Jump to content

Stargazers Lounge Uses Cookies

Like most websites, SGL uses cookies in order to deliver a secure, personalised service, to provide social media functions and to analyse our traffic. Continued use of SGL indicates your acceptance of our cookie policy.

sgl_imaging_challenge_banner_30_second_exp_2_winners.thumb.jpg.b5430b40547c40d344fd4493776ab99f.jpg

Thalestris24

Members
  • Content Count

    6,452
  • Joined

  • Last visited

Posts posted by Thalestris24


  1. 45 minutes ago, Merlin66 said:

    I'm revisiting this topic.....

    I found that most (All?) CMOS sensors are fitted with microlenses and the immediate  chip cover plate can vary in thickness from 1 mm to 5 mm (!!!!)

    If this was a real problem then surely it would be showing up on more and more images taken with CMOS cameras?

    It seems strange the the prime example here and CN is of one star - Anitak

    I've never experienced this type of issue.... we do suffer more from "ripples" in our spectrographic profiles - an intensity waviness - thought to be due to either/ both the internal structure of the silicon chip or interference between the cover plate and the silicon surface.

    See: 

    https://www.lensrentals.com/blog/2014/06/the-glass-in-the-path-sensor-stacks-and-adapted-lenses/

    http://www.astrosurf.com/buil/CMOSvsCCD/index.html

    https://britastro.org/sites/default/files/attachments/SpectralResponse_WhitePaper_April09.pdf ( thanks to Robin for the link)

     

    Is there a real problem here?????

     

    Isn't it more of a phenomenon rather than a problem per se? I gather it's caused by some variation of the Talbot(-Lau) effect? There is lots of physics and maths online that explains it - it's a bit beyond,me but essentially I understand it to be a diffraction effect which results in 3d self-imaging. I suppose the sensor + microlenses behave like a diffraction grating - under certain circumstances. I imagine it depends on various physical spacings, reflecting surfaces and particular light sources, angles, wavelengths etc.  (don't ask me!) which nefariously combine to generate the (unwanted) pattern. When I first saw examples it immediately reminded me of some x-ray diffraction patterns. Perhaps it actually occurs quite a lot but doesn't normally get made visible? It's quite fascinating, really. I think if  I were younger and brighter I'd probably like to delve deep into it. However, I've never (yet) witnessed it directly. Is there any connection with using an oag setup?

    https://hal.archives-ouvertes.fr/hal-00998967/document

    Louise


  2. 3 minutes ago, Dr_Ju_ju said:

    Louise (and any other newcomers), another quick tip to pass on....

    … and that is, to keep your hot end \ heating block clean, especially internally, where over time deposits will accrue, resulting in blobs, stringy-ness, blockages, bad bed adhesion etc.

    Externally its relatively easy to use a fine wire brush to gently clean off any deposits, but internally it will probably require stripping down the nozzle \ heater block \ heat break, into their component parts. This may well require that the block is heated to working temperatures to 'break' and seals, SO BE CAREFUL, and use suitable tools etc. Also when hot, its then much easier to dislodge any caked on deposits....

     

     

    Thanks for the tip! I think the printer came with a length of stiff 'wire' thingy which I presume is for cleaning the nozzle? Not used it yet. There are also some spare nozzles - maybe I'll need a new one at some point...

    Cheers

    Louise


  3. 6 minutes ago, michael8554 said:

    Hi Jay

    Your Calibration was carried out at Dec = 90, in other words pointing at the North Pole, or maybe Polaris..

    So when Calibration started, PHD2  started stepping the mount west. All that would do is rotate the mount, but it would still be pointed at Polaris, which would only move as much as your Polar Alignment error.

    Calibration should ideally be carried out at Dec = 0 and pointing roughly south.

    Dec 0 isn't your local horizon, Dec 0 is only 90 degrees down from Polaris .

    Read these Best Practices:

    https://openphdguiding.org/phd2-best-practices/

    Michael

    So it is! I confess I hadn't looked at the PHD2 log....


  4. 13 minutes ago, JamesF said:

    They must have changed it fairly recently then.  The URL you gave definitely used to be correct, Louise.

    James

    What's annoying is that there's no link to the correct url on their main page (that I could see). The broken link was on a piece of paper in the box for the gpcam3 I recently bought. Oh well. I'm not even sure if I really needed it in the end! It's a usb 3 camera so I plugged it in a laptop usb 3 socket. Power light came on but couldn't connect :( I switched to a usb 2.0 and it worked fine (with the usb 3 cable). I know my usb 3 port works normally so dunno what was going on there. Connecting to the usb 2.0 worked fine with SharpCap. Anyway, gpcam3 178m now installed on a Travelscope 70 ok :). The qhy5l-ii mono that was on the scope is destined for the Lowspec Spectrometer guiding unit. Musical chairs for astro cams! Meanwhile, I updated Win 10 on the laptop earlier and the battery icon has disappeared! Tut! I'll have to search for a solution to that next...

    Louise

     


  5. 19 minutes ago, Stub Mandrel said:

    This is testing on my PC (as debugging on my laptop is horrible with the nasty keyboard)

    I haven't got ASCOM on the PC, so downloading that, although not having it doesn't affect other cameras.

    Hi Neil

    Shame you haven't got Ascom. I found some other complaints about SharpCap not recognizing the asi1600. It relates to v2.9 and 3.0 have you got the latest v3.2.6137?

    Louise


  6. 1 hour ago, Stub Mandrel said:

    Help! Sharpcap is eternally stuck 'detecting cameras'.

    ASI1600 shows in device manager and works with ASICAP

    Any ideas @rwg?

    Thanks!

    Hi Neil

    I don't know why SharpCap would be stuck but what frame rate are you trying to run at - lower might be better. I remember I had problems trying to run my qhy183m but using the Ascom driver worked (even though SharpCap moaned). Have you got the latest version of SharpCap installed?

    Louise

    ps isn't ASICAP for Android? Maybe you have a usb problem?


  7. 1 minute ago, Merlin66 said:

    Louise,

    The good news is light pollution doesn't existing in spectroscopy!!

    Valerie does her work from the centre of Paris (!!) Christian works from his balcony near Toulouse.....

    We can remove the unwanted sky glow signal - sodium, mercury lights etc. very easily during processing. LED lights.....well that is more difficult.

    Ken

     

    Well, that sounds encouraging! There's a wide mix of Glasgow lighting types contributing to the skyglow. Even with Ha I'm limited. I usually don't bother trying to do anything until the nearby all-weather pitch switches of it floodlights after 10pm. I'll just have to see what I can do.

    Louise


  8. Just now, Merlin66 said:

    Louise,

    I should also have added that spectral exposures can be very long - to build up the signal and improve the SNR. I use 20 x 240s min subs (!) hence the benefit of a cooled mono camera.

    I don't know if SharpCap can handle cooled cameras and long exposures.

     

    etacar_20190315_394_KMHarrison.jpg

    Yes, SharpCap can control cooling and do long exposures ok. However, the length of my subs is generally limited by the city skyglow :(. With the Atik383l+ I can probably do 360s with a normal sub but then I'd be using a lp filter or Ha filter. Not sure how long I'll be able to get in pure luminance. That looks a nice Eta Carinae spectrum! That is about mag 6? So quite bright and the Atik314 has quite a high qe. My Atik383l+ isn't so sensitive so presumably would need longer exposures. My snr would be a lot poorer. I can only see to the East and not much higher than alt=35 deg. Nothing involving astro imaging is simple or straightforward for me!

    Louise


  9. Just now, Merlin66 said:

    Louise,

    Don't know how ShapCap handles darks, alignment and stacking. I use an ATik 314L with the Spectra-L200.

    Buil's ISIS, Valerie's VSpec and John's BASS Project are all suitable for the spectral processing - taking the raw spectral image to a 1D profile.

     

    Oh, ISIS not IRIS! I have some image processing software called IRIS... SharpCap pro does live stacking with optional darks, flats and auto alignment (or can just guide with PHD2). I can't see any way to take flats, though. Not sure about image measurement. 

    Louise


  10. 8 minutes ago, Merlin66 said:

    Louise,

    Yes, you've got the main points.... the telescope focuses the star image onto the front of the slit plate (and seen by the guide camera), the light goes through the slit and is made parallel by the collimator... the beam hits the grating, the light is dispersed into a spectral image which is then focused by the imaging lens onto the CCD chip.

    At this stage bench testing is the way to go...a bright desk lamp (or fluoro) shining into a paper diffuser on the entrance should give enough light to work with at the slit.

    You may be able to use your dummy grating (mirror on 3D block) to align and focus the collimator and confirm the imaging arrangement. 

    Which program will you use to obtain your spectral image? It should be able to analyse the image (using the measurement/ profile tools) and give you a FWHM result - mine (AstroArt) shows the result down to 0.01 pixel.

    Ken

     

    Hiya

    I'd not really thought about specialist imaging software - I kind of assumed I'd be able to do it with SharpCap as I did with the Star Analyser? Is Christian's IRIS a possible? Possibly AstroArt, especially as you recommend it :), but I wouldn't want to fork out for something unless I already know all the kit is working ok. I don't get the best guiding here, not helped by having to do my imaging through an open window... So I might put everything together only to find my results are rather poor :(.

    Thanks

    Louise


  11. Hi Ken @Merlin66

    Useful info in your last post on Rockmover's thread :) Paul changed his design slightly - he made the camera fl = 100mm and dia 30mm so fr = 3.3. However, I currently have one which is fl=87mm and dia=26mm (fr=3.34). It should allow attaching my Atik without too big an extension. My collimator lens is fl=121mm. So with a slit gap of 20 um it would appear as 14.4um. With my Atik383l+ that means it should cover 2.7 pix when focused. I suppose that means 3 pix in practice? When I've tried to test focus the collimator it's proved quite difficult since illuminating my diy practice slit from the 'scope' side tends to generate diffraction though I did get some ok images via Sharpcap. However, I'll be testing it more properly with all the right components in place - hopefully within the next week. Um, I have been assuming that, on its own, the imaging camera is focused on infinity/a distant object? Hope that's correct... I was using a second test mirror to see outside through a window with a Touptek camera in place of the proper imaging camera. I was able to get an image of distant objects ok. I'll repeat with the Atik attached next. I understand that an attached scope will focus it's image (normally of a star) on the slit? The photons which exit from the slit are collimated by the collimating lens which transmits the beam to the grating and the spectrum is then (hopefully!) seen by the imaging camera. Hope I've got that right!

    Thanks

    Louise


  12. 7 hours ago, dyfiastro said:

    I have only been playing around with tinkercad so far but I have found that it has a metric thread generator built in.
    I am currently in the process of designing an adapter for my 130PDS so I can mount the MPCC inside the focuser tube.
    For this I needed T2 and M54 Threads, the generator only goes upto 50mm but the T2 threads have so far worked after a few trial and errors to get the correct internal thread sizing correct.
    Nothing stopping you using tinkercad for the threads and then importing them into fusion for the rest of the design.

    As a side not regarding print beds, my ender pro came with a magnetic bad which has been a godsend. the fact that you can just peel the bed of and then peel the print away makes life a lot easier.
    I have cut a number of mirrors for when I want to have a glossy surface as the magnetic bed leaves a matt one. I have found that a small amount of IPA applied to the bed and print make the print pop right off (you can almost hear it cracking and releasing as the IPA is evaporating)

    Thanks for the suggestion re Tinkercad. I can do it in Fusion 360 and the original lowspec stl files already had T2 threads. At the end of the day it's trial and error to try and get the print to work properly however you generate threads. I have the magnetic bed also and it does make it fairly easy to remove most things.

    Louise

    • Like 1

  13. 10 minutes ago, Rockmover said:

    Yes, this is all making MUCH more sense now. I am going to quickly 3D print a square holder (same size as the grating) with a spot for the guide mirror.  Then I can just put that in and align the collimater position. 

    This is a really fun project, and I know its evolving, but I'm surprised no one has made a nice YouTube video as a guide for building and setting this thing up.  Hopefully, if my unit is successful I can make that (PART 2) for others so they don't have the struggles I am having.

    The struggle is half the fun! If it was made too easy it wouldn't be so interesting. Overcoming hurdles is how you learn about something :)

     


  14. 6 minutes ago, Rockmover said:

    That is the OVIO guide platform.  Everything makes sense now, I now just need to wait for the OVIO slit ring to arrive from JEULIN....or make one as you did.

    Ah yes, I recognise it now - not used to viewing it like that! I just took a 1" round mirror and cut a short line in the backing with a scalpel. Then just taped it in place. Not good enough for a proper slit (though maybe with a new blade and a bit of practice...)


  15. I don't recognise that diagram - where is it from? It's the non-shiny side that's used. I found it a bit confusing and counter-intuitive too. However, having tried it out I believe it will work ok. The guide camera is focused on the slit. The telescope is also focused on the slit. The guide camera can then see the star and can guide on it. I think it might be quite challenging to get a particular star lined up with the slit.

×
×
  • Create New...

Important Information

By using this site, you agree to our Terms of Use.