Why I hate choosing a CCD

[Jutscher]

Hey guys, and :help:

So here is the deal. I decided that I want to move to a dedicated CCD for my imaging needs based on a couple of things... primarily that my current modded 500D that I have been using has plenty of nasty big dust motes that infect every pic that I take (please disregard if you see the same for sale... its fine ;)) and is in need of retirement.

As such, I have been and will continue to use a Takahashi TSA 120 with a FL of 900mm, at F7.5. I enjoy taking sharp, wide field images, but would like to be able to crop these on occasion for smaller objects such as galaxies etc.

I decided that I would put my old practices of impulse buying aside and do some homework to ensure that I got the best CCD to suit my scope and preferred style of imaging.

That said, I have been looking at dedicated CCD's such as SBIG's ST-8 and ATIK's 11000. Both have a 9uM pixel size, which would give me
a pixel angular size of 2.06 arc seconds. The 11000 would give me a much larger FOV (at a price) which could be later cropped. Whereas the ST-8 is far cheaper and comes with a guiding chip (not as important as I already have a guiding setup - it just needs improving/stabilisation)

If we were to assume that good seeing in the outskirts of Perth (sea level and usually hot) was roughly 2.5 arc seconds, then my understanding is that 9uM operating at 2.06 arc seconds would be okay, if sampled 1x1

My concern is, would a 9uM pixel size for this relatively short FL scope be risking unescessary undersampling if conditions allowed (does anyone know the usual seeing for outer un-light polluted WA?).

Am I better off choosing a smaller pixel to ensure that I am covered for that perfect day, and just bin for the majority of poor seeing days?

And just to make things even more complicated, pixel size aside, I would like a camera body that allows decent thermoregulation where darks can be taken in daytime if required, to preserve dark sky for light frames.

Hopefully thanks in advance, but I realise that this is a subject fraught with differing opinions.

Sam

[tlgerdes]

From what I understand, the "goldilocks zone" is between 1-2 arc-sec/pixel. Starting at 2 for 900mm means you wouldnt be doing yourself any favours if you shorten your focal length in the future. I would be shooting for 1.5.

[gregbradley]

My understanding is .66 arc sec/pixel was closer to ideal. Based on Nyquists sampling theory that it takes 3X higher accuracy to gain a decent sample (I may have dumbed that down but that is the basic concept).

So .66 as a target assumes then that .66 x 3 = 2 arc seconds seeing is available.

If your seeing is never that good then you can go for a higher than .66.

But 1.5 arc sec/pixel if that theory is true would mean you are expecting seeing of 4.5 arc seconds which is pretty poor seeing.

So following this idea along then the ideal setup would be in arc seconds/pixel 1/3rd of the best seeing you can expect from your location.

Also another rule is smaller pixel cameras for faster F ratios. I think because of how the above works out for this type of scope.

From what I have seen of images, those who apply the above seem to get very good results so it must be pretty close to being true.

Wodaski has a free CCD calc to make it easy to work this out for your setup and different scopes or cameras.

http://www.newastro.com/book_new/camera_app.php

This is a handy tool.

Greg.

[[1ponders]]

Can't add much more than what Greg has said except to jump up and down and clap Ron's CCD Calculator. Wouldn't be without it.

[Jutscher]

Thanks for the quick replies, and the calc link, a bit easier than plugging the info into SNPP6 for a FOV reference.

So, by applying the star size formula: Star Size = (Seeing * FL)/206265 = Then in average perth skies (lets say 2.5arc seconds)
Star size = (2.5 * 900)/206265 = 0.011mm = 11microns.

My understanding of the Nyquist rule was to 2x sample (correct me if wrong) therefore in seeing of 2.5 arcseconds I would need a pixel size of 5.5microns, pretty close to my current 500D at 4.7microns in terms of ideal sampling.

So I guess, I need to find a CCD with properties similar to my DSLR, weird.

[gregbradley]

I just googled Nyquist rule and its at least 2X. So that would be the minimum in order to reconstruct the signal.

I suppose that is why I have seen it expressed as 3X to allow a margin as 2X is the absolute minimum.

So with that then if you are matching a specific scope you can work it.

Your DSLR is already a bit more than 2X and it seems you are on safe ground there.

KAF8300 chip is 5.7 micron pixels so that would be one choice. That is the chip in the SBIG ST8300, FLI Microline 8300, Apogee U8300,QSI583 and Starlight Express and QHY cameras.

QHY is cheapest, SBIG ST8300 probably next cheapest. Then perhaps Starlight Express then Apogee and then FLI (the best).

Greg.

[Jutscher]

Thanks Greg, that will give me a little bit of reading for the next couple of days :thanx:

Would also be keen to hear from anyone using this scope for imaging, and what decision they made re: CCD.

Cheers

[renormalised]

You can also add the Atik 383L + to that list of cameras that uses the 8300 chip. It's also cheaper than the QHY9 mono....$2599, at Andrews. Atik are very good cameras.

[mill]

Really you have to include a filter wheel and a set of LRGB filters in that price.
Oops it just went way over the price of a QHY9M that will come with filter wheel and LRGB filters and cools to -50 below ambient.

When you start to give information, you should include the missing parts.

You might have forgotten about the filter wheel and filters, if so then i am sorry.

[Rigel003]

I have the FLI ML8300 and have just moved up to a TSA-120 from my FS-102. I'm planning on using it with the TOA35 reducer at F/5.6 most of the time for wide fields. Should be a good match. The cooling and download speed of this camera are great. It can easily get down to -30 degrees C on summer nights.

[renormalised]

You also have to be careful about being condescending, Martin:)

It's being included as part of a package deal. You won't buy a QHY9M for $2000-$2300 (less the price of the FW and filters), more likely $2500-$2800 by itself. So add those costs to your camera if you didn't buy it with the FW and filters originally. They turn out to be roughly the same cost.

It all depends on what FW/Filter combo you purchase as to what the final price will be.

Mind you, the QHY9M combo is a good buy, and the OSC version is a steal!!!:)

[renormalised]

One thing I haven't seen too many of...piccies from the QHY10 and 12. The 12 looks like it could be a good buy for the people wanting a powerful OSC with plenty of pixels that isn't too heavy on the wallet.

[mill]

I am not beeing condescending at all Carl.

The QHY9M has been a package deal from the first day it has been sold and only gone cheaper.
I bought mine when it was $3000 and now it is $2800.
I am starting to think it will be a permanent deal :P

[renormalised]

How reliable, mechanically, is the FW?

[mill]

My filter wheel had only one hickup because the small screw in connection wasn't crimped on properly.
I tighened it and after that it worked perfect till now.

[renormalised]

That's good to hear...that they're reliable.

[ballaratdragons]

From looking at DSO images, lately the QHY range of cameras seem to give a better image, unless it is just coincidence that the fantastic images of late were taken with QHY's?

I know nothing about CCD cameras, I'm just giving my view of one who looks at DSO images a lot.

If that helps at all :shrug:

I know, not a very technical bit of help, is it.

[Jutscher]

yeah, the QHY9 M certainly does appear to be a pretty good in terms of covering the focal requirements of my scope while retaining a reasonable FOV. Equally the price is pretty good especially considering that it includes FW and RGB 2" filters.

Will probably be a hot contender

Addit - The FLI does look pretty sweet, but for the extra cost, I could fit in a set of narrow band filters, which would be a huge addition as I would love to do a little more backyard imaging

[OzRob]

There's a SBIG ST-8300M with FW and filters in the classified section: LINK (http://www.iceinspace.com.au/forum/showthread.php?t=67988)

[Jutscher]

... anyone know of any FLI dealers in Aus, the FLI website gives:
Astro Optical Supplies - http://www.astro-optical.com.au (http://www.astro-optical.com.au/), however I couldnt find any FLI cameras on their site.

The QHY9, although at a pretty good price, does not appear to have the build finish of other cameras of the same chip - images in the manual showed a early oxidisation of the fan plate, and the plugs looked poorly seated - I could be wrong, but why would you put these images in the manual?.

Where as the ATIK does not promise the same level of coolin (40C as compared to 50C) the actual product finish appears a lot tidier. and for a very similar price although I realise that this is minus FW and RGB.

As for the SBIG, I know this is shallow, but I think it kind of looks like a 1980's T.V set. Although I am sure that it is a perfectly capable camera for a good price, I am gonna rule it out on aesthetics.

Thoughts?

[Rigel003]

Might just as well buy FLI gear from OPT or similar US vendor. More cost effective than Astro Optical and more knowledgeable about the products. FLI is very responsive to direct email enquiries too.

[Jutscher]

Yeah, I am just a little unsure re: I know some people have had software issues with the FLI cams - requiring a bit of input from the distributor.
Also, would hate to spend a lot of money sending products back stateside for service/repair in the event that it needed it.

Do you have any images posted of you're FLI/TAK combo?

[Rosebud]

Sam,
I'll toss in another one just to confuse you even more.
Have a look at the Moravian G2-8300 on Steve Massey's site. It has everything that you need plus it has an inbuilt 5 posn filter wheel.

Cheers

[bokglob]

Hi Sam. I've taken a different path, and after seriously considering the 8300 chip, decided to go with the 4022M in a SXVR-H16,in part because I already own a 1.25'' filterwheel and colour and narrowband filters, and also the better well depth and read noise of this chip compared to the 8300, this will allow me extra exposure time before anti-blooming cuts in and reduces sensitivity (good for the faint stuff) I figure. At 7.4um pix size, my general seeing, and the scopes f7.5, the numbers crunch o.k for me, so I'm envious in a way of the large field, but then again,size is'nt everything:rolleyes: Also, between Claude in Aust, and Terry at Starlight Xpress in the U.K I know I'm well looked after in terms of aftersales service and costomer support:thumbsup: Looking forward to seeing the results of whatever you decide upon!

[Jutscher]

Thanks Wally and Darrell, I will check them out.

Got a huge car service/repair bill today, so it's gonna set the final decision back by a few weeks at least.
Good chance to read some more manuals/reviews in the interim tho.
Who knows I may even have a crack at cleaning my DSLR, couldn't make it any worse :bashcomp:

Addit: yeah Darrell, Claude definitely knows his stuff, the only problem I have with ordering equipment from him is that my phone bill skyrockets as it takes at least an hour to get off the phone again - lol

[RobF]

If you're getting serious about it Sam, why not do up a spreadsheet for all the models you're remotely considering - features/spec down left handside, CCDs along the top. Force yourself to fill in the blanks for things like sensor size, arcsec/pixel, QE, well size, download time, price, cooling capability, etc

Sure you can often find comparisons of a few cameras here and there, but doing this forces you to think about what's most important to you. Trouble is, by the time you're finished, you'll be itching to spend on something no doubt! :lol:

[[1ponders]]

I wish you hadn't said that Rob :lol: Would you care to share yours to save me some time :P

[Jutscher]

Thanks Rob,

Now that I have the spare time, that might not be a bad idea.

[RobF]

Happy to if you really want Paul - mine was pretty slap dash and over a year old now. Your FOV and image scale would be quite different to mine too wouldn't it? Started out as a learning exercise (I thought!), but within a few days I was suddenly obsessed with buying my QHY9/FW/filters package.

[blink138]

sam there is an atik dealer in perth i believe called shane i think,
his prices are the same as andrews and there have been very good reports on his service and professionalism
i would contact him and he may even be able to show you them working
pat

[Jutscher]

Yep, I have met Shane, and he is definitely very helpful - I accidentally ran into him one observing night, he had loads of valuable info on imaging, and helped get my first decent polar alignment using the polar scope.
On the night he was using his 11000, a nice camera.
Web address = Www.theastroguy.com.au
Have spoken to him re: Atik 383, but haven't made a final decision yet.

[gregbradley]

There was a bit of difficulty in getting the driver for the filter wheel to work at one point. I think that has been sorted for some time now.

FLI are the Rolls Royce of imaging cameras. They also dropped their price for the ML8300 to match Apogee their main competitor.

But you will need a filter wheel and filters on top of it plus an autoguiding solution so the cost stacks up. But they are the best as far as the straight camera goes.

Greg.

[Jutscher]

I think I am going to go with Rob's idea of putting all the pro's and cons on a sheet and trying to use that to eliminate various cameras.

The FLI is definately top of the list if my budget will allow it, particularly after seeing the IMOTW - wow (although different chip)

[BlueAstra]

OK, couldn't resist. Here is my spreadsheet when I was looking into getting a SX-H16. You can plug your scope parameters into the yellow areas to get the FOV details. Its maybe a bit out of date, but feel free to modify. The prices are in UKP.

[Jutscher]

Cool, will have a look when I get home, thanks
:thanx:

[M_Lewis]

Like all things, I would see if you can try a camera before you buy it. I own the Atik 383, bought it from the astroguy in perth, as andrews couldn't match the price. I haven't looked back since, and am very happy with the Atik.

There is enough of the 8300 chip around now in the astro communities, that you should be able to get someone to pop over one night with camera in hand, and attach it to your scope. We're talking about an investment here in your astrophotography travels, so I would take a lot of time to make your decision, but ultimately do what you like, not what everyone else likes.

[strongmanmike]

I considered the ML8300 (wouldn't mind one as well) but went with the PL16803 instead and as far as loading software goes, I have Windows Vista on my lappie and today I downloaded the FLI setup kit from the FLI web site (one click) unzipped it all (one click), went upstairs and pluged everything in ie PL16803 with CFW-5-7 & Atlas focuser connected to the ProLine body and it all worked perfectly first time, everything talking to everything else in both FLIGrab, FLIFocus and Astroart4 :thumbsup:

http://www.pbase.com/strongmanmike2002/image/133257295/original

So I wouldn't worry about software issues and the like, and even if there were any FLI would come to the rescue for sure :thumbsup:

Mike

[Jutscher]

Sorry about the delayed reply - my internet router has blown up, waiting for a new one. I had to wait until at work to use their internet.

The ATIK is looking like it might be the go, have only heard good things from people who use it, hopefully, once Shane gets some more in stock, I will be able to test it on my scope for a final decision.

I really like the FLI, but it terms of availability (would likely have to get friom the states) and my current budget, I think it has been ruled out.

Cheers
Sam