new scope question

[james]

I was looking around at getting a new scope, and was wondering is the the old saying "get the largest Aperture you can afford" still applies with Astrophotography.

I Know large Aperture = more light, which will mean more detail when viewing, but does this still apply to astrophotography because you can increase the amount of light with longer exposure times.

Therefore I was considering a small Apo refractor  either a William Optics Megrez 72 or a skywatcher equinox 80mm refractor. My logic being that they both should have good optics (ED Glass) and due the the shorter focal length a larger field of view, which may be better for imaging some Deep sky objects.

Also very small so good as a grab and go scope, Or would I be better off spending the money on a larger Aperture Maksutov or Schmidt cassegran.

What do you think

James

[Rick]

There's also the shiftability factor (unless you're setting up a permanent observatory at home). There's no point in getting a scope that's too big to take to your favoured observing sites.

[Mike]

If ti was my money i'd go for the Megrez. It is better optics that the Skywatcher and just the right size to be portable and to enable imaging a long list of objects. A wider field of view is also more forgiving on guiding errors and is far easier to learn with.

[Ian]

I've got the Megrez 72 ED APO and mechanically it's a fantastic piece of kit. I'd be inclined to believe it's no slouch either optically but I've not yet managed to really push it. It's a scope I would never have bought five years ago. It would have been far too expensive to justify, and I couldn't have afforded the astro cam to do it justice. That no longer applies, for either bit of kit.

To get a long focal length scope to track and guide accurately for astro imaging, you need to spend big bucks on a mount and guiding system (or get a camera with a big sensor like a DSLR like MarkS has) but the new Synta mounts are nothing like they were five years ago and can do sterling work on focal lengths up to around 500mm or so, probably even longer. Despite the increase in performance their costs have not risen anywhere near as much in comparison.

So small scopes are capable of fantastic images, the cameras and mounts are affordable, they won't break your back when setting up and give photos good enough to get published (see JohnP for that ) When you get a dose of aperture fever, there's the 12" lightbridge you can borrow. That'll cure that one...

[james]

Thanks for the advise

I was thinking of the EQ5 Synscan Mount (GOTO which I hope would be good enough for guiding as the pro versions are a lot more expensive.

As you say I have got a lot of learning to do and therefore easy of use is an important factor.

Now all I need to do is convince 'she who must by obeyed' that this is a good use of our limited funds, I fear this may be harder than finding and imaging the faint fuzzy's them selfs.

James

[Rocket Pooch]

Hmmm, ok I feel our advice need to get up to date here on the mount and scope/mount front.

The HEQ5 and HEQ6 mounts are fine, I image with mine, an old one up to 2 meters most of the issues you read about here relate to guiding or the use of software, flexture etx not the mount.  So personally yes if you can buy an AP900 or Gemini G32 then that would be the way to go, but if you have about £800 to spend on a mount the EQ's are good.

I have an HEQ6-Computer Controlled and Sphinx SXD, I bought the SXD because it light and cool, the PE of both are +-20 and +- 16, I have not used the SXD for imaging yet, but I did measure the PE and its better than the EQ6 so it should be ok.

We have people here with expensive mounts G11 & Takahashi who also have issues with guiding, its not the mount I think it probably something else.

What I suppose I'm saying is if you are on a budget, go for an HEQ6, Fay has one and she guides for 10 minutes without any issues, well that is up to the point where the software goes iffy.

Personally I put a lot of time into learning the software I have for imaging, I guide with either K3CCD tools or AstroArt with not major issues, although with AstroArt you need to do some calculations to get it right.  But you do need to learn what you are doing, just plugging it is and assuming its going to work is not the case, if you see me here going "oh I have guiding issues" its because something is bending or my mount needs adjusting, not the software.

As for the scopes, my ED80 is much better optically than my ZS66, by a mile, and therefore I use it, the ZS66 is however mechanically brilliant.  From reading up on the Equinox Skywatcher scope's I don't think the extra cost is worthwhile.  There's a guy here Paul Whitmarsh who has an ED80 with a William Optics crayford this is very nice and I'll probably put one on my ED80 one day.  One point ot note, you can also put a focal reducer on say a ED80 and bring it down to the WO72 and get more light capture, just a though, if you go the other way the F no get's higher and therefore you capture less light.

From an Imaging point of view your Signal to Noise ratio is the key thing you are after, good optics are nice as well, if you can get a faster scope with larger appature then good, at 750mm in length your into 6" Newtonians and also the Refractors.  To give you an example of how critical this is, if you get an F5 scope say 6" F5 newt and image against a 80mm ED80 F7.5 your images will be half the exposure to get the same results, this means one of two things, a) you can image for the same time and go deeper, b) you can image for shorter times and guiding becomes less critical.  You jut need to get your head around things like collimation.  Actually I was thinking of buying a second hand 6" Newt for £199 as an astrograph.  However, you cannot normally put a focal reducer on a Newtonian and you often need a comma corrector.

The issue with Mak's and SCT's tends to be the focal length and also dew issues, the need for critical guiding and also the need to get the collimation and focus right.  Again I have an 8" RC SCT, great scope for imaging small targets, focus is critical.  You need to be careful here because they tend to be heavy and also if you look at some of the postings here the secondary can be an issue and also flat field issues can be an issue.

Big thing everyone else has missed, a) if you can't guide at 400mm, give up your not using the software right, or you have a crap mount, b) no one has advised you that you need to consider what you are imaging, although you question seems to relate to wide field and not planetary imaging, and c) the overall budget, I'll give you an example.


Megrez 72        £299
Heq6 Skyscan   £639


You will then need to get a camera, maybe a dual bar, guide scope, filters, filter wheel, power supplies, etc etc etc.  SO depending on what you want to do add someone between £1000 - £4000 on top.

Actually it was interesting reading everyone else's comments, they all seem to say buy WO, they are nice, but go and read the reviews especially against other ED scopes, the point missed is that mechanically they have the edge, visually at 150x - 250x magnification who knows, I like my ED80, I do not like the ZS66 because its not as good visually and has field curvature, but it does go in a small bag.  Personally I doubt you will notice the difference, from an imaging point of view as long as there is no distortion over the size of the CCD pixel you will not notice the difference.

Portability, great get a Megrez 72, but remember if you invest heavily in a AP900 you will be carrying around 50KG of mount.

Fay, John, Robert & Mark what do you think, you do more imaging than anyone else here.  What would you do again?

For example:

CCD v's DSLR
SCT v's Refractor
Guiding thoughts?
Favourite software?

Also consider secondhand, astronomers do not often chuck their scopes in fish pond, dent them or drop then on the floor (appart from Fay and I) so they tend to be in good nick.


Chris


P.S. Off to Wales tonight, it will be clear in Bromley.
P.P.S. Here's a couple of images using a cheap nasty Skyscan mount and cheap nasty ED80, taken in the UK with a second had CCD camera, one in an observatory one in the field, see what you think.

http://farm4.static.flickr.com/3085/2584189491_63c45490e5_b.jpg
http://farm4.static.flickr.com/3237/2482390969_0e9d38d65e_o.jpg

[Rocket Pooch]

Thanks for the advise

I was thinking of the EQ5 Synscan Mount (GOTO which I hope would be good enough for guiding as the pro versions are a lot more expensive.

As you say I have got a lot of learning to do and therefore easy of use is an important factor.

Now all I need to do is convince 'she who must by obeyed' that this is a good use of our limited funds, I fear this may be harder than finding and imaging the faint fuzzy's them selfs.

James

James ensure its the SkyScan version not the non-SkyScan they have different motors and gearing.

[Rocket Pooch]

James,

Have a look here today there's lots of ZS stuff http://www.cloudynights.com/ubbthreads/postlist.php/Cat/0/Board/refractors/page/0/view/collapsed/sb/1/o/all

[james]

The mount I was looking at was this one

http://www.harpersphoto.co.uk/product/eq5_synscan_computerized_mount_system_981_/

It does not mention skyscan (and is cheaper) so I assume it not have the better motors. I was told it had better moters/gears than the neq3.

http://www.harpersphoto.co.uk/product/neq3_synscan_computerized_goto_equatorial_mounting_system_106_/

I felt the EQ6 would be to heavy and I need to trade stability with portability.

Many thanks for your reply.


James

[JohnP]

Bloody hell Chris - epic...! did you get paid for that review/ report...

James - I went the 'cheapo' route - I started with a push to scope & webcam's which I subsequently modified myself - I have now progressed to a proper astro camera (albeit one of the cheapest you can get Atik 16ic) & an EQ6Pro mount.

There is a lot to be said for spending £40 or so on a cheap webcam - you learn an awful lot about imaging, focus, finding objects FOV, focal lengths etc. etc. so if I were starting out again I would probably still invest in one of these - There is a real frill/ buzz about getting your first images of the moon, saturn, jupiter etc. (don't expect to image much more with a std webcam though).

I then spent a few years modifying webcams & although I got some great images along the way for not a lot of money & learnt loads I think if I had to do it all again I would just jump in & buy something like the Atik 16ic I have now. They are only about £300 & you can get cheaper 2nd hand.

WRT mounts I would definitely go for a fully computerized goto - I spent too many hours trying to find DSO's (rather than imaging) when I started out with my push to scope. I can recommend EQ6Pro or its smaller version the HEQ5.

I think scopes are really down to personal preference - some people prefer refractors, other relectors or hybrids. I currently have a WO ZS66 & Intes Micro MN56 (I love the Intes - very solidly built, reasonable aperture & not too big). The ZS66 does have field curvature problems especially with a large area CCD like a DSLR. As Chris pointed out I think the ED80 is a great scope for the money.

James you need to remember that if you get serious about this you will need two scopes - one for imaging & one for guiding + filters etc.

WRT software - again down to personal preference - I think K3 is a great acquisition/ guiding package & not too expensive - you should search around as there is lots of free stuff... i.e. DSS, Registax etc.

Best bet would be if you could make it to the next DSC in August - hopefully there will be lots of people there with lots of different setups etc. to look at..

Cheers & HTH - John

[RobertM]

That's very good advice Chris.  I would just reiterate what you have inferred that it's best to start off with shorter focal length scopes as the guiding is MUCH less critical.  My guiding problems either relate to a 1.5 pixel shift (at 1400mm f/l) or it not working due to either me (most likely) or the software.  If I was imaging at less than 1000mm then it wouldn't be noticed.  If you try to image at f/10 with an 8" SCT or Mak with a cheap mount then you might get lucky but on the otherhand the frustration of isolating the problem if it doesn't will have you pulling your hair out !

I can't really comment on the mounts mentioned here but I have had a Vixen GP-DX and they are very good for the money.  I think the mechnical tolerences of the Jap equipment is much finer and (more importantly) consistent.  There seems to be more variability with the Skywatcher mounts but they are much cheaper and they are getting better.

As for scopes ... I had an Equinox 80 and sold it, optical quality was good but it is bloody heavy for an 80mm - about twice the weight of the older ED80.  The FD 72mm looks like a good compromise, people like them.  Also look at something that is going to give you lots of light gathering power for DSO's e.g. the GSO 8" F4 Newtonian.  Newtonians give exceptional performance on axis but you will need a Coma corrector with almost any CCD camera.  Fortunately these are relatively cheap and can turn them into excellent astrographs for DSO work.  Another side effect of a Newt like the GSO is that it's relatively lightweight so won't put too much burden on your mount.  One of the disadvantages of short focal lengths is that they are a lot more critical of focus position (ideally need a focuser with a 10 to 1 reducer) and collimation (alignment of optics).

Different people have different opinions but if I was starting out now from scratch with the experience I've collected then it would be a 70-80mm f/5-f6.5 refractor and either the GSO 8"or Vixen R200SS Newtonians (both are F/4) with Coma corrector.  With those scopes mounted piggyback you could either get away with a lighter mount or (preferably) go for a heavier mount (HEQ6 ?)and be well within it's capacity.  Neither would be that special for Planetary work but then you could later get a Mak Cas for Planets (I think skywatcher do a 6-8").  These scopes would be much less critical of the precision of your mount and give a lot of enjoyment to boot.  Having two scopes would allow you to image with one and guide with the other (that's what I do at the moment) though there is a bit of faffing if you want to change them over !

For ccd/filter wheels etc I would start off without a filter wheel, either with a mono or colour ccd and a light pollution filter (either an Astronomik CLS or Baader Neodymium).  You will find 1.25" filters much cheaper and Baader the cheapest.  There is no doubt that the cooled CCD will give you the best images for the forseeable future and second hand are very good value.  If going that route I'd recommend going for a 1/2" chip size such as an Atik or the Starlight SXV-M7 (mono) or colour (much less sensitive) equivalents.  Just look in the gallery at what John/Fay have done with theirs.  For guiding I would recommend one of the DMK USB2 cameras, they make excellent dual purpose Planetary and guide cameras.  As an alternative to the cooled ccd camera you could go down the DSLR route, modified for Ha they make good Astro cameras.  They might also be a more flexible option coupled with the F/4 Newt or smaller refractor and have the advantage that you could add a set of prime focus lenses and small mount to take on holiday.

At the end of the day you will find that no one telescope/camera combination does everything perfectly (at least not at our end of the market), that's why you may need a range of equipment to cover whatever interests you may have.

If you can wait till the DSC then you will see the whole range of equipment that members have and how they operate together with S/W - there's no better experience than seeing equipment in action (I use that word loosly!).

Whatever you do and advice you take, make sure you research your options and define what you want to achieve - widefield/Deep Sky/Galaxy/Nebulae etc. and start simple.

Sorry I was going to keep this short but I ended up rambling on !

Robert

[MarkS]

I use an SCT - a Celestron C11 on an EQ6 Pro mount - focal length 2800mm.  I went straight from a small cheap Newtonian to an expensive SCT, so I don't have much experience with different scopes.  But here are my own comments on the SCT.

Its an excellent scope for planetary imaging and for smaller "fuzzies" because of it's wide aperture and hence high resolution

The field of view is very narrow - this restricts the range of objects you can reasonably image.  Even over this narrow field of view, illumination is not very even, so shooting flat frames is important.

To capture the whole FOV requires a large sensor - either a DSLR or a very expensive astro-camera (the cheaper astrocameras have small sensors)

The generally bad seeing conditions in the UK mean you can very rarely use the high reolution at anything near its full ability - stars will always look like big blobs on your image until you scale the image size down by 2 (or 3).  Having said that, binning images down to a smaller size helps improves the signal to noise ratio enormously - this actually makes using a  DSLR a good proposition on the SCT

Due to the long focal length, guiding is very critical - it shows up the smallest of guiding errors

Dew is a huge problem on the front optics - in the UK I can very rarely image without a dewheater and dew shield.

It needs frequent collimation - probably because I transport it around too much.

The large size of the tube makes it more susceptible to windy conditions.

It's also heavy - so lifting it onto its mount is always a worrying procedure.

For the above reasons I would caution against it as a beginners scope.

[Rocket Pooch]

wow lots of words here,

[Daniel]

I'll second that about not going straight to the SCT, I've been getting a lot more fun and better images out of my 80ED lately despite the much lower light gathering power

[RobertM]

It's all your fault Chris, you wrote the first chapter ...

Hope you took your wellies with you