My TAL-2M telescope is a PushTo instead of a GoTo, so I have to find the objects manually.
I do this by using the Setting Circles of my scope.
Sometimes this takes quite a while and I am always happy when I (finally) have the object of my choice nicely centred in my eyepiece.
But now the real problem starts: I have to replace the eyepiece with home made parfocal adapter with my camera.
I have to do that VERY carefully because when the OTA is only moved a little bit (in RA of course, the DEC is locked) then I do not see the wanted object on my screen and I have to guess in what direction the OTA should be adjusted and also how much.
And with dim objects I have to wait until the required exposure time has been completed and I get the refreshed preview image on my screen. Usually I have no other option than replacing the camera with the eyepiece, re-find the object, and replace again.
The main problem is that on my scope the RA setting circle is rather crude and hard to see and thus not much help for this kind of precise OTA adjustment. And because of the local light pollution and the dimness of the object the nice 8x50 finder of my scope is useless, alas.
The whole procedure takes a lot of time and sometimes I think that it is a miracle that I can make any images at all ....
I have been thinking to buy Digital Setting Circles (DSC) for my scope, but those things are expensive.
Also: all I wanted to know - after installing the camera - in what direction and how much to shift in RA, so a simple digital readout would be enough.
Then I got an idea and I mounted a spare Vesta webcam with it's original lens on a bracket in such a way, that it looks down at the RA setting circle and can be used as an RA monitor.
|This is what the RA setting circle looks like when viewed by the RA webcam.|
First I tested in the daylight:
On my laptop I ran two instances of K3CCDTools: one with a Vesta and 2x135mm SLR Photolens aimed at the chimney of my home and the other instance looking at the RA setting circle: the RA monitor.
When the SLR Photolens instance was properly aimed I manually adjusted the RA circle of my mount so that the arrow was nicely aligned with one of the engraved lines of the circle: easy for me to remember. I verified that this was clearly visible on the screen.
Then I hid the window with the 'imaging' camera and swung the OTA around.
I repositioned by using the RA monitor webcam and carefully positioned at the RA value I had remembered.
I reopened the 'image' window: BINGO! The chimney was exactly there where I wanted it to be!
Two instances of K3CCDTools: one as 'imaging' window and the other as RA monitor window.
The chimney was right in the centre of the screen after blind repositioning by using the RA monitor window.
The same night - it was clear ! - I tested 'under the stars': it went like a dream.
I could easily 'blind' refind my target and also targeting at a new object went smoother than ever, because the RA pointing is now far more accurate because of the superior visibility of the RA scale on the RA monitor window.
Note: my RA setting circle is illuminated by a small 12V lamp, which is more than enough for the Vesta RA monitor cam to get a clear picture on the screen.
Note 2: I stopped using the above method in July 2005 as the 2nd instance of K3CCDTools is now being used for autoguiding :o)
To improve my view of the setting circles I now use a simple magnifying glass, which also works fine.