5 replies to this topic

[GaryShaw]

Hi Folks;

 

Conditions were not really favorable tonight but its the first clearish night in several weeks since I mounted up the CDK so I decided to do some testing and experimenting to get the feel of the scope.

 

I'm using The Sky X and an MX+ mount and thought setting up for plate solving (image link in TSX terms) might be a good first task to go for. Of course, for that, you need decent focusing so that's where I started - with  TSX's @focus3 autofocus tool. To use @focus3, I needed  to first enter some data on: F-ratio, pixel size and focuser step size.  I had previously asked the folks at Planewave about step size for the Hedrick Focuser that came with the scope, and was told to use 1.0 Micron. This approach didn't get me very far tonight so I increased it to 4.0, then 6.0 microns and finally completed the autofocus routine and the scope was in decent focus. Problem is, I'd gotten to a better focus just doing it manually so I think I'd benefit from some guidance from others on how focuser step size is determined for this combination of gear.

 

If any of you with CDK's could share your experience in setting up efficient step sizes, I'd much appreciate it. Its possible that the conditions tonight were the main problem, but still, it would be interesting to learn if there is a specific step size or a specific approach to determining it that some of you had found. Looks like it will be another week before a clear night rolls along to work on this again.

 

Thanks for giving this some thought...

 

Gary

ps: Next I’ll be working out autofocus in NINA so any insights on the Hedrick focuser step size in that context, would also be very welcome…

Edited by GaryShaw, 07 May 2024 - 10:53 PM.

[Wiecha]

Hi Gary -- so we must have taken delivery of our 12.5 CDK's at about the same time...I had first light also a couple of days ago and am tonight hoping for some gaps in the clouds to do the same experiments as you with autofocusing, starting as well with TSX @Focus3 as well as the provided PWI4 tool.

 

During daylight I just ran the Hedrick focuser from 0 out to maximum range and see the tick counter at 39312...so to first approx let's say 1.3 tick/micron or 0.76 micron/tick.  I was/am a bit surprised by this fairly low resolution as my prior focuser, the Optec Leo, scores 0.08 micron/tick about an order or mag better.  Granted .8/tick is probably ok but just saying...

 

Anyway, you were asking more about the step size for autofocuser increments...we could use this info on underlying resolution to guess how many ticks would make sense for each focuser step.  Of course that will also depend on focal length, camera, thus image scale etc.  I do notice that the PWI4 app defaults to 500 so I will likely leave it there at first both in that tool and in TSX to see how things go.

 

Please let me know when you settle on a good config and I will update as well.

Thx, Charlie Wiecha

[GaryShaw]

Thank you Charlie. Nice to have a fellow traveler to connect with on first use of this OTA. I wish there were some experienced CDK folks responding on this question but we’ll sort things out one way or another. No clear skies anticipated here for at least another week. Hope you have better conditions.
Rgds
Gary

[Wiecha]

Hi Gary -- update from last evening.  So the PWI4 out-of-the-box autofocus worked first time like a charm.  Accepted the default settings, step size of 500 and 5 images overall.  Started with nearby but not good focus.  The app computed the curve and set the focus very nicely.  I haven't tried the TSX @focus3 again but will likely give that a shot too -- but the PWI4 process at least this time worked great. 

 

Charlie

[GaryShaw]

 

During daylight I just ran the Hedrick focuser from 0 out to maximum range and see the tick counter at 39312...so to first approx let's say 1.3 tick/micron or 0.76 micron/tick.  

 

Hi Charlie,

I’ve had no clear nights since your post so have made no progress getting to know the scope. I’m planning today to check my Hedrick versus what you reported in the quote above regarding the end position. Could you explain what you mean by “tick”. I plan to simply note the starting and ending ‘positions’ - just see how many 1 micron steps (step size per Bill Dean) I get at the full-out position. Will post the outcome. 
Gary 

[GaryShaw]

I tried some daylight testing on the focuser movement. I expected its range of motion for the 1.3" of travel its supposed to have, to yield a full-out micron reading of 33,020. The most I got was a bit over 30,000 and I was unable to repeat that a second time.

 

When I racked it in to begin with, it went to -7. I tried again and it went to 1. One prior time when I first used it, I was -7 or -8. I wondered why I'd get negative numbers at the low end. Now, I wonder why I get inconsistent numbers at the high end. None of this matters of course, if it can work with TSX, NINA or PIW4 to achieve reliable autofucus results.

 

I would be interested to hear whether the behavior I've mentioned is out of whack with what others have experienced. Charlie, Dan, Rouz ?

 

Thank you,

Gary