Newbie Astronomer - How to make the most of poor equipment

[esxste]

Don't buy any eyepieces, and save the money to give your budget a boost for the Skywatcher 150p. You can upgrade your eyepieces after, and can enjoy the better views a bigger aperture will give you. 

[LukeSkywatcher]

 I think the Vixen NPL's would be more or less as much as I'd be willing to spend at this point until I've had a look through one and I'm convinced it'll make a reasonable difference.

The NPL's really do make a difference over stock supplied EP's. I find them brilliant. Very sharp across the FOV and the contrast they offer is amazing. Most people who use them or have used them say that the eye relief is not great, but i find it fine. Ive used the NPL's in all of my scopes and never had a complaint.

[Lowjiber]

I hope you take this constructively.

Those little 76mm tubes are all made in the same small factory, and are then marketed under a variety of names, Bushnell,

Venture, Seben, etc.  Given the small aperture and adding in the obstruction of the secondary, it will never be much more than a beginner's scope... as you already recognize.  Targets like Juipter, Saturn, the Moon, M42, Pleaides, and a few others will be accessible, but deep space objects are pretty much out of the question.

My neighbor bought one at a garage sale last week for $3 (US), and came over asking me to "fix it"... thus my experience with these small Newts.

Below are some steps you can take that will not only tune it up, but give you some insight that will be needed as you progress to better equipment.  I'm assuming you'll be willing to invest a few dollars and some time.  If not, stop reading here. (Grin)

The first, foremost critical thing is to get it collimated.  This process of aligning the mirrors and focuser is critical to getting the most out of the little scope.  What will you need?  Either a laser collimation device, or a Cheshire device... more on that in a link below.

That scope's objective mirror is not "center-dotted".  That's a process of removing the main mirror cell and installing a mark in the exact center of that 3" diameter mirror.  This mark will be used to adjust the mirror in relation to the secondary (smaller) mirror during the collimation process.  Most folks use a self-adhesive hole reinforcing "donut" like you'd use on notebook paper, but even a black dot from a Sharpie will work.

So how do you get the mirror out?  Below is a picture of the bottom end of your scope.  There are six screws.  The three that are screwed all the way in are the cell mounting screws.  The others, which are likely slightly unscrewed, are the tilt adjustment screws.  Simply remove the three mounting screws, and the cell will come out with the mirror still in place.  (You many need to lightly tap the outside edge of the cell with the blade of a straight slot screwdriver to "unstick" it from the tube.)  Do not clean or otherwise touch the mirror with your fingers.

Now, follow the process described in this video.  (In your case, you won't need to remove the mirror from the cell... that's for much larger scopes.)  The diameter of your mirror is exactly three inches... no need to measure it.  https://www.youtube.com/watch?v=0tRHYSzaRLk

Now that you have the mirror center-dotted, simply reinstall the mirror cell and bolt it in with the three screws you removed earlier... they don't need to be "super-tight", just "snug" works fine.

Now, you're ready to collimate it.  Collimation seems daunting at first, but with a few basic concepts, it will become second nature.  What may take you an hour now, you'll be doing in five minutes after you've done it a few times.  (Small Newtonians like yours, don't need much additional collimation.  However, larger (>150mm) need to be at least checked every time out.)

Here's a link to what many consider the "bible" of collimation.  Read it carefully (twice) and follow it steb-by-step... no shortcuts.  At the end of the piece, there is a section on how to do a simple "Star Test" after collimation.  A star test is a quick, accurate way to know if your scope is collimated... we all do it, all the time.

http://www.astro-baby.com/collimation/astro%20babys%20collimation%20guide.htm

The link above describes using a Cheshire to collimate.  There are tons of videos about how to do it.  Just Google "collimation Newtonian" and have a nice time watching them.  The techniques are all the same unless one has a Bird-Jones design Newt, which you don't.  (Thank God)

A word about eyepieces...

The pic below is some data that I wrote on the scope to remind my neighbor of important stuff.  Bottom Line: Your scope is what we call "slow" wth a focal ratio of f/9.2.  What does that mean?  A lot.  However, for your purposes right now, it's telling you not to even attempt to focus with any eyepiece shorter than 10mm, and then only in good seeing conditions.

Trust me. LOL

Clear Skies

[Charic]

procky1845......Hi, In addition to all the advice already given, I would say don't buy a new Eyepiece until you have a new telescope, especially as you already know, you WILL be upgrading! Just make the most of what you have. A darker site to view from could possibly make the most improvement to your viewing pleasure.  A £30 20mm Plossl or a £600  21mm Televue Ethos cant improve what your telescope can only achieve. The Eyepiece only allows you to see the telescopes image at the focal plane, which needs to be good in the first place. You know thing's can and will get better?

But if you do have to buy a new Eyepiece now I would buy 8mm BST Starguider?

Your mention of the sky-watchers is interesting. The 130 and 150 are fine. The 150 would be better because of the bigger aperture it affords. That said, the 200 would be better still and the 300 even better for visual observations, but as mentioned earlier in this thread, if you buy an Eyepiece now, then discover your getting a 300mm or bigger telescope, your Eyepieces may not work so well at the faster focal ratio the telescope would have.

In all honesty, if you think you like the 130 get the 150, and if the 150 is top of the list get the 200P. Then stop there. Some folk cant accept coma or think they need really expensive Eyepieces or correctors to bring out the best in a 250mm+ Newtonian telescope. All Newtonian's  have coma, its inbuilt by their design? the only way you can reduce the effect is to use a less powerful telescope, or use correctors to alleviate the effect on the faster telescopes. I know AndyWB has addressed several folk in the past, as he uses some of the  BST's to good effect in his 250PX. On axis, everything will look good but towards the field edge of view in the bigger telescopes, coma is more evident.

I mentioned the 8mm BST above. That Eyepiece goes very well with the Sky-watcher 'Skyliner' 200P Dobsonian. The Skyliner is an f6 ratio telescope which takes well to many of the Eyepieces available today, although I have chosen the BST brand. Look  at how many folk in this thread are using Dobs from Sky-Watcher. You wont want or need much more after using the Skyliner. Although for an even bigger brighter image you may need to go 300mm+, but weight, size and the expense have overtaken your life by then.

8" Newtonian, is the UK's best selling telescope......is often appended to the Skyliner.

I'd give the Skyliner some consideration. £330 delivered with an 8mm BST to get you started, then build from there. get saving now Christmas!

Filter through all the replies , check on-line, just  take your time, and enjoy what's ahead.  If you could visit someone or a club prior to Christmas to  try a 130-200 Dobsonian, that will help.   Take care for now.

[Charic]

Lowjiber......Hi, Thats good information in trying to get a little more out of ones telescope. I went down this same route with my Celestron 127EQ Powerseeker. The 127EQ telescope has the fixed 'Bird-Jones' corrector/Barlow lens to allow for a shorter focal length ( probably keeping the length short would keep the weight down which would wobble less in its flimsy GEM tripod ? )

What this exercise does do for the individual is to install confidence and to actually get some hands on experience with assembly and how the telescope works. Having completed my rebuild, with  Centre spotted primary Mirror using a blackened adhesive ring binder, and some newer Eyepieces. I came to my own conclusion that I still needed a much better telescope. But at least I was certain I could get no more from the telescope. My Skyliner arrived shortly after.

[procky1845]

Lowjiber - Thanks for the collimation info. I'll definately give my scope the star test next time I'm out. I'd not considered that it might not be setup correctly.

Charic - You're probably right about saving money for the new scope. I did look at the 200p Dob but it's a bit too big for me I think. Besides the fact that I don't really have room to store it I'd like something I can move about a bit more easily. The 200p explorer may also be a bit big for what I need at the moment although the extra aperture would be nice. I am still only just starting out so I think I will more than likely go for the 150p explorer as I think this will be enough to keep me going for a while.

[procky1845]

Out of interest what's the point of collimating the scope? Is it to improve clarity of the picture?

[dweller25]

Hi All,

Just wanted to say hello.

I've always had a bit of an interest in space, the stars and such, and I've always told myself that one day I would purchase a telescope and give astronomy a go. My wife bought me a telescope for my 30th birthday a couple of months ago and I've been using it to peruse the night skies.

My  telescope is not great (to put it lightly). Its a Seben 700-76 reflector telescope. The mounts very shaky, the optics are less than stellar, and its very difficult to see whatever it is that I'm attempting to look at. Out of the provided eyepieces I soon learnt that the only ones of any use are the 20mm, 12.5mm and 6mm.

Despite all this, I'm hooked. On the odd occassion where I have managed to see what I'm looking for I've had a great time. I've seen and resolved Albireo, viewed M13 as a faint smudge, observed the M39 open cluster, seen a few different coloured stars and have seen the Andromeda Galaxy ("seen" might be a bit of a strong word, it appeared as a small ball of light, I couldn't even make out the galaxy shape).

I've bought a couple of books, the S&T Pocket Sky Atlas, Turn Left at Orion and have learnt a lot of the constellations using a combination of Stellarium and giving myself neck ache in the back garden. I've also learnt how to star hop with reasonable success, and have learnt the difficult lesson that if your finderscope doesn't point in the right direction, you'll spend all night looking in the wrong direction.

I already have plans for a bigger scope, but I won't be buying a new one until Christmas time. I don't want to offend my wife, and if I can survive until then on the Seben it proves to myself that I'm not going to lose interest (and also I will more than deserve it by that point!).

So my questions are:

1. Has anybody else had any "experience" of using this scope to successfully hunt down some interesting sights? Any pointers for how to get the best out of this monster would be greatly appreciated.

    

2. Has anybody got any more general tips that would help somebody in my situation with a poor scope improve the things they can see.

    

3. What sort of things should I be able to see with it, I wouldn't say light pollution is a major problem for me as I'm more on the outskirts of the city where I live, but I have tried to spot the Ring Nebula every single time I've been out with the scope and failed. Maybe the scope's not up to it?

There is some awesome content on these forums and some very knowledgeable people, its been very helpful over the past couple of months.

Anyway, thanks for taking the time to read!

A couple of general tips....

1. Make sure the scope is fully cooled down before use - put it outside half an hour earlier than you want to use it, take off the dust caps and point the front slightly up to the sky to let warm air out but not let dust in.

2. Make sure the collimation (alignment of the mirrors) is good.