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

New plate solver program

astrophotography
  • Please log in to reply
131 replies to this topic

#126 han.k

han.k

    ASTAP Software

  • *****
  • Vendors
  • topic starter
  • Posts: 535
  • Joined: 09 Mar 2015
  • Loc: the Netherlands

Posted 22 January 2021 - 02:47 PM

This evening, I was able to do a field test of the new SQM routine. Unfortunately only a few measurements due to clouds passing by. Higher then SQM 18.4 was not possible due to the shining Moon, but the result is good.

 

Later, just realizing that altitude plays a role. Measurements where done at zenith. At lower altitudes the stars are fainter so probably it is better to talk about relative SQM value. The measurements where done at zenith. so maybe it is a coincidence that the values are so close.

Extinction becomes significant when altitudes are lower than about 45 degrees. At sea level, zenith extinction is 0.28 magnitudes, and at an altitude of 45 degrees it’s 0.40 magnitudes.

SQM measurment with ASTAP.png

In the latest ASTAP version only one SQM value is present based on the background level. The noise measurement has been dropped since it did not perform for OSC raw images. Camera used was the ASI1600MM in bin 2x2. Exposure time adapted from 0.5 second to 30 seconds.

 

Han


Edited by han.k, 23 January 2021 - 01:46 AM.

  • RossW likes this

#127 han.k

han.k

    ASTAP Software

  • *****
  • Vendors
  • topic starter
  • Posts: 535
  • Joined: 09 Mar 2015
  • Loc: the Netherlands

Posted 23 January 2021 - 01:01 PM

For the record: Today I looked more in detail to atmospheric extinction. The likely reason that the Unihedron and ASTAP reported values are very similar and exitinction did not play a role is the fact that the Unihedron calibration is about 0.35 magnitudes corrected. This is equal to the extinction when imaging the zenith:

 

http://www.lightpoll...d/sqmreport.pdf

       

The different zero point is likely due to the fact that the relation has been obtained with outside-the-atmosphere magnitudes V’ and B’. As an example, assuming an extinction of 0.35 mag in V and 0.15 mag in B and replacing V’=V-0.35 and B’=B-0.15, where V and B are the apparent magnitude below the atmosphere, we obtain SQM−V= 0.2(B−V)−0.31 in agreement with my previous results. The zero point of the current SQM calibration made by Unihedron gives SQM≈V’ for stars with B’=V’, above the atmosphere, and consequently the below-the-atmosphere SQM-V correction factor for the alpha Lyrae spectrum come out different from zero. Fig.18 shows that for alpha Lyr is SQM-V=-0.35 mag arcsec−2.

 


  • Sky King likes this

#128 Sky King

Sky King

    Messenger

  • *****
  • Posts: 429
  • Joined: 16 Mar 2017
  • Loc: Arizona

Posted 28 January 2021 - 12:48 AM

Hi, So tonight I tried the ASI174mm with the ZWO 30mm F4 guide scope and ASTAP solved like lightening at 120 focal length! It was even partly cloudy. So if I calibrate the guide scope and the C8 better, I could even move the ASI174mm from the guide scope to the C8 after solving and take my images. Got some interesting super wide images through the ZWO 30F4.

 

 

Attached Thumbnails

  • M31.jpg

Edited by Sky King, 28 January 2021 - 01:30 AM.


#129 mikenoname

mikenoname

    Viking 1

  • *****
  • Posts: 978
  • Joined: 29 Jan 2015
  • Loc: Death Valley Region (Bortle 2 - SQM 21.9+)

Posted 03 February 2021 - 01:15 AM

I will add to my webpage the advice: For small field-of-view you have to expose longer.

 

Well now that I have upgraded to the 183MM from the 178, ASTAP just solves everything without have to do anything. I can leave the exposure at 1 second and gain at 200 and it just solves! With the 178 both the gain and exposures had to be cranked up.

 

Can't stress enough how big a part FOV plays in the operation of ASTAP.



#130 Sky King

Sky King

    Messenger

  • *****
  • Posts: 429
  • Joined: 16 Mar 2017
  • Loc: Arizona

Posted 11 February 2021 - 02:21 PM

So for small chip cameras, besides longer exposures, which hasn't worked very well for me, the guide scope approach worked well, by reducing the focal length a lot. My 80mm Explore Scientific also works well for ASTAP. Could this effect also be achieved with a serious focal reducer like the Meade F/3.3 or the original Optec Reducer NextGEN MAXfield 0.33x SCT? I have both of these and with my C8, that may reduce focal length and increase the chances of ASTAP solving. Also these focal reducers were designed for small chip cameras and create bad vignetting with larger chips like the ASI174mm. So I will give this a try.



#131 mikenoname

mikenoname

    Viking 1

  • *****
  • Posts: 978
  • Joined: 29 Jan 2015
  • Loc: Death Valley Region (Bortle 2 - SQM 21.9+)

Posted 11 February 2021 - 03:12 PM

Life with ASTAP seems to get much easier when you exceed three quarters of a degree for field-of-view, at least in my experience.



#132 han.k

han.k

    ASTAP Software

  • *****
  • Vendors
  • topic starter
  • Posts: 535
  • Joined: 09 Mar 2015
  • Loc: the Netherlands

Posted 22 February 2021 - 11:36 AM

For people having the H17 or H18 star database installed, please upgrade to ASTAP 0.9.500. Older versions have a bug causing the solving to fail for some celestial locations in the command-line mode only.

 

Han




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





Also tagged with one or more of these keywords: astrophotography



Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics