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.


Best Practice imaging with ZWO ASI 533MC under bright skies

  • Please log in to reply
5 replies to this topic

#1 steppen


    Lift Off

  • -----
  • topic starter
  • Posts: 13
  • Joined: 07 Jun 2020

Posted 04 May 2021 - 07:05 PM

Apologies if this has been asked and there's a thread you can refer me to. I am looking for insight on what gain and offset to use with a ZWO ASI 533MC and a couple of filters in Bortle 8 - 9 skies. I read that higher gain 101, for instance, is better to reduce noise. Gain1 is better for higher dynamic range and more depth. Since I am fighting the noise of light pollution, this tells me that the higher gain would be better. But my instinct tells me that less gain should be less noisy. I've used my camera with both settings, and I am not sure I can discern significant difference. Add another variable. A light pollution filter like the idas, or a narrowband like the l-Extreme Pro. I am really curious what the experts think. Thanks!

#2 Dynan


    Fly Me to the Moon

  • *****
  • Vendors
  • Posts: 5,553
  • Joined: 11 Mar 2018
  • Loc: NOLA

Posted 04 May 2021 - 07:21 PM

I probably sound like a broken record for suggesting SharpCap Pro (≈$15/yr...≈3¢/day) but it is a great program for determining a good exposure for any sky/gain.


After you analyze your sensor (only takes a few minutes or use a stock analysis included in SC), you choose what you'd like to use (Unity Gain/ Highest Dynamic Range/etc.) Then you point to an area near your target and it will analyze and suggest the best exposure/gain for a determined amount of time in your session. This would be the TOTAL session (stacking) time you expect to use. The subs may not look the best, but the stack will.


I use it to analyze the sky (I use Unity Gain), see the analysis results, and then choose the closest exposure time for which I have master darks and biases.


SC Pro comes with some other GREAT tools also.

Edited by Dynan, 04 May 2021 - 07:22 PM.

  • barbarosa, austinstephens and steppen like this

#3 barbarosa



  • *****
  • Posts: 2,961
  • Joined: 11 Apr 2010
  • Loc: 139 miles W of the Awahnee Hotel

Posted 04 May 2021 - 07:58 PM

Q1 What he said.




The IDAS LPS filters have a lot of fans.


 I am personally impressed by the by the IDAS NBZ


The L-Enhance is good, the L-Even More also good.wink.gif  


Surprisingly I get some  benefit using a visual sky glow filter, which I believe to be the same as the one sold by Orion.


Edited by barbarosa, 04 May 2021 - 07:59 PM.

#4 kel123


    Surveyor 1

  • -----
  • Posts: 1,528
  • Joined: 11 May 2019

Posted 04 May 2021 - 09:04 PM

As was suggested above, for some targets, I let Sharpcap pro smart histogram choose length of subs for me. I use exactly that same camera with a dual narrowband filter.

However, for some targets, especially the dimmer ones, I just use unity gain and choose the length of my subs, between 120 and 300 seconds.

A part of me rebels against the exposure length recommendations by Sharpcap as they happen to be so awkward with suggestions like 18.5 seconds, 16.5 seconds, 21.7 seconds etc. This makes dark libraries useless. And they also take a lot of space. You may shoot 1000 subs instead of some 10s.
It is as if your EQ mount and guiding equipment are surplus to requirement. So, the recommendations sometimes seem too good to be true to me. Hence, I just do my own thing with my capable camera, mount and guiding equipment by using more conventional settings.

Meanwhile ,get a dual narrowband or the triad if you can afford it. You need one to image a lot of all those emission targets in that kind of light pollution.
For broadband targets like galaxies, star clusters, reflection nebulae and some planetary nebulae , though I use optolong L-pro, some imagers are now doing away with their broadband filters as there are now more capable processing softwares which remove gradients in seconds. Broadband light pollution filters also filters out parts of the details aka signals in your target. I wouldn't be getting any other broadband light pollution filter in the near future.
  • steppen likes this

#5 elmiko


    Fly Me to the Moon

  • *****
  • Posts: 5,794
  • Joined: 27 Jul 2009
  • Loc: Arizona

Posted 04 May 2021 - 10:02 PM

I just got the camera I use 100 gain 20 offset Bortle 8 skies. 120 sec subs.

  • Dynan likes this

#6 Sky King

Sky King


  • *****
  • Posts: 425
  • Joined: 16 Mar 2017
  • Loc: Arizona

Posted 05 May 2021 - 01:26 AM

Here's another discussion on this topic.

  • elmiko likes 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