Takahashi FSQ85 owners, I need help……please….☹️

Hello all,
I am really struggling and am wanting help form any Takahashi FSQ85 owners, now you guys will know that these  scopes don’t play nice with modern small pixel cameras, such as my QHY268m and 268c cameras with 3.76 micron pixels, so Tak bought out a new corrector for this issue and it’s not included with the scope when you buy it new, well mine was made the year before they were supplied with the new corrector, so I have now bought it.

so before when I mages with this scope and camera combo I had bad astigmatism in the outer 1/4 if the image, with cross like star shapes, which apparently was normal for this scope and small pixel camera, now after fitting the corrector, it’s much better, but it’s still there when you zoom in in the image, albeit not as bad, but still there, so why is this..? I have used the correct 56.2 backspace plus 1/3 of my filter thickness, ..??

would the corrector not work properly if the spacing is wrong, and what should I see, if anything the corrector is too close, maybe 0.1mm would this really make a difference….I just expected it to be much improved and it’s not….☹️

so any advice of if you have some un cropped images taken with your set up with this scope and the 1.01x flattener, I would like to compare to mine…

Help appreciated 
Stewart

Hello all,
I am really struggling and am wanting help form any Takahashi FSQ85 owners, now you guys will know that these  scopes don’t play nice with modern small pixel cameras, such as my QHY268m and 268c cameras with 3.76 micron pixels, so Tak bought out a new corrector for this issue and it’s not included with the scope when you buy it new, well mine was made the year before they were supplied with the new corrector, so I have now bought it.

so before when I mages with this scope and camera combo I had bad astigmatism in the outer 1/4 if the image, with cross like star shapes, which apparently was normal for this scope and small pixel camera, now after fitting the corrector, it’s much better, but it’s still there when you zoom in in the image, albeit not as bad, but still there, so why is this..? I have used the correct 56.2 backspace plus 1/3 of my filter thickness, ..??

would the corrector not work properly if the spacing is wrong, and what should I see, if anything the corrector is too close, maybe 0.1mm would this really make a difference….I just expected it to be much improved and it’s not….☹️

so any advice of if you have some un cropped images taken with your set up with this scope and the 1.01x flattener, I would like to compare to mine…

Help appreciated 
Stewart

I have the FSQ-85EDX (with the 1.01 flattener incl.). I run it currently on a QHY600M. Exactly matching back focus is certainly critical. So is tilt. I have a tilt adapter in the image train and after some fiddling it is now quite good in the corners. Your calculation of 56.2mm + 1/3 filter thickness is correct. (i currently do not have an un-cropped image published here but will do so in a few weeks when my current target is completed). CS, John
(P.S.: I do have an un-cropped FF image but that was with a 5.36u EOS R: https://www.astrobin.com/sha3ff/C/ )

Andy Brown:

Hello all,
I am really struggling and am wanting help form any Takahashi FSQ85 owners, now you guys will know that these  scopes don’t play nice with modern small pixel cameras, such as my QHY268m and 268c cameras with 3.76 micron pixels, so Tak bought out a new corrector for this issue and it’s not included with the scope when you buy it new, well mine was made the year before they were supplied with the new corrector, so I have now bought it.

so before when I mages with this scope and camera combo I had bad astigmatism in the outer 1/4 if the image, with cross like star shapes, which apparently was normal for this scope and small pixel camera, now after fitting the corrector, it’s much better, but it’s still there when you zoom in in the image, albeit not as bad, but still there, so why is this..? I have used the correct 56.2 backspace plus 1/3 of my filter thickness, ..??

would the corrector not work properly if the spacing is wrong, and what should I see, if anything the corrector is too close, maybe 0.1mm would this really make a difference….I just expected it to be much improved and it’s not….☹️

so any advice of if you have some un cropped images taken with your set up with this scope and the 1.01x flattener, I would like to compare to mine…

Help appreciated 
Stewart

Hi Stewart,

I've had my Baby-Q for just over a year and corner stars can be a problem, as John has said, the backspacing is fairly critical and also tilt from the rotator (if yours has one) and the focuser. I've invested in a Gerd Neuman Tilt Adjuster which I'm hoping will solve my issues but I've not yet had time to play with it. I'm also using the 0.73x reducer with a 294mm-pro but the flattener should be better, even with an APS-C size sensor.

CS,

Andy

Thanks for the reply,
we’ll tilt is not the issue here, as my camera had a very small amount which was sorted, it was I let about 20 microns out in one corner, the other two corners were pretty much perfect, also tilt would not manifest with these shaped stars, this is astigmatism,  it’s almost like the flattener is not here at all, as it’s not much better than before I put it on, I just wish I knew what it was….

you say you have a tilt adjuster, so what do your stars in the corners look like before you have adjusted for the tilt, to see if they look like mine do…

Andy Brown:

Andy Brown:

Hello all,
I am really struggling and am wanting help form any Takahashi FSQ85 owners, now you guys will know that these  scopes don’t play nice with modern small pixel cameras, such as my QHY268m and 268c cameras with 3.76 micron pixels, so Tak bought out a new corrector for this issue and it’s not included with the scope when you buy it new, well mine was made the year before they were supplied with the new corrector, so I have now bought it.

so before when I mages with this scope and camera combo I had bad astigmatism in the outer 1/4 if the image, with cross like star shapes, which apparently was normal for this scope and small pixel camera, now after fitting the corrector, it’s much better, but it’s still there when you zoom in in the image, albeit not as bad, but still there, so why is this..? I have used the correct 56.2 backspace plus 1/3 of my filter thickness, ..??

would the corrector not work properly if the spacing is wrong, and what should I see, if anything the corrector is too close, maybe 0.1mm would this really make a difference….I just expected it to be much improved and it’s not….☹️

so any advice of if you have some un cropped images taken with your set up with this scope and the 1.01x flattener, I would like to compare to mine…

Help appreciated 
Stewart

Hi Stewart,

I've had my Baby-Q for just over a year and corner stars can be a problem, as John has said, the backspacing is fairly critical and also tilt from the rotator (if yours has one) and the focuser. I've invested in a Gerd Neuman Tilt Adjuster which I'm hoping will solve my issues but I've not yet had time to play with it. I'm also using the 0.73x reducer with a 294mm-pro but the flattener should be better, even with an APS-C size sensor.

CS,

Andy

Thanks for the reply,
we’ll tilt is not the issue here, as my camera had a very small amount which was sorted, it was I let about 20 microns out in one corner, the other two corners were pretty much perfect, also tilt would not manifest with these shaped stars, this is astigmatism,  it’s almost like the flattener is not here at all, as it’s not much better than before I put it on, I just wish I knew what it was….

you say you have a tilt adjuster, so what do your stars in the corners look like before you have adjusted for the tilt, to see if they look like mine do…

It does sound like a different problem Stewart. Can you post a single stretched sub to compare?

This is a single 120s sub (Blue filter) uncalibrated, uncropped showing my corner star shapes from tilt (incidentally a nice Meteor too).

Hello all,
I am really struggling and am wanting help form any Takahashi FSQ85 owners, now you guys will know that these  scopes don’t play nice with modern small pixel cameras, such as my QHY268m and 268c cameras with 3.76 micron pixels, so Tak bought out a new corrector for this issue and it’s not included with the scope when you buy it new, well mine was made the year before they were supplied with the new corrector, so I have now bought it.

so before when I mages with this scope and camera combo I had bad astigmatism in the outer 1/4 if the image, with cross like star shapes, which apparently was normal for this scope and small pixel camera, now after fitting the corrector, it’s much better, but it’s still there when you zoom in in the image, albeit not as bad, but still there, so why is this..? I have used the correct 56.2 backspace plus 1/3 of my filter thickness, ..??

would the corrector not work properly if the spacing is wrong, and what should I see, if anything the corrector is too close, maybe 0.1mm would this really make a difference….I just expected it to be much improved and it’s not….☹️

so any advice of if you have some un cropped images taken with your set up with this scope and the 1.01x flattener, I would like to compare to mine…

Help appreciated 
Stewart

I have the FSQ-85EDX (with the 1.01 flattener incl.). I run it currently on a QHY600M. Exactly matching back focus is certainly critical. So is tilt. I have a tilt adapter in the image train and after some fiddling it is now quite good in the corners. Your calculation of 56.2mm + 1/3 filter thickness is correct. (i currently do not have an un-cropped image published here but will do so in a few weeks when my current target is completed). CS, John
(P.S.: I do have an un-cropped FF image but that was with a 5.36u EOS R: https://www.astrobin.com/sha3ff/C/ )

thanks for the reply,
so with incorrect back focus what should I typically see, the astigmatism back, but not as bad…???  If so then that could be the issue, but why would my scope require more or less than the stated 56.2mm do all scopes vary a bit…?? Is 56.2 just a guide and starting point…??
sorry for all the questions….

Andy Brown:

This is what it looks like with the flattener, in the top right corner, excuse the quality, was just to show the issue, it’s blown up 3-1 in Pixinsight…see how that look cross shaped and bloated, some of the smaller ones look almost square, which is clearly astigmatism, it was much worse before the flattener…

Not too clear from this Stewart, but could this just be undersampling? Is this with the 268C? What filter are you using, if any, and where is it in the imaging train? Have you tried drizzling to see if that improves it? 

Sorry for all the questions. Andy

Andy Brown:

And this was before the flattener was fitted….😮😮

I agree this isn't tilt Stewart. Could this be a collimation problem? I had to send mine back to Takahashi Europe to have the focuser tightened and they collimated it for me too. I've never seen star shapes like this 🤔

Andy Brown:

Andy Brown:

Hello all,
I am really struggling and am wanting help form any Takahashi FSQ85 owners, now you guys will know that these  scopes don’t play nice with modern small pixel cameras, such as my QHY268m and 268c cameras with 3.76 micron pixels, so Tak bought out a new corrector for this issue and it’s not included with the scope when you buy it new, well mine was made the year before they were supplied with the new corrector, so I have now bought it.

so before when I mages with this scope and camera combo I had bad astigmatism in the outer 1/4 if the image, with cross like star shapes, which apparently was normal for this scope and small pixel camera, now after fitting the corrector, it’s much better, but it’s still there when you zoom in in the image, albeit not as bad, but still there, so why is this..? I have used the correct 56.2 backspace plus 1/3 of my filter thickness, ..??

would the corrector not work properly if the spacing is wrong, and what should I see, if anything the corrector is too close, maybe 0.1mm would this really make a difference….I just expected it to be much improved and it’s not….☹️

so any advice of if you have some un cropped images taken with your set up with this scope and the 1.01x flattener, I would like to compare to mine…

Help appreciated 
Stewart

Hi Stewart,

I've had my Baby-Q for just over a year and corner stars can be a problem, as John has said, the backspacing is fairly critical and also tilt from the rotator (if yours has one) and the focuser. I've invested in a Gerd Neuman Tilt Adjuster which I'm hoping will solve my issues but I've not yet had time to play with it. I'm also using the 0.73x reducer with a 294mm-pro but the flattener should be better, even with an APS-C size sensor.

CS,

Andy

Thanks for the reply,
we’ll tilt is not the issue here, as my camera had a very small amount which was sorted, it was I let about 20 microns out in one corner, the other two corners were pretty much perfect, also tilt would not manifest with these shaped stars, this is astigmatism,  it’s almost like the flattener is not here at all, as it’s not much better than before I put it on, I just wish I knew what it was….

you say you have a tilt adjuster, so what do your stars in the corners look like before you have adjusted for the tilt, to see if they look like mine do…

It does sound like a different problem Stewart. Can you post a single stretched sub to compare?

This is a single 120s sub (Blue filter) uncalibrated, uncropped showing my corner star shapes from tilt (incidentally a nice Meteor too).

that is not tilt, your top left stars elongate towards the middle of the image, the bottom left stars also point towards the middle of the image, that would not happen with tilt. Tilt manifests from one corner or one side to the other, out of focus on one side side, and in focus on the opposite….🤔

is your flattener fitted there….if so then try moving it away a little bit…

Andy Brown:

And this was before the flattener was fitted….😮😮

I agree this isn't tilt Stewart. Could this be a collimation problem? I had to send mine back to Takahashi Europe to have the focuser tightened and they collimated it for me too. I've never seen star shapes like this 🤔

well it’s perfect with older CCD cameras with larger  pixels, the stars are pretty much perfect from edge to edge,,,so no, the scope is fine, it’s to do with the flattener, if it’s not used this is what you get in the corners, hence wanting to see some other images that have been taken using a similar camera and this scope with no flattener fitted…

this was taken with the same scope, no flattener and an old SXVR M25c CCD camera with same size sensor but 8 micron pixels, and the stars are great edge to edge, as this is what these scopes were designed for, hence not needing the flattener, as there is already one built into the scope…