astrophotography stars not round

This can be caused by your mount not having enough time to settle between exposures. Bianca Andreescu breezes past second French Open hurdle | The Star Please note: For astrophotography enquiries, we recommend contacting the dealer you purchased your product from in the first instance. The tracking unit you are using claims a typical peak-to-peak tracking error of 5 arc-seconds over a five minute period. By adjusting the focus carefully, you will see the central spike move in relation to the fixed X spikes, similar to the image sequence below. Full-frame cameras cannot be corrected perfectly on some scope flatteners/correctors and. does your scope info indicate it is good for full-frame cameras??? If its oscillating between + and corrections youll need to turn down the aggressiveness. creating optical problems. Best cameras for astrophotography: Shoot for the stars | Space All you need to do is check your collimation, the flexure in adaptors and focuser. Well rounded stars give your image a crisp, professional look that we are all aiming for when imaging. The fine focus will typically give you a 10:1 reduction, giving you excellent resolution and precision for finding the exact focal point. konstantinos75 Members 89 105 cheshire, autocollimator, etc., I almost never achieve perfect With less The fine adjustment is usually the smaller outer dial. Or could it be something else? On the basis I switched most of the kit between the 2 photos, I'm assuming it's either mount to camera related, but where to go from there I'm not sure. You may have multiple issues besides spacing. Sometimes stars can have a good shape in one part of the image but they get increasingly distorted away from this spot. The problem with the elongated stars still continues. The focusser looks square to the scope. Brighter stars look even worse. Edited by Kevin_A, 30 October 2020 - 11:08 AM. Fix: Go with threaded connections only, or ensure your camera is (very) securely mounted (compression rings are bad). But by wind.. More ideas appreciated. Some aberrations can be seen during a star test, which is a process in which a bright star is examined out of focus and at high magnification. Go to the Lens Corrections tab. Star Trails - star trails requires much longer exposures and the rotation of the earth. coma corrector in place, a star placed. I use an 8 inch 1000mm F.L. With 14 total picks, the Rams were the busiest team in the league over draft weekend, and added many more players as . Relating to the Collimation and Once aligned, hit the Recalc button. Suggest you show Lights, as stacked images will have averaged out the problems. Use something like ASTAP to do this. A good amount of detail is shown in the nebula, with lots of fine structure and contrast visible. Now take a test shot at your planned exposure length (if you are using a tracking mount, you should, of course, be polar aligned and have tracking enabled). no defocus the star. mirror so that the optical I will say, backfocus is not yet dialed in, according to literature, I should have 55mm backfocus. cell made of something other than glass will often cause it to warp as There are two main types of primary mirrors used in Newtonian telescopes: lower cost spherical mirrors, which form part of a sphere and are supplied with low-budget telescopes, and the more popular parabolic mirrors, which are sculpted into the shape of a parabola. If the target is due south, west or south west I get elongated stars, I do 15 minute subs but the problem is present even on 5 minute test sub. Ensuring you can keep your stars round is key to producing stunning images of the night sky. Taking that little extra time to ensure your image is sharp and focused will reduce the frustration of seeing an otherwise good image ruined. Even small focus adjustments will cause the central spike to shift noticeably. glued to the cell, then you cannot easily rotate them to help rule out The image in the middle was defocused slightly. appear distorted (updated Try 5 for expansion and 2 for feather. Please re-enable javascript to access full functionality. I personally use Maxim and have set up a spreadsheet which I load the log file into to display not only RA/DEC adjustments over the session but also cross reference them against guide star brightness - It's then very easy to spot periodic worm errors or see the guide star wanders if the transparency drops off. Under Defringe, slide the Purple Amount slider to the right until the halo is gone. Increasing the ISO will increase the camera sensors signal gain, making the image brighter, which is ideal for low light images. But there's a possibility I am wrong with this assumption Before opening the mount and adjusting the backlash, do you have any ideas what could be the reason of elongated stars? NOTE: Lasers can Aug. 2016), All images and text Copyright Mike Unfortunately, not all aberrations can be eradicated: some are caused by manufacturing or assembly errors, others are simply a limitation in the telescopes design. Put your coma corrector back in the focuser Scope sat outside for 90 minutes prior to use, to acclimate to temps. below will then help you get close to perfect primary and system Try popping your DSLR on and see if you still get the same star distortion (better to simplify when hunting for issues). I think there were 15 in a plastic package. There is no tool available for checking everything, but you can get expensive software that can tell you if your sensor is tilted and you can use software or masks to see if you are in perfect focus. coma can be checked by a $30 tool and elongated stars are variables that are trial and error based on back spacing. but alasno magic tool for everything. If the elongation appears to be radial (curved) across the whole frame - its PA. Is there some way of sorting this out in the daytime as 5 sec or 120 sec exposures give the same result and the centers are sharp so I not convinced it happens due to tracking issues? Landers Nolley II Works Out With Fifth Team Ahead of 2023 NBA Draft When a star is in perfect focus, the central spike will be positioned exactly between the two X spikes. Of the six we have looked at, chromatic aberration and astigmatism are unlikely to be fixable at home. From An astrophotography image with pin-sharp stars ensures that you maximise the hard-to-capture detail of faint deep-sky objects, such as nebulae and galaxies. Tipping is more difficult to solve since it can be caused by a number of issues. You are using the equivalent of a 600mm lens (200mm times 1.5 (crop factor) times 2 (doubler)). A second pair of Ontario eyes might not help here: to me the stars are either very fine in the center or fine enough that if you can achieve the same roundness across the field, edge to edge, you will probably be very satisfied :-) Regardless, your path to happiness (in the short term ;-) is to get round stars near to the edges. (Or perhaps I mistakenly interpreted the advice, but I don't think so.). The most important thing is to respect the BF. Catadioptric scopes like Schmidt-Cassegrains, Maksutov-Cassegrains or Ritchey-Chrtiens require a baffle tube to prevent light from the front of the telescope falling directly onto the focal plane before reflection from the primary mirror and this can cause vignetting. Before hitting GO on your exposure plan, it is worth taking a few final test shots to double-check that you are completely happy with your focus. To visualise this, imagine that you are looking at the side of the light cone as it leaves the telescope lens or is reflected from the telescopes mirror on its way to the focal plane. Given that all the stars appear to be radiating away from the center my first inclination is that there is a backspacing issue, in this case the camera is ever so slightly too far from the corrector, is there a way you can move the camera closer by 0.5-1mm? I purchased the scope new in fall 2019, used it visually and have been pleased with performance, this is the first time I've attempted to set it up for astrophotography. I also had problems with my corrector. Moving to an off axis guider will eliminate this. To do this, pan to your intended deep-sky target and frame up your shot. During the astrophotography session, the telescope was pointing to the East and there's was no problem noticed with PHD guiding. Thing to do is get an assortment of spacers, available through Baader and I think I also saw the package on Amazon from 0.6 to 1.3mm. I know the Astrotack is perfectly aligned to the polar star as the stars in the middle of the picture are still round even with 3 mins exposure. Strangely the pillar moves a little from the vertical after a few days and needs resetting. where a star will appear round even with no coma corrector being used) This can be especially true if you are dithering. These initial focus positions will help you avoid a situation where you are too far out of focus that stars become difficult to view on the live view screen. Filters, particularly narrowband filters like this 12nm H-alpha filter, will make focusing more challenging. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. Telescope focusers have a focusing knob that you turn to adjust the focus. As you can see from previous MaximDL guiding graph for test 3 with VC200L I have these values, After performing star drift method for polar alignment, Ihave managed to reduce these values to. How to Fix Oblong Stars in your Astrophotography using Photoshop I did not mention this - but No wind last night. Astrophotography for Beginners - A Guide to Astrophotography A small pop-up window will appear, and in the available fields, you should enter your setup focal length, objective diameter and camera pixel size. ChrisIS To access the Bahtinov Aid in APT, select the Tools tab on the right-hand side of the main display and select it from the list. Difficult to tell if its PA, we would need to see a whole, uncropped image. Do you have any idea what is the reason that causes the stars to be elongated in some frames? This is an evidence that my problem with elongated stars is caused by wind. The autoguiding is done through the ST-237 guide chip of SBIG ST2000XM. Any comment on these M51 images will be welcomed. When light from a star passes through a grating of regularly spaced lines, it creates a very pronounced diffraction spike perpendicular to the direction of the grating lines. As the knob is adjusted, the telescopes optical tube assembly will move in or out, physically changing the length of the telescope and with it the distance from the objective lens to the eyepiece or camera sensor. 2) What is the diameter of your main objective lens tube? After checking the generated fits, I see in some frames the stars look ok - pretty round - while in some other frames the stars look elongated. With same setup described above I slewed the telescope to Zenith and captured a sequence of 10 minutes exposures of M51. I see the same shape stars everywhere I look, center or all corners. The technical storage or access is necessary for the legitimate purpose of storing preferences that are not requested by the subscriber or user. I'm waiting on delivery of a zero-length t-adapter to test reduced spacing, but I can say with confidence that I don't know what is going on here. Sign up for a new account in our community. konstantinos75 About does this happen often. Astrophotography: Star Shaping in Photoshop, with an - YouTube including the edge support of the mirror. early in the evening, understand that your mirror will They are generally worse out on the edges. your head. I took from a very experienced CN'er advice that states that if the stars are "radiating away" from the center that one should add distance, not take it away. Given that stars are still awfully small at 600mm (35mm equivalent), 2-3 pixels represents considerable distortion. Right now it's ~ 53.5. It could be many other things though..a gust of wind for example. After that, I pointed the telescope low to the East and took two exposures of 15 and 25 minutes of Deneb. By clicking Post Your Answer, you agree to our terms of service and acknowledge that you have read and understand our privacy policy and code of conduct. For outer tube diameters from 85mm-120mmFor outer tube diameters from 105mm-150mmFor outer tube diameters from 125mm-180mmFor outer tube diameters from 195mm-240mmFor outer tube diameters from 215mm-260mm. coma-free spot in the center of the eyepiece's field, and then the I would capture a test field with plenty of well-spaced, bright stars. The combination of the three different grating orientations on the Bahtinov mask creates three distinct diffraction spikes. Unfortunately the image posted is a low resolution and on my screen it shows round center stars but with a slight donut effect (slightly darker in the centers) which could be a focusing issue that would amplify the corner issues further than normal. These settings are usually enough to reveal the diffraction spikes if you use a bright star. Not sure how this helps at all fixing the issue here bud? The exception to this is with refractors employing an optical design known as a Petzval, in which there are four lens elements, the front pair correcting chromatic aberration and the rear pair correcting field curvature. The technical storage or access that is used exclusively for anonymous statistical purposes. see HOW the star expands, not This means that with the exception of very long focal length telescopes, they are unable to focus the whole field of view at the same plane. It is particularly noticeable in deep-sky images, where the centre of the field of view can appear markedly brighter than the periphery. One final thing about DSLR lenses is there is often no focus lock. To get the . Learn how your comment data is processed. Check out Astrophotography Tool or APT here. These are as a beginner when you don't have the equipment and are wondering how to get started, or if you are traveling somewhere without all your equipment. A quick and simple tutorial on how to round off oblong stars. If the problems are exactly the same on both scopes then you can rule out collimation as the odds of that are basically zero. If the star you are focusing on is bright enough, you should now see the characteristic diffraction pattern on the live view screen. Once centred and magnified, you can begin to refine the focus. 1 Celestron NexStar 4SE Check Price 2 Celestron Inspire 100AZ View 3 Celestron AstroFi 102 Telescope View 4 Celestron NexStar Evolution 925 Computerised Telescope Check Price 5 Celestron Astro Fi. Ensuring you can keep your stars round is key to producing stunning images of the night sky. The problem must be backlash in the motor gears of HEQ5 mount. Edited by 06AwzIyI, 29 October 2020 - 09:39 AM. Powered by Invision Community. This method will get you very close to the correct focus, so all that is needed from here is confirmation or refinement. The PA is usually very good and the PHD graphs are as flat as a pancake. It is also a good setting if you want to take a test shot to check your focus in more detail. On Canon DSRL cameras, this is done using a wheel adjuster near the shutter button. And they do not usually show as a spike on the side of a circular star. Such a star will show an enlarged Airy disc and close examination on either side of correct focus can reveal much about the quality of the optics by noting the formation of the concentric rings formed in the image. Plan to be outside for several hours. Use the cameras live view to monitor the size of the star. Adjust the focuser to make the star appear as small as possible. This combination of focus sensitivity, accuracy, ease of use and low cost is why the Bahtinov mask is so widely used throughout the astrophotography community. The Williams Optics Zenithstar 73 comes with a Bahtinov Mask integrated into the lens cap. Guide to Astrophotography + 8 PRO Night Sky Tips Again this time the autoguiding was perfect. But sadly, the increase in worldwide light pollution makes it more difficult to. To get better than that, you'd need to either shorten your exposures (by raising your ISO) or move up to a more sophisticated tracking system, perhaps one that uses real-time imaging of the pole star for self-correction (which will not be cheap). Thank you for your analysis about my problem. Keep reading to find out more. bulge that you see when defocusing. another one or two! You may even already know from your eye doctor that you have astigmatism. Both DSLR lenses and telescopes are commonly used for astrophotography, so I will run through some of the features and differences you will likely encounter. Sign up for a new account in our community. Why is Bb8 better than Bc7 in this position? I'm using an Atik one 9.0 camera, and both photos were using a tuned EQ6-GT mount. Autoguiding was performed via ST4 with second chip of SBIG ST2000xm like previous time. rev2023.6.2.43474. As you approach the focal point, you may start to see fainter stars pop into view; this is a good indication you are on the right track. I have tightened everything up with no effect. Best telescopes 2023: To stargaze galaxies, nebulas and more | Space I have been looking into backspacing and from Kevin's charts it could be the camera is too close to the coma reducer, though Baader specify the correct distance and that is what I have used. Lockwood Custom Optics - Why aren't my stars round? Astrophotography filters will also drastically reduce the amount of light that reaches your cameras sensor, particularly narrowband filters. I am fairly new to astrophotography and been at it about 6 months. I have had a bad coma corrector and some correctors just don't work well with some scopes. This one used PHD2. In a refractor, the individual lens elements are held in place within a cradle called a lens cell; in a reflector, the primary mirror is held in place by a series of small clips that hold the mirror in an adjustable carrier. - take 1 sec exposure without guiding; as you can see the stars are round so this excludes problem with collimation of the telescope optics. Oblong stars across the field can be due to poor guiding in one axis. Is there a reason beyond protection from potential corruption to restrict a minister's ability to personally relieve and appoint civil servants?
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