Odd one Rodney. I have never seen CCDstack behave like that before with
multiple scopes.
Are you using the silly Tak mounting clamshell?
If so after some more tests I would think you’d be better off with a set of rings.
I used SoCal rings in my FSQ. ADM make rings as well.
Flexure is the likely culprit. You’re not there yet with that.
Joshua, Greg - answers to your questions and more information:
Attached are snaps of my imaging rig. We have:
* FSQ106 -> Feather Touch Focuser -> mechanical adapters -> QSI683
Note: no reducer in image train
* Orion 80mm F5 guide scope -> ASI120 mini guide camera
* Parallax tube rings on both OTA and guide scope
* Skywatcher EQ8 equatorial mount
"So, all you did between these two image is a meridian flip?"
Yes
"To me, image ....23456 is much softer than the other, almost out of focus I would say, but I see there is only minutes between the images, same temperature and the same focus position." I noticed this as well.
"Without shifting anything, can you take 2 or 3 images on a row of, say 60 sec exposure or less, pointing more or less east about 45 deg altitude, then flip the meridian and do the same pointing west, don't rotate the camera." Worth a shot - will do.
"In your last post, you rotated 90 deg, is the rotator after the focuser?"
No, it isn't. See attached image of the focuser showing where the manual rotator (captains wheel) is on the Feather Touch focuser. The arrow is indicating the point of rotation. The only thing between there and the OTA is the adapter that screws on to the OTA tube.
"Are you using the silly Tak mounting clamshell?"
Yuk - no . Parallax tube rings all round.
So the summary of all this is that the consensus seems to be that the issue is flexure and is not with the OTA. I still have an open mind on this and will continue to explore further. I would rather have the issue being flexure as this is something that is more under my control. However, the logic behind the camera rotation test indicates that the problem lies on the OTA side of the rotation point and I cannot ignore this.
Being new moon now of course the weather forecast for the next three days is overcast so it may be a few days before I can get back on to this.
I've done forensics on two problematic Taks so far, one being an FSQ106, and I found borth Captains wheel rotators to be seriously unreliable for maintaining proper alignment.
Last edited by Stefan Buda; 11-02-2021 at 11:26 PM.
I've done forensics on two problematic Taks so far, one being an FSQ106, and I found borth Captains wheel rotators to be seriously unreliable for maintaining proper alignment.
Rodney's Tak doesn't have one. He has a camera angle adjuster (CAA). Did you have issues with these as well? I have one on my old Q. It's pretty tight machining. Nearly as tight tolerances as a bearing pressed in a bronze bush. That's how it felt when I took it off and put it back in.
I wouldn't be surprised to find out that what Stefan says about the captain's wheel, to be true, if you're using one. On the other hand, I've done tilt measurements on a CAA from someone else, and found there to be untreatable tilt/movement in it, with it being fully tightened up. You need something that locks down in the same position every time, especially when pixel peeping
I'm not running with the Tak CAA Greg. I've swapped out the entire Tak focuser with the Feather Touch unit and did not re-install the CAA.
Oh sorry, I thought you left it in.
With the Feathertouch its worth knowing th escrew undeneath the focuser is a lock not a tension adjusting screw. One post here on IIS mentioned they damaged their focuser thinking it was a focuser tension screw.
Feathertouch focusers are great but not perfect. I remember Yuri from TEC Telescopes testing their FT 3545 focuser. Upside down it had less flex than right side up so it can move slighty. Worth checking. Is there any slight movement in it if you grab the end of it and apply some force with your hand - is there any give? Make sure its correctly tensioned up.
I have had a few FT focusers and never had an issue with them. They are also beautifully made. But really the best focusers I have used are the AP ones.
Stainless steel drawtube. Never seen anyone else do that. My car would not dent or flex that! Not that this helps you.
If you shake the scope a bit do you hear any lenses rattling?
Why don't you ask Claude for his opinion?
Are your filters well secured and can't lean forward? I saw an issue once with 1mm thin filters leaning forward and giving odd results.
Are you using threaded adapters to attach your camera? Try grabbing your camera and see if there is any give.
Yeah... I'm sorry but some people are just a liiittle too perfectionistic he he . The amount of aberration present in that "before" shot would be unnoticeable in a final image after a a multi frame additive process across the sky, especially if a meridian flip is incorporated...
Still, if you can be bothered and are not worried about pulling your $8K scope apart a little ... hey, knock yourself out I suspect nobody will notice the improvement unless you pointed it out with close up comparisons
That said, given the seemingly fickle vulnerability to the phenomena, sounds like there would be a lot of FSQ's out there that would suffer from this very minor, variable aberration issue caused by slightly miss aligned elements... but it is all but invisible in final images.
Thanks Greg and Mike for continuing the discussion on this. I've finished grabbing a basket full of data on an area around NGC3293 with the QSI683 camera running on the FSQ106 and have started the processing on same. From initial inspections it does appear that the aberrations won't make their way into the final image. I will leave it to others to inspect, pixel peep, and see what can be found
Having said that, the QSI683 camera is much kinder to this scope than my new ZWO ASI6200 so we may not have heard the end of this story yet. I do agree though that we can get hung up on the minutia at times and the real test is what we finish up with on the screen. Any image that passes the discerning gaze of the viewer on this forum is doing well.
True, but in Rodney's case the defect is visible and unlikely to be invisible in the final image.
It may be that one or more of these lens adjusters may be a tad loose allowing an element a freedom of movement it should not have.
Greg.
Yeah probably, I was mainly commenting on the CN thread ...but I am not suggesting one shouldn't pursue improvement, but like the obsessive compulsion to get absolutely perfect polar alignment (if that even exists) especially by those with high end mounts ...when all they want to do is point at one object each night and track it for hours So, whether a target lands 1, 5 or 10 arc min from centre of the FOV after a GOTO, is of no importance what so ever... ...but they will hammer away and not take images until those PA numbers are perfect ....or worse essentially never image at all
Thanks Greg and Mike for continuing the discussion on this. I've finished grabbing a basket full of data on an area around NGC3293 with the QSI683 camera running on the FSQ106 and have started the processing on same. From initial inspections it does appear that the aberrations won't make their way into the final image. I will leave it to others to inspect, pixel peep, and see what can be found
Having said that, the QSI683 camera is much kinder to this scope than my new ZWO ASI6200 so we may not have heard the end of this story yet. I do agree though that we can get hung up on the minutia at times and the real test is what we finish up with on the screen. Any image that passes the discerning gaze of the viewer on this forum is doing well.
Best,
Rodney
Look forward to checking out the final result Rod ...as long as there are no worms
Yeah probably, I was mainly commenting on the CN thread ...but I am not suggesting one shouldn't pursue improvement, but like the obsessive compulsion to get absolutely perfect polar alignment (if that even exists) especially by those with high end mounts ...when all they want to do is point at one object each night and track it for hours So, whether a target lands 1, 5 or 10 arc min from centre of the FOV after a GOTO, is of no importance what so ever... ...but they will hammer away and not take images until those PA numbers are perfect ....or worse essentially never image at all
Mike
Yes there are those on CN that seem to complain about extremely minor defects. I am sure the Tak distributor in the US is familiar with them.
But these new small pixelled CMOS cameras like the ASI6200 and QHY600 full frame sensors are mercilous in showing up defects. Seemingly more than the % difference in pixel size with the larger pixelled cameras.
I suppose if there was a full frame version of the 4.54 micron KAF8300 we would have seen some complaints then as well.
But if you lose sight of the real purpose of imaging, which of course is to take as good an image as you can, then yeah you've lost the plot.
I've grabbed sufficient data with the FSQ106 now with both of my cameras (QSI683 and the ASI6200) to produce results that I believe I will be happy with. The optical aberrations that show up with image registration are small enough to get evened out during image calibration, registration and integration. The QSI683 is much kinder to this this scope with the larger pixels and smaller sensor though it is obvious when collecting data with the ASI6200 that there is still some work to do.
Capturing data with the ASI6200/FSQ106 initially showed definite tilt issues but I've managed to even this out quite a lot using the Gerd Neumann Camera Tilting Unit (CTU) that I have in the image train. It is easy to use as the adjustment screws are on the outside of the unit and easily accessible whilst watching the screen and downloading images. Whilst I have some work to do yet, I am pleased with the results so far.
Refer to this post for my first published image taken with this combination.
. Parallax tube rings all round.
so it may be a few days before I can get back on to this.
... hey, knock yourself out 
I suspect nobody will notice the improvement unless you pointed it out with close up comparisons 
...when all they want to do is point at one object each night and track it for hours 
So, whether a target lands 1, 5 or 10 arc min from centre of the FOV after a GOTO, is of no importance what so ever...
....or worse 
