Narrow Band Imaging

Discussion in 'Astronomy, Exobiology, & Cosmology' started by Xelasnave.1947, Aug 25, 2018.

  1. Xelasnave.1947 Valued Senior Member

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    I have taken up narrow band imaging where instead of one shot a photo is made up by taking , in my case, seperate photos thru seven different filters.
    We have red blue green luminance O11 S11 and Ha filters to make up a photo.
    We take many exposures thru each filter and combine them seperatly and then make up a final image from the seven stacked groups.
    It has been a steep learning curve for me and I have not yet mastered the complicated processing which may take another five years...well longer as you continually improve and lets face it in astrophotography the sky is not the limit.
    Here is a sample of my first captures which are thru a small 80mm scope which because of the imaging in various wave lengths gives much more detail than using say a single colour astronomy camera or a DSLR.

    Alex
     
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  3. Seattle Valued Senior Member

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    The first image is stunning. Is the telescope a refractor for this particular purpose?
     
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  5. Xelasnave.1947 Valued Senior Member

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    Thank you.
    It was my first effort and I must say I was surprised so much detail became available.

    The image does not do the data justice I suspect as 50% of the game is in the processing.

    In a couple of years I should be able to get much more than I did on this first try.

    The scope is an 80 mm dia primary triple lens with a focal length of only 400mm making it a f5.

    I have not looked thru this scope as it was purchased soley for imaging.

    The second image suffers from my lack of processing skill.

    It has 6.5 hours of data taken in dark perfect conditions which should mean that it would be really something but my skill is not able to take advantage of the huge amount of data.

    I have spent probably 40 hours on it and will probably spend another 100 before I do the data justice.
    Alex
     
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  7. Xelasnave.1947 Valued Senior Member

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    Here is another.
    The colour is incorrect (lack of processing skill on my part) but I was happy with the detail given the small scope.
    When I use this new camera on my eight inch it should be pretty neat.
    I now have my mount, camera and its built in cooling device (these captures are taken with the camera 15 degrees C below) , filter wheel, electric focuser all controlled using my lap top with free software for all of that...
    And it was not all that expensive because prices for astro gear has dropped dramatically...thank goodness.
    But so much to learn still.
    To be honest I did not think I could do it at all.
    I am now going to step up to plate solving which is software that enables you to take a photo and identify exactly where your scope is pointing which means I will be able to photohraph objects that I cant see...cool eh.
    Thank you again.
    Alex
     

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  8. Dr_Toad It's green! Valued Senior Member

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    Do you use a FITS plugin for your image processor? You might also have to offset the image layers by a pixel or two, depending on the wavelength.
     
  9. Xelasnave.1947 Valued Senior Member

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    Forst image I used fits format but the camera default went to raw second time out.
    My processing has a long way to go.
    I have been only using photoshop and gimp for individual processing of RBG etc and then using layer mode in photo shop to put the seven groups together.
    I have not bothered doing dark frames or flat frames yet.
    Dark frames are shots with the lens covered to show up any hot pixels to subtract from the image and flat frame is in effect a shot with something white over the lens to show up any dust spots in the optical path which you subtract from the main image...there are also dark bias frames which are short exposures to enable further management of hot pixels.
    The camera is cooled to reduce noise which is just stuff that should not be in the image..its more complicated but I hope that gives a bit of an idea to the various processes.
    I should mention I use a free program Deep Sky Stacker.
    You load your light frames (actual photos) up to 300 in some cases of a certain exposure, your dark frames (say 20 or more) your flat frames (say 20 or more) and bias frames (say 20 or more ) and the program stakes the light frames and subtracts the "problems" found in the flat bias and dark frames.
    So if you put in 60 light frames of 120 seconds each you end up with a photo that has a total exposure of two hours.
    If you want to take an astro photo with a static tripod you can take a number of very short exposures say 10 seconds and stack them as Deep Sky Stacker wont worry that the stars move over your shots.
    I have taken photos "right way up" one night and turned the scope 180 degrees and stacked both the "right way up" and the "upside down ones" to get one photo all in one place☺

    I started with Startools yesterday for each group but have a long way to go to learn it.

    The program the big boys use is Pixinsite which cost about $400 which I am happy to pay but learning it will takes years I believe.
    Thank you for your interest.
    Alex
     
  10. Xelasnave.1947 Valued Senior Member

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    The third image thru the small scope with the narrow band approach seems to produce a better image than I got a while back using my eight inch and a dslr camera so I cant wait to see what the narrow band and the eight inch will do.
    Alex
     
  11. Seattle Valued Senior Member

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    Very cool. I hope you will continue to update this thread. Is there any (affordable) laser alignment (adaptive optics) like the professional observatories use to "remove" atmospheric effects? Something like the "God Particle" for astronomy.

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  12. Write4U Valued Senior Member

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    It is remarkable how Tele-photography can reveal patterns in the chaos at immense scales.

    Somehow this suggests a fundamental mathematical function of spacetime. Awesome!
     
  13. Write4U Valued Senior Member

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    You became the center of the universe.....

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  14. Xelasnave.1947 Valued Senior Member

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    Not that I know of.

    In the city I cant see the Celestial South Pole which is sortta necessary to get what we call a good polar alignment.

    The mount points South and is at an angle which just happens to be your latitude.

    If this is out the photo shows star drift.

    Because I can never get a good alignment I take only 30 second shots and being so short you dont notice the star has drifted.

    So I had to do it this way but the unexpected result was much clearer shots because you limit the atmospheric disturbance somewhat...further you get good frames and not so good so you only stack the best.

    A spin off of the mount not being perfectly aligned in addition to a better overall take is the slight movement helps reduce the noise in the photo as the movement over a session can be considerable and smear out the noise.
    In fact if yoir alignment is spot on you command the mount to "dither" which causes the mount to move slavery ghlty away from the position of the last capture.

    I also now run auto guiding.

    I have a very small telescope mounted on the main scope with its own camera. You select a star and the software monitors where the star is and adjusts the mount to keep the star in the one spot and one can take rather long exposures but given my experience with the 30 second approach I am only using 2 minute captures a ven though auto guide allows for much longer exposures.

    So I guess the short exposure is my approach to adaptive optics.
    Alex
     
    Last edited: Aug 26, 2018
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  15. Xelasnave.1947 Valued Senior Member

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    We are each the center of the observable universe☺
    Alex
     
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  16. Xelasnave.1947 Valued Senior Member

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    Many of you will have a dslr camera and a lens...can be 50 mm to whatever but many if you bought a two lens Canon deal will have a lens up to 300 mm...remember my scope is only 400 mm.
    So stick your camera on the tripod set it to take continuous shots say at 1600 iso and say 10 seconds ( adjust longer or shorter) take about 100 and stack them in the free Deep Sky Stacker program. It has various adjustments that you can do a basic process but you can take it to photo shop or down load free GIMP and be amazed.

    Alex
     
  17. Xelasnave.1947 Valued Senior Member

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    Doing this say with the Moon produces exceptional captures.
    But for the Moon download Registax again free and easy to use.
    Here is one my daughter and a very young friend took with a dslr thru my little scope...30 frames stacked in Registax...they were so excited to have produced this..all I did was focus the camera they did the download stacki g and processing.
    The young friend got such a confidence boost and even adults now think she is an expert☺
    Stacking will allow a shorter focal length and will enable great shots with a lens kit type deal.
    Alex

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    Last edited: Aug 26, 2018
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  18. Xelasnave.1947 Valued Senior Member

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    Here is a long exposure of the Milky way using a lens that I would snap the cat with...unguided on a mount that I highly tunned but an hour twenty from memory...I have put it here before but I hope it may encourage some folk into photography to have a go.
    But I think I could do similar with a modern dslr (this one is over ten years old taken on a six mega pix canon so a modern camera will pas this effort)
    Alex

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  19. Xelasnave.1947 Valued Senior Member

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  20. Seattle Valued Senior Member

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    Is the first picture the Horse Head Nebula?

    So, everything I'm looking at, other than nebula, are stars. Most are small points of light, some few of them are a lot brighter and bigger and are diffracted by the lens elements, is that an accurate explanation of the stars that look like diamonds?
     
  21. Xelasnave.1947 Valued Senior Member

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    Yes and the Flame Nebula.
    Probably but we would need to go thru one by one to be sure...
    Stars should be so small that we could only just notice them however atmosphere does not allow that...if they have spikes it may indicate they were captured using a Newtonian telescope but they should be round and small ... getting that is not easy...here is a shot thru my eight inch which is a Newtonian and you will notice what we call diffraction spikes.
    The secondary mirror is supported by four "vanes" and it is those vanes that give us the spikes.
    Alex

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  22. Xelasnave.1947 Valued Senior Member

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    Here are the scopes I use..both only have a dslr attached.
    The long tube on the small scope is my invention ... it is baffled to exclude stay light from nearby stars...something others dont worry about...however after I built this unit I was happy to find a similar set up on the Hubble Space Telescope....
    Stars present as small specks of light but you see that light where ever you are so a lot more gets in the tube than most think...in my view.
    Alex

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  23. Xelasnave.1947 Valued Senior Member

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    Here is the eight inch. Sorry had to trim it down to upload.
    Alex
     

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