M33/ modifed webcam, M33 Atik 314L

[JohnP]

Don't think Fay had SC3...?

[Fay]

SC3

[JohnP]

I stand corrected... I didn't know that you had a webcam with the SONY ICX424 AL chip in.... sorry...

[Rick]

You can have ...

And, conversely, if your kit is poor, that's going to limit what you can achieve.

The difference between the two images is amazing. Likewise yours of M42. I was hoping folks might actually look a little deeper, think a bit about what makes a difference, and maybe share some of what they've learned. If the way the improvement was achieved is treated as a black art then how's anyone else going to learn anything from it?

[Rocket Pooch]

Hi Rick,

There are a few things I noticed which made a massive difference in my images, the 1st was to have an actual cooled asto CCD, being able to Autoguid Properly and have optics at least F7.5 or faster, basically anything to get the signal to noise better.  After that we can all argue over QE, Ha Sensitivity and scope designs, but that the finer point of the sport.

For example Atik 314L and ED80 F7.5 required four times the exposure than a Atik 314L and a 6" Newt at F5, but the newt's stars may have diffraction spikes, etc etc.

The second part, and this is where some people here have come on in leaps and bounds, is to understand the processing process, it really does not matter how good the subs are, if you don't combine them properly the result are crap, for example I have a perfectly good noise free set of LRGB of the packman, but I can't quite get it right yet and the image looks rubbish.

Oh yes and light pollution this has probably the biggest effect on LRGB than anything.

Chris


I'll dig out my 2004 M33 but here's the 2008, the only difference between fays and mine (taken on the same night, same conditions, same location) was Fay was shooting at F7.5 I was shooting at F5 and my subs were 10 minutes, I think Fays we're 5 minutes, I have 5x the signal to noise.

[Fay]

We have to consider location as well, also seeing conditions, very important. Very nice M33 Chris

[Fay]

I think an SC3 mod was the replacement of the chip for a more sensitive one. I Can't remember which chip it was. I think they do mods different now.

[Daniel]

Fantastic progress Fay, Im sure equipment helps a lot, but technique definitely has a massive part to play, a big revelation I've had is that I now don't go hopping about the universe looking at objects, I make a choice on what Im going to image at the start and stick with it. I was trying to see too much, but not getting enough data on any one object before, hence some of my images being a bit better as of late.

[Fay]

Yes, I tend to get excited when I see all the goodies up there & want to do more than one a night!!!!!!!


Looking at the quality of Chris's M33, you can see where his experience in guiding & processing make such a big difference to an image. I was having a problem with guiding & although sorted, it was not good enough, that night, for 10 minutes, whereas Chris's was fine.

[Fay]

Chris what F5 scope have you got?

[Daniel]

For me the biggest problem has been noise, and im definitely noticing the difference by not hopping about so much and getting good long exposures (im looking to add to my M42 and horsehead this year, I'd like to get a full 12 hours on both) Im hoping to get around my S/N problems using the DSLR quite soon, not by jumping to a cooled camera (don't think im ready for that yet) but I've finally ordered a hyperstar and im hoping to get my sub times down to under a minute (probably as high as I'll be able to go with the light polution around here)

Chris, im just wondering, I saw your working out of the S/N of yours and fays kit, do you know how much light gathering power the 14" at F1.9 would have over the 120ED at F7.5 im using right now?

[RobertM]

Don't know about light gathering but I'm sure it would be 100-200 times faster at capturing the same data.  I feel you may have hit the nail on the head when it comes to faster imaging in LP skies, so it will be very interesting to see your results, especially with the V3 Hyperstar and DSLR chip combo.

[Mac]

The light gathering part is easy, its just the following equation (size of large scope/size of small scope) squared.
it should realy be area, but the 2*pi, cancells out on both sides.

which works out as (355mm / 100mm) squared = 12.6

So for the same F ratio you scope has 12.6 time the light gathering power.

The differences in the F stop 1.9 over 7.5 work out roughly the same as F2 & F8 (easier on the maths), so this is a ratio of 4.
Exactly it 3.9......

F2 = 1min
F4 half the light. twice the time, ect. (better depth of field)

so its roughly 12.6 * 4 which is about 50 times faster

So if you took a 1 min sub on the 14" at F1.9, you would need to take a 50min sub roughly on the ED120.

to give you a better example. if you took a 1min sub on the keck (Single mirror), and compared it to your hyper star.
(keck/14")^2
(10m/.355m) the light gathering power of the keck is ~800 time that of your 14"

Cant find any data about the F stop for the keck.

[Fay]

Chris, I see your M33 was taken thru Ollys Celestron Genesis. Is that a better scope than the Skywatcher?   

[Fay]

Mac, you are so clever!