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Old 09-01-2013, 11:53 AM
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Andy01 (Andy)
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DSLR, OSC or Mono CCD?

Hi everyone,

Can I ask for advice/opinions on the best next step in my imaging journey?

I have been imaging for a while with an unmodded DSLR, and would like to image DSO's and get more data and info in the IR and possibly other spectrums, and drive the camera from the laptop.

I have a 120 ED refractor on an EQ6, and an orion mini guider package.

Options are ...

A) mod my DSLR or purchase a modded one, or
B) step up to a cooled OSC CCD like a QHY8 or QHY8L or similar, or
C) invest heavily in a mono camera, (a steep learning curve).

I live in the Melbourne suburbs so light pollution is an issue, and I have 3 small children who go to bed at 9, so I'm pushed for time most nights!

I use a mac - Nebulosity, PHD, Stellarium and EQMac all work ok.

Thoughts?

Cheers

Andy
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Old 09-01-2013, 12:53 PM
Poita (Peter)
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I personally wouldn't bother with the modded dslr, a cooled CCD makes more sense really.

As for colour vs mono, I can loan you a mono SBIG camera and filters etc if you want to see if mono is your bag.
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Old 09-01-2013, 12:57 PM
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jjjnettie (Jeanette)
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I personally went for a cooled and modded DSLR as I already know how to use one.
But.... there is a QHY8 for sale right now.
http://www.iceinspace.com.au/forum/s...d.php?t=101560
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Old 09-01-2013, 01:45 PM
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I would suggest a cooled CCD as well.
I started off with a DSLR and still use it sometimes, but I much prefer my OSC CCD, I find that there is more to play with in an image in terms of processing and the low noise also helps in processing.

There are people who've taken some really nice images with cooled dslr's. although the difference in the dynamic range between 12bit and 16bit is debatable, a cooled ccd does make sense, you don't have to worry about ISO, just exposure length.
you have to get your head around the concept of stretched vs unstretched images but its not hard.
narrowband will require much longer exposures with an OSC, but can be done.
I went with an OSC because I could image 3 or 4 targets in one night, whereas with a mono, it'd take 4 times as long, albeit with better results.
with temperature measurement and regulation, in theory, you should be able to take your darks at home.
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Old 09-01-2013, 02:02 PM
Poita (Peter)
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A cooled and modded DSLR isn't a bad option, it has the advantages of not having to have the computer tethered to take images.
However you will usually be guiding anyway, so there is often a computer hooked up.

The downside to me with the cooled DSLR route is the clunkyness and the cost.

It is fairly pricey to get a modded and cooled DSLR, and the temps won't usually get down as low as a cooled CCD camera.

For not much more you could get a QHY8 or similar camera with a Sony chip that doesn't really require darks, has solid cooling and great Ha sensitivity.
The QHY8L requires darks, or long bias frames as it is an interlaced chip you get some amp glow in one corner due to the way it reads the image out.
I'd go for the QHY8 Pro instead if you need the 'coke can' style casing.

Run nebulosity on your Mac and the drivers are built in for the QHY8, as are most of the tools to do image acquisition, stacking, stretching etc.

It is an easy path to take, will set you back between $800-$1000 for the camera, and will work with the Mac beautifully.
If you don't like it, the resale value is pretty close to what you would pay for it, so there is probably only $50-$100 risk in buying one to see if it suits you.

That pretty much holds for any 2nd hand Astro CCD, if you choose wisely the resale price is pretty much what you will pay for it.

[BTW: I sound like an ad, but my camera already has a buyer, so there is no bias ]
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Old 09-01-2013, 02:04 PM
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Screwdriverone (Chris)
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If you are time poor Andy, OSC is the way to go.

For the money, Poita's QHY8 on Ice Trade is an absolute bargain.

6MP, DSLR sized chip (perfect on your ED120), COOLED CCD and as I have personally used this camera (Peter loaned it to me), quite easy to use.

Go for it, it wont last long, or might already be gone....

Otherwise, you could try the last 314E mono that is available at Andrews (I bought it as they thought it was colour ) as it is a very nice mono camera with almost ZERO noise and then later, buy some Ha or OIII, SII filters etc and go nuts from Suburbia. Mono Ha shots are some of the best shots going for night skies that have lots of light pollution.

With the ED120, you wont have any issues with lining up the newt diffraction spikes like I would have if I imaged over a number of nights.

The 314E is only $899 and they have free freight on at the moment. WELL worth it as I personally know how good these cameras are as I bought the 314L+ when I took that 314E back (as it was mono).

Check out some of my latest Deep sky pics for how well the 314L+ performs on my 1000mm FL 8" newtonian. I love it.

Cheers

Chris
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Old 09-01-2013, 02:22 PM
DJT (David)
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Small hijack so apologies but Alistair, I assume that to do narrowband with an OSC I still need a filter wheel and filters? I ask because at the moment I us a HA clip in filter with the DSLR which means I can image well from Light Polluted Sydney so would want to see what could be viable with an OSC. Or is there a screw in HA filter type option that does away with the full FW setup?

Quote:
Originally Posted by alistairsam View Post
I would suggest a cooled CCD as well.
I started off with a DSLR and still use it sometimes, but I much prefer my OSC CCD, I find that there is more to play with in an image in terms of processing and the low noise also helps in processing.

There are people who've taken some really nice images with cooled dslr's. although the difference in the dynamic range between 12bit and 16bit is debatable, a cooled ccd does make sense, you don't have to worry about ISO, just exposure length.
you have to get your head around the concept of stretched vs unstretched images but its not hard.
narrowband will require much longer exposures with an OSC, but can be done.
I went with an OSC because I could image 3 or 4 targets in one night, whereas with a mono, it'd take 4 times as long, albeit with better results.
with temperature measurement and regulation, in theory, you should be able to take your darks at home.
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Old 09-01-2013, 02:50 PM
Poita (Peter)
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Quote:
Originally Posted by DJT View Post
Small hijack so apologies but Alistair, I assume that to do narrowband with an OSC I still need a filter wheel and filters? I ask because at the moment I us a HA clip in filter with the DSLR which means I can image well from Light Polluted Sydney so would want to see what could be viable with an OSC. Or is there a screw in HA filter type option that does away with the full FW setup?
You can either screw on filter on at a time with the OSC or use a filter drawer or filter wheel.
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Old 09-01-2013, 03:05 PM
DJT (David)
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Originally Posted by Poita View Post
You can either screw on filter on at a time with the OSC or use a filter drawer or filter wheel.
aaah..thanks very much
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Old 09-01-2013, 03:55 PM
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As Peter mentioned, you can get the 2" Ha Filters with a thread on them that you either screw onto the end of the UV/IR nosepiece of the QHY8 or the coma corrector if you use one. I use one.
Here's an example
This has the qhy8, uv/ir nosepiece, spacer, coma corrector, and LP filter screwed on. The Ha would screw on similarly. you may not need a coma corrector for your scope though.
http://www.flickr.com/photos/gus_sme...n/photostream/

Have a look at Eric's narrowband images from Sydney with a qhy8. very long integration time (20min subs), but great results
http://ejcruz.smugmug.com/Photograph...haBo3_L-XL.jpg

I'm planning on adding Ha to the QHY8 RGB images, still learning though.
and get an LP filter. I recently got one and was amazed with the difference.
again, you get the 2" threaded filters

without
http://alistairsam.wix.com/astronomy...23nj/image11wt
with
http://alistairsam.wix.com/astronomy...c23nj/image724

edit: the above are unprocessed 60second single frame with the qhy8.

They can be fiddly and sometimes not reliable in terms of drivers or banding or software errors, but once you install them correctly, they work well.
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Old 09-01-2013, 04:27 PM
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Andy01 (Andy)
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Thanks so much for your input everyone, very much appreciated

Consensus is to get the OSC CCD, and I was leaning towards that too.
I'm happy to get a 2nd hand unit, I'm budgeting around a grand.

There's a few options in that range. QSY8, ATIK, SBIG or other?

Cheers

Andy
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Old 10-01-2013, 02:04 PM
LAW (Murphy)
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Am I missing something basic? My 450D is 12 megapixels, and the CCDs are mostly 1.4-2 megapixels. I understand that CCD chips are very different to CMOS chips but how do you compare the specs?

With less pixels do they trade fine detail for light gathering sensitivity?
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Old 10-01-2013, 05:14 PM
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The QHY8 is a 6 megapixel camera, but as you say, it's different.
There's a good review posted here.
http://www.iceinspace.com.au/93-489-0-0-1-0.html?

Cheers Andy
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Old 12-01-2013, 09:32 AM
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wasyoungonce (Brendan)
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Well some food for thought on all this. I see on CN that icodome is now offering "full monochrome sensor replacement" (or should I say implant service) service for some Nikon cameras.

Their initial images look very promising indeed. A bit of wait and see atm.
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Old 12-01-2013, 08:38 PM
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I would advise a mono ccd. Much more flexible if you want to shoot narrowband. As for the advice that a OSC has a time advantage, that's rubbish. A mono will get you more photons than a OSC for a given exposure and better resolution since you are not interpolating missing values not covered by the Bayer matrix. Just do the maths: if you do a one hour exposure with a OSC and then a one hour exposure with a mono R:G:B:L 15:15:15:15 you will get 1.5 times as many photons with the mono as compared with the OSC--the pic has got to have a better SNR, as well as better resolution. The OSC is easier to get your head around, and is cheaper because you don't have to outlay money for filters and a maybe for a filter wheel, but those are about the only advantages I can think of.
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Old 13-01-2013, 12:48 AM
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Quote:
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As for the advice that a OSC has a time advantage, that's rubbish.
I don't think anyone doubts that shooting LRGB mono results in better SNR and resolution given the same total exposure time as a OSC camera.

Rather, with a OSC you have a usable "finished" image as soon as one sub has finished exposing. Further exposures just increase the SNR.

With mono cameras, I believe that many people shoot filters sequentially, e.g. 1 hr of red, 1 hr of lum, 1 hr of blue, 1 hr of green in a single night. If clouds roll in after 1.5 hours, you won't have any finished image at all...

(While you could take one sub of each LRGB filter sequentially to minimise this risk, you'd lose some of the benefits of mono by shooting L and B frames lower in the sky where there's more atmospheric extinction and worse seeing.)
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Old 13-01-2013, 09:29 AM
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Ah yes the old whats better mono or one shot colour CCD argument!!

I've shot extensively with DSLR, modded DSLR (several), one shot colour and several mono cameras.

I would argue the camera that is best is the one that bests suits your intended images, time, budget and mount/scope. A high end heavy mono camera on a scope with a weak focuser is a waste. Same with a poorly tracking mount. You won't get happy results. I thinking its about matching your gear up well.

One shot colour cameras are improving all the time. The ideal ones for some reason do not seem to be on the market yet or the one shot colour crowd have't ordered them specifically or some such. They really need the later developed Kodak True Sense sensors. Why? Because your standard colour is created by a filter matrix of RGGB repeating pattern called a Bayer Matrix. Its in almost all DSLRs and colour chips. Kodak developed a ClearRGB matrix to improve low light performance. Per them this improves low light performance by 2 to 3X. Sensitivity of these chips is only a little bit below a standard mono chip. So you could have the best of both worlds.

Starlight Express, FLI, Apogee may have these. You can specify a sensor with these brands. Starlight would be the cheapest. But all 3 would be out of your $1000 budget though.

Otherwise I would agree that one shot colour is quite limited for DSO in heavy light pollution. Although I think its Allan Gould has posted some high quality images using just that from Brisbane. Judicious use of a light pollution filter is probably a must.

One shot colour because 4 pixels are taken up to make one colour dot in an image are handicapped for narrowband. You can take Ha images with them but with greatly reduced sensitivity as only the red filtered pixels are really contributing to the Ha image so thats 1 in 4. It works out a bit more than that but not much.

With mono on the other hand every pixel counts.
For narrowband work you normally look for a sensor with high QE (quantum efficiency that is the sensitivity of the sensor to light) and low noise. 15 to 20 minutes is a good exposure time so that puts pressure on your tracking and autoguiding. Once you add in filters and a filter wheel $1000 is not enough to get a mono, filter wheel and filters. You would also need some software to process the images.

So one shot colour is still your best bet. Its a lot of fun and you get instant images, less prone to clouds moving in stopping a sequence (you need 4 filtered images to make a colour image from mono usually - LRGB).

I hope this helps. QHY8 is a popular choice and is likely to be in your budget. Theres a QHY14 which has more megapixels that seems nice.

Modded 350Ds are very cheap and a very high performing astrophotography camera as an alternative.

A number are using cooled 40Ds and they seem to shine. A modified Canon 5D would be an awesome alternative. There is always a chance of picking one up on Astromart from time to time.

Greg.
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Old 13-01-2013, 11:43 AM
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I have a QHY8 that I have had for a little while. purchased it her on the forum after my battles with DSLR'S. Best move I ever made. I work for myself so find it difficult to do all nighties to get Lrgb images, so a color CCD was the best option for me. Love my QHY8 and found I was taking images on the first night I used it in Nebulosity. If it ever failed on me I would purchase another in a flash. Sure thier are better and more expensive cameras, but bang for buck you can't go wrong with the QHY8. No noise and small light profile that was great for me on a fork mount LX200..



Mardy
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Old 13-01-2013, 12:34 PM
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Sorry for my noobie questions but what about the 'Monochrome' option on DSLRs for narrowband imaging?

If each pixel picks up a different wavelength then narrowband imaging will not utilize all the pixels, I can understand that much, but does the Monochrome option that most DLSRs have allow the use of all the pixels or does it just artificially assign a greyscale to a colour image?
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Old 13-01-2013, 01:50 PM
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Quote:
Originally Posted by LAW View Post
Sorry for my noobie questions but what about the 'Monochrome' option on DSLRs for narrowband imaging?

If each pixel picks up a different wavelength then narrowband imaging will not utilize all the pixels, I can understand that much, but does the Monochrome option that most DLSRs have allow the use of all the pixels or does it just artificially assign a greyscale to a colour image?
The colour filters are built into the sensor in a DSLR or OSC camera so there's no way to avoid their use. When you produce a black and white image from a DSLR it is, as you suggested, just mapping the colours to grayscale values.
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