5mm reticule eyepiece?

[Gerhard]

Hi all,

I was just wondering... I've been looking for eyepieces to do drift alignment with, and as per this video:

http://www.andysshot...tAlignment.html

and after trying out with my own 5mm eyepiece (without reticle), I wanted a 5mm reticle eyepiece. 

But searching it turns out there are practically only 12,5mm illuminated reticle eyepieces...

The 5mm Orion seems to have been discontinued...

Anybody have any idea why this is? Did the 5mm cost too much? 

As I see it a 5 mm would do nicely, because one easily sees the direction a star goes, when turning off the motor drive, and I'm guessing it would also be better for detecting the drift. More so than with a 12,5mm...

Thanks for any ideas, thoughts!

Gerhard.

[ronin]

Likely a 5mm reticule eyepiece would mean you are contunually adjusting.

5mm on most scopes means a high(ish) magnification, that in turn means a narrow field and any object will therefore drive across the view quickly.

You are in effect trying to centre an object that is moving a bit too quickly to be defined as stable for any length.

Your Vixen is 750mm, that is 150x which in turn on a plossl means 1/3 degree view edge to edge so half that for centre to edge of the eyepiece not the reticule bit in the centre. So for careful setting the object is likely contunually moving out of the centre too quick.

So I guess it is a case of on a moving celestrial object that field is too small for the use of a reticule to be practical.

[Stu]

The OP has said he has tried a 5mm and it does what he requires.......

All I can suggest is using a Barlow to get the additional magnification and accuracy you require. A x2 will obviously get you close, and playing with spacing will get you to 5 I'm sure

[Gerhard]

Likely a 5mm reticule eyepiece would mean you are contunually adjusting.

5mm on most scopes means a high(ish) magnification, that in turn means a narrow field and any object will therefore drive across the view quickly.

You are in effect trying to centre an object that is moving a bit too quickly to be defined as stable for any length.

Your Vixen is 750mm, that is 150x which in turn on a plossl means 1/3 degree view edge to edge so half that for centre to edge of the eyepiece not the reticule bit in the centre. So for careful setting the object is likely contunually moving out of the centre too quick.

So I guess it is a case of on a moving celestrial object that field is too small for the use of a reticule to be practical.

As I understand the practice of drift alignment (only watched the video in the link I mentioned before), you need to center a star in the reticule, turn off the tracking, watch it drift West, and align the reticule that way.

Next, you "put" the star on one of the East-West reticule lines, with tracking on, and watch if it drifts north or south. If one is already aligned well, this should not happen, because the tracking compensates.

I tried this yesterday with my "normal" 5 mm EP, and found that when I turned off the tracking, the centered star went West not too quickly to vanish immediately from the fov, but quickly enough to detect the movement and follow it to align the hypothetical crosshairs.

Then afterwards I turned the tracking back on, and for a test I put the star practically on the edge of the fov, to see if it would disappear from the fov, or if it would come further into the fov, thus showing drift one way or the other.

I had polar aligned before doing this, and the star did not move at all... I'm not sure this is because I aligned perfectly (doubtful) or if the drift is too slow, and I did not wait long enough to see it (waited something like 5 mins).

Point being, I'm worried a 12,5 mm EP would have too LITTLE magnification to be useful, because it would show even less clearly possible drift movement, necessitating long waits to see drift.... Also aligning the crosshairs would take more time, because the westward movement would be less evident... I found the latter very convenient in the 5 mm EP...

[Gerhard]

I wrote to the astronomy club I'm a member of and maybe somebody has an EP I can buy off of him.

I'll try that (probably a 12,5 mm) and see if it works well for me. Afterwards I might decide to buy a barlow as well, as suggested.