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The Pup- Fantastic seeing

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#1 Rutilus

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Posted 03 January 2013 - 04:22 PM

With Sirius only getting to around +19 degrees altitude from my site, it takes a night of really good
seeing to go after the Pup.
For the past two days it has very mild here at around +12C, and last night with my Carton 100mm f/13 Achromat
I was taken by how easy it was to see stars E and F in the Trapezium.
Moving down to Rigel, I got a quite wonderful view with the star presenting a very stable image.

So this was definitely the night to go Pup hunting. Using a 12.5mm Baader Genuine Orthoscopic
eyepiece (104x) Sirius gave a stunning view, never before had I seen the image so stable.
With the Carton lens, Sirius was pure brilliant white, with just the very tiniest flash of blue C.A.
visible. I picked the Pup up within about 10 seconds of getting Sirius into the eyepiece, there it was,
no if's no but's, not just glimpsed now and again, but a constant steady faint dot.

What a fantastic view, I spent the next hour just taking in the view, this type of seeing
so low down is exceedingly rare for me from this location.

I tried several different filters to see which if any gave an advantage.

1. No-Filter. The Pup was seen very well in spite of the brilliance of Sirius.
2. Baader Semi-APO. The only difference I could see over the non-filtered view was
a slight dimming of the over-all view. Still the companion star was still easy to see.
3. Baader Contrast Booster. This filter did make a difference, it completely removed
the bluish tint of C.A. from the eyepiece view. There was a very slight colour cast,
with Sirius now appearing a slightly dirty white. However it provided the best views
of the companion.
4. Yellow and Green filters. The companion was still visible when using these filters,
a bit harder with the green filter.

So on the night, the Contrast Booster filter work very well indeed, and on nights of average seeing
I think this will be the one I use when Pup hunting.

#2 Kon Dealer

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Posted 03 January 2013 - 05:55 PM

Isn't the Baader semi-APO a combination of the Contrast Booster and Fringe Killer?
If so I'm puzzled why it didn't perform similarly?

#3 Rutilus

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Posted 04 January 2013 - 02:23 PM

Kon, interesting what you say regarding the Semi-Apo.
I have now tried this filter on half a dozen achromats,and all it does is dim the image slightly compared to the un-filtered view.
Any C.A. visible remains the same in the all the scopes I tried it on. With the filter there is no colour cast, unlike the Contrast Booster
which gives a slightly pale yellow tint. On all the scopes I tried the Contrast Booster completely removes any trace of C.A.

On my refractors, the Semi-apo has been a complete waste of time. However, when used with my C9.25 SCT it is a superb Mars filter.

Last night I viewed Sirius again but in just average seeing conditions, the Pup was much harder, this time only visible
in moments lasting 3-5 seconds at most.






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