The Celbridge Deep Field

Folks - the observatory is coming on (still haven't decided on a name yet...) with just the front doors to do.

I have to say that it really makes a huge difference not having to tear the setup down each session. Just roll away the shed and there she goes.

Anyway, I shot off a few test images last night. With the polar alignment getting better, I managed a three minute unguided shot and there's more in the mount as well. So hopefully I can get up to 4 or 5 minutes eventually - possibly even more with the AP training routine.

I took this one of M39 (well, a portion of it) and on doing a search through Aladin, came up with an identifiable star down to mag 18.6. Now this was the Red plate in the USNO2 catalogue but from what I can tell, Visual magnitudes tend to be a greater number than the R magnitude. So, a V mag of 13.8 equates to an R mag of 13.7, 15.5V to 15.1R, 15.1V to 14.9R and so on. If that's the case, then the setup I have has gotten down to a V mag of 18+. The relationship between V and R mags doesn't seem to be linear though. I guess it depends on the temperature of the star and its composition on how the two are related. Anyhow, I'm pretty sure that I can get down to Mag 18 now.

Here's the image, details below:



Object M39/NGC7092 (open cluster))
Date/time 10/08/05 23:33 UTC
Exposure 60 sec
Image no. 2
Imager DSI
Mount AP1200
Scope C8 SCT

hi Dave,

really excellent results. You should try for the big one (tenth planet) . . . lots of backyard observers getting images as it's magnitude 18.9 at the moment.

more at www.extrasolar.net/planettour.asp?StarCatId=&PlanetId=297

all the best,

John

P.S. did you get my PM earlier in the week? Will talk to you on Saturday night as I'll be at the KAS Star Party.

Good work Dave. I'd be amazed if you couldnt go even deeper than 18th mag. I understand CCD imagers routinely go down to 22nd mag. I'd also be amazed if you wernt able to do at least three minutes unguided with that mount of yours, and I dare say you could go a bit longer too. The issue that will limit you is the repetitive worm cycle mening whatever periodic error is present will repeat itself at equidistant intervals. I assume the AP1200 has PEC so that shouldnt be a problem.

I've been hatching a plan to have a go at UB313 too. I reckon it shouldn't be too tricky given a decent night and a dark sky, its relatively high and there are a couple of bright field stars close in too.

UB313 may be a stretch with the 8 incher. I know an 11" SCT can get down to mag 19.6, 16 inches will get you over mag 20. And a 20" RC will get down to the level that those moneybags astrophotographers get down to.

Funnily enough, the image above was the 60 sec exposure. The 180 sec exposure had loads of noise. But then I didn't do a 3 minute dark becasue it was a bit of a trial. Witha 3 minute reduced image, I still think I can't get much below mag 18 or so. And I'd be suprised if I got to mag 19...

The AP1200, as well as PEC (which can get the mount to less than 1.0 arc-second peak to peak error) also has the ability to 'record' the movements of an object. If you want to track say an asteroid, you center the object, start recording, wait 10 minutes or so, then recenter it. The 1200 will then faithfully reporduce those movements and keep the object centered. I believe that unguided exposures of 30 minutes (yes, minutes) have been achieved this way.

But I think the limiting factor then becomes the light-gathering power of the OTA and the sensitivity of the CCD plus signal-noise ratio.

But there's be no harm trying. I feel another project coming on... Who will be first person in Ireland to image the tenth planet?....

Cheers
Dave

And a 20" RC will get down to the level that those moneybags astrophotographers get down to.

Mount AP1200....

:lol: :lol: :lol:

Great image by the way. Keep pushing the limits... be interesting to see how far it can go.

They have the AP1200 AND an RCOS AND an SBIG/FL CCD plus the latest software, focuser, deheater AND they have bought a plot of land in Arizona/NewMexico for their remote observatory (18 footer of course). The real big guns must be well into 6 figure sums. I just broke 5 figures...

Of course, I had my way... Better go buy a Lotto ticket

Cheers!

Dave McD