Planning to buy a first telescope?

russ_watters

It would be better to learn star collimation, but it will be tough on a Dob since it requires high magnification. (and calm skies)

Chronos

For a practical collimation guide see http://www.skyandtelescope.com/howto/diy/3306876.html.

davenn

thats great :)

Its us "older guys" (like me) that learned how to get around the sky without digital setting circles and "goto" telescopes.
LEARN and I say it again LEARN how to starhop you way around the sky to find objects
yes it takes a little longer but the huge advantage is you will really get to know your way around the stars :)
And that nite you are at some friends place and the only thing they have is a pair of binoculars, you wont be lost in showing them a few objects of interest

Dave

AnTiFreeze3

Luckily, I'm almost forced to learn the skies, since I have a simple dobsonian mount.

And I actually just got back from the meeting. It's very official, in that they are allotted a decent amount of money from grants, and are building a new observatory (there are on-going debates as to what type of telescope should go in it), but everyone there was very welcoming and relaxed. They were all at least 35 years or older, but this will only benefit me, because they all seem very experienced.

Apparently, one guy got bored and built his own 32" dobsonian; I feel like I will have a lot to learn from them.

Chronos

My first scope had setting circles that proved utterly useless. Of course I had no clue how to polar align my scope [6" f8 newt], which was a contributing factor. The setting circles had like 5 degree increments which further exacerbated an already hopeless situation. My favorite eyepiece offered less than about 1 degree tfov, which was also unhelpful. Goto was a pipe dream back in those days, so, star hopping was the only option. I hated star hopping, and still do. Albeit, I admit, it was instructive.

russ_watters

While I have respect for the skill required to look for things without GOTO, IMO, this was largely a barrier that got in the way of the primary goal of looking at things. I'm not sorry to see that skill die.

davenn

in many ways you should be thankful that you have a "Dobo" mount, you really will never regret learning to move around the sky the old way.
Goto scopes are great, only just got one myself at the beginning of the year after 40+ yrs in astronomy. But one has to be consious of not becoming too lazy and forgetting the basics by letting the scope find everything for them.
There is nothing wrong with goto scopes, for some one who really likes to get around many objects quickly say... those that supernova hunt in a mass of galaxies regularly or if you are trying to find new faint objects, whatever they are... comets, asteroids, or deep sky objects then having the scope get you into the right area of the sky helps lots :)

Dave

Chronos

You still need some basic star hopping skills, even with goto. I feel insecure until I can match the field of view to a star chart, but, goto is a huge time saver when it puts you close enough not to deal with the tediousness of leaping star to star from several degrees away to reach the target area. I've been a variable star observer for 40 years and finding those target fields are incredibly difficult compared to something distinctive, like a galaxy or planetary nebula. I still use my 40+ year old all sky charts.

AnTiFreeze3

Long story short, OwlAstronomy had to cancel my orders and fully reimbursed me for my purchases: the 20mm eyepiece ($33) and the variable polarizing filter ($20).

So, I'm still stuck with my 25mm, standard-issued Plossl, the shorty 2x Barlow, and the extension tube that I bought (which has worked well thus far).

So I've searched around a bit, and found this.

So here are my options.... tell me if they're feasible or not:

1.) I don't buy the case. I would consider making individual purchases based on what I need at any given time. That leaves me with the following magnifications:


25mm Plossl: 48x
25mm Plossl + 2xB: 96x
*25mm Plossl + 2xB + ET: 128x

2.) [a.] I buy the case, selling what I don't need, keeping what I need.

I would sell the 4mm and 6mm eyepieces (4mm gives too high of a magnification, 6mm would be redundant w/ 12.5 and Barlow) so that I could use them to finance a nice 5mm planetary eyepiece. I would compare the Zhumell Barlow with my Orion Shorty Barlow, and sell the lesser of the two. In this option, I would debate selling the 25mm Plossl or not; I primarily use it as a finder, and feel as if the 32mm would take over this role.

That leaves me with the following magnifications:
32mm Plossl: 37.5x (about as low as my telescope should go... or so the internet tells me)
32mm Plossl + 2xB: 75x
*32mm Plossl + 2xB + ET: 100x

25mm Plossl [Refer to above for magnifications]

12.5mm Plossl: 96x
12.5mm Plossl + 2xB: 192x
*12.5mm Plossl + 2xB + ET: 256x

(And assuming I purchase a 5mm planetary eyepiece)

5mm: 240x ... I wouldn't use the Barlow/ET for obvious reasons.

[b.] I would be the scrooge of this Christmas, and follow suit as in Part A, but would skimp out on purchasing a 5mm planetary eyepiece (I am still in consideration of selling the 25mm Plossl that came with my telescope because there's an overlap in magnification when using 25mm with the Barlow and the 12.5mm by itself).

I would do this because, when using EP + 2xB + ET with the 12.5mm, I can get up to 256x magnification, whereas with the 5mm eyepiece, I would be limited to 240x.
_ _ _ _

I know this seems ridiculous, but I am almost always incredibly careful when spending my own money. It also seems as if I should just altogether skip out on the case, since I would sell two of the four eyepieces, but the filters and Barlow would be very beneficial, and I haven't seen a package like this anywhere else.

*Assuming I did my math correctly. The extension tube is 2" long, and the shorty barlow lense is 3" long. If I were to have a 3" ET, then my shorty barlow would bump up from a 2x to 3x, so I made my calculations under the assumption that, when using a 2" extension tube, it would essentially make a 2x Barlow into a 2.666...x Barlow lens.

Chronos

The 25mm plossl will be ok. It is unfortunate the OWL is unavailable, its a great EP for the money. You can still cruise ebay for a used wide field EP.

AnTiFreeze3

I found this eyepiece, along with these filters. I'll probably just buy these two separately and save myself the head-ache of trying to rely upon other people buying what I don't need.

Chronos

14mm is a bit short for a wide field. You really want something in the 20+ range.

CowedbyWisdom

Hey guys! I am interested in buying another telescope and was wondering if any of you had any advice about either of the two i'm split between. It seems to simply come down to a quality? vs aperture argument. The first scope is a Zhumell Z12 with a 12 inch aperture seen here... http://www.telescopes.com/telescopes...rtelescope.cfm or a smaller but from what I have read online (hence the apprehension) a more quality scope in the Meade Light Bridge 10 inch dob shown here... http://www.telescopes.com/telescopes...iandeluxe2.cfm
Any and all advice on which would be the better choice as a 2nd telescope would be greatly appreciated. Cheers!

-Jack

chemisttree

That telescope would be very similar to what you already have. What bump in quality do you seek? If you are mainly concerned with the optical quality, I would consider replacing the diagonal with this one. If the focuser isn't up to snuff.... replace it too! Maybe have the main mirror refigured and recoated eventually?

davenn

not really

the scope he bought some time ago was a 90mm (f10) refractor
I had to go searching through this thread to discover for myself lol


Both these 2 scopes being decided between will make awesome "light buckets" :)
10 - 12 inch at ~ f5 or so will be quite fast optics compared to the refractor and
nebulae etc will appear so much brighter

CowedbyWisdom .... I can assume by your trend in choices of scopes that you are not really interested in goto ability or motorised tracking for astrophotography use ?

either of these 2 dobo's will make great viewing of the skies .... see if you can find some independant/unbiased reviews of both of them .... ie. not reviews that may be posted on the sales page sites

I own a 10inch f5 dobo, solid not truss tube, if you got the truss tube one, you would need the shroud to wrap around it to keep ambient light out
I also own a Celestron C9.25, 9.25inch f10,
each has its uses the f5 is a light bucket, but lower magnification
fast optics like f5's can suffer from a little spherical and chromatic aboration but this is normally only visible around the outter edges of the field of view and under higher magnifications. They are great for wider field objects, globular and open clusters, diffuse nebulae etc

The f10 scope offers much higher useable magnification and get great for small bright objects
planetary nebulae, galaxies, planets etc

Both those scopes say max useable mag of ~ 500x. I suspect that would be really pushing it and a bit of sales hype, In practice I would suggest that ~ 200 - 300x would be closer to the truth before the aborations spoken of earlier become quite obvious
Thats from personal experience with several fast scopes over the years

Dave

chemisttree

DOH! I even chimed in on that one!

Drakkith

Dave, other than the obvious effect the focal length has on magnification and eyepiece choice, why would the faster scope give brighter views? Or is that all you meant?