Re: (IAAC) Obj: Alpha sco/ M4 - Inst: 4" Off Axis Dobsonian f10


Some thought on splitting Antares:

You list your scope as a 4" off axis. I assume you are using an 
off-axis mask to eliminate the diffraction spikes. But you are losing 
resolution if you do. Try a hex-mask. Cut a piece of cardboard or the 
like to a circle big enough to cover the open end of your tube, and cut 
out the largest practical hexagon within. What this does is 
re-distribute the light from the diffraction rings into six spikes. I 
have found that the companion lies on the first ring and tends to be 
hidden by it. Rotating the mask will move the position of the spikes, 
hopefully until the companion lies between two of the spikes.

Another technique some people have found useful is using filters to cut 
down on the glare of the primary. Some people have reported luck using 
an OIII filter; I personally have used an Orion UltraBlock filter with 
some success. Apparently, the sceptroscopic differences of the two 
stars help here, as the companion apparently has more in the bandpass 
of the filter and thus is less affected by it.

Also, some people report better luck splitting this during twilight, 
when the brighter ambient light reduces the primary's glare.

William Schart

On Monday, May 26, 2003, at 04:07  AM, Apache User wrote:

> ----
> Observation Poster: Shane Sweeney <shane_sweeney@hotmail.com>
> Observer: Shane Sweeney
> Your skills: Intermediate (some years)
> Date/time of observation: 05/25/2003 0600UT
> Location of site: Tahlequah, OK, USA (Lat 35 9', Elev 250M)
> Site classification: Rural
> Sky darkness: 8 <1-10 Scale (10 best)>
> Seeing: 7 <1-10 Seeing Scale (10 best)>
> Moon presence: None - moon not in sky
> Instrument: 4" Off Axis Dobsonian f10
> Magnification: 79,125,255
> Filter(s): None
> Object(s): Alpha sco/ M4
> Category: Multiple star.
> Class:
> Constellation: Sco
> Data: mag   size
> Position: RA :  DEC :
> Description:
> I have yet to split Antares!! I thought I had something but couldn't 
> tell at 255x a little dot now and agian. I have a little bit of dust 
> on my primary and at 255x I get little arcs around the airy disc out 
> to about 3" on really bright stars. M4 looked agreat at 29x and was 
> very mottled at 79x, many stars resolved all across ellipse at 129x 
> with averted vision. 255x was very dark and started to look like a 
> very very tight open cluster with a bit of background haze.
> --
> Optional related URLs:
> ** This observing log automatically submitted via the Web from:
>   http://www.visualdeepsky.org/enter-log.html
> To stop receiving all 'netastrocatalog' lists, use the Web forms at:
> http://www.visualdeepsky.org/subscribe.html

To stop receiving all 'netastrocatalog' lists, use the Web form at: