Telescope Reviews: A few Dawes Doubles

A few close doubles with similar magnitudes (near 6) for exploring
Dawes limit:


 Name     RA    Dec     Mag1  Mag2   Sep   PA   Con  Star
 STF  61: 00499 +2743   6.33  6.34   4.30  296  PSC  65 PSC
*STF  73: 00550 +2338   6.12  6.54   0.95  314  AND  36 AND
 STF 333: 02592 +2120   5.17  5.57   1.40  209  ARI  EPSILON ARI
 KUI  15: 03520 +0632   6.26  6.56   0.70  208  TAU  31 TAU
 STF2583: 19487 +1149   6.34  6.75   1.40  107  AQL  PI AQL
 STT 395: 20020 +2456   5.83  6.19   0.80  123  VUL  16 VUL
*SHJ 345: 22266 -1645   6.29  6.39   1.55   14  AQR  53 AQR
*BU  720: 23340 +3120   5.67  6.11   0.53   98  PEG  72 PEG

Data is from WDS; entries marked with an asterisk have known orbital
data and the Sep and PA for these was gleaned from an ancillary WDS
ephemerides file with Sep and PA projected for 2003-2007 (obviously,
I used the 2003 projections).

I only looked at five on the list last night with my 8" dob, seeing was
reasonable but not great:


65 PSC: Easy to find and easy to split, and right on the way to the next
        one:
36 AND: Figure eightish: At 200x it was detectably notched, and at 400x I
        could see (for fleeting moments) two distinct but somewhat
        overlapping spurious/airy disks (borrowing terminology from EdZ's
        Raleigh Limit post).
Ep ARI: Relatively easy at 200x
PI AQL: Same separation and same magnitude difference as Ep ARI, but over
        a magnitude fainter: definitely found this one the harder of the
        two.
72 PEG: This one is beyond the theoretical Dawes limit for my 8", but I
        tried hard anyway. Couldn't scratch it, let alone put a notch in
        it. Seeing wasn't really good enough to see if there was any
        detectable elongation.

I would have tried for 31 TAU later, but I got side tracked by Saturn (which
was *very* nice once it gained a little altitude) and viewed no more doubles.
I think 31 TAU will be at or past the practical limits of my 8". I tried Zeta
Boo in the spring/summer, which is listed as 0.74 separation for 2003. I was
able to discern something between a notch and a peanut at 400x and my
guesstimate of PA was in the ball park of the reported figure (but that was
once, briefly, out of 6 or so different attempts).

Tonight is predicted to have better seeing, so I may well try for 31 TAU, but
I suspect that'll be the end of my Dawes experimentation --- I've learned two
things: 1) I think my scope performs acceptably in terms of close doubles, and
2) I derive much more enjoyment from more comfortably separated doubles with
interesting color (almach, albireo), or magnitude (rigel) contrasts

andrew

--------------------
4.5" orbitor dob
8" skywatcher dob
Larrivee 6-string (oops, wrong instrument)

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