[PRejto (Peter)]

Let's say I have a flattener that requires BF of 116mm. I'm trying to decide if my TEC180 will have enough focus in travel to accommodate the flattener. How does a flattener change the focal point compared to a scope without a flattener? Do they push the focus out a bit? A Precise Parts fitting on the focuser drawtube adds about 9mm. 116 + 9 = 125mm. Is it safe to assume that if I have over 5" of in travel on the focuser this will work?

Thanks!

Peter

Edit: The flattener I'm considering is for a TOA-130. I wouldn't expect it to give a full frame corrected field on a TEC180, but might it give enough correction to cover a KAF8300 chip? The TOA-130 is for a 2.7" focuser. Should I also worry about vignetting? Ideally I'd use the TOA-67 4" flattener. But with a BF of 106mm it is just a tad to short to fit my current gear. To use it I'd need to get a different camera, or a new housing for the camera I want to use. (Moravian G2-8300. I'd need the model without the inbuilt filter wheel)