Jump to content


Photo

Losmandy G11 with Gemini II questions

  • Please log in to reply
20 replies to this topic

#1 Lane

Lane

    Soyuz

  • -----
  • Posts: 3586
  • Joined: 19 Nov 2007
  • Loc: Frisco, Texas

Posted 27 October 2012 - 01:32 PM

I have A few questions for anyone that has one of these mounts with the Gemini II:

1. I see all kinds of bug reports for Gemini II from last year, are these bugs resolved now?

2. When I go camping and other campers are trying to sleep nearby, I need to eliminate the noise of the GOTO. During those times can I still push the mount and then just use the Gemini for the final centering at low speed?

3. If the answer to 2 is yes, then when I move the mount manually will I be able to look at the Gemini hand controller and determine when I have reached the object? In other words will it work just like having a Sky Commander or something like that attached.

4. Will I be able to attach the Southern Stars Skyfi unit to the Gemini II and run the mount wirelessly from Sky Safari with my iPad?

Thanks in advance for any answers you can provide.

Lane

#2 dawziecat

dawziecat

    Vanguard

  • *****
  • Posts: 2229
  • Joined: 20 Oct 2010
  • Loc: Rural Nova Scotia

Posted 27 October 2012 - 02:00 PM

I have A few questions for anyone that has one of these mounts with the Gemini II:

1. I see all kinds of bug reports for Gemini II from last year, are these bugs resolved now?

2. When I go camping and other campers are trying to sleep nearby, I need to eliminate the noise of the GOTO. During those times can I still push the mount and then just use the Gemini for the final centering at low speed?

3. If the answer to 2 is yes, then when I move the mount manually will I be able to look at the Gemini hand controller and determine when I have reached the object? In other words will it work just like having a Sky Commander or something like that attached.

4. Will I be able to attach the Southern Stars Skyfi unit to the Gemini II and run the mount wirelessly from Sky Safari with my iPad?

Thanks in advance for any answers you can provide.

Lane


#1. I've had G11-Gemini II since March 2011 so have seen it all. The software was largely non-functional at that time with only the most basic GOTO functionality and only one star alignment possible. That changed in Jun 2011. Gemini II has been eminently useable since that time and all the carping about bugs and dis-functionality have been way overblown! Usually by people who don't own it! I've been using it for astrophotography quite successfully since that time.

#2 and #3. No! If you push the mount manually, Gemini II will become lost. Furthermore, if you have limits set to prevent crashing the motor against the mount head, Gemini will have an incorrect limit location and either stop tracking inappropriately because it thinks a crash is near or, worse, a crash will occur.
Be aware that Gemini will NOT know where it is after you manually push it.

#4. No experience on that here.

It's a great mount! Forget the hysteria about how it is buggy! No manual yet though, making it a bit hard to figure the myriad of features out.

#3 terry59

terry59

    Aurora

  • *****
  • Posts: 4615
  • Joined: 18 Jul 2011
  • Loc: Colorado, USA

Posted 27 October 2012 - 02:27 PM

Lane - I have a GM8 and a Sirius. The GM8 slews much more quietly than the Sirius. I know that is a big issue for you.

#4 Dan Finnerty

Dan Finnerty

    Messenger

  • -----
  • Posts: 422
  • Joined: 11 Sep 2011
  • Loc: Pasadena, CA

Posted 27 October 2012 - 02:58 PM

Lane,

1) with the latest updates to the firmware, the bugs are gone. I got mine a year ago and star alignments were driving me crazy. All that is gone now. For AP, the software now incorporates PEC, but I've not tried that out yet. Some interesting new features are being incorporated as well, so the software continues to evolve in a positive direction. Check out Tom Hilton's Gemini web site and the Gemini II Yahoo forum, lots of information and help. Tom provides a wonderful service to Losmandy users!

2) the only solution to noise abatement is to slew at lower rates, which helps significantly. You can set slew rates via the hand controller. Dawziecat already gave you a good answer to the consequences of push-to. The telescope loses its position knowledge. However, you can resync to a known star (not re-align) and reset the mounts knowledge of its pointing. That can be a big help if you bump the OTA and the clutches slip. I've used it a number of times for just that reason.

3 is already answered by 2 above...

4) I have the SkyFi unit and SkySafari and it is a wonderful system. The SkySafari software is the best I've come across. I use my iphone (an ipod works as well) for convenience sometimes but the buttons are too small for convenienece. The iPad is wonderful. It is like having an astronomy book connected to the telescope. You tap on the info button and get a detailed description of the object you have centered on, along with high-res images. I think the new iPad mini might just be the best thing yet, as the iPad gets a bit big in the hands sometimes. Also note that android phones are supported by the software as well. I hesitated at first to get the SkyFi unit, as it is a bit pricy. The SkyWire connector is relatively inexpensive and works perfectly. However the freedom of the wireless connection is worth it if you can swallow the price of admission. Also, with the latest SkyFi firmware, you can now set up the unit to connect through your home wireless network if you have one rather than a dedicated ad-hoc network, thus you can surf the internet for more info if you want (or email your wife about what an incredible view she is missing by going to bed rather than standing around in the cold with you). An incredible educational/outreach tool.

Hope this helps!

#5 mega256

mega256

    Viking 1

  • *****
  • Posts: 925
  • Joined: 10 May 2007
  • Loc: N of Tampa

Posted 27 October 2012 - 04:05 PM

Tom has 2 wonderfull sites and great help..

http://tech.groups.y...roup/Gemini-II/

This is the G2 site with online simulator help.

http://gemini-2.com/

Iv had my G11-G2 (6-11-11) and I think its a great system
and the touch screen is so nice to use.. Now a Very solid system. I belive that the new G11-G2 systems are shipping with the new HD losmandy motors,,,they are very powerfull,But there may be some extra noise,but can be set up to slew slower,and takes care of most of it.

#6 pfile

pfile

    Gemini

  • -----
  • Posts: 3163
  • Joined: 14 Jun 2009

Posted 27 October 2012 - 11:33 PM

i just got one of these mounts a few months back.

i think i got unlucky and i have an RA worm with 20 arcsec pk-pk periodic error. that in and of itself is not a bad thing, but the worm does have some spots where the rate in arcsec/sec is too high, and my guider can't react fast enough. hence even with an OAG i still have some slight elongation at 1100mm. i am dreading adjusting the worm and/or replacing it with the one-piece block/ovision worm as the adjustment seems very difficult.

bug wise, yes, i do see some strange behavior. it seems to swallow short DEC pulses sent by the ST-4 port, and sometimes it just goes insane while being guided and overreacts wildly to the inputs. in this case i've had to reboot the G2, but the swallowed DEC commands seems to have no solution.

if you are not doing astrophotography, then i guess the above is not relevant for you.

on #4, i did this once using WiFiScope to allow Sky Safari to connect to the Gemini 2. it turns out that there are 2 standards for longitude, one where - means West and one where - means East (seriously...). SkySafari tried to set the location of the mount, and you guessed it, it uses the opposite convention from the G2. i was very confused by that for a while, as the scope pretty much refused to slew to any star i could plainly see above my head. so perhaps it is wise to turn off SkySafari's automatic location setting.

#7 pfile

pfile

    Gemini

  • -----
  • Posts: 3163
  • Joined: 14 Jun 2009

Posted 27 October 2012 - 11:36 PM

wow, i did not realize this about the consequences of pushing. does that mean that there are no encoders on the axes themselves, but instead all pointing information derives from the encoders in the servomotors?

#8 Hilmi

Hilmi

    Soyuz

  • *****
  • Posts: 3604
  • Joined: 07 Mar 2010
  • Loc: Muscat, Sultanate of Oman

Posted 28 October 2012 - 12:28 AM

Pfile,

Do you have the latest firmware?

#9 Lane

Lane

    Soyuz

  • -----
  • Posts: 3586
  • Joined: 19 Nov 2007
  • Loc: Frisco, Texas

Posted 28 October 2012 - 12:44 AM

Interesting information guys, thanks. I guess Gemini II is not for me. I think I will go with a non-Gemini model assuming I can still add the encoders and DSCs. I guess buying a used one in this configuration is another option.

#10 orlyandico

orlyandico

    Fly Me to the Moon

  • *****
  • Posts: 5281
  • Joined: 10 Aug 2009
  • Loc: Singapore

Posted 28 October 2012 - 02:30 AM

doesn't the gemini g2 have an RJ45 encoder input?

the only challenge is that losmandy no longer makes the encoder hardware so you'd need a kludge bolt-on from a 3rd party..

#11 Dan Finnerty

Dan Finnerty

    Messenger

  • -----
  • Posts: 422
  • Joined: 11 Sep 2011
  • Loc: Pasadena, CA

Posted 28 October 2012 - 12:26 PM

Interesting information guys, thanks. I guess Gemini II is not for me. I think I will go with a non-Gemini model assuming I can still add the encoders and DSCs. I guess buying a used one in this configuration is another option.


What mounts DO have position encoders? My CG 5 does not. I don't think any of the Celestron mounts do. I've never really thought about this before, it is just the way things seem to be. In the quest for inexpensive goto mounts, this feature seems to not be widely supported.

The g11 mount does have encoder mount points machined on to the ra and dec housings. Too bad Losmandy does not market the encoders any more. I would be interested in retrofitting them. It would certainly improve the operability of the mount -- if implemented properly.

#12 dawziecat

dawziecat

    Vanguard

  • *****
  • Posts: 2229
  • Joined: 20 Oct 2010
  • Loc: Rural Nova Scotia

Posted 28 October 2012 - 01:52 PM

The g11 mount does have encoder mount points machined on to the ra and dec housings. Too bad Losmandy does not market the encoders any more. I would be interested in retrofitting them. It would certainly improve the operability of the mount -- if implemented properly.


I blundered into this "pushing Gemini II manually" early in my experience with the mount. I did not understand what the problem was when my GOTOs went all to heck and was nonplussed when the mount just stopped dead for no reason apparent to me. It had encountered the limit I had set but I did not understand that at the time. There is no manual explaining this complex beast! It is easy to get frustrated and blame the mount for behaviour that seems whacky. I think we saw a lot of that in the early days of Gemini II. Now, thanks almost totally to Tom Hilton, Gemini II users are a more sophisticated bunch.

However, there is a point where I would certainly ask myself where I would stop upgrading the G11- Gemini II. Recently I was wondering if my mount was tracking badly. I made the decision that I would not spend more money on it to find out. If I needed the worm upgrade, I was not going to get it. If I needed better tracking, I would sell the G11 Gemini II and buy a Mach 1 rather than chase retrofitted upgrades that seem not always to be fully satisfactory for everybody. That said I had precious little trouble when I decided to adjust my worm mesh in RA. It was easy. Maybe I was just lucky. People seem to fear this task. I did too but, in retrospect, it was not the problem and there there was no need. My RA worm backlash was not excessive. Now, after tweaking it, it is virtually non-existent!

So, after a great deal of diddling about, it seems my G11 has always tracked perfectly well. My problems were/are elsewhere. So I do not see myself getting a new mount after all. And I like Gemini II very much! It amazes me what it can do! And I LOVE, and use nightly, the bookmark feature to check focusing and refocus between filters. I guess I have become at home with Gemini II and am reluctant to leave it.

It would be nice if you could push Gemini manually. Personally though I don't think I would buy add-on encoders to permit me to do this. They sound finicky and are likely
expensive.

You reach a point doing upgrades where I think you would have been better off just buying a better mount in the first place.

Only upgrade I would consider now is the new AP Polar Alignment Scope. it they make it compatible with the G11, I will buy it. I hope they will.

I can't address the noise issue Lane seems concerned with. The G11 is not silent but it seems unlikely that the noise it generates would be a big deal in a campground to me. But maybe . . .
It was news to me that you can vary the slew rate if noise is a concern. Just another in an amazing list of features in Gemini II software IMO.

#13 pfile

pfile

    Gemini

  • -----
  • Posts: 3163
  • Joined: 14 Jun 2009

Posted 28 October 2012 - 03:05 PM

Pfile,

Do you have the latest firmware?


hi hilmi, yes, i believe i do. i updated it about 3 weeks ago using the firmware update program.

#14 pfile

pfile

    Gemini

  • -----
  • Posts: 3163
  • Joined: 14 Jun 2009

Posted 28 October 2012 - 04:50 PM

That said I had precious little trouble when I decided to adjust my worm mesh in RA. It was easy. Maybe I was just lucky. People seem to fear this task. I did too but, in retrospect, it was not the problem and there there was no need. My RA worm backlash was not excessive. Now, after tweaking it, it is virtually non-existent!


well, it isn't just about adjusting out the RA backlash. there's the competing requirement that the worm/wheel interface be smooth enough along the whole 360 degrees of the wheel such that it does not bind. and then there's the fact that with the two-piece worm block, making sure the worm is being held exactly perpendicular to the worm is difficult to achieve. and of course making sure both worm blocks are axially aligned with one another. and then there's the whole question of whether you should polish your worm/wheel to get better PE performance.

i'm pretty sure i'm just looking at PE issues. guiding with an OAG, i can see in a stack of 60 7-minute subs that the star elongation is entirely in RA, with no DEC component. this tells me that either there's too much backlash, or the slope of the PE curve is just too great to correct quickly enough with autoguiding. i never see PhD struggling to reverse RA direction during calibration, so i don't think i have a problem with backlash.

i have yet to get a good PEMPro upload. who knows, this might be the solution for me. i'd be happy about that, if i can get it working. in fact, now i wonder why i didn't ask ray gralak about this at AIC. that was dumb...

#15 Lane

Lane

    Soyuz

  • -----
  • Posts: 3586
  • Joined: 19 Nov 2007
  • Loc: Frisco, Texas

Posted 28 October 2012 - 06:17 PM

I can't address the noise issue Lane seems concerned with. The G11 is not silent but it seems unlikely that the noise it generates would be a big deal in a campground to me. But maybe . . .
It was news to me that you can vary the slew rate if noise is a concern. Just another in an amazing list of features in Gemini II software IMO.


It is the difference between staying at the campground and being told I have to leave because other campers are complaining about the noise. After 10pm some places are very strict about the noise level, it just depends on the campground. I was at Horsethief Campground near Canyonlands just two months ago and after 10pm I could hear people whispering in their tent at the adjoining campsite. I could hear someone walking on the gravel road from their tent to the bathroom 5 campsites away. Even on a very slow slew speed the fairly quiet Sirius mount sounds very loud at that campground. So I am not looking to reduce the noise I need to eliminate it. I already have some push-to mounts but they cannot handle the 6" or the C11. And the lack of DSC's is no big deal if all I want to view are the brighter DSO's but for the faint stuff it would be way to time consuming trying to manually locate everything. I would just get a Discmounts DM6 with DSC's which can probably handle the scopes, but I really would like tracking, it will help a lot when viewing at high power. Unfortunately it looks like the standard G11 plus Losmandy DSC's will cost as much as a G11/Gemini unit.

#16 Ray Gralak

Ray Gralak

    Vendor (PEMPro)

  • -----
  • Vendors
  • Posts: 328
  • Joined: 19 Apr 2008

Posted 28 October 2012 - 06:23 PM

That said I had precious little trouble when I decided to adjust my worm mesh in RA. It was easy. Maybe I was just lucky. People seem to fear this task. I did too but, in retrospect, it was not the problem and there there was no need. My RA worm backlash was not excessive. Now, after tweaking it, it is virtually non-existent!


well, it isn't just about adjusting out the RA backlash. there's the competing requirement that the worm/wheel interface be smooth enough along the whole 360 degrees of the wheel such that it does not bind. and then there's the fact that with the two-piece worm block, making sure the worm is being held exactly perpendicular to the worm is difficult to achieve. and of course making sure both worm blocks are axially aligned with one another. and then there's the whole question of whether you should polish your worm/wheel to get better PE performance.

i'm pretty sure i'm just looking at PE issues. guiding with an OAG, i can see in a stack of 60 7-minute subs that the star elongation is entirely in RA, with no DEC component. this tells me that either there's too much backlash, or the slope of the PE curve is just too great to correct quickly enough with autoguiding. i never see PhD struggling to reverse RA direction during calibration, so i don't think i have a problem with backlash.

i have yet to get a good PEMPro upload. who knows, this might be the solution for me. i'd be happy about that, if i can get it working. in fact, now i wonder why i didn't ask ray gralak about this at AIC. that was dumb...

After you are done uploading your PEC curve to the Gemini you should do another Acquire Data run to make sure PE is reduced. Even if periodic error is reduced extra RA drift might be introduced by the Gemini's PEC algorithm, which I think could cause the elongation in RA that you are seeing. If it is excessive RA drift you can use the tool in PEMPro's Gemini tab to remove the drift.

-Ray

#17 pfile

pfile

    Gemini

  • -----
  • Posts: 3163
  • Joined: 14 Jun 2009

Posted 28 October 2012 - 11:35 PM

hi ray, yes, I have done that and right now the problem is that the PE goes absolutely nuts after uploading a curve with pempro. I have tried inverting the curve to no avail. if I train the PEC with Gemini-2 and ask pempro to retrieve the curve, I see a similar shape to the curve before inversion, so I think the curve is okay. this could have something to do with the guide rate that the curve is being played back at. I have not had time to debug it yet. should have done it tonight but I am too tired from AIC :)

if I remember right I do see RA drift after PE training with Gemini-2. the subs I am talking about above we're mostly aquired with PEC off.

is the drift thing a bug, or is it something fundamental about PEC that causes the drift?

#18 SMigol

SMigol

    Ranger 4

  • -----
  • Posts: 310
  • Joined: 30 Jul 2010
  • Loc: California, USA

Posted 29 October 2012 - 12:43 AM

The RA drift after using PEC is a known issue. It's wise to consider running the script that is available in PEMPro to do drift tuning.

Important things to note:
1. ensure that while tuning the mount does not cross the meridian.
2. ensure that you retain an east-bias in RA.
3. rough polar alignment is OK.
4. let the script run for a while and keep watching the results. note the time stamp of the one that comes the closest to 0 drift.

I've noticed that even when I let the script run for a dozen or more passes, the best result was after just 4 passes. I've noted this timestamp and removed all the other curves from the system to avoid confusion on my part.

Note that letting the mount do its own training should give a decent curve as well, but do expect that the RA drift will likely remain. I think that the cause is because the corrections for PEC are not summed to ensure that the RA rate is correct. Thus the measurements afterwards help tune for the curve.

#19 Ray Gralak

Ray Gralak

    Vendor (PEMPro)

  • -----
  • Vendors
  • Posts: 328
  • Joined: 19 Apr 2008

Posted 29 October 2012 - 07:34 AM

hi ray, yes, I have done that and right now the problem is that the PE goes absolutely nuts after uploading a curve with pempro. I have tried inverting the curve to no avail. if I train the PEC with Gemini-2 and ask pempro to retrieve the curve, I see a similar shape to the curve before inversion, so I think the curve is okay. this could have something to do with the guide rate that the curve is being played back at. I have not had time to debug it yet. should have done it tonight but I am too tired from AIC :)

if I remember right I do see RA drift after PE training with Gemini-2. the subs I am talking about above we're mostly aquired with PEC off.

is the drift thing a bug, or is it something fundamental about PEC that causes the drift?

The drift when PEC is applied seems to occur with both an uploaded curve and when you try to train PEC via the autoguider. To me this implies there is a bug somewhere in the Gemini's PEC logic.

If you want please post the logs here or on the CCDWare/PEMPro forum so I can get get a better idea of what you are seeing. Also, make sure you are using the latest PEMPro build and Gemini firmware.

-Ray

#20 pfile

pfile

    Gemini

  • -----
  • Posts: 3163
  • Joined: 14 Jun 2009

Posted 29 October 2012 - 10:36 AM

sure i will do that when the weather clears, thanks for the help.

#21 Startraffic

Startraffic

    Viking 1

  • *****
  • Posts: 739
  • Joined: 12 Feb 2006
  • Loc: Lat. 39.143345, Long. -77.174802

Posted 29 October 2012 - 11:51 AM

Lane,
The original Losmandy encoder are not available. You "can" get encoders from several other sources that will work. I have a set of encoders on my G11 that I have setup to work with the Gemini-1. I've upgraded my mount to a HGM-200 (the forerunner of the Titan) and moved my Gemini-2 to that. The HGM-200 has built in encoders but Gemini-2 doesn't support them at this time. I believe that support is one of the future features of G2. I hope so, I do a lot of outreach with the BSA with both Cubscouts (boys 6-11) & Boyscouts (Boys 11-18). The Boyscouts aren't too bad. They generally don't put their hands on the scope more than once. The Cubscouts do it everytime which moves the scope. With my G11 &, encoders & SkyCommander it was simple to move the scope back on target.

Clear Dark Skies
Startraffic
39.138274 -77.168898






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics