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tooth_dr

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Posts posted by tooth_dr

    Problem with flats mono CCD

    in Imaging - Image Processing, Help and Techniques

    Posted

    Just now, vlaiv said:

    Ah, that is opposite from what I assumed - this is under correction in flats.

    If we go to original formula calibrated = lights / flats

    and calibrated value is lower than it should be - we have two possible cases:

    1. lights are lower in value than they should be - this can happen from improper calibration (like multiple darks / bias subtraction, but I don't think it is the case)

    2. Flats are "stronger" than they should be (higher in value) - this can happen if one is for example calibrating flats with bias only and there is significant dark current, but I don't think it's the case here.

    Another reason why flats might be stronger, and this would be my main suspicion in this case - flocking and baffling of telescope - some unfocused light is making it's way to the sensor when using flats, bypassing "regular" optical train. Depending on scope type, this can happen with:

    Newtonian scopes if there is reflection from tube walls opposite focuser that end up going down the focuser tube, it can happen because reflection of secondary support that ends up in the tube. Focuser tube needs to be baffled as well, if it's not - it can "channel" light inside (multiple bounces coming directly from flat source).

    For folded designs with central obstruction it would depend on central obstruction fully covering aperture - if you look at the back of your scope you should not be able to see the light coming straight from aperture - it needs to bounce of secondary.

    Refractors should be pretty immune to this - all the light that enters telescope goes thru the lens, so there is simply no chance of it being unfocused and reaching sensor.

    This was my fault for describing it wrong in my first post. Sorry about that vlaiv.

    These were taken with an ED80 refractor.

    Im retaking some of the calibration data now as I’ve spotted the fits header is the darks and bias was different ie it says QHY9-CCD whereas the flats and dark flats just say QHY9 (they were taken a couple of days ago).

    Problem with flats mono CCD

    in Imaging - Image Processing, Help and Techniques

    Posted

    34 minutes ago, Adam J said:

    In general I don't think that you would use both dark flats and bias at the same time, in so far as I am aware you use one or the other and for CCD's the choice is BIAS. Using both might be tripping APP up a little. 

    Hi Adam.  The final integrated image is actually quite bright, so this ties in with that, it's like the overall brightness has been boosted.

    Problem with flats mono CCD

    in Imaging - Image Processing, Help and Techniques

    Posted

    28 minutes ago, Xiga said:

    That's a good point Adam. APP is now 'smart', so it is supposed to handle the files automatically for you. I still manually select mine one batch at a time (just because I've been doing it that way since the earlier versions, and, well, I'm on old dog, lol) so I don't know how well this functionality works. If you throw it files it doesn't actually need, will it ignore them? Or does it just know how to handle all the myriad calibration files, assuming you've selected all the right ones to begin with? Not sure tbh.

    Another tip for you regarding APP - you don't need to finish a stack to know if calibration is working or not. As soon as you've finished Step 2 (Calibration) you can select any Light sub from the list at the bottom, and change the drop-down box at the top of the screen from 'Linear' to 'l-calibrated'. This will show you what the Calibrated Light sub looks like, and it should be obvious if it's working or not.

    If the Bias files don't solve the problem for you - thinking outside the box here - you definitely haven't mixed up your Atik and QHY flats by any chance?

    Thanks Ciaran.  My calibrated subs look 'ok, certainly pretty flat to my eye, but if I look hard I can see the dust bunnies in some of them.  That was the first thing I checked and prompted me to post on here! However the stacked result has a very pronounced defect!  But this thread is useless without PICTURES!  When I mean APP would use them automatically, I just did one session and one camera, and added the above files.  No other cameras, or sessions were part of the files, I'll try that again without Bias and then without Flats to see what happens :D

    Meteor Camera

    in EEVA - Reports

    Posted

    On 06/02/2019 at 00:44, don4l said:

    That is  a good one!

    Have you heard of UKMON?

    https://ukmeteornetwork.co.uk/

    It might be worth sending them an e-mail.

     

    Thanks for the heads up, I have been followig them and looking at their various publications.  I'm joining Nemetode http://www.nemetode.org/ and have been in touch with the founder and a couple of members.  Interesting it turns out the founder William went to school with my brother, so it's a small world indeed.

     

    Problem with flats mono CCD

    in Imaging - Image Processing, Help and Techniques

    Posted · Edited by tooth_dr

    3 minutes ago, Xiga said:

    Hi Adam

    I think @vlaiv is right about the Bias files. I don't use Darks myself with my DSLR (although I keep meaning to run some more tests on that) however, it is my understanding that if you are using Dark Calibration files, then you should not also use Bias files, as I think it will remove the dark current twice. So it's probably over-correcting at the moment.

    Try without the Bias files and see how it goes.

    I will try this later Ciaran. Thanks ??

    I just assumed APP would do what was needed automatically, and use them appropriately 

    Problem with flats mono CCD

    in Imaging - Image Processing, Help and Techniques

    Posted

    34 minutes ago, vlaiv said:

    If both outer field and dust shadows are brighter - that is over correction.

    calibrated = light / flat

    If calibrated is larger in value, from above simple equation we have two possibilities - either light is larger than it should be or flat is lower than it should be.

    Light can be higher under these conditions:

    1. dark or bias (or both) is not removed, so there is residual signal besides light signal

    2. there is source of light pollution which is not present when doing darks / bias files - such as scope having a light leak and you take camera off for dark / bias frames

    3. Darks were "colder" than light subs.

    Flat can be lower that it should be if:

    - not properly calibrated (which I doubt since you took same duration flat darks under same conditions)

    - flats were taken when sensor was cooled but matching darks were taken with hotter sensor.

    - sensor is in non linear region when doing flats - again I doubt this since you went for ADU at about half way and in general non linearity would produce host of artifacts with calibration.

    Here are some questions that could help to understand what is happening:

    1. Was temperature regulation same in all corresponding subs?

    2. How did you acquire subs (on scope / off scope / day / night - particular conditions for each)

    3. Exact calibration method used. Maybe try without bias - it's not needed for fully matching darks.

    Thanks vlaiv

    What you are saying is very helpful and this will hopefully get me to the bottom of the problem.

    1. All subs were taken at -15oC. The camera sometimes fluctuates to -16oC but 1/2 a degree should make much difference.

    2. Lights - night time, luminance filter

    Darks - on scope in shed at night time with end cap on

    Bias - on scope in shed at night time with end cap on 

    Flats - taken using a computer monitor set to white page, four sheets of white paper over end dew shield, held by a cardboard holder, scope about 40cm from screen, at right angles. Also used same luminance filter.

    Flat Darks - on scope in shed at night with end cap on

    Camera not moved between lights and flats.

     

    Problem with flats mono CCD

    in Imaging - Image Processing, Help and Techniques

    Posted

    1 hour ago, LightBucket said:

    Hi,

    I am just getting to grips with APP, so can’t really help at this point, but am looking for some CCD data  to test with as my own data does not have flats I have only used darks till now...so if you are willling to let me Have a go with your data, maybe I can help...

    Have you not got your Atik 383 anymore..?

    Thanks William. I can upload data if you want no problem.  I still have the Atik.

    Problem with flats mono CCD

    in Imaging - Image Processing, Help and Techniques

    Posted

    I processed a few subs of Leo on Wednesday night, using the frames listed below.  The camera is a QHY9 mono with the KAF-8300 mono sensor.  I used Astrophotography Tool (APT) for data collection and Astro Pixel Processor (APP) for processing.  I used the 'CCD aid tool' in APT to calculate a mean ADU of about 26k for my flats.  This resulted in an exposure of 8 seconds.  In my stacked image from APP, the outside of the image is bright and some dust bunnies are visible.  Any suggestions of what to try next?

    LIGHTS: 24 x 300s

    DARKS: 30 x 300s

    FLATS: 30 x 8s

    DARK FLATS: 30 x 8s

    BIAS: 30 x 0.01s

    • Like 1

    Meteor Camera

    in EEVA - Reports

    Posted

    On 02/02/2019 at 14:35, jam1e1 said:

    good effort! i find my Oculus only captures the brighter meteors, whilst more FoV there is a trade off of sensitivity (if thats the right term!). I have thought about doing video setup too

    Thanks Jamie.  Since that video was taken I realised the focus was off by a bit.  So I did the needful - got the wife up on the shed rood and she adjusted it whilst I viewed the screen.  Now it's much better and I get less false recordings.  The scintilations from out of focus orion stars were causing the video to trigger a detection, and I filled 250GB hard drive in two days!

    No fireballs yet but about 30+ meteors in 4 nights.  The Watec 902H is very sensitive, and along with the 8mm F0.8 lens (pure fluke I found this on ebay USA), it should pick up meteors down to magnitude +4 or +5

     

    Here is a capture from Saturday.

    https://streamable.com/eiwn0

     

     

    • Like 1

    'AllSkEye' all-sky imaging Software (Windows)

    in Discussions - Software

    Posted

    16 minutes ago, AngryDonkey said:

    Hi Adam,

    Unfortunately analog cameras are not supported and there is currently no support for the DirectShow driver (although that might change sometime), so webcams won't work either.

    AllSkEye works with most cameras supported by an Ascom driver and all Starlight Xpress and ASI Zwo cameras.

    The ASI 120MM or MC should work, although there are many USB related issues with that particular camera (and ZWO are not really supporting it anymore). There are some workarounds for it so if you need help, just get in touch. The AllSkEye support forum would be best for this as I don't want to clog up this thread with support related posts.

    Mike

    Ok Mike, thanks.

    Meteor Camera

    in EEVA - Reports

    Posted

    1 hour ago, Helen said:

    Thanks ?  looks good! I need to work out where I can mount the camera.  It is housed in a standard security camera housing (long version not dome!), so I need to check it is water tight if pointed straight up!  But it has a dew protection system, so I'm hopeful for some nice views (mostly of clouds I fear though  ? ).  I suppose I could test over the next few days by watching snow storms ? 

    Helen

    Mine is in a heated standard cctv enclosure too. It’s at 45 degrees and so far so good. I’ve one at 5mm and it’s ok. But I think much lower and the housing interferes with the FOV. 

    Meteor Camera

    in EEVA - Reports

    Posted

    4 minutes ago, Helen said:

    What software/setup are you using Adam?  I picked up a meteor cam set-up from ABS before Christmas (mostly for the watec video cam in it which I'm planning on using for lunar impacts in the future) and it would fun to try for meteors too ?

    Helen

    Very good Helen. I bought UFOCapture V2 which seems to be the preferred choice for capturing meteors. It’s not cheap at ¥20k but can be used on multiple PCs at the one site and I have 2 cameras. 

    • Thanks 1

    'AllSkEye' all-sky imaging Software (Windows)

    in Discussions - Software

    Posted

    10 hours ago, AngryDonkey said:

    Thanks Gav, glad it's working!

    A difficult one to answer! It's really the camera/lens combination that makes the biggest difference i.e. how much of the sky you will manage to get onto the image. Most people are trying to achieve 180 degrees but personally I prefer 150 to 160 degrees, you won't see the horizon all the way round but I think it makes much better use of the sensor area. ASI ZWO cameras are popular as they are relatively cheap and many of them come with a basic all-sky lanes in the package. Another thing to consider is the housing. This is not so much an issue if you setup and take down every night while you do other astro stuff but if you are thinking of a permanent setup then it obviously need waterproofing, heating, etc. There are ready made solutions such as the Starlight Xpress Oculus but many people created their own, with some really genius solutions (and can be done much cheaper). There are a few threads on here describing the process.

    Thanks Mike

    I just asked as I have a couple of mono and a colour camera (USB) with the 640x480 sensors, and a 2.1mm lens.  I do have a ZWO120MM but it's being used as a guider.   I tried it very briefly last night but I got an error message trying to connect a DMK camera, so I'll sit down with the instructions and work it out.  Will it work with an analogue camera via a USB 'grabber' (eg pinnacle dazzle)?  I'm in the process of thinking about an enclosure, and making my own, so that's the long term plan.

    Adam.

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