Re: [APML] OT: M109, NGC 2403 and other collaboration images

["Greg Hartke" <ghartke@adelphia.net>]

Hi, Duncan,

Echoing Jason, there are 2 important properties to consider to get the most 
out of your processing: shoot at a scale such that your image is oversampled 
and take long and many subexposures to get a large signal-to-noise ratio. 
Imaging with this in mind will, again as Jason said, give you the 
opportunity to be aggressive with your processing and get as much out of the 
image as possible. It goes without saying that you also need impeccable 
technique and excellent optics to do this. We may be able to develop a high 
SNR with our smaller scopes but we'll never be able to duplicate the 
oversampling of the large scopes which allows aggressive image processing. 
For that reason, we'll never quite be able to match the images of the larger 
scopes. You just can't fight the combination of light gathering power and 
image scale.

This tells us in part why film imaging is so difficult. To get the 
equivalent signal-to-noise ratio of a well done CCD image (at the equivalent 
image scale) would be murder. Rob Gendler might have 5 hours of data for an 
image which could consist of ten 30 minute subexposures. To approach his 
subexposure depth in a film image might require 2 to 3 hours. (Even so, 
would the film image be as deep?) Can you imagine finding the time to do 
that 10 times? I can't. Like so many of us I'm fighting weather and schedule 
and it just ain't possible.

Like you, I also have a 10" f/6.3 LX-200. I'm not really using it right now 
because I'm shooting with a 152 mm f/7 refractor. I like the image scale of 
the LX-200 OTA but after using the refractor I'm spoiled by the better 
optics. The LX-200 was a blast and an excellent platform for learning but my 
taste has gone a bit beyond it now. I'll work on improving my technique with 
the refractor and eventually get something else with the image scale I want 
and suitable optics.

Of course, I'll never develop the amazing processing skill of Rob and others 
here simply because I don't have the time, never mind the talent. ("Not 
having the time" is another way of saying that the priority of this hobby is 
not high enough in my life to warrant the requisite level of effort.) That's 
OK because I can already see that with I've learned here I won't embarrass 
myself, either. At least not too much.

I don't really know how close film can come to CCD images. I've seen film 
images in recent years that left me dumbfounded. Now I look at CCD images 
such as those of Rob, Tony Hallas, and others and they make the best film 
images look soft and not nearly as deep. It's amazing how our expectations 
evolve as the technology expands. FWIW (which ain't much), here's the way it 
looks to me: The best film images (and they're truly excellent) are just not 
as deep or sharp as the best CCD images. Then again, looked at differently, 
both are outstanding but  in different ways. I would say the preference of 
one over the other lies in esthetics which is another way of saying ya like 
what ya like.

One thing is for sure: It's certainly a fabulous time to be involved in the 
hobby. I've been an amateur for over 35 years and this is far and away the 
most exciting time I've seen. Is that cool or what?

Regards,

Greg

----- Original Message ----- 
From: "Duncan Munro" <dmunro@sfu.ca>
To: "Discussion of Film Astrophotography" <astro-photo@seds.org>
Sent: Wednesday, March 02, 2005 11:30 PM
Subject: Re: [APML] OT: M109, NGC 2403 and other collaboration images


> Greg , hi.   I look at Jim Misti's images and I see a challenge, in 
> several ways.  For starters, even though he has a 32" scope he can still 
> only resolve to the limits of seeing which does (or not?), theoretically, 
> allow "mere mortals" like us to match his images, albeit with some 
> difficulty.
>
> for example 32" F7.2 + SBIG 1100 = 14.3x21.5 min FOV with .32 arc/sec 
> pixels.
>
>                   10" F10 + SBIG ST8= 12.6x18.9 min FOV with .74 arc/sec 
> pixels
>
> both systems have a similiar FOV and both should resolve to the limit of 
> seeing. I guess the question becomes: How close can a mortal using the 
> above Meade compare to gods?  Could a very dedicated Meade 10" F10 user 
> resolve to the same limits as a 32" F7.2?
>
> 2ndly, how close could I come using my 10" f6.3 at F4.4 and a lowly ST-7E? 
> 10" F4.4 + ST7= 14.3x21.4 min FOV with  1.68 arc/sec pixels. Let's say I 
> fly to Mauna Kea, and guide my scope to it's absolute limits. How close 
> could I come to duplicating Jim's images, in terms of resolution and 
> depth?
>
> The last question is how close can film come to competing with CCDs? Could 
> a well corrected 10 to 12" OTA using film match a 32" 7.2 using a large 
> format CCD camera? Perhaps film could match it with stacked multiple 
> images and continuously temperature adjusted focus?   How about a DSLR and 
> a 10" OTA?
>
> Finally, I could probably build a 25-30" f4 coma corrected newtonian with 
> a  computerized 3 axis  mount for about the same cost (maybe a little 
> cheaper) as all my existing equipment  so it's not really out of the 
> question even for Joe LunchBuckets like me...
>
> cheers
>
> Duncan 

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