Dob or Auto dob?(that is the question!)

[tinny]

Hi

I was just about to pull my wallet out and pay for a skyliner dob as my first 'scope when I spotted the auto tracking versions...

I don't want a GOTO as I want the challenge of finding objects, but I wondered if this extra function added to the experience and was worth the bit extra?

(The cost isn't really an issue, more the benefit to functionality)

Thanks

tinny

p.s. Having just joined I have never met such an imformative and friendly bunch of people so thanks again

[brantuk]

I started with the flextube auto version - once you find something it stays in the eyepiece without having to push manually for about 30 mins. Imho it makes viewing much more convenient. Plus you allways have the option to upgrade by just adding a goto handset.

It allows you to "push to" or slew with the arrow keys as well - very clever bit of kit

[twotter]

I've got a 'dumb' dob and enjoy using it. Nudging isn't a big deal, in fact it takes longer to explain than it does to achieve.

My vote is for a normal Skyliner 200P, and use the money saved to buy a few accessories. Telrads are popular, cheshire collimator, wixeys etc... Wider FOV EPs make life easier on the nudging front, so perhaps a Hyperion or similar

[tinny]

Thanks lads, nice to get a couple of contrasting opinions...

I've heard these 'Telrad's banded about but what the devil are they!?Any clue on price?

[jimmyjamjoejoe]

Telrads are a type of finder, usually no magnification, that project a series of rings like a bullseye against the background sky. Kinda like a red dot sight you see on guns etc. They go for about £40-50 i think.

While i'm here i'l sling in a question i've been thinking about, since i'm in the same situ as you - Without the motor, how often will you find yourself needing to nudge? I know it obviously depends on the eyepiece used, but just in general, on a DSO using your "viewing eyepiece" as opposed to the wider "finding the rough area eyepiece", are we talking like 10-20seconds till its out of view, or a few minutes?

I think if it were anything less than 30secs or so, i'd have to get a motor, it'd do my head in lol

[brantuk]

I've been offered on as low as £12 second hand or they go up to £40 brand new. They work well on a dob - basically an illuminated reticle which is like a big "O" with a little "o" in the middle of it (circle within a circle).

The thing is they are not magnified but they represent in the sky exactly what's on a star map. So what you see enables you to plot star hops to your object. They look a bit ugly but are very effective and can be seen on a lot of dobs

[WayBig]

I like my auto dob, nice and easy to use the controls to slew around whilst you're at the eyepiece. The tracking is not the best but is useful sometimes

[brantuk]

I've seen a comet drift across a 22" dob in a wide angle ep in about 5-7mins if that helps. To keep it central though I had to nudge every 1-2 mins - quite easy in a big dob but in my 12" I prefer the motors.

[JamesM]

A Telrad is a red dot (in fact concentric circles) finder that is dimmable. They look like a toboggan for a mouse and you can find details here . The idea behind them is that you can point your scope toward the part of sky that is of interest using one eye whilst looking at the sky at the same time with the other. Merging the two images together makes it look like there are huge red circles on the night sky. Most optical finders only allow you to view a small area of sky that can be devoid of any easily found star patterns and so it is easy to get lost. There are maps out there that have the Telrad circles on them so that it can help make star hopping really easy. The only downside is that of course it relies on you being able to see where to point the scope (finder) which isn't easy with light pollution. This product along with a right angled finder in which the view is only back to front as opposed to being back to front AND upside down with a straight through finder, makes the perfect combination to find anything manually.

So Telrad gets you very close, right angled helps you find the object leaving you to fine focus with the eyepiece (well that's the theory!)

Clear skies

James

EDIT: I can't type as quick as brantuck - I think he uses a secretary!

[umadog]

Telrad: The Recreational Astronomer: Using a Telrad

In practice, when hand-tracking you don't really think in terms of "oh dear I have to push the scope again." Nudging it along becomes second nature. The key thing is not how often you have to push the scope, it's how easy the scope is to push. Specifically, how bothersome hand-tracking is depends on the scope's bearings. If the bearings are bad then it feels like you're fighting the scope. There may be back-lash or static friction (or both). Yuk! If the bearings are good, then the scope feels like an extension of yourself and there's no problem at all. If it's a Dob, you can upgrade bearings fairly cheaply: you're not stuck with what came with the scope.

For most DSO viewing I tend to forget I'm tracking at all. I only notice the need to track when I'm looking at planets at over 200x and trying to pick out subtle details in moments of good seeing. Under those circumstances auto-tracking is a nice luxury. However, it's quite possible to get a lot out of planetary observing at 300 to 400x using hand-tracking.

[great_bear]

It allows you to "push to" or slew with the arrow keys as well - very clever bit of kit

Can you really do "push to" on an upgraded tracking dob?

- I thought they lacked the encoders required for "push-to" to work?

[umadog]

Can you really do "push to" on an upgraded tracking dob?

- I thought they lacked the encoders required for "push-to" to work?

It depends what you've bought... I think with the Orion ones you can because there are encoders in the motors. Check, though. If you go all-out and buy an Argo and ServoCat then you can do more or less anything.

[tinny]

Brilliant thanks, I think that about covers it!

[great_bear]

It depends what you've bought... I think with the Orion ones you can

This was in specific reference to the Sky-Watcher Flextube ones. My understanding is that you can't push an auto version with a goto handset (at least not without scrambling any alignment), because the "auto" version doesn't have the encoders that the true "goto" version has.

Happy to be proved wrong though, if someone's tested push on an upgraded "auto" Flextube.

[umadog]

Oh, sorry. Thanks for correcting me!

[MatthewC]

Sorry for hijacking this thread but is it possible to buy the auto mount for the standard 200p dob seperately?

[great_bear]

Nope!

[Pingster]

I have two goto scopes. And i was completely new to astro before. In my humble opinion go for a goto scope. Yes it cost more. But in the UK we have such bad weather that you simply can not afford to waste time looking for objects when your viewing window is sometimes only 1hrs or 20mins at a time (seriouly, you will find this out very quickly). Most dobs will come with 3 eyepieces everything you been to see well. I have a 16in dob and only use a 32mm and 17mm and a x2 powermate. UK seeing cinditions simply dont let you use more powerful mags very often. The saving you have by not buying goto will let you buy more eyepieces. But tbh, whats the point if you cant find anything to look at.

My brother was outnwith me list night. He does not know any objects location. But with a quick 5min tutorial he was flipping thru the tour mode happily all night without any help. I almost rellied saying get a push to... But i think those who have been into astro for more than 6months will recommend push to, maybe like me they actually forgot how difficult things where when they started out, as they know the key targets by heart now.

Get a goto. You wont regret it. As you can always push it to targets on nights of completely clear weather, and you have plenty of time to challenge yourself, yet if it gets too frustarting you can go back to goto.

Also i will add that i go viewing with newbies and those with years experience under their belts. And very often i use my goto to help them

Locate and confirm new targets, and very often targets they view on regular basis but just cant seem to remeber where it is!

[great_bear]

In the UK we have such bad weather that you simply can not afford to waste time looking for objects when your viewing window is sometimes only 1hrs or 20mins at a time

I have to say that I agree with this. Furthermore I don't see any evidence that it hinders your ability to learn the sky. Faffing around clueless as to where you are hinders your ability to learn the sky. So I'm completely behind you on the goto front...

On the magnification front there's a lot of things that influence this - and big scopes without smartly designed thermal management are going to give you an illusion of poor seeing when it's the scope that's the problem. I hear some people say that 200x is maximum magnification in the UK but that's simply not true. It's a rare night when I can't manage 300x at some point during the evening - even if it's only for half-an-hour - and 360x is not unusual either, although (again) only for a short period during the night.

[umadog]

The maximum magnification depends on the object. I regularly view globulars at 300x or more but on the same night it's unlikely I'll stray much above 200 to 250 x on Jupiter. I think people are saying 200x because that's a more commonly used magnification. Of course, as bear says, you need to make sure you scope is cooled down.

I must say that short observing windows are the only times I use GoTo. Even as a die hard star-hopping, I can see the benefit of goto under these circumstances. When I'm somewhere dark and looking for, say, Neptune. Then I'll do a goto because I'm not interested in learning it's current location and hunting for it. I don't get to go to dark places often so I want to see interesting stuff when I'm there. However, even from dark skies, I will rarely use the GoTo because I find I'm faster on the easy objects or the objects I already know. That's why I like learning the sky--it's pretty cool to beat the machine and if the power fails it doesn't matter. For these reasons, I think push-to is often a better option. You have the crutch of the machine but you aren't paying for drives and all that stuff. It's easy to star-hop and use the machine to give you a hint when you're stuck.

If you want to see loads of objects *NOW* then learning to star-hop may seem like a chore and may be frustrating (depends how quickly you take to it). However, it also depends why you're in hobby. Perhaps you star-hop and find only 3 objects in 2 hours. If you spend quality time with those objects and have learned a lot in the process of finding them then how long it took doesn't matter. I'm not trying to start a GoTo/star-hopping debate because those get tedious (use whatever works for you), I'm just saying that if your sole goal is the view then use a machine if that's what it takes. If you're interested in the whole process and don't mind a few initial outings with low object hauls, then skip the goto and take things as they come.

[great_bear]

It's a rare night when I can't manage 300x at some point during the evening - even if it's only for half-an-hour - and 360x is not unusual either, although (again) only for a short period during the night.

OOPS! Just realised that I was getting my eyepieces muddled up!

Please re-read that as: "It's a rare night when I can't manage 230x at some point during the evening - even if it's only for half-an-hour - and 300x is not unusual either, although (again) only for a short period during the night."

That's a bit more conservative!

The above on Jupiter on my Mak180.

Oh - and apologies for the error!

[SteveKinder]

Maybe save you some time and frustration –

I have been trying to but a new Telrad for over a week now and you can’t get one for love nor money. Well not quite true, a very helpful chap called Bern at Modern Astronomy offered to get me one from Germany but to his everlasting credit he recommended against it based on the inflated price. I have been told that both there is a problem with production and a problem with the UK importer. If you can get a second hand one for the sort of price indicated then bite their hand off.

I am looking for one based on a recommendation from a very respected and experienced astronomer and it’s is clear that some people really like Telrad’s. However, they don’t seem to do much. No magnification, just a mirror and a bit of glass with a red circle on it as far as I can tell.

If you go for something like a 9 * 50 finder scope you can also potentially use it as a guide scope.

Cheers,

Steve.

[great_bear]

they don’t seem to do much. No magnification, just a mirror and a bit of glass with a red circle on it as far as I can tell.

Yes-and-no really.

It's true that Telrads are really clunky, and look like they cost about £2.50 to make. There's no mirror though. It's just a 45-degree bit of glass that reflects an illuminated image of some concentric circles.

But describing it as such is a little bit disengenuous - it would be like describing a telescope as "just a tube with a magnifying glass at the end"

The image of circles goes through a lens so it appears on the infinity focal-plane - so it looks like massive red circles are drawn on the sky. This makes for a device that is both fun and practical to use; the real innovation being that the spacing of the circles at 4,2,and half-degree sizes makes for a tool that greatly aids star-hopping.

Hope that helps explain this overpriced accessory box!

For me it's not a replacement for a 9x50 finder, but an augmentation of one. i.e. you use the Telrad to get you in the right vicinity of something, and then use the 9x50 to get bang-on-target. In the case of a right-angled 9x50 (or 6x30 etc.) finder, either a Telrad or other type of red-dot finder is more-or-less-essential to get you in the right ball-park...

[SteveKinder]

OMG you don't even get a mirror!? :-)

Don't get me wrong. I do want to buy one as I feel you can't all be wrong. I am just a bit sceptical. Not helped by the fact that nobody seems capable of taking my money off me for one.

Hopefully I will be singing the praises of Telrad in the near future.

Steve.

[great_bear]

OMG you don't even get a mirror!? :-)

- and I'm not even convinced the "glass" is real glass...