Reserching a new scope setup

[markab]

Hi everyone

I’m sure these are the same queries that have been asked many times before so sorry for the repartition. I will be grateful for any advice you can offer.

I have been interested in Astronomy for many years and have a small 4” reflector. I am now looking to move on to a more advanced setup with a budget of up to £2500.

I would like to try astro imaging and the setup would have to be portable.

My choice so far is :-

Orion SPX 300 f 5.3

EQ6 pro ( without goto )

Canon 550d

I realise that the mount is not light weight and is nearly as much as the scope but I hope it will be better for imaging work and will take any reasonable scope upgrades and attachments.

I’ve chosen a Newtonian over a Cass or refractor because of the better cost per inch of Ap. I may be wrong in this choice since most imagers seem to use refractors (I cannot recall seeing a CCD attached to a reflector.)

I know I cannot expect equipment to do too many things but the choice of camera is made partially for other use too.

Can I use the video function of a DSLR as I would an adapted webcam ?

The canon doesn’t have an articulated screen, is this not important for astro imaging ?

Why is a faster focal ratio scope better for deep sky photos ?

Thanks for any comments you have.

Markab

[Jdavies]

With astrophotograhy your are going to need as a must a motor and would strongly incourage getting the goto eq6 otherwise you will not get enough light into the camera to get decent images without the object moving. also the is alot more to takin pictures then first seems. it can get very expensive very quickly. do your research and don't rush into a buy take your time.

[ollypenrice]

EQ6 yes, but without GoTo, no. Why? Two reasons;

- You will soon be imaging things that are entirely invisible in the EP. You don't want to lose half your precious night in search of them!

-The LAST thing you ever want to do in imaging is take you camera on and off and exchange it for an EP. You lose critical focus (which takes a while to find. 5 minutes can be optimistic.) Also if you take off your camera you will need to reframe it exactly - another 10 minutes lost - and you will no longer have reliable flats. You need to reshoot these if you disturb the optical system.

Sp please do opt for GoTo or you really will kick yourself!

Why is f ratio so critical? In imaging f ratio is what determines the intensity of light concentrated on your chip. It is the ONLY thing which determines this. Aperture has nothing to do with it, something which is counter intuitive and which many people cannot bring themselves to believe. But if you take a big 14 inch SCT and use it at f10 it is very slow (Low light concentration, long exposures.) Fit the same 14 inch with a Hyperstar conversion to shorten the focal length and lower the f ratio to f2 and it becomes a blisteringly fast f2, needing very short exposures. It has not changed in aperture though. That's why f ratio matters so much.

So f ratio wise your choice of Newt is good. But there is a downside. Newts do not give a flat field and need coma correctors to get one. They are big, bulky, wind-prone and more tricky to balance. You need a very solid focuser and tube to keep things orthogonal and you need to collimate them each time. (More time lost). On this forum Mike gets fantastic results with a large Newt but they are much harder work than refractors and imaging is quite hard anyway!

I may be wrong but I get the feeling that you believe in your heart that a bigger telescope will get you better results. This is not necessarily so. First decide on the kind of focal length you want because this determines your field of view, wide or 'zoomed in.'

(Shorter is much easier to guide than longer and lots of targets are large.)

Then think about your options. For a focal length of about 500mm I dithered between a superfast 180mm Tak Epsilon corrected Newtonian (f3.3) and a much smaller 85mm Tak refractor (f5.3), fast but not as fast. I went for the little refractor because of the ease of focus, balance, freedom from collimation, stability in the wind and on the mount generally and because I personally dislike diffraction spikes. This last point is not just aesthetic; you can't combine images from two scopes if one or both have diffraction spikes.

But the case for the Newt can also be made and, I don't doubt will be made well, by others.

What about the superb SW MN190 f5 Maksutov Newtonian? This is a bargain and has great optics. However, the easiest system is with a small fast refractor. A recent M31 of mine is on the Deep Sky board at the moment if you want to check it out.

Olly

[bish]

Out of interest, does a GOTO track better than just a dual drive? I was thinking of upgrading to HEQ5 (from EQ5) but discounted GOTO as I like to find things. The reason is that i may be buidling/buying an observatory (ie converted shed) and as I wouldn't have to lug the kit around thought I would go for a more stable mount with a view to perhaps trying some basic imaging.

[ollypenrice]

Out of interest, does a GOTO track better than just a dual drive? I was thinking of upgrading to HEQ5 (from EQ5) but discounted GOTO as I like to find things. The reason is that i may be buidling/buying an observatory (ie converted shed) and as I wouldn't have to lug the kit around thought I would go for a more stable mount with a view to perhaps trying some basic imaging.

No, I can't see why it would make any difference. The periodic error of an EQ6 is pretty large, maybe six to ten times that of a premium mount, but it autoguides out very well, hence its great popularity amongst imagers.

Olly

[markab]

Thanks for your advice.

Olly, you’ve given me a lot to think on.

You didn’t take that pic of yours from my back garden nor the South of France. That was taken from the top of Everest on a clear night. Can you tell me what setup you used. They’re stunning images. Thanks again.

[ollypenrice]

Thanks for your advice.

Olly, you’ve given me a lot to think on.

You didn’t take that pic of yours from my back garden nor the South of France. That was taken from the top of Everest on a clear night. Can you tell me what setup you used. They’re stunning images. Thanks again.

Thanks! Yes, South east France with Tak FSQ85ED and focal reducer (focal length 328mm) on EQ6 Synscan Pro at f3.9. Atik 4000 CCD camera. Only about 4 hours of data as well, which is not a lot in imaging terms.

Sky not at its absolute best.

But Martin took a winner of M31 from Chesterfield with his FSQ106 refractor. Okay these are very expensive but the result you would get from a cheaper refractor would come close.

Olly

[bish]

No, I can't see why it would make any difference. The periodic error of an EQ6 is pretty large, maybe six to ten times that of a premium mount, but it autoguides out very well, hence its great popularity amongst imagers.

Olly

Thanks Olly.

[Jdavies]

Go for goto its worth it