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

How seriously to take sampling rates ?

  • Please log in to reply
3 replies to this topic

#1 gazerjim

gazerjim

    Cosmos

  • *****
  • topic starter
  • Posts: 8370
  • Joined: 12 Feb 2004
  • Loc: n-dimensional space

Posted 25 June 2018 - 01:12 AM

Like anyone afflicted with the disease of astro imaging, that next upgrade to [fill-in-the-blank] is always in the works.  As of now there are two within possible reach for me--a 6 inch imaging newt, and a more capable camera than my ASI 224.  Although the 224 is a great performer for the money.

 

So I am pouring over the specs for various cameras,  debating how much camera I can afford that would work well with both my 72EDII and a scope in the 6 inch range.  I have plugged the values for numerous cameras into the sampling calculator,  and it looks like a pixel size in the 3-4 range is theoretically optimum.

 

But how much leeway is there for nice sharp, high dynamic range imaging ? .(the kind I hope to to someday)  I have seen  pics on the internet taken with combinations in which the image is both under and over sampled (usually the former, it seems) that look fantastic.

 

My mouse cursor keeps hovering around the ASI 178 (to cool or not to cool ? Summer nights are warm here.)  Although I'm wondering if its extremely small pixels (2.4 micro-M) might pose a particular downside?  Do smaller pixels generally exhibit more noise (thermal or otherwise) ?  Is well depth related to pixel size and usable dynamic range ? 

 

Comparing camera specs can cause  dizziness !  



#2 NaNuu

NaNuu

    Mariner 2

  • -----
  • Posts: 220
  • Joined: 14 Apr 2017
  • Loc: Germany

Posted 25 June 2018 - 02:28 AM

Well, I use similar scopes as you do (or plan to) and I do own the ASI 224 as well as the ASI 178 (both mc, both uncooled) - While I do like the somewhat larger fov and the more pixels of the ASI 178, it's more complicated then the ASI 224: i.e. if you put the gain a bit higher (which you want to do, as the sensitivity is significantly less then with the 224), playing with the histogram to show fainter nebulae often brings in some red and blue stripes. You will need more integration time to get similar results as with the 224. There is some more noise as with the 224, too - but this is manageable (i.e. using darks). The smaller pixels may one of the reasons why that sensor is less sensitive. I can't tell wether cooling would change a lot - it will be helpful if you image during warm nights...

 

I don't say this is a bad cam, but I myself did need quite some nights to understand it and it's not as easy going as the 224. It's definitively great for solar/lunar stuff, though! And once you understood the differences of the 178 compared to the 224, you will have fun with it. Yet, whenever I decide to take the 224, I am taken by it's increased sensitivity, especially for the fainter stuff.

 

I myself am thinking about a true step up cam wise wrt eaa: the ASI 294 pro (well, it's quite a bit more money...). much bigger fov and lots of good results here show, that this might be the direction to go if I get another cam.


Edited by NaNuu, 25 June 2018 - 02:29 AM.


#3 gazerjim

gazerjim

    Cosmos

  • *****
  • topic starter
  • Posts: 8370
  • Joined: 12 Feb 2004
  • Loc: n-dimensional space

Posted 25 June 2018 - 12:30 PM

 

 

I don't say this is a bad cam, but I myself did need quite some nights to understand it and it's not as easy going as the 224. It's definitively great for solar/lunar stuff, though! And once you understood the differences of the 178 compared to the 224, you will have fun with it. Yet, whenever I decide to take the 224, I am taken by it's increased sensitivity, especially for the fainter stuff.

 

I myself am thinking about a true step up cam wise wrt eaa: the ASI 294 pro (well, it's quite a bit more money...). much bigger fov and lots of good results here show, that this might be the direction to go if I get another cam.

Interesting, and why I hang out here and read testimonials and compare pics taken with various setups.    "The proof is in the pudding", as the saying goes and the most popular cameras tend to be popular for good reasons. 

Have come to the conclusion that I simply do not know enough to choose based solely on technical specifications. 



#4 NaNuu

NaNuu

    Mariner 2

  • -----
  • Posts: 220
  • Joined: 14 Apr 2017
  • Loc: Germany

Posted 26 June 2018 - 05:02 AM

That's more or less my own way - specs are good for specialists and technicians, but being a poor mathematician, I can't translate specs to performance. So I check what experience others have (and I don't buy very new, very fancy and cool stuff - I might run in troubles). I don't need the best ever combo, but a good one. For that, results shown on this forum are a good way to find my own decision. (-;




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