Hello, I am considering purchasing an STX-16803 for use with both a PlaneWave CDK12 (F/8) and a TEC APO140ED (F/7.) I am also interested in adding in an Optec (Gemini or Pyxis 3”) Rotator. It seems that the limited back focus on each telescope (11.09” for the CDK12 and 7.2” for the TEC140) may be insufficient for a rotator combined with the STX-16803, FW7-STX filter wheel, STX Guider and the AO-X adaptive optics accessory. Dropping the AO-X (and adding a custom Precise Parts adapter) seems to help. Also, based on what I read in the AO-X manual, perhaps my focal lengths of 2541 and 980 mm respectively might not be a good fit. Any feedback will be appreciated. Following Is my shot at an image train for the CDK12 + STX-16803. (Question: can I just attach the Pyxis rotator directly to the STX Guider with a custom part?) And I’m not sure about the TEC140. View attachment 4139
The rotator uses a lot of back focus. Given that the STX has a square chip do you really need it? Or did you want it to help locate guide stars?
Thanks Doug, and no the rotator is not a requirement. I’m just transitioning from an Alt/Az mount + DSLR to a GEM + CCD (plus a built-in tracking CCD too.) I just need to abandon old ways of thinking. Regarding the built-in tracking CCD, I've been a bit confused about using the built-in guider vs. using the STX Guider on the front of the FW7, and 50 versus 65 mm filters. I think I was looking at older information. Let me know if I understand this correctly, but I believe I can use the STX Guider and FW7 with 50 mm filters, ignoring the built-in guide chip in the camera, and negating the need for an OAG and/or a separate guide scope (I’m also using an MX+ with Tpoint, ProTrack and PEC.) Plus I now have an FW7 filter wheel (with LRGB filters, plus Ha, SII, and OIII narrowband filters,) and I’m guiding in front of the filters (a plus for narrowband and guide star selection.) Finally, regarding the AO-X, assuming I have OK seeing (2-4” FWHM,) and the following assumptions, would the AO-X be of use to me?
We're moving away from the built-in guiders. Having the guider behind the filter is a problem for narrowband imaging. The larger filters are expensive and you get fewer in the wheel. Since the introduction of the STX Guider - as we expected - everyone is buying the FW7-STX instead of the FW5-STX. No one is using the internal guider anymore. And that's a good thing. Yes the AO-X will be useful. In fact on your best nights it should improve your FWHM noticeably.
Thanks again. Also, is there anyone I ask about the required adapters and spacers for connecting an STX-16803 to a 2018 TEC140? I believe the focuser on the TEC140 is a 3.5” Starlight focuser. I took a crack at crafting an image train (please see image below) using the TEC140 field flattener, and another using an AP 0.72x Quad Telecompressor. In both instances I am unable to fit the STX Guider and AO-X unit into the image train. Assuming I image with just the camera and filter wheel, it seems as if I may need one custom adapter to connect the TEC FF to the SBIG FW7-STX, and a second custom adapter to connect the AP Reducer to the SBIG FW7-STX. And since there is seemingly no room for the STX-Guider (and AO-X,) I’ll plan on either taking unguided exposures with my MX+ (and creating a nice Tpoint model,) or (in this case) I can use the STX-16803’s built-in guide chip and guide from behind the filter wheel (just have to avoid narrowband for now.) Alternatively, should I be looking at a different field flattener and/or reducer+flattener that leaves me with more available back focus? Sorry for asking but I haven’t had time to research other options yet. Oh, and I'm going to look at image trains for a PlaneWave CDK12.5 next. I assume that will be a bit easier.
Hi Nick, I can help you with the final details with the adapters and logistics of use. Send me a private msg with your telephone number and will be glad to assist you with 1 on 1 support. Best regards Tim
