DS imaging at very slow F ratios.

[ollypenrice]

I'll take the liberty of putting here a link to an image which challenges many popular assumptions.

Even as an advocate of the idea that the F ratio myth really is a myth, this data set amazed me. See what you think.

Olly

[Zakalwe]

A wonderful image that  shows the advantage of good dark skies. Try doing that in a light polluted area with poor transparency and seeing...

[ollypenrice]

38 minutes ago, Zakalwe said:

A wonderful image that  shows the advantage of good dark skies. Try doing that in a light polluted area with poor transparency and seeing...

But, even so, if I'd asked, 'What will I get using a six inch scope at F15 with 3 minute subs?' I suspect the bulk of the replies would have been along the lines of, 'Not a lot!' My own sky here has seen SQM22.05 but I'm still amazed by the combination of short subs and slow F ratio.

Olly

[swag72]

I've been giving this some thought........ and looking about and doing some processing myself...... I think that the BIGGEST factor in all of this is dark skies. If you don't have them, then life becomes a little more difficult. That's my take on it from my SQM 20.3 .....(On a VERY good night) ....... location.

[johnrt]

7 hours ago, swag72 said:

I've been giving this some thought........ and looking about and doing some processing myself...... I think that the BIGGEST factor in all of this is dark skies. If you don't have them, then life becomes a little more difficult. That's my take on it from my SQM 20.3 .....(On a VERY good night) ....... location.

I'm backing Sara on this, I tried dropping to f/9 with my 6" RC and it was woeful, my skies are far from dark, I can make out no trace of the Milky Way above my head. Non starter for me unless you're amongst the blessed few with inky black over their heads at night.

[Merlin66]

90% of all the Astro imaging done in the 1970's and later were done by amateurs using f10 SCT's.

with hypered film etc the results, at the time were far beyond any previously obtainable.

Times, and equipment changes......

Fast systems are great for extended nebula, slow systems excel for stars.

 

[andrew s]

In the end given good optics, stable mechanics and mount etc. it comes down to how many photons you collect from the target compared to noise from the sky, read noise, photon statistics etc. 

For photon statistics (target and sky background) S/N goes with the diameter of the optics and sqrt(exposure time).

Regards Andrew

[wimvb]

12 hours ago, swag72 said:

I've been giving this some thought........ and looking about and doing some processing myself...... I think that the BIGGEST factor in all of this is dark skies. If you don't have them, then life becomes a little more difficult. That's my take on it from my SQM 20.3 .....(On a VERY good night) ....... location.

As in real estate, it's very much about location. When I imaged M45 last year from my dark site, I could pull out faint dust without too much effort. But from my home front yard in the suburbs, no such luck. Even with more total exposure time, my images are drowned in noise after applying DBE.

Location, location, location.