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Old 20-02-2010, 10:21 AM
NilRecurring
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Tak FSQ-85ED + KAF-8300 Combination

Hello everyone! First post on iceinspace!

I came here looking for some advice on this setup that I am considering. I've ordered a Takahashi FSQ-85ED and a SBIG ST8300M and plan on using them together. I will be using them on a Losmandy G11.

It provides me with an image scale of 2.47 arcsecond/pixel and a FOV of 138.9' x 103.2'. I understand that anything between ~1 and 3 arcsecond/pixel is fine. Am I correct in assuming this?

If I buy the 1.5x extender, I can achieve a image scale of 1.65 arcsecond/pixel.

What do experienced imagers here think? One of the reasons I went for a small scope was I was recommended to start with a scope (I do have some experience with Astrophotography, but not extensive) that has a short focal length, as it will make my life easier. My primary interest is both galaxies and nebulae imaging.

So, I was thinking that I would start with nebulae and some galaxies and provide a good size in this FOV, and then later on add a higher focal length scope to my arsenal.

Any advice would be appreciated.
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Old 20-02-2010, 11:06 PM
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zipdrive (Dave)
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That sounds like a great combo!

Welcome to the forum
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  #3  
Old 21-02-2010, 10:51 PM
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Sounds to me like you know enough to gather photons and present them very well. Your equipment is as sound as your logic IMO
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Old 25-02-2010, 09:17 AM
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The old addage of 2" per pixel is now a bit out modded. Current thinking is that over sampling is fine and under sampling is not great. You may find that you are slightly under sampling with that setup and it could cause some square stars. The problem lies with the focal length of the scope rather than the pixel size in the camera. It is worth a try though as this will present a nice wide field. If it does not work you can always sell the scope.

The ST8300 is great for galaxy work when combined with a longer focal length scope. I currently have my setup at 0.7" per pixel and this allows a great deal of sharpening before it becomes a problem.

With a slightly shorter FL you will find this sensor will perform well. Several chaps here are using 700 odd mm of FL and achieving really nice results.

Best of luck.
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Old 25-02-2010, 09:47 AM
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Quote:
Originally Posted by Paul Haese View Post
The old addage of 2" per pixel is now a bit out modded. Current thinking is that over sampling is fine and under sampling is not great. You may find that you are slightly under sampling with that setup and it could cause some square stars. The problem lies with the focal length of the scope rather than the pixel size in the camera. It is worth a try though as this will present a nice wide field. If it does not work you can always sell the scope.

The ST8300 is great for galaxy work when combined with a longer focal length scope. I currently have my setup at 0.7" per pixel and this allows a great deal of sharpening before it becomes a problem.

With a slightly shorter FL you will find this sensor will perform well. Several chaps here are using 700 odd mm of FL and achieving really nice results.

Best of luck.
Paul
Thats interesting as a 10"SCT fl 2500 with a 0.63 converter gives a fl of 1575 and using the information on the SBig site (http://www.sbig.com/sbwhtmls/ST8300.htm) for the camera shows this is right in the sweet spot for this camera 0.74 arc sec/pixel and 0.89 arc sec/pixel without the converter (but binned 2x2). Thus if my reasoning is correct then the st8300 would be OK for this setup without too much oversampling? Comments would be appreciated as Im just getting my head around all of this.
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Old 25-02-2010, 02:43 PM
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You should also think about how you are going to do the guiding - i.e. guide scope, OAG, self guiding CCD etc...
As a main imaging scope, the FSQ106ED would be a better option (if it's within your budget of course)
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  #7  
Old 26-02-2010, 07:47 AM
NilRecurring
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Quote:
Originally Posted by Paul Haese View Post
The old addage of 2" per pixel is now a bit out modded. Current thinking is that over sampling is fine and under sampling is not great. You may find that you are slightly under sampling with that setup and it could cause some square stars. The problem lies with the focal length of the scope rather than the pixel size in the camera. It is worth a try though as this will present a nice wide field. If it does not work you can always sell the scope.

The ST8300 is great for galaxy work when combined with a longer focal length scope. I currently have my setup at 0.7" per pixel and this allows a great deal of sharpening before it becomes a problem.

With a slightly shorter FL you will find this sensor will perform well. Several chaps here are using 700 odd mm of FL and achieving really nice results.

Best of luck.
I see.

Well, the FSQ-106 is out of my budget, as when I include the accessories, that pretty much adds another $500. At this point, I'm at $3500. With the 106EDX, I will be at $4500, way out of my budget.

But if you think 700mm of FL is going to be ok, then adding an extender to 85ED will provide me with a scale of 1.65"/pixel (FL of 675mm). Is this still undersampled? The extender is a further $300.

Secondly, I'm intentionally going for short FL scope, I'm just a beginner and I have been recommended a short FL scope to start off with by numerous folks.

Regarding guiding, I have a Orion ST80 for a guidescope along with a Orion SSAG.

Half of the people I've talked with have told me 2.47"/pixel is just fine. And the other half tell me that its not. I really don't know what to do about this. I'm trying to make a rig thats going to last me a long time and due to location (Pakistan), I cannot easily sell stuff, as there's virtually no market for this. So I try to buy the best I can afford so I don't 'upgrade' every 12 months and waste money.

There is something that makes me feel I'm making the right decision. The FSQ-106 is often coupled with the STL11000, which has huge pixels and provides a image scale of 3.3"/pixel, and I can still see lots of stunning work with this combo.

Last edited by NilRecurring; 26-02-2010 at 08:13 AM.
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Old 26-02-2010, 08:50 AM
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I understand your point of view.

With the extender I am not sure it is 2" or bigger to maintain your imaging circle. It might be worth a check.

Yes the FSQ106 and STL11L have been mated together several times and acquired fantastic results. If you can image at 1.65" per pixel this is better than 2.47", just for sharpening value alone. It is all really just a guide but like others have said getting the 106 would be better in the long run.

This is all just current thinking and so long as you don't get blocky stars it really does not matter which sensor you go with. Experts such as Peter Ward, Martin Pugh, Mike Sidonio and Greg Bradley will have more definitive answers for you. They are all members here and I urge you to contact them via PM.

Best of luck with your decisions
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Old 26-02-2010, 11:12 AM
NilRecurring
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Originally Posted by Paul Haese View Post
I understand your point of view.

With the extender I am not sure it is 2" or bigger to maintain your imaging circle. It might be worth a check.

Yes the FSQ106 and STL11L have been mated together several times and acquired fantastic results. If you can image at 1.65" per pixel this is better than 2.47", just for sharpening value alone. It is all really just a guide but like others have said getting the 106 would be better in the long run.

This is all just current thinking and so long as you don't get blocky stars it really does not matter which sensor you go with. Experts such as Peter Ward, Martin Pugh, Mike Sidonio and Greg Bradley will have more definitive answers for you. They are all members here and I urge you to contact them via PM.

Best of luck with your decisions
The 106, might, indeed be the better long term scope. However, at what cost and for what? For an extra $1000, I will gaining: focal length and image scale. The image scale, without the extender, will be 2.1"/sec (up from 2.47")... but at a cost of $1000. Sure, I get aperture as well, but its the F-Stop that counts and the difference is very small; 85EDX is F5.3 and the 106EDX is F5.

I am already buying the ST8300 and Baader 2" HaLRGB Filters. This comes upto about $3000. If I take advantage of the QHY9 offer these days i.e $2000 for camera, filterwheel and LRGB filters, I save about $1000 and I could essentially use that money for the FSQ-106. But, nothing comes for free and the SBIG comes with great software. Secondly, I don't know what the quality of the QHY9 filters is - what's the point of buying a telescope like the FSQ-106EDX, only to use it with average filters?

Why not instead, after gaining some experience with the FSQ-85ED + ST8300M and learning for at least a year, buy a AstroTech RC8, which has a focal length of 1625mm and costs about $1395?

What is your opinion?
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Old 26-02-2010, 11:27 AM
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I suggested the FSQ106ED because you will never out grow it. It will be a scope for life, and that, is a good thing.
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Old 26-02-2010, 11:31 AM
NilRecurring
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Quote:
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I suggested the FSQ106ED because you will never out grow it. It will be a scope for life, and that, is a good thing.
Well, I really doubt I'd grow out of the 85ED. Considering the type of work people turn out with small ED refractors, I am a long long way to reach the limit of this 'scope. But, again, this is something i cannot quantify.

If you mean that I will need to buy another scope when I upgrade to a bigger sensor, perhaps. But the 85ED has an image circle of 44mm. One could fit a 35mm frame easily inside that, if I'm not mistaken.
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Old 26-02-2010, 11:33 AM
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Keeping tp the 85 for a year and then going to narrow field imaging is certainly a wise move. Guiding and flexure can be very frustration when stepping up to the RC8". That I can attest to myself.

The 106 is the sort of scope you buy and keep all your life. Just something I thought would suit your long term plans given you are living in Pakistan.
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Old 26-02-2010, 11:35 AM
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Originally Posted by Paul Haese View Post
Keeping tp the 85 for a year and then going to narrow field imaging is certainly a wise move. Guiding and flexure can be very frustration when stepping up to the RC8". That I can attest to myself.

The 106 is the sort of scope you buy and keep all your life. Just something I thought would suit your long term plans given you are living in Pakistan.
I really do appreciate your advice.

But could you give me reasons as to why the 85ED cannot be a 'life-time' scope and the 106EDX can?
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Old 26-02-2010, 12:45 PM
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Astrophotography is like that. There is always a better mount, camera and scope out there. The FSQ-106ED is a top of the range scope. There is a good chance you will outgrow the 85ED one day and it will be relegated to a guide scope. That's okay, so long as you are aware of it up front.
What do I mean by top of the range? I mean the gear that is used to take the APOD images for example. Paramount ME, STL-11k, 16803, FSQ106ED, RCOS etc etc appear time and time again.
James

PS - by the way I also agree with the stuff Paul has said.

Last edited by Moon; 26-02-2010 at 12:48 PM. Reason: spellink!
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Old 26-02-2010, 01:15 PM
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James nailed what I was thinking. The FSQ106 is one of the few wide field scopes that is mentioned in kits at places like GRAS and New Mexico. It just happens to be the one most recommended by the best imagers. I am sure the 85 is a fantastic scope and if this is all you can afford then go for it. It will leave many scopes of its class for dead and has the Tak build quality. We are just trying to make sure you get what you need.
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Old 26-02-2010, 01:19 PM
NilRecurring
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I will think about it.

While I cannot increase my budget, I suppose I could forego the ST8300 and the Baader filters, and get the QHY9, filterwheel and filters. That'll save me $1000, and I could get the 106EDX for that.

I just wonder if its the better choice.
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Old 26-02-2010, 01:26 PM
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I will think about it.

While I cannot increase my budget, I suppose I could forego the ST8300 and the Baader filters, and get the QHY9, filterwheel and filters. That'll save me $1000, and I could get the 106EDX for that.

I just wonder if its the better choice.
IMHO it's a no brainer. Get the 106. You still can get a better cam later. That scope will last you a lifetime.
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Old 27-02-2010, 10:34 PM
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I get 2.32 Arc:seconds per pixel with my setup (TMB 80/480 + ST8300M)

Whether you go for the FSQ85 or the FSQ106, both will provide awesome images with any camera. The KAF8300 sensor is made for wide field imaging. Your proposed setup sounds awesome!
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