Quote:
Originally Posted by White Rabbit
do you think I would get any benifit from it with my HEQ5 pro mount. I intend on upgrading at some point (arnt we all?) so it may be worth bying it now whilst the AU is flying high even if I dont use now.
Thanks for the help guys.
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Hi Sandy,
In a previous post you wrote -
Quote:
What I find a pain in butt is when I slew to something it will be in the FOV but not centred. I always have to take an image then recentre, take another image and so on and so on. It all takes to much time and I only have a few hours at night most nights.
It's especially a pain when you go past the meridian and I have to flip the mount. ATM when I go past the meridian, I select another target because of the huge deal of framing the picture the same way it was.
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Based on this description, it is likely you probably have Dec to optical axis
non-perpendicularity, what is known as Collimation in Hour Angle or CH for short.
It can come about for a variety of reasons, such as an OTA not being "square"
on a dovetail or "square" in a set of rings, or in turn the dovetail or rings not being
"square" to the head of the mount. It can also occur if the OTA is not collimated
or if you are using a camera in an eyepiece holder, if the camera's optical axis
is not collimated with respect the light exit path from the eyepiece holder.
For example, if the camera is heavy and held in a holder by a thumbscrew,
it might shift under the weight of gravity.
If the error is random, such as a mirror flop in an SCT or a sudden shift in a
camera with respect the eyepiece holder or if the scope is now and then
rotated in a set of rings, it can be more difficult to cure and certainly pointing
analysis in that case won't be able to compensate for it, but it would tell
you that in fact you have a random error.
If the error is of a systematic nature, it lends itself perfectly to pointing analysis
and correction.
Apart from CH, there are other phenomena that could give rise to it, such as
Dec to RA non-perpendicularity, or NP for short, but since you mention it is a
commercial GEM, NP is a less likely candidate than CH. With either CH or NP,
as you flip the mount, the direction of the error will reverse. CH is constant for
for all values of Dec whereas NP will be at a minimum at Dec=0 on the scope
and a max value at the pole of the scope.
There will undoubtedly several other sources of error, though probably not
as pronounced as your likely CH term, that TPOINT would uncover and
mop up for you. As a bonus, it will tell you your polar misalignment as well.
Whether it is worthwhile for you, that will have to be for you to decide, depending
upon how serious a problem it is for you.
TPOINT can be purchased 'standalone' from Software Bisque -
http://www.bisque.com/sc/shops/store...t-win-box.aspx
though they assume nearly all users will be using it in conjunction with
TheSky.
Keep in mind that if you are using it standalone, you will
need some way to log the sampled stars cataloged RA/Dec, where your
scope "thinks" it is pointing in RA/Dec and the current sidereal time.
These are the tasks that using TPOINT in conjunction with TheSky will
automate for you, otherwise you will have to script something yourself.
Good luck!
Best Regards
Gary
