Without chasing down the problem, I can confirm that the new polar alignment scheme does not work with my RASA/CGX-L config. The symptom is as previously described; the motion in each mount axis does not correlate to the drawn vectors. Worse, the results are not sufficiently repeatable to warrant trust without verification. After confirming many times that the results were different each time invoked, (verified with drift aligns after each attempt over several nights), I gave up on the feature and returned to other align methods. Just a heads-up to folks to not blindly trust this feature without doing verification by drift align if it matters to you..... CS Doug

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Doug S replied to the topic 'Change USB traffic for ZWO ASI camera' in the forum. 2 weeks ago

It would be helpful to have just a bit more context about what problem you're experiencing. Is this your imaging cam or guide cam? Are you using ST4 or not? How much gear do you have using USB? Are you using a USB hub, RPi4, or ??? If Rpi4, are you using USB2 or USB3? What's the symptom you're experiencing, and is there any more to the story about why ZWO recommended you adjust USB traffic settings? I don't have a clue what that 40 parameter is all about, but if you give more context, you might get to the root cause & solution. Cheers, Doug

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Hi Jo, I accept it's ok to allow the step size to be user set, but I don't think it's optimal. There are many users who will not get this set right (and there is a "right" setting to within a tolerance). It's true that you can experiment with a V curve to iterate/guess at step sizes, but I prefer a measurement that relates to CFZ and the motor/drawtube relation. That prevents jumping over the CFZ and not achieving best focus (i.e. step size too big), and wasting a lot of time (iterating through measurements where the step size is too small).

Hi Andrew, yes, multiple measurements makes for better averages, and I do this as well. It takes longer, and this is part of the reason I like having a solution to OP #3.

Cheers, Doug

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regarding OP points 2 & 3:

Point 2: While I concur that the method of measuring HFR can be a step in a better direction, HFR readings can be very suspect to momentary bad seeing variability. A slightly more rigorous approach would be better. IMO, it was a mistake to allow users to set a step size directly in the GUI. This info should have been automatically calculated from known parameters of the optical system and a user estimate of best seeing and acceptable focus tolerance. See this reference for details:
www.goldastro.com/goldfocus/ncfz.php
Folks who take the time to read the above will know the size of their gear's CFZ. A 1/3 CFZ stepsize would give ensure the right focus is always obtained (for well functioning focusers). The most difficult aspect of the above is that the Ekos step size must be known in motor counts, not microns. To find the correct step size in motor counts, a user must drive the focus motor through some measured focuser travel (or know the thread pitch of the internal focuser's drawtube and motor counts per rev). Many refractors have a scale right on the focuser to make this easier, so the #counts per mm (for instance) can easily be found. In the end, the # of motor counts per micron yields a correct mathematical answer for step size. IMO, the GUI should have been better thought out and is at the root of much of the confusion.

On point 3: I've been using a developed temperature based focus compensation (also with altitude residuals) in my own Ekos branch for many months now (search temperature compensation for postings). I have reduced my autofocus runs to a minimum. I don't waste precious observing time on focusing any more. I offered the code to anyone who wanted it and suggested it could help the community. I made clear from the start that I wasn't a GUI developer, and I developed the feature with a config file. Some suggested a GUI was desirable (I didn't disagree, but it isn't necessary strictly speaking). Unfortunately, no volunteer was found to develop the GUI to replace the config file (used for controls and function(s) definition). So, the community wide effort was abandoned for lack of interest. Some folks actually prefer the simplicity of repetitive focusing. For my f/2.2 rig, this was too much of a waste of time to bear. To each their own! Cheers, Doug

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Duncan, you don't need to do a 2 star align. Most folks do a "quick align" with the HC before moving to Ekos control (which pretty much does nothing....in place alignment for time in HC). Afterwards, do a drift align or other polar align method (your choice) in Ekos. This will save time. If you continue to struggle with Ekos guiding, you might try PHD2 guiding to see if you can break through there. If so, then look closer at your guiding setup parameters to see if you've got something askew. Good luck....

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The USB3 powered hub I used is here:
www.amazon.com/gp/product/B00SIQIV04
I do power the hub from the PPB; works great. I did do some soldering to shorten some of my cables for a nice clean fit (when I couldn't find short cables to purchase).
About the RASA, it's a really decent wide field scope, but I designed it for narrow field by clipping the wavelength (Hoya UV/IR filter), and then pairing with a small pixel field and smaller chip (intentional to keep off-axis distance small). I probably should have gone with an ASI294 (didn't know about "unlocked mode"), but I did go with an ASI183mcPro & 2.4um pixels. That makes for reasonably nice images and platescale of 0.799 arcsecs/pix. See here for example images I've captured with the RASA:
www.astrobin.com/users/dmsummers/
Good luck with your cable management & new EAF focuser; I'm really happy with my EAF. BTW, expect about 90 steps of backlash for the EAF.
Cheers, Doug

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