Lynds Bright Nebulae (LBN) 635

[Tom Davis]

Here is a faint one in Cassiopeia. It requires a lot of exposure time to come up with anything! Stretch that data!!!!

http://www.tvdavisastropics.com/astroimages-1_00009c.htm

Tom

[multiweb]

Wow. Another great pic Tom. Really well processed too. :thumbsup: Quick question for you. Would a C11 with an Hyperstar 3 give a "similar" result in term of luminosity capturing faint dust? I realise the optics are not as sharp but I'm talking about how fast the scope becomes. Apparently it would go from F/10 down to approx F/3?

[Tom Davis]

I believe it would. An 11" aperture at f/3 would be quite the dust catcher!

Tom

[dpastern]

Noice - look at all that faint detail.

Dave

[DavidU]

Ohhhh nice ! Man that must be faint......

[renormalised]

Actually, Marc, for a C11 it's f/2, so it's even faster.

[renormalised]

Nice shot, Tom. The detail is quite breathtaking:D:D

[Matty P]

That's amazing Tom.

I can't imagine how faint this object is. You have captured it very nicely.

:thumbsup:

[multiweb]

I know starizona sells them but they don't ship outside of US. I wonder where to find an hyperstar 3 in Oz? :shrug:

[AlexN]

Excellent image Tom

[sjastro]

That's a fine image Tom.

On the subject of optics, there was a recent thread that dispelled the myth that reducing the f/ratio of a telescope by reducing the focal length resulted in faster optics.

http://www.iceinspace.com.au/forum/showthread.php?t=50007

Regards

Steven

[multiweb]

Yes but in this case we're talking about an 11" SCT with an F/2 primary. The secondary (F/5) is taken out. So it's not like you're correcting an F/10 primary on a newtonian.

[Lester]

Fantastic, deep image Tom. Thanks for the view.

[sjastro]

It doesn't matter.

For equivalent CCD or CMOS exposures, the number of photons collected is dependent on the diameter of the mirror (or lens). Unlike stopping down a camera lens, you are using the same diameter mirror in which case you won't be going any deeper using the optical system at f/2.

Note the principle doesn't apply to photographic emulsions.

Regards

Steven

[AlexN]

I beg to differ... I've seen the results of shooting IC434 through a C11 with a QHY8 @ F/10 and at F/6.3... 10 minute exposures struggle to bring out the fainter nebulosity, I've seen 30second subs of IC434 through a C11 with Hyperstar and the results are amazing...

This is however, a conversation for another thread rather than trashing up Toms thread...

[multiweb]

My Hyperstar 3 is on its way so as soon as I've got it I'll image at F/2 and F/10 and compare.

[sjastro]

Shooting at lower f/ratios (lower FL) results in a larger pixel scale and camera noise less obvious on faint objects. The fainter nebulosity may appear to be smoother but you are not going any deeper.

Regards

Steven

[multiweb]

Agreed. Visually the faint stuff should look brighter then. 11" at F/2 ot F/1.8 is approx 510mm FL with an image scale of 3.2arcsec/pixel with the QHY8. I calculated the FOV to be just a bit bigger than my 5" newt at F/5

[Tom Davis]

The point is: use as large of aperture that you've got for a long as you can stand! As for me, I like wide FOV images so I use short f.l. scopes. I'm not an physicist, just a guy who likes to image faint extended objects.

Tom

[atalas]

Wonderful as always Tom!