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angryowl

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Everything posted by angryowl

  1. angryowl
    Appreciate all the help on this Steve and look forward to hearing their opinions as to what may be causing this.
  2. angryowl
    You’re absolutely right and many thanks for pointing that out. This was a mistake on my part as I should have clearly mentioned that a 600s exposure also looked sharp on the refractor. I think I was a bit tired and frustrated when posting those tests, but still that’s no excuse.
  3. angryowl
    Just tried this and the back aluminium mirror holder is rock solid with not even the tiniest movement detected when pulled and wiggled. Additionally, all screws are completely tightened and no play whatsoever there so I think this can safely be eliminated.
  4. angryowl
    Well, for one the clouds were starting to roll in when I mounted the refractor so I thought I'd get as many in as possible and two, I couldn't fit any filter inside the imaging train and stupidly thought that 600s exposures on the frac would oversaturate stars, making results harder to interpret. Only then I had realised that I was imaging at F11 which is an entirely different ballgame from F2.2. I had taken one 600s exposure on the frac I think but not kept it, but I can tell you the stars were as pinpoint as those in the 300s exposures. On the RASA I only took 600s exposures as that’s probably the longest I’m ever going to go and my latest astro images have all had 600s subs.
  5. angryowl
    Just thinking about this gives shivers down my spine... Really do hope it's not this and something else easily fixable, but that's just wishful thinking at this point.
  6. angryowl
    Much appreciated all of the input here... @Davey-T – Trust me, I’ve too been doing a lot of reading regarding SCT mirror flop and it should only ever be as apparent as what I’m seeing during a Meridian flip, but not during a normal exposures. That bit you said leaving the locks slightly loose to allow tiny focus motions during imaging runs I think I heard somewhere else and is very interesting. A loose element inside the 4 element secondary was suggested a few posts up by @michael8554 and I had considered this before, but as I said that would have, I think been easy to spot as it would have produced all sorts of optical aberrations in my stars. Still at this point in time this could be a possibility, but how to test for this without taking the corrector plate apart? hmmm. The issue presented itself with both a flexible Astrozap, DIY aluminium dew shield and no dew shield at all on the OTA. The dew shields were all secured in place properly so I doubt that’d be it, but a good shout indeed. I have been told David Hinds would be the person to contact in such situations regarding Celestron issues within the UK. Is this correct? My thinking was that FLO being the distributor and place I purchased the OTA from, are the first point to go to when one feels something is off about equipment, but I don’t mind directly contacting the Celestron folk in trying to better understand what I’m dealing with here. @vlaiv– I completely agree with your points on the mirror cell about it not being secured in place, that makes a lot of sense. Regarding the front corrector plate, I could never find/hear/feel any movement of the corrector plate whenever I screw/unscrew my camera. I realise you’re referring to the smallest movements here, but as you say this would result in the camera/secondary no longer being orthogonal with the primary thus resulting in odd stars at one corner and not the others. I can definitely check the screws going round the aluminium mirror block to see if any are loose or have any play. Will do so today and report back...
  7. angryowl
    Thanks for that Michael, hopefully the RASA lock mechanisms work in a similar fashion. I agree, looking through the images, engaging the mirrors only make a small difference it seems and I'm not sure what to think of this. As to a conclusion I simply don’t know at this point, as you put it may be a combination of the heavy OTA hanging off the mount sagging due to gravity and the mirror itself sagging and flexing. But then again could be something else. Hoping someone more knowledgeable than me might see something or suggest something I may try that I haven’t before. One thing I know for sure is that the Mesu 200 mount can be eliminated from the equation as it can track splendidly and provides fantastic results even at a relatively long 900mm FL as the tests showed.
  8. angryowl
    Oh and a question I've always been meaning to ask; on the EdgeHD/RASA scopes, do the mirror locks lock the mirror itself in position or just the focuser? Reason I'm asking is I've read somewhere that they only lock the focusing mechanism in position and not really affect the mirror at all?
  9. angryowl
    An interesting one I thought was this single 300s exposure last night with the scope pointing NW at a high-ish elevation. 600s unguided mirror locks fully engaged.
  10. angryowl
    Last nights’ results: All of the usual stuff, then quickly mounted the refractor on to test I was still getting pinpoint round stars in 300s exposures, which I was. Mounted the RASA similarly to the night before with no changes WHATSOEVER and here are the results: Pointed near Procyon, here’s an unguided 600s exposure with the mirror unlocked: Pointed near Procyon, here’s an unguided 600s exposure with the mirror fully locked: Pointed near Procyon, here’s a guided 600s exposure with the mirror unlocked: Pointed near Procyon, here’s a guided 600s exposure with the mirror fully locked:
  11. angryowl
    On Tuesday @Davey-T generously lent me his 80mm 900mm FL refractor to test and when got home I set up as usual. Done a proper three-point balance as I do with my RASA and got it spot on. Polar aligned within 30 or so arc seconds using SharpCap, and got Stellarium and SiTech up and running, and after a one star alignment I was up and imaging. I didn’t have a Bahtinov mask for the scope so hand focusing for testing worked fine. Here are the results: Ignore the triangular-shaped stars the frac as they're a result of the retaining rings holding the lens. Scope on East side of pier pointing SE roughly 50 deg elevation 300s UNGUIDED (two consecutive exposures presented) Scope on East side of pier pointing South roughly 50 deg elevation 300s UNGUIDED Scope on West side of pier pointing South roughly 50 deg elevation 300s UNGUIDED Zenith 300s UNGUIDED Took the refractor off the mount and without changing ANYHTING I mounted the RASA, these are the results for the same parts of the sky: RASA on East side of pier pointing SE roughly 50 deg elevation 600s UNGUIDED RASA on East side of pier pointing SE roughly 50 deg elevation 600s GUIDED with the 60mm scope RASA on West side of pier pointing South roughly 50 deg elevation 600s UNGUIDED RASA on West side of pier pointing South roughly 50 deg elevation 600s GUIDED with the 60mm scope Apologies for the lengthy post, but I figured images of more parts of the sky might help with better understanding what’s happening here. A report of lest nights’ results will follow shortly.
  12. angryowl
    This had crossed my mind, but I think it may well have shown in the stars in the image as weird aberrations.
  13. angryowl
    Yes, it looks like the next step is trying a refractor on the mount and see where that puts me. As to the changes made since I was getting good stars with the scope, there are none, except for an aluminium dew shield and routing the cables round the scope differently. I completely understand that it’s hard to pinpoint defective/faulty equipment and I most certainly don’t want to jump to the conclusion that the scope is at fault here, but I’ve been looking at this for months now and all that’s left in the equation is the OTA itself. That being said, my desire is not to return or replace the scope as it’s fantastic otherwise and simply outstanding optically, I just want to get to the bottom of this and find a fix so I can get back to imaging.
  14. angryowl
    Appreciated Dave and by the looks of it I might have to take you up on that as this may be a definite way of excluding the mount as being the culprit here.
  15. angryowl
    That's a good test to perform next time I'm out and I remember once I forgot I had the mirror locked and tried to turn the fine focus knob a bit and it only rotated like three quarters before it became apparent that something was stopping it and would not go further.
  16. angryowl
    So, the conclusion is that the drift I'm seeing cannot be caused by anything else but the mirror itself flexing. Could the mirror locking mechanisms themselves be faulty? And as this cannot be fully locked down there will always be movement in the mirror resulting in drift in longer exposures. When I purchased the scope, I was under the impression that the mirror can be fully locked down if need be. Also, how can it be explained that I had been getting round stars in 5 minute exposures just after purchasing the scope in roughly the same parts of the sky that I now get elongated stars? Could it be that the grease used on the mirror shaft degraded and now shifts a lot more than it did before? So, the only solution for me at this point would be to use an OAG at the front of the scope which would cause havoc in my images. If any RASA imagers chime in here with details of their setup and exposure lengths and how they deal with this mirror movement between exposures would be much appreciated.
  17. angryowl
    A comprehensive email has been sent to FLO explaining the situation and we shall see what the response is and what the next steps may be. Will regularly update this thread once I know more or as new developments arise. Will also like to thank everyone who took the time to read through and provide advice and assistance., much appreciated.
  18. angryowl
    Ah, my bad entirely. Makes total sense now. Mind you, just had my morning coffee so still not up to full speed ?
  19. angryowl
    Valuable piece of information right here! I've never done this as always thought once the mirror was locked any movement in the focusing knobs, even the fine one, might strip something inside the focuser or mess with other things. This is very good to know as I currently focus with a Bahtinov mask and with the mirror unlocked it's a lot of going back and forth to reach proper focus with all that backlash in. I will definitely try this next time I'm out.
  20. angryowl
    Hi Ron, appreciate the input on this A very good mention indeed and have thought about this several times. I thought maybe with time the grease they used lost some of its properties and turned more liquid, or just performs worse and as you say allows the mirror to ever so slowly sag. Again, you’re correct in saying that if it is indeed this, it would explain the varying in direction drift seen throughout different parts of the sky. I always end all of my focusing runs pushing the mirror up and once in focus never go the other direction. Your statement regarding racking the focuser in both directions to get the grease around both parts makes sense, but wouldn’t that still eventually cause the mirror to sag, albeit slower, but still sag? I may be wrong on this though. The amount of backlash in the focusing mechanism/mirror mount when reversing focus is quite large, I would say. Never measured it in terms of pixels, but I think it’s considered common with all SCTs?
  21. angryowl
    Wow, this is such an incredible offer Dave. You're right, trying a refractor will surely eliminate any potential mirror movement or anything like that. Plus, my Atik has a T2 thread and would have plenty of adapters to reach focus if need be. Just thinking what my options with the RASA would be if a refractor gives good results; Parallax rings, finding a way to mount it more sturdily or just smashing the thing to bits for the sheer joy of it.
  22. angryowl
    Hehe, much appreciated mate, but you've done more than enough by borrowing me the OAG which has highlighted some interesting things.
  23. angryowl
    I completely get your point of view Steve, but is differential flexure what we’re seeing here? I thought differential flexure was the main scope flexing in a different manner than the guidescope thus the latter not correcting the drift properly. However, I’m getting image drift over unguided relatively short exposures from the RASA alone. Would this not indicate something flexing/sagging in the scope/mirror/saddle assembly or mounting points? I’m just trying to understand how other imagers using the RASA can image unguided, which is a main selling point for the scope, and get acceptable results. Is it due to them using CCDs with larger pixels resulting in larger image scales making the drift less apparent?
  24. angryowl
    Well, I don't have anyone to borrow one off from so no, don't think that's an a option at the moment.
  25. angryowl
    No, not yet, as I wanted to be as sure as possible it was something to do with the scope as I hate wasting peoples/suppliers time when in fact it may well be something else entirely. Will reach out to them tomorrow, but given their reputation I'm sure they'll be more than helpful in resolving this.
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