... by daring to raise the subject of "Department Store" telescopes on the IIS Forums, but I was flicking through the Aldi catalogue that just landed in my mailbox.
This weekend, they are selling the National Geographic 76 mm / 350mm table-top Dob for $49.99, and the National Geographic 76 mm / 700 mm Newt on an equatorial mount for $99.99. At those prices they're practically Christmas stocking-stuffers for any little kids that you might know. (I've used the table-top Dob, and it's not total rubbish optically.)
(Dons flame-proof suit and takes shelter behind a blast wall.)
I bought the table-top Dob a year or so ago, and it wasn't usable out of the box. The secondary mirror was not underneath the focuser, I had to supply my own (longer) screws to fix that. Apart from that it can be made to work and will give better than $50 views. The primary mirror looks quite decent, even though it lacks a means of collimation.
I was wondering about collimation on the cheap reflectors. Image quality would be all over the place and most gift givers wouldn't know how to do it anyway. Might be better off with a cheap refractor.
I bought a $48 60mm F11 refractor Dick Smith special a few years back out of curiosity. It was actually pretty good and well worth the $48.
These little scopes are a hit and miss affair. The mirrors on the whole are spherical rather than parabolic. This makes them not really suitable for high power observing. The quality of individual mirrors can be variable too.
If you keep this in mind, don't expect too high magnification, and enjoy low power, wide field viewing, then these can be surprisingly good.
I picked up one of the Celestron FirstScope 3" dobbies. I quickly came to see its strengths and shortcomings. Then I found the perfect use for this little chappie - as a big finder.
I've coupled this little reflector onto the 'back' of my 17.5" dob. This dob has three finders on it - by design, not folly. For this big dob, and as I only use it as a push-pull scope, this big finder works very well when using very detailed charts.
I totally agree that these little scopes will need to be individually fine tuned. As they are made so cheaply, part of the cost saving is cutting corners during assembly and component selection. You will need to give these some considered TLC.
But there is one more tip to pimping these little fellows - ditch the eyepieces that come with it. They are very poor quality. Use half decent plossls or even a humble Kellner, and you will be very surprised at the performance of these modest little scopes.
Alex.
PS, In the photo, you will see in the background, hickny's 13.1" dob also with one of these 3" Celestron FirstScope's as a big finder.
Last edited by mental4astro; 05-12-2014 at 09:59 PM.
My son has a Celestron FirstScope from his grandmother, a purchase based on the Amazon reviews. I can see why it has those good reviews, it seems like super value for a little while.
Pros:
* Small/cheap/light
* It is reasonably stable and easy to get on target, a big plus for beginners/kids
* The focuser works OK, although the grease in ours went bad within a couple of years (thick, tacky).
Cons:
* The eyepieces are not good. They belong in a McDonald's toy, especially our 4mm.
* The scope optics are not good. With a very good eyepiece, I can kind of tell that Saturn is not round. With the included eyepieces, I have no idea what I'm looking at.
* The 4mm included eyepiece a lie - our scope is not remotely capable of that usable magnification. With a good eyepiece, you can clearly see the different parts of the mirror come into focus while trying to find the best compromise. The Nat Geo one seems to be promising even better magnification. There is just no way if it has the same spherical mirror.
* Out of curiosity I tonight tried a 24mm Televue plossl in it - I think the views through our basic Synta 50mm straight-through finder are much cleaner and reveal more.
It is the kind of thing that might inspire someone with means to get something good. For someone without means, such as a young child, I think it is a bit of a cruel gift. It hints at what it might be like to own a telescope.
I sort of agree with jayeson, however I found my FirstScope to be very usable with baader hyperion eyepieces, much better optically than i expected. So maybe the optics aren't consistant, the supplied eyepieces are garbage.
I must say, having patiently waited for a loan scope from ASV for the past several months I find this little bugger to be tempting to muck around with, though not nearly as much as the $300 12in bintel dob in the ice trade section, which went to another member on here - congrats!.
I've held off buying this thanks to the reviews on this and other sites, however some say it does reasonably well with a 15mm bintel/gso eyepiece for widefield?
My local ALDI still has over 20 of them and they've been sitting for just over a week now. I keep checking every few days when I'm in the area to see if they've dropped the price, as they tend to do for special buys that don't sell. If they do then I might just have to pick one up to play around with until I can get the loan scope...
Decided to take a punt on a used skywatcher heritage 130p instead. I know the focuser is the weak point but it'll do for grab and go and camping duties.
[QUOTE=Steffen;1138060]I bought the table-top Dob a year or so ago, and it wasn't usable out of the box. The secondary mirror was not underneath the focuser, I had to supply my own (longer) screws to fix that. Apart from that it can be made to work and will give better than $50 views. The primary mirror looks quite decent, even though it lacks a means of collimation.
I saw these in Aldi "special buys" mentioned it to my niece who works there.
One appeared as my "secret santa gift"
Last time I had a telescope was 1972 as a 12 year old with a Tasco refractor?
Which gave me such many hours of joy standing a top our aluminium carport roof , in west suburbs of Sydney-looking at the moon, Jupiter and Saturn. They were only small discs but I could just make out Saturn with a ring around it.
Now I live on an isolated farm and the stars are brilliant on clear nights, with no light polution.
I'm wondering how this will go? I wont be home until Jan 4 at present near Wyong on the central coast NSW.
Would love to rekindle my youth getting back into star gazing, but Im not expecting a lot from this small dob, as have read here before a 6-8" Dobson would blow my mind.
Anyway its 60 days to give it a try
As you've posted above, a number of users reported that the secondary mirror was not properly aligned with the primary mirror and it was impossible to do so unless they replaced the bolt to which the secondary mirror is affixed (a trip to the local hardware store armed with the bolt from the scope may be in order.).
I picked up a bintel/gso superview 15mm 1.25" eyepiece for use with my scope and apparently it's also good for use in the little aldi/nat geo dobs.
If you have any troubles with it then post back here for help.
As you've posted above, a number of users reported that the secondary mirror was not properly aligned with the primary mirror and it was impossible to do so unless they replaced the bolt to which the secondary mirror is affixed (a trip to the local hardware store armed with the bolt from the scope may be in order.).
I picked up a bintel/gso superview 15mm 1.25" eyepiece for use with my scope and apparently it's also good for use in the little aldi/nat geo dobs.
If you have any troubles with it then post back here for help.
I
Good luck.
Thanks for suggesting the eyepiece, I wouldn't know how to align the mirror even if I got the
Larger screw/s maybe could google a guide somewhere?
Cloud covered nights so far so cannot tell if its out of alignment, how do you tell?
Leaves on trees seem in focus and clear.
Ive often considered a scope just for viewing. What does a $50 view mean?. One awesome view, or years of satisfying viewing on every outing?. The SkyWatcher Heritage P130 Dobsonian Telescope is listed at a monster $260 (which sounds a bit extreme), perhaps something half way at say $130 would be ideal?.
Indeed, theres not much in between. I managed to get the slightly used skywatcher p130 for $150 delivered. Hope to receive it in the next week or so. If
Ididn't win that I'd probably have cracked and got the aldi dob.
Pete,
Your aldi dob has a fixed primary mirror and it sounds like your secondary might be set ok from the factory. Definitely try it out before mucking about with the alignment. Post back here if you need help with it.
Yes the primary mirror in these scopes is fixed in place, but there is a little trick that can help. By loosening the three screws that hold the primary mirror cell in place just a touch, the cell can be tweaked a little to improve collimation, and the screws are then re-tightened.
There is SOME repositioning possible with the secondary, but this is limited too. Remember, they are made CHEAP, so to spend too much time on them at the factory is not economical. Most secondary mirrors are just set eye-balling to give some sort of good-enough reflection of the primary back through the focuser. Thing is the position of the single arm can be set too high (or low) with the secondary holder mechanism not having screws long enough to give the secondary mirror enough travel to best collimate it with the focuser. If set too low, then nothing you do with the secondary mechanism will improve things. The only other option here in both cases is to re-drill and re-position the arm holding the secondary. My FirstScope has the secondary's arm set too high.
These scopes are not made for dedicated amateur astronomers. They are considered toys that will be discarded and forgotten quickly. So don't expect too much from them out of the box. Another reason for the poor eyepieces they are supplied with. To fabricate them to the standard we expect makes the labour involved too expensive - you are getting what you pay for. They all require considered TLC to trick them up to their full potential. This potential can also be compromised by they way they've been put together. Up to you then as to how far you want to take the modifications. But if they are modified as far as their design allows, and as far as your tools allow, they can be quite an effective little instrument.
So would this be better than the aldi one if I could get it for $250 second hand?
Or this one on gumtree for $100
Emailed them they replied it is a Precision brand, hardly used.
Not sure on either of those, best to start your own thread in the beginners section to garner opinions.
Keep an eye out on the icetrade telescopes and mounts section as there are regularly good deals available from people trading up.
I'd also recommend seeing if you can meet up with other astronomers in your area as they will likely be happy to show you their equipment and give you a run through of the basics.
The clouds slightly parted last night and had a short look at the moon.
Using barlow and the 20mm, The moon was crystal clear very detailed and in perfect focus.
(But not as large/close as I expected) which means I need to go bigger!Or would a better bigger than 20mm help?
I already now have scope-envy, searching for either a 6 to 8 inch Dobsonian.
I gave my 81 yr old mum a peak and she said "The moon is upside down and reversed"
She was right! I was just glad it seemed to be clear and not out of alignment and hadn't noticed until a second look.
Do all Dobsonian scopes suffer that?
Neptune was also above the horizon but clouds obscured it, as well as Andromeda.
Would have been a test to have a look with this scope, maybe tonight will be less clouds.
( I know its a toy scope) but impressed with its clarity of the moon albeit reversed.
Last edited by creeksky; 29-12-2014 at 08:19 AM.
Reason: spelling
Pete
Yes all Newtonian scopes (a Dobsonian is a type of Newtonian) will invert and reverse the image. You get used to it very quickly.
While it is possible to setup a device that will correct this, it is very rarely done as you lose light every time you use a lens or mirror, and in the end does it really matter? There is no up or down in space!
Also with the size of the moon. Magnification is a function of the focal length of the scope and the focal length of the eyepiece. From memory these little scopes are f4 so they have a focal length of 76x4 or 304mm so your 20mm EP gives a power of 304/20 or 15x. So to make the moon image larger, you need an eyepiece with a shorter focal length, or a bigger scope!!
If you are looking at a 6" or 8", I would go the 8", not that much bigger but much more light gathering.
and clear.
