Jump to content

  •  

CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.

Photo

What can you do in 10 to 30 seconds?

  • Please log in to reply
69 replies to this topic

#51 will w

will w

    Apollo

  • *****
  • Posts: 1280
  • Joined: 13 Aug 2006
  • Loc: oxford,ms

Posted 06 February 2019 - 01:42 PM

Steve,I get confused that you get confused because of some posts here. Its pretty simple.If you dont get in the teck end off it. Dont care about that. It dont show me too much.will w



#52 skyguy88

skyguy88

    Ranger 4

  • *****
  • topic starter
  • Posts: 324
  • Joined: 13 Nov 2006
  • Loc: Prescott, AZ

Posted 12 February 2019 - 08:03 PM

Hi Steve,

 

CCD's being faster than CMOS is not a myth.  Saying that CMOS have caught up and are faster than CCD is the myth.  Everyone has become brainwashed into thinking CMOS is more sensitive because of the beautiful images full of rich detail that they can produce, not realizing that in fact they are taking way longer to get that image.  The problem is that all the images that are posted from CMOS cameras are stacks, while all the images posted from CCD cameras are single exposures.  That is not a fair comparison.  I have done a bucket-load of tests, with dozens of camera models, and for a single exposure CCD's still produce the best SNR...reworded another way, CCD's produce the shortest Time To Observable Image.  Specifically the ICX828 CCD still blows everything else away, by more than a factor of 10.  Slowly I am putting all my testing together to present to the community, it is just taking a lot of time to do correctly.  Please stay tuned, I am on it!

 

Cheers,

 

Jim T.

Hi Jim,

I'm the OP here and I'm anxiously awaiting your conclusions. After happily using Mallincams for outreach for a dozen years, I would like to consider one of the new CMOS cameras to get more resolution on a big screen. I'm having a hard time reconciling your factor of ten with several images that I have found on the image gallery. For example, image gallery page 286, post 7137 (Brian S) and 7139, 40, 42, 43, 44 (Jim Meadows). These images were posted after I asked for short exposure results. And the M27 image at the bottom of Mallincam's DS10 C page. https://www.mallinca...ider-ds10c.html  . I'm anticipating using the camera on a 14 inch f7 (maybe 3.5) scope for an outreach project. I would appreciate your thoughts.

Thanks,

Bill



#53 jimthompson

jimthompson

    Apollo

  • *****
  • Posts: 1077
  • Joined: 06 Oct 2009
  • Loc: Ottawa, Canada

Posted 15 February 2019 - 11:10 AM

Hi Jim,

I'm the OP here and I'm anxiously awaiting your conclusions. After happily using Mallincams for outreach for a dozen years, I would like to consider one of the new CMOS cameras to get more resolution on a big screen. I'm having a hard time reconciling your factor of ten with several images that I have found on the image gallery. For example, image gallery page 286, post 7137 (Brian S) and 7139, 40, 42, 43, 44 (Jim Meadows). These images were posted after I asked for short exposure results. And the M27 image at the bottom of Mallincam's DS10 C page. https://www.mallinca...ider-ds10c.html  . I'm anticipating using the camera on a 14 inch f7 (maybe 3.5) scope for an outreach project. I would appreciate your thoughts.

Thanks,

Bill

Hi Bill,

 

I agree that the images you have mentioned are pretty impressive for short exposure, but be careful in how you compare things.  Both Brian's and Jim's images are on fast scopes, an f/3.5 newt and an f/2 Hyperstar respectively.  Unless you have a similarly fast scope, you will not be achieving the short exposure times that they are.  Also note that Jim's images, although he was using 1 second sub exposures, are stacks of 10.  That means the total exposure time is actually 10sec to get an image.  That is still pretty darn fast, but if you were to put a camera with ICX828/829 on the same telescope I think you'd find you get your image in 1 second but in only one frame (no stacking).  The trade off of course is that the ICX828 sensor is only SD (640x480).  To get higher resolution you need to accept it will take longer to get a final image, and use a CMOS sensor.  Perhaps for your application though 10-20 seconds vs. 1-2 seconds is okay.  If you are trying for really dim objects though, the difference in speed is perhaps more important.

 

One additional note on focal ratio.  You suggest that you will be using a 14" f/7 scope.  You will have problems if you try to reduce that scope down to f/3.5 (reduction of 0.5x) using one of the larger format CMOS cameras such as the ASI294 or ASI1600.  Because of the size of these sensors you can expect lots of coma and vignetting if you try to reduce that agressively.  I find that 0.7x-0.8x is about all I can manage when I use my ASI294.

 

Regards,

 

Jim T.


  • will w likes this

#54 skyguy88

skyguy88

    Ranger 4

  • *****
  • topic starter
  • Posts: 324
  • Joined: 13 Nov 2006
  • Loc: Prescott, AZ

Posted 17 February 2019 - 02:20 AM

Hi Jim,

 

Thanks for the thoughtful response....and for pointing the limitations with the new wave of cameras.

 

I'm hoping to find reason to justify recommending one of the 294 cameras. If it was for myself, I would just order it and find out by operating. But it's not, so I'm considerably more cautious.

 

Starting with the setup that we've been using, Xterminator on an Edge 11 inch OT at f/3.3. 14 inches will get us 62% more photons.

 

The new scope is native f/7.2. The manufacturer sells a .66 reducer. That would yield f/4.9

 

Your experience suggests.....a .75 reducer which would yield f/5.4.

 

The Mallincam image that I linked in my previous post used a .5 reducer. That would yeild f/3.6. I don't see any aberrations in that image.

 

For our outreach program, some coma or vignetting is acceptable, as long as the target object is not effected.

 

Then there is binning. If I understand, bin 2 reduces the effective pixel count by a factor of 4, reduces the linear resolution X2, and increases the sensitivity by X4. The 294 chip has 28 times more pixels than our Xterminator. Binning 2 or 3, would still leave us with much finer resolution than our present setup.

 

Our targets are generally bright. M1, M42, M51, M27, M13, M8, M20, M16, M17, M81, M82, M33,  NGC 4565, NGC 891, NGC 253, etc.

 

We can increase our exposure time modestly. If we decide to chase a fainter target, that is another thing.

 

Putting this all together, it seems to me that it will work well. But I am a novice at this kind of analysis and I would welcome corrections to my naive understanding. 

 

Bill

 


  • will w likes this

#55 alphatripleplus

alphatripleplus

    ISS

  • *****
  • Moderators
  • Posts: 44548
  • Joined: 09 Mar 2012
  • Loc: New Jersey

Posted 17 February 2019 - 09:44 AM

 

 

Then there is binning. If I understand, bin 2 reduces the effective pixel count by a factor of 4, reduces the linear resolution X2, and increases the sensitivity by X4. The 294 chip has 28 times more pixels than our Xterminator. Binning 2 or 3, would still leave us with much finer resolution than our present setup.

 

 

However, the pick-up in SNR for 2x2 software binning is more like a factor of 2, as shot noise adds in quadrature under binning, i.e. 4 times as much signal, but double the noise for bin 2 . See this excellent discussion by Robin Glover.


  • skyguy88 likes this

#56 will w

will w

    Apollo

  • *****
  • Posts: 1280
  • Joined: 13 Aug 2006
  • Loc: oxford,ms

Posted 17 February 2019 - 11:24 AM

Errol, Do you know if Robin Glover is a Electrical Engineer. I know he made up the sharpcap s/w. will w



#57 skyguy88

skyguy88

    Ranger 4

  • *****
  • topic starter
  • Posts: 324
  • Joined: 13 Nov 2006
  • Loc: Prescott, AZ

Posted 17 February 2019 - 03:12 PM

Thanks, Errol

 

Thanks for the clarification....and the link really amplified my understanding.

 

Cuts the margin down some...but I think it's still OK.

 

Great site for getting educated.

 

Bill


  • alphatripleplus likes this

#58 alphatripleplus

alphatripleplus

    ISS

  • *****
  • Moderators
  • Posts: 44548
  • Joined: 09 Mar 2012
  • Loc: New Jersey

Posted 17 February 2019 - 06:28 PM

Errol, Do you know if Robin Glover is a Electrical Engineer. I know he made up the sharpcap s/w. will w

No idea, sorry.



#59 Astrojedi

Astrojedi

    Gemini

  • *****
  • Posts: 3447
  • Joined: 27 May 2015
  • Loc: SoCal

Posted 24 February 2019 - 10:52 AM

Sorry late to this thread. I do a lot of outreach as well and this is a relevant question.

 

I will raise you and ask you what you can do in 1 second.... :)

 

https://m.youtube.co...h?v=iTgVT_WGThM


  • Ptarmigan and tmaestro like this

#60 Astrojedi

Astrojedi

    Gemini

  • *****
  • Posts: 3447
  • Joined: 27 May 2015
  • Loc: SoCal

Posted 24 February 2019 - 11:08 AM

I don’t know why these threads turn in a CCD vs CMOS debate. They are very different technologies with advantages and disadvantages.

 

The biggest value proposition of CMOS is simplification of equipment needed and lowering overall cost to achieve the same results. CCDs can achieve the same results but require longer sub exposures which requires a better mount and potentially autoguiding. Not to mention CMOS sensor based cameras are 2-3x cheaper than CCDs.

 

The main difference between the 2 technologies is read noise. The much lower read noise of the CMOS sensors at higher gains provides much better SNR for shorter sub exposures. With CCDs you need longer subexposures to compensate for the higher read noise.

 

The above is fact not my opinion. But which technology you choose to use is personal preference. I prefer CMOS as I like stacking very short exposures. You may pick CCDs if you prefer longer single exposures.

 

Another side benefit of the lower read noise is that you can have smaller pixels and still achieve the 60-70db target dynamic range that sensor designers aim for. This allows for better resolution with smaller scopes. I achieve better detail on galaxies and smaller objects with my C8 and 183 mono than I used to achieve with my C11 and 8300 sensor.


Edited by Astrojedi, 24 February 2019 - 03:50 PM.

  • Howie1, bsavoie, DSO_Viewer and 1 other like this

#61 skyguy88

skyguy88

    Ranger 4

  • *****
  • topic starter
  • Posts: 324
  • Joined: 13 Nov 2006
  • Loc: Prescott, AZ

Posted 25 February 2019 - 06:43 PM

The purpose of this thread is to clarify the effectiveness of the new generation of CMOS cameras as outreach tools. The main issue is how long it takes to collect a usable image of moderately bright DSO's. I have seen enough examples of fairly short exposure images to be reasonably confident. Still, most of the posted images are very long, too long for outreach....at least my version. I'm guessing that most of the exposure time of those long exposures is adding icing to the cake. But I want to be sure.

 

For me settling evidence would be an image of M51 with the shape being easily recognizable at less than 30 seconds and substantially refined with continued exposure. The rest of the few dozen objects that I use regularly are easier.

 

I suspect that the use of live observing will continue to grow in outreach programs. Settling this issue is important to the outreach community. 

 

Bill

 

 

 

 

 

 

 



#62 Astrojedi

Astrojedi

    Gemini

  • *****
  • Posts: 3447
  • Joined: 27 May 2015
  • Loc: SoCal

Posted 25 February 2019 - 07:44 PM

The purpose of this thread is to clarify the effectiveness of the new generation of CMOS cameras as outreach tools. The main issue is how long it takes to collect a usable image of moderately bright DSO's. I have seen enough examples of fairly short exposure images to be reasonably confident. Still, most of the posted images are very long, too long for outreach....at least my version. I'm guessing that most of the exposure time of those long exposures is adding icing to the cake. But I want to be sure.

 

For me settling evidence would be an image of M51 with the shape being easily recognizable at less than 30 seconds and substantially refined with continued exposure. The rest of the few dozen objects that I use regularly are easier.

 

I suspect that the use of live observing will continue to grow in outreach programs. Settling this issue is important to the outreach community. 

 

Bill

Bill,

Here is a live stacking video of M51. C8 @ F5 using ASI290MM. Shape is visible in 2s exposure and improves with stacking. This video is in fact from an outreach session from my backyard (white/red LP zone).

 

https://www.youtube....h?v=C6HfaIv_VAY

 

I think where CMOS cameras excel for EAA is live stacking using short exposures. CCDs are better with single longer exposures.

 

I have found that for outreach people get really excited seeing an image immediately and then seeing it build over time as we are discussing the object.

 

Best,

Hiten
 


  • Ptarmigan, CharlesC, saguaro and 2 others like this

#63 tmaestro

tmaestro

    Messenger

  • *****
  • Posts: 433
  • Joined: 22 Jul 2015
  • Loc: West of Houston, Texas

Posted 26 February 2019 - 01:00 PM

The purpose of this thread is to clarify the effectiveness of the new generation of CMOS cameras as outreach tools. The main issue is how long it takes to collect a usable image of moderately bright DSO's. I have seen enough examples of fairly short exposure images to be reasonably confident. Still, most of the posted images are very long, too long for outreach....at least my version. I'm guessing that most of the exposure time of those long exposures is adding icing to the cake. But I want to be sure.

 

For me settling evidence would be an image of M51 with the shape being easily recognizable at less than 30 seconds and substantially refined with continued exposure. The rest of the few dozen objects that I use regularly are easier.

 

I suspect that the use of live observing will continue to grow in outreach programs. Settling this issue is important to the outreach community. 

 

Bill

Here's another video from Astrojedi that illustrates what I hope to do given the opportunity (and more experience with the equipment).  It shows a C8 at f/2 with an ASI224MC at 400 gain, slewing around the light polluted sky and stopping on DSO after DSO that are immediately visible without stacking.

 

https://www.youtube....h?v=iTgVT_WGThM



#64 Howie1

Howie1

    Mariner 2

  • *****
  • Posts: 261
  • Joined: 22 May 2013

Posted 26 February 2019 - 08:26 PM

Sorry late to this thread. I do a lot of outreach as well and this is a relevant question.

 

I will raise you and ask you what you can do in 1 second.... smile.gif

 

https://m.youtube.co...h?v=iTgVT_WGThM

Doh ... just sold my 224 and Rokinon 135mm f/2 lens. When the bad weather clears here I'll have to try 1 sec with my other 224 based cam and mallincam MFR5 reducer nosepiece and see what I can get. Agree ... having done outreach (and for my own personal taste 'observing' with usually single 30 sec frames) .... short times rule. 

 

Top vid Jedi. waytogo.gif


  • Astrojedi likes this

#65 will w

will w

    Apollo

  • *****
  • Posts: 1280
  • Joined: 13 Aug 2006
  • Loc: oxford,ms

Posted 26 February 2019 - 09:33 PM

I do not see very much from any of these videos as for 1 or 2 seconds goes. All i see is if you stack enough frames you will get more detail. All that comes down too speed verses resolution. Wich one do you want to have..Will w


Edited by will w, 27 February 2019 - 09:00 AM.


#66 Astrojedi

Astrojedi

    Gemini

  • *****
  • Posts: 3447
  • Joined: 27 May 2015
  • Loc: SoCal

Posted 27 February 2019 - 11:07 AM

Doh ... just sold my 224 and Rokinon 135mm f/2 lens. When the bad weather clears here I'll have to try 1 sec with my other 224 based cam and mallincam MFR5 reducer nosepiece and see what I can get. Agree ... having done outreach (and for my own personal taste 'observing' with usually single 30 sec frames) .... short times rule. 

 

Top vid Jedi. waytogo.gif

Thanks Howie. Love how the new tech is changing the game.

 

On a side note... inspired by you I got a DSLR again. Reminded of my early days of imaging. Really enjoying the big sensor views.


  • Howie1 likes this

#67 DSO_Viewer

DSO_Viewer

    Viking 1

  • -----
  • Posts: 778
  • Joined: 03 Jan 2016

Posted 27 February 2019 - 12:14 PM

I do not see very much from any of these videos as for 1 or 2 seconds goes. All i see is if you stack enough frames you will get more detail. All that comes down too speed verses resolution. Wich one do you want to have..Will w

What???

 

Steve



#68 will w

will w

    Apollo

  • *****
  • Posts: 1280
  • Joined: 13 Aug 2006
  • Loc: oxford,ms

Posted 27 February 2019 - 11:25 PM

Steve , popcorn.gif   will w



#69 Dwight J

Dwight J

    Gemini

  • *****
  • Posts: 3198
  • Joined: 14 May 2009
  • Loc: Lethbridge, Alberta, Canada

Posted 28 February 2019 - 12:10 AM

A8F629AD-B9F3-4BEE-BA5C-D05A1B9C3E58.jpeg

 

Here is a 14 sec. frame grab from a recorded DVD I made using a C14 at F2.8 and a Mallincam Extreme.  The “live” image was amazing which this just hints at.  


  • Starman27, will w, CharlesC and 2 others like this

#70 Noah4x4

Noah4x4

    Vanguard

  • *****
  • Posts: 2309
  • Joined: 07 Apr 2016
  • Loc: Colchester UK

Posted 28 February 2019 - 02:25 AM

The fact is that after however long it takes me to achieve focus, using my Atik Horizon on Hyperstar I can then GoTo a NEW DSO target  and see at least the clear outline of most inside three stacked frames not exceeding 10 seconds each. Bright Objects like the Orion Nebula or Hercules Cluster will look genuinely impressive inside 30 seconds. Yet, whilst I can make out the outline of the Horsehead or M51 in 30 seconds, it takes a little longer to develop the view I desire. F/2 will speed up photo capture, but results using CCD or CMOS can never be instant and a few stacked frames will normally be desirable.


  • will w, CharlesC, bsavoie and 1 other like this


CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.


Recent Topics






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics