×

INDI Library v1.8.0 is Released (27 Jul 2019)

INDI Library v1.8.0 is mostly a maintenance release to fix a few bugs in several drivers.

Focus Module revisited

  • Posts: 43
  • Thank you received: 7

Focus Module revisited was created by MikeCEM60

Currently EKOS arrives at best focus by moving the sensor "in" and "out" with decreasing amplitude, thus arriving at minimum HFR value.

My home built focuser is belt driven, thus backlash in the system becomes an issue: this could be avoided:

First HFR is mapped in one direction (e.g.: "in" movements only) from outside to inside of best focus position. Once the V curve is established the focuser would rewind to its start position, and incrementally, using only "in" commands arrive at HFR minimum. Backlash avoided, that should eliminate most failed autofocus procedures.

Thanks
Michael
The following user(s) said Thank You: sterne-jaeger
1 month 2 weeks ago #40789

Please Log in or Create an account to join the conversation.

  • Posts: 934
  • Karma: 6
  • Thank you received: 239

Replied by wvreeven on topic Focus Module revisited

Michael, I don’t understand. Belt driven systems are known for their low backlash or even complete absence of it. My home built focuser is belt driven and has 0 backlash. Wouldn’t it be possible to eliminate the backlash completely?


Wouter
ASI1600MM-Pro Cooled and filter wheel with a SkyWatcher Esprit 80 ED on a SkyWatcher HEQ5-Pro

ASI1600MM-Pro Cooled and filter wheel with an 8" TS Ritchey-Chrétien on a SkyWatcher EQ6-R
1 month 2 weeks ago #40814

Please Log in or Create an account to join the conversation.

  • Posts: 268
  • Karma: 5
  • Thank you received: 82

Replied by sterne-jaeger on topic Focus Module revisited

I have the same problem as Michael with my Optec PDMS focuser. It is belt driven, but has nevertheless a backslash of 50-80 ticks.
1 month 2 weeks ago #40819

Please Log in or Create an account to join the conversation.

  • Posts: 166
  • Karma: 1
  • Thank you received: 29

Replied by DerPit on topic Focus Module revisited

My Pegasus DMFC fortunately has an internal driver setting to specify backlash.
But I do agree that it would be valuable to have a focus mode in EKOS that can take care of backlash by itself, for those that cannot set it in the driver.
A simple solution would be to have the focusser approach dialed-in values always from the same side, with a definable overshoot. I.e., to go from 10000 to 9950, it first goes down to 9800, and then up again to 9950.
Should of course be optional, so people with driver-internal backlash compensation can switch it off.
openSUSE Tumbleweed KStars git INDI git
GPDX+EQMOD, CEM60EC, ASI1600+EFW+ASI290 mini
1 month 2 weeks ago #40828

Please Log in or Create an account to join the conversation.

Replied by knro on topic Focus Module revisited

Patches are welcome! An option can be added to mimic this behavior. Anyone needs help in setting up their development environment?
Jasem Mutlaq
Support INDI & Ekos; Get StellarMate Astrophotography Gadget.
How to Submit Logs when you have problems?
Add your observatory info
The following user(s) said Thank You: Blueshawk
1 month 2 weeks ago #40837

Please Log in or Create an account to join the conversation.

  • Posts: 166
  • Karma: 1
  • Thank you received: 29

Replied by DerPit on topic Focus Module revisited

knro wrote: Patches are welcome! An option can be added to mimic this behavior. Anyone needs help in setting up their development environment?


That part is not the real problem. It's more understanding C++ and the layout of the code. KStars/EKOS is a complex beast and not the best starting point to learn I'm afraid :(

(Just wanted to have a look at what is needed to add also the Hour Angle to the "Mount & Alignment" overview, instead of issuing a wish. But even that looked to me like Olympus Mons to an ant :ohmy: )
openSUSE Tumbleweed KStars git INDI git
GPDX+EQMOD, CEM60EC, ASI1600+EFW+ASI290 mini
1 month 2 weeks ago #40880

Please Log in or Create an account to join the conversation.

  • Posts: 37
  • Thank you received: 4

Replied by Megiddo on topic Focus Module revisited

Unless your belt is tight... I don't see how there wouldn't be backlash. I have mine loose enough to get off so I can do large adjustment. I just put a 'bar' on one side of the belt to take out some slack, but slide the bar out and I have slack enough to get it off the gears.
1 month 1 day ago #41270

Please Log in or Create an account to join the conversation.

  • Posts: 186
  • Karma: 2
  • Thank you received: 54

Replied by Lead_weight on topic Focus Module revisited

Most focuser motors have a gearbox, this is where the backlash comes in. It’s not typically from the belt.
-Andrew
––––––––––
Mac Observatory - All about using the Mac for Astrophotography: www.macobservatory.com
Astrobin: www.astrobin.com/users/Lead_Weight/
The following user(s) said Thank You: El Corazon, MikeCEM60
4 weeks 1 day ago #41355

Please Log in or Create an account to join the conversation.

  • Posts: 43
  • Thank you received: 7

Replied by MikeCEM60 on topic Focus Module revisited

Well, that is probably true for the pro units, but if you have a 3D printer, and too much time on your hands?



Last edit: 4 weeks 4 hours ago by MikeCEM60.
4 weeks 4 hours ago #41376
Attachments:

Please Log in or Create an account to join the conversation.

Time to create page: 0.639 seconds