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Found 22 results

  1. Hey, For sale is Baader Rowe Coma Corrector (RCC I) in a perfect condition (used max. 2 times). £90 including delivery in EU. PP preferred. Thanks for looking!
  2. Hi all, yesterday caught a good clear sky, so went out to observe. Had a lot of difficulty setting up the scope... On the first run it didn't want to complete the 3 star align, so I had to do everything again, and fortunately, afterwards it did align... Probably to do with poor PA... I had difficulty the first time aligning well with the polaris... So then I tried M1 (was low, and the photo did not turn out too well, so not posting), M64 and NGC 5033 (not processed yet). M64 came out like this without flats: and with flats: As in the last time, big problems with tracking and coma, apart from the flats problems (really have to get me a flatbox). The galaxy is not too bad, but the edges of the photo show terrible stars... Will have to try more and harder... I'm also thinking that in the end the place where I observed (close to home) is not near as good a place for dark skies, as the place from my last post (with M3, M81/82 etc), which is at an hour's drive... http://stargazerslounge.com/topic/240657-coma-problem/?p=2621703 Any thoughts? Any suggestion would be helpful... Thanks! Gerhard.
  3. hi all, I was just reading up on optical aberrations, and it appeared to me that maybe my pics taken with my Vixen suffer from coma... It looks to me like the stars are all malformed, and maybe this is coma, very common to newtonians... Coma correctors can be a solution, as I gather, but backfocus issues might ruin this, if there is not enough room to focus with a corrector on. Does anybody know if my Vixen R150S can handle a coma corrector with a DSLR attached? or will I not be able to focus anymore, and so would have spent 160 euros in vain? I haven't found info on the backfocus of my scope... Any info would be great!!! Gerhard. ps: also anything you might have to say about my pics would be appreciated! :-)
  4. The Newtonian telescope design is both simple and remarkable. It is capable of producing a perfect image on axis, but off axis, the image quality degrades mainly due to an optical aberration called coma. Modern fast Newtonians and Donsonians of F/5 and below have a surprisingly small diffraction limited spot (just 2mm across in an F/4.5), where the image is not disturbed by coma. The Astro-Tech (also sold under the Altair Astro and GSO brand labels) coma corrector has been designed to cancel out this aberration to give a flat, wide field with high resolution from edge to edge. It is manufactured by Guan Sheng Optical (GSO) and was developed by Astro-Tech from a high quality, modern optical design by Roger Ceragioli My corrector came in a nice box and consists of two parts, the coma corrector itself and a 2" eyepiece adaptor which screw together with a 48mm (2" filter) thread. The eyepiece adaptor has two screws and a brass compression ring and is marked ALTAIR ASTRO 2", Coma Corrector, Made in Taiwan. At least I knew I had the right part, but no other documentation was supplied and I had to search the web for information on how to use it. Unfortunately the corrector is not ready for visual use as supplied, because of inadequate eyepiece spacing. The proper spacing is not critical and a compromise spacing to cover your eyepieces can made up with 2" extender tubes, such Hyperion fine tuning rings or empty 2" filters. You do not need a turntable like that of the Tele Vue Paracorr. With the spacers installed, the assembly which is now about 70mm long just slides into the focuser tube like a barlow. In this arrangement the focal point is moved in by a small distance of about 10mm (see photographs below). The corrector acts as a very slight barlow, enlarging the image by just about 10%. The lenses are nicely coated and reflect pale green. The aluminium housing is cleanly finished in satin black and the combined unit weighs about 350 grams. Once set up properly in a collimated telescope, the corrector works just as you would expect to give a clean, flat image. The view feels quite different, much more like a refractor, with pin point stars from edge to edge, but no chromatic aberration. Objects can be allowed to drift across the view of wide angle eyepieces with little or no visible loss of sharpness. The removal of coma can be clearly demonstrated by doing a star test on and off axis without the corrector installed and then with it. Any loss of contrast due to the extra corrector glass (two doublet lenses) in the light path is undetectable, I think. The coma corrector is now a permanent fixture in my focuser except on occasion when viewing planets with my 200mm Newtonian which now has a motor drive. It seems to me that a coma corrector should be a standard accessory for all fast Newtonian telescopes and particularly for larger Dobsonians with no tracking. This model is an effective, affordable example and I strongly recommend it. The first issue is actually finding one in stock. Supply has been patchy over the years and at the time of writing, it is listed by Astronomics (Astro-Tech brand at $135, including T-mount, but out of stock), Agena (GSO brand at $130, including T-mount, but out of stock), Ian King (Altair Astro brand at £88) and Telescope Service (GSO brand without visual adaptor at 61 Euro). There is then the issue of setting it up properly and most of the remainder of this review is devoted to showing how this can be done, but first there is a little information about Newtonian telescopes and coma. Newtonian telescopes are all designed with a single figured mirror in the shape of a parabola rotated on its axis, a paraboloid. All mirrors of a given focal length are the same shape. If you have a fast mirror, it is easy to to create a slow one of the same focal length, just by blanking off the outer part of the mirror. It is the outer part of the mirror that generates coma, which is zero on axis but which increases linearly the further from the axis you get. At the focal surface, the amount of coma is independent of the mirror focal length so a single corrector will work for any Newtonian. In practice, a perfect corrector is not attainable so the designer will aim to produce the best result he can for a specific F/ ratio, F/4.5 for this model I understand. However, the corrector will give good results for mirrors that are somewhat faster than this and for all slower mirrors. Coma correctors would actually be better called Newtonian correctors, because the designer is looking to produce the smallest attainable spot size for a point source, so will also be looking to reduce the other lesser Newtonian aberrations, field curvature and astigmatism. To do this, he will have in mind a particular focal length, around the longest that is commonly used (so about 2000mm or slightly less), because these aberrations are less in longer telescopes and it is wise not to over correct significantly. Newtonian telescopes are perfect on axis, but coma damages image quality at even a modest distance off axis. At the focal plane, about 1mm off axis, in an uncorrected F/4.5 Newtonian, the image is just at the diffraction limit and the strehl of even a perfect mirror has fallen to 0.8. In a 250mm scope, this gives a coma free, sharp field of about 6 arc minutes across, about 1/5 of the apparent diameter of the moon. For comparison, the field stop of a 9mm orthoscopic eyepiece is about 6mm so only the central 1/3 (1/9 of the area) of the view is free of coma in an F/4.5 scope. Coma increases sharply with the speed of the telescope, at the focal surface inversely with the cube of the F ratio. Collimation is the business of lining up the coma free sweet spot with the centre of the eyepiece axis. The tolerance for collimation is perhaps 1/4 (though some would say 1/6) the size of the sweet spot so that it covers the centre of the eyepiece. So far as I can tell, this tolerance also looks good for a telescope fitted with a coma corrector. To set up the GSO coma corrector properly, the total back focus (distance from the last lens to the focal plane) has to be about 75mm. The designer says that it is not critical and from 65mm to 85mm will produce a good spot size. This distance will be made up somthing like mine below, added to the height of the eyepiece focal point height above the eyepiece shoulder (or subtracting the height below the shoulder). 1.25" My 2" 2mm 2mm Spacing from last coma corrector lens to the shoulder 45mm 45mm 2" adaptor spacing 11mm .... 2" to 1.25" adaptor (if any) 19mm 19mm Spacers (Hyperion 14mm ring + empty 2" filter) 77mm 66mm Total (excluding eyepiece distance) My one 2" eyepiece has a focal point above the shoulder, and my 1.25" eyepieces are all within -12mm/+8mm of nominal, so are all fine. Tele Vue is unique in publishing the height below the shoulder of the focal point for all their eyepieces. For other users, you are going to have assume the focal point is close to the shoulder or measure the position. First, locate the prime focus by taping a piece of tracing paper to the top of the focuser and focusing on something. This does not have to be at night and can anything sufficiently distant so that it comes into focus, such as a church spire or distant tree. It does not depend on the telescope so using a refractor with a graduated focus scale is very convenient. You then measure how far in (plus) or out (minus) you have to move the focuser for each of your eyepieces in turn. For users only intending to use 2" eyepieces, a single 28mm Hyperion tuning ring might be fine. If you do not like the idea of finding empty filter rings, or more likely buying cheap ones on eBay and removing the glass, some suppliers (in particular Telescope Service) have spacing rings with the right 48mm thread, in a few sizes such as 10mm and 20mm, but these are generally expensive. Variable spacers are also available but these are not going to sink into your focuser tube. When I first set this up I had to remove a 2" to 2" adapter to allow the unit to go all the way into the focus tube. This left too little out focus so I made a plastic washer (from a yoghurt tub, see photo below) to prevent the corrector slipping all the way into the focuser and providing the necesssary out focus. One correspondent who uses only 2" eyepieces has done away with the eyepiece adaptor and has simply added enough extender rings to screw the corrector to each eyepiece as he uses it. I hope that this will is enough information to set up this corrector properly but I would welcome questions, and of course comments and correction.
  5. The Fighting Dragons of Ara ( NGC 6188 ) ( please click / tap on image to see larger ) The Fighting Dragons of Ara ( NGC 6188 ) Bright Nebula NGC 6188 and open cluster NGC 6193 are embedded 4,300 light years away in the Sagittarius arm of our Milky Way galaxy and can be seen with the naked eye south of Scorpius in the constellation of Ara. With powerful stellar winds and energetic ultra-violet radiation, massive stars sculpt the interstellar gas and dust of the nebula into wonderful shapes and cause the interstellar gas to brightly fluoresce. Closer to the hot young stars of the cluster, bright blue “sunlight” reflects off the clouds of gas and dust to produce the blue reflection nebulae seenin the image. Magnitude +5.19, RA 16h 41m 42s, Dec -48deg 48' 46". Approx. 3800 light years away. Image details: This is an HDR image constructed from exposures ranging from 2 seconds to 240 seconds in length. The aim was to capture the faint stars and details in the nebula whilst at the same time maintaining colour in the bright stars without clipping the highlights. Plate Solution: Resolution ........ 1.336 arcsec/px Rotation .......... 90.002 deg ( North is to the right ) Focal ............. 1475.57 mm Pixel size ........ 9.56 um Field of view ..... 58' 28.5" x 39' 0.8" Image center ...... RA: 16 40 09.903 Dec: -48 41 27.00 Telescope: Orion Optics CT12 Newtonian ( mirror 300mm, fl 1200mm, f4 ). Corrector: ASA 2" Coma Corrector Quattro 1.175x. Effective Focal Length / Aperture : 1410mm f4.7. Mount: Skywatcher AZ Eq6 GT. Guiding: TSOAG9 Off-Axis-Guider, Starlight Xpress Lodestar X2, PHD2 . Camera: Nikon D5300 (unmodified) (sensor 23.5 x 15.6mm, 6016x4016 3.9um pixels). Location: Blue Mountains, Australia Moderate light pollution ( pale green zone on darksitefinder.com map ). Capture ( 24 June 2017 ). 8 sets of sub-images with exposure duration for each set doubling ( 2s to 240s ) all at ISO800. 34 x 240s + 10 each @ 2s to 120s. Processing ( Pixinsight - 19 Aug 2017, 13 Jan 2018 ). Calibration: master bias, master flat and no darks. Integration in 8 sets. HDR combination. ......... This is a reprocessed version using the data I captured earlier in the year...
  6. Hi Does anyone feel able to recommend an OAG + Coma Corrector combination that achieves the correct spacing and good reliable results when connected to a Nikon DSLR? Cheers Mike
  7. Aenima

    Comet Catalina

    From the album: The next step.

    Was really chuffed to catch this comet, especially with the two tails. This i believe is the 5th comet i've caught 'on film' as it were. Along with Panstarrs - ISON - Jacques, and Lovejoy (forgot the numerical names). Equipment: ED80 - / 350D -/ EQ6 -/ CLS clip
  8. I recently tried imaging M7 with my 6" f/4 Newtonian. I had earlier commimated it with a Cheshire and Howie Glatter and was sure of the collimation. However, when I imaged using my DSLR with the coma corrector installed, I get focused stars off centre and not on the optical axis. Anyone experience anything similar before? What could this be? Tilt in the optical train? The focuser was drawn out only about 5mm to reach focus along with a 50mm extension tube. Any suggestion is welcome.
  9. ( Edit 20 Aug: adjusted to increase brightness ) ... The Fighting Dragons of Ara ( NGC 6188 ) ( please click/tap on image to see larger and sharper ) ...................... Original: The Fighting Dragons of Ara ( NGC 6188 ) ( please click/tap on image to see larger and sharper ) Bright Nebula NGC 6188 and open cluster NGC 6193 are embedded 4,300 light years away in the Sagittarius arm of our Milky Way galaxy and can be seen with the naked eye south of Scorpius in the constellation of Ara. With powerful stellar winds and energetic ultra-violet radiation, massive stars sculpt the interstellar gas and dust of the nebula into wonderful shapes and cause the interstellar gas to brightly fluoresce. Closer to the hot young stars of the cluster, bright blue “sunlight” reflects off the clouds of gas and dust to produce the blue reflection nebulae seenin the image. Magnitude +5.19, RA 16h 41m 42s, Dec -48deg 48' 46". Approx. 3800 light years away. Image details: Plate Solution: Resolution .......0.586 arcsec/px ( original full size image ). Rotation .......... 89.764 deg. Pixel size ........ 3.90 um. Field of view ..... 58' 41.6" x 39' 9.5". Image center ...... RA: 16 40 09.856 Dec: -48 41 22.50. Image bounds:. top-left ....... RA: 16 42 10.059 Dec: -49 10 30.54. top-right ...... RA: 16 42 06.489 Dec: -48 11 57.14. bottom-left .... RA: 16 38 11.010 Dec: -49 10 39.74. bottom-right ... RA: 16 38 11.897 Dec: -48 12 05.58. Telescope: Orion Optics CT12 Newtonian ( mirror 300mm, fl 1200mm, f4 ). Corrector: ASA 2" Coma Corrector Quattro 1.175x. Effective Focal Length / Aperture : 1410mm f4.7. Mount: Skywatcher AZ Eq6 GT. Guiding: TSOAG9 Off-Axis-Guider, Starlight Xpress Lodestar X2, PHD2 . Camera: Nikon D5300 (unmodified) (sensor 23.5 x 15.6mm, 6016x4016 3.9um pixels). Location: Blue Mountains, Australia Moderate light pollution ( pale green zone on darksitefinder.com map ). Capture ( 24 June 2017 ). 12 sets of sub-images with exposure duration for each set doubling ( 1/8s to 240s ) all at ISO800. 34 x 240s + 10 each @ 1/8s to 120s. Processing ( Pixinsight - 19 Aug 2017 ). Calibration: master bias, master flat and no darks. Integration in 12 sets. HDR combination PhotometricColorCalibration.
  10. My image of Omega Centauri ( NGC 5139 ) has been published as the NASA APOD for the 11th of July 2017 https://apod.nasa.gov/apod/ap170711.html Link to full size image on NASA site ( warning quite large - 4620 x 3720 ) Link to discussion of image on asterisk.apod.com ( credit apod.nasa.gov ) ( full size image - 4620 x 3720 ) Link to original post for this image back on the 10th of June
  11. I have a revelation (GSO) coma corrector that I use on my 130 pds with a Canon 1000d. I have noticed that I am still getting some coma. My question is, do I need a spacer between the corrector and the T ring. I can't find any definite information on this but I read somewhere you need 75mm between the rear element and the camera sensor
  12. Tarantula Nebula ( NGC 2070 ) in the Large Magellanic Cloud ( LMC ) Re-processed to tweak colour balance and bring out a little more faint detail: New version: Original: ( click/tap on image to see full size - the above compressed version looks a little soft; the full size version is sharper ) The Tarantula Nebula ( NGC 2070 ) is the largest and brightest emission nebula in the nearby irregular galaxy, the Large Magellanic Cloud ( LMC ). At a distance of 160,000 light years away from us, the Tarantula Nebula is so bright that it would cast shadows on the Earth if were as close to us as the Orion Nebula in our galaxy. First image with new telescope and autoguider/setup. Links: 500px.com/MikeODay photo.net/photos/MikeODay Details: Nebulae: NGC 2070 Tarantula Nebula NGC 2048 NGC 2060 NGC 2077. Open clusters: NGC 2042 NGC 2044 NGC 2050 NGC 2055 NGC 2091 NGC 2093 NGC 2100 Image centre RA 5h 38m 57.3s, Dec -69deg 20' 36.6" (nova.astrometry.net) Field of view (arcmin): 58.7 x 39.2 Scale (full size image) 0.585 arcsec/pixel. Telescope: Orion Optics CT12 Newtonian ( mirror 300mm, FL1200mm, f4 ) Corrector: ASA 2" Coma Corrector Quattro 1.175x Effective Focal Length / Aperture ): 1410mm f4.7. Mount: Skywatcher AZ Eq6 GT Guiding: TSOAG9 Off-Axis-Guider, Starlight Xpress Lodestar X2, PHD2 Camera: Nikon D5300 (unmodified) (sensor 23.5 x 15.6mm, 6016x4016 3.9um pixels) Filter: none Exposures: 14 x 240 sec ISO400 12 x 120 sec ISO400 10 x 60 sec ISO400 11 x 60 sec ISO200 10 x 60 sec ISO100 10 x 30 sec ISO100 Pixinsight & Photoshop 20 December 2016
  13. Hello! I bought a GSO 2 inch Coma Corrector for my 8inch Newtonian. I'm still having terrible coma on one of the corners which is actually worse than without the coma. The rest of the corners look fine with proper guiding. Here are some details and what I've done to try and solve the issue: 1- Spacing is 75 mm just as recommended. 2- Used a Cheshire, laser collimator, and a webcam to check collimation. 3- Squared the focuser so that it's orthogonal to the optical axis. 4- Tried another DSLR Note that once I collimate and double check that I'm collimated with all the tools, I always try to do a star test and collimation appears off (the dark spot isn't in the middle). Last time I tried to collimate the primary using a star but it's really tough to fine tune since due to the focuser's sag, I can't be sure that the star is in the middle of the fov. My take on the problem is that when I'm using the DSLR with the coma corrector, the weight is moving the focuser away from the center of the optical axis but I'm not sure this if this is the case. I've tried everything and I'm out of ideas. Below is a test image I took for Lagoon Nebula. Notice the coma on the left top side mostly, while the right side usually appear to have no coma (not the case in the attached image though for some reason, but usually the right side is fine). One more thing I've noticed, the stars on the left corner appear to be out of focus while the rest of the image appears well in focus (used a Bahtinov mask with APT bahitnov focus tool) There's also another image I took for a distant light to check collimation (since clouds covered the sky as soon as I decided to do a star test). It appears to be fine and I was able to center it better but didn't capture the image. Please let me know if you have any idea what's causing this. My number one suspect is the focuser's sag preventing me from doing accurate collimation although everything appears to be normal while collimating. I'm giving this another 2 weeks of my time, if it doesn't work I might quit astrophotography till I'm able to afford an APO. One more thing that needs to be added, when using the GSO CC I had to move the primary mirror up the scope by around 2 cm to be able to achieve focus. Clear Skies!
  14. Hi all, I've just bought a Samyang 14mm f/2.4 for my Nikon D5100 and am not happy with the results. I've already sent one back and now the replacement appears to be just as bad. As you can see in the sample there is quite a difference in quality. The images were taken at a fairly dark area, ISO400 for 30secs on a Star Adventurer. The crop is from the centre of the lens. Image quality only started to improve after stopping down to f/7.1. If the aberrations are this bad at wide open it would effectively be a useless lens. My kit 18-55 zoom gives far sharper stars across the aperture range. Am I expecting too much from the Samyang or should this one be winging its way back too? I appreciate any advice cheers
  15. Sky was nice and transparent around 2am, so it would have been rude not to take the binoculars out. As it was going to be a short session, I used the Lunt 16x70 on the monopd and #222 joystick (trigger-grip) head. First stop Jupiter; only two moons. Up to see how easy M65 & 66 were - answer: very and, while I was looking at them, NGC 3628 was also obvious with averted vision. Suitably emboldened I headed over to Melotte 111 (far too big for this binocular's field, but vibrant) to see what I could make of one of my favourite telescopic galaxies, NGC 4565. Put gamma Com at 3 o'clock and, sure enough NGC 4559 was in the middle, obvious with AV and possible with DV. Put 4559 at the top and bingo! Berenice's Hairclip was slap bang in the middle - nice not-so-little streak of light. Spent a long time just enjoying it, then the idea struck me: how many galaxies in the Coma-Virgo cluster could I see and identify? That cued what was both a highly enjoyable and highly frustrating 20 minutes. Starting at Vindemiatrix (boy, I love the colour rendition in the Lunt!) and headed over to M60 just over a field away. Nice and obvious. Then I went over to M87 and the shenanigans began! I reckoned that, with M87 just below centre, I should be able to see 7 or 8 galaxies in the same field. I could see at least a dozen, most of which were in Markarian's Chain but, before going there, I thought I'd have a shufti at M58, which can be an elusive target in 70mm binos from my suburban back garden, "enhanced" as it is by the ghastly "improved" streetlights that Hampshire County Council has, in what it tries to pass off as its wisdom, decreed that I must endure. Popped 58 in the middle, and it disappeared. Used AV on it and there it was again. OK, fine, to be expected, so how many could I see in Markarian's Chain? Again, lots, until I tried to count them, when half of them disappeared. Concentrate on M86 or M84, the others come back again. Look at them, and most of them disappear. Frustrating when trying to count them, but fun just making them come and go at will. So, how many galaxies did I see? I haven't a clue; I gave up trying to count them, but before chilly fingers and common sense sent me crawling back into my pit, I had a thoroughly enjoyable time.
  16. Greetings! I own Skywatcher's 6'' F/5 reflector and I've recently purchased and installed Moonlite focuser. I took all collimation of mirrors and the focuser very seriously and I worked with various tools like Howie Glatter's collimator and tublug, TS Optics Concenter-2z eyepiece and Cheshire. Everything looks perfectly centered and aligned. However, I still see optical aberration in a form of coma and I have elongated egg-form stars in the edges. Here's is how it looks like: I did a star test and I see that when the star is in center then, it looks OK. But, not in the edges. I do use old coma corrector that my friend borrowed me and I either it doesn't help or I am missing something in collimation or something else. I will appreciate any advice you can give me. Thank you!
  17. Tarantula Nebula ( NGC 2070 ) in Large Magellanic Cloud ( LMC ) by Mike O'Day. The Tarantula Nebula ( NGC 2070 ) is the largest and brightest emission nebula in the nearby irregular galaxy, the Large Magellanic Cloud ( LMC ). At a distance of 160,000 light years away from us, the Tarantula Nebula is so bright that it would cast shadows on the Earth if were as close to us as the Orion Nebula in our galaxy. New version ( April 9 ): ( please click / tap on image to see larger and sharper image ) ............ Older versions: And here it is re-processed to try to reduce the red background ( due to light pollution I think ) without impacting the colour of the stars too much ( please click / tap on image to see larger and sharper ) Details: Nebulae: NGC 2070 Tarantula Nebula NGC 2048 NGC 2060 NGC 2077 Open clusters: NGC 2042 NGC 2044 NGC 2050 NGC 2055 NGC 2091 NGC 2093 NGC 2100 Image centre ... (nova.astrometry.net) Field of view (arcmin): ... Telescope: Orion Optics CT12 Newtonian ( mirror 300mm, fl 1200mm, f4 ). Corrector: ASA 2" Coma Corrector Quattro 1.175x. Effective Focal Length / Aperture ): 1410mm f4.7. Mount: Skywatcher AZ Eq6 GT. Guiding: TSOAG9 Off-Axis-Guider, Starlight Xpress Lodestar X2, PHD2 Camera: Nikon D5300 (unmodified) (sensor 23.5 x 15.6mm, 6016x4016 3.9um pixels). Filter: none. Exposures: 100 sub exposures ranging from 1s 100ISO to 240Sec 400ISO HDR processing of 5 sets of images Pixinsight & Photoshop 20 December 2016 / April 2017
  18. The Rosette Nebula and Cluster ( NGC 2237 and 2244 ) in the constellation Monoceros edit: updated 30th Dec with improved colour balance and slightly increased brightness ... ...... original: ( please click / tap on image to see larger and sharper ) Still a work-in-progress really... with only 10 x 4min exposures for the main 'lights' before the clouds came over. I will try to add some more data when the moon has gone I am still experimenting with how to get the best out of the D7500. With the very warm nights ( low to mid 20s all night ) the 'warm pixels' are very noticeable so I reverted to my old practice of in-camera dark subtraction. This worked quite well and produced a nice smooth noise floor in the integrated images - albeit at the expense of more exposures. ................. Identification: The Rosette Nebula ( NGC 2237 ) is a large, circular emission nebula in the constellation Monoceros. It surrounds a cluster of hot, young stars known as the Rosette Cluster ( NGC 2244 ). ( SkySafari ) NGC 2237, 2244 Caldwell 49, 50 North is up. .................. Capture Details: Telescope: Orion Optics CT12 Newtonian ( mirror 300mm, fl 1200mm, f4 ). Corrector: ASA 2" Coma Corrector Quattro 1.175x. Effective Focal Length / Aperture : 1400mm f4.7 Mount: Skywatcher EQ8 Guiding: TSOAG9 Off-Axis-Guider, Starlight Xpress Lodestar X2, PHD2 Camera: Nikon D7500 (unmodified) (sensor 23.5 x 15.7mm, 5568x3712 @ 4.196um pixels) Location: Blue Mountains, Australia Moderate light pollution ( pale green zone on darksitefinder.com map ) Capture ( 23 Dec 2017 ) 9 sets of sub-images with exposure duration for each set doubling ( 1s to 240s ) all at ISO400. 10 x 240s + 5 each @ 1s to 120s imaged ~ +/- 1.5hrs either side of meridian maximum altitude ~ 51.3 deg above north horizon Processing ( Pixinsight ) Calibration: master bias, master flat and in-camera dark subtraction Integration in 9 sets HDR combination Image Plate Solution =================================== Resolution ........ 0.633 arcsec/px ( full size image ) Rotation .......... 0.181 deg Focal ............. 1367.90 mm Pixel size ........ 4.20 um Field of view ..... 58' 59.4" x 39' 15.0" Image center ...... RA: 06 31 55.638 Dec: +04 56 30.84 ===================================
  19. The Great Barred Spiral Galaxy ( NGC 1365 ) in the constellation Fornax edit: new version with new long exposure data ( 52 x 240sec ) and better dark subtraction / dithering to remove streaks in the noise and amp glow. This also allowed for a greater stretch revealing more faint data in the galaxy and small faint fuzzies in the image .. The Great Barred Spiral Galaxy ( NGC 1365 ) in Fornax ( please click / tap to see larger ) and below I have added a 100% crop of new version: ........ original image: NGC 1365 ( please click / tap on image to see larger ) ............... The Great Barred Spiral Galaxy ( NGC 1365 ) in the Constellation Fornax Below the equator, not seen from much of the Northern hemisphere, NGC 1365 passes very nearly directly overhead an observer situated near Cape Town, as Sir John Herschel was in November of 1837, or near Sydney, as I was, almost exactly 180 years later, when I photographed this “remarkable nebula” that is numbered 2552 in his book of observations from the Cape. Not called a “nebula” now, of course, this striking object is one of the nearest and most studied examples of a barred spiral ( SB ) galaxy that also has an active galactic nuclei resulting in its designation as a Seyfert galaxy. At around 60 M light years from Earth, NGC 1365 is still seen to occupy a relatively large area ( 12 by 6 arc minutes ) due to its great size; at some 200,000 light years or so across, NGC 1365 is nearly twice as wide as the Milky Way and considerably wider than both the Sculptor and Andromeda galaxies. This High Dynamic Range ( HDR ) image is built up from multiple exposures ranging from 4 to 120 seconds with the aim of capturing the faint detail in the spiral arms of the galaxy whilst also retaining colour in the brightest star ( the orange-red 7th magnitude giant, HD 22425 ). Also, scattered throughout the image, and somewhat more difficult to see, are numerous and far more distant galaxies with apparent magnitudes of 16 to 18 or greater. Mike O'Day ................. Identification: The Great Barred Spiral Galaxy New General Catalogue - NGC 1365 General Catalogue - GC 731 John Herschel ( Cape of Good Hope ) # 2552 - Nov 28, 29 1837 Principal Galaxy Catlogue - PCG 13179 ESO 358-17 IRAS 03317-3618 RA (2000.0) 3h 33m 37.2 s DEC (2000.0) -36 deg 8' 36.5" 10th magnitude Seyfert-type galaxy in the Fornaux cluster of galaxies 200 Kly diameter 60 Mly distance .................. Capture Details: Telescope: Orion Optics CT12 Newtonian ( mirror 300mm, fl 1200mm, f4 ). Corrector: ASA 2" Coma Corrector Quattro 1.175x. Effective Focal Length / Aperture : 1400mm f4.7 Mount: Skywatcher EQ Guiding: TSOAG9 Off-Axis-Guider, Starlight Xpress Lodestar X2, PHD2 Camera: Nikon D7500 (unmodified) (sensor 23.5 x 15.7mm, 5568x3712 @ 4.196um pixels) Location: Blue Mountains, Australia Moderate light pollution ( pale green zone on darksitefinder.com map ) Capture ( 22 Nov 2017 ) 6 sets of sub-images with exposure duration for each set doubling ( 4s to 120s ) all at ISO400. 70 x 120s + 5 each @ 4s to 60s total around 2.5hrs Processing ( Pixinsight ) Calibration: master bias, master flat and no darks Integration in 6 sets HDR combination Image - Plate Solution ========================================== Resolution ........ 1.328 arcsec/px Rotation .......... -0.008 deg ( North is up ) Field of view ..... 58' 8.6" x 38' 47.5" Image center ...... RA: 03 33 41.182 Dec: -36 07 46.71 ==========================================
  20. Hi all budding astrophotographers, I recently acquired a C9.25 and after a few days I had my first clear night (moon rising). I bought a Celestron f6.3 reducer which I connected after removing the 2" back, then connected my Canon 1100d DLSR camera via a T-tring. Many of the central stars seem sufficiently round in shape but I was surprised to find so many stretched stars in the corners even after the installation of the x0.63 reducer, I thought it also acted as a coma corrector. The dew shield was not perfectly sitting on the scope but I don't imagine this could be the cause. Is this coma on the corners or something else? Do you think I'm being unrealistic of my expectations when using the reducer to also flatten the image? Is it because of the unrealistic field of view from a DLSR camera on the C9.25 or perhaps I have possibly a dodgy reducer or could collimation be the source of my problem? FYI, the image is a single 5 min exposure without any processing, guided using a finder guider and using a CLS filter, EQ6 on a pier. Im pleased with the image apart from the corners due to the stretched stars. Many thanks for looking, your advice is always appreciated.
  21. [ITEM NOW SOLD] Skywatcher 0.9x Coma Corrector Suitable for use with Newtonian reflector telescopes with F-ratios F4-F6 but is optimised for the SkyWatcher Explorer F5 telescopes with 2-inch focuser. Also acts as a 0.9x reducer so a F5 Newtonian becomes F4.5 and F4 becomes F3.6 etc. Requires 55mm back focus. £70 + £5 P&P Payment via PayPal, Bank Transfer or cash if collecting. Item is currently located in Leeds/Wakefield area, but it could be made available in Manchester or Chesterfield areas if given enough notice.
  22. Hi I've attached an image of M42 that I took last night. I've done nothing to it except stacking the 15 x 120s frames. I have the NexStar 6SE SCT. I'm trying to work out if the funny star shapes are coma or something else? Last night happened to be my first night dithering the images too. So i'm not sure if that has caused it? Focus wise I don't think it's too bad (please correct me ). It is present in my RGB frames too. ** I should point out that this image was taken with my f/6.3 focal reducer / corrector ** (But if it is coma, it's not doing it's job properly!?) Thanks Joe
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