TS 2" Field Flattener (TSFLAT2) Review

[cgarry]

This is a quick review of the Teleskop Service 2" Field Flattener - Universal Field Flattening Lens as used with my William Optics Zenithstar 80FD scope (f/6.9) and QHY8L camera (APS size sensor).

The TSFLAT2 is a field flattener designed to work on a broad range of refractor telescopes, from f/5 to f/8. The flattener does not act as a focal reducer so the focal ratio of the telescope remains unchanged.

Here is a picture of the TSFLAT2, the battery is just there for scale:

Here is a picture of the TSFLAT2 connected in the optical train as I use it:

The recommended distance between the flattener and the camera sensor is 109mm, however with my set up I found that it works better with about 120mm of spacing. Trial and error is the key here.

The next image is a simple stack of just two 300s subs taken without the flattener in place. The image has not been cropped but has been reduced in size and had a simple histogram stretch applied.

This image shows the four corners of the image at full size, this shows the coma problems well:

The following images are the equivalent pictures taken with the field flattener in place. These were taken with a very bright moon spoiling any chances of doing any proper imaging, but are good enough to show the star shapes.

As can be seen, the flattener has made a huge difference to the image, keeping the stars round, tight and focused right to the corners of the QHY8L's large chip. I am very pleased with how it has performed and looking forward to working on some real images when the moon finally goes away.

A further bonus that I was not expecting is the effect the flattener has had with the off axis guider. Because the stars at the edge of light cone where the OAG takes its light from are now tight and focused rather than smeared, many more starts become available to guide with in PHD. I was really pleased to see this side effect of the flattener.

Cheers,

Chris

[TeleSkoop]

Thank you for the review. I never got mine working properly with a Canon 50D. It is better, but I did expect more.

Trial and error is the key here.

I probably need to do more experimenting.

I have the TS 90 MM APO and unmoded Canon 50D.

If you have a same setup and get a nice flat image, please let me know how.