I have had a bad coma corrector and some correctors just don't work well with some scopes. if the primary mirror All you need to do is check your collimation, the flexure in adaptors and focuser. maximum exposure length (seconds) = 400 / focal length (for ~14-16mm) We most often shoot with a 16mm or 14mm lens when we go wide, so from our field tests, this works: ~28 seconds = 400 / 14mm. If you enjoyed this post, please consider subscribing or leaving your feedback in the comments below. Many challenges come with astrophotography, but one of the most critical skills to master is achieving pinpoint star focus in your astrophotography images. Example - last night I started imaging Rosette Nebula, 120 sec exposures of Rosette Nebula, I was using a 2" Antlia ALP-T filter. I'm finding stars are not round. [if you load them into something like DSS and register/compute offsets, the dx and dy columns show this]. You may even already know from your eye doctor that you have astigmatism. I have also taken many pictures trying to exclude the wind factor and other things that might 'shake' the camera. where a star will appear round even with no coma corrector being used) see HOW the star expands, not How to Expose for Perfect Stars PhotographingSpace.com DESCRIBED BELOW, YOU MAYIMPROVE YOUR TELESCOPE'S IMAGES There is no fine focus ability on most DSLR lenses, so adjustment can sometimes be a bit coarse. Now imagine looking down on the light cone from above the telescope. Focus is adjusted using a focusing ring around the lens housing. Here you can see a sequence of M13 images during this session. d750 settings for astro: Astrophotography Talk Forum Forum: Digital Just something like a 10-second exposure, then really critically assess the stars in all corners/edges and the center. Round up of today's best deals ZWO ASI183MC Pro MP CMOS . 1) What is the focal length of your camera lens or telescope? 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. If the image is still faint using these settings, you can increase the exposure length. Credit: Astronomy: Roen Kelly Entering the second week of June, Venus approaches the Beehive Cluster, arriving within 1.1 of these stars on June 12 and standing 0.8 north of M44 on the 13th. Finally, vignetting can be dealt with through calibration with flat frames during post processing this can make a huge difference to your images. The stars are sharp and appear small in the image. By using this site, you agree to our Terms of Use. There must be a million threads here about flattening the field for AP which is what you need to do to get round star in the corners. This will allow you to capture as much light as possible. The image on the right has a more significant defocus applied. How can an accidental cat scratch break skin but not damage clothes? These additional cookies will be set only if you click Accept below. take 1 min and 2 min exposures of Vega; as you can see the stars are elongated in both images. severe coma, stars still appear asymmetric at or near focus, a How to figure out what is wrong with your telescope when How to process Astrophotography Images: Star correction high-quality eyepiece, move the star This is not such a big issue with observing as the eyepiece and the eye itself compensate to a large extent. rather than "Gaudeamus igitur, *dum iuvenes* sumus!"? When using filters, ensure you focus with the filter in place. You will need to make sure that the focusing mask fits correctly over the end of your lens or telescope. Well rounded stars give your image a crisp, professional look that we are all aiming for when imaging. 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. The outer diameter of the telescope tube (not the objective lens) should be measured, and a suitably sized mask chosen to fit over the end. The Elephant Trunk was taken with a 300mm Canon lens, 1.4 converter, using 20x5min Ha, OIII, SI, a skywatcher 50ED guidescope and S. 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. Temperature can have a big effect on this aberration with a telescope, especially a refractor, having no apparent problem until the temperature drops and the various components start to contract. This process typically involves adjusting a focusing ring or a focusing knob. The autoguiding is done through the ST-237 guide chip of SBIG ST2000XM. Also have a look atimage4.JPG, this is the MaximDL graph output, So judging from these test results I have come to the conclusion that my problem can be caused by, (a) flexure by the VC200L focuser since a heavy camera SBIG ST2000xm is connected to this focuser. SCHMIDT CASSEGRAIN AMATEUR ASTROPHOTOGRAPHY= Home I'm not sure the Baader MPCC Mk III is capable of coma correction for full frame. Its common for people to find their stars have little tails. 4658 0 What is Coma Aberration? Powered by Invision Community. Also, it wont be backlash - because in PHD that will manifest itself as a sawtooth pattern in the guiding graph (and 1min is too short a time for backlash to build). If its oscillating between + and corrections youll need to turn down the aggressiveness. I have a flattener/reducer that produces similar stars radiating away from the center, and my understanding was that indicated more spacing was necessary between the flattener and sensor. Problem with elongated stars - Imaging What do the characters on this CCTV lens mean? Any coma issues at all (with a properly adjusted field flattener/coma corrector) should be re-verified by simply verifying collimation is good to start with. If the dealer is unable to assist you, we are more than happy to help. I have offset the mount even more than usual but the problem persists. Save 50% when you subscribe to BBC Sky at Night Magazine today. The Williams Optics Zenithstar 73 comes with a Bahtinov Mask integrated into the lens cap. 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. Now I am confused. In fact, just about everything concerning the SCT is complicated except for its relatively simple design (other than that dratted corrector). Try 5 for expansion and 2 for feather. Edited by PirateMike, 29 October 2020 - 08:48 AM. Thanks all, I will try increasing backfocus when the rain decides it's had enough! This setting is often found on the lens rather than the camera body. Most optical systems dont fully illuminate the field of an eyepiece or the surface of larger camera sensors, resulting in stars of equal magnitude appearing dimmer at the edges of the field than at the centre. For all of the collimation adjustments to move GREATLY PixInsight Tutorial | Put those Stars Back into your Astrophotography Learn how to identify the errors that can occur in your telescopes optics. The inclusion of extra-low dispersion (ED) glass elements can also deliver very good results. Of course trial and error would be definitive. telescope is nearly perfectly collimated. bulge that you see when defocusing. Making statements based on opinion; back them up with references or personal experience. Your stars are mostly round, with a "spike" at 11:30. advice to follow, please put the star in the center of the field of Also have a look atimage2.JPG, this is the PHD lab output after inserting the PHD logs, - start autoguiding, guiding scope is VC200L, guiding camera is SBIG ST2000XM with dual chip ST237, MaximDL is used as a guiding software. By SportsDay Staff. Stars at the 4 corners (not shown) look the same - showing this same flare. My equipment: Vixen VC200L, Skywatcher HEQ5, SBIG ST2000xm. Is there a place where adultery is a crime? Field Flattener\Reducer: ES 3"FFFR507X-00 0.7x field flattener\reducer - this is the ES reducer\flattener designated for this scope. Guide to Astrophotography + 8 PRO Night Sky Tips I rotated the camera 90 degrees with no change. Adjust the focuser to make the star appear as small as possible. The latter may be better carried out by a professional. Now I am suspecting either the focuser or the mirror housing flexingunder its own weight. Lockwood, 2016. 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? Adobe Photoshop's Camera Raw filter. Step 5 Adjust the exposure length to between 10 and 20 seconds. How to Avoid Star Trails by Following the '500 Rule' - PetaPixel I also use Astrotrack without guidance. Copyright 2021 Stargazers Lounge Got any tips you think weve missed? You currently have javascript disabled. It's complicated. Your scope could be centered exactly at the NCP, and if it were then Polaris would not be there. 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. 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. Edited by Kevin_A, 30 October 2020 - 11:05 AM. Step 3 If you use a DSLR lens with an adjustable aperture, you will want to set this to at least f/4.0 or wider. glued to the cell, then you cannot easily rotate them to help rule out Your email address will not be published. What happens if a manifested instant gets blinked? Failure to get this very fine adjustment correctly set at the factory can result in the mirror being slightly deformed resulting in the optics being pinched. Set the balance so it is slightly heavier on the East side. Just as with field curvature, coma becomes worse with shorter focal length telescopes. The Elephant Trunk was taken with a 300mm Canon lens, 1.4 converter, using 20x5min Ha, OIII, SI, a skywatcher 50ED guidescope and SX Lodestar guide camera. I don't know if I am saying anything useful here. Thanks in advance The North America and Pelican Nebula in Cygnus are filled with fine structure and beautiful detail, by Mike Soulby stellardiscovery.com. I'm using an Atik one 9.0 camera, and both photos were using a tuned EQ6-GT mount. There is also a more complex design called an apochromat that is specifically designed to bring all the wavelengths of visible light to the same point of focus, resulting in high-quality images. Step 10 As you adjust the focus, the aim is to make the star as small as possible. astrophotography - Am I experiencing field distortion while astro The technical storage or access that is used exclusively for anonymous statistical purposes. The 2023 NHL draft will be June 28-29 at Bridgestone Arena in Nashville, and the Stars do not have a first-round pick after trading it to New York . It can be a frustrating hobby when adjusted properly isn't perfect! (The vertical field of view of a 600mm lens is 220', and you have 4000 vertical pixels.) This is fairly simple - if the stars in the telescope do not appear to be round, tilt/turn your head. The human brain is very good at recognising when the central spike is positioned precisely between the X spikes; this means your focus can be confirmed very quickly and with a high degree of accuracy. If the stars in the corners are misshapen and look different in each corner you may be experiencing tilt in your optics. Follow the steps below, and you will be able to get excellent sharp stars in your images. We hope these tips can help you get the most out of your setup and lead to some stunning images. condition: If it's Astrophotography can be a photograph of a landscape with the night sky or deep-sky photography. You need to be a member in order to leave a comment. 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. Registered Company in England & Wales - 05948849. Answer? Collimating Your SCT For Best Performance Any comment on these M51 images will be welcomed. A simple adjustment to the amount of time you give your mount between exposures should fix this problem. With 14 total picks, the Rams were the busiest team in the league over draft weekend, and added many more players as . I see the same shape stars everywhere I look, center or all corners. I have started astrophotgraphing. and this is a video of the 40 fits frames where you can see the problem with elongated stars in some frames. However, adding distance made the elongation worse, not better. All corners in your picture show slight elongation with 2 of them showing definite coma. As you adjust the focus of your lens or telescope, the central diffraction spike will move from side to side between the two X shaped diffraction spikes. As example - attached is a 100% zoomed-in (center area) of a single 2 second exposure fits file. More ideas appreciated. ChemiMOS has a market-leading dynamic range with a native full well capacity of over 50k e- and Read More, Our offices will be closed from December 23rd until January 3rd, 2023. The effect can be minimised in scopes that use two glass elements made from different types of glass (historically crown and flint glass). "I don't like it when it is rainy." The Bahtinov mask will reduce the brightness of the star you are trying to focus on as it diffracts and spreads the light from a single point into three diffraction spikes. The problem must be backlash in the motor gears of HEQ5 mount. This ensures a secure fit around your telescope tube, simply find the size that fits your telescope. You may have multiple issues besides spacing. Place your Bahtinov mask over the end of your camera lens or telescope objective. Pan around the image and carefully check that the stars are pin-sharp when viewed at 100% zoom. When a star is in perfect focus, the central spike will be positioned exactly between the two X spikes. Images with beautiful detail in galaxies, great capture of faint outer regions of planetary nebulas and great capture of h-alpha in emission nebulas often simply get 'destroyed' by harsh, clipped, bloated and too prominent stars. Jun 1, 2023 4:45 PM EDT. the coma corrector from your telescope if you are using one, put in a 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. Try some shots without the reducer and see if the stars are any different with regards to the "spike". Chromatic aberration While not being a perfect fix for all problems you may find this removes any issues you are facing. Not only are round stars aesthetically pleasing they are also a sign that you are getting the most out of your set up. On second look I do think your collimation is definitely not great (coma in 2 corners). and even your center stars are a bit off looking (donuts). 2) What is the diameter of your main objective lens tube? Fix: use polarfiner http://myastroimages.com/Polar_FinderScope_by_Jason_Dale/, If the elongation only occurs say, from halfway across the frame and out towards the corners- its a tipped field (this will show in short, and long subs). Fix: Tighten up your whole guiding arrangement stiff as possible. (other Any deformity in the shape of the lens or mirror can result in the focal planes being at slightly different points producing distorted star shapes. he instructions b) For a telescope, you can first focus on a distant street lamp if you are unable to see any stars and are not sure where the focal position is. The Flaming Star Nebula in Auriga has some fascinating structure, by Mike Soulby stellardiscovery.com. No wind blowing. 8:55 PM on Jun 1, 2023 CDT. // All photos: Tony Hallas 2 Go to. The fine focus will typically give you a 10:1 reduction, giving you excellent resolution and precision for finding the exact focal point. Use the magnifier feature on your camera or view the image on your laptop. Sign up for a new account in our community. My primary lense I use is Sigma 70-200mm F2.8 APO with Nikon D7100 and Sigma 2X TC. The technical storage or access is required to create user profiles to send advertising, or to track the user on a website or across several websites for similar marketing purposes. Somehow it often seems as if the stars in an astro image are ignored or overlooked in much of people's workflow. You need to be a member in order to leave a comment. Before you do anything else,determine if you have Placing a filter in the optical train will affect the focus position. One final thing about DSLR lenses is there is often no focus lock. Something like M44 or M67, depending on your FOV. NOTE: Lasers can I'm sure a quick search will provide you with more than enough information. Polar Alignment For Astrophotography | Aligning How-To Guide back to its original orientation, Primary mirror strain-induced Due to the reduced light transmission, short test exposures can be helpful. But by wind.. Hello - I've not yet approached the manufacturer, prior to doing that I'm looking for an opinion on these star shapes Is this something I've misconfigured or perhaps a scope issue? Before we start talking about how to remove or even avoid coma in your astrophotography images, lets first talk about coma aberration. Coma can be removed by the use of a coma corrector. take 2 min, 5 min, 15 min exposure of Vega; as you can see the stars are elongated in all images. Focusing on very faint objects is difficult but can be made easier by having an approach that works for you. Your camera model may differ from the images shown; please refer to your camera user manual if required. 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?