My current setup for OSC on the Takahashi FSQ-85 uses the QHY-OAG-M and the various QHY metal spacers which you screw through the OAG onto the CAA that fronts the QHY286C.
However, I’ve never liked the screw adapter approach for this sensor as unnecessary back focus is wasted due to the weird CAA to QHY286C not being a screw thread. The lack of an IR cut window on the QHY268C sensor means I need to sit an additional filter in the QHY 020055 M48 (F) adapter, in order to change the filter I would have to take the imaging train apart to remove it !!!
Baader Universal Filter Changer
Enter the Baader Universal Filter Changer (UFC) , the chart below details the core base changer alongside the adapters required to match to most common setups.
You can purchase additional sliders than can hold 50mm, unmounted and threaded 2 inch (M48) filter. The slider is magnetic so it will not dislodge during slews or during scope assembly or disassembly.
Proposed Set-up
The Takahashi Flattener (TKA37582) has a metal back focus distance of ~56.2 mm so I need to get close to that but being under that distance is better than being over as I can add additional spacers if needed. The effect of adding a 2mm thick 2-inch filter decreases the optical backfocus by 0.6mm (2mm/3) so I will need to add 0.6mm spacing to account for the filter effect which results in a total distance of ~56.7mm.
| Order | Component | Thickness (mm) |
|---|---|---|
| 1 | QHYCCD QHY268C CMOS | 17.5 |
| 2 | QHYCCD CAA M54(f) (#020002) | 6 |
| 3 | Baader UFC M54(m) camera side adapter (#2459117) | 2 |
| 4 | Baader UFC base (#2459110) | 13 |
| 5 | Baader UFC SP54(m) telescope side adapter (#2459134) | 1 |
| 6 | QHYCCD OAG-M M54(f) (#020079) adapter | 3 |
| 7 | M54 Metal Spacer | 0.5 |
| 8 | QHYCCD OAG-M | 10 |
| 9 | QHYCCD Metal Spacer | 0.4 |
| 10 | QHYCCD OAG-M M54(f) adapter | 3 |
| 11 | M54 Metal Spacer | 0.3 |
| 12 | Baader M54 x 0,75 Inverter Ring | 0 |
| Total | 56.7mm |
I should now be able to change filters much easily albeit at an additional cost but the flexibility should be worth it. Of course I will need to test the star shapes in the field to make sure that I have the correct back focus and add extra distance if needed.
Vendors
The majority of the Baader UFC components were purchased from FLO (First Light Optics) and the remaining adapter (#2459134) from Tring Astronomy. Delivery and communication by both vendors was great, shame about the Royal Mail industrial action messing deliveries about during the Christmas holiday.
Thanks
My gratitude to Stuart1971 from StargazersLounge who helped me with suggestions to try to sort out the QHY268C noise banding issues.