Re: [APML] OT: St-4 -help!

[Éder Iván <eder@prof.hu>]

Radek,

Thanks for the tips.
Yes, I know the problems coming from the gearbox. I'm planning to buy a 
SkyScan upgrade, but still I'm waiting for an upgradeable (via internet) 
version.
I absolutely know how my mount works, since I guide it manually for 2 
years. It has the same rough (and big +/-20") periodic error, and huge 
backlash (about 1.7 sec). I tried to set backlash (H2 parameter) to 
different values, but the problem does not disappeared. While st-4 worked, 
I simultaneously watched the guide star through the main optics, so there 
were no backlash overcompensating, or similar setting problem. The st-4 
every time (after direction changing) applied the increased time to the 
second corrections also, I don't know why.
Maybe the SkyScan upgrade will solve the problem, and i will not need 
backlash compensation anymore.

Thanks again,
Ivan

At 01:12 2005. 09. 19.t Conve, you wrote:
>
>Hi Ivan,
>
>no, theres is no need for photo.
>
>First of all I have to say that I dont have ST-4 so I cannot help you with 
>setup, but I have old type of EQ-6 mount, I did some modification and Im 
>using it successfully now (you could see some of my pictures).
>
>
>My experience with old type of EQ-6 mount is that motors are very weak so 
>it has to be gearbox inside with couple of tooth-wheels which cause two 
>main problems:
>
>- huge backslash
>
>- periodic error which si quite big (mine has about 40", but its not main 
>problem) and mainly very rough (did you do some measurement of periodic 
>error ?) because of quality of tooth-wheels used in gearbox
>
>
>So I decided to do some modification, first of all I disassembled mount 
>completely and cleaned it from old grease and oiled it with new. Then I 
>knew I  had to do something with gearbox, because it caused a lot of 
>problems. But at that time was no Skyscan on the market, so friend of mine 
>bought suitable powerful stepper motors and made for me tooth-wheels which 
>I needed. Basically it looked pretty same as Skyscan but without 
>electronics. I did not need new electronics because I bought new one in 
>the time I bought my mount, because I wanted to have autoguider input. So 
>I bought Powerflex MTS-3SDI, which has autoguider input, PEC, backslash 
>compensation, microstep, it enables change frequency of the stepper motors 
>etc. After changing of motors and gears (I had also to reprogram my 
>electronics, which was quite easy) periodic error changed a lot. Size 
>stays the same but its very smooth now so autoguider can handle it.
>
>  Other thing which changed was backslash. Before modification I had to 
> use backslash compensation with autoguider. But it was problem with it. 
> Size of backslash was changing a little bit with position of worm, so I 
> had to control it before every exposure and change settings of backslash 
> compensation when needed (It might be also your problem, it might be 
> overcompensated, which is worse than small amount of dead travel). But 
> after modification there is no backslash at all, so I dont have to use 
> backslash compensation.
>
>  So my recomendation for you is to buy Skyscan and change motors and 
> gears it will help you a lot. Backslash will be minimal, periodic error 
> will be smoth (I dont say it will be small, but its not so important) and 
> motors wll be more powerful. In adition you will have Goto (which is 
> great for searching of dim objects) and PEC. I have PEC in my electronics 
> but cannot use it because error of my mount is still not periodic.
>
>
>Maybe it will help a little bit
>Radek
>
>
>--------------------------------------------------------------------------------------------------------------
>
>I have the old type, I made an autoguider input into the hand controller.
>Not complicate, 5 cables, 4 for the 4 directions, 1 for the ground. If you
>need more info i will send photos later.
>
>Ivan
>
>At 22:40 2005. 09. 18.t Conve, you wrote:
> >Hi Ivan,
> >
> >what type of EQ-6 do you have ? New Skyscan version with autoguider input
> >or plain ? When plain, how do you connect ST-4 to it ?
> >
> >Radek
> >
> >
> >
>
> >Hi Guys!
> >
> >Several weeks ago I had purchased a brandnew(!) st-4 autoguider. I'm in the
> >learning phase still, but I have an uncovered problem with the camera.
> >
> >There is a problem with the backlash compensation, which seems to works not
> >properly.
> >The problem is: when st-4 change the direction in Dec, it applies the
> >increased correction time (due to H2 setting) TWICE, resulting a completely
> >false correction.
> >
> >Does anybody has any idea what might be the problem?
> >
> >Thanks:
> >Ivan
>
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