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Visual Observing and Recal

Emilio J. Robau, P.E.
 

Roland,

I really appreciate the time you have taken to write this answer.   I was embarrassed to ask the question, but figured some of the users could help, and they did help.   I now know what to do now.   All I can say is that I wish I would not have gotten so caught up in imaging to delay the enjoyment of looking through a scope for so long.  I have had a wonderful time over the past couple of nights looking at old familiar targets such as the moon, Jupiter, and Mars.  I only wish that Saturn wasn't so low in the sky but time will cure that.

Thanks again for stooping down to help a lost visual observer.
Roland Christen
 

When you do a slew, you send the object co-ordinates to the mount. The mount now has the object co-ordinates in memory so it knows where it is in the sky. You can then move the axes to center the object, either manually via the clutches or electronically via the push buttons. In either case the  co-ordinates are in the mount and all you have to do in this case is to do a recal. This will match the entered co-ordinates to the actual position of the axes.

Sync is a special situation that occurs if there are no co-ordinates in the mount. For example, you power up the mount, release the clutches and move the scope manually to and object. The mount has no idea where it is because no object co-ordinates were entered. In  this case you bring up the object's co-ordinates in your planetarium app and Sync on them.

There is a danger in syncing on an object which might be past the meridian (counterweights up slightly). In that case all subsequent slews to other objects will occur with counterweight up and scope underneath the mount. That's one reason we discourage using sync. There are plenty of other ways to mess up such as syncing on the wrong object, which will definitely get the mount lost. Best to use GoTo to slew the mount to the object, center it with whatever method you like, and do a recal. Let the mount do the thinking.

Rolando

-----Original Message-----
From: Emilio J. Robau, P.E. <ejr@...>
To: main@ap-gto.groups.io
Sent: Sun, Jan 8, 2023 6:47 pm
Subject: [ap-gto] Visual Observing and Recal

I am having an issue visual observing with my new scope.    I am totally inept at such a simple thing;visual observing.   I am so used to imaging I am lost in space on how to replace platesolving.

Here is my situation.  I issue the slew command.   The scope goes to the object, but it is not centered.  In fact it is off the field of view.  This is the first slew of the evening and I moved the scope prior to start up, but tell the scope it is in park 3 when I unpark it.  I slew to the first target.  It is not in the field of view.  I manually move the scope to the object.  The object is now in the field of view.  Should I be doing a sync or a recal or neither.   I am thinking recal.  I am sure someone can answer this.
Thanks in advance for any answer.



--
Roland Christen
Astro-Physics
Mike Dodd
 

On 1/8/2023 7:56 PM, Christopher Erickson wrote:

Basically, always use Recal.
Agreed.

Do you have a finder scope? I've found it helpful to use the arrow keys
to center the target (a very bright star) in the finder first, then in
the OTA with a long FL eyepiece. If I want to be precise, I'll replace
that with a short eyepiece that has crosshairs. I use the hand box arrow
keys with the slew rate set at 12X.

Using the finder scope first eliminates blindly searching for the star
in the main scope. I always adjust my finder scope so its crosshairs
match the center of the main OTA, and I note which direction each arrow
key moves the star in the finder scope.

This is the first slew of the evening and I moved the scope prior to
start up, but tell the scope it is in park 3 when I unpark it.
Is the mount actually _in_ that position? If you put a level on each axis, are they level? Can you adjust the tripod or whatever the mount sits on so the axes are level? If so, then your first slew should put the target close to the center of the FOV. The only reason it's off is because the mount is not physically exactly in Park 3.

HTH.

--- Mike
Christopher Erickson
 

Recall and sync are almost exactly the same thing. Except sync will confuse your servo controller if your counterweights are above your OTA. Basically, always use Recal.

Further, depending on your servo controller and hand controller firmware versions, ortho error will effect your goto accuracy when crossing the meridian.

-Christopher Erickson
Observatory engineer
Waikoloa, HI 96738
www.summitkinetics.com
   


On Sun, Jan 8, 2023, 2:47 PM Emilio J. Robau, P.E. <ejr@...> wrote:

I am having an issue visual observing with my new scope.    I am totally inept at such a simple thing;visual observing.   I am so used to imaging I am lost in space on how to replace platesolving.

Here is my situation.  I issue the slew command.   The scope goes to the object, but it is not centered.  In fact it is off the field of view.  This is the first slew of the evening and I moved the scope prior to start up, but tell the scope it is in park 3 when I unpark it.  I slew to the first target.  It is not in the field of view.  I manually move the scope to the object.  The object is now in the field of view.  Should I be doing a sync or a recal or neither.   I am thinking recal.  I am sure someone can answer this.

Thanks in advance for any answer.
Emilio J. Robau, P.E.
 

I am having an issue visual observing with my new scope.    I am totally inept at such a simple thing;visual observing.   I am so used to imaging I am lost in space on how to replace platesolving.

Here is my situation.  I issue the slew command.   The scope goes to the object, but it is not centered.  In fact it is off the field of view.  This is the first slew of the evening and I moved the scope prior to start up, but tell the scope it is in park 3 when I unpark it.  I slew to the first target.  It is not in the field of view.  I manually move the scope to the object.  The object is now in the field of view.  Should I be doing a sync or a recal or neither.   I am thinking recal.  I am sure someone can answer this.

Thanks in advance for any answer.

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