Celestron SCT Advanced VX

[Joshelerry]

Canon 5D is the camera, afull frame.
Thinking of Celestron C8 NGT Newt.. I suppose using prime focus on this newt will requires either barlow or protrude to the scope in order to get the focus? Bcos I only see Orion having a specific Newt for ap by having the design of the focus higher up in the eyepiece.

[mymoon]

Hi Joshelerry

As you are a photographer maybe you should get a tracking mount that has goto and a autoguiding port.

Then you can use your canon camera and all your canon lenses for astrophoto imaging from the 8mm f/4 to 400mm f/5.6 . This requires a mount that can carry up to 5kg. The cost is reasonable.

Heavier 300mm and 400mm f/2.8 and 500mm and 600mm f/4 and the new 800m f/5.6 all made good astrophotography tool. Being heavier lenses they demand a mount with heavier load capacity and more expensive.

Even the 70-200 f4 make damn good imaging tool. If later you decided to quit this hobby then you have to sell only the mount.

The men who inspired me to go the lenses and SCT route

click here #1 and do read his comparison with canon L lenses and high end refractors

And

click here #2 and do go to his digital imaging papers.


Unfortunately most astrophotographers started of as a visual astronomer. They peek at the sky through telescope. In order to jump from a star to another they have to know the stars.

Only the new generation start astroimaging with a DSLR and lenses on a static tripod followed by a tracking mount. As photographer they need to know the subject they will be photographing to take great and stunning images. ie as they progress in the picture taking they need to learn astronomy. BTW you can star hop with a GOTO too.

Cheers

[Joshelerry]

So is sct or newt more suitable to do ap? Prime focus i mean

[mymoon]

So is sct or newt more suitable to do ap? Prime focus i mean

Do a google or a bing search . ' So is sct or newt more suitable to do ap'

You will get the answers to your question. Then decide. In this game there is no right or wrong decision. This is the first part of the work flow. Image acquisition.

Both system need new skills and further time investment in learning collimation, drift alignment, autoguiding. Some people is a natural to these adapting like a duck to water. Refractors like your camera lenses rarely needs collimation.

Not to alarm you but image acquisition is the beginning. Then followed by image processing and post processing before you can see the images as posted here.

BTW Astroimaging is the most difficult of all imaging and it can become the most expensive too both in time and money. That is why I support the suggestion that you go and see the various types of imaging gear used for this hobby.

Strange lately I don't see any introduction to astrophotography/astroimaging session in Singastro anymore. Most sessions advertised are for visuals.

Cheers

[Gary]

Unfortunately most astrophotographers started of as a visual astronomer. They peek at the sky through telescope. In order to jump from a star to another they have to know the stars.

Hi mymoon. Why is this considered unfortunate?

Strange lately I don't see any introduction to astrophotography/astroimaging session in Singastro anymore. Most sessions advertised are for visuals.

Just sharing some of my thoughts regarding this. No offense intended and nothing personal.

What you have observed is factually accurate (not many local AP intro sessions lately) which should be hardly considered strange but rather normal. Some potential reasons:

- DSO AP setups involves more equipment, i.e. needs more motivation, manpower, resources (e.g. private transportation) to bring out and setup.

- Requires at least one visible star to introduce concepts like drift alignment, star trailing, importance of accurate focusing. As we all know, some nights can be so bad we hardly even see one star. Whereas for visual sidewalks, even just a Moon on a star-less night will do.

- To a complete newcomer without basic astronomical information to jump straight to AP intro session, chances are, they may spend the most the precious AP intro session time asking about basic visual stuff like how do you know that is a planet, what are the different types of telescopes, how do you find objects in the sky, where to buy telescopes ...etc.

During mainly visuals session like the recent SAFRA Jurong event, we do have an AP setup that attracted a fair crowd of people asking about AP. And the telescope volunteer did try his best to answer those questions and explaining the components of his setup in the context of AP. Though it is not strictly an AP-only step-by-step demonstrative event, I believe it was quite a decent basic introduction to some members of the public that evening.

My point is that just because a session is mainly visual, newcomers to astronomy attending such sessions may still learn a tiny bit about AP directly or indirectly - e.g. why the need for tracking mount, why some telescope designs are better for AP, why you can't captured non-lunar objects nicely with just a mobile phone, portability issues...etc.

AP is like a niche within a niche (general/visual astronomy). One good source of motivation for local APers to conduct AP intro sessions is via increase in public demand for such knowledge. General/visual astronomy (e.g. mainly visual sidewalk sessions) can help by boosting the main base of people getting interested in astronomy and thus boosting the potential "conversions" to APers within those newcomers. If the majority of the general public is not even aware of such objects can be seen through telescopes in Singapore, they would not even have thought about taking a photo through them.

It is hard to imagine why would a newcomer just want to jump to AP immediately and "hate" to waste time on going visual first at least for a short period of time. Surely the main reason why photographers like to photography is because they *see* the beauty in a particular object in the first place right?

So is sct or newt more suitable to do ap? Prime focus i mean

@Joshelerry - Coming back on topic to your question, the answer is not a very straightforward one that can be explained in a few words. As mymoon suggested, google this question and one can read the informative discussion threads in Cloudynights forum to understand the various factors involved. Best is to observe and learn from an AP veteran directly - see how he/she go through his/her workflow under clear skies.

It is extremely daunting to figure out everything by yourself or just by reading a few forum posts here and there (even for a visual system, let alone AP). And the price to pay from any potential misunderstanding can be very high - e.g. committing to an AP setup and then find out you have grossly underestimated the AP-related problems and end up having to sell almost everything at a loss and buy another new setup all over again.

If you read enough posts in astro forums, you will surely come across posts like "if I am able to start all over again, I would have bought this and this instead of that and that". Even during public stargazing sessions, you may hear telescope volunteers tell you their had-I-known-earlier stories.

Assuming you intend to buy your AP setup with after a couple more months of research, you will be very eager to do AP and get the maximum value out of it. Even if you buy it earlier, you may spend a couple of months to understand the complexity of AP and intricacies of your telescope setup. But by then, we may be already in the year-end monsoon period where clear nights will get rarer. The next clear stargazing/AP season may begin around March/April 2014. So why not be patient, take your time to do deeper research, save up longer to increase your budget (if necessary), learn from the AP pros, "play" with the telescopes for free at public stargazing session to increase your experiential knowledge in the meantime? Or course even during monsoon period there will be a clear night here and there. But staring at your new telescopic investment in a dry cabinet night after night of bad weather is something not easy to swallow and stay optimistic about.

Of course, there is Comet ISON in November which MAY be a good reason "hurry up" your purchasing decision, learn AP super fast and capture this *potential* once-in-a-century event. But then again, like most comet hunters will tell you, comets are like cats - can be totally unpredictable.

[Gary]

Visual is primary but however imaging will come along because I'm a photographer myself and hence it will come quite naturally to capture what we see.

Can fully understand this nature to capture what you see since you are a photographer. I guess you have already heard this many times by now but still worth repeating and emphasising - DSO astrophotography involving telescopes is almost like nothing you have come across in your non-astro photographic experience. To think otherwise is like someone thinking he/she can easily learn how to "fly" a spacecraft to Moon and back because he/she has plenty of experience flying commercial jets!

The main challenges which normal photography don't usually encounter are:

- Factoring the rotation of Earth during the shot.
- Need for high-precision tracking instrument.
- Need to deal with light pollution in urban environment
- Precise focusing on a single dot of light
- Learning post-processing techniques like stacking and various signal-enhancing techniques

So if you already decided "visual is primary", do pay attention and stick to that and not sacrifice too much of visual in hopes of getting better AP out of your setup. Else, there is a danger that you may end up with a setup that is neither here nor there.

[MooEy]

Forget about anything celestron if you want to do deep sky astrophotography. SCT are one of the last choices when it comes to deep sky imaging, almost anything is better.

You need at least 2-3 years of imaging experience before you can handle those 1500mm+ of focal length. If you cherish the hair on your head and desire tight round stars, pick up a small apo refractor with a reducer/flattener. Those will fill your full frame sensor nicely and the shorter focal length makes it easier to get round stars for a start.

Forget about drift alignment, I don't do it for short sessions. Just let the autoguider sort out the drifting issues. Pick up a decent mount, look at vixen or losmandy for a start. Those typically comes with decent gears that are under +/-10" of error. Make sure you pick up a new one or one used by another imager. Bumps and knocks can cause damages to the gears resulting in erratic tracking errors. Like orly mentioned, the mount is the most important part.

Pick up a small 50mm finder with an adapter for the guider. KW telescope and Modern Astronomy sells the finder with the adapters. You can use either the QHY5/StarShoot Autoguider or the ASI-120 as your guider. If you are feeling loaded, SBIG ST-I and Starlight Xpress Lodestar are good choices. For the rings, Stellarvue R50E is one of the best.

And stop browsing those Celestron ads, most products they sell don't work as advertised.

~MooEy~

[mymoon]

Coming from a photographic background I found it is easier to introduce astrophotography to photographers than to those who has been involved in visual astronomy and learning astrophotography from visual astronomer will be like learning physics from a maths teacher. That I consider unfortunate. Sorry Gary. No offense meant to you. You are doing a great job introducing the night sky to the people.

You want to know astrophotography go to the astroimagers. There are a number of them in Singastro, people who speak your language. The figure 200mm to visual is not the same to an astroimager ; one represent aperture and to the other is focal length.

Take care though go to those using DSLR and not (yet) those using CCD. The picture you shoot (mostly in RAW) needs to be tweak using image processing softwares before presenting to the world via Singastro or Flickr or printed to be displayed on the wall. Night photography is an extension albeit a more demanding one of day photography. Doing it in the dark in an unfriendly and hostile environment of mosquitoes and leeches is a challenge indeed. Another enemy is dew. Their favourite resting place is the front of your lens.

To be good in photography you have to know your subject matter you are going to photograph. Otherwise your photos will be technically correct good only for record but lacking the oomph that makes a picture great.

Hence to photograph the night sky you have to know when the objects are in season and the best time to shoot them sky conditions permitting. Nowadays there are Apps both in the IOS and Androids tablets and smartphones to help you with the objects and composition and their location in the sky too.

So I recommend budding astroimagers to start with nightscapes. All that is required is the DSLR with a steady tripod (it can be windy at night) a kit lense 18-55mm,a 50mm, a intervalometer and a dark sky. Equipment already in your possession. The only item to buy and use is a red torchlight. Learn how to do manual focus on dim stars. Focus, focus, focus.

Good examples of the genre can be found at (google) TWAN websites. You can shoot the Milky Way(on its back or standing), the constellations, the moon and the stars trails and learn how the stars moved and how they affect your star trail composition. You begin with single shot first. Next you progress taking multiple shots and learn stacking of the images using astro imaging software and daytime use PhotoShop, noise reductions and/or using dedicated astroimaging softwares. If weather is not too kind to you , spend the time shooting timelapse of clouds .

Once you got tired of taking nightscapes then progress to the next step in using longer focal length lense. If you got deep pockets you go for 70-200mm f/2.8. Otherwise a 70-300 f/5.6 will be acceptable. The two stops handicap can be overcome with doubling the ISO and smart use of the noise reduction technique. You may need to add another equipment; a hotshoe RDF for your pointing.

You can now capture images called lights by still using the tripod capture the orion nebula, andromeda galaxy and other big bright objects etc. Do learn about dark frames, bias frames, flats and how to mix them with the lights to make an image.

Next you can upgrade to using a photographic accessory known as Star tracker. It sits between your camera and tripod. Their job is to track the sky allowing for longer image exposures. You will be now expose to polar alignment. Read Joyce article on how she polar align the Polarie tracker. You can now do wide angle astrophotography as define by astronomers. The trackers come in all shapes and carrying capacity; up to 500mm f4 lense .

Now that you have encroach into astronomer's territory you may wish to continue and go for telescopes and german equatorial mounts (GEM) and learn about drift alignment, guiding scope etc. It took me along time to learn that your goto accuracy is dependent on your drift alignment and that even the China made mount can track without guiding for one or two minutes if properly aligned. Then you have to align your goto for pointing accuracy.

Good Luck for the sky is the limit and can very quickly burnt a big hole in your pocket. Like Orly says go for the best mount you can afford and carry and for telescopes you can consult Remus. Don't forget to leave some change for softwares.

So you can learn astroimaging in a structured way or jump headlong into it and then backtrack. Unfotunately there is no shortcut; you still have to know your ABCs and your grammar before you can write you sentences progressing to an essay. But like LKY says getting your fingers burnt and you will also learn.

my dua sen.

[orly_andico]

I am wondering why this isn't stated enough.

If you have a lens like a 70-200/2.8, 200/2.8, 300/4, 300/2.8 or similar, those make great short refractors. No need to buy anything else!

Few bits to add to MooEy's post:

1) to handle 1500mm+ focal length, you need a good mount. Losmandy G11 minimum (and even then success isn't guaranteed). No matter how many years of experience you have, you will not get any success imaging at those long focal lengths if your mount isn't up to it.

On the other hand, have heard of newcomers who image successfully in less than a year with these long scopes, but they put a lot of money into the mount. There's this guy on Cloudynights forum who is producing results as good as the veterans, in under one year. He got an ASA DDM85 mount. I leave it as an exercise to the reader to find out what that costs.

With astrophotography, there is an element of "buying your way to success." Buying a full-frame camera will not make your photos look better. An expert with an Instax could still produce aesthetically better photos.

But an amateur with limited experience but a high-end mount can produce better-looking photos than an expert with an entry-level mount. I say "can" not "will." But it's possible.


2) it is possible to image with an SCT. I am doing it (and with a Celestron at that!) The SCT has many diseases: mirror flop, horrific amounts of coma and curvature, a very long focal length - all of these can be dealt with. But if you're fighting your mount at the same time, these issues will prove insurmountable and you'll lose much hair. What do I do -

a) a good mount is 80% of the battle
b) I have a focuser lock on my SCT, helps with mirror flop. A mirror lock is better - so you're better off with a C8 EDGE.
c) I use a flattener to fix the coma and field curvature; again a C8 EDGE would address this issue (built-in flattener)
d) I limit exposure lengths to 5 minutes. Which sucks because the f/10 focal ratio means you're not getting very much at 5 minutes.

I only use my SCT for imaging small planetary nebulas, which are too small to show any detail in a refractor. Also PNs are bright, so the f/10 focal ratio doesn't hurt too much.

So if you really want to image with an SCT,

a) get a C8 EDGE
b) get at least a Losmandy G11 mount, or a Vixen Sphinx SXP or SXD2 (not an SXW or SXD) - maybe a Vixen GP-DX or GP-D2 would be able to handle a C8 for imaging, but I wouldn't gamble on that. When you skimp on the mount, 90% of the time you will ditch it down the road and buy a better one, losing money in the process.

Telescopes may come and go, but a good mount is forever.

[MooEy]

I think the G11 is pushing it. The Mach1GTO/PMX would be more ideal for those focal lengths. Given 200mm of aperture and maybe f/7 after the reducer, there is still a whopping 1400mm of focal length. The pixel size of the 5DMkII is 6.4 microns. That works out to be 206.265/1400 * 6.4 = 0.94"/pixel. Unless the mount has those super good 5-7" peak to peak of PE, I doubt it would guide very well in the sub-arcsecond range.

~MooEy~