Astronomik, Canon and astro-imaging. Anyone tried Clip-Filters ?

[mickyj]

Thanks. This is not going to be a quick purchase, I am learning and looking, then re-evaluating.

Ultimately I plan to hook my Canon EOS 5D via T mount and do some star gazing with reasonable Moon, planets and Nebula images.
I also aim to fit it with filters and take some sun shots.

[ameerat42]

That sounds like a good plan, Mick.
Am.

[ameerat42]

BTW Mickey, while looking 4 something else I came across this, and thought it interesting as a price comparison with any other place you might be searching on:
Agena Astro Products. It is "stateside".
Am.

[mickyj]

Thanks for posting the link

[SteveInNZ]

Just in case it's still in the running, I'd just say 'no' to the 4SE. Optically, it's slow (f/13) and the Alt/Az type of mount is very limiting for astrophotography, both for tracking and stability. It would be a good visual only scope as it's easy to setup, has goto and a moderate aperture.

The EQ-3/150mm Newt is quite good and while not ideally matched for photography, would be a great visual setup. Because photography is more demanding, the general rule of thumb is to limit yourself to around half of the mounts' carrying capability. So you'd find it difficult to use that setup for long exposure photography as it is. However, the mount works just as well with a camera and lens instead of a telescope for deep sky stuff. There's plenty of good stuff to be had with 200-500mm focal length.
For the planets, the general technique is recording video and the tool for the job is either a webcam, capturing the video from a liveview DSLR at prime focus or using a point and shoot through an eyepiece (afocal). The telescope would be fine for that, although I think the weight of a DSLR would probably be too much for the focuser.

I guess the bottom line of that setup is that it's a good, complete visual setup. For astrophotography, I think that it would be a great learning setup (and I value that highly) but if you want to move to the next step, it's a 'start over' situation. The mount doesn't have the reserve capacity to take a guidescope which you'd probably need to image at the focal length of the scope that's supplied.

If you're shopping around that budget, I'd be tempted to go for a HEQ5 and a cheap achromat telescope for now. It's not the greatest, but it's fine for looking at the moon and larger planets. Add a webcam to photograph them. Use your camera and lenses for deepsky stuff. As funds and/or desire become more available, look at adding either the Newtonian or something like an ED80 which is a very popular scope for astrphotography. The little achromat you bought initially is an ideal guidescope and the mount will still be within its capability for photography.

Steve.

[mickyj]

Thanks,
No, the 4SE is no longer an option. Pity, I saw a really cheap second hand one. It was great to look into it and work out what it can / can't do as I have learnt so much in a rapid amount of time, through the research. Yes, F/13 is slow. I am looking F/5 and it seems that would be in the most commonly recommended range (F/5-F/6).

Thanks for the EQ-3/150mm Newt feedback. That was the type of info I needed to see. I was worried that a Canon EOS with a Telescope on a Eq3 pro would be too much weight

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The mount doesn't have the reserve capacity to take a guidescope which you'd probably need to image at the focal length of the scope that's supplied.
.

I assume you mean the Camera + Telescope + guidescope is too much weight for the EQ3 ?

[mickyj]

Looking again at the ever expanding $$$, I suspect the Bintel BT200 f/5 HEQ5 Pro GOTO is a good choice.

http://www.bintel.com.au/Telescopes/...oductview.aspx

Putting together what I have learnt. A good GEM (Equatorial Mount) with the ability to hold some decent weight, a Goto system for locating stars and a good apperature (F/5 - 200mm) is the go. A good Refractor is the go but a Reflector will work fine.
If I get a kit, I will likely get the Tube rings included. I would still need to source a power supply for the Goto mount stepper motors and a counterweight if the setup is unbalanced. This kit also includes an extension tube, 1.25" ND Moon filter and 2 eye peices. Buying all this seperatly really adds up.

This is starting to look expsnsive but cheaper than putting this together bit by bit.

[ameerat42]

Mickey, it can be a$tronimical, all right (grin).

Looking at this scope setup, two things come to mind:
1) The connection of the scope saddle to the mount is by a single steel (sliding to redistribute weight) rod of modest size. In addition, how firmly does the saddle hold the tube?
2) The "straight-through" finder scope and its position would make for much head-butting against the tube, causing in turn, much head-butting and cussing as you knock it out of position (grin).

Apart from these two point, the rest looks good: f/5 and 1000mm is not a bad combination, and 8" diam starts to give you better resolution - at least potentially. Also, the rest of mount looks sturdy.

But don't 4-get the two points above, because any weakness is going to be noticed no matter how good the rest of the system may be.
Am.

BTW as an aside: I'd gladly pay the likes of this money if I could get something that ticked all the boxes. If you can, go and give it a shake and see how it goes.

[SteveInNZ]

Mmmm... Now you're cookin'

That's a nice setup. That is a manageable sized scope and would keep you going for a long time. It has a reasonable focuser too.
For a power source, grab a jump starter pack from Super Cheap Autos.
The connection point that Am mentions is called a dovetail and there are two standard sizes (Vixen and Losmandy). That is the smaller Vixen style. If you move up a price bracket, you'd start seeing the larger ones. I don't think you'll have any trouble with the Vixen.
I agree about the finder. Straight through is a pain. I don't use a finder at all now and much prefer a green laser pointer. I know you guys have some restrictive laws with them so you'll need to check that out if you are going to get one.

OK - So the bad points. It's a fast Newtonian so it will suffer from an optical aberration called coma which gives you egg shaped stars towards the outside of the frame. There is a solution called a "coma corrector". More $$$. You'll also need to learn how to (and possibly buy some aids) to collimate the mirrors. Scopes like that are quite fussy about collimation. It's not overly difficult but it's something to learn and a time consumer.
As it is, you'll have to use it "unguided". That means that you have to spend quite a bit of time setting it up to get the polar alignment as close as possible. Again, it's not difficult but is something to learn and something that takes time at each setup.
I have a Celestron equivalent of this mount and 950mm fl refractor and do 1-2 minute exposures without guiding.

In order to do longer exposures at that focal length you need to get into guiding which is another leap ($$) but will just be an add-on to what you have. Then you'll be capable of producing some stunning images.

IMHO, the bottom line comes down to you and how you cope with learning curves. If you're a "jump in the deep end and stick with it" person then you'll get a lot (of both frustration and reward) out of that setup. If you need see some results for encouragement, I would probably suggest the ED80 route.

You can always give Bintel a call. They can be quite helpful.

Steve.

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I've posted a picture in the Astro photo section taken at 950mm unguided, just to whet your appetite.

Steve.

[mickyj]

Mickey, it can be a$tronimical, all right (grin).

Thanks, I laughed

It was very witty of you.

I see exactly what you mean about the finder scope. I might be able to use my cheap achromat as a guide scope as suggested by SteveinNZ. It is very light and would not hinder the mount (Weight wise) at all. It would just need some thought. There were two solutions, F/4 at 800mm or F/5 at 1000mm at Bintel. I suspected the F/5 at 1000 mm would be better. Unfortunately I am not close to a Telescope shop, so this makes it hard to see what I would be buying

With point 1) I assume you are worried that the weight in the saddle might make the rod slide back a little and hence ruin any stability in the photographs ?

With the saddle's actual grip in the tube ... I only have the photo at http://www.bintel.com.au/Telescopes/...oductview.aspx to go by.
2 x tube straps. The straps look to be a fair distance apart and the straps them selves look fairly thick. This should give it stability, not sure about strength. I guess I could start with these as the default straps and look at another accessory for a better connection later, if they don't work out. Is there something that does a better job you can link in so I can take a look ?

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The connection point that Am mentions is called a dovetail and there are two standard sizes (Vixen and Losmandy). That is the smaller Vixen style. If you move up a price bracket, you'd start seeing the larger ones. I don't think you'll have any trouble with the Vixen.

I used Google images to search for "Vixen telescope dovetail" and "losmandy telescope dovetail" and now completely understand what you are talking about.

... Yes to the Green lasers ....Laws are laws

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You'll also need to learn how to (and possibly buy some aids) to collimate the mirrors. Scopes like that are quite fussy about collimation. It's not overly difficult but it's something to learn and a time consumer.

As it is, you'll have to use it "unguided". That means that you have to spend quite a bit of time setting it up to get the polar alignment as close as possible. Again, it's not difficult but is something to learn and something that takes time at each setup.

In order to do longer exposures at that focal length you need to get into guiding which is another leap ($$) but will just be an add-on to what you have. Then you'll be capable of producing some stunning images.

For those that are hearing "collimation" for the first time (Like me) http://www.skyandtelescope.com/howto/diy/3306876.html

With your "unguided" comment, I had believed the Goto would take care of tracking etc after I manually found the best polar alignment? I thought this Bintel unit included the items required and there would be no extra $$$.
Can you clarify as there is likely something I have overlooked


>Edit

Hmm, I see what you mean by guiding. It seems most Autoguides can be added on later. http://www.bintel.com.au/Astrophotog...oductview.aspx
The ED80 puts the cost outside of my reach. The Autoguide will need to come later.

I take it with a Goto system, I can get it pointed at the celestial pole, use the goto to locate my target, turn on some form of tracking in it and it will start the motors and move with the earths movement.
Does the autoguide just make it more accurate ?

[ameerat42]

Quite a little sub-forum, this thread. It's good to have your input, Steve.
(An expansion of the "Ta" button.)
Am.

[SteveInNZ]

I take it with a Goto system, I can get it pointed at the celestial pole, use the goto to locate my target, turn on some form of tracking in it and it will start the motors and move with the earths movement.
Does the autoguide just make it more accurate ?

Yes. That's it exactly. The latest version of that goto system helps you align to the pole. It will slew to a star and tell you to center it. You do that a few times and it works out the error and then tells you to center a star with the adjustment knobs.

The two terms "tracking" and "guiding" aim to do the same thing (follow the motion of the stars) but do it in different ways.
Tracking relies on having a good polar alignment and then it runs the motor at exactly the right rate to counteract the Earths rotation. That's correct in theory but doesn't cater for things like refraction from the atmosphere or misalignment between the scope and the mount.

Guiding does it by using a camera and computer to look at a star and repetitively move the mount a tiny bit to keep it positioned in exactly the same place on its chip. It doesn't rely on the alignment and things as much as all of the errors have the same efect on the guidestar as the target.

A simple analogy would be driving a car down a straight road with your eyes closed (tracking) or eyes open (guiding). If you start off pointing in the right direction you'll be OK for a short distance but really, having your eyes open is the trick.

Steve.

[mickyj]

Quite a little sub-forum, this thread. It's good to have your input, Steve.
(An expansion of the "Ta" button.)
Am.

Yes, this post is going to be an awesome reference. I have been looking all over the internet for the sorts of information in this post and have been unable to find it.
Now we all have it as a record of exploration and teaching

[SteveInNZ]

Don't forget that other people will have different experiences and therefore different opinions. I've just shared mine and I'm far from an expert.

[mickyj]

The more I read, the more I like the Skywatcher HEQ5 PRO mount. It has high quality stepper motors (64 micro steps), upgraded mother-board, ST-4 autoguiding port for astrophotography and it is supplied with a Synscan GOTO handset.

I think I have sold myself on the idea. Now I just need to find the $$$ and start learning. I work in IT so taking on new things and learning them is something I have to do daily. At least this time it is going to be something less IT related

[mickyj]

Thanks to everyone for the information supplied so far. I have come up with another question and I suspect only those with expeariance can answer this one.

For Astrophotography, What would be better, a Reflector at 200mm x 800mm f/4 or one at 200mmx 1000mm f/5.

They are the same price

[SteveInNZ]

The focal length doesn't make much difference. There will be things that are too big or too small, no matter which you choose.
IMHO, the biggest difference in focal ratios would boil down to needing a coma corrector for f/4 and wanting one for the f/5. The difference in exposure time is the same as it would be for lenses of the same focal ratios. ie. about 60% longer. In reality, that doesn't matter either because no matter what, you'll always want more.

The most important thing to ask/check is that you can achieve focus with a DSLR. Most standard newtonians don't allow you to wind the focuser in far enough for photography. Some are sold as "Astrographs" (designed for photography) which are suitable. Others may require a lower profile focuser and/or moving the main mirror up the tube by an inch or two.

Also keep an eye on your weight budget too.

Steve.

[mickyj]

The focal length doesn't make much difference. There will be things that are too big or too small, no matter which you choose.
IMHO, the biggest difference in focal ratios would boil down to needing a coma corrector for f/4 and wanting one for the f/5. The difference in exposure time is the same as it would be for lenses of the same focal ratios. ie. about 60% longer. In reality, that doesn't matter either because no matter what, you'll always want more.

The most important thing to ask/check is that you can achieve focus with a DSLR. Most standard newtonians don't allow you to wind the focuser in far enough for photography. Some are sold as "Astrographs" (designed for photography) which are suitable. Others may require a lower profile focuser and/or moving the main mirror up the tube by an inch or two.

Also keep an eye on your weight budget too.

Steve.

As always ... Sage advice. Thankyou !!!

[ameerat42]

Hmm. Just saw this. Yes, agree with what Steve said.
Here's what I'd add in answer to the Q on which focal length: With the shorter FL you will have a wide(-er) field scope, and with the addition of a barlow/coma-correcter (they used to be combined for wide-field scopes) you will end up with say, FL of1600mm. With the longer one as your choice, well..., yes..., you can get (4-gotten what they're called, so) "field-wideners". But from what I remember, they're not so practical as having a wide field to start with.
Am.

[SteveInNZ]

A handy (free) tool for checking out how big your images will be is CCDCalc. You can setup your camera and telescope options and pick astronomical objects and it will show you how big they'll be in the frame.
You're opening up a can of worms here Am.
Coma is an error that is inherent in Newtonians and is determined by the focal ratio. Stars in the middle are round and stars at the outside look like comets. If you have an f/4 telescope, the diameter of the circle on the image plane with round stars is about 8mm. For an f/5 scope, that's 12.5mm, f/8 is 32mm, etc. The sensor of a crop camera is 15x22mm so coma is a non-issue for an f/8 telescope but is substantial for a f/4 scope.
A "coma corrector" or the much more expensive "paracorr" aim to just resolve the coma with no change in focal length. Another option is to use a much cheaper Barlow (like a 2x teleconverter) which multiplies the focal length by 2 and therefore the focal ratio for your f/4 scope is now f/8. No more coma but only a quarter of the field of view and longer exposures.

The other optical doo-dad in our bag tricks is the "focal reducer". As the name implies, they are the opposite of a barlow lens and reduces the focal length. They are most commonly used with Schmitt-Cassegrain Telescopes (SCT). The SCT has the advantage of aperture and focal length in a physically smaller package than a Newtonian. However, they are usually quite slow at f/10. eg. A 8" SCT has a focal length of 2032mm. If you put a 0.63x focal reducer in the image train, that becomes a 1280mm f/6.3 telescope. SCT's don't have issues with coma but do have a curved field so the focal reducer is usually designed as a reducer/flattener to fix that at the same time. There is also a 0.33x reducer for SCT's and it makes it a fast f/3.3 but it's not suitable for DSLRs.
There are also reducer/flatteners for refractors and they're usually matched to a particular focal length and ratio.

It looks to me like the f/5 scope is coming out ahead of the rest at this point and while a coma corrector will be in your future, I don't think it will be a limiting factor for a while.

Steve.