View Single Post
  #6  
Old 29-04-2015, 06:07 PM
Slawomir's Avatar
Slawomir (Suavi)
Registered User

Slawomir is offline
 
Join Date: Sep 2014
Location: North Queensland
Posts: 3,230
Thank you very much gentlemen for your feedback, replies and questions. I will do my best to answer questions as accurately as possible.
Quote:
Originally Posted by Amaranthus
I find I get marginal additional cooling on my QHY22 with 100% vs 75% cooling. Maybe 5C lower if it is a warm night, and 2C lower on a cold night. So I typically run my cooler at 75% as an optimum. On 5C nights here in Tassie, I typically cool the QHY22 to between -35C and -40C. Dark current is then virtually non-existent.

The cooler runs at 65-67% to cool the camera about 35C below ambient temperature(25C to -10C). I got it down to -20C (about 45C below ambient) and the cooler from memory was at about 80%. Yet there was literally no difference in the dark current between -10C and -20C, thus I run the camera at -10C and let the cooler and fans work at ease (below 70%).


Quote:
Originally Posted by lazjen
If I'm reading the article correctly, he's getting the temps down to -10C from 25C+, so at at least a 35C below ambient temp. That doesn't sound too bad?

Yes Chris, you are correct. 35C below ambient with the cooler running at 65-67% of power does not sound too bad.
Quote:
Originally Posted by gregbradley
Good review Slawomir.

I am surprised the well depth is 23K at low gain. Can you change the gain on these QSI cameras in software?


Yes, with on click of a button in Nebulosity. QSI recommends low gain when binning at 2x2 or higher, since then you physically increase the surface area of each (combined) pixel and thus space for holding electrons.
Quote:
Originally Posted by gregbradley
The read noise is really low, that's great.

If you are not subtracting darks wouldn't it be better to simply use the cooler at 100%?

The theory of not using 100% cooling I thought was to keep the temperature regulated to match darks.


There is virtually no difference in dark current between the camera running at -10C and -20C, thus I prefer the fans and cooler to run at ease with less than 70% of its capacity. Maybe I am na´ve, but I like to think that equipment usually lasts longer when not running all the time at 100%...
Quote:
Originally Posted by gregbradley
Its lucky I suppose that the camera is clean early as -10C is kind of weak cooling for a CCD. I guess I am used to FLI where -35C becomes usual but then the Starlight Expres Trius 694 cools to 45C below ambient (slightly optimistic in my use, more like 40-42C reliably).

25C to -10C gives 35C difference with the cooler running at less than 70%. To achieve 45C below ambient (from 25C to -20C) the cooler was running from memory at about 80%. - I will test how low I can get with the cooler running at 100% and will place the result in here.
Quote:
Originally Posted by gregbradley
Can you say more about the filter wheel and OAG? Is it hard to focus the OAG?

One issue I have with cameras in general is I get tired of connectivity issues when you have multiple components. It started in my SBIG days where the camera would take 10 seconds to connect as it downloaded the driver every time you started it up. I take it QSI is the same as FLI, Apogee and SX in this regard that the driver is in the on board memory of the camera? I like instant connection as I used to hate waiting 10 seconds and then it often fail and then chase down why. 10 seconds sounds stupid but its these little lags that can be irritating operating electronics.

Having a combined filter wheel and OAG in one package that connects as a unit with one click is very appealing. Its just 2 things that are no longer likely to cause you a problem (filter wheel and OAG).

I wish FLI integrated a filter wheel and OAG. Its the idea started with the SBIG STL that was so useful and convenient.)


The camera connects right away - I use Nebulosity and choose QSI 500/600 from the camera menu.
I am using an external filter wheel (Orion Nautilus) and TS OAG and they are connect with T-threads. Honestly, now I wish I have gotten the WSG version instead of the slim one as it is a really nice package - but there is always room in my house for another camera in the future... :-)

Quote:
Originally Posted by gregbradley
I notice QSI images are often very good. Its hard to pick one over the other with the QSI 683 Wsg 8 being so popular. I think the usual reason for chosing that over the 690 or 660 is the wider field of view.

QSI though have had some quality issues. Over at the QSI Yahoo Group there have been multiple posts about filter wheel going out of alignment, or amp glows on the 683 or artifacts. Is Kevin still running the show there or is he out? It seemed like he was the guy and if he isn't there anymore can the new guys do as good a job as he does?

Greg.


I really cannot comment on the issues. All I can say is that QSI 690 was a substantial step up for me from my previous camera - in particular in terms of powerful cooling and build quality. The overall impression is that the guys at QSI really took time to design this camera.

Yes, there is very minor amp glow that I noticed in dark frames after heavily stretching them - but I really tried hard to see this amp glow in my light subs and even have measured them and could not see any effects of amp glow. I have seen darks and bias frames form other cameras that implemented 8300 chip and they did not look nearly as clean and even as the ones from Sony's sensor.

I hope my replies have helped to clarify a few things

Muchos Nachos
Slawomir

Last edited by Slawomir; 29-04-2015 at 07:41 PM.
Reply With Quote