Your smaller camera does not have to worry as much since the angular FOV is smaller. If the spikes are present with skewed rays but not with centered rays, I would look really closely at the objective lens surroundings including the dew shield (which you can also experiment with by retracting it fully). Speaking of skewed rays, try the image with the bright star perfectly centered. You might check yours and look to see if there is any imperfection (even a shiny scratch) all around the aperture. I don't know what the retaining ring of your Askar objective is, but on my smaller Askar 300, the retaining ring has a notch for the lens spanner, and it encroaches dangerously to making the aperture not perfectly circular for a skewed ray. Look for anything that is not perfectly smooth. Since the diffraction spikes are nearly horizontal, the imperfection is in the vertical direction (consquence of the 2D Fourier Transform). Chromatic Aberration, as far as people I checked with told me, there should be no chromatic aberration with the SharpStar 61 and the reducer/flattener, so Im wondering if it. Ive never seen such thing for a refractor, I dont really know what could cause this. If they do, the problem is somewhere on the OTA end, otherwise it is on the camera end. Reflecting telescopes, like NASA’s James Webb Space Telescope, produce diffraction spikes when they are used to image bright objects like stars. These weird diffraction spikes, which are more visible to brighter stars. You can also test for sure by rotating the camera angle and see if the spikes rotates. Notice that the most horizontal spike is angled from the black line.įrom this, I suspect that the spikes are not sensor related. Then you won't be able to get rid of the spikes like Andrea. 2) The string trick, or better yet, a 3D printed set of vanes to put over your objective. The black line is aligned to graphical horizon. rhedden: If you absolutely must have spikes on your refractor or SCT images, there are three ways: 1) StarSpikesPro, which costs 36. Equally important in a choice of telescope type is the focal length and the resulting field of view. In summary: Refractors generally have the edge over reflectors for a quality image, both from the standpoint of lens/mirror quality and precision optical mountings, and lack of central obscurations. That’s why you have to use a star to set up the focus.Erriegraven these horizontal spikes when nothing is in the lightpath?īTW, I think those spikes are not perfectly horizontal. Refractors don't suffer from this problem. Unfortunately, in my excitement I then forgot to take the mask off before taking some trial Moon exposures – I really couldn’t understand why they were darker, and looked out of focus! All the sharp endes of craters etc were being diffracted into a mess. … and here’s an image that’s not in focus: Here’s the image of a star in focus (pretty well): Because the central spike is on one half of the aperture, it works like the famous Hartmann focus test as you move through the focus position, the central spike shifts sideways between the other two which are crossed. The diffraction spike pattern from a bright star using a Bahtinov mask. A simple tool like this can help you capture sharper astrophotography images when used properly. The mask works by generating diffraction spikes perpendicular to the edges a brighter spike (larger area), plus two slightly fainter spikes at 30 degrees offset each way. The Bahtinov mask shown below is a popular choice, as it covers a wide range of entry-level refractor telescopes in the 65-100mm diameter range. The tube is big enough to pop loosely over the end of the refractor. This was then mounted on the end of an old cardboard container: Took this image of M42 (3-inch refractor) from my. However I tried this setup with a Bahtinov mask, made by printing the grating pattern on transparent film. It’s a better quality if I use more rings, and a smaller field of view with the eyepiece. Now comes with FREE WO patented Diffraction Spikes Bahtinov Mask Cap Zenithstar 73 is a greatly versatile and portable refractor telescope for beginners and. It doesn’t look too bad poor at the edges, as before when using only one ring of extension tubes with the eyepiece for projection. The live view was monitored on a tablet, by using the HDMI output from the camera, and a video capture dongle. This image is what I managed purely by using live view to focus. The Moon was about so I thought it could be a good test. I decided that I wanted to try a Bahtinov mask for focus tests on the 3 inch refractor, after having tried one on a telephoto lens with some success.
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