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Equipment Discussions >> Mounts

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mistyridge
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Re: LOSMANDY GEMINI 2 GOTO SYSTEM new [Re: dawziecat]
      #5667615 - 02/07/13 06:23 PM

I have not updated my firmware since July 2012. I just use the mount visually. Are the changes since then sigificant?

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Raginar
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Reged: 10/19/10

Loc: Rapid CIty, SD
Re: LOSMANDY GEMINI 2 GOTO SYSTEM new [Re: mistyridge]
      #5667724 - 02/07/13 07:37 PM

No.

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nemo129
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Re: LOSMANDY GEMINI 2 GOTO SYSTEM new [Re: neilson]
      #5667781 - 02/07/13 08:17 PM

Quote:

Hi Terry D.
You stated your using fl up to 600mm. There's a big difference when your imaging DSO's at 3250mm fl. I need my goto's to be dead on. At up to 600mm is so wide field you might not even notice it being off a little but at 3250mm fl. it becomes a problem.

I'm glad your Gemini 2 has no issues.



Neilson




Hi Neilson,

While I am not currently using the huge fl you are using, I routinely use an AT8RC at 1625mm and like Terry I only use 3 or 4 alignment stars and the G11-Gemini 2 combo puts my targets on my ST8300 chip every time. Before I sold it, I did image with an 11" EdgeHD at 2800mm with a Canon 450d and my goto's were similarly as accurate. My experience with the Gemini 2 has been very positive in the 2 years I have been imagining with it so I have to give it a positive vote.


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neilson
professor emeritus


Reged: 08/22/10

Re: LOSMANDY GEMINI 2 GOTO SYSTEM new [Re: nemo129]
      #5667929 - 02/07/13 09:56 PM

Hi Kirk,
Were they dead center every time all over the sky. My CGEM DX was dead center in the eyepiece and imaging chip every time. My G11 has yet to give me even one item dead center. I can even sync. then slew away then tell it to go back to the star and it will always be off from center or to the edge. Tonight I tried only a 4 star model after a polar alignment but my slews were off to the edge, even Jupiter was off.
I do have to say one thing, the moon has been centered most of the times perfectly. I would of expected it to be the opposite.

I know this is being nit pickey since at least a part of each DSO is in the eyepiece. But I feel since I paid over $1,000. more for the G11 than my CGEM DX it should be at least as accurate as Celestrons Nexstar. The goto accuracy was the one thing that impressed me the most on my DX. I read about others pointing out how their Celestron mounts puts targets dead center every time too. Even My Meade LXD75 and LX200R are both more accurate than my G11. I notice quit a few people using expensive goto software on their G11's. I wouldn't doubt they were wanting more accurate goto's as one reason. And if your mount does get every target centered every time all over the sky then that is great. But mine does not and I think it should.
This is not a deal breaker item but I think it should be addressed and corrected. Having goto's that are fine or ok or just good doesn't cut it after using much cheaper mounts with consitant excellent goto's.

I can't say Gemini 2 is better than Nexstar or even as good as it is when it comes to goto's.

neilson


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jrcrillyAdministrator
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Reged: 04/30/03

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Re: LOSMANDY GEMINI 2 GOTO SYSTEM new [Re: neilson]
      #5667940 - 02/07/13 10:02 PM

Quote:

I can even sync. then slew away then tell it to go back to the star and it will always be off from center or to the edge.




That's usually a symptom of a slipping clutch. A less common cause is bad encoder reads.


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neilson
professor emeritus


Reged: 08/22/10

Re: LOSMANDY GEMINI 2 GOTO SYSTEM new [Re: jrcrilly]
      #5667996 - 02/07/13 10:35 PM

Hi John,
My new mount's clutches were slipping bad. I called Scott and he told me that I had the wrong clutches by mistake. He sent new different ones. Now my mount does not slip. They hold really good now and I am much happier about that. I was expecting this to fix my goto's. I have tested and tested but the problem is still there. I had hoped the clutches were the cause, but they were not.

Thank you for the suggestion.
I dont know how to test the encoders but I have switched the RA with the DEC motors then back hoping it might be a motor. But no luck there.

neilson


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jrcrillyAdministrator
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Reged: 04/30/03

Loc: NE Ohio
Re: LOSMANDY GEMINI 2 GOTO SYSTEM new [Re: neilson]
      #5668159 - 02/08/13 12:04 AM

Quote:

I dont know how to test the encoders but I have switched the RA with the DEC motors then back hoping it might be a motor. But no luck there.

neilson




The only other common issues (serious backlash or mechanical slop) are very unlikely in a mount of that class. The test you describe is perfect for diagnosing the problem, as it eliminates alignment errors completely. I'd watch closely to see whether the error on returning to the star is in one or both axes. If it's both, I'd look very closely at the OTA mounting for slop and look for backlash in both axes. If it's only one axis, then the first two I mentioned are still the most likely suspects but you can check backlash as well.


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neilson
professor emeritus


Reged: 08/22/10

Re: LOSMANDY GEMINI 2 GOTO SYSTEM new [Re: jrcrilly]
      #5668232 - 02/08/13 01:29 AM

Hi John,
I have checked those things before but I will go back and check them more carefully tomorrow. I appreciate you helping me. Thank you

neilson


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Charlie B
scholastic sledgehammer


Reged: 03/22/08

Loc: Sterling, Virginia
Re: LOSMANDY GEMINI 2 GOTO SYSTEM new [Re: jrcrilly]
      #5668490 - 02/08/13 08:49 AM

Quote:

That's usually a symptom of a slipping clutch.




This would be my guess as well. I bought a $4.99 strap wrench from Sears because I could not hand tighten my clutches enough to keep them from slipping. The tri-knobs were too expensive for me but the strap wrench works fine. Even with the strap wrench, I've had slippage if I've not bundled the cables correctly.

Charlie B


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nemo129
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Re: LOSMANDY GEMINI 2 GOTO SYSTEM new [Re: neilson]
      #5668570 - 02/08/13 09:28 AM

Hi neilson,

Quote:

Were they dead center every time all over the sky.




I set up fresh each night that I image, so I build a new model each time. I start (polar align) with getting all 3 stars set up in the PAS. I guess I am lucky as my PAS works very well (verified by occasional drift checks). When I am building my model I used to use a 12mm centering EP. The first star on a given side of the meridian is normally way off excepting a few very lucky times! The second star is usually in the FOV of the 8 x 50 finder and the third is usually very close to the center of my EP. Subsequent stars, if I add them are very close or dead on the center. I recently started using my guidescope (optics aligned to the main OTA) to build my model as it is easier to sit at my laptop and center stars than doing refractor prayers or contorting myself when using my imaging newt. It also saves me from having to rebalance the mount after I add the main imaging camera and filterwheel.

As for imaging, as it pertains to your question; at lower fl like on my 80mm APO at 480mm or my SV105 at 735mm pretty much dead on. No as much at longer focal lengths, but always on the chip. I seldom image what the goto gives me anyway as I am sure most folks like us will frame a shot after they find the object. There have been times that the mount has hit my target perfectly. It is not the rule though!

(Note: I normally only build east models and if I flip at meridian I add two stars in the west and use the bookmark feature to return to my target and do a manual plate solve if needed)

As to why you are seeing targets off center after proper alignment, I cannot explain. I have seen that as well but it always ended up being my own user error. Most commonly I picked the wrong star in the model. I'm not saying you are making mistakes, just commenting on why I think I have seen the issue.

On the subject of the G11/G2 costing $1K more than the CGEM-DX, I think it has a lot to do with mount construction and where it is made. I owned a CGEM before the G11 and IMHO the G11 is a better made mount using machined parts instead of sand cast parts. You certainly have a much better tripod than I had with my CGEM, so I have no comment there, only that the Losmandy HD tripod is much better than the original CGEM tripod. BTW I really loved and miss the Celestron firmware. Simple to use and as you said very accurate. It is certainly an area where Celestron has a clear advantage. Again, just my opinion.

I absolutely agree that you should be able to achieve more accurate goto's than you are currently getting. I would expect better than what you described.

Finally, (sorry for the long post) I am personally not happy about the lack of progress on the Gemini 2 firmware as of late. Sure it is functional and it gets the job done for me right now, but it could be better and there are reported and confirmed issues that need to be addressed as well as features that need to be improved(PAC for one!) and added (electronic assisted axis balancing).


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neilson
professor emeritus


Reged: 08/22/10

Re: LOSMANDY GEMINI 2 GOTO SYSTEM new [Re: nemo129]
      #5668797 - 02/08/13 11:37 AM

Hi Kirk,
To me it sounds like your not getting much better accuracy than I am at longer focal lengths. At 480mm and such light weight mine would probably look somewhat centered just fine too. Its at longer focal lengths where it becomes noticable. I am using the exact OTA setup that I was using up until November on the CGEM DX.
I have a 9.25 Edge with a 2" flip mirror so I don't have to rebalance. I have an orion 80mm short tube on top with a DSI 2c as a guidescope. I use a 12mm illuminated reticule for alignment. I was even able to consitantly get my goto stars on the DX in the center of that reticule.
I level my mount with a nice carpenters level each time. I take time to balance my mount perefectly since its very sensative. I have never had a mount this picky about balance.

When I do my alignment I just use every star that the Gemini 2 gives me. Then I flip to do the West model then go back and redo several of the East model stars. I have marks on the ground to setup my tripods that I have used for years. I use "Polar Finder" software to tell me where in my finder to put Polaris. My PAC's accuracy is off about the same as my goto's. It was much worse before the new clutches. These clutches hold really good now.
I use leather work gloves to tighten them. I will buy the other knobs next month. Some times I do an East model, PAC, Drift, goto CWD, turn mount off then on(cold start) and start East/West models. Sometimes just a drift, CWD, off/on(cold start), then East/West models.

You mentioned that you did plate solving. I'm not experienced with that but it sounds like your using aftermarket software to help with your alignment. If so, Why are you needing that?

This accuracy is fine for wide field but not long focal lengths. It would of been ok 3 or 4 years ago but it's behind Meade and Celestron now. This mounts price point calls for better accuracy.

The Gemini 2 goto sells for $1,595.00 . The entire CGEM mount with goto costs $1,499.00 . The CG-5 is a lot less. That tells me the Gemini 2 costs about 3 times more than Nexstar. I expect it to be at least as good as Nexstar, not just acceptable. You mentioned how the mount is machined instead of cast aluminum. I agree, This is a higher grade mount. I think the firmware should be too. When I image DSO's that I can't even see, it would be nice if the mount centered them on my chip. Especially after all the work and time I spend doing a full East and West alignment. I don't think my mount is performing any worse than anyone elses who are using my fl. I haven't read anywhere that anyone who's using this mount with at least 3250mm fl without other software helping is consistantly getting all their goto's centered on their chip and/or eyepiece of 15 or 20mm. If Nexstar can have that good of accuracy then why can't Gemini 2.

neilson


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Raginar
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Reged: 10/19/10

Loc: Rapid CIty, SD
Re: LOSMANDY GEMINI 2 GOTO SYSTEM new [Re: nemo129]
      #5668851 - 02/08/13 12:02 PM

Kirk,

Is PAC and axis balancing really that important to you? I think it's a neat 'gee whizz' feature, but there are so many other software options if that's what you're looking for (and doing AP). Otherwise, the current PAC is plenty usable.

I agree, I want them fixed too. But look at Synta's software, they're just now picking up PAC. Axis balancing is a relatively new concept too. And, neither of these are available for AP people (without other software).

I dunno, I'm pretty happy with where it's at. Definitely not Celestron, but it's not too shabby.


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neilson
professor emeritus


Reged: 08/22/10

Re: LOSMANDY GEMINI 2 GOTO SYSTEM new [Re: Raginar]
      #5669033 - 02/08/13 01:27 PM

Celestrons All Star Polar Alignment is very accurate. I usually imaged without doing a drift alignment.
After doing PAC I still need to do a drift. Even after doing the PAC 2 or 3 times I still needed the drift. I did a drift then tried PAC and it had me move the mount out of alignment. Try it some time.
Usable, it depends what you consider usable.
And if your just doing visual or AP.

neilson


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Raginar
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Re: LOSMANDY GEMINI 2 GOTO SYSTEM new [Re: neilson]
      #5669549 - 02/08/13 06:19 PM

Neilson,

I'll just keep using something else then. I'm sure they'll get around fixing it someday. As long as it continues to control my mechanically superior mount... I'm happy . My issue with the CGEM was that it couldn't perform mechanically.

The MI250 rocks!


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neilson
professor emeritus


Reged: 08/22/10

Re: LOSMANDY GEMINI 2 GOTO SYSTEM new [Re: Raginar]
      #5669832 - 02/08/13 09:54 PM

Hi Raginar,
I see you have an MI250. I just saw some pictures of one. That is an increadable looking mount. I wish I had one of those.
I recieved my new G11 mount with a number of serious mechanical problems. I blamed them for my Gemini 2's issues. But as the mechanical problems are getting fixed my Gem2 is still the same. Once my mounts mechanical issues are fixed, I wouldn't give it up for a Meade or Celestron mount. But I do find it hard accepting the Gem2 after using the NexStar.
I have been watching Rene fix things and add things that people want to make the Gem2 better, but only after its requested. If there are a lot of people saying the accuracy is good enough as long as its in the eyepiece somewhere then thats as good as it will ever be.
But if we ask him if he would improve the accuracy so that items are centered, especially DSO's for imaging, I bet he would do it.

And yes I emailed him a request to increase the goto and PAC accuracy about a month ago. But If others let him know its wanted he might go ahead and improve the goto's and PAC's accuracy.

Neilson


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Raginar
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Re: LOSMANDY GEMINI 2 GOTO SYSTEM new [Re: neilson]
      #5669896 - 02/08/13 10:25 PM

I agree completely. It's amazing the difference a mechanically sound mount makes.

BTW, did my first 'full' setup with modeling. Surprisingly easy to accomplish, completely spot on with not being that accurate. And, you definitely need to build models on each side of the meridian.

Edit: So I was examining the data I got from my new pointing model after using PEMPRO. Have you guys ever paid attention to how sensitive it is to the pointing model? The numbers for it's polar alignment significantly changed depending on where I was in the model. Perhaps that is the issue we're running into when using PAC?

Edited by Raginar (02/08/13 11:11 PM)


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neilson
professor emeritus


Reged: 08/22/10

Re: LOSMANDY GEMINI 2 GOTO SYSTEM new [Re: Raginar]
      #5669959 - 02/08/13 11:27 PM

Hi Raginar,
Wow thats great. I wonder if different models of mounts make a difference on quality of accuracy.
I am thinking of swapping out my gearbox to see if it helps. I had noticed on mine that I definately have to make a model of both sides for goto's also.
What ota are you using on it.

I am glad you are getting good results with that real nice mount.

neilson


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mistyridge
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Reged: 10/28/05

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Re: LOSMANDY GEMINI 2 GOTO SYSTEM new [Re: neilson]
      #5670064 - 02/09/13 02:09 AM

Check your coordinates....Lat - Lon. and time clock. If you are off on all your gotos by the same amount that could be the problem.

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Hilmi
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Reged: 03/07/10

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Re: LOSMANDY GEMINI 2 GOTO SYSTEM new [Re: mistyridge]
      #5670088 - 02/09/13 02:54 AM

Have you tried flashing the sram? That would clear any corrupt settings.

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orlyandico
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Re: LOSMANDY GEMINI 2 GOTO SYSTEM [Re: Hilmi]
      #5670108 - 02/09/13 03:29 AM

If Celestron sold a $1000 retrofit nexstar and motors, with programmable gear ratios, I suspect there would be a market.

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