Re: Comet Hyakutake

[Joel.Alpers@xxxxxxxxxxx]

John R writes:

#It's interesting that the apparent motion of the comet across the star
#field is roughly perpendicular to the direction of the tail - good for "3D"
#(since the camera should be positioned so that the apparent motion of the
#comet is side to side).

Yes, that is interesting. I noticed that on my overlays. 

#Joel - did you use any kind of tracking to compensate for the "rotation"
#of the star field near the pole? Also, in your previous post on film
#speed, exposure time, etc., what was the f-ratio?

tracking: No, I don't own a telescope with an equatorial drive :(
I _did_ build a barn door yesterday, but found it useless as it didn't
have enough "freedom" on camera direction once properly set up. Live
and learn - I'll need to buy a ball head and bolt it on. Won't make
it for this comet, perhaps for Hale-Bopp...
Do you mean f/stop?  I'm working in the 2 - 4 range, depending on
the lens used.


#A brief comment in a newspaper - that the entire comet, including the 
#head and the huge tail sweeping 20-30 degrees across the sky, would give 
#off about as much light (as seen from Earth) as a bright star 

Excellent point, one that I was _trying_ to make in another posting,
but didn't say this clearly. The tail is _faint_, and the more light-
polluted your viewing site, the less of it you'll see.

The 1/4 moon was up at 9:30 when we arrived at the first dark site. 
The comet was unimpressive, with most of the tail washed out by moonlight.
An amateur astronomy friend looked up "moonset", and we went home, 
grabbed a couple hours of Z's, and got up at midnight, for another
trip to a dark site, without the moon's interference.

The tail spanned about 45-50 degrees!!!!

The comet moved fairly significantly during the hour, so much so that
I think my intended "stereo pairs", taken at the beginning and end of 
the hour, will have _much_ too much divergence. Hopefully there will
be some "accidental" pairs in the shots taken in between which will
work.  The comet is simply moving that much faster than several nights 
ago. (I haven't seen the film yet, as we got back after 3:00 am - 
so sue me! ;)

Tonight may well be the last good viewing night, as "moonset" is
getting much later every night.

Joel.


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