Sunday, October 02, 2005

1st Night: '05 Fall Season

Tonight I arrived at TotL (northeast corner of the Great Lawn in Central Park) at 11:30p with Peter, Kin and Charlie already observing.

Nova hunting started at 11:55p and was interrupted by the lawn sprinklers going off at 12:05a. Around 12:30a the sprinklers ceased. Even with a light wind the mist drifted over our equipment. Lots of maneuvering to get optics onto dry ground. An officer in an SUV stopped by at 12:50a to remind us that the park was closing at 1:00a. Peter and I stayed with optics packed until nearly 2:30a observing and chatting. The officer never returned.

The sky was clear and my attention was on the northeast portion of the sky focusing on Auriga. A check of the naked eye limiting magnitude (NELM) from my apartment window on the Upper East Side was ~4.8. From the park I reached the same limit. Stars used for NELM were HIP 4151 (HD 5015) mag. 4.8 between γ Cas and κ Cas. Also seen was υ1 Cas mag 4.8 between γ Cas and η Cas (Achird). This is dimmer than υ2 Cas. Relating NELM to binocular's limiting magnitude (BLM) will be an ongoing project.

[image: b&w] NELM Cassiopeia mv 4.8 - 5.6

The optics used tonight were a pair of Fujinon 10x70's. They reached to at least magnitude 9.5. Something I need to resolve for this survey is how deeply should I search in order to cover as much ground as quickly as possible with a decent chance of finding a nova. Determining how much brighter than the BLM is the key. What I'll attempt to do next time out is to bin the stars seen in the 'bins' based on how difficult they are to see. I'm thinking of 5 groupings but will finalize this in the field:

1 - obvious even with sunglasses on
3 - dimmest star seen with no effort
5 - seen after searching for an extended period

I've decided for now to keep this binary and will work with 2 groups:

1 - star seen with no effort
2 - seen after searching for a short period

1-2 Oct 2005: Time spent nova hunting ~30 minutes from 11:55p-12:55a.

Dimmest stars seen in 2 asterisms (Double Peaked Triangle & One-armed Stickman) in SALC 53:

HD 280232 (v mag 9.5)
TYC 2894-1223-1 -- Star in double system

Sources: PtfP 9.53; Tycho-2 VTmag 9.593 (err 0.029); GSC-2.2 Bjmag 10.30 (err 0.04) / Vmag 9.59 (err 0.03); GSC Pmag 9.38 (err 0.40); SAO Pmag 10.0 / Vmag 8.9; AGK3 Pmag 10.0; HD Ptm 10.0; BD mag 9.0

HD 30896 (v mag 9.3)
TYC 2399-600-1 -- Star

Sources: PtfP 9.28; Tycho-2 VTmag 9.31 (err 0.028); GSC Pmag 9.26 (err 0.23); AGK3 Pmag 9.3; SAO Pmag 9.3 / Vmag 8.7; HD Ptm 9.00; BD mag 8.8

HD 277396 (v mag 9.3)
TYC 2899-1549-1 -- Star

Sources: PtfP 9.26; Tycho-2 VTmag 9.433 (err 0.021); GSC & GSC-ACT Pmag 8.76 (err 0.40); SAO Pmag 10.8 / Vmag 8.8; AGK3 Pmag 10.8; HD Mag 10.8; BD mag 9.0; 2MASS Bmag 10.91 / Rmag 9.26; GSC-2.2 Bjmag 11.36 / Vmag 9.43; USNO-B1.0 B1mag 11.19, B2mag 10.09 / R1mag 8.45, R2mag 8.38; USNO-A2.0 Bmag 11.6 / Rmag 8.1

2MASS All-Sky Catalog of Point Sources [2mass]
AGK3 Catalogue (Dieckvoss, Heckmann 1975) [i/61b]
BD: Bonner Durchmusterung (Argelander 1859-1903) [i/122]
GCVS: Gen. Cat. of Variable Stars 4.2 (Vol. I-III) [ii/250]
GSC: HST Guide Star Cat., ver. 1.2 (Lasker+ 1996) [i/254]
GSC-2.2 Catalogue (STScI, 2001) [GSC-2.2, i/271]
GSC-ACT: HST GSC, ver. GSC-ACT (Lasker+ 1996-99) [gsc-act]
HD: HDE (H. Draper) Charts: p.p.m. (Nesterov+ 1995) [iii/182]
PftP: Planetarium for the Palm, version 2.4beta4c
SAO: Smithsonian Astrophysical Observatory Star Cat. [i/131a]
Tycho-2 Catalogue (Hog+ 2000) [i/259]
UCAC2 Catalogue (Zacharias+ 2003) [i/289]
USNO-A2.0 Catalogue (Monet+ 1998) [i/252]
USNO-B1.0 Catalog (Monet+ 2003) [i/284]

The Greek alphabet: α alpha, β beta, γ gamma, δ delta, ε epsilon, ζ zeta, η eta, θ theta, ι iota, κ kappa, λ lambda, μ mu, ν nu, ξ xi, ο omicron, π pi, ρ rho, σ sigma, τ tau, υ upsilon, φ phi, χ chi, ψ psi, ω omega


Tag said...

Nice work on your efforts.

A bit off topic: I am interested in your ongoing side study of your NELM/BLM experience. Had you conducted a similar effort with the 7x50 bins? Your limiting magnitude with them was somewhere around 8.6 or so? I am curious how closely your experience with NELM/BLM agrees with the some of the literature out there.


Ben C. said...

Peter: If you look at the 'Summaries through Feb 2005' I list the BLM at 8.6 on the nights I started measuring this feature in the Fuji 7x50's. BLM = ~8.5 were estimates. I've been looking for a formula to predict what the mag. gain would be and one from Carlin [3LOG(Dcm) + 2LOG(magnification) + 0.6 + NELM] (Dcm = diameter in cm) works out to 9.2 with the 7x50's using an NELM of 4.8. This number seems too high. For the Fuji 10x70's this would work out to 9.9. Research shows that magnitude gain plus NELM is not linear for increasing apertures. See article by EdZ at which I'm sure you've seen. I'm not sure why Carlin's formula uses a +0.6. I'd like to find out what this represents. I have a feeling NELM + mag. gain for the same optics is probably linear and this can be demonstrated by comparing TotL BLMs to a dark sky site's BLM.