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Found 15 results

  1. Celestron's EdgeHD product line features an integrated field flattener. As with all flatteners, these produce optimal results when the imaging plane is a specific distance from the flattener. In the EdgeHD whitepaper Celestron describe the optimal backfocus of 133.35mm (5.25") for the 8" model, and 146.05 (5.75") for the 9.25", 11" and 14" models. They suggest that the image plane should be placed within 0.5mm of this distance. When putting together an imaging train it can be quite hard to determine the actual backfocus. You could add together all the optical lengths quoted by manufacturers, you could get calipers and actually measure each part or even try to measure the entire thing (although it can be quite hard to figure out where to measure from. At some point, you have to trust some manufacturer spec (unless you fancy risking your sensor). Once all this is done you might, however, find that things vary ever so slightly; everything from the tightness of threads to the T-ring not quite giving exactly 55mm. How do you work out if you've done it all correctly? In a table in the whitepaper (page 13), focal lengths are given for each OTA (for example 2125mm for the 8" model). Hypothetically then, it should be possible to measure whether or not you're at optimal backfocus by plate solving for your image scale. In the same table, an image scale is given for a sensor with pixel size 6.4 micron but you can use a calculator (such at the astronomy.tools one) to work out the expected image scale for your particular sensor. This does require that your image is as close to perfect focus as possible. Putting all this into practice. I used my calipers to try to get the image train as close to 133.35mm as I could and then plate solved some resulting data taken with a DSLR with 5 micron pixels. From my calculations, if I'm in focus at the correct spacing, I should have an image scale of 0.485"/pixel. However, my astrometry.net solves gave an image scale of 0.495"/pixel. Working backwards, this indicates that I was at a focal length of 2083mm, quite a way inside 2125mm. Although I can't find a reference I've read that, for an SCT, the focal length changes by approximately 3mm for each 1mm of backfocus, this implies that my sensor is 14mm too close! Now, I'm no expert with calipers but I feel like I couldn't have been more than a few mm out, and if anything I thought I was too far. I suppose I could have been a bit out of focus but surely not ~10mm. Is there a mistake in my logic of aiming for 2125mm focal length?
  2. When I align my Celestron CPC 1100 EdgeHD through Starsense Auto Allignment, after Completing the successful plates resolve in the handset, you have to press enter to continue to the second stage of selecting a bright star to point scope towards it, which I used to do in the past. Today after successful plate resolve, when I tried to press enter it takes you back to the first screen “Star Sense Ready” instead of selecting the brightest star option. Can anyone help and advise where am I making mistake ?
  3. Hi folks, I've been seeing tear drop shape stars with the EdgeHd 8 and ZWO ASI294MC Pro camera, so I verified the collimation. I'm using a celestron x0.7 reducer. Does collimation needs to be checked with an eyepiece or with the camera and with or without reducer? I'm asking since I verified my collimation yesterday and couldn't see the concentric rings with the complete imaging train (ASI294MC, OAG, and x0.7 reducer). It was only showing the inner shadow and outer circle. I than replaced the AS294MC with my guide cam (ASI120) which has a much smaller sensor and could see many rings. While, to my view, it seems to be collimated, it's strange that I can't see the rings with the main imaging cam. Any thoughts? Here's how I left the collimation after some adjustments with the guide cam. Kind regards, Jairo
  4. I am associated with a college who had purchased a Celestron EDGE HD14 two years ago. Due to the high humidity of the place, there has been quite a bit of fungus which has grown on both the front corretor plate and the rear coma corrector lens which is inbuilt into the central hole. If anyone would know how to disassemble the EDGE HD 14 from the front and rear end it would be very beneficial. TIA
  5. Okay folks, so, for a variety of reasons, including but not least an appalling sequence of poor weather since my last post on this particular topic, I have been unable to obtain an accurate measurement of the focal length off my 8” EdgeHD incorporating Baader SteelTrack Focuser and Click-lock Diagonal. I managed to remedy this situation over the weekend just past. Initial measurements based on adding the optical path of each of the components together, had the complete resulting optical path at about 2400mm, however this was not bourne out in practice. Using my 22mm T4 Nagler, at 2400mm focal length this should have given approx 45’ TFOV. Using M81 and M82 as a yardstick (approximate separation 36’), they should easily have been visible in the same field of view, however they were not. Extrapolating back from these values seems to be indicating a focal length somewhere between 3000 and 3225, which makes the revised speed of the system a whopping F15 to F16. This must be having a significant detrimental impact on the sub-aperture correction inherent in the Edge HD design, so I’m thinking of removing the Steeltrack from the system and replacing with a FeatherTouch or equivalent. This measurement is actually consistent with a drift measurement I made last year, (instructions courtesy of Don Pensack), but discarded due to it being so far removed from the expected result nearer 2400mm. But the proof as they say is in the pudding. So for those considering adding a Crayford to their EdgeHD, based on this experience I would say don’t. From feedback on this topic in CN, it is very possible that it is something to do with either the slightly faster primary/secondary combination in th EdgeHD and/or the sub-aperture correction in the baffle tube, possibly resulting in significant vignetting. (Thanks to Don Pensack and Edggie from CN, for their input). If you are interested in reading the CN thread discussing this you can find it here: https://www.cloudynights.com/topic/574002-calculating-effective-focal-length-of-an-edgehd/ Kind Regards Paul.
  6. Hi there, could someone please provide depth and thread pitch for the front cell screws on an 8" Edge HD, as in the empty socket portrayed in the attached photo:8" Edge HD, as in the empty socket portrayed in the attached pho Kind Regards Paul J.
  7. Hi there, I'm wondering if any SGL members might have a spare secondary assembly for an 8" EdgeHD. Basically, the previous owner of my Edge did something abominable to the collimation screws which mean that they will not move. I suspect the original owner has used a threadlock product or similar on the collimation screws. I am therefore looking to replace the entire secondary assembly. Shipping the scope off to David Hinds is one possibility and I am pursuing this, however I'm also looking at other options, such as replacing the secondary assembly myself. Kind Regards Paul J.
  8. Well I've had three good, clear night's here and dry days so I was able to leave my mount hibernated to cut down on set-up time (wish I had an Obsy!) I don't have much worthwhile data to show for my efforts but I've done a lot of sorting out. I can now get reasonable results guiding with my OAG at 2800mm which has been a bit of a challenge but I'm happy with where I am. My images were really noisey though - bad enough to be obscuring the target and I wasn't sure if it was because the setpoint cooling was only getting down to -20 C (usually go to -25 C in winter and this is my first summer imaging) or if it was the 900 second exposures. Anyway, I had a lot of fixed pattern noise that neither darks nor AA5's defect mapping could sort out. Some 90 second subs of M52 convinced me that the noise wasn't solely down to the length of the exposures so I was beginning to worry that my camer had developed a fault... SGL to the rescue and another thread pointing to power leads as a possible source of noise. I'd be running the camera and filter wheel from the same power line as part of a loom, but using a seperate cable for the Atik 383L+ seems to have solved the problem. So pleased to have learnt so much, but this is all I have to show for now. Celestron EdgeHD 11 on a DIY hypertuned CGEM DX, using QHY IMG0H and PHD to guide. 3 x 900 sec L exposures binned 2x2, stacked in AstroArt 5 with a quick tweak in PhotoPlus x4 Hopefully next time I post this target it'll be in colour with a lot more data but I'm looking forward to seeing what I can get out of the scope for DS)s even at f/10. Thanks for looking.
  9. What should I buy for a Canon 40D (Astrophotography): a Celestron EdgeHD 8" AVX or a Celestron AVX SCT 9.25" since the price differs only for 100EUR? I want to have nice DSO pictures but be able to see planets as well. Been using a 114mm reflector for 6 years. Thanks in advance
  10. Hi there, the saga continues... Earlier this month I started the post: https://www.cloudyni...h-of-an-edgehd/ In which I was seeking help in the calculation of the revised EFL for my 8" EdgeHD. Courtesy of Don Pensack from CN, I was furnished with a formula for calculating the EFL based on the timing of a star across the FOV. The first clear sky opportunity to carry out this calculation came this past weekend, in which I used a 17mm Nagler for the timing. Timings were as follows: 1/ - 2m 4 secs -> 2.06m -> EFL = (82/0.525)*17 = 2698mm 2/ - 1m 57 secs -> 1.95m -> EFL = (82/0.4875)*17 = 2859mm 3/ - 1m 55 secs -> 1.92m -> EFL = (82/0.48)*17 = 2904mm Giving an average EFL of 2820mm or f13.89. This appeared excessive to me, way more than I was expecting. Of course the results are dependant on the accuracy of the timings and I probably need to take more measurements, however I'd be interested in hearing feedback from the learned masses on SGL. One thing that has become evident using the Baader Steeltrack and Click-lock diagonal in the light-path is that I'm pretty sure the images through the Nagler do not appear to be as crisp as I remember them via my humble Celestron 40mm Plossl and the stock 1.25" visual back and star-diagonal. I also noted that the field stop in the Nagler didn't appear to be as clearly defined as I was lead to believe it should be, from reading the numerous reviews of Naglers on the various web forums. I'm thinking that the steel-track in combination with the 2" diagonal (especially in light of the long EFL calculated) is having a seriously detrimental impact on image quality. I am now considering selling the steel-track and installing a Feathertouch microfocuser in its stead. All constructive critique welcome :-) Kind Regards Paul J.
  11. Hi guys, I need a guide for a "long run" purchase plan. Long Story Short: I want to buy colour CCD or CMOS camera for DSO via my SW 130PDS, and cannot decide as here the Long Story kicks in!: I am almost sure, in few years distance, I will go for a Hyperstar Solution. I am only 2 years in Ap hobby and these clouds are KILLING ME! London is not the best place for such a hobby, - I am sure you all will agree on that. So, to get the best of that "one clear night a month", - Hyperstar is probably the only option... or, alternatively, simply emigrate to LaPalma... I am 99% sure I will go Hyperstar way sooner or later, and like everyone, I hit the budget wall. I look for cam in around £1k, Hyperstar will cost around £1k and plus the scope minimum £1k. I am not the lucky one who can afford it in one go, so I think to by cam which will be usable with Hyperstar in the future and here are some question I have googled and googled and could not found out: 1) of course, which cam, I think of ZWO ASI1600MC PRO or ASI294MC PRO. I am sure, both will perform OK on SW 130PDS, but what about Hyperstar??? And the next Q goes in relation; 2) My wallet will be able to afford something like EdgeHD 8" (+ Hyperstar), however, these ZWO cams are sooo big and I afraid 8" aperture will be too small as ZWO may place too much shadow while sitting on the Hyperstar - anyone tried them on EdgeHD 8" ?; 3) If HD 8" is too small, I am sure, EdgeHD 9.25 is too expensive for my wallet, is there any alternative for 9" CSC + Flattener + Hyperstar to make a setup cheaper than HD 9.25" price (insane price difference... insane!).. 4) Or maybe, - I had to start with the question, - which is the ideal colour cam for HedgeHD 8", but if there are any cheaper options with larger Aperture + Flattener, - why not? All goes on NEQ6 mount, - back garden in London, Woolwich.... with LP level which I call "the constant Polar Day". P.S. Why Colour cam? Filter prices! I want to avoid them till I will win a lottery.
  12. Anybody from the UK ever buy a Feathertouch Microfocuser from the US? I’m considering replacing my Baader Steeltrack with the Feathertouch. Comparing prices in the UK against suppliers in the US it seems that it might be beneficial to buy direct from the US, especially considering that as a CN member you get 10% discount from Astronomics. If the package is small enough it might just get by customs as well ?
  13. Hi there, Is there such a thing as a Vixen dovetail bar specifically designed for the EdgeHD? I note that there are CGE specific bars in the classic Celestron orange livery, but I have been unable to find a vixen style equivalent. I need the bar for my 8” Edge to allow the mounting of my new Guidescope mount. If no exact equivalent, can someone recommend an appropriate replacement. I am wary of plumbing for just any old generic bar. I would prefer direct attachment to the OTA as opposed to the use of radius blocks, need to keep overall weight down. Kind Regards Paul J.
  14. Two questions if I may. 1. Can the three screws marked by yellow arrows in the picture below be used to mount a second finder shoe on the C11 EDGE HD scope, permitting both a straight through and a right angle finder to be fitted? 2. The EDGE has field flattening optics inside; is the distance from the visual back to the chip critical, or by making adjustments to the position of the mirror to achieve focus on a chip say 250mm away from the visual back mean the field will still be flat at that distance? Thanks. James
  15. Hi there folks, wondered if you could review the logic in my calculation of EFL for my 8" EdgeHD. My revised outfit incorporates the following: Baader Steel Track Focuser - Light path from Baader specs given as 120mm when fully extended, focus range of 30mm. Baader Click-lock Star Diagonal - Light path 112mm Technique for focus is to bring the scope to rough focus with the stock SCT Focuser, with the Steeltrack at the midpoint of its focus range, so set to 15mm. Recommended back focus by Celestron 133mm Therefore revised back focus would be: 120 - (30 - 15) = 105mm + 112 = 217 giving a delta of 217 - 133 = 84mm General rule of thumb recommends 10mm of focal length for every additional 3mm of back focus, therefore: (84/3) * 10 = 280mm giving an approximate revised EFL of 2032 + 280 = 2312mm with the scope now operating at F11.3. Kind Regards Paul.
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