I have the 294 and 80 Esprit, but should be the same setup since they vary the length of extender tube attached to the flattener (according to the manual anyway) to compensate. Everything I needed for reaching back focus came with the Esprit and 294.
According to the manuals on the site (page 8),
80 Esprit: https://cdn.shopify....Esprit80EDT.pdf
100 Esprit: https://cdn.shopify....sprit100EDT.pdf
The 80 says it requires 66mm back focus, and the 100 needs 63mm. (Top of page 8).
Next, it mentions the ring spacer for the 80 as 11mm, and for the 100 as 8mm (Middle of page 8).
For me, the flattener came pre-assembled with the spacer already attached, but it sounds like yours is missing, or maybe you got it now?
Assuming it's attached, we can then subtract how much back focus we have left to fill,
80 needs 66mm - 11mm = 55mm
100 needs 63mm - 8mm = 55mm
So rest of setup should be same if we have the same camera.
With the ASI294, it should come with a 16.5mm spacer, a 21mm spacer, an 11mm spacer already attached to the camera, and an additional 6.5mm of space is between camera edge and sensor. This is according to the ZWO website (graphic at bottom of page): https://astronomy-im...294mc-pro-color. That gives a total of 16.5 + 21 + 11 + 6.5 = 55mm. This then gives a grand total of 11 + 55 = 66mm for the 80 and 8 + 55 = 63mm for the 100.
Here's a picture of the setup on the 80,
- Draw-tube adapter, does not affect as it's in front of field flattener, comes with Esprit.
- Adapter I bought which allows me to put in a 2-inch filter without having to mess up my back focus, since it's on the telescope side of the flattener. You can find it here if you're curious, but this is not required.
- Field Flattener
- The extender tube (M48 adapter) which came with the Esprit, came pre-attached to field flattener; for the 80 gives 11mm, for the 100 it should be 8mm
- 16.5mm extender, comes with ASI294
- 21mm extender, comes with ASI294
- 11mm extender, comes attached to ASI294, plus 6.5mm to the actual sensor for a total of 17.5mm
I hope that helps, but if anyone sees any issues with the above, let me know!
Edited by Brule, 10 November 2019 - 02:04 PM.