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TS Optics Photoline 80mm F6 APO and TSFLAT2

TS-Optics TSFlat2 Equipment Flattener Refractors
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lensflaredk avatar
lensflaredk avatar
I use a combination of the TS Optics Photoline 80mm F6 APO and TSFLAT2 and I have had (still have) huge issues getting decent stars.

First I followed the instructions and did a 123mm backfocus (also tried adding a bit to account for filters) and it did not improve. Then I took some shots in the dark and managed to improve it but ended on a backfocus of 107,5mm. Better result than before. But I am still not impressed. Anyone been through something similar and have any good advice? I'm using a touptek 2600mm with filters and all that.

Comparing the different backfocuses. Shot on a night with some clouds, so not ideal but still gave a result
https://www.dropbox.com/s/p4qepbwtggm80lh/astro_compare_tsflat2.jpg?dl=0

Stacked frame where it really shows up
https://www.dropbox.com/s/h7l0e2c9sp4sk14/masterLight_BIN-1_6224x4168_EXPOSURE-300.00s_FILTER-Ha_mono.jpg?dl=0

Just a cornergrab as it is now. This is at 107,5mm. 123mm was worse.
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andrea tasselli avatar
andrea tasselli avatar
What does the field look like without the corrector?
Giovanni Fiume avatar
Giovanni Fiume avatar
I have the same apo, but with a TSRed279 reducer, and a 115/800 with a TSRed379 reducer.
Until I was using a Moravian G2-8300 and a asi533 I never had any problems.
Since I bought a QHY268 it has become a nightmare.
The Sony IMX571 sensor is a killer. It wants super corrected optics and correctors and high level mechanics (focusers).
I have stars on the edge of the field distorted due to the tilt, but also due to aberrations that I could not see with less demanding sensors.
I've tried various backfocus distances, but haven't been able to fix until now.
I would also like to take the TSFLAT2 because I believe that a flattener creates fewer problems than a reducer with with this sensor.
In any case your stars aren't so bad … but if you are a pixel peeper like me …
lensflaredk avatar
lensflaredk avatar
lensflaredk avatar
lensflaredk avatar
Giovanni Fiume:
I have the same apo, but with a TSRed279 reducer, and a 115/800 with a TSRed379 reducer.
Until I was using a Moravian G2-8300 and a asi533 I never had any problems.
Since I bought a QHY268 it has become a nightmare.
The Sony IMX571 sensor is a killer. It wants super corrected optics and correctors and high level mechanics (focusers).
I have stars on the edge of the field distorted due to the tilt, but also due to aberrations that I could not see with less demanding sensors.
I've tried various backfocus distances, but haven't been able to fix until now.
I would also like to take the TSFLAT2 because I believe that a flattener creates fewer problems than a reducer with with this sensor.
In any case your stars aren't so bad ... but if you are a pixel peeper like me ...

I have two issues with what is going on.

1. On their webpage it is being sold as to give nice corner-stars, which I'm not seening, far from it.
2. This is the big one that makes it smell. 123mm is supposed to be the ideal BF for it. I found it best at 107 (and having bad stars), which makes me think something else is going on.
Giovanni Fiume avatar
Giovanni Fiume avatar
Giovanni Fiume:
I have the same apo, but with a TSRed279 reducer, and a 115/800 with a TSRed379 reducer.
Until I was using a Moravian G2-8300 and a asi533 I never had any problems.
Since I bought a QHY268 it has become a nightmare.
The Sony IMX571 sensor is a killer. It wants super corrected optics and correctors and high level mechanics (focusers).
I have stars on the edge of the field distorted due to the tilt, but also due to aberrations that I could not see with less demanding sensors.
I've tried various backfocus distances, but haven't been able to fix until now.
I would also like to take the TSFLAT2 because I believe that a flattener creates fewer problems than a reducer with with this sensor.
In any case your stars aren't so bad ... but if you are a pixel peeper like me ...

I have two issues with what is going on.

1. On their webpage it is being sold as to give nice corner-stars, which I'm not seening, far from it.
2. This is the big one that makes it smell. 123mm is supposed to be the ideal BF for it. I found it best at 107 (and having bad stars), which makes me think something else is going on.

The TSFLAT2 is a universal corrector, not dedicated.
The published backfocus distances are recommended and not exact.
However if you have bad stars on all four corners, it could still be a backfocus problem or simply an optical system that is not correct enough for your sensor.
If instead the distortion is not symmetrical, then you too have a tilt like me.
It could be the focuser, any extensions or adapters you use, or the camera itself.
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lensflaredk avatar
lensflaredk avatar
So universal correctors are crap?
andrea tasselli avatar
andrea tasselli avatar
andrea tasselli:
What does the field look like without the corrector?

https://www.dropbox.com/s/o5pwlhhck1xz2rw/no%20reducer%20m71_2022-12-15_17-16-57_100_-9.70_30.00s_0001_Lum.jpg?dl=0
There you go

Looking at the uncorrected image I can see textbook astigmatism due to the astigmatic field curvature and nothing new here. I think the issue is with the corrector-flattener which introduces far more coma than it should. I suspect, given the price, it is one of the cheaper variety which I once tested and not really good at f/6 and below. If you can, send back and get your money back. My Hotech works reasonably well but if I had to do it again I'd go with another one.
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SBodin avatar
SBodin avatar
Hello lensflaredk,

I just received a new TS Photoline 80mm F/6 APO with the  TSFLAT2 flattener this week. The weather has been bad but I was able to set up for a few quick shots the other night. I used the recommended 123mm spacing as well as was quite disappointed in my stars around the corners. I hope to experiment again very soon. I appreciate your posting your results. If I learn anything I'll be certain to share with you. I'm shooting with a modified Nikon D550. No sensor tilt 'in camera'…stars are  fine in my homemade 6: Newtonian. Purchased the TSFLAT2 because its long backfocus allowed insertion of a filter drawer and off-axis guider should I wish to add them in the future.

SBodine
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lensflaredk avatar
lensflaredk avatar
Hello lensflaredk,

I just received a new TS Photoline 80mm F/6 APO with the  TSFLAT2 flattener this week. The weather has been bad but I was able to set up for a few quick shots the other night. I used the recommended 123mm spacing as well as was quite disappointed in my stars around the corners. I hope to experiment again very soon. I appreciate your posting your results. If I learn anything I'll be certain to share with you. I'm shooting with a modified Nikon D550. No sensor tilt 'in camera'...stars are  fine in my homemade 6: Newtonian. Purchased the TSFLAT2 because its long backfocus allowed insertion of a filter drawer and off-axis guider should I wish to add them in the future.

SBodine

Looking forward to hear your results. I ended up buying adapters so I could screw it all together and reduce a lot of tilt that way. For me there were some sag in the compression ring.
But it didn't fix the problem in the corners.
Janez Skubic avatar
Janez Skubic avatar
There is difference in distance sensor to flattener for APO80 scope with 480mm and 560mm focal lengths. Distance to flattener for 560mm is around 118mm. Check which of the scopes you have. I had this same problem.

Janez
lensflaredk avatar
lensflaredk avatar
Janez Skubic:
There is difference in distance sensor to flattener for APO80 scope with 480mm and 560mm focal lengths. Distance to flattener for 560mm is around 118mm. Check which of the scopes you have. I had this same problem.

Janez

Mine is the 80mm F6 (480mm FL). So it should be 123mm, but isn't. I also tried around 115 and it was not better than 107
Michel Makhlouta avatar
Michel Makhlouta avatar
I owned this combination before and I remember the backfocus was around 123 (plus or minus 5mm, margin of memory error). I bought delrin rings from 0.3mm to 1.5mm and experimented a lot to get it right. I remember I had a hard time getting decent stars but mine were either elongated or radial, never seen the shapes you are seeing. That doesn't look like a spacing issue? Did you get in touch with TS? Maybe the lenses are over tightened for shipping? I heard some manufacturers do that.
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lensflaredk avatar
lensflaredk avatar
Michel Makhlouta:
I owned this combination before and I remember the backfocus was around 123 (plus or minus 5mm, margin of memory error). I bought delrin rings from 0.3mm to 1.5mm and experimented a lot to get it right. I remember I had a hard time getting decent stars but mine were either elongated or radial, never seen the shapes you are seeing. That doesn't look like a spacing issue? Did you get in touch with TS? Maybe the lenses are over tightened for shipping? I heard some manufacturers do that.

I wouldn't rule anything out. I have used small spacers around 123 with no difference, I only saw an improvement when drastically reducing the distance. But still not amazing. Might be both the scope and flattener. At least i'm pretty convinced there is something wrong in the state of jutland...
SBodin avatar
SBodin avatar
Isn't it a bit backward that when you shortened the backfocus to 107.5mm you improved the radially elongated stars. Generally one would 'increase' the backfocus to address that, correct? Perhaps I am missing something.
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lensflaredk avatar
lensflaredk avatar
I agree. First I tried was to make it longer but it only made it much worse.
Janez Skubic avatar
Janez Skubic avatar
My experience is that TSFLAT2 should work as specified by the vendor. Possibly a faulty or wrong product.

I have the same type of equipment, TSAPO80 480mm with TSFLAT2 ASI2600MC. Flattener is at around 123mm, I do not see any problems with stars, stars are round and tight even in the corners.

Janez
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lensflaredk avatar
lensflaredk avatar
Janez Skubic:
My experience is that TSFLAT2 should work as specified by the vendor. Possibly a faulty or wrong product.

I have the same type of equipment, TSAPO80 480mm with TSFLAT2 ASI2600MC. Flattener is at around 123mm, I do not see any problems with stars, stars are round and tight even in the corners.

Janez

When did you buy yours?
SBodin avatar
SBodin avatar
Janez' experience does seem to possibly indicate a flaw in the scope. In my very limited (one night for half an hour) experience the corner stars look more like the result of coma than the expected field curvature. I understand this is not supposed to be a significant problem in APO refractors, and I'm not qualified to judge. But attached is the upper right corner of my one stacked image of M42 (just 15 minutes, no darks, flats or bias) with back focus set at 123mm.

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lensflaredk avatar
lensflaredk avatar
Your result is not far off mine at 123mm
Marius Bednar avatar
Marius Bednar avatar
Have a look at my gallery.

The elephant's trunk and Gamma Cygni were taken with the TS 80/480 FPL53 Triplet Apo with the 2" TS flattener spaced 118 mm in front of the sensor.

Elephant's Trunk

Gamma Cygni, Butterfly Nebula

I notice stars being slightly sickle shaped in the corners, indicating spacing to be too much.

With my current OAG the spacing is 116 mm. The following is the result

Cave Nebula

Stars are pretty bloated/fluffy in all these photos, due to haze and aggressive stretching during processing to reveal the nebulae, but I think 116 mm yields slightly better results than 118 mm.
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lensflaredk avatar
lensflaredk avatar
Latest update, did some further testing and they asked me to return the scope and flattener so the technical personal could take a look at it
Flemming Kristensen avatar
Flemming Kristensen avatar
I've had exactly the same experience with this scope/flattener combination. After several trips back to the shop for testing and tweaking, including an exchange to a better flattener (the TSFlat25Del) TS finally had to admit they couldn't fix the problem and took the scope and flattener back. They offered to replace it with a better refractor with a dedicated reducer. After a bit of negotiating I ended up with an upgrade to a 94EDPH seven lens system at a discount with which I am fairly happy.

(If you take a look at my Pleiades image from December '21 you will find corner stars which look exactly like yours.)
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