Celestron SCT Advanced VX

[Joshelerry]

Hi just checking how sct with goto is important for long exposure astrophogaphy?
Can newt do the same w goto equupment?

[Gary]

Hi just checking how sct with goto is important for long exposure astrophogaphy?
Can newt do the same w goto equupment?

All telescope designs with a tracking mount/mechanism can do long-exposure astrophotography. GOTO is good to have to speed up the finding of objects but not compulsory as one can find them manually if they know how to.

So the more important questions are:

(1) How accurate is the tracking of the complete setup to the extend that captured stars are pin-point sharp even at the edge even after very long exposures?
(2) How hassle free can (1) be achieved? E.g. need to spend time collimating telescope, long cooling down time of optics, need for extensive dew protection ..etc.
(3) What telescope design (e.g. focal ratio, field-of-view, flatness of view) is good for the type of celestial objects one wish to capture via long-exposure photography?

Generally, for long-exposure astrophotography of Deep Sky Objects (DSO), the refractor telescope design is the most popular among DSO astrophotographers.

[Joshelerry]

Hi, thanks

I'm considering Newt or SCT bcos of the aperture/value ratio. Mainly will like to settle for 8" around there. 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.

1) Can SCT be use on daytime like a refractor telescope? That is understand that for Newt it can't because the image is upside down but for SCT/refractor is it ok to use as a daytime telescope abeit with mirror image?

2) Favor is on SCT because I have a Full Frame Camera which I intend to plug to the end of the tube and there is apparently no focusing issue like that of the Newt. Not all image will be long exposure though, some lunar, planetery shots as well but I will not plan to have more than 1 scope and hence will like to get one that can shoot DSO; of course I understand there is no ONE SIZE FITS ALL scope here.

3) The mount is computerized and hence I suppose if the battery went flat; it means "pack up and go home" then? Because is there any possibility to attach some manual knob for fine adjustments?

4) You mentioned accurate tracking, I suppose Celestron Advanced VX mount with the Nexstar system is trustworthy on this area? Unless the setup is not done properly.

[orly_andico]

SCT's have a horrendous amount of field curvature.

Hence on your full frame camera any stars beyond perhaps 20% of the center will be elongated like fat eggs.

You would need some form of flattener/reducer to flatten the field. The reducer also reduces the SCT from f/10 to maybe f/5 to f/7. Problem is the reducer also shrinks the image circle, so there will be tremendous vignetting. In my experience, there is no way an SCT can fully illuminate a full-frame DSLR.

The main problem with the SCT is the long focal length (2000mm) which magnifies mount errors. Also it is very slow - f/10 - so you will need very long exposures, which combined with the long focal length means you will need a very expensive mount (which the AVX is not).

Optec sells a 0.5X reducer which flattens and reduces the SCT to f/5 - but it shrinks the image circle dramatically, to 18mm diameter, which won't even cover an APS-C sensor.

With regards to accurate tracking - the AVX is an entry-level mount. I wouldn't try imaging with an f/10 SCT on that mount, guaranteed hair loss. The gears simply aren't accurate enough.

Like the man (Gary) said - you're best off with a refractor if you intend to image. A refractor will be fast (f/5 to f/7) and even faster with a reducer. It won't need collimation. It has no mirror flop. And the focal length is short (usually 500 - 700mm) which means it's more forgiving of mount errors.

Imaging and visual don't have a lot of overlap, what's good for one will not be that good for the other.

If you want a decent visual and imaging scope, don't buy the AVX bundle. Buy an Astro-Tech 8" imaging Newtonian.

It is 8" so decent for visual (albeit it has an over-size secondary, which is required for imaging). It is f/4 and only 800mm focal length, so the FL is manageable and its focal ratio is fast. You will need a coma corrector though, Astro-Tech makes a nice one. Or the Baader MPCC.

[mymoon]

Sometimes in life advances are made by not following to the herd. I image for hobby and not for scientific research.

You have two issues here. The first is the Celestron Advanced VX mount
The second is the suitability of f10 SCT for imaging in this part of the world.

I own a Edge C11 to image smaller DSOs. Compared to my other scope WO 110 FLT at f7 the C11 gives a huge image scale. So for bigger objects I image with the WO and for smaller ones with the SCT both using a Canon 60d modded with a LPS filter at prime focus. I image from KL in the white/ red zone of the Bortle scale. The measured SQM is 17.4.

Also using the Edge C11 I can get resonable size images of the planets using the video crop mode or what is now known as Lucky imaging. Try it sometimes.

When the moon is up even at full moon I image with the clip on 6mn Ha filter. As long as the object is not inline with the moon's path you get a decent image.

I autoguide using the 50mm guide scope piggy back and a QHY5 mono with PHD. I am using an ancient Tak NJP Temma2.

As to the Celestron mount I cannot advice for I do not owe it or have any experience with it. If it is the same built as the Atlas EQ6( my other mount) I will vouch for it.

Maybe this video will help with the mount. It tells you how to drift align too. A must for astrophography.

Click here

BTW my other scope is a Celestron C8.

Cheers

[orly_andico]

IIRC mymoon has a Takahashi NJP mount.

hardly comparable to a Celestron AVX...

at the end of the day, for imaging the most important part is the mount, and that gets expensive really fast.

[ivan]

Hi just checking how sct with goto is important for long exposure astrophogaphy?
Can newt do the same w goto equupment?

I'm pretty much a beginner in AP, but so far this is what I've gathered (more experienced AP-ers, correct me if I'm wrong):

GOTO isn't essential for long exposure AP. It only assists in searching for the object. After which, the GOTO only tracks in RA. Instead, what's more important is a decent german equatorial mount - one that has good RA tracking and is stable (note: higher stability often means a heavier mount, which implies lower portability). For exposures beyond one minute, you will find that you require guiding.

As for the AVX, it should be able to give decent guiding below a minute, assuming you have done accurate polar alignment. It has an in-built all star polar align feature that gives decent accuracy, but often what you'll find is that you will need to do drift alignment. Also, the AVX has periodic error correction, unlike its CG-5 predecessor, which is useful for AP.

As for the OTA, however, I wouldn't recommend an SCT. SCTs are best for planets and small planetary nebulae, but to capture stunning wide field nebulae, the long focal lengths of SCTs are a bane. Even the C6 has an FL of 1500mm, which falls to about 1000 with an f/6.3 reducer. This still crops out quite a number of nebulae. Therefore, I would either recommend a fast refractor (ED or APO), or a fast imaging newtonian (note that not all newtonians are made for imaging - some don't reach prime focus and require mods) with a coma corrector (which can cost upwards of 200 USD). A lower magnification is also more forgiving on tracking errors.

[Joshelerry]

Hi do u have some models of newt that can do AP?

[antares2063]

Example of an imaging Newtonian ,I used to own one of these, was taxing my old mount though cos of the weight...

http://www.vixenoptics.com/reflectors/r200-ss.htm

But as many has mentioned before, if this is your first scope you are intending to get, don't plunge too far in the deep end in too soon, humans are generally creatures of comfort, once the novelty wears off, and a day may come when you dread looking at the whole setup and the hassle..

Join a few obs session first, look at different setups in person, get to understand the different mounts and scopes more

Hope this helps

[ivan]

Hi do u have some models of newt that can do AP?

I believe the most commonly used one is the AstroTech (sometimes known as GSO) f/4 Imaging Newtonian, either a 6 inch or 8 inch. Going beyond 10 inches can reduce the fov by a fair bit, as well as tax the VX mount a little too much. For some reason, however, they're almost always out of stock.

If you get a newtonian, make sure to purchase a coma corrector because coma tends to worsen with faster imaging systems. The Baader MPCC seems to be a good buy based on reviews, although you could get the AstroTech Coma Corrector, which is cheaper.

Also, what camera are you planning to image with?