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Home Forums Observing and Imaging Group My week in dark skies, Brecon Beacon.

This topic contains 61 replies, has 7 voices, and was last updated by  Astrograph 3 years ago.

Viewing 15 posts - 31 through 45 (of 62 total)
  • Author
    Posts
  • #8402

    Sumitra
    Participant
    Topics: 21
    Replies: 233

    Sure thing, I’m on it 🙂

    YAY!!

    #8414

    Brian Blake
    Participant
    Topics: 187
    Replies: 409

    Want to talk about New equipment curse. I was at my friends house yesterday helping him set up his new telescope and I tripped and fell down some steps and cracked my ribs.

    #8418

    Tej
    Participant
    Topics: 36
    Replies: 589

    Oh no, Brian are you OK? Well no of course you’re not but hope you heal up quickly, man.  I’m sorry for your mishap 🙁

     

     

    Andy, at this rate we’re not going to last long in this committee, with my relentless equipment purchasing jinxes and your blasphemous jokes (thought it was funny myself…oh no, I shouldn’t have said that)…

    #8419

    Mike Meynell
    Moderator
    Topics: 119
    Replies: 749

    Don’t worry Tej… I’m also the blame… I’ve got “new” equipment as well… albeit a secondhand Skywatcher Esprit 80ED and a secondhand Astrotrac!

    Sorry to read about your mishap, Brian. I hope it heals up soon.

    #8420

    Brian Blake
    Participant
    Topics: 187
    Replies: 409

    I will still be at the History group.

    #8422

    Christina Chester
    Participant
    Topics: 17
    Replies: 193

    The Astrophotography for Beginners course definitely sounds like a really great course!

    Thanks for the detailed reply, Tej – much appreciated. I’m REALLY happy to hear that I can get going with what I already have. Honestly, didn’t think I could do anything deep sky without lots of really expensive tracking equipment! The first link you’ve shared is probably about as good as it’s gonna get (don’t know why I haven’t just stepped outside and given this a go)… And this was taken without a ‘scope?! I’m excited to give this a go. Wonder what it’ll look like with my 5″ reflector… I imagine, not that much better and no where near as your amazing close-up photo but if it’s possible, then that’s certainly something!

    The best astrophoto I’ve achieved so far, is a 4 pane mosaic of the Moon:

     

     

    Posting a link from Twitter – hope that worked 🙂 Had to create a mosaic because the T adaptor I bought is a 2x Barlow so I was zoomed in too closely to get it in one hit. I know, there’s no pleasing me – too close, too far… I want to try this again with staking next time. I’m not happy with the quality of that photo. Not sure if stacking will improve the quality or if I just need better equipment. See, I’ve already made headway on that downward purchasing spiral… Poor Brian – hope you mend up soon!

     

    #8423

    Tej
    Participant
    Topics: 36
    Replies: 589

    The Astrophotography for Beginners course definitely sounds like a really great course! Thanks for the detailed reply, Tej – much appreciated. I’m REALLY happy to hear that I can get going with what I already have. Honestly, didn’t think I could do anything deep sky without lots of really expensive tracking equipment! The first link you’ve shared is probably about as good as it’s gonna get (don’t know why I haven’t just stepped outside and given this a go)… And this was taken without a ‘scope?! I’m excited to give this a go. Wonder what it’ll look like with my 5″ reflector… I imagine, not that much better and no where near as your amazing close-up photo but if it’s possible, then that’s certainly something! The best astrophoto I’ve achieved so far, is a 4 pane mosaic of the Moon: <iframe id=”twitter-widget-0″ class=”twitter-tweet twitter-tweet-rendered” style=”display: block; max-width: 99%; min-width: 220px; padding: 0px; border-top-left-radius: 5px; border-top-right-radius: 5px; border-bottom-right-radius: 5px; border-bottom-left-radius: 5px; margin: 10px 0px; border-color: #eeeeee #dddddd #bbbbbb; border-width: 1px; border-style: solid; box-shadow: rgba(0, 0, 0, 0.14902) 0px 1px 3px; position: static; visibility: visible; width: 500px;” title=”Embedded Tweet” height=”700″ frameborder=”0″ scrolling=”no”></iframe><script src=”//platform.twitter.com/widgets.js” async=”” type=”mce-no/type” charset=”utf-8″></script>Posting a link from Twitter – hope that worked :) Had to create a mosaic because the T adaptor I bought is a 2x Barlow so I was zoomed in too closely to get it in one hit. I know, there’s no pleasing me – too close, too far… I want to try this again with staking next time. I’m not happy with the quality of that photo. Not sure if stacking will improve the quality or if I just need better equipment. See, I’ve already made headway on that downward purchasing spiral… Poor Brian – hope you mend up soon!

     

    Bloody hell, Christina, that’s setting a high bar for a beginner’s attempt!  Great image.  A mosaic, I’ve never even done a mosaic so you gotta teach us that!  Since you clearly have the patience to do a mosaic, you sure got what it takes to enjoy being an astrophotographer and you sound really hungry.   There is a whole playground open for you with the gear you have to enjoy all types of astrophotography.   So you have started with Lunar photography, sweet.  Its what I started with too.  Then I moved on to Jupiter and the Sun (using a white light filter).  Its all within your reach right now with the gear you have.  You dont have to spend a penny more to capture Jupiter and its moons, Mars, Saturn and of course the moon.   With just your DSLR and camera tripod, you can also get started with taking pictures of the deep sky too (albeit wide angle view) and there is a useful exposure guide table for non tracking astrophotography somewhere on this website, written by our chairman himself, Malcolm.  I’ll try find it.   In terms of deep sky photography with a telescope, its quite a different ball game as you guessed but absolultely within your reach with what you have, just a little learning curve needed…well an endless learning curve actually, lol.

     

    However, there are two inexpensive and imho essential items that I suggest you purchase to bring out the best in your telescope for both visual and imaging of planets and deep space.

     

    The first is a bahtinov mask for achieving ultimate focus, this will cost about £16-£17 for the scope you have.  I think its an absolute must have for both visual and imaging.  This clever mask, which you mount in front of the object lens of your reflector, creates a diffraction pattern through your eyepiece or camera view screen, when the scope is pointed at a bright star.  You basically adjust the telescope focus until the diffraction lines are equidistant.  You just do this at the beginning of your session then remove the mask.  Its so elegant and lo-tech yet ensures your viewing through eyepiece or imaging is at its sharpest definition.  I am sure you experience frustration in focussing your telescope when viewing an object through the constant air turbulences.  Its so hard to know if you got focus or not but a bahtinov mask conquers that uncertainty.  A must have…I said that already, haven’t I?

     

    The second item, I think you will need is a normal t-adaptor, as the one you have is combined with your barlow but like you said, you would want a wider field of view for some of your moon (or solar) imaging.  But that’s not actually the main reason you will need it.  You will need it for deep space imaging.  Never use a barlow for deep space because the barlow reduces your light capture.  You want every single light photon!  A T adaptor cost about £17.

     

    The one big issue for all of us Londoners, is light pollution but its only a problem for deep space imaging.  For planetary, no issue.  It is why for over a year and a half I have only being enjoying planetary imaging.  But actually if I had made more effort I could have done deep space even in London, however results would have always been mediocre compared to going to dark sky locations.

     

    Sho whatch you prepared to do ?  🙂    Still cant get over with that moon mosaic you done, well done with that, love it.  What mount do you have, btw? Is it manual, motorized, equatorial?  And also can I know which DSLR you have?

    • This reply was modified 3 years ago by  Tej.
    #8429

    Tej
    Participant
    Topics: 36
    Replies: 589

    Right, Sumitra, Mike and anyone interested in Mike’s controversial theory, I have done a preliminary comparison test of stacking my Andromeda frames with calibration and without calibration.

    So Mike’s hypothesis is that we may not need Dark and Bias calibration frames when stacking with DSS because DSS should be able to reduce noise intrinsically when stacking the light frames, particularly when there is a slight drift in movement through the frames. At least that’s my interpretation. And boy do I hope to prove it true because taking dark frames steals our valuable clear skies time and they have to be taken at the same time as the light frames to be most effective.

    First stage, stacking. For both calibrated and non calibrated stackings, I have kept to the same DSS settings.

    18 frames were stacked then load into into photoshop as 16 bit Tiffs.

    First thing I needed to do was crop the image which contained a dark border. So we get this:

    Light frames stacking without calibration:

    Light frames stacking with calibration (5 dark frames + 30 Bias frames):

    Although there is a shocking beauty and the beast comparison here, it says nothing for Mike’s hypothesis yet because the uncalibrated stacked file simply needs an RGB levelling out. Although notice DSS produces not just a more more aligned output but also an already reasonably stretched histogram. So more processing work is need on the uncalibrated file to start with.

    So next I apply a first level of stretch to each image. For the uncalibrated frames images, I needed to work on each RGB channel seperately as they were not aligned. I zoom both images into a part of the galaxy to show the noise level comparison.

    Light frames stacking without calibration:

    Light frames stacking with calibration (5 dark frames + 30 Bias frames):

    And here I hit a big problem with the uncalibrated frames image. Notice the histogram is severely fragmented and this reflects in the jarring gradients in the image. Whereby the calibrated frames image show a solid histogram with smoother gradients and also a degree of noise.

    Just for the sake of it. I will add a subtle curve.

    Light frames stacking without calibration:

    Light frames stacking with calibration (5 dark frames + 30 Bias frames):

    But whats going going on here? I cant actually proceed with processing the uncalibrated frames stack as it looks absolute rubbish. In fact each individual frames look ten times better than the stacked file!

    So I then stacked fewer frames, picking the best rated ones. Carried out the same process as above and still came up with the same fragmented histogram and jarring gradients.

    So does this disproves Mike’s theory? No, I dont think so. It certainly shows more post processing is needed. As horrid as the above comparisons look, there could be the possibility that DSS cannot actually deal properly with stacking uncalibrated frames.

    OR, quite possibly, there are certain stacking parameters I need to change for when stacking light frames without calibration frames. However, DSS is supposed to automatically recommend settings appropriate to the quality of stacking. In this case, DSS did not recommend any different setting changes with or without stacking frames. Could it perhaps be that I am not properly stretching the histogram of the uncalibrated frames image?

    So what’s the next step? I think I have to assume that DSS cannot be used for stacking without dark and bias frames for now (even if not true). SO I will now try use a different stacking program. I will choose the trial period version of Nebulosity because this is what Mike uses and so Mike, you can advise me on any settings needed to stack. I registered a trial period before I went to Wales to try it out but haven’t yet, so here is an incentive!

    So no conclusions drawn yet, the experiment continues 🙂

    • This reply was modified 3 years ago by  Tej.
    • This reply was modified 3 years ago by  Tej.
    • This reply was modified 3 years ago by  Tej.
    #8433

    Mike Meynell
    Moderator
    Topics: 119
    Replies: 749

    That’s bizarre, Tej.

    What stacking method are use using for the light frames? Is it the simple “average” method, or are you using one of the more complex options?

    #8434

    Tej
    Participant
    Topics: 36
    Replies: 589

    Complex? I stay well away from anything to do with complex ;)…I go with the recommendations as per this DSS settings screen which I used for both types of stacking

    I’ll have a look at other settings and let you know…

    #8435

    Tej
    Participant
    Topics: 36
    Replies: 589

    Perhaps I’ll change to Auto-adaptive weighted Average combination method?

    #8436

    Mike Meynell
    Moderator
    Topics: 119
    Replies: 749

    Yes, try the weighted average method and see what happens.

    #8437

    Tej
    Participant
    Topics: 36
    Replies: 589

    ….and Stacking parameters are set to “standard” mode (in Result tab)

    #8438

    Mike Meynell
    Moderator
    Topics: 119
    Replies: 749

    Whilst Tej continues his experiment as a result of my controversial comment, I think I should clarify my position on this, lest people get the idea that I’m against all calibration of images.

    A quick search on any astronomy forum will tell you that there is a fair amount of controversy on this subject!

    My issue with the adherents for calibration is that it is the quickest way of putting a beginner off the topic of astrophotography. Even experienced photographers often don’t understand what a dark, bias or flat frame is… and don’t really understand why they are applying them to their image (or “light”) frames. For beginners, it just causes total confusion in my experience.

    So, I’m not dismissing the use of calibration entirely, I’m just saying that you can often produce exceptional results without using calibration. Sure, calibration can improve your image… but sometimes the results are barely noticeable.

    I’ve already pointed out that it shouldn’t be necessary to produce bias frames, as the information is already in your dark frames. The problem with dark frames has already been covered, but you also need to remember that darks can also ADD noise to the image, so they are not a panacea. To avoid this, I’d say you need at least the same number of darks as lights, averaged together. Otherwise you run the risk of increasing noise in the image. This is a pain in the proverbials, frankly, as you are reducing the amount of time available for collecting your light frames.

    If you are just starting out in astrophotography, I’m not sure I’d bother with calibration. Sure, as you get more experienced, give it a go, but don’t expect it to suddenly give you the most amazing images. I suspect the improvement in image quality will be marginal at best, and may sometimes prove detrimental.

    For the perfectionists… carry on calibrating! 😉

    #8441

    Tej
    Participant
    Topics: 36
    Replies: 589

    I’ve tried toggling all sorts of settings now and I get the same fundamental issue of fragmentation.

    And with so many different stacking otpions changed, I thought I try another stacking with calibration frames and they stacked nicely with a solid spread histogram. I then went onto another PC and tried stacking on that, again same fracture histogram result.

    I have also tried another set of andromeda images at iso 3200 without the calibration frames. These actually stacked a little better but then the fractured histogram reared its ugly head again. If I was a beginner (which actually I am) and had not taken any dark frames, I would have been rather dejected with this given that I had captured the galaxy with good focus and and very steady tracking…wait, could the tracking be too good!?! The same stars appear at the edges from beginning to final frame.

    I am given up with DSS in terms of stacking without calibration frames…its not serving this experiment well. Unless, you can think of something else, Mike?

    I’d like to try Nebulosity anyway. I will use DSS one more time to do a trial stacking of using just dark frames without the Bias frames to see if Bias frames are unnecessary and even possibly destructive as per Mike’s theory.

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