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

magnitude limit with Esprit 100 f5.5 vs 8" Rasa given a OSC CMOS

  • Please log in to reply
3 replies to this topic

#1 Geneszy

Geneszy

    Lift Off

  • -----
  • topic starter
  • Posts: 23
  • Joined: 12 Apr 2015

Posted 14 July 2019 - 08:46 AM

Just looking to determine a rough estimate on mag limits given the same camera setup on both the Esprit 100 f5.5 and 8" Rasa. I know the Rasa is way faster but can I reach the same magnitudes with the Esprit with enough exposure time or is this a limit since it is a 100mm vs the 203mm?



#2 bobzeq25

bobzeq25

    Hubble

  • *****
  • Posts: 16931
  • Joined: 27 Oct 2014

Posted 14 July 2019 - 09:47 AM

I have the C8 RASA and a 100mm F5.8 (SVQ100).

 

AP is peculiar.  Given enough time, the 100mm can reach the same magnitude.  The reason lies in how different the camera is than your eyes.  It can sit there patiently accumulating data.  Provided you do some things like keeping it pointed at a moving target very precisely.  <smile>

 

The magnitude limit you can reach is, however, affected by your skies, the light pollution level.  AP is often extremely complex, and it can be hard to include all the relevant factors in any theoretical analysis.  Often, theoretical analyses here are completely driven by what factors are included, and what is ignored.  The results may be as theoretical as the analysis.  <smile>

 

Bottom line.  I got the C8 RASA so I could do better images in my light polluted skies.  "Better" includes better signal to noise ratio, and I can get that much faster with the RASA.  That works.


  • elmiko likes this

#3 Geneszy

Geneszy

    Lift Off

  • -----
  • topic starter
  • Posts: 23
  • Joined: 12 Apr 2015

Posted 14 July 2019 - 09:59 AM

I have the C8 RASA and a 100mm F5.8 (SVQ100).

 

AP is peculiar.  Given enough time, the 100mm can reach the same magnitude.  The reason lies in how different the camera is than your eyes.  It can sit there patiently accumulating data.  Provided you do some things like keeping it pointed at a moving target very precisely.  <smile>

 

The magnitude limit you can reach is, however, affected by your skies, the light pollution level.  AP is often extremely complex, and it can be hard to include all the relevant factors in any theoretical analysis.  Often, theoretical analyses here are completely driven by what factors are included, and what is ignored.  The results may be as theoretical as the analysis.  <smile>

 

Bottom line.  I got the C8 RASA so I could do better images in my light polluted skies.  "Better" includes better signal to noise ratio, and I can get that much faster with the RASA.  That works.

Makes sense....thanks for the easy to understand explanation. I a just outside the city of Columbia SC so skies are not so great. Humidity and I say moderate light pollution are an issue especially in the summer with the moisture in the sky. 



#4 Stephen Kennedy

Stephen Kennedy

    Surveyor 1

  • *****
  • Posts: 1844
  • Joined: 03 Jul 2014
  • Loc: California

Posted 14 July 2019 - 09:28 PM

It is true up to a point that in the Magnitude limit you can reach that longer exposure time can compensate for smaller aperture.  However I do not think that even under the darkest skies and the longest time my 210 mm Newtonian would ever reach the magnitudes that the 8.4 meter Subaru Telescope on Moana Kea that I took a tour of a few years ago regularly reaches.  The Sun would rise the next morning before I could get to 26th magnitude with a camera.  The RASA has twice the aperture and therefore four times the light gathering power of the Esprit and that will dictate limits that can be reached and exposure times.




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