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Stratis

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Everything posted by Stratis

  1. Generally I would agree, but with the RST-135 in particular this seems to be a good thing. It has a very tight response and no backlash to speak of on either axis, but like most harmonic mounts does need to correct sometimes quite rapid drifts. 1sec is about as high as I like to go with it, 0.5sec improves matters if the seeing is decent, this is something many owners of the mount have noted and it's in the 'unofficial' manual for the mount. Multi-star seems to mitigate chasing the seeing, and the subs are good at least at the shorter FLs I usually contend with. Part of my hopes in this upgrade plan are that I'll be able to make better use of my big scopes which tend to be relegated to visual work. Thank you for this @vlaiv, I had no idea this camera even existed and even if I had, I'd likely have dismissed it due to my overall poor impression of its predecessor. There's a review on FLO from a fellow 290MM user that clearly states the 220M is a superior camera specifically for OAG use, so that's fantastic news for me. Thanks also @ONIKKINEN for the similar recommendation! Can I ask which other guide cameras you've used in the past and how it might compare, especially in terms of faint star SNR in OAG usage? I've been working towards a truly portable but powerful imaging setup that can fit into hand luggage on a flight, and OAG/filter/rotator combo unit is a big part of that I'd rather not waste by falling back to a guide scope. Also I've long held the dream of using an OAG to guide an SCT at f/6.3 or even f/10 instead of having to bolt an achro to the top rail with all that added mass. The 290MM works fine on a guide cam but haven't had the clear nights to test it on the OAG. @Elp you're right in what you say. Part of the plan for a more sensitive camera is the use of a broad NIR filter to reduce seeing interference with the guider. At present the 290MM just isn't sensitive enough for both fast exposures and NIR.
  2. As topic really I have searched about this many times, even comparing QE curves as best as one can, but I've not been able to confidently select a guide camera capable of accurate, rapid corrections (0.25sec or less). Time was the SX Lodestar was the undisputed champ of guide sensitivity, but the CMOS era is more complicated it seems. I currently use an Altair GPCAM2 290M. As the happy owner of an RST-135, the only complication of the mount is the necessity for rapid guiding exposures; the unofficial manual (authored by my mount's first owner, as it happens...) makes this clear and it's my experience that 0.5sec is as fast as I can achieve with the 290M / 30mm guidescope setup. As I plan switching to OAG and possibly longer focal lengths, I fear I will need a camera that can make better use of faint signal. Are there any guide cameras that can be recommended on raw QE? Almost every other metric from expense to field of view to image quality to transfer rate I can work around... it's that 'ultimate' performance that I need.
  3. There was definitely a bandwidth issue. This is known with the RPi in that it doesn't really keep up with USB3 specs, especially not when all its ports are loaded as it's basically just a soldered-on £5 USB hub, but I had hoped that the internal memory buffer could compensate. It seems it does compensate in that the data is delivered and somewhat faster than USB2 speeds, but the signal is somehow biased in the process. I used a USB-C hub with a Surface Go 2 tablet (I normally use it for focusing and polar alignment at the mount) to take frames with NINA and the output was way better. Damn shame as the RPi is perfect in every other respect, sips power and super lightweight as remote control box.
  4. Offset was the setting I had the least idea about, thank you for clarifying. Looking at the histograms you're clearly right, I was wondering why the values chopped off so abruptly like that. If I may ask another newbie question, should I be using Bias frames or Dark frames with this camera? From what I've read a Dark frame includes the data the Bias frame would?
  5. Thank you guys! The only experience I have with OSC imaging has been a 585-based sensor (which produces profoundly different output) and my 6D which is hardly comparable. Really good to know it's normal behaviour. I shall have to learn how to process it out
  6. UPDATE: All issues fixed! Rather than necropost and drag this back to the top of the forum, I'm editing this top post. Previously, I had concerns over a strange magenta gradient appearing in the darks and bias frames of an Altair 26C. Initially the other forum members reassured me (see below for very helpful replies) that all is well, and indeed I was able to resolve the issue. I was able to trace the problem to the use of a Raspberry Pi 4 as the imaging computer. There is something strange in the way the RPi's internal USB hub interfaces with the 26C, as by switching to a Windows PC and NINA the gradient (however mild) disappeared completely leaving beautiful even darks.
  7. Reaching out to people who own both an Askar FMA 135 astrograph and a thread gauge! The FMA135 is a neat bit of kit, but I'd like to be able to attach something to the front threads, for example a 2" filter or a stack of M48 spacers to use as an extended lens hood. The lens cap threads directly onto the lens cell; is anyone able to determine what thread size that is so I can get an adapter made up? All the best, Paul
  8. As a recent owner of an RST-135, I can attest this is not the case: the Rainbow Astro HD mounts have two mounting systems, 3/8" centre thread plus two M8s 45mm apart. I literally just swapped my AZ-GTi (which I LOVE and has served as my travel AP mount wonderfully) for the RST in exactly the same mounting arrangement and It Just Works. @Ags Happy to hear you fixed your GTi, I still use mine as my solar scope mount. In the future for you, I strongly, strongly recommend a 'Small Harmonic Drive' mount.... I've had a huge SCT hanging off the side of mine, it's practically the same size as the AZ-GTi but throws big scopes around like they're not there. Only concern is with legstrike, as these things have enough torque to physically bend and shear your equipment without pausing for breath...
  9. Hi all, Getting back into astro after a long break, and digging through equipment drawers I've stumbled across these two Astro Engineering ImageMate 4x units. I have no idea whatsoever how I ended up with two of these things... but more to the point, they are completely different! You can see from the images, both are marked identically. One is physically over 5mm taller, but most significant is the clear disparity in optics, the shorter unit has a much smaller clear aperture and optic assembly so the prescriptions have to be different. I would like to sell one to a good home as I hardly need two, but before that happens I'd like to know how these things differ. A comparison test would be ideal, but I don't really have the expertise to critically judge and clear nights are at a premium. If anyone is experienced with these units or their manufacture, and can shed some light on these differences I would really appreciate it! ~Paul
  10. I have three SCTs in the stable, a SkyWatcher 127XLT (so basically a blue-tube C5), a 2014 orange-tube 8SE OTA, and most recently a reasonably-new 6SE OTA. All three are Synta-era XLT-coated. Unfortunately between them I am missing several mounting screws that previous owners have lost over the years, so adding finder shoes is really difficult. Does anyone know the appropriate finder shoe screw thread for these Synta OTAs? There's a post on here which states that the old USA models used an Imperial thread, but I feel like the chances of a Chinese manufacturer using Imperial sizing is very, very low. Please help if anyone knows, or if anyone has any of these scopes and a way of determining thread pitch and screw size
  11. Well it's been a bit of a rollercoaster since I started this thread, thank you to those offering advice My CEM60 has to have a full service as it turns out the previous owner (since learned he is a convicted criminal....) did some 'DIY' inside the mount and badly screwed it up. It's entirely correctable, but I want a proper repair warranty on it for the next owner so they can be assured it'll work as advertised. Til I get a new mount I am confined to my AstroTrac and baby refractors. I've reviewed the payload specs for the CEM40 and it really should work fine with my largest imaging scopes, the C8 and the 115mm triplet. My biggest and most irritating scope to mount is a 152 f/5 achromat which is both long and heavy so that may be out of its comfort zone for imaging, but for visual should be ok. I recently sidegraded my imaging camera to a much lighter setup which should help a lot with its payload moment too. I've confirmed I cannot use my beloved Avalon T-pod 110 with the CEM40 so if I go that route I will have to abandon it. Anyone in the market for a near-mint black Avalon T110 T-pod with free CEM60 adapter plate?
  12. Great news for us remote imagers (or people who just don't like having a laptop constantly open), the Raspberry Pi 4 has been released! This model is WAY more capable than previous versions, and has some major upgrades which make it very attractive for AP; Up to 4GB of RAM - this speeds up platesolving and enables on-board stacking of larger subs Much faster CPU - everything runs better, at much greater power efficiency, and more high-demand apps at once USB3 - finally! So new CMOS cameras and large-chip sensors can rapidly transfer their subs to the Pi without amp glow Gigabit Ethernet - for people with observatories, this is critical for transferring subs Onboard wifi - sadly the same as the old Model 3 but still, it enables remote control and connection to wifi mounts We've seen the Pi and other SBCs used in things like the ZWO ASIair, I really feel the new Pi blows everything else out of the water though in its price range. The efficient CPU means you can effectively run this off a power bank and never have to worry about its draw, and the USB3 means you can link up numerous add-ons like long-range wifi adapters without impacting your sub downloads from the camera which was always a risk with the shared USB2 bus on the old Pi. I've ordered mine and going to be setting it up as a remote Kstars-based imaging controller bolted to the scope itself; anyone else thinking of doing the same?
  13. Hi all, Coming back to astro after a long break, many ups and downs I recently hauled my trusty CEM60 out of limbo and realised I'd like to shift to a smaller mount, as I have never come near the incredible weight limits on this mount for imaging or visual. The new CEM40 really looks perfect in most regards, so I am hoping that will serve as my new main imaging mount. I image with apo refractors, from a 7kg 115mm TS triplet down to a little WO Megrez 72 at only 2kg on an AstroTrac, with both DSLR and QSI 583wsg (so about 2kg camera package). My greatest imaging load has never exceeded 12kg. I already have an amazing Avalon T-110 T-pod underneath the CEM60, with an iOptron adapter atttached, this one in fact: https://www.teleskop-express.de/shop/product_info.php/language/en/info/p10799_Avalon-T-Pod-110-130-Adapter-Kit-for-iOptron-iEQ45-and-CEM60-Mounts.html This adapter has the central peg for iOptron, plus mounting holes set around the perimeter for the alignment pegs. The adapter has two sets of two threaded holes; the first set is 130mm apart across the centre, and fits the CEM60 perfectly. The second set is 120mm apart across the centre, and I think is meant to fit the smaller iOptron mounts like the iEQ30. So the £1400 question; can the adapter accept a CEM40 mount? Can the two threaded holes set 120mm across the centre mate with the CEM40? If anyone has any info on the absolute mounting hole arrangements for the CEM40 alignment pegs it would really help
  14. I am quietly thrilled this thread is still going... I'd taken a long break from AP as a new job ate all my waking hours, but I have that under control now and I've got a few new scopes in the stable. The ZS66 of course, remains I have just completed construction of a 50mm finderscope conversion into a guidescope for my Lodestar; if early tests are any indication it will guide up to 1500mm no problem so everything in my lineup is catered for, with a guide load of barely 250g. Seriously, if nobody's tried guiding with one of these setups they should, once the guidecam is screwed into the finderscope it is like an iron bar, no flex whatsoever and no possibility of focus slip. I have a field flattener yes, it's the Altair Astro cheapo one that reduces to 0.8x and flattens, I believe. I haven't tried it with the ZS66 yet but perhaps I ought to. Is anyone familiar with the proper spacing for those?
  15. The issue here is with the nature of your 'measurement' waveform; a soundwave is distinct from a light beam in a very specific manner; it is not at the greatest possible speed within its medium. The medium of sound is whatever physical medium is carrying it; if it is air, then it is Mach 1. This however does not equal 'c' in your equations, as it is possible to exceed the speed of sound in any given medium. You falsely attribute the character 'c' to mean Mach 1, when one of the governing principles of the letter c in physics is that it is the upper asymptotic limit for all velocity within that medium (for light, a vacuum), not just the wavefront itself. Also, if you are using only a single reference frame then STR basically ceases to apply; we here on Earth are hurtling through the cosmos at quite a velocity yet notice no dilation or synchronisation issues here because we are all in roughly the same inertial frame. STR only applies when two bodies are in relative motion. If your second observer is on the platform then the synchronisation and dilation issue returns with a vengeance.
  16. Stratis

    Ostara 102ED Unboxing

    Here's my unboxing of the Ostara 102ED APO Refractor Premium package. This scope is not so well-known, so I've included as much detail as I can!
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