pixels on the lower part of the chip through a gradient to black pixels at the top of the chip.

    After adding in the paper sheets, I was able to take exp to 1.3s, and the gradient started to disappear and become uniform. The dust bunnies then wold show.

    It took a few sheets of paper to get it to the point where the LRGB were a few seconds long,which gave a good gradient across the flat. Ha flat then become about 20s With these settings, the ADU was approx 20,000 of the full well depth, which I m happy with as 55k is the stated full max.

    Tom

  3. On 14/07/2022 at 02:10, symmetal said:

    Any update on your Apx60 Tom, and any reply from Atik?

    Alan

    Hi Alan

    I just started imaging leaving the camera on power Save, and Low as the settings. Sorry I still have to mail Atik, I got very side tracked, and started on a new mosaic.

    I m not sure how to write a review of the camera, but I can say that the FITs are very clean. My old 11 meg had a lot of pixels, and bad columns, so each file of the camera is a joy from that point of view.

    I have been taking 2hrs worth of Lum frames, where normally I would have taken 4hrs of Lum for each Lum pane. In my new 2hr frames the data is clean (so far without flats) and the data of the dim background dust is very evident.

    I have not taken Ha or RGB frames yet, I ve been just running it for the Lum frames.

    In short I m very impressed with the camera. The system still has tilt, so I cant give a proper account just yet, but in a mosaic the end downsized frames will not show the tilt issues, especially after the overlaps are blended.

    The chip is o sensitive that taking flats is tricky. The Ha flat at 6 secs show s agoo even light frame. The lower 0.1s flats for the other filters, are giving bright to dark gradients across the chip that are unusable.

    So you need a dim flat field box I think to get flats with this chip.

    Tom.

  4. 7 minutes ago, ollypenrice said:

    Yes, I felt there was a whiff of green across the middle, going horizontally. However, trying to fix it threw the other regions out of colour balance so I decided to let it be. I didn't run SCNR green on the linear data. Perhaps I should have done.

    Olly

    Try SCNR on the full image, it might only adjust the middle section.

    T.

  5. 22 hours ago, symmetal said:

    Hi Tom,

    Yes, those fits gain settings don't make any sense. The Sony datasheet for the IMX455 states max 36dB of gain. Can you confirm that the gain setting on Low is reported as 0 in the fits header. Also if you post the Low, Med and High EGAIN settings from the fits headers it will give an indication of the actual gain being used.

    I assume Atik haven't replied to your email yet.

    Alan

    Yes the low gain value is 0 as per Astroart header data. 
    I haven’t written to atik yet as I wanted to get the tests done first so that I can word my mail correctly. I ll send it this weekend.  Tom. 

  6. On 01/06/2022 at 17:21, symmetal said:

    I forgot to say that the fits header will show the GAIN and OFFSET values of the image, hopefully with actual values for the gain, and the EGAIN entry will show the electrons/ADU value from which the gain can also be determined. If you post those values for the LOW, MEDIUM and HIGH presets it will be useful Tom. 'Astroart' or 'Fits Liberator' will display the fits header. 😀

    Alan

    Good thinking and yes the values are there. So even though the manual says the Gain goes from 0-35 the Medium and High have much higher values.

    image.png.5929296647edb873438b301a33e4085f.png

     

    image.png.46742caae610ce5ff92bd89dc9c474b8.png

  7. 4 minutes ago, symmetal said:

    HCG is a feature in the latest Sony sensors. It's built in to the sensor circuitry itself as one of its readout modes. There is a LCG (Low Conversion Gain) mode too for use in bright conditions but astro cameras don't enable that mode. 😀

    All the ADC conversion circuitry is built into the CMOS sensor chip too. Each sensor column has it's own ADC circuitry, so there are 9576 ADC converters on your IMX455 sensor, unlike CCD sensors where there is one ADC which is on a separate board to the sensor.

    So the HCG mode is there if Atik choose to enable it.

    As you use SGP Tom, like me, you probably aren't yet aware that the gain and offset can be set in SGP too which can catch you out. I just set it in the Ascom driver and don't let SGP change it but I do enable the gain and offset to be inserted into the image filename as a convenient check.  If you insert _%cg_%co_ as part of the SGP filename template you'll get a filename similar to this

    M31_Lum_60sec_gain_100_offset_50_1x1_-15C_2021-09-06_frame44.fit

    In the SGP control panel you can set gain and offset for the whole sequence here, though I leave it 'Not Set' so it uses the Ascom driver value. You can set higher gain when binned for quicker autofocusing if you wish.

    309124246_ControlPanel.png.fac9718bd38473d4fb7e58b16626f741.png

    In the Sequencer itself you can click on the cogwheel next to each event here

    Sequencer.png.c5779c4e27f7e81bfd92586515f93e15.png

    which will bring up another panel like this where a different gain and offset can be set just for that event.

    897063376_EventOptions.png.5ca53b7a506b3250311388bc0ff3b9b5.png

    SGP checks the event setting first and if it's not set there it checks the control panel setting, and if it's not set there it uses the Ascom driver setting. Hope this helps. 🙂

    Alan

    Thanks Alan. I was looking at the main gain setting in SGP, but I was not aware of the Cog wheel second option, so thanks for that.

    I'll add in the meta data to the files too, its good info to have.

    I'll let the Ascom driver start with the Power save and Low, and go from there for starters.

    Tom

     

  8. 7 minutes ago, gorann said:

    It is something you get with the ZWO and QHY versions of the latest sensors (IMX 410, 455, 492, 533, 571) and seen as a sharp reduction in read noise when you move the gain over a certain threshold. Something kicks in in the amplifyer. Not sure if it is built into the Sony chip or in the amplifyer used by the camera manufacturer. I use that setting all the time with my ASI2600 and 6200 to be able to get more subs out of a give time period and assume it will significantly increase my S/R I get that night. Here is what it looks like for your sensor on the ASI6200, so everyone would use the gain 100 setting:

     

    Screenshot 2022-06-01 at 00.05.17.png

    So a few things must be happening here.

    Either the Atik amp works differently to ZWO, the most likely I would think, or the software is controlling it differently.

    Given the chips are all from Sony, I would think that any specific silicon P/N gate signal or what ever it the correct term, will be the same. So any cliff in voltage signal should be the same for all further cameras manufacturers.

    My data is not showing a cliff anywhere in the Std Dev. (We are taking the Std Dev in ADUs as the Read Noise here in Bias frames)

    Now the Atik manual is very vague about settings that "PowerSave – This mode allows the camera to shut down non-essential circuits during exposures"

    Who knows what this means. Maybe Atik are reading this thread and enjoying our struggle here :)

    Tom

  9. 25 minutes ago, gorann said:

    This thread is getting more an more interesting and I look forward to ATIKs explanation of how it all works. It would be very odd if they did not provide the HCG option.

    Yes its fun taking and plotting the data and seeing what the cameras does.

    Is HCG normal in all other CMOS chips? I dont know, or is it only dependant on how the software reads the chips, sets the gain etc...

    Tom

  10. 1 hour ago, symmetal said:

    As the camera gain increases the noise range from min to max will increase as well, likewise the SD. You therefore need to increase the offset to ensure the min value stays above 0. Your Medium and High presets both seem to have a very high gain setting so even with the higher offset applied it's not enough to avoid the black clipping.

    The power settings could be USB speed settings as you say. The Atik manual doesn't mention whether ROIs can be set for planetary imaging. Without a ROI the frame rate will be very low on such a large sensor.

    Alan

    Yes a full frame planetary camera seems counter intuitive.

    Increasing the offset to stop clipping makes sense as I read it.

    Thanks for all your inputs here.

    I think its lead me to the Low setting, and Power save. That suggests that it'll also keep the full well depth high. Unless I m chasing super dim nebula, I wont change those settings.

    Tom

  11. 1 hour ago, symmetal said:

    Yes there seems little real difference in the noise in the three power modes.

    I'm not sure what the LOW, MEDIUM and HIGH settings refers to as Medium and High show a large min to max change with black clipping present. Power Save Medium and High show black and white clipping too.

    I'll be interesting to hear what Atik say concerning the HCG setting.

    Alan

    Edit: It looks like Low, Med, High are possibly preset gain/offset settings with Low being gain 0 as the SD figures agree with your SD table. Med and High show much higher SD values than your SD table on the right. I'd have thought the SD would be significantly higher at higher gain settings than your right SD table shows, so not sure if the higher gain values are being set correctly when entered manually.

    The preset offset value of 200 is a bit low at LOW setting though is just avoiding black clipping.  At MEDIUM and HIGH the preset offset is too low but in Power Save mode it white clips anyway so no offset value entered here would be much good. 🤔 Does it display what the actual gain settings are when you preset MEDIUM and HIGH.

    No there is no mention of what the gain and offset values are actually running at in the preset modes Low Medium High. However given the Background values that match the closely the ADU, it looks like they run at 200, 400, 1050.

    So maybe as the manual says, the Power save, Normal and Fast which show very little differences are like the USB speed in your ZWO menu. I can see how Fast would allow lots of frames to downloading to beat the seeing.

    I m at a loss to explain the Medium and High Presets though. Looking at the Medium and High frames though, the 0 ADU seems to correspond to the lower x axis, yet the offset appears to be at the 400 / 1000 mark.

    I guess either the gain is maxed out, and / or internally the s/w is doing something to the chip causing the data to get clipped on the Min values. Very confusing.

    See attached Stats FOV from the Medium Preset setting on Normal Mode.

    Tom.

    image.png.5bc79d5fb39a20d881ef3cddd797f7d8.png

  12. Here are some more results from todays tests. Taken at room temp, and an offset at 400 for the table of varying Gain values.

    Then I tried different "Power" modes. The Power Save is not the lowest noise / SD value as the manual states.

    All in all I think it might be best to just go with the Power Save mode, and Low settings that Atik set.

    There is no obvious HCG cliff in the data as in the ZWO settings.

    Tom

     

     

    Apx60 Bias tests.jpg

  13. 10 minutes ago, symmetal said:

    Possibly. It's worth doing the tests in normal mode and see what the SD figures are for comparison.

    Alan

    Yes I should that with all the settings and see. I'll wait for Atik to reply first I think. The fridge is now full of food :)

     

  14. 46 minutes ago, symmetal said:

    Hi Tom,

    From your results there is no indication than HCG mode has been enabled at any gain setting. The noise SD just increases with gain just like with a camera without HCG. HCG is built into the sensor though I expect there is an option to enable/disable it via software. I think it's worth dropping an email to Atik to query this as this is a major selling point of cameras with HCG sensors.

    However, your SD figures are similar to what I have at gain 100 (your gain 10) when HCG is enabled on the ASI, which may imply that HCG is enabled all the time on the Atik. 🤔 At room temp I have SD 5.9 with HCG on and SD 12.9 with HCG off.

    Regarding offset I would think that 500 is a reasonable figure which would give you ADU minimums of around 350, though offset 400 would be OK too if you wish.

    Alan

    Maybe this is the HCG equivalent?

    I had it set in the capture program for the test shots.

    image.png.ec2b4aea47fc55740b1a95c386d4cb0b.png

  15. 19 minutes ago, symmetal said:

    Hi Tom,

    From your results there is no indication than HCG mode has been enabled at any gain setting. The noise SD just increases with gain just like with a camera without HCG. HCG is built into the sensor though I expect there is an option to enable/disable it via software. I think it's worth dropping an email to Atik to query this as this is a major selling point of cameras with HCG sensors.

    However, your SD figures are similar to what I have at gain 100 (your gain 10) when HCG is enabled on the ASI, which may imply that HCG is enabled all the time on the Atik. 🤔 At room temp I have SD 5.9 with HCG on and SD 12.9 with HCG off.

    Regarding offset I would think that 500 is a reasonable figure which would give you ADU minimums of around 350, though offset 400 would be OK too if you wish.

    Alan

    Thanks for your reply Alan. I'll mail Atik and see what they say. It would be good to know exactly what their presets do to the camera. Its hardly an Intellectual Property thing?!

    I certainly didnt get anywhere near your 12 SD values, so as you say maybe it was always On, or On from my "Power Save" selection.

    Yes my 1000 is way to high on offset I think. I'll drop that by at least half.

    Tom

  16. On 23/05/2022 at 01:25, symmetal said:

    A quick check to see that the HCG mode is enabled in your Atik Tom is to take 2 bias frames, one without HCG and one with and look at the results in Fits Liberator or similar fits viewing program. On the ASI6200 HCG is enabled at gain 100 and above. Here are my results below for gain 100 and gain 99, (HCG disabled) Note the difference between min and max ADU values and the Standard Deviation. HCG on, SD is 6.0, HCG off, SD is 12.9. This is at room temperature too.

    As your gain settings appear to be in steps of 1dB, I suspect it will be enabled at gain 10 on the Atik, assuming it is automatically enabled on the Sony sensor chip rather than being set by the controlling software. You can take test bias frames at say gain 0, 5, 10, 15, 20 etc and see where the read noise decreases sharply, ie the SD drops noticeably. That's where the HCG mode kicks in. That's the gain setting I would use all the time. 🙂

    Also, you can see if your offset is good too while looking at the bias frames. The minimum ADU value must be significantly above 0 to avoid black clipping. It's 368 ADU on mine at gain 100. My offset setting is 50, with an offset increase of 1 increasing the output ADU by 10. Offset 50 therefore adds 500 ADU to the output which you'll note is where the peak of the bias histogram is, also corresponding to the image mean or median value. If the offset was 0 then the peak of the bias histogram would be around zero too and the left half of the histogram would be clipped to black, which is bad. I could get away with offset 30 without clipping, but I left it at the default 50. The tiny loss of dynamic range due to the offset being too high is insignificant.

    As your offset is in ADU steps of 1 rather than 10, I would start with offset 500 and see what the bias looks like. Aiming for a minimum image ADU of at least 200 to 250 should be fine. Note that as the gain is increased the offset may need increasing too to avoid black clipping, but you'll most likely only use the camera at the one gain setting where HCG is enabled. 🙂

    420726446_Biasatgain100.png.6b30068d5421e0347d945213a6d60dd3.png

    1803122249_Biasatgain99.png.6e76a68665144d6b2ca61105905b886f.png

    Alan

    I managed to borrow a 12v mains power supply that gave 2.5A Not quite the 5A needed to use the full cooler. So instead I put the camera in the fridge, where the sensor thought it was 11C. It was in there for over an hour and cold to the touch. I would have thought it would have been 5C approx.

    Anyway here are the Bias results using Noise Evaluation script in PixInsight and Statistics in AstroArt6

    So first thing to note is the difference in both programs seeing the noise at different Gain settings. If you assume Standard Dev = Noise from the two programs.

    Once you increase the Offset, which I guess gives a better result on the data, as no black clipped data is rejected then the 30 / 35 Gain seems to show the lowest Noise in PI (One cell is incorrectly marked Blue as the lowest in the image offset 1000 gain 30), but 0 Gain is the best in AstroArt6

    So very confusing, I m none the wiser which would be best. Especially given that the Atik manual suggests dont go over 30 on the gain.

    From the data the AstroArt6 Standard Deviation is a straight increase line.

    The Noise script gives an "M" shape for all 3 offset data sets.. So I dont know about HCG on this camera.

    Anyone want to give an input to the data?

    Thanks Tom

     

    image001.png

  17. 21 hours ago, symmetal said:

    That's disappointing Tom.  Without the camera cooler running the power consumption is less than 1A and the ASI can be powered just from the USB3 connection, though a laptop may not supply enough current via USB3. I assume you were using the cigarette connector too. It does look like a power issue though as USB speed issues only arise while downloading and you have difficulty connecting.  My mini-PC on the scope will often hang downloading if the USB3 speed setting on the ascom driver is at 100%. I have it set to 75% and have no issues. You don't  seem to have that option though so that must be set automatically on connecting.

    The Atik has a standard 2.1mm centre positive connector so any generic 12V power supply you have supplying 2A or more would work for testing if you don't have the cooler running.

    Alan

    I had the cooler running to -15c from the car cigarette lighter port. It did download a few 300s the very first time I tried the camera. 
    so can’t say for sure what hung the software on this second attempt. I d rather test with the cooler running to get done graphs so I just may have to go get a 5amp rated 12v mains power supply as it could be a while before I get out to the observatory. I d like to be a little bit familiar so I can run it remotely once I get home. 
    Tom. 

  18. Ok well attempt one has sort of failed.

    I did manage to get the camera to connect in SGP, but it failed to save any Bias frames.

    So I went to Dusk which I downloaded, and it wouldnt connect to the camera.

    Third go was getting Artemis to connect, and it did. In the exposure settings there are the settings that match what SPG and the download manual sees.

    However it hung flushing a frame and I had to quit the program. So no bias frames were downloaded.

    At that point sitting in the idling car the battery on the laptop started to fail.

    Very odd behaviour all around. I really need a 220v AC adapter that can give 5amps to test this properly. Disappointing that this was not supplied with the camera really.

    Anyway at least the Artemis and SGP has the settings visible and changes can be made to them.

    Tom

    Apx Artemic capture settings.JPG

    Apx60 SGP Camera connection power save Custom.JPG

  19. 19 hours ago, symmetal said:

    A quick check to see that the HCG mode is enabled in your Atik Tom is to take 2 bias frames, one without HCG and one with and look at the results in Fits Liberator or similar fits viewing program. On the ASI6200 HCG is enabled at gain 100 and above. Here are my results below for gain 100 and gain 99, (HCG disabled) Note the difference between min and max ADU values and the Standard Deviation. HCG on, SD is 6.0, HCG off, SD is 12.9. This is at room temperature too.

    As your gain settings appear to be in steps of 1dB, I suspect it will be enabled at gain 10 on the Atik, assuming it is automatically enabled on the Sony sensor chip rather than being set by the controlling software. You can take test bias frames at say gain 0, 5, 10, 15, 20 etc and see where the read noise decreases sharply, ie the SD drops noticeably. That's where the HCG mode kicks in. That's the gain setting I would use all the time. 🙂

    Also, you can see if your offset is good too while looking at the bias frames. The minimum ADU value must be significantly above 0 to avoid black clipping. It's 368 ADU on mine at gain 100. My offset setting is 50, with an offset increase of 1 increasing the output ADU by 10. Offset 50 therefore adds 500 ADU to the output which you'll note is where the peak of the bias histogram is, also corresponding to the image mean or median value. If the offset was 0 then the peak of the bias histogram would be around zero too and the left half of the histogram would be clipped to black, which is bad. I could get away with offset 30 without clipping, but I left it at the default 50. The tiny loss of dynamic range due to the offset being too high is insignificant.

    As your offset is in ADU steps of 1 rather than 10, I would start with offset 500 and see what the bias looks like. Aiming for a minimum image ADU of at least 200 to 250 should be fine. Note that as the gain is increased the offset may need increasing too to avoid black clipping, but you'll most likely only use the camera at the one gain setting where HCG is enabled. 🙂

    420726446_Biasatgain100.png.6b30068d5421e0347d945213a6d60dd3.png

    1803122249_Biasatgain99.png.6e76a68665144d6b2ca61105905b886f.png

    Alan

    Thanks for all these great ideas. I'll do these tetss and post my results.

    Thanks Again Tom

  20. 15 hours ago, symmetal said:

    There's no mention of an anti-dew heated front window in the Atik manual either. 🤔

    I don’t even think there ever was one. It used to be a firmware change that you installed and you could set the power by setting the percentage I think. It was so long ago I can’t remember. However I don’t think it ever showed up as on anywhere in the software. 

  21. 1 hour ago, whipdry said:

    Ahh thats great thanks. Good to see the explanations of  gain and offsets. I imagine thats the most asked question from newbie CMOS imagers. I think I'll be taking lots of test shots to figure out what suits what objects.

    I didnt get the allen keys or the desicant tool in the box though. Luckily I have plenty of tools at hand.

    Tom

×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue. By using this site, you agree to our Terms of Use.