#1  
Old 01-04-2016, 05:30 PM
raymo
Registered User

raymo is offline
 
Join Date: Sep 2011
Location: margaret river, western australia
Posts: 5,092
Stunning DSLR images. How!

There are a few people out there that produce stunning images with DSLRs that are, to the uneducated eye at least, hard to separate from high quality CCD camera images.
Is how they do this the result of doing each step in the process of
capture and processing as close to perfectly as humanly possible? or
are there one or two discrete things that make these images possible, such as very dark sky sites, very long duration subs, huge total
exposure times etc: CCD cameras seem to be inherently sharper than any
DSLR, so how do these people produce images that rival CCD images?
Post capture sharpening?
raymo
Reply With Quote
  #2  
Old 01-04-2016, 05:36 PM
Somnium's Avatar
Somnium (Aidan)
Aidan

Somnium is offline
 
Join Date: Oct 2014
Location: Sydney
Posts: 1,669
Check out this video by Tony Hallas , he does amazing dslr work and goes through some tips and tricks https://m.youtube.com/watch?v=PZoCJBLAYEs
Reply With Quote
  #3  
Old 01-04-2016, 05:44 PM
blink138's Avatar
blink138 (Pat)
Registered User

blink138 is offline
 
Join Date: Aug 2009
Location: perth w.a.
Posts: 2,235
a cool climate does help a lot raymo with a dslr sensor!
pat
Reply With Quote
  #4  
Old 01-04-2016, 05:49 PM
Atmos's Avatar
Atmos (Colin)
Ultimate Noob

Atmos is offline
 
Join Date: Aug 2011
Location: Melbourne
Posts: 6,628
If you over-sample quite a bit a DSLR can perform virtually to the same level as a mono CCD. The reason for the loss of sharpness is due to the bayer matrix. A 12mp DSLR has 3mp of red, 3mp of blue and 6mp of green. This does not just limit overall transition but also resolution. All of this you are probably quite aware of.

If you under-sample using a OSC on a short focal length scope you don't get the same resolution as it is lost in "missing pixels"... so to speak. If you over sample you have several RGGB "pixels" covering each star.
Reply With Quote
  #5  
Old 01-04-2016, 06:21 PM
raymo
Registered User

raymo is offline
 
Join Date: Sep 2011
Location: margaret river, western australia
Posts: 5,092
I'll have a better look at it later Aidan; I used to follow Tony's work back
in the days of film. He did the best film version of M31 that I have ever seen.
Yes I'm well aware of the benefit of coolth Pat.
Colin, being as I am an old gas emitter, I have no idea how to under or
over sample anything.[except maybe chocolate or ice cream].
As I get nearer and nearer to the great black abyss I seem to be
going from high school back to primary school, and finally back to
kindergarten and childcare.
raymo
Reply With Quote
  #6  
Old 01-04-2016, 06:44 PM
glend (Glen)
Registered User

glend is offline
 
Join Date: Jun 2013
Location: Lake Macquarie
Posts: 5,637
You can create your own cold climate DSLR Raymo, just do a cold finger mod and shoot at 0C or below. If you want all those pixels working full-time get rid of the bayer matrix and run mono. Even if you don't want to do it yourself there are mod for hire businesses like CentralDS.
Reply With Quote
  #7  
Old 01-04-2016, 06:58 PM
raymo
Registered User

raymo is offline
 
Join Date: Sep 2011
Location: margaret river, western australia
Posts: 5,092
Hi Glen, Yes I am aware of that option; the only trouble is that I can't
decide whether it is worth selling my treasured Hartungs, and various
other possessions, in order to find the wherewithal.
raymo
Reply With Quote
  #8  
Old 01-04-2016, 08:14 PM
Atmos's Avatar
Atmos (Colin)
Ultimate Noob

Atmos is offline
 
Join Date: Aug 2011
Location: Melbourne
Posts: 6,628
Over sampling and under sampling is just a matter of focal length. If you increase focal length you increase the number of pixels that each star (and therefore detail) covers. Working at an image scale of, let's say, 0.5"/pixel with a OSC could theoretically perform the same as a mono.
Reply With Quote
  #9  
Old 01-04-2016, 08:44 PM
raymo
Registered User

raymo is offline
 
Join Date: Sep 2011
Location: margaret river, western australia
Posts: 5,092
So following that reasoning, if I make my 1000mm scope effectively a
2000mm one by using a 2x barlow, I would get better resolution. I also
presume that you could keep going until the object becomes too dim to
image properly. That seems counter-intuitive, as we all know that the image quality drops away as the magnification increases, or is one supposed to use lower and lower power EPs to keep the target's apparent size unchanged.
Would that mean that a 2000mm scope using 20mm EP[100x mag]
would give a superior image to a 1000mm scope using a 10mm EP[100xmag]?
raymo
Reply With Quote
  #10  
Old 01-04-2016, 10:17 PM
rmuhlack's Avatar
rmuhlack (Richard)
Professional Nerd

rmuhlack is offline
 
Join Date: Nov 2011
Location: Strathalbyn, SA
Posts: 873
from my experience with DSLR imaging, the key was to take all steps possible to increase signal to noise. For starters, I image from dark rural skies which helps considerably compared with an urban location. After various tests, I worked out an ISO and sub time that would give optimal signal to noise for my camera. This was about 3-4 minutes at ISO 1600 when I was using an uncooled DSLR, and then 8-10 minutes at ISO1600 when I used cold finger modded DSLRs. Making sure that darks and bias frames were temperature matched with lights was important, and then making sure collimation and focus were good during capture. I mainly used two telescopes - one with a focal length of 1278mm, and another at 650mm. I also had several images using Nikkor camera prime lenses which also worked well.

After that, my images made a huge leap forward when I started processing my images with Pixinsight - this allowed me to really pull all the data out of my images. From there it was then about extending total exposure to as long as possible - my maximum exposure was about 50 hours, with many images going for 15-20 hours or longer.

A lot of effort, but I think the resulting images hold their own, eg http://www.astrobin.com/users/rmuhla...blic=&sub=year

Moving to mono CCD has been a further learning curve - i haven't been nearly as productive with my imaging since I made the switch for various reasons (work-life balance being part of the equation, as well as other equipment issues which have held me up, like my obs computers both needing to be replaced). Hopefully those issues are now dealt with, and I can look forward to more imaging in 2016.
Reply With Quote
  #11  
Old 02-04-2016, 01:44 AM
raymo
Registered User

raymo is offline
 
Join Date: Sep 2011
Location: margaret river, western australia
Posts: 5,092
Thanks for taking the time to respond; all comments are carefully noted.
cheers raymo
Reply With Quote
  #12  
Old 02-04-2016, 12:46 PM
kkk26's Avatar
kkk26 (Chit Ko Ko)
Registered User

kkk26 is online now
 
Join Date: Sep 2010
Location: Woodlands, Singapore
Posts: 8
Excellent images, Richard. All images were captured with DLSR? I am always interested to get cool modded DSLR
Reply With Quote
  #13  
Old 02-04-2016, 01:02 PM
rmuhlack's Avatar
rmuhlack (Richard)
Professional Nerd

rmuhlack is offline
 
Join Date: Nov 2011
Location: Strathalbyn, SA
Posts: 873
The lunar images were taken with a qhy5l, however the other images linked there were all taken with a DSLR.
Reply With Quote
Reply

Bookmarks

Thread Tools
Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT +10. The time is now 02:40 PM.

Powered by vBulletin Version 3.8.7 | Copyright ©2000 - 2020, Jelsoft Enterprises Ltd.
Advertisement
Lunatico Astronomical
Advertisement
Testar
Advertisement
Bintel
Advertisement
Astromechanics
Advertisement
Astronomy and Electronics Centre
Advertisement