Imaging question for newbie

[Stevo69]

Sorry if this is explained elsewhere, but I've searched for it for some time.

I'm trying to choose between C11 S-GT XLT (EQ mount) and CPC 11 XLT (fork mount).

If I bought the CPC 11 with fork mount, I don't intend to do imaging or astrophotography straight away, but the time will come when I want to advance. I will naturally buy a wedge.


Question 1: Should I get the same imaging results between a C11 on a GEM mount, and a C11 on a fork and wedge arrangement? I'm thinking more regarding the performance of the drive mechanism. I hope this makes some sort of sense.

Question 2: Imaging CCD devices on the market highlight the fact that they are for planetary imaging. Not much is mention regarding general field objects, DSO's etc.

I don't have a camera so when the time comes, will a CCD be sufficient for medium/long exposure images for DSO's?

Has anyone taken any CCD images of DSO's and if so, can they post them up here or provide links?

[monoxide]

im no expert when it comes to imaging but ccd's are very good for imaging both planets and dso's, what you primarily want to image would determine what camera you would get. i wont turn the thread into a debate by mentioning models or brand names but take a look in both the deep space and solar system image section of the forum and youll see lots of photos taken with ccd's.

[iceman]

Hi Steve

I can't answer the performance of an GEM vs fork/wedge arrangement, but regarding the CCD aspect, the C11 is fine for CCD DSO work. The large aperture is great, but the long focal length of the C11 will make it more challenging if you don't go all out with respect to guiding etc.

You'll want a focal reducer to make it a little easier to start, to give you a wider field of view and a faster focal ratio.

Regarding CCD's, for budget-medium range you'll be looking at either a DSLR or a DSI/DSI-Pro type of camera. If you already own a DSLR, with the right adapters you can get started almost right away.

There are many DSO images taken using DSLR's and DSI's in the Deep Space section of IceInSpace, so just start browsing around and keep asking questions.

Just beware that the photography side of things is quite indepth and will start costing more and more money :) Not only the equipment, but the software as well (there is free stuff, too). Not to mention the time taken in capture and processing.

I hope you're ready ;)

[Stevo69]

Thanks for your opinion and advise, iceman. I think I may be using the wrong terminology. Last time I did any sort of astrophotography was 15 years ago with an Olympus OM-1 (if anyone remembers that famous camera!)

Can I clarify some of what you've mentioned: A DSLR is a common digital SLR "still" camera - understood that one. A DSI? are you referring to a CCD imager? i.e. a live capture image with a video output that can connect to a PC and appropriate software?

Actually this is what I want to achieve. A C11 SCT, and a "live capture" CCD imager such as here (http://www.celestron.com/c2/product.php?CatID=50&ProdID=354)connected to a notebook. Will this allow me to capture DSO's?

I sort of understand the concept of still, long exposure photo's will produce better images, due to the long exposures. But can the same results be achieved from live CCD devices and PC software?

Oh boy, if I haven't confused you now, I'm going good. Thanks in advance.

hoo roo.

[montewilson]

I'd like to reinforce what Mike said by saying that unless you are a super-human, starting imaging with a C11 at prime focus will almost certainly end in frustration and you'll sell the scope and go sailing or whatever you can do to get as far away as possible from Astronomy. I've seen it happen too many times. It's probably the single biggest killer of Astro-enthusiasm.

Get the C11, its a great scope and you will see heaps with it. But before you take on imaging, use a camera on it piggy back, then do the same through a small scope or telephoto lens and you will get good results quickly. This setup will allow you to get magazine quality images without pulling your hair out. You won't have to spend a fortune to get pictures (above the cost of the scope and DSLR ) This way you can guide through the C11 and image through something smaller on its back. 1000x easier! Also you will have a great visual scope and a good camera for day to day photos too.

When you have learnt all about imaging through 50 -500mm lenses/scopes you will know enough to take on the mighty C11 prime focus challenge.

[gbeal]

I agree with all the above, but if you don't already have the C11, perhaps look for one that has the "Fastar" of "Hyperstar" setup. This allows you to remove the secondary and use the primary as a BIG FAST mirror. This would get you round the frustrations of imaging with the native or reduced C11. It will however not really be suitable for DSLR type CCDs, so I may have you slightly off track here.

[rumples riot]

Get the C11 but with and equatorial mount. Fork mounts are alt/az and are a bit too tricky to get into DSO imaging. You can use a wedge to mount them and convert them to polar but there is flexure from the tines of the fork. The equatorial mount will track well and that eliminates a whole range of problems from the start. GEM's are the most realiable mount.

The DSI is a CCD camera. You can connect it directly to the computer. However, you will need a guide scope to take long exposure images. You can initially get away without one, by using short exposure times under a minute and taking a whole heap of images and combining them, but long term you will be reaching for a guidescope.

The Nextimager that you linked is not the best for what you have in mind. It is only really good for the planets and even then it is not that great. Imaging equipment can be cheap to get you started but to get really super high quality images that you can print into posters requires more expensive camera's.

The same results can be achieved from CCD's as normal long exposure but like I said you will need a guidescope and dark skies. Many great results can be achieved, but choosing correctly now is important.

In terms of CCD's for DSO imaging, try looking for Sbig as a brand name. The are dedicated to DSO imaging. They are expensive but produce excellent results. A DSLR is the most appropriate at this stage though.

Paul

[Stevo69]

Thank you everyone for your opinions.

I don't see myself getting big into astrophotography because this telescope purchase in the next 12 months will almost certainly be the last telescope I ever purchase. I don't see myself every spending anywhere near the same amount of money again on astrophotography equipment. Maybe I might purchase a CCD imaging device as I already have a laptop.

So why am I asking these questions? I guess I just doing some advanced research. Just in case taking a few images takes my fancy. But I certainly don't see myself in the financial position in the future to dive into astrophotography. I am leaning towards a C11 S-GT XLT (EQ mount). And I don't want to spend this sort of money and find the telescope is absolutely 100% non-suitable for astrophotography, 2 or 3 years down the track.

montewilson: You mention the term "prime focus". Is that when you mount the CCD device to the eyepiece on the OTA?

rumplesriot: Is the flexing of the fork that much of an issue? I'm not doubting you, just surprised. Can anyone else elaborate on the drawbacks of fork over GEM for astrophotography? Is it due to the mechanics of the drive motion on an Alt/Azimuth trying to act like an EQ motion? I guess a drive tracking an object on an Alt/Azimuth from horizon to meridian, then to horizon again is a series for "steps" for both Alt and Azimuth drive mechanism? (up, left, up, left, up, left....then after the object reaches the meridian, down, left, down, left......) Correct?

[montewilson]

Yes Prime focus is when you put the camera where the eyepiece normally goes. If you have an eyepiece there and then a camera that is called eyepiece projection and it will increase the magnification and ergo the complexity and reduce the guiding tolerance.

If you plan to do mainly observing a fork is OK but they have problems when you go close to the pole (Small Magellenic Cloud for example) because the camera can touch on the base of the mount. GEM is certainly the prefferd option for imaging scopes in our size bracket.

[Stevo69]

Thanks again montewilson. I'm convinced a GEM is the way for me. And a Celestron C11 S-GT is the favorite.

And I understand where you're coming from re: starting off piggybacking and easing into prime focus and eyepiece projection down the track. Small steps! but after the big purchase, funds for a DSLR/DSI will be limited.

What is the advantages over a long focal length anyway. Can someone briefly explain that? From memory it is especially important for planetary work.

rumplesriot: Thanks for the heads up regarding SBig DSI's.

I have lots more DSI questions but I'll post them as I get closer to purchasing the 'scope. (Perhaps as time gets closer to purchase day, I may have to kindly ask to tag along to an Astro Camp somewhere to see a C11 and DSLR/DSI's up close in action.):whistle:

[rumples riot]

Steve, if you plan on using a fork mount in alt az mode, you will need a derotator so that field rotation is removed. Using a field rotator is not the preference; a GEM is the best mount for long exposure photography.

[Stevo69]

Hi rumples riot, no I've decided on a GEM. The C11 S-GT has a GEM..

[iceman]

Hi Steve
Long focal length doesn't really have much advantage for deep-space photography - it's more challenging, requires greater accuracy in tracking. The benefit is, you get up close and personal images of deep-space objects. For example, you can take a close-up image of the keyhole nebula in Eta Carinae, instead of the widefield view of the keyhole and all the surrounding nebula.

For deep-space imaging, you'll want a focal reducer, or even a widefield faster scope like an ED80 piggybacked on top of your C11 - you image through the ED80 and guide through your C11.

For planetary imaging, long focal length matters. The longer the focal length = the more magnification = the more resolution = the more finer, small structure details you see on the planet/moon. The caveat is, the longer the focal length, the better the seeing needs to be to get sharp images and actually resolve those fine details.

[Stevo69]

Thankyou again for all the above opinions. May I throw another variable into the equation?

I had almost set my sights on a Celestron C11 S-GT XLT (EQ mount), but have looked further into a Celestron 10" C10N-GT.

Both have the CG-5 GT mounts, so the real differences are the aperture (the C10N-GT is 1" smaller), and a Newtonian versus a SCT. Potentially the C10N-GT is half the price, depending on where I shop.

My two aims are the same:

This purchase would be for an investment as I aim to keep it for many years to come (this will probably be the last telescope I purchase).
I still aim to get into astrophotography down the track using a CCD device, rather than a DSLR.
An aperture of at least 10" (I've already owned 4-6 Newt's).I would welcome any further opinions to help me choose which one would be suitable.

hoo roo
Steve

[iceman]

Hi Steve.

I love newtonians, and much prefer them over SCT's. However for astrophotography, the newt may require the mirror to be moved up the tube, or to get a low profile focuser, if you wish to use a DSLR on it. For a CCD device, i'm not sure.

Also, a newtonian on an EQ mount can get the eyepiece into odd positions and difficult to observe through. You need to make sure you can rotate the tube in the rings to ge the eyepiece into a comfortable position.

Apart from those 2 things, I much prefer newtonians.

But the C11 is a good scope, too.

[Stevo69]

Yeah, I understand this, I don't have a problem with this. I'd have to buy a step ladder also!! But because I've build newtonians in the past, I sort of feel more comfortable owning one, as a SCT-type is completely new to me. So that is why I am now looking "outside the C11 circle".

The preference towards a EQ mount with drive, over a Dobbie is because I used to spend many, many sessions, many years ago, trying to show family and friends objects and constantly re-aligning the field of view. I've never had a EQ mount with a drive, and although a 16" Meade Lightbridge would be absolutely amazing!, I recall those early days of amateur astronomy, when I would constantly re-aligning the field of view.

[Terry B]

The other very obvious difference between the SCT and the newtonian is the problem of fogging. The large corrector plate is much more prone to fogging. This is fairly easily dealt with with heaters etc but it is one more thing to worry about.
Having said that my scope (VC200l) is a compromise between the two. A cassegrain with an open tube. It is however much smaller.