How deep is this image..?

[strongmanmike]

Be interested to know if anyone with a good star atlas program can add a few more magnitude labels to this image:

http://upload.pbase.com/strongmanmike2002/image/116253840/original

Cheers

Mike

[DavidU]

Are you trying to out do Hubble?
Deep as !

[seanliddelow]

Wikisky will show you the mag of galaxies up to 15-20:thumbsup:.
Just find the same patch of sky.

[Robh]

Sean, for curiousity, tried Wikisky.
Very useful resource. Nice interface and images.
I like the fact you can drag the maps to centre at a specific point.

Mike, great picture.
Didn't recognise the galaxies at first then realised you've featured two of the Grus Quartet.

Regards, Rob

[renormalised]

I have a fairly good eye for telling magnitudes....I'd say the faintest blobs you have in there are down around +20 to +22, but best to checkout with a very good atlas. Wikisky doesn't go deep enough....there's blobs in Mike's piccie which don't show up on the Wikisky section of that part of the sky.

[Peter Ward]

Mike, great effort, but sorry, you can't do useful magnitude estimates with processed RGB data.

The drill is the usual reduction (dark+bias/flat) of a calibrated BVR or I into the photometry package of your choice.

Mira and MaximCCD both do splendid jobs. Reference star magnitudes can usually be found via an image link with TheSky or similar. With a calibrated image you can then use known values to measure the unknowns.

My guess with a 6" scope and a KAF11002 will deliver around mag 19.5...very hard to go deeper....but not impossible.

P.S.
I have done many asteroid curves using the same chip and a 14.25" scope. Typically 10 minute subs. The data becomes a little useless
below mag 20.

[seanliddelow]

Probably because it was a dss image. This image looks like it was a sloan digital sky survey image...:thumbsup:

[CometGuy]

Mike,

I converted your full size image to grey-scale, saved it as a fits file and ran it through Astrometrica. According to it you are detecting stars to mag 20.5 V, not bad for a 6" scope!

Terry

[Peter Ward]

How did you correct for non-linear scaling? The posted data is only 8 bit/channel .jpg You *need* a calibrated 16bit (data) frame to make a determination such as this.

[CometGuy]

I just matched the star field in astrometrica, and used the magnitudes given by USNO B1.0 for the matched stars. For example the following crop from Mikes largest image shows a couple of mag 20 stars. The "Vmagnitude" value was estimated using R and B values from the USNO catalogue.

Terry

[Peter Ward]

You missed the point.

The data has been scaled.

[CometGuy]

Yes but I didn't measure data from the image.

T

[Peter Ward]

No you didn't. ;)

[CometGuy]

Mike,

This is a very useful freeby program - Aladin - I use it often:

http://aladin.u-strasbg.fr/java/nph-aladin.pl?frame=downloading

Download the file, run it and type NGC7590 in the "command" window. This will centre the screen on NGC7590, from the "File" menu you can load as many catalogs and survey image overlays as you want (there are 100's available). For stars I would choose the USNO B1.0 catalog as it goes all the way down to mag 21.

Terry

[strongmanmike]

Cheers Terry, thanks heaps

Mag 20.5 huh? cool :thumbsup: not bad for a 6" scope from a semi dark sky I guess?

I will check that program out.

Mike