Thursday, March 14, 2024
Follow-up to the Imaging Vesta Challenge, March 2024
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| Black and White printable map for locating Vesta at s asimilar scale to the images. Elnath and zeta Tau (Tianguan) are fairly obvious and Vesta is near 121 Tau. Click to embiggen | Photorealistic map for locating Vesta (and in conjunction with the printable map). Elnath and zeta Tau (Tianguan) are fairly obvious and Vesta is near 121 Tau. Click to embiggen. |
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| Stack of 30x 1 second exposures at ISO 3200 with my canon IXUS "point and shoot" on 8 March. Click to embiggen. | Labelled Stack of 30x 1 second exposures at ISO 3200 with my canon IXUS "point and shoot" on 8 March. Click to embiggen. |
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| Stack of 10x 4 second exposures at ISO 3200 with my Samsung S24 on 8 March. Click to embiggen. | Labelled stack of 10x 4 second expsures at ISO 3200 with my Samsung S24 on 8 March. Click to embiggen. |
So how did my asteroid 4 Vesta imaging challenge go? Remember my original attempt didn't go too well, despite my confidence.
I had a second opportunity on the 8th. The sky clarity was better, I could actually see Tianguan (zeta tau) and Elnath on the back of the camera/phone screen in test shots (there was a lot of groobling around on the ground setting up the shots and several test exposures to get the right patch zoomed in. My Knees do not like me as I did this on the gravel bike path near the beach.
But eventually I got Tianguan (zeta tau) and Elnath framed at a good zoom level (don't ask me what the Zoom is, the Canon IXUS just gives a zoom bar and the Samsung S24 give a zoom level but I forgot to record it. Both the IXUS and Samsung were on a tripod (I have a special adapter to pones for my tripod).
For the point and shoot IXUS I took 30 x 1 second frames at ISO 3200 (f/5.6), as the IXUS doesn't take exposures longer than 1 second (well it does, but defaults to ISO 50!). I traded noise for sensitivity. I also took a dark frame (exposure exactly the same as the main images but with the lens blocked to account for noise. The frames were then stacked in Deep Sky Stacker, the stacked output saved (a TIFF file), then exposure adjusted in The GIMP and the TIFF converted to JPG.
Unlike last time 4 Vesta was clearly (if faintly visible). You should embiggen the images above to see Vesta clearly.
For the Samsung S24 I took 10 x 4 second frames at ISO 3200, f/3.4no dark frame though. The frames were then processed as for the IXUS (stacked in Deepsky Stacker, the stacked output saved (a TIFF file), then exposure adjusted in The GIMP and the TIFF converted to JPG). The result is much better than the single 10 second exposure.
The Samsung S24 is cheating though, few cameras/phones have a 200 megapixel camera. They will be closer to the 20 megapixel IXUS. But the point is that even with an ordinary camera phone and stacking you can take effective astrophotos down to at least magnitude 8. This opens up a world of sky imaging you didn't think you could access with simple equipment.
How did others go, Well Brendan got Vesta on the 9th,
Vesta is seen faintly above121 tau and has clearly moved since my images on the 8th.
If anyone else has images and wants to submit them, let me know.
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| Single 10 second second exposure at ISO 3200 with my Samsung S24 on 3 March, Vesta is just visible. | Labelled stack of 10x 4 second expsures at ISO 3200 with my Samsung S24 on 8 March. Click to embiggen. |
In these images from 3 and 8 mrach you can clearly see the movement of Vesta.
Labels: 4 Vesta, Asteroid, astrophotography, gimp
Monday, August 06, 2018
Animations of the July 28 Lunar eclipse (2018)
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| Entire sequence of the eclipse stacked and aligned in GIMP, starting every 5 minutes until totality and then every 10 minutes until the Moon finally disappeared behind the roof tops (4:06 am.-6:23 am) Sadly the later stages are made rubbish by whatever compression GIMP uses, but you can see the beginning of the glow as maximum eclipse passes (totality ended at 6:44 am; click to embiggen). | Inital sequence of the eclipse up until the start of totality stacked and aligned in ImageJ, starting every 5 minutes until totality. I didn't do the full sequence as aligning moon images in ImageJ is a right pain, and they tend to get out of sequence. but the quality of the fully eclipsed images is much higher. |
Here, as promised, are my animations of the total lunar eclipse of July 28. Because the motor drive on the telescope decided to stop working, I had to manually drive the scope, and the images were not aligned, so I had to align the images by hand. This is a pain in both GIMP and ImageJ (even though there are tools in both to do it they each have their own limitations.
But in the end it work out okay, mostly. not too happy with the way GIMP made the eclipsed images low res, but it does give you a feel for what it was like.
Labels: animation, astrophotography, eclipse, gimp, imageJ, Moon
Sunday, June 10, 2012
Images from My Transit of Venus, June 6 2012
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| My first image of Venus at 10:26 am ACST when the clouds had broken. | Near mid transit at 11:04 am. The varying colours are due to the cameras auto exposure function, and its lag when clouds come over. |
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| After a cloud interlude, Venus approaches the Sun's limb | Just before 3rd contact at 1:52 pm ACST |
I had great plans for the Transit of Venus on June 6 2012, the last until 2117. I had made a binocular projection system, I had my 4" Newtonian telescope with a glass aperture solar filter, a home-made Baader filter for my 8" Newtonian telescope and a mini Baader filter for my Olympus camera.Wednesday dawned cloudy. Actually, when I first woke up the sky was mostly clear, but huge slabs of cloud moved over where the Sun would be shortly before Sunrise, ending any hope I had of seeing first and second contact.
This was the pattern for the day, large parts of the sky would be sparkly blue, except where the Sun was. Due to the weather I made a decision to only use the binocular projection system and my 4" Newtonian scope, as these systems could be moved around a lot more quickly than the homogeneously heavy 8". Also, although I have a time drive on the 8", it drifts slowly. With brief patches of blue coming over the Sun at short, widely spaced intervals, the time to realign the scope would be too long to catch the breaks. So I stuck with the simpler systems.
An added complication was that SmallestOne was sick and had to stay home too. He wasn't THAT sick, well enough to watch TV and play computer games, but I still had to keep an eye on him and give him his medications at the prescribed times. So I divided my time between moaning at the clouds, looking after SmallestOne, watching the live webcasts and rushing out when gaps in the cloud came up.
I had a great Transit. I took heaps of shots through the 4" scope. Most were useless, with cloud coming over just as I was imaging, or the scope shaking with the wind. Getting the focus right was a pain too. But I could watch the progress of the transit with the binocular projection system easily while I fiddled with the camera.Some people came over and I showed them the transit with the projection system (I had to move quickly to stop one person trying to look through the eyepiece rather than at the card the image was projected on. Even SmallestOne came out and had a look (he wasn't impressed). Compare this transit with my Transit experience in 2004.
Even though I thought I had carefully placed my scope, just as third contact was coming up, the Sun went behind a tree. So I rapidly moved the scope and binoculars, and hurriedly realigned and refocused in time to see Venus approach the Sun's limb.
And the clouds came over again.
Nonetheless, I was able to get sufficient shots to see third contact and just before fouth contact (I though I had 4th contact but I was fooled by the low magnification image). I have made the final series of images into the animation below. It's a bit jerky as at lot of frames were unusable due to cloud. The weird tiny black speckles are due to the GIF to AVI translation. Images taken using infinity to infinity imaging a Canon IXUS and a 4" reflector with aperture filter and 25 mm eye piece, the camera was held in place by a commercial adapter (see image of the scope above).
Animation of third and fourth contact. Images were imported into GIMP as layers, aligned using the difference function and manual alignment, the cropped, exported as an animated GIF, then converted to AVI with ImageJ.
Reflecting after it was all over, what was really good was the degree to which the astronomical community, both amateur and professional, put a lot of time into making sure the general public got to experience the transit, either by making their won projection systems, public outreach events or webcast. As well as thoroughly enjoying my own experience, I'm glad I could help in some small way to let others experience it.
Labels: animation, astrophotography, gimp, imageJ, transit, Venus
Wednesday, March 02, 2011
Using Iridium Flares for Parallax Measurements (part 2)
Overlay of two separate flares simultaneously at a) Largs North, SA and b) Blackwood SA, images overlaid using The GIMP. My image was taken with a Canon IXUS, 400 ASA, 15 second exposure. You may need to click on the image to embiggen and see the reference stars. Back in October I posted about an Iridium flare captured by Dean Male and myself. From those images I tried to calculate the height of the Iridium satellite using parallax. The figure came out too high, but not too bad for measurements done with pencil marks on a bit of paper.
So we decided to try again. After a couple of false starts (curse you weather) Dean and I finally got another good shot of an iridium flare last night (March 1).It helped that from my vantage point, it was a -8 magnitude flare, which was stunning, the brightest flare I've even seen (Dean only saw magnitude -3, to put this in perspective, Venus is magnitude -4)
As for last time, I measured the distance between the two flares and reference stars (6, 9 and 12 Hydrae respectively). I measured the distances using ImageJ (and calibrating the scale of the images against the known angular separations of 6, 9 and 12 Hydrae). This is a bit more accurate than the pencil mark on paper. As before, I used the formula used for Lunar parallax:
Knowing that Dean and I were 12.5 Km apart, I calculated a distance of 961 Km, it should be 801 Km (Iridium 65 was 791 km vertically above the earth, but as it was offset from us, the actual path length is longer).
So, better than the first attempt, but still well outside the 3% error achieved for measuring the distance of the Moon using simple photography. I've been racking my brains as to why I'm not getting better accuracy. The only things I can think of are:
1) Dean and I aren't really 12.5 Km apart but are something more like 10.5 due to triangulation effects (but, I can't make the maths work with the Cal Sky data)
2) The fact that we are measuring the flares a substantial distance below the zenith, which might mess up the assumptions for the equation but I still think the effect would be small.
3) Altitude, I'm at sea level, Dean is up higher (nah, that night compensate for being below the Zenith).
I'm stumped at the moment. Any ideas?
UPDATE: Having thought about the geometry for a while, I realised I was measuring the distance angle perpendicular to the flare, instead of North-South (or East -West), so the measured angle didn't correspond to the geometry of the viewing.
When I did this, I got 787 Km, which is within 1.8% of the actual distance (801 Km).
So YAAYYYY!!! I spent a lot of time trying to work out how to visualise the angles to draw a diagram of the situation, and this made me realise I was using the wrong measurements.
Labels: gimp, imageJ, iridium flares, Satellite
Saturday, February 19, 2011
The Tarantula Nebula (and FITS Liberator)
Left Image: Tarantula Nebula imaged using GRAS 14 instrument at Global Rent a Scope with 3 x 120 sec Red filter FITS images, 3 x 120 sec Green filter FITS images and 3 x 120 sec Blue filter FITS images. Each series of individual filter runs stacked using in Image J using Z projection of maximum intensity, then stacked and assembled into a RGB composite using ImageJ. Right Image: Single 120 sec RGB filter FITS images stretched using FITS liberator and ArcSinh(x) stretch. Stretched files stacked and assembled into a RGB composite using ImageJ. These are smaller frames of the nebula cropped form the whole image. You really, really need to click on these images and embiggen them (and compare to this APOD image which is 31 hours of exposure).
As people know, I'm a fan of low cost astroimaging. For GRAS remote telescope images, my workhorse is the freeware ImageJ. This works pretty well, especially for stacking and aligning images. However, astronomical images can have a large dynamic range from the very faint to the almost overexposed. How to bring out faint structure without turning the bright sections into glaring blobs.
This is where FITSLiberator comes in, it's a freeware app (also there are photoshop plugins), which makes it very easy to adjust the dynamic range of your images for later assembly in other image processing programs (You can do something similar in ImageJ but it's not as easy). As you can see above, with FITS liberator I was able to adjust the dynamic range of my Tarantula Nebula images to almost match the brightness of the multi-stacked images, without the central regions getting overexposed or the background being over-coloured.
Obviously my Tarantula Nebula won't win the astrophotography contest, and I still have a lot to learn, but I'm going to get a lot more out of my images now.
The FITS Liberator website comes with links to a whole range of Hubble raw images, and step by step instructions so you can create your own version of classic Hubble pictures. The PDF user manual is here.
Whole frame of the Trantual nebula and bits of the Large Magelanic cloud taken with GRAS-14. Click to embiggen (warning 2 meg of image)Labels: astrophotography, FITSLiberator, gimp, Global Rent-a-Scope
Saturday, October 16, 2010
Comet 103P/Hartley near NGC 1528
Comet 103P Hartley mosaic showing the nebula NGC 1491 , open cluster King 7, and open clusters NGC 1528 , 1513 and 1545 . This was shot from Global Rent a Scope GRAS 14 (stack of 5 black and white images at 60 seconds each for top image and one 60 second image for the bottom image with the comet). You, really, really need to click to embiggen (it's worth it).Yes, I deliberately made this mosaic, really I did. I didn't mess up my imaging co-ordinates and take 6 images of a completely comet free area before realizing my mistake, no siree.
If you want to see how it is really done, this stunning mosaic from Rolando Ligustri is the way to go.
Chart showing area where images were taken, the field of view of the G14 imager is shown as the large rectangle at the bottom.The individual FIT images were stacked in Image J using Max Z projection, saved as half scale png's then assembled in the Gimp using layers and difference features.
Labels: astrophotography, comets, gimp, imageJ
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