Lynds Bright Nebulae (LBN) 635

Tom Davis (Tom) · #1 29-09-2009, 12:05 PM

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/astr...s-1_00009c.htm

Tom

multiweb (Marc) · #2 29-09-2009, 12:25 PM

Wow. Another great pic Tom. Really well processed too.

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 (Tom) · #3 29-09-2009, 12:54 PM

Quote:

Originally Posted by multiweb

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?

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

Tom

dpastern (Dave Pastern) · #4 29-09-2009, 01:27 PM

Noice - look at all that faint detail.

Dave

DavidU (Dave) · #5 29-09-2009, 03:41 PM

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

renormalised (Carl) · #6 29-09-2009, 05:41 PM

Quote:

Originally Posted by multiweb

Wow. Another great pic Tom. Really well processed too.

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?

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

renormalised (Carl) · #7 29-09-2009, 05:42 PM

Nice shot, Tom. The detail is quite breathtaking

Matty P (Matt) · #8 29-09-2009, 06:46 PM

That's amazing Tom.

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

multiweb (Marc) · #9 29-09-2009, 08:16 PM

Quote:

Originally Posted by renormalised

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

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

AlexN · #10 30-09-2009, 05:30 AM

Excellent image Tom

sjastro · #11 30-09-2009, 06:50 AM

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/s...ad.php?t=50007

Regards

Steven

multiweb (Marc) · #12 30-09-2009, 06:43 PM

Quote:

Originally Posted by 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/s...ad.php?t=50007

Regards

Steven

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 · #13 30-09-2009, 07:04 PM

Fantastic, deep image Tom. Thanks for the view.

sjastro · #14 30-09-2009, 07:24 PM

Quote:

Originally Posted by 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.

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 · #15 30-09-2009, 07:36 PM

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...

Quote:

Originally Posted by 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

multiweb (Marc) · #16 30-09-2009, 07:50 PM

Quote:

Originally Posted by 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...

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 · #17 30-09-2009, 08:12 PM

Quote:

Originally Posted by 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...

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 (Marc) · #18 30-09-2009, 08:18 PM

Quote:

Originally Posted by 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

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 (Tom) · #19 01-10-2009, 12:26 AM

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 · #20 01-10-2009, 04:12 PM

Wonderful as always Tom!