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Oddsocks

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About Oddsocks

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    Engineering-electronic and mechanical design, development and implementation, Software development, Astronomy, Photography, Hiking, Sailing, Literature, Music, Art, Theatre, Single malt Scotch Whiskey.
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  1. It’s OK for a dedicated setup as long as you don’t need more than 55mm BF from the T thread to the sensor and that means usually you can’t squeeze an OAG into the gap, separate filter wheel and camera only might just fit. I use a couple of QSI cameras with built in OAG and FW and can usually manage with just 55mm BF but separate FW, OAG and most cameras just won’t fit. It’s a bit odd that WO, and several other manufacturers, stick to this 55mm flattener BF for DSLR’s, you’d have thought they’d have caught on by now that probably half the astrophotographers on the planet were using separates in the image chain and design the standard BF to something like 75mm and provide a 20mm spacer for use with a DSLR, doesn’t really make much sense to me but perhaps it’s a lot to do with how much focuser travel is available on many telescopes so maybe they just woudn’t be able to reach focus with a BF larger than 55mm? Plus there’s the issue of increased vignetting as you push the flattener further from the sensor. The TS Proline flattener that you linked to is a much better bet, plenty of BF and a wide aperture, should suit most setups. I have their 2” version for use with a TMB 80 and it works very well, currently though I am using a 100mm quadruplet and am free from the arduous task of setting up flattener spacings! William.
  2. The back of the Flat IV (the part that carries the T thread) is a fixed distance with respect to the sensor. The calibrated scale numbers around the barrel are the distance in mm from the rear of the movable glass element inside the flattener to the sensor, assuming that the distance from the shoulder of the T thread on the Flat IV to the sensor is the standard 55mm for a Canon DSLR. It’s not easy to describe the Flat IV, it would have been so much simpler if WO had bothered to provide a manual or a drawing. The way that WO intended the Flat IV to be used is with the T thread at the back of the Flat IV body screwed directly to a Canon T adaptor and attached to a Canon DSLR giving a standard 55mm distance between the shoulder of the T thread and the DSLR sensor, then, to accomodate a large range of different WO telescope focal ratios the Flat IV body is adjusted to move the internal flattener lens group nearer, or further from, the rear flattener T thread. Normally you would mount the Flat IV so that the shoulder of the T thread on the back of the Flat IV is 55mm from the camera sensor, then, adjust the body of the flattener so that the scale reads the actual BF between the sensor and the rear of the internal flattener lens group according to the WO published data for your particular telescope, i.e, for the FLT 132 set the flattener scale to read 71.5mm (+ 1/3 the thickness of the filters you use) while the distance from the shoulder of the T thread on the back of the flattener remains fixed at 55mm to the camera sensor. If you need a little more BF to accomodate the equipment you are attaching, FW, OAG, camera etc, and provided you can still reach the recommended total BF distance for your telescope then simply subtract anything over the 55mm standard BF distance from the recommended scale setting of the Flat IV. To explain, if you needed 60mm between the shoulder of the Flat IV T thread and the camera sensor to fit all the equipment in then subtract 55mm standard assumed BF from the actual used BF of 60mm gives you 5mm over-length, subtract this from the recommended 71.5mm for your WO 132 gives you 66.5mm (plus 1/3 filter thickness) to set on the body scale of the Flat IV. HTH. William.
  3. Oddsocks

    Mesu not tracking on initial testing

    Tom. If I remember correctly RS485 uses differential amplifiers in the transceivers for the RX and TX signals so Rx has it’s own separate 0v and Tx has it own 0v, they can’t share a common 0v on the signal pairs. The Sitech is RS232 and RS232 uses end-to-end cabling and doesn’t use differential amps so you only need three wires, Rx, Tx and a common 0v (and maybe +5v if the receiver amp in the device is not host powered). Besides the above, the logic levels are different with RS232 working at either 5v or 15v and RS485 working at 6v, finally, RS232 uses simplex or full duplex modes and RS485 only uses simplex or half duplex. Bottom line is that in very few cases can RS485 be directly substituted for RS232 unless the port hardware is either user or auto detect configurable and the full set of cabling is provided. Looking at the Sitech drawings and manual this appears to be an RS232 only device. HTH. William.
  4. Thank you! I think Olly is over-rating my abilities somewhat! Still, it’s appreciated. I’m retired now but spent almost my entire career working with imaging systems. Although not the same discipline as astronomy, many of the optical components I worked with share similar design principles and the knowledge gained is useful when dealing with telescope problems. Most of these problems are solvable, eventually, though not so easy and rather time consuming when your observatory is remote from where you work and live. William.
  5. Depends whether you need UV/IR blocking. With a pure mirror system and no other glass such as flatteners in the focal path then there is no need for the luminance filter as long as you refocus when switching between the RGB filters and the empty slot where the luminance filter would be. If you are using a refractor, or a reflector with a corrector or flattener in the focal path you will need the luminance filter to cut the extra focal UV/IR otherwise you will have bloated stars in the luminance channel since the UV/IR components are not bought to the same focal point as the visible wave lengths. Besides the above, for open tube OTA’s, having the luminance filter in the filter wheel as well as the RGB filters also serves to keep dust from the camera sensor for the current imaging session which may otherwise cause problems with flats if taken before/after the dust accumulated.
  6. If you are sure that the artefact is a reflection of the flattener mechanical internals you may be able to kill the reflection at source by placing field stops externally on either side of the flattener as in the attached image. For trial use artists black mounting board or plain thick cardboard painted matt black to create the field stops. Cut the field stop from the card using a compass cutter or gasket cutter, if you have one, otherwise a craft knife and scissors. The width of the field stop shoulders should be enough to obscure the flattener internal parts while leaving the optical path as clear as possible. You may need to cut a notch in the field stop closest to the OAG to avoid losing too much field of view for the guide camera. Temporarily take out one of the filters and rotate the empty slot into the optical path then look down the OTA from the prime objective end, use a torch to illuminate the camera sensor and flattener and look at the camera sensor from the edges of the prime objective, this will give you a clue how wide you can make the shoulders of the field stops so that the sensor is not obscured but as much as possible of the flattener internals are hidden behind the stops. The field stop closest the prime objective will have a narrower shoulder than the one nearest the camera. For testing fix the field stops in place with tape or blu-tack, magic putty...etc. If testing is successful fix the field stops in place semi-permanently with a few dabs of rubber cement (bicycle puncture repair outfit) or other soft adhesive that won't leave marks on the metalwork when it is time to remove them. If you want to be really accurate you can make a scaled ray drawing of the OTA and optical components and calculate the maximum sizes for the field stops but TBH the by-eye method is good enough, the worst that will happen if you are oversize is there will be slightly more vignetting or a little cut-off at the image edges, if undersize the reflection artefact may remain. Cardboard field stops will last years, the card just needs to be thick enough not to warp over time. I have made several over the years for different optical systems though once we had the right size in card we usually machined something more permanent in metal or plastic. One of my fellow club astronomers has recently made a snap-in set in black ABS on a 3D printer, attaching the stops to the focuser barrel on one side and flattener-filter wheel coupler on the other. William.
  7. Looking at the specs the Dulux Duramax High Heat seems the best choice as it is described as a “flat finish” and should dry mat, the White Knight product is described as “Low Sheen” which sounds more like a satin semi-gloss finish when dry. The Dulux is self priming too and should cling to an anodised surface but do wipe the metal first with acetone (nail polish remover) as sometimes manufacturers use carnauba wax as a sealant for the anodising dye and that remains in the pores of the anodised surface only to leach out when you apply the solvent based paint and weaken the adhesion. Watch out though not to spill or apply any acetone to plastic parts, strictly anodised metal only! Spray some of the paint inside an old jar or can and apply to the work with an artists paint brush dipped in the jar, don’t spray it directly onto the work as it is much too mobile and spreads too easily where you don’t want it.... Bunnings also stock a mat black chalkboard paint which works just as well though it is not self priming and is not so ‘clingy’ to plain un-primed anodised surfaces. https://www.bunnings.com.au/white-knight-300g-chalkboard-spray-paint-black_p1566851 Both the high temp BBQ paint and the Chalkboard paint are good suppressors of unwanted reflections in the visible and IR wavelengths, for our use in optical equipment the only real difference is the high temp paint has a harder surface that is difficult to scratch so it is good for removable items that get handled a lot such as eyepiece barrels, barlows etc and the less expensive Chalkboard paint is good for telescope OTA’s, focuser barrels, filter holders and parts that are handled rarely. I hope the reflection problem does prove to be from the anodised metal surfaces of the flattener since this is relatively easy to fix, more often it is due to back reflections from the highly reflective rejection filters and the rear glass element of the flattener where the flattener is ahead of the filters in the light path. Even though the flattener glass is treated to make it low reflectivity some light is still reflected back. In an ideal world the filters and OAG would be ahead of the flattener in the light path but this is not so easy to achieve and not suffer vignetting or flattener to sensor spacing problems. William.
  8. A couple of extra points to check. Look at the central spindle in the filter wheel and make sure that the carousel is tightly held. The carousel should turn easily but should not appear ‘floppy’, for want of a better description. The carousel should hold the filters perfectly perpendicular to the optical axis, if the carousel is loose on it’s spindle this would shift any internal reflections from the filters off to one side and of course the position of any reflections would be highly variable depending on the tilt of the carousel under different OTA attitudes. The second point to check is the back of the pickup prism/mirror at the end of the OAG stalk. Look at the side of the OAG prism/ mirror that faces the main camera sensor, it should be blackened, if not you may see an off-axis reflection of the OTA baffles bouncing between the filters, back of the prism, and into the main camera. If your OAG is assembled correctly the pickup prism/mirror should be central to the long edge of the main camera sensor and that is where any reflection would be present if this was the cause however since we don’t know where the OAG pickup is located on your system this is worth checking if only to eliminate it from the list of possibles.... William.
  9. You have two separate issues to deal with. The artefact is a reflection of component(s) in the image path but the reflection is so far off centre that something is misaligned, the optical path is not collimated correctly. Has the problem been present since you began using the telescope or since you changed one of the components? Looking at the images you posted so far show a variable amount of tilt from virtually none in the first post to ~16% in the last, the stars in the lower left show tilt distortion quite clearly. Most likely this tilt is due to slop in the nosepiece fitting of the WO Adj.FlatIV when it is clamped in the FT focuser and the variability is down to the amount of tilt present as the attitude of the OTA is changed . You may need to find a way to improve the rigidity of the clamping so that when the WO Adj.FlatIV is slid into the focuser draw tube it can not wiggle and tilt as the draw tube clamp screw is tightened. Try wrapping a piece of the very thin, transparent, flexible, hard-plastic packing foil that is used in supermarket food packaging, around the nosepiece barrel of the WO Adj.FlatIV as it slips into the focuser draw tube, so that it can not rock from side-to-side. You will have to experiment with different thicknesses of plastic (or other materials) to find a suitable thickness of material that can wrap a single complete turn of the WO Adj.FlatIV barrel so that it is held tightly and axially central to the focuser draw tube and cannot tilt as the clamping screw is tightened. You may find the draw tube of the FT focuser has adjuster screws either side of the central clamping screw (where it pushes against the brass compression ring) so that excessive slop can be taken up for whichever nosepiece is inserted into the draw tube. Note that when you use a wrapper around the nose barrel of the WO Adj.FlatIV then the safety undercut in the nosepiece is no longer able to secure the flattener, and the rest of the image chain, from falling out of the focuser draw tube so for safety a lanyard cord should be tied around the camera and filter wheel up to the tube rings with just enough slack so that the focuser can be moved into focus but the imaging equipment can not fall to the ground if the WO Adj.FlatIV slips out of the focuser draw tube during use. This 'sloppy' fit of the WO Adj.FlatIV in the focuser draw tube is not uncommon as the fit tolerances for the 'standard' 2" focuser vary so much between manufacturers and the larger dedicated WO flatteners that screw directly to the threads on the standard WO focuser are a better solution however since you have invested in the Feather Touch then adding packing around the flattener nosepiece is the only simple remedy and is one that I have used in the past. Both hard plastic packaging foil and self-adhesive copper foil work well (available from garden centres and used to stop slugs and snails climbing plant containers, or from electronic component suppliers and used to repair printed circuit boards). Once the reflection artefact is centred then the source of the reflection can be located. If you look carefully you can see that the 'artefact' actually covers almost half the image. This may be multiple reflections between the filters and the flattener or it may be an image of the OTA baffles, either way, the next step is to put the image system into its basic configuration. Remove the flattener and couple the camera directly to the telescope. Ignore the coma , is the artefact still there? If the artefact has disappeared with the flattener removed then you can be sure the artefact is due to refections between the filters and the flattener, or flattener and sensor, I can't remember if the WO Adj.FlatIV is just black anodised or painted with non-reflective black paint. If black anodised you may need to overpaint any visible metal surfaces with blackboard paint or high-temperature mat-black BBQ paint (pigment based paint). If the artefact is still there with the flattener removed then it will be more of a problem to pin down the cause as it could be a reflection between the filter and the prime objective or between the filter and the camera sensor. If the artefact is still present with the flattener removed try taking out one of the filters from the carousel and image through the empty slot, is the artefact still there? Check the unmounted filters are inserted into the carousel pointing in the right direction, some manufacturers have an arrow, or some other marker, on the edge of the filter that shows the side that should point towards the sky. If the filters are mounted facing the wrong way round then strong reflections can occur between the camera sensor and the filter, or, between the filter and flattener. The fact that the reflections are slightly different between filters may be that some are pointing the 'right' way and some are pointing the 'wrong' way. Check also that the filters are sitting flat in the carousel and can not move or tilt, additional spacers may be needed beneath the filters where they sit in the carousel recesses, you would need to refer to your filter wheel manufacturers handbook and the filter thickness of the filter type you are using to determine if additional spacers are needed, the filters should be held firmly in the carousel and not be slightly loose or able to lift/tilt. Which camera and filter wheel are you using? I read on the Diffraction Limited forum recently that one of their SBIG camera - FW - filter packages left the production line with a bare metal base plate between camera and FW, it was missing the black anodising stage and causing reflections inside the camera. Double check by visually inspecting all the components in the optical path that all metal surfaces are correctly blackened and that no bare metal is visible anywhere. Hopefully the above will give you a few things to eliminate from the process of identifying possible sources of the artefact. William.
  10. Diagonal banding in CCD / CMOS detectors is nearly always caused by interference from an electronic source whose frequency is close to the clock readout frequency of the detector. Since you have eliminated the external power supply and see this with internal battery only then you have ruled out external sources and all that remains is something inside the camera. If the issue appeared immediately after the camera was modified I would suspect a possible problem with the internal ribbon cables connecting the various boards inside the camera so that a ground connection is missing, maybe the ribbons are not fully homed in their respective sockets etc. Of course it might just be coincidence and nothing to do with the mod at all and a component has failed on one of the boards causing the problem. If the camera modifier is no longer working on these cameras and you are not able or willing to pull the camera apart yourself perhaps a chat to a Canon service agent might be worth investigating ? HTH William.
  11. It might be that your dark frame library has been contaminated, a small light leak into the telescope during dark library creation can result in the darks having too high a ‘dark’ current, leading to over-correction when applied to the live image in Starlight Live and resulting in a ‘blank’ image. Try creating your dark library with the camera off the telescope and the camera port covered with the black rubber transport cap, if you still have it, as well as a few layers of dense fabric to ensure absolutely no light is entering the camera. The main problem with using a dark library in conjunction with the Ultrastar and Lodestar is the lack of temperature regulation of the sensor so dark libraries are not always that effective unless the sensor temperature during EAA live viewing closely matches that when the dark libraries were created. As a test, next time you are using Starlight Live for EAA under observing conditions don’t use your existing dark library but cover the telescope and take a new dark stack of at least ten frames then switch to viewing, do you now see the live image normally? Lastly, if you inspect your Starlight Live acquired dark libraries in different image processing applications be aware that some may change the image format when saved from unsigned to signed integer, floating point to non-floating point etc and this will render these dark libraries unusable in Starlight Live with similar results that you have reported, probably not relevant in this instance but worth mentioning, if you do open the Starlight Live dark libraries in a different app for viewing do not ‘save’ when closing. William.
  12. The 3D image shows the the spacing is not quite right, almost there, the corners are pointing down which shows overcorrection for coma, without a coma corrector the corners would be pointing up. Try a series test removing 0.5mm spacer from the FF distance and a second series test with 0.5mm added to see which way you need to go, if at all. The result will never be perfectly flat though, as the corners come up the whole flat plane tends to curve so you have to accept a compromise somewhere. The tilt direction makes a significant difference to the image, if the tilt is across the short axis, as in your image, the resulting stars at top and bottom won't show much distortion, if the same 9% tilt was across the long axis then the stars at the either end of the axis would show more distortion, the tilt direction and it's magnitude work together in the effect you see in the image and reflectors are very difficult to control in this respect as the main mirror will shift slightly in the mirror cell with pointing angle. A square detector is relatively easy to achieve a good result, an oblong sensor is harder since the tilt direction has a big influence across the full width of the image. Tilt and curvature work hand in hand in the effect they have on the image extremities with both factors almost having a multiplicative relationship. The best position for measuring and making adjustment is with the OTA pointing up to the zenith so that he mirror is laying flat in the cell, make your measurements in that position and any adjustments to spacing then test at approx 45% elevation either side of a meridian flip. If the 45 degree test shows significant tilt, and you can see the effect in the images, then you will off on the trail of 'Hunt the Sag'. Refractors are much easier to achieve consistent results from one session to the next in this respect. In the end it just comes down to what your expectations are and whether you can really see a problem with your images. The 'Tilt' measurement is not directly related to mechanical tilt and this causes new users of CCD inspector a lot of unnecessary angst, tilt is a measurement of the distortion of the FWHM profile of all the measured stars in the image that have the distortion lying in a common plane and periodic error, tracking problems, drive vibration etc can all show as 'tilt' when in fact there may be very little, so keep the exposures as short as possible to minimise this effect and ideally the images should only be luminance filtered, no narrow band or RGB and avoid any large areas of nebulae in the image. Using the lowest overall FWHM scored images will yield the most accurate results, the hard part then is deciding if any residual tilt is from mechanical or optical collimation sources (or both!). HTH.
  13. CCD inspector can give quite variable results for many reasons, thermals, pointing, tracking, seeing etc, etc. The trick is to load at least ten single images, exposure time as short as possible, taken a few minutes apart and with small changes in pointing then select them all simultaneously for evaluation, CCD inspector will output the average of the selected images thereby minimizing random variability. When choosing which images to add to the group measurement use those that show the smallest FWHM score, click on the FWHM column header to sort the loaded images by score, choose the best and remove the worst then select all the remaining for averaging. Use the 3d view to get a qualitative indication of curvature together with the 2d view for the quantitive report. I have found Live Adjust can be a bit unstable with big DSLR images, works well with conventional CCD images that don't need RAW conversion, have never had much luck with Live Adjust with a Nikon but QSI and Starlight Xpress FITs images work, maybe worth posting on the dedicated CCDWare forum to see if this is a known issue and what the answer may be. HTH.
  14. Hi Alan. My quick test is not really a direct comparison because I think CKemu’s posted image is from a Hydrogen Alpha solar telescope, so primarily only the red pixels should be active, though I have no real idea under what conditions the image was produced, how much light leakage into the optical path, exposure time, gain setting, thermal dark current etc, whereas my sample images were taken in white light illuminating a dark red object at just 2ms exposure time and minimum gain. A real test would be to compare a white light image of a deep red object at similar camera settings with the samples from my MM and MC cameras. It just seemed that CKemu’s image looked so much like a bayered image when captured in mono mode to be just random chance. An interesting problem nonetheless. William.
  15. I have the same two early series ASI120 cameras as you, 120MM and 120MC Comparing your Ha image in the opening post against two images I took this evening in white light, using MaxImDL for capture with mono camera selected for both MC and MM, it looks as though it might be possible you have a colour detector that has had the mono firmware loaded, though as I don't know how much you stretched the image I can't be really be sure. My MC image in white light won't be exactly the same as your Ha of course since you will only be recording primarily in the red while I was capturing in red green and blue. A really quick test you can do in daylight is to remove the camera from the telescope, do not use the supplied wide angle lens just use the camera with the sensor exposed and point the camera at a brightly lit primary coloured object, red, blue or green, held a few centimetres in front of the sensor and in live view mode look at the histogram display. A monochrome sensor lit with a primary colour will show a histogram that contains just a single peak, as in the image attached below, a colour sensor will show two or three separated histogram peaks when lit with a primary colour, also shown below. It is not beyond the realms of possibilities that during a production run a colour sensor board ended up being flashed with the mono firmware and labeled as such. Another quick test you can do is to look at your MM and MC side-by-side, I really wanted to post a picture for you but my camera just won't focus closely enough so a description will have to do, tilt the camera so that a bright light is reflecting at a sharp angle off the sensor so that you see the refection of the light in the sensor, the colour sensor is considerably darker than the mono sensor when the angle of reflection is the same. If both the sensors look around the same brightness that is another indicator that they are both colour sensors. I final test might be to download the ASI120MM and ASI120MC firmware from ZWO's website, they still have the firmware load tool and both the MC and MM updated firmware for the early versions of the ASI120MM/MC. It would be interesting to load the MC firmware, connect the camera and wide angle lens and see if it captures a normal colour image, if so that proves you have a colour sensor in a camera pretending to be a mono. if not, then reload the mono firmware. AFAIK the only difference between them is the device ID string that tells the capture software whether a colour or mono camera is connected so that it knows whether to debayer the image or not. I must warn though that reloading flash firmware is not without its risks, as flash memory frequently fails during erase and load operations, as long as you are aware of the risk it might be something to consider. I have re-flashed both my MC and MM cameras, the later firmware is supposed to help with the capture lock-up bug and blue-screen-of death-problems on Windows 7 64bit that the early cameras had. Comparison image below: HTH William
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