Re: [ap-gto] Re: 2 dumb questions - slew limits and pec


Jun 29, 2005

 


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#13104 Jun 29, 2005

I'm using a 1200 and have a couple of beginner questions:



1 - I assume that I can still image past the meridian if I set

slew limits in the hand controller and the settings only limits the

motion towards the zenith - correct? I generally control the scope

through The Sky and understand that the software controls the limits

there but if a slew in intiated through the control box (while

actively connected to The Sky) I assume that the limits in the hand

controller govern.



2 - I plan to train the PEC using the settings in the hand control

box. I assume a good way to do so is by using the error corrections

of my autoguider? I assume that this records only one worm cycle

and there is no point in multiple runs? Finally I assume that it's

fine to autoguide during the playback of the PEC correction later?



I know the danger of assumptions so thanks in advance.



Bill Patterson

www.laastro.com



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#13105 Jun 29, 2005

Hi Bill,



First, let's differentiate between "slewing" and "tracking." Slewing

is when you're moving the scope to different coordinates via

something (handbox or software such as TheSky). Tracking is when the

RA axis is moving to match the movement of the stars. An AP mount

will happily track right through the meridian while imaging. It will

only flip if you send some coordinates to the mount and it determines

it needs to flip - e.g. the target coordinates are on the other side

of the meridian.



Regarding PEM, you can program it manually or with an autoguider.

Both only use 1 worm cycle. If you use an autoguider, be careful to

have your guiding settings such that they don't chase the seeing.

Alternately, check out PEMPro. It has the ability to average more

than one worm cycle (effectively averaging out the seeing) and you

can manipulate the resultant curve before training the mount. You

can (and I believe should) turn on PEM for the best autoguiding.

Having said that, with AP mounts and their low, smooth PE, it really

doesn't matter much either way, unless you're doing unguided images.



I hope this helps.



Jim McMillan

--- In ap-gto@yahoogroups.com, "BillyPatt" bill@l...> wrote:

> I'm using a 1200 and have a couple of beginner questions:

>

> 1 - I assume that I can still image past the meridian if I set

> slew limits in the hand controller and the settings only limits the

> motion towards the zenith - correct? I generally control the scope

> through The Sky and understand that the software controls the

limits

> there but if a slew in intiated through the control box (while

> actively connected to The Sky) I assume that the limits in the hand

> controller govern.

>

> 2 - I plan to train the PEC using the settings in the hand

control

> box. I assume a good way to do so is by using the error

corrections

> of my autoguider? I assume that this records only one worm cycle

> and there is no point in multiple runs? Finally I assume that it's

> fine to autoguide during the playback of the PEC correction later?

>

> I know the danger of assumptions so thanks in advance.

>

> Bill Patterson

> www.laastro.com



----------------------------

#13106 Jun 29, 2005

In a message dated 6/29/2005 1:48:56 PM Central Daylight Time,

bill@... writes:



> 1 - I assume that I can still image past the meridian if I set

> slew limits in the hand controller and the settings only limits the

> motion towards the zenith - correct? I generally control the scope

> through The Sky and understand that the software controls the limits

> there but if a slew in intiated through the control box (while

> actively connected to The Sky) I assume that the limits in the hand

> controller govern.





NO, the keypad (hand controller) is a stand alone item. The Sky is a stand

alone item. If you slew with The Sky, then all applicable software controls

built into The Sky will govern the motion of the mount. The keypad is out of the

picture at that point. The Sky controls the mount servo directly - that is the

item to which it is connected. It is not connected in any way to the keypad,

so any settings in the keypad are not valid.

>

> 2 - I plan to train the PEC using the settings in the hand control

> box. I assume a good way to do so is by using the error corrections

> of my autoguider? I assume that this records only one worm cycle

> and there is no point in multiple runs? Finally I assume that it's

> fine to autoguide during the playback of the PEC correction later?

>



Yes, you can guide during playbeck. The guide signal always overrides the PEM

corrections. The PEM corrections are overwritten each time that you do

multiple records. You can smooth out and tweak the internal PEM corrections with an

external program on your computer - Ray Gralack's PemPro.



Roland Christen





[Non-text portions of this message have been removed]



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#13107 Jun 29, 2005

In a message dated 6/29/2005 2:43:48 PM Central Daylight Time,

chris1011@... writes:



> I generally control the scope

> > through The Sky and understand that the software controls the limits

> > there but if a slew in intiated through the control box (while

> > actively connected to The Sky) I assume that the limits in the hand

> > controller govern.

>

>

> NO, the keypad (hand controller) is a stand alone item. The Sky is a stand

> alone item. If you slew with The Sky, then all applicable software controls

> built into The Sky will govern the motion of the mount. The keypad is out of

> the

> picture at that point. The Sky controls the mount servo directly - that is

> the

> item to which it is connected. It is not connected in any way to the keypad,

>

> so any settings in the keypad are not valid.

>



Sorry, I did not read your question properly. Let me try again.



If you initiate a slew with the keypad (I assume that's what you meant by

controller/control box), then the settings inside the keypad will be valid, and

any slew limits will be observed. If you slew with Teh Sky, then any settings

inside the keypad will be ignored.



Roland Christen





[Non-text portions of this message have been removed]







----------------------------

#13108 Jun 29, 2005

Hi,



Roland's comment below is confusing me.



Let's say I want to slew to an object east of the meridian (to observe

it continously for a while) I will slew with 'The Sky'. So I use the

keypad and change the meridian flip to 1hr. I go back to 'The Sky' and

slew. I think I have done that before and the mount ended up with the

OTA on the east side and the scope pointing east of the meridian.

(sort of what I want and expected).



Does that contradict the wording below? I thought the meridian setting

from the keypad is obeyed when slewing from 'The Sky'. I am not aware

that 'The Sky' has meridian flip controls. (Please correct me if I'm

wrong)



Sorry about splitting hairs. ;-)



Gert

>

> Sorry, I did not read your question properly. Let me try again.

>

> If you initiate a slew with the keypad (I assume that's what you

meant by beypad is > controller/control box), then the settings inside the keypad will be

valid, and > any slew limits will be observed. If you slew with Teh Sky, then any

settings > inside the keypad will be ignored.

>

> Roland Christen

>

>

> [Non-text portions of this message have been removed]



----------------------------

#13109 Jun 29, 2005

In a message dated 6/29/2005 3:51:59 PM Central Daylight Time,

drgert1@... writes:



> Let's say I want to slew to an object east of the meridian (to observe

> it continously for a while) I will slew with 'The Sky'. So I use the

> keypad and change the meridian flip to 1hr. I go back to 'The Sky' and

> slew. I think I have done that before and the mount ended up with the

> OTA on the east side and the scope pointing east of the meridian.

> (sort of what I want and expected).

>



Yes, that is correct. The meridian delay is simply done by the keypad by

offsetting the time by 1 or more hours and this fake time is sent to the mount

servo. The keypad retains the correct time for parking and other calculation

purposes. So, when the mount servo is asked to go to a new RA/DEC position, it

looks at its internal clock, sees the new time and determines if the object is on

one side of the meridian line or the other, and then slews accordingly. An

RA/DEC number can be sent in any number of ways - by the keypad, by a

planetarium program, or by you typing in the RA/Dec number in Hyperterminal and sending

the info to the servo via the Com port.



In the case of a slew limit, we calculate in the keypad whether the RA/Dec

number is inside or outside the forbidden zone which you have set in the keypad.

If the number is inside this zone, the keypad simply refuses to send this

RA/Dec value to the servo, and tells you so.



Roland Christen





[Non-text portions of this message have been removed]



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