Takahashi FSQ106ED - am I expecting too much?

[Steve 1962]

Hi

I've not posted much recently because I've upgraded my kit with a new (to me) 10 Micron GM1000HPS mount and a Takahashi FSQ106ED. (Thank you Mrs L - you are lovely!  ).

I went from an FLT98 to the FSQ because my long term aim is replace my Atik 460 with a larger chipped CCD..and the FSQ has a very large image circle. To quote the Tak Europe website; " CCD users will be able to dream with the use of large sensors without risk of vignetting or loss of definition in edge of field. ........... A perfect image is at this price. . The scope's strapline title is a "Flatfield Super Quadruplet".

I've finally got the scope on the mount, with a fully screwed together 72mm diameter image train leading to an SX OAG, FW then the 460 camera. This reached focus with drawtube extended about 10mm. The image scale is 1.765" / px ..... and here's what I've getting.....

The full size image of the corners can be found here; https://www.flickr.com/photos/perrybarn/15499383782/ 

This was 60secs binned 1 x 1 through an L filter and is typical of the results I'm getting. For this image, the focuser was orientated to be horizontal side to side.

After several days of fettling and sorting out problems (most of which were down to me I admit but including last night when I spent 7 hours trying to adjust out a visible side to side (i.e. parallel with the focus knob shaft) sag out of the focuser) this is the best I can achieve.

I think that the stars in the top left and bottom right are slightly eggy.

This wasn't what I was expecting, but I'm worried that my expectations are too high (even for a £4k scope!?) , so before I go any further with this I'd welcome anyones' views about this image and whether I need to get on with my life, stop nit picking and just start enjoying my dream set of kit.

Thanks in advance.

Steve 

.

[Liquid360]

I can't yet comment, but I just bought the same scope... I'll be following this thread. Which mount?

[Steve 1962]

 I just bought the same scope... I'll be following this thread. Which mount? 

I went for the 10 Micron GM1000HPS - which I'm extremely pleased with. I'm pleased to see you got your PMX sorted..and I'll be very interesting seeing what you get from your Tak.

Steve

[Liquid360]

Thank!! Ditto!!! Shall we be the blind leading blind? [emoji6]

[Liquid360]

PS. I'm gonna be afraid to post images first.... I'm afraid I'll never live up to my hardware.

[Steve 1962]

I should add that, even if this is deemed acceptable - should I worry about future use of a heavier camera with a larger chip albeit probably with pixels 1.5x  or 2x the size?

[Liquid360]

My QSI causes no problems... yet. Out of the List Of Concerns it's nothing to worry about. I've not heard otherwise. Helpful huh?

[JRWASTRO]

Hi

I've not posted much recently because I've upgraded my kit with a new (to me) 10 Micron GM1000HPS mount and a Takahashi FSQ106ED. (Thank you Mrs L - you are lovely!  ).

I went from an FLT98 to the FSQ because my long term aim is replace my Atik 460 with a larger chipped CCD..and the FSQ has a very large image circle. To quote the Tak Europe website; " CCD users will be able to dream with the use of large sensors without risk of vignetting or loss of definition in edge of field. ........... A perfect image is at this price. . The scope's strapline title is a "Flatfield Super Quadruplet".

I've finally got the scope on the mount, with a fully screwed together 72mm diameter image train leading to an SX OAG, FW then the 460 camera. This reached focus with drawtube extended about 10mm. The image scale is 1.765" / px ..... and here's what I've getting.....

Capture.JPGCorners.jpg

The full size image of the corners can be found here; https://www.flickr.com/photos/perrybarn/15499383782/

This was 60secs binned 1 x 1 through an L filter and is typical of the results I'm getting. For this image, the focuser was orientated to be horizontal side to side.

After several days of fettling and sorting out problems (most of which were down to me I admit but including last night when I spent 7 hours trying to adjust out a visible side to side (i.e. parallel with the focus knob shaft) sag out of the focuser) this is the best I can achieve.

I think that the stars in the top left and bottom right are slightly eggy.

This wasn't what I was expecting, but I'm worried that my expectations are too high (even for a £4k scope!?) , so before I go any further with this I'd welcome anyones' views about this image and whether I need to get on with my life, stop nit picking and just start enjoying my dream set of kit.

Thanks in advance.

Steve 

.

Greetings Steve,

I agree about the shape of the stars and I do not think your expectations are too high. This is top quality optics and so it should produce a top quality picture.

The Atik 460 has a relatively small sensor (16mm diagonal) so much so I would expect to see virtually no distortions in that image given that the FSQ106 image circle diameter is specified at 88mm and further the FoV is only 1.7 degrees on the diagonal. 

What also disturbs me is the form of the central bright star ... it displays a diffraction pattern with a "short cross". Why? I could only hazard a wild guess.  Check the shape of the aperture. Is there something "out of round" ?

If you can lay your hand on a camera with a full frame sensor take a picture of a star field and look/measure the distortions . If out of spec send it back for collimation or replacement.

Cheers and beers,

Jeremy.

[steppenwolf]

I too noticed the diffraction spikes (tiny) and wondered if these were a microlens artefact? I have not heard of this issue before with the 460 though.

The black dots are more puzzling though and I can't decide whether they are a processing artefact or a camera fault but I am struggling to think of an optical cause for these.

Sent from my iPhone from somewhere dark .....

[Steve 1962]

Hi Jeremy

Thanks for that - I'm relieved that it's not just me! You've put into words exactly how I feel about this.

 I should have said that the image has had a levels stretch in PS and the small diffraction spikes on the bright star seem to be a feature of my camera - they were there with my previous scope and are always aligned with the x and y axes of the chip - I think I've read somewhere that it's down to microlensing on the chip.

Is anyone out there prepared to lend me a big CCD I wonder? I suppose that really all I need is a T mount for my Canon.

All the best and thanks again

Steve

[Steve 1962]

Hi Steve

Thanks - your comments crossed with mine "in the post".

As as I've said - I've always had them with the 460 and just thought that they were an inherent feature. It only affects the really bright stars (this is Deneb incidentally).

Have I missed some black spots? The original sub was very smooth with low noise (thanks Sony!), so I'm pretty sure that anything you can see is down to some form of compression on here or Flickr.

Cheers

Steve

[steppenwolf]

Have I missed some black spots?

My bad - compression issues, please ignore!

[ollypenrice]

I use two FSQs (though ours are Fluorite super quadruplets. Tak's name change with the glass change always makes me smile! I use them with full frame (35mm) CCDs and get stars which I find fine. 

I don't think the images posted are being quite fair to the optics because I can see certain effects around the stars which cannot be of optical origin. The stars look as if they've been through deconvolution (though they may not have been.) They have dark rings around them. There are other oddities, too, like the little wiggly dark trails close to them. The shapes don't look too good on the small ones, I agree, but given the high level of artefact around them I really suspect that the problem lies in the camera/processing/software side of things.

What is the full history of the FITS from the moment it left Artemis Capture? (If you don't capture in Artemis I'd try dong so, following Ian King's good advice that if something isn't working, run it in its own software.)

Could you Dropbox the untouched linear FIT straight from camera?

Olly

[Steve 1962]

Hi Olly

Thanks for your input.

The images were acquired using Sequence Generator Pro, which has always given me good results with this camera. Thanks for the tip about Artemis - I've never used it, but I will have a go next time it's clear here.

After acquisition, all I did to the imge that I posted was a levels stretch in PS CS5, some cutting and pasting, conversion to TIF for Flickr and JPG for SGL..and posted them.

Here's some links to the last three non-clouded out images from Thursday night. These are unadulterated FITS straight from the camera.

https://www.dropbox.com/s/dyez9ofhwzk7qck/Light%202014-10-10%20030811%20Cave%203_60sec_-15.0C%201x1_L_frame4.fit?dl=0

https://www.dropbox.com/s/qldtyjq28pedqc4/Light%202014-10-10%20030925%20Cave%203_60sec_-15.0C%201x1_L_frame5.fit?dl=0

https://www.dropbox.com/s/nadmhn58e7pyybc/Light%202014-10-10%20031039%20Cave%203_60sec_-15.0C%201x1_L_frame6.fit?dl=0

Thanks again

Steve

[libraryman]

Hi Olly

Thanks for your input.

The images were acquired using Sequence Generator Pro, which has always given me good results with this camera. Thanks for the tip about Artemis - I've never used it, but I will have a go next time it's clear here.

After acquisition, all I did to the imge that I posted was a levels stretch in PS CS5, some cutting and pasting, conversion to TIF for Flickr and JPG for SGL..and posted them.

Here's some links to the last three non-clouded out images from Thursday night. These are unadulterated FITS straight from the camera.

https://www.dropbox.com/s/dyez9ofhwzk7qck/Light%202014-10-10%20030811%20Cave%203_60sec_-15.0C%201x1_L_frame4.fit?dl=0

https://www.dropbox.com/s/qldtyjq28pedqc4/Light%202014-10-10%20030925%20Cave%203_60sec_-15.0C%201x1_L_frame5.fit?dl=0

https://www.dropbox.com/s/nadmhn58e7pyybc/Light%202014-10-10%20031039%20Cave%203_60sec_-15.0C%201x1_L_frame6.fit?dl=0

Thanks again

Steve

I have the 106ed, I see the same cross hairs but at the moment, only through the red filter on my qsi583, I would guess it unlikely that several people have an issue with optics since mine is new as well....I also see a little eggynes but I am putting it down to orthogonality in my train because I'm not using Tak adapters! CCD inspector shows some tilt in my set up.

Interesting thread, I'll be watching ass well

Raay

[perfrej]

Careful when adjusting focuser sag!

/p

[Steve 1962]

Thanks Per!

Ray - sounds like we have similar situations.

Just for the record, the adapters that I'm using are 1 x 52mm long TKA23250 and 2 x 17mm long TKA31581 M72 spacers. These are screwed directly into the M72 adapter on the focuser drawtube. I then have a 72mm adapter for my SX OAG/FW. 

I didn't go for the "standard" CA35 adapter route because I don't like thousands of poinds worth of CCD hanging on a grub screw.

Steve

[pete_l]

Not an FSQ owner, but might I suggest taking one shot, rotating the camera 90° and taking another. See if the issues stay in the same location in the image or if they have been rotated with the camera (or have disappeared altogether).

That will help narrow down if the effects arise in the OTA or in the camera, or change when the camera is moved.

[Earl]

I get the little spikes with my 8300 chip on brighter stars, this is a known microlens issue i have been informed, are you using the reducer?

[Owmuchonomy]

Your expectations are certainly not too high. I paid a lot less for my AA 102 APO EDT and dedicated flattener and I am not satisfied yet with the corner eggy stars I get. The imaging kit is marketed as producing a flat field on a crop sensor. Having generated data and ruled out the obvious with help from SGL Input I have passed the issue back to the distributor.

[ollypenrice]

I've just downloaded Steve's first image, converted it to TIFF in Astro Art 5.0 and given it a standard log stretch (grey point slider) in Photoshop,  then cut back the black point. I think it looks perfect. I've taken the liberty of putting it on my Smugmug gallery so I can link to the fullsize but if that's not OK by Steve I'll delete it.

I simply can't see anything wrong with it. The small diff spikes could be all sort of things but to my eye the stars look lovely, Takahashi all the way.

I won't put a small version on here because the compression artefacts make a muck of it but have a look here at the full; 

http://ollypenrice.smugmug.com/Other/Takahashi-EM200TEC140/i-hBhKQsN/0/X3/Steve%201962-X3.jpg

Personally I'd be delighted by that. (I must say that I heaved a sigh of relief when I checked out the corners at 400%!) 

Olly

[Owmuchonomy]

I've just downloaded Steve's first image, converted it to TIFF in Astro Art 5.0 and given it a standard log stretch (grey point slider) in Photoshop,  then cut back the black point. I think it looks perfect. I've taken the liberty of putting it on my Smugmug gallery so I can link to the fullsize but if that's not OK by Steve I'll delete it.

I simply can't see anything wrong with it. The small diff spikes could be all sort of things but to my eye the stars look lovely, Takahashi all the way.

I won't put a small version on here because the compression artefacts make a muck of it but have a look here at the full; 

http://ollypenrice.smugmug.com/Other/Takahashi-EM200TEC140/i-hBhKQsN/0/X3/Steve%201962-X3.jpg

Personally I'd be delighted by that. (I must say that I heaved a sigh of relief when I checked out the corners at 400%!) 

Olly

I really hope I'm wrong for the OP but I can see eggs at top right on that image link. I have so much empathy as I am still getting my own eggs for breakfast!

[steppenwolf]

Achieving a truly flat field right into the corners seems to be something that telescope manufacturers are currently really struggling with  - even the top brands are not achieving this feature reliably. The closest I've seen so far is the output from the Vixen VSD 100 (f3.8) which uses a 3 element corrector at the rear of the telescope.

However, your expectations are not too high because some imagers (Olly for example) are getting the star shape results they expected from this grade of optic. Spacing and orthogonality are such a pain to get right - I feel your pain!

[Earl]

zooming in to a pixel level might show a touch of eggyness, to resolve it do the rotated camera sub and see if they move with it, if they do the chip is the cause id say. its very minor, I know my field is not as flat as it could be and i need to look into it at some point.

[ollypenrice]

I really hope I'm wrong for the OP but I can see eggs at top right on that image link. I have so much empathy as I am still getting my own eggs for breakfast!

Well, I had another look at the top right and, yes, there is a slight offset. This is an 800% crop.

But, yikes, 800% is a big zoom! Aren't we pixel-peeping at this level?

Olly