US ASTRONOMY
sxinias : Today, 12:23 PM from Sxinias Marathon Greece
Mandii,
Congratulations on getting your 6 inch telescope in operation. You are doing some good work without sophisicated equipment. Have you had the opportunity to accurately polar align your mount?
Joe
MANDII : Today, 02:56 PM
Dear JOE ,
The day of 5th Feb , I setup this scope .
On the same night , I did polar alighment by Drifting method , and took the picture of M50 & NGC3242 .
Polar alighment is always important . In my situation , it helps me to find the object efficiently ,accuratly ,and helps to track the object during the imaging process . To explain this two points indepth , it can be too much to say .
For this time , I want to say something about how I do the polar aligment , find the object , and track the object into pictures . It's my first time to explain this in this forunm , in English .
I did the drifting not by naked eye with eyepieces .It's done on a computer screen by inserting the camera(DSI-I) . The EQ3 mount is turned the polar at the same time when I look at the star moving-discrepancy from the screen . The more exposure time taken in a single flame , the more discrepancy( star tails) we can see from the screen . And then adjust(polar align ) the mount to reduce the discrepancy .
2ndly , if the mount is not aligned well , I can't find the DSO objects properly .
Actually , I am not free-finding the objects , like the star-hooking inside the eyepiece .
Becasue star-hooking is difficlut in my case , there is not much stars in the View finder. The FOV in an eyepiece(25mm eyepiece ) is so small( less than 1 degree) , and the star positions is always rotated to some degrees in a Newtonian scope , it's not fully inverted as the normal refractors do . So you cannot easily recognise those stars in a mean time , when you are looking at the the star-chat at the same timming. In summary speaking , It's very hard to find the object .
Indeed , I was usually using the numeric calibration ( RA and DEC scales ) on the mount . I turns the RA axis according to the time angle of an object ,meaning the RA value the object is located at the time it is observed . Let say this moment the object is located at time-angle 22h10m , the next hour it will move to position 23h10m . The time angle is very looks like to the RA value of an object , but it's changing with time and RA is fixed . After the mount's RA axis is rotated well , I turns the DEC axis to the DEC value of that object , this is traight forward because the DEC of an object is always fixed whenever any time is concerned .
THE ABOVE METHOD TO FIND AN OBJECT , I PERSONALLY CALLED THE " MANUAL GOTO" , it's similar to electronic GOTO , but using your own hand . If the mount is not aligned well, I can't see the objects within the FOV . This time , I can see the M50 and NGC3242 within the eyepiece FOV , by just one time turning of the RA and DEC aixs . It's located not really at centre , but within the area of the FOV .
3rdly , the polar alignment is aimed to star tracking in imaging .
My tracking this time was 1 minute single exposure , for total 10-20 minutes .
BR
MANDII |
显身卡
