It only took a minute

[Demonperformer]

From all the hardware/software experimentation I have been doing over the last couple of nights, here is a single 60-second unguided sub. I just wanted to see what I could get with my setup before I started using the guiding, to give me a baseline from which to judge my future efforts.

The setup was my 8" SCT + SXV-H9 (unbinned) on the NEQ6, aligned with polemaster.
The original image file was FITS, but it has been converted to JPEG for upload.
The bright star near the centre of the image is BD+84 12 (Vmag 9.80, according to CDC).
Star 'A' appears on CDC, stars B-D do not appear on my version of CDC (which has UCAC4 loaded, but nothing more comprehensive), but the approximate positions are labelled on the screenprint.

In each case (B-D), I have identified the star in question by getting a guestimated position from CDC, entering this as the search position on Vizier J/PASP/116/1012/catl [A star catalogue for the open cluster NGC 188 (Stetson et al, 2004)]. In each case, I selected the most likely candidate of those stars listed as being near the guestimated position by (1) eliminating any star brighter than m16.0, as this would have been displayed on my version of CDC, (2) eliminating any star fainter than m19.0, as being highly unlikely to have been recorded when brighter stars were present, (3) selecting the star closest to the guestimated position. The errors in my guestimates ranged from -3.50s to +0.59s in RA and -11.6" to -14.8" in Dec.

Star A = UCAC4 876-000326, magnitude given as 16.90 [from CDC]
Star A = SMV 5744, Bmag=17.613, Vmag=16.799 [from Stetson]
Star B = SMV 6404, Bmag=17.512, Vmag=16.808
Star C = SMV 7384, Bmag=17.781, Vmag=16.940
Star D = SMV 7313, Bmag=18.082, Vmag=17.563
Star D+= SMV 7303, Bmag=17.624, Vmag=17.092

OK, one sub is hardly a scientifically significant sample, but the results suggest that I have got at least to Vmag 17.5 - which I find to be surprisingly deep for a single 60s sub, under streetlights. Unfortunately, I was so involved doing other things, I forgot to take an SQL reading, but typically (based on readings taken previously) I would expect it was between 17.5 & 18.0.

All-in-all, I think this suggests I have some interesting times ahead, tracking down (potentially) some very faint objects.

Thanks.

 

[knobby]

60 seconds unguided ... Nice work 

[Demonperformer]

Thanks, Knobby.

Of course, we should remember that NGC 188 is within 5º of NCP. I somehow doubt I would have got quite such round stars on an unguided sub if I had done the same experiment near the celestial equator.

[Bonnylad]

1 hour ago, Demonperformer said:

Thanks, Knobby.

Of course, we should remember that NGC 188 is within 5º of NCP. I somehow doubt I would have got quite such round stars on an unguided sub if I had done the same experiment near the celestial equator.

That answered a big question as to no trails.

[Demonperformer]

Quick update:

Based largely on this incident, I am in the process of upgrading my version of CdC to include the PPMXL catalogue (to mag 20). Details here. A quick check shows that the faintest star identified in the first post (star 'D') is PPMXL 478059667753169204, which is spot-on for SMV 7313, my selection as 'most likely star'. So reaching Vmag 17.5 in the image is confirmed.

Thanks.