NGC7242

[petevasey]

NGC 7242 is a fairly faint (mag 12.9) elliptical galaxy, notable for being the main member of a small group of galaxies in Lacerta. The nights of 29th and 30th of October gave me the opportunity to capture enough data. Only just enough colour - clouds moved in towards the end of the RGB run in the small hours of 31st. QSI 683 on RC10 with SX AO. Luminance 13 out of 16 (clouds!), R & G 4, B 3 subs all 10 minutes binned 2x2.

 

 

Edited November 4, 2019 by petevasey

[MartinB]

That is a lovely galaxy cluster.  A beautiful image.  Did you manage to find a decent guide star? What magnitude do you find that you need for AO to work for you?

[petevasey]

Thanks, Martin,

The full size image (without annotations) is now posted on my web page, here.

As it happens, a very bright guide star was available for this one - 1 Lacerta, mag 4.12 as in the Skymap clip below.  I generally look for at least mag 9 which will give me AO exposures around 3 per second.  Fainter stars can work ok particularly if the sky is very clear.  But even if I'm down to 1 second or even longer exposures, it's still worth using the AO because of the rapid response - only the inertia of a little glass plate instead of the whole mount to be moved.   When I have sub second exposures, any mount movement required due to drift of one kind or another taking the guide star beyond the pre set limits of the AO, the AO corrections continue as mount corrections take place, so the mount movements are completely compensated for.   I always use the AO for longer focal lengths, although with my TS65 quad (420mm fl) it's not necessary, particularly on my Observatory mount.

Cheers,

Peter

Edited November 3, 2019 by petevasey
Added link

[MartinB]

Thanks Peter.  I have used AO a fair bit myself but always aimed for 4 or more corrections per sec which limited the targets available.  I might dust it off and put it back into service!