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Old 13-04-2008, 06:51 PM
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QHY8 or modded 40d?

OK everyone,

I'd like to get a new camera, exclusively for astro imaging. My field time is limited, and my skies not totally black, so a single shot colour camera would seem to be the best option for now.
In my price range are a modded 40d http://www.sciencecenter.net/hutech/canon/index.htm
a QHY8 cooled ccd. http://qhyccd.com/QHY8.html
The QHY8 has almost no dark noise and good spectral response, but it uses a lot of power, 12V at 4A means I'll need a car battery to run the set-up when I'm away from mains power.
The 40d with a Hutech or Baader mod is practical too, the images on these forums speak for themselves, but the cooled ccd should have better signal to noise.

I've seen a few discussions on IIS about the merits of CCD vs DSLR, but I can't find much on the QHY8, which would seem to be the best alternative to a DSLR. (A DSLR killer??)

There is a wealth of experience on IIS. Please, let's start a bit of a discussion about the QHY8 vs the modded 40d, post some images, talk about the pros and cons of each. It could be interesting...

Cheers,

Rob

Last edited by Astrod00d; 13-04-2008 at 07:11 PM.
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Old 13-04-2008, 07:42 PM
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well my Qhy8 arrived last week----notice the thunderstorms around Sydney? eventually i will be able to provide you you with one side of the story at least -hopefully
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Old 13-04-2008, 07:42 PM
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oh for images the qhy forum is the place to go
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Old 13-04-2008, 08:00 PM
Hagar (Doug)
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Qhy8

Just got mine also. Hopefully will have some images soon.
Check out QHY forum
http://www.qhyccd.com/ccdbbs/
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Old 14-04-2008, 08:41 AM
Alchemy (Clive)
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An isssue id very much like to see covered but with the added cooling as if youre going to that level for the extra its going to be worth it, the standard modded 40d might go say 10 mins exposure whereas the cooled could extend way beyond that.

So far ken G, Hagar and seeker372011 have got one that i know of, and on the other side for the cooled camera its h0ughy that owns one (350d)

Ive been impressed by the results with h0ughys camera, particularly the Ha response (see photon collectors cg4 image) the 40d can only be better.

on the q8 forum/images im impressed with the ability to go 20 min exposures.

there does not seem to be a real comparison just yet as i really dont think m42 or m8 is a worthwhile comparitive study, some more challenging objects need to be displayed, and then of couse the processing skills of the imager will also play a part.

The 40 d has 10+ megapixels , the q8 has about 6, whether the extra pixels can be utilised in anything other than widefield is debateable.

icing up would be an issue id like to know about, the q8 is pretty much sealed i dont know for the 40d that issue.

the weight factor of a modded 40d vs q8 would have the 40d weighing in way over the q8 i expect. which is an issue with less than solid focusers.

i would like to know about the image format and software for the q8 as the cannon has a solid package that is easy to use.


Just my musings at the moment, im leaning evr so slightly towards the q8 at the moment.

clive.
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Old 14-04-2008, 09:00 AM
Zuts
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Hi,

The QHY8 is cooled but it is not regulated cooling. Once you turn on the cooling the camera will get as cold as possible but it will vary with ambient. Therefore like a DSLR you probably need to take darks as part of the nights imaging, unlike a regulated setup where you dial in the temp and can take the darks anytime. People say you dont need to take darks with a QHY8 but i dont quite understand this as there are other types of noise apart from just hot pixels.

Additionally the cost of a 40D plus mod plus cooling is more expensive than a QHY8 and in some cases is approaching that of dedicated second hand astro cameras SBIG etc. I would probably go the dedicated astro camera route if it was my choice and get the QHY8 even though the cooling is not regulated.

If you are talking about spending over 3 grand landed on a modded, cooled 40D which wont be any use for daylight the lighter dedicated QHY8 starts to look much more appealing.

Just my 2 cents

Paul
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Old 14-04-2008, 10:23 AM
Alchemy (Clive)
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Quote:
Originally Posted by Zuts View Post
Hi,

The QHY8 is cooled but it is not regulated cooling. Once you turn on the cooling the camera will get as cold as possible but it will vary with ambient. Therefore like a DSLR you probably need to take darks as part of the nights imaging, unlike a regulated setup where you dial in the temp and can take the darks anytime. People say you dont need to take darks with a QHY8 but i dont quite understand this as there are other types of noise apart from just hot pixels.
Paul
ive seen the same comments about no darks, not having any experience with cooled cameras my thinking is this, at cool (maybee -20 deg) the noise level is minimal, and the difference between -20 deg and -16 deg for noise is much less than say 20 deg and 16 deg.... hope that makes some sense.

it might be possible to take a series of darks and use for most of the cool temps with reasonable results ?????

the noise of my 300d although a basic modded job, above 20 deg c is objectionable to the point i dont bother anymore, as i know i can do better another day.

interested in other peoples thoughts
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Old 14-04-2008, 10:48 AM
Alchemy (Clive)
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another question, what is the wait time for purchasing the q8
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Old 14-04-2008, 12:25 PM
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[1ponders] (Paul)
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I've often seen this comment about no darks (and not just in this thread) and I just don't understand it. If observatories that cool their cameras to -100 deg need to take darks what makes others feel they don't? Taking darks is an important part of the callibration process. They don't just remove the repeatable noise, but also hot pixels, bias charge, shot noise etc.
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Old 14-04-2008, 12:40 PM
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RB (Andrew)
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Quote:
Originally Posted by [1ponders] View Post
I've often seen this comment about no darks (and not just in this thread) and I just don't understand it. Taking darks is an important part of the callibration process. They don't just remove the repeatable noise, but also hot pixels, bias charge, shot noise etc.
I've often said this as well.
It is important to do darks (as well as flats for that matter), unless you're really pressed for time.
Applying darks does improve the quality of the outcome whether it's a cooled cam or no.
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Old 14-04-2008, 06:13 PM
Alchemy (Clive)
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I've often said this as well.
It is important to do darks (as well as flats for that matter), unless you're really pressed for time.
Applying darks does improve the quality of the outcome whether it's a cooled cam or no.
makes sense, darks are easily enough done so not a big deal,

going to keep this thread active as this is a subject i really want covered.

earlier questions about software, icing up, not yet answered

i have been perusing images from this camera (q8) this afternoon and it is now probably exactly the camera i need, so dont be shy and speak up with opinions.
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Old 14-04-2008, 06:45 PM
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Sorry for taking too long to respond guys, but i had many other things to do..
Anyway, lets start with the "No Draks required". Well, thats about right for most images you will be doing.

Why, because as some of you had said, NOISE (Or lack of it). Noise is not just a slight difference in background. Its can be a MASSIVE difference. For those with a slow internet, i suggest you just look at the thumb nails at my site that compares a 10 minute dark frame from a QHY-8 and an image from the SBIG STL-11000M http://web.aanet.com.au/gama/qe.html .

For those that have high speed, then compare them here for the QHY-8 http://web.aanet.com.au/gama/images/...me600-QHY8.jpg and then the SBIG here http://web.aanet.com.au/gama/images/...2030%20sec.jpg .

This is why you need to take dark frames with the Kodak sensors. Thats not a starfield there boys.. Its noise, and it changes with temperature. This is why you need to match the exact temp when doing imaging with your exposures. So if you want a 2 minute image, you need to take a 2 minute dark. You want to image 3 minutes now ?, well, you need to re do a dark frame for the 3 minute frame. Because the QHY-8 has peanut shells worth of noise, it doesnt need to be set at exactly the same temp. Even if you have a temp difference of 10 or 20 degrees, its still never going to produce the noise the Kodak chips produce.
So this is why you dont need to regulate these Sony sensor cameras QHY, and in fact the Starlight Xpress cameras are also designed this way as well (Sony ccd chips).
Imagine just turning on the camera, leaving it cool down while you setup your scope, then attach and start imaging. No darks !, just dial in 1, 2 , 5, 10 minute exposures, and change the exposure the next frame, no need to do darks again for the different exposure.
Of course people that want to frame their work, or are perfectionists, then they would take a dark frame, but even so, the noise is not at the same levels produced by the Kodak sensors. In fact, you could count the pixels on one hand that have saturated. Sony are very stringent on dead pixels, and pixels that saturate withing a given time. There is more detail in terms of noise, but that is a few chapters in themselves.

Availability is high globally, and can take time to deliver. I do get large orders of them. They dont last long, word gets around pretty fast, and many dont believe the "No Dark Frames required" that many say. But its true !.

If there is any more info you need let me know guys.

Theo.
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Old 14-04-2008, 06:54 PM
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Wow Theo, our posts crossed! I'll edit mine a bit!

Yes, with the QHY8 I think I would take a few master darks. Why short-cut things after spending $2440 on a camera, I'd want the best results possible.

True, the QHY8 does not have regulated cooling. How important is regulated cooling, and I wonder if regulation could be added later? Theo-The noise is so low anyway that regulation is not really important.

What capture software would one use with a QHY8, and what would it cost?

Centralads have the cooled astro 400d for USD2150 including shipping. We'd still have to pay duty/GST on arrival in Australia, so the QHY8 costs less.

Is condensation an issue with a cooled DSLR? Houghy?

So many things to consider!

Cheers,

Rob
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Old 14-04-2008, 07:09 PM
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You guys arent doing much looking, and really should. If you guys did, then you would have found out that the QHY-8 comes with Maxim DL, Astroart, CCDsoft, Video capture and streaming, and Linux drivers. We couldnt get the kitchen sink in there. We hope to on the next version !.

As for Icing Up, its not ice. The camera attached to a scope will not produce any problems. What can occur depending on humidity and ambient temp, is when you place a reducer and filter with a spacer and mount it to to camera, the the air inside the spacer is now sealed. What happens now is the very cold sealed chamber of the CCD, will of course attract the warmer air inside the sealed spacer, and thus will dew a tiny spot on the outside of the chamber. This has occured to some people around the world. Some place a small dew heater around the spacer when they need to use a reduer or have high humidity.
But if procedure is followed and the items are placed inside a sealed box and the desicant is applied to them (Including the reducer and spacer) it will dry the air and prevent this happening.
Others just reduce the current to the peltier cooling and this also prevents any dewing within the spacer/reducer.
But the camera on its own attached to the scope will NOT dew, as the air is circulated within a larger area as apposed to a small air trap caused by sealing the air with an external filter or reducer.

Theo.
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Old 14-04-2008, 07:20 PM
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Well Rob, Regulation of the temperature is extremmly important when using the Kodak chips.
Why so ?, well, that image you see that i have linked has a specific pattern. The pattern changes with temperature, and shows less and less as you decrease temperature. So the noise is sort of producable again by apllying the same temperature, you can again show basically the exact same noise pattern. So if you image with a temp of say 5 minutes, then not only would you have imaged the sky for 5 minutes, but also the noise generated by 5 minutes. So by taking another exposure for the same time at the same temperature, you could remove this noise away from your image. So what is left is just your exposre more or less..

Because the noise pattern is really not evidant, and cant really see it unless you do extreme detail work, you wouldnt need to take dark frames.

Oh yeah, there have been some bananas, and you know who you guys are !!, have been removing the sealing filter/nosepiece while power is applied to the camera, and of course the camera dews up in a micro second.. When i asked why they did that, they mostly said, to clean the "DUST" !!. Gees.

Theo.
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Old 14-04-2008, 07:51 PM
Alchemy (Clive)
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i spent some time today looking at images produced by the q8 and can say im impressed, thanks for answering the questions, one more... the output of the camera is it a raw a fits or what ? your website says 16 bit, forgive me if you think i havent done the research..... this is the research
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Old 14-04-2008, 08:18 PM
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Hi Rob,

Had a run with a friends QHY8 at SPSP (see achromat image on chinese mount post on deep sky part of forum). It did drain the battery but boy was it good! They are very low noise.

A few points in discussion with Ken the owner
- you need to add in the cost of 12V power supply with the digital camera (they dont go long on batteries) and possibly a baader mod (close to same price?)
- no dark frames so more time to image.
Although I guess you may want to factor in a heavy duty battery!

I was very impressed but may end up going down a 450D/?40D path as our digital camera is on the way out anyway (but probably wont go the mod).
If I wasnt Id be pretty happy with a QHY8. Of course you keep seeing great results with the 40Ds too.

Cheers
David
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Old 14-04-2008, 08:20 PM
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Why do you need a baader mod on the QHY8? it's already allowing in h-a, right?

No dark frames is a big plus!

Watching this thread with interest..
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Old 14-04-2008, 08:27 PM
Alchemy (Clive)
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Why do you need a baader mod on the QHY8? it's already allowing in h-a, right?

No dark frames is a big plus!

Watching this thread with interest..
efficiency up to 660nm is good, see gamas links below

cant see why you would build a dedicated camera for imaging that blocks Ha that would be silly to say the least. the images ive seen dont indicate any issue in that dept.... ha is somewhere around 620nm yeah?
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Old 14-04-2008, 08:30 PM
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I think he may be speaking about Narrow band work, im not sure.
The camera comes with either clear or a UVIR block, or both..
But many are using H.a only, etc..
As for power drainage, like i said, you can limit the current by either getting the DC-102 which will regulate the voltage via PWM to the Peltier, or just get a simple current regulator and run it in series to the peltier.
But gees, i think you will find the big cameras will chew power when its a dual stage cooling setup like the QHY-8.

Rob, the image is what ever software your using. It is a Raw image, and i use FIT in Maxim, then i either save the file or play around with it. You can even download it in BMP if you wanted..

Theo
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