Re: PASILL4 on Mach1, update


Pierre Henrotay
 

Hi Samir,

thank you for the tip, looks like a good idea.

I just did so, but not using TheSky which I do not have:
- in SkyMap Pro, I made a map of the area next to the North Pole
(about 15 degrees wide) and saved it as bitmap
- I took a photo in daytime thru the polar scope against a white
background; easy with my digicam
- I used MaxIm to align the map and the photo (plain translate,
rotate and scale) using 2 stars as alignment: Polaris and delta UMi
- added both images with 50% intensity each

The result is that OV Cep ends up at the right place as well.
The conclusion is that the reticle is fine. BTW, I rechecked that it
is centered by taking 4 pics thru the polar scope, with a distant
object as target, each pic differing from previous by 90 deg: all
fine, centering is OK.

I must be doing something wrong when using the polar scope itself,
but yet wonder what. Especially since for the last test, we were two
guys to crosscheck what we were doing.

Need further clear nights to retest... unfortunately no clear skies
forecast for the next days/weeks.

So the status so far: operator error ?

Pierre
--- In ap-gto@..., "Samir Kharusi" <samirkharusi@...>
wrote:

At least from what you have drawn, the indication is that the
magnification is correct. It is thus fairly simple to verify that
the
reticle is correctly engraved or not. Take a photograph, daytime
against a clear sky or a white sheet of paper, through the polar
scope. Just try various lenses on a digicam or dslr holding the
lens
against the eyepiece. Something always works well enough. Match up
your photo, ie using Image Link, with The Sky. My old version of
The
Sky did not show the location of the North Celestial Pole, but I
added it in as a user point. Be careful that you put it in for
2008!
The error in the sketch does seem to be too large to be blamable on
atmospheric refraction, IMHO, and if it is indeed in error,
Losmandy
should be able to produce corrected reticles fairly quickly.

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