Equipment ideas

[ChrisEdu]

I was talking to FLO earlier today and metioned that I was thinking about what to buy next, what with Christmas and my birthday being so close together. They suggested that, as you folks like spending other people's mony, I should post on here.

So, given a budget of between £1k - £2k what scope would you buy?

I think my main interest is heading in the direction of looking at nubulae, although, I also enjoy looking at planets too. Not sure if I want to get into imaging, it's a possibility but probably at a later stage.

Over to you folks - spend away!

p.s. I might consider extending the budget a bit if there was a good enough reason to do so.

[Ben Ritchie]

If you're sure you want to be 100% visual, i'd be looking at one of the Skywatcher 12" dobsonians (probably the 'flextube' truss one) and some decent eyepieces. That can cover anything from <£1k if you're careful with the eyepiece choice to the full £2k if you go down the Nagler/Ethos route...

If you think you may want to start imaging, i'd probably look towards an EQ6 mount with a 8" or 10" Newtonian OTA, which will do well for visual now but offers a good route into imaging later.

[ChrisEdu]

That sounds just like what I was thinking along the lines of doing.

[Keagle]

A note on the 10" Newt on the EQ6. I had one before the VC and for me, with my observing location not quite out of the door and trying to setup as a one-man show, everytime I wanted to use it was a pain.

It is do-able, but requires patience

If you have a obs like Yfronto then I'm sure it's fine. But I wouldn't like to set it up for imaging all the time.

The 10" newt from Skywatcher will also require a third counterweight on the EQ6.

Kurt

[Ben Ritchie]

The 8" GSO Newt that Bernard sells would be a good visual/imaging choice, fairly light and easy to handle on the EQ6 (you can use a HEQ5, I did, but it's a bit too close to the limit IMHO, the EQ6 would be a better choice). You'll need the MPCC for imaging with anything but the smallest of CCDs - and all DSLRs - and for visual too if you're picky about coma, some are, some aren't.

I'd still go down the Dob route if you decide you're visual at the moment though, for looking at nebulae the extra light grasp of a 10" or, ideally, 12" really helps.

[ChrisEdu]

What about the Sky-Watcher Explorer 300P on an EQ6 PRO SynScan?

[Keagle]

If you have a permenant setup then yeah, mainly for imaging as it doesn't matter where the focuser is orientated so much. For visual, the eyepiece is going to be a pain to get to. That wont be a lot of fun to setup each time, though. And a step for the eyepiece will be needed...

Aside from the size and bulk, it is a very nice scope But I think it will be a lot of hassle. The dob will be far easier to setup, far far farrr easier, but if you want to do imaging we need to look at some more choices .

Kurt

[Ben Ritchie]

What about the Sky-Watcher Explorer 300P on an EQ6 PRO SynScan?

I wouldn't start there with imaging, the focal length's longer than ideal really for starting out and it's just too cumbersome. And for visual only i'd still think the dob mount is better, just for simplicity.

I'd suggest having a careful think about what you want to do and how much you have to spend (there's a big difference between £1k and £2k!). At the upper end of the budget there's room for nice imaging and visual setups, and IMHO separate visual (10" or 12" dob + eyepieces) and imaging (maybe HEQ5/EQ6 + 80ED + DSLR?) setups are the way to go. At the lower end you need to be careful not to try and do both in one setup but end up doing neither well, so you may well be better off thinking carefully about what you want to do and buying one good setup for that and leaving the other until later.

[Viking]

Here is a link to the Dob page on FLOs site. Couple of interesting quotes on the larger scopes.

http://www.firstlightoptics.com/products.php?cat=31

With the dob you don't have to bother with an equatorial mount at this stage, they have their own. The finders don't look that great, but its an easy job to replace them. You will have plenty of £1ks left to purchase other goodies.

John

[ChrisEdu]

Ok - let's assume that I'm going to want to get into imaging, whilst still wanting to be able to do observing of planets and DSOs. I already have a DSLR so I could use that to start with. Budget nearer the 2k than 1k.

[Ben Ritchie]

Ok - let's assume that I'm going to want to get into imaging, whilst still wanting to be able to do observing of planets and DSOs. I already have a DSLR so I could use that to start with. Budget nearer the 2k than 1k.

I've kind of said it already, but with a (near)2k budget i'd get...

- Skywatcher 300P dob + cheshire collimator for visual (£500, near enough). Maximum visual bang for your buck, so to speak. Only reason i'd go smaller is if you have issues with storage, want to take it elsewhere regularly ... in a small car ... or need to carry it a long way around the garden. In that case the 250px solid tube or flextube are good options.

- EQ6 + 80ED + Bern's QHY5/ST80 guidescope package, for use with your DSLR. Uses most of the rest of your budget, but a great imaging setup, brilliant value for money, the EQ6's is 'future proof' if you buy a bigger 'scope at some point. This will take you a long way in imaging before you ever need to upgrade.

If I was starting again knowing what I now know the above is undoubtedly how i'd spend my money...!

I don't have the EQ6 (have a HEQ5 instead) but I think you're pretty local to me so you're welcome to come over and see what some of that stuff looks like etc.

[Neon]

My experience of imaging is fairly limited, but what about the new Skywatcher Astrograph:

First Light Optics Mak-Newt

It's only 7.5", but should be a fairly good compromise between visual and imaging, apparently designed with DSLR's in mind. Stick it on an EQ6 and you'll have a rock solid setup with some change left over for eyepieces and extras.

Just my tuppence worth.

[Doc]

2k I would buy....

Visual...

300P dob

Full set of Baader Hyperion eyepieces

Imaging...

EQ5 or maybe EQ6

ED80

DSLR

Should come in close to 2k.

[Ben Ritchie]

My experience of imaging is fairly limited, but what about the new Skywatcher Astrograph:

Looks very promising, but it's sufficiently expensive that the Mak-Newt and EQ6 take up most of the budget - there wouldn't be the cash for a visual light-bucket too. So for a £2k imaging setup, yeah, i'd agree (although i'd probably wait a little until its a bit better known, early days yet). But for a setup to cover an introduction to imaging and visual then I think it's too skewed towards the imaging side of things.

[ChrisEdu]

So, no-one would recommend something like a Celestron C11-S GT as a kill both birds with one stone option?

[kniclander]

I bought a skywatcher 10" dob for visual only. I find it a bit too big to carry out of shed in one piece - one reason I bought the 10" not the 12" was carrryability but as I can't carry the 10 I could have got the 12 which is of course bigger (therefore better ) and easier to collimate. having said that the other reason I bought the 10 was price so I couldnt have bought the 12 anyway. I love the 10; you'd love the 12. Don't know about the C11 but you cant beat a dob for set up time.

Apologies for slightly irrelevant post

[ChrisEdu]

I think I want something with a GOTO mount - can't be arsed to spend time finding things!

[Ben Ritchie]

So, no-one would recommend something like a Celestron C11-S GT as a kill both birds with one stone option?

Not for deep-sky imaging, the focal length's far too long. Would be good for the moon and planets with a webcam though.

It also looks a bit under-mounted?

[ChrisEdu]

Couldn't one use a reducer thingy for the focal length?

[Ben Ritchie]

The C11 has a 2800mm focal length, if you want to use a DSLR then you're limited to the 0.63x SCT reducers which will still give you almost two metres of focal length - more reduction comes at a cost of vignetting and/or distortion over the big sensor of a DSLR. Even the 0.5x or 0.33x reducers, which only work with small-chip CCDs, only drop you to 1400mm or 925mm focal length - in contrast, a typical 80mm refractor has a focal length of 500mm or 600mm. The longer the focal length, the higher the resolution and the harder life becomes. It's not impossible to image DSOs through a big SCT, but it's considerably harder than it needs to be.

Like I said, if you try to do everything with one setup then you risk compromising both imaging and visual. The C11 will be good for visual and lunar/planetary imaging, but DSOs ... not so much.

[ChrisEdu]

Why is high resolution a problem? Logic, to me at least, would seem to suggest that that equals more detail. Could you enlighten me further regarding the focal length issue, too?

Cheers.

[Ben Ritchie]

High resolution does equal more detail (although seeing limits this), but high resolution also shows up every tracking error in the mount. For lunar/planetary imaging when you're taking thousands of very short images and stacking them this isn't an issue, as the exposures are much too short to show tracking errors. However, for DSOs, where you want tens or hundreds of seconds of exposure time, it is very hard to image at long focal lengths without the stars trailing.

General advice to newcomers is to aim at an image scale of around 2.5"/pixel - this is roughly what an 80ED + DSLR gives you. At native resolution a C11+DSLR works at 0.5"/pixel. Assuming 20 arcseconds of periodic error, fairly typical for an entry-level GEM, stars will trail by 40 pixels over one worm cycle if you don't use autoguiding. Even if you do, it's very hard work to keep stars point-like.

[ChrisEdu]

What do you mean by 'seeing limits this'?

With focal length, presumeably, like in photography, the longer the focal length, the higher the native magnification? And therefore, a high focal length coupled to a large diameter gives brighter, larger observations? Also, I assume that if one is using accurate for tracking, the f number is less important? Why do some scopes of the same sized aperture have different f numbers (i.e. speeds)? Is it simply down to how the light is reflected within the scope, or are there other factors at play?

[Ben Ritchie]

What do you mean by 'seeing limits this'?

In theory as you go to longer focal lengths you get higher resolution - however, unless you put the telescope in space, you're looking through a moving atmosphere that blurs out detail at scales below a scale called the 'seeing', measured in arcseconds. The telescope I use in Paranal, Chile has some of the best skies on earth, and the average seeing there is something like 0.66 arcseconds. In the UK it's significantly worse, something like 1.5-2 arcseconds I think (dedicated planetary imagers may know a figure).

What that means in practice is that, for long exposure imaging in the UK, you don't see an improvement in resolution once you go above about 1500mm focal length, because your resolution becomes limited by the seeing not by the optics of the telescope.

Planetary imaging is somewhat different. If you collect thousands of very short images you find that because the air is constantly in motion some will be sharp and others blurred. Software allows you to automatically reject the blurred ones so you can work to the best of the night's seeing conditions, not the average, although seeing is still a limitation - some nights will be better than others. However, the net effect is that you can usefully use longer focal lengths for lunar/planetary imaging than you could for deep-sky.

With focal length, presumeably, like in photography, the longer the focal length, the higher the native magnification?

Yes, with the limit that - at the seeing limit - longer focal length/higher magnification no longer becomes useful

And therefore, a high focal length coupled to a large diameter gives brighter, larger observations?

Hmm, assuming you're increasing aperture faster than focal lenth then yes, you get brighter and larger. At constant f/number then you just get larger, not brighter, as the focal length increases. CCD behaves differently to film in this sense, which causes all sorts of arguments online. I'm not going into that

Also, I assume that if one is using accurate for tracking, the f number is less important?

f/number is, in a sense, unimportant if your mount tracks accurately, as you can get any desired signal to noise level by exposing for a longer time. However, in practice you have a limited time to image (due to the weather here, if nothing else) and a mount that can track accurately at long focal length is extremely expensive. So, in practice, the advice is always to go for a 'fast' (i.e. low f-number) telescope working at short focal lengths so that it places fewer demands on the mount. In other words, a refractor or medium focal length Newtonian (e.g. a 6" - 8" f/4).

Why do some scopes of the same sized aperture have different f numbers (i.e. speeds)? Is it simply down to how the light is reflected within the scope, or are there other factors at play?

It's down to the design - a huge number of factors come into play here, especially with refractors, but any design is a complex balance between some good features, bad features and price (...pick two...).

If you're seriously thinking about doing any long exposure imaging, i'd really recommend begging, borrowing or buying a copy of Wodaski's "The New CCD Astronomy". It's a little out of date with regards specific equipment and his idea of "cheap" is somewhat at odds with the rest of us, but it covers the fundamentals very well and can save you plenty of cash and frustration.

[marksward]

+1 for the 300p on an EQ6 - not that I'm biased

Gathers light great and simple to use for visual once you know roughly where south (or north for you) is. Not the lightest thing to carry around (esp if you're not just using the backyard). Save some money for collimator and prob a lens or two. I'm just waiting to get some more cash together for a couple of lens options.

dobs are great and simple, but for me its easier to keep a target in the sights by tapping the button on the EQ mounts handset than to try to GENTLY move a Dob.

I rarely bother with the star alignment for the EQ6, but thats just me. I can pick out the bigger objects in the sky and just motor the mount towards it. Only if I'm after something unfamiliar (which is quite alot) do I use the GOTO