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LOSMANDY GEMINI 2 GOTO SYSTEM

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#101 neilson

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Posted 27 February 2013 - 12:08 AM

Hi Everyone,
I received a replacement Gemini 2 computer main box today. I tested it and the results are looking good.

I made an East model then slewed back to several alignment stars and they were fairly close to the center. I slewed to M42(orions nebula) and it was centered. This never happened before. I did a PE run using PHd with guiding disabled and the tracking was good. It ran slow before. I took a 2 1/2 minute guided image and my stars were round. They were football shaped before.
The only problem I had was when slewing to an East side star that was not near where any of the modeling stars were and it was outside the 12mm illuminated reticule eyepiece. This tells me I need to use all 12 alignment stars on both East and West models if I want all my goto's in my eyepiece.

My Gemini 2 still needs more testing to make sure since I just did 2 hours worth tonight. It's looking much better than it has the past 2 months.

It's not as good as my Celestron CGEM DX was. It just needs 2+4 stars and all the stars I goto were centered not just fairly close. If my G11 Gemini 2 keeps working as good as it did tonight then I will probably keep it.

They just released an update to the firmware so I will install it and test it tomorrow. Its supposed to fix some of the bugs. They hope to fix the rest of the bugs next update.

Neilson

#102 neilson

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Posted 27 February 2013 - 10:55 PM

Hi Everyone,
Well I installed the new firmware in my Gemini 2 today. I started testing my tracking and goto's. They were working good finally.

Then I wanted to slew to the horsehead nebula to image it. There is no Bernard catalog (Bernard 33) and it looks like they removed the IC catalog (IC434). It looks like the NGC catalog is gone also. No Caldwell, But there is the Messier catalog. And some others I never heard of. I think their star and double stars and things like that. I dont know if I'm supposed to enter the coordinates but I dont know any.

Then to make things worse the handbox locked up again. The only way to fix that is restart and do another 24 star model. No Way, I gave up for tonight.

Neilson

#103 Hilmi

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Posted 28 February 2013 - 12:42 AM

Catalogs can just be copied across thats not an issue. Hand controller locking is from shoddy design where they madethe box too tight a fit just slightly loosen the screws on the back of the box. I suspect they will be introducing a revised design of the hand controller soon

#104 neilson

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Posted 28 February 2013 - 01:04 AM

Hi Hilmi,
I already updated and no longer have the old firmware and I havent a clue how to copy them across.
I already tried loosening the screws on the handbox. At least every other day my screen locks up making me turn it off and restart it. Sometimes twice a day. Its very frustrating.

Neilson

#105 Hilmi

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Posted 28 February 2013 - 01:29 AM

Im happy with my Gemini II taking into account that it only now is maturing. Its the sloppy backlash and adjustment mechanism of my G11 that I am not happy with. I feel that for imaging this was a bad choice. I have outstanding native uncorrected PE that last night I measured at +/- 2.6 but then the DEC backlash makes guiding difficult in some orientations. Make Dec tight and it stalls, loosen it and you will have guiding difficulty. Adjustment mechanism is archaic and annoying

#106 neilson

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Posted 28 February 2013 - 02:02 AM

Hilmi,
That doesn't sound good. I hope you can get it worked out. I am happy with finally getting 8.5 arcseconds total PE. I'm hoping PEC will bring it down some more.
Do you have to re train the PEC each time you turn the mount off.

I just found out from TOM that the NGC by Didier has all the NGC items in it. And that Rene may have found an alternate IC catalog but it has to be converted to use with Gemini and should be updated later. Both catalogs could not be in the Gemini 2 for copywrite reasons and these alternate ones will work.
I am relieved.

neilson

#107 neilson

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Posted 28 February 2013 - 11:53 AM

Hi Hilmi,
Tom just said that you cannot copy the NGC or IC catalogs across because the Gemini 2 firmware looks for them and will delete them each time you power up. I can understand them not being allowed to include these catalogs but who's business is it what we install ourselves. My Gemini 2 came with NGC and IC catalogs already installed. What right do they have to erease them and not allow them. Well its not really a big deal because they are going to have alternate versions. And thats good enough for me.

neilson

#108 gdd

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Posted 28 February 2013 - 03:43 PM

Im happy with my Gemini II taking into account that it only now is maturing. Its the sloppy backlash and adjustment mechanism of my G11 that I am not happy with. I feel that for imaging this was a bad choice. I have outstanding native uncorrected PE that last night I measured at +/- 2.6 but then the DEC backlash makes guiding difficult in some orientations. Make Dec tight and it stalls, loosen it and you will have guiding difficulty. Adjustment mechanism is archaic and annoying



Does the Gemini-2 backlash compensation (TVC) help at all?

Gale

#109 Hilmi

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Posted 28 February 2013 - 10:45 PM

I have applied backlash compensation through MaxikDL with limited successs. But problem is still there.

#110 orlyandico

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Posted 28 February 2013 - 11:07 PM

every time i read one of these threads i thank the stars i didn't buy a G11... :tonofbricks:

it is simply mind-boggling that a $3600 mount should have such problems. I mean, one expects such issues with a CGEM and adjusts one's expectations. But not when you pay over twice!

(sorry, off topic)

#111 Hilmi

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Posted 28 February 2013 - 11:30 PM

Pretty much on topic. It's just like gambling, you feel one more time and you'll get it right. But you never really get there

#112 gdd

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Posted 01 March 2013 - 12:53 AM

have applied backlash compensation through MaxikDL with limited successs. But problem is still there.



I read that MaximDL performs backlash compensation by waiting a programmable length of time for the worm to reverse direction.

Gemini TVC uses a different approach, it reverses the direction of the motor at high speed for a programmable amount to quickly take up the slack and then resumes at normal guide correction speed. Might be worth an experiment to see which method works better. Or maybe those with experience in both methods can let us know.

Gale

#113 mistyridge

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Posted 01 March 2013 - 01:32 AM

I am still using last years update which seems to work OK for my use...visual + some planet imaging. I think I will skip the latest update as it seems to cause problems and is hard to install.

#114 Hilmi

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Posted 01 March 2013 - 03:09 AM

What problems? I installed the latest update and it went without any trouble at all. It adds a nice emergency stop button and so far it "seems" to have removed the guiding bug.

Its not difficult to install it just needs manual installation as compared to automatic install.

The difficulties I am facing are mechanical

#115 neilson

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Posted 01 March 2013 - 08:47 AM

Hi Hilmi,
I set my TVC backlash on my Gemini to 30 and it made a noticable difference on my mount. I ended up lowering it to 25. But your right, each repair has me thinking its the last one then something else goes wrong. Its been frustrating but at least I have been able to get them fixed. If something needs replacing Scott sends you the part. Meade or Celestron would never do that.

But for the money I paid I did expect the mount to perform much better right out of the box.

neilson

#116 orlyandico

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Posted 01 March 2013 - 09:10 AM

Here's an interesting one... Maxim backlash compensation doesn't wait.. it applies a fixed pulse movement whenever reversing direction to take up the slack. Say your mount has 2 seconds worth of backlash (at guide speed). This means that if dec guiding ever has to reverse direction, Maxim will apply a 2-second pulse to reverse.

the problem with this scheme is, if your mount has a lot of backlash.. say it has 20" of backlash (which is not uncommon). at 1X guide speed it would take 20 freakin' seconds to reverse direction in declination...

My Littlefoot controller (and the Gemini 2 as described above) have a different method: when reversing direction, a fixed number of pulses are sent, but at a much higher speed than the guide speed (for the Littlefoot it is at 40X sidereal - this is called the backlash speed).

That way, dec reversals are supposedly "instantaneous."

In my experience this doesn't work, but the problem on my AP600 mount is stiction. Even after applying 30-40 pulses to reverse direction, the mount doesn't move. Or if it does, it over-shoots.

(another OT) i got the AP600 for $2K (same price as a new G11 non-Gemini!) because I thought, it's an AP, it has to be great... well the periodic error is great, but it had (and has) a lot of problems in declination as described above.

the AP 9000QMD controller has a backlash adjustment, but it wasn't working for me. so I read up on the Littlefoot controller and thought, I'll add GoTo to this thing and fix my declination problems at the same time! (with the fast backlash speed feature).

well it didn't work. the Littlefoot controller was almost $1K (at least it didn't cost as much as a Gemini 2). so i was in the same situation.. throwing money in trying to fix the mount. eventually i gave up.

then I thought about getting a G11.......... because i thought, with the Ovision worm and all, I can get AP level performance. I wouldn't even need a Gemini 2, because I could retrofit the Littlefoot to a G11.

fortunately i resisted that temptation. :tonofbricks:

#117 Hilmi

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Posted 01 March 2013 - 11:28 AM

I have just gone through some balancing acrobatics today and I am now testing the entire setup again. It seems to all work, but unfortunately to get this to balance, I had to keep the camera at an orientation which does not result in a pleasing image. So now I am thinking maybe the camera needs some kind of counter weight system so that it never affects balance regardless of orientation.

#118 SMigol

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Posted 01 March 2013 - 02:01 PM

FWIW, my g11 has the dec backlash issue, too. What I've done is bumped my DEC guide rate to .5x vs .2 by using the Gemini web page. This is the only place where you can set different guide rates for the axes. It helps significantly. I also use Maxim's stiction control set at the maximum (9x) and set the dec aggressiveness to not overshoot. Thus, it will bump along, slowly adjusting DEC depending on what the drift suggests. Rarely it will overshoot and then it will try to get back. The slightly higher rate does help. Mostly the higher rate just breaks the stiction to keep things moving.

Note that I had to use this function when the weather got colder. I fully expect to turn this off once temperatures return to their temperate norms.

#119 orlyandico

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Posted 01 March 2013 - 02:10 PM

SMigol, i also used the same technique on my AP600. anti-stiction for the win. I used 0.3X in RA and 1.0X in DEC (on the Littlefoot). Results were still.. not exemplary.

The Mach1 made all these issues go away hard.






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