Newby seeking 'which scope' advise...

AndyTee (Andy) · #1 18-05-2010, 06:55 AM

I am new hereabouts, though I have been lurking and reading furiously for a few days. I have pretty much zilch astronomical experience beyond a hazy ongoing fascination (I walk a couple of clicks every evening after dark). Anyway I have thought about 'maybe getting a telescope' for years and am about ready to take the plunge.

Reading the various 'beginner' posts has pretty much convinced me that a 6" Newtonian on a Dob mount is the way to go. I think a Saxon might be best - to my uneducated eye it seems to come with pretty good EPs etc included. I could spend the extra for an 8" but if I read the forum right I am likely to get clearer,sharper looking more often with the smaller scope. Is that right/wrong????

If I go the 6" route, what other stuff should I get on the first order to get off to a good start? The scope/supplier at the top of the list is http://www.ozscopes.com.au/dobsonian...xon-6inch.html

A bit more info about my 'normal' viewing site - back yard - might be helpful. I am cursed astronomically by having a back-yard jammed between a two-storey house to the south and a stand of VERY tall eucalypts in an arc from SE right around to directly west. We NEVER see the sun from autumn to late spring, it never gets over the trees, so neither will the planets. My interest therefore is going to be the moon and DSO pretty much straight up. Yes I know 'straight up' is a problem, but I have nothing below about 60 degrees except SW

Another 'local' issue is dampness. I am also cursed by a nearby river, winter evenings are damp. So damp that about an hour of use delaminated the edges of a plasticised-cardboardy sort of sky chart I bought. I know that dampness is going to make the 'seeing' worse, but how will the scope itself react to regular exposure to very high cold humidity? Would a sealed tube be better? I had almost talked myself into parting with $1k on http://www.ozscopes.com.au/celestron...telescope.html before I started reading this forum...

On the upside I have fairly easy access to what might be the world's best dark sky, tree-free hilltop (at a guess 270 degrees clear down to the horizon with only very slight rising ground to the North). Getting there though involves about 50k on dirt roads. How well does a telescope travel over fairly rattly corrugations punctuated by the occasional bone-jarring thud????

Sorry about the very long first post, I promise extreme brevity in the future...

Andy

bmitchell82 (Brendan) · #2 18-05-2010, 11:58 AM

Well, all i can say is for that price of 1000 dollars, ide go a 10" dobsonian, theres been a heap on the forums lately for 500 dollars. and considering your running with pure Visual, you want aperature, and also considering you want to look at DSO's the bigger the better.

the difference between the size will be brightness and details. clarity should be with any scope.

Things to get Irrispective of scope size:-

a good set of hex keys
a good phillips and flat screwdriver
a laser collimator (youll have to do some mods to anything cheaper than about 100-150 bucks, but they are easy to do, just take a few momoents of your time)
a cheschire eye piece.

go with the standard eye pieces for a start, then your next purchase should be a good quality 2x barlow, followed by a 20mm eye piece, 40mm eye piece and then a 10mm eye piece.

and then get rid of all the standard ones.

If your thinking about attaching a camera to your telescope. everything changes dramatically!

let me know if you are going down that path.

Suzy · #3 19-05-2010, 03:16 PM

Quote:

Originally Posted by AndyTee

Reading the various 'beginner' posts has pretty much convinced me that a 6" Newtonian on a Dob mount is the way to go. I think a Saxon might be best - to my uneducated eye it seems to come with pretty good EPs etc included. I could spend the extra for an 8" but if I read the forum right I am likely to get clearer,sharper looking more often with the smaller scope. Is that right/wrong????
Andy

Welcome Andy

I think you may have gotten confused with the "seeing" conditions and how it affects the image on different sized apertures. Smaller aperture scopes show less detail, so if the "seeing" isn't so good, it won't affect the image as much on a 6" as it would a larger aperture.

Yes the 6" & 8" dobs are the ideal beginners telescopes but if you can afford it, go for the 10 inch! Brendan has given very good advice.

astro744 · #4 19-05-2010, 04:34 PM

Quote:

Originally Posted by bmitchell82

Well, all i can say is for that price of 1000 dollars, ide go a 10" dobsonian, theres been a heap on the forums lately for 500 dollars. and considering your running with pure Visual, you want aperature, and also considering you want to look at DSO's the bigger the better.

the difference between the size will be brightness and details. clarity should be with any scope.

Things to get Irrispective of scope size:-

a good set of hex keys
a good phillips and flat screwdriver
a laser collimator (youll have to do some mods to anything cheaper than about 100-150 bucks, but they are easy to do, just take a few momoents of your time)
a cheschire eye piece.

go with the standard eye pieces for a start, then your next purchase should be a good quality 2x barlow, followed by a 20mm eye piece, 40mm eye piece and then a 10mm eye piece.

and then get rid of all the standard ones.

If your thinking about attaching a camera to your telescope. everything changes dramatically!

let me know if you are going down that path.

40, 20, 10 with 2x Barlow only gains you a 5 as the 20 & 10 are doubled up. Also a 40 with 2x Barlow has far too long an eye relief unless you get a 2x Powermate.

You can collimate by eye without the laser and yes the cheap ones are out of collimation themselves defeating the purpose. Search the web for collimating a Newtonian and you will find plenty of resources.

If you can afford it go the 8" over the 6" for almost twice the light gathering capacity. The 6" f8 and 8" f6 are almost the same size except for tube diameter. The 10" f5 has a larger tube again but is still manageable. After a bumpy road trip you will need to collimate. Also the mirror will shift inside it's cell and a bit of PVC tape around the clips holding the mirror will stop it rotating and possibly scratching the surface. Note the mirror clips must not be over tightened to avoid optical deformation.

Dampness and dew is more of a problem on closed systems where moisture may get in but has trouble escaping. An open tube Newtonian is fine in damp conditions and will not rust as most of the components are alluminium or glass. A dew heater is available for the secondary mirror and for eyepieces.

A set of tools and torch, both red and white is a good idea.

AndyTee (Andy) · #5 19-05-2010, 07:28 PM

Thanks for all the replies and advice!

Current thinking is 8" - I'd rather get a couple of decent EPs and a Barlow straight off than wait, and I don't want to blow more than I have to on something that might not work out. Conversely if it does work out I am happy to upgrade fairly quickly...

The tools etc I already have, the advice to search for manual collimation articles was well received (I don't mind tinkering) so all I need now is the scope and some fine clear nights!

@ Brendan: astrophotography is probably in my future (I have dabbled in photography most of my life) but atm I have neither laptop nor webcam. I do have a couple of DSLRs which I hope to bring to bear in the future, but I know the Dob is not 'quite' the right tool for that...

Thanks again

that_guy (Tony) · #6 19-05-2010, 07:47 PM

if your thinking of photography anytime soon, you might want to consider an 8" Reflector on EQ mount. This way, the same aperture as the 8" dob but tracks... i think its in your budget...

bmitchell82 (Brendan) · #7 21-05-2010, 02:20 AM

as for getting the collimation right i am going to disagree with you whole heartedly. I've had my reflector for a year and a half now and it was since i got myself some good collimation tools that things changed.I do astro photography and with the 10" skywatcher have never got the FWHM below about 4-5, last night i had it at 3.02 which was absolutely awesome! and i can tell you the detail that i got out of that was phenomenal!

Also the there are specific reasons to why I said the combination of ep's if you wanted to be very specific i wouldn't introduce a barlow at all! just get the correct eye pieces the less glass in the way the better, in saying that those eps are not cheap! I have a meade S5000 eps, 40, 26, 20, and the 2x ED barlow, to be honest with you i rarely use the barlow to the point i have religated it to a 50mm Extension though it is there if i need it!... i use the 20mm the most, followed by 26 and the 40 for extended star fields. if i wanted to do planetary or PN viewing(which is the only reason for mega magnification) then i would spend the money on a 5mm nagler or panoptic but i am happy with using my cam to view so everything is peachy.

Collimation is CRITICAL if you want perfect views, if you don't really care then a 35mm film canister will get you pretty much a decent view but not stunning. Its like i always say, if your just out there to swing ya bat and throw your ball about then hey anything goes, but when you want to start doing something that is just a bit more than a fleeting fancy....

Andy, if your looking to get to photography, but don't have the $$$ or equipment yet, be sure to make calculated moves. I am a uni student and do not have bulk funds at my disposal, everything i do is for a very specific reason! getting the correct instruments will be hard as photography requires different specifications. I have heavily modified my 10" Skywatcher dob to the point that the only thing skywatcher is the tube and the mirror. the secondary has been changed, the primary cell has changed, the focuser has changed, the spider vanes have been changed, and the tube hasn't missed out on getting changed,

i had to shorten it to fit the 3"FT focuser.

There are a lot of considerations when moving down this path as astrographs are generally a lot different to visual scopes. Just keep asking questions and the community will pitch in their knowledge, its up to you to pick the eyes out and get what you need.!

AndyTee (Andy) · #8 26-05-2010, 05:12 PM

Good grief but this is a minefield! Things I had thought would be 'obvious' just aren't, and the things that seem like they may be most important simply didn't occur to me a couple of weeks ago. Thank goodness I didn't just 'jump in'...

PORTABILITY: Never even thought about it, but the only place to keep a scope in our house is an empty upstairs bedroom. Narrow stairs, with a tight landing. And there is no convenient route from the bottom of the stairs to the back door, so it is out the front, through a narrow gate and down a rough path.

BACK YARD: there is nowhere - and I mean nowhere - in our yard that approximates 'flat'. We live on a steepish slope. I could certainly level an area, but the damned trees that surround the place dictate that the scope will have to be moved to at least three different locations depending on which direction I want to look. Three or four decent-sized level areas isn't going to work.

SO: a decent sized Newtonian reflector on a Dob mount is not looking like a choice which will see a lot of use.

I have used cameras for years and am familiar with setting up tripods on bad ground. I don't think a EQ mount scares me too much. And the more I think about it the more likely it seems that I will want to hang a camera off the thing sooner rather than later.

Current thinking is now headed more to something like an ED80, or maybe a SCT of some sort on a decent sized GEQ base. I am not too fussed about GoTo (I suspect the challenge of finding will simply add zest to the seeing), but something that tracks once I find it seems sensible.

Comments? Suggestions? Alternatives?

jjjnettie (Jeanette) · #9 26-05-2010, 05:59 PM

I believe an 8-10" dob is the way to go when you're first starting off.
They give splendid views through the eye piece. They're simple to use.
Easy to set up. If an object you want to see is behind a tree, just put the scope on it's trolley ($25 @ SuperCheap) and move it to a better location.
It's not that simple with an EQ or eve Alt Azi mount. They'll need to be realigned after moving. (ho hum and I'd rather be observing than having to play around with the mount again)

jjjnettie (Jeanette) · #10 26-05-2010, 06:01 PM

Later, once you've been to a few star parties, and seen the equipment that others use. See how things are set up for Astro Photography. It will give you food for thought as to where you may want to go in this hobby.
But in the beginning, keep it simple and enjoyable I reckon.

AndyTee (Andy) · #11 28-05-2010, 03:56 PM

Thanks Nettie. I took myself into Bintel's in Camberwell today and they said pretty much what you said - "Keep it simple, stupid!" Unfortunately they are out of stock of 8" Dobs at the moment and also pretty sure the next shipment is over committed already. I had a big think about a 10", but I really think it might be a bit cumbersome in my environment. Anyway I think I might have sourced something second-hand from the IIS forum....

Andy

jjjnettie (Jeanette) · #12 28-05-2010, 04:16 PM

I had a 10" and used to shift it around everywhere using that trolley I mentioned earlier. Down a heavily gouged driveway then over cattle grid if I wanted to observe in the front paddock. If you do have to man handle it, it does break down into 2 easier to move pieces.