4.5" reflectors from Dick Smith

janoskiss (Steve H) · #1 18-01-2005, 07:06 PM

Hello everyone,

Does anyone know anything about the 4.5" Newtonian reflectors sold by Dick Smith for just under $200? See http://www.dse.com.au, and search for "114 telescope". I've had some great viewing sessions (best one on xmas night, out of town), and marvelled at the usual things first timers marvel at: moon, Saturn's rings, Jupiter's moons, few of the brighter open clusters and even the gas clouds in M42.

While I've enjoyed all that, I'm not all that happy with the scope. I'm hoping you people might be able to help me fix it up a little or tell me to stop wasting my time trying to do impossible things.

First thing was the mount. Very wobbly, but still better than some of the ones I've seen in camera shops (on scopes costing heaps more). In a gentle breeze 30x is the highest useful magnification. I built a dob mount for it and that's much sturdier. I miss the turn of the knob tracking the sky though.

The other thing is the optics. It came with 30, 10 and 6mm EPs (and two barlows that are not compatible with any of the EPs with the focuser!). The view with the 30mm EP (30x) looks fairly clear, but at any higher magnification I can't get a sharp focus. Stars are definitely not pinpoints, but kind of blurry three pronged blobs (diffraction pattern from the spider I presume). Saturn & its rings look more like an ellipse with two holes in it than two distinct objects.

A guy in a scope shop said the EPs are nothing special but they're OK and that even with a basic 4.5" reflector I should get clear & crisp views and be able to see the Cassini division, the shadow of the Saturn on the its ring and stars as points of light. Another shop did a quick adjustment of the main mirror with a laser collimator.

I had the scope out since but the view has not improved noticably. I tried the "star test" but I don't see anything that even resembles those theoretical diffraction patterns that I'm supposed to see.

So, after that bit of frustration, I made a laser collimator out of a cheap keyring laser and some plumbing bits, but it's hard to get good quality 1.25" pipe, so it's pretty rough. No improvement.

Despite the poor performance I've enjoyed the scope (or should I say the sky) enough to want more, and have ordered an 8" Dob from Andrews Communications in Sydney (I'm in Melbourne).

If possible I'd still like to fix up the 4.5", since it'd make a nice companion scope for its bigger brother, being so much lighter, smaller, and hence portable and accessible for the little people.

Any advice, secrets of the trade I'd very much appreciate.

Cheers,

ballaratdragons (Ken) · #2 18-01-2005, 07:49 PM

I have seen the scope you are talking about in Dick Smiths.

It's possible the eyepieces are Huygenian. Do they have H=30, H=10 and H=6 written on them? If so, that is 90% of your problem.

If they have K=30 etc. thats almost as bad

Please tell me what is on the eyepieces.

Tasco can be improved, so don't panic.

Bring this conversation over to the 'Equipment Discussions' forum so others can help too with suggestions from there.

iceman (Mike) · #3 18-01-2005, 08:00 PM

Agree with Ken, moving it to the Equip forum where others can pitch in.

Starkler (Geoff) · #4 18-01-2005, 08:12 PM

It is very likely out of collimation.

Find a nice medium-bright star, focus on it and rack the focuser out until you see a pattern something like this ....

http://www.iceinspace.com/image_zoom...XdTE4dC5qcGc=#

If you dont see concentric circles on stars either side of focus that is the proof. If these "circles" look triangular it is likely indicative of a pinched primary mirror, meaning the mounting clamps are too tight and distorting the mirror.(very common). The clips should only be tight enough to stop the mirror slopping about ie just touching it , but not clamping it down hard.

The secondary mirror should be directly under the focuser and appear as a perfect circle when looking square into the focuser.

You should be able to see all of the main mirror centred in the secondary mirror when you look square into the focuser (without an eyepiece)

Get yourself a plastic canister of the type that 35mm photo film comes in. Cut most of the bottom out of it leaving some material to give the walls some strength. Drill a small hole ( no more than 3mm) in the dead centre of the cap. This will fit a standard 1.25" focuser almost perfectly and will be a better collimation tool than a laser alone.

Jimmy · #5 18-01-2005, 08:26 PM

I recently bought this telescope and returned it. It is a s..t scope. The mount is as wobbly as hell... It looks hefty and strong, but it's very deceiving (it weighs a hell of allot). The tripod extension leg holder thing breaks if you just slight over tighten it. On first light, the bloody degrees/angle metres fell of and the scope flexi position adjusters just kept loosening up (the little screws the connect the flexi cable to the tripod).

The eyepieces that it is supposed to come with (as stated in manual and on box) don't come with it. 1.5x erecting eyepiece works ok on Rigel or Sirius, but you cannot achieve a good focus. The 2x barlow, forget it. Everything went fuzzy and blurry. The barlows are not compatible with the focuser (you take it to the limit, it looks like your getting there and boom, can't focus anymore.) You know at the front of a newtonian...the mount where the second mirror sits the looks like a cross... thats what the stars come out as..... unbeleivable shadowy crap.

The eyepieces are Super Plossl (made in China). 6mm 10mm and 30mm (or 32mm can't remember..... I returned it and got the 8" GSO DOB and a Meade ETX70AT remember!!).

The 32mm and 10mm is great for zooming in on the moon, but when attaching a barlow you can lose focus (even on a full moon with moon filter attached).

I thought S...t what a bargain when I bought it...but pffft what a piece of crap even after collimation. A terrible buy. Don't be deceived by cheap electronic store crap..... Maybe one in a thousand might be lucky to get something good if they bought one of these....

Get the 6" or 8" GSO Dobs.

Since you've bought it and modded it, try your best to make it work. Sheesh Im lucky I got a refund..............

Good Luck

ballaratdragons (Ken) · #6 18-01-2005, 08:34 PM

Also, if I remember correctly, on the box it was called a 'Refractor' telescope

and it was priced at $95

'come in spinner!!'

MintSauce (Gordon) · #7 18-01-2005, 09:33 PM

gee jimmy, I thought we were helping you decide what scope to buy and we ended up making you buy 2! Wish I could afford that - tell me how much the ETX70 comes to after frieght from US please.

janoskiss (Steve H) · #8 18-01-2005, 10:51 PM

Thanks for the feedback everyone.

Several point were made. Here are my thoughts:

1. Eyepieces.

They are not Huygens' or Kellners. They are (super) Plössl, and the focal lengths cover a sensible range: 30, 10 & 6mm.

I had these looked at by some one in York Optical's shop in Melbourne, and I went there with the intention of buying one or two better eyepieces (willing to spend $100 on one), and I let the guy know that I want better EPs. He checked them out in a $2000+ refractor and told me not to waste my money, cos they were fine.

2. Collimation

You don't see nothing like Starkler's image of concentric circles with this thing. I think thick spider vanes dominate the visual appearance of the diffraction pattern. The pattern is not "triangular" though, so probably no pinched mirror. I can see some arcs of circular fringes within the approximately 3-fold symmetric pattern. Adjustments of the main mirror don't seem to improve the pattern (just worsen it if I take it far enough).

As for 35mm film canisters... I presume Starkler has been using digital cameras for a while, because all film canisters these days seem to be made from the same mould and are over 32mm in diameter, so they do not fit the 1.25" focusers. (I do not buy Kodak though, since I found out years ago that they're abandoning the chemical medium of traditional film alltogether, going the hard sell on digital. So much knowledge, down the toilet! What a shame!)

3. The scope is crap.

Thanks Jimmy, for the brutal honesty and well done for getting a refund. It's good to hear some one else bought this thing and found the exact same flaws as I found. I may have been more forgiving though...

After my first look at the moon, I was too excited by the view and quickly sliced up most of the cardboard packaging and put it in the recycling bin. At that point I was committed not to return the scope.

Yes there are many dodgy things about the scope, but you can put up with some defects and work around others.

The mount is very shaky but still usable at low power (30x), and, with a lot of patience, at moderate power (90x). My home made dob mount is a lot more useful.

Several things don't fit, including the finderscope mount. I had to hacksaw one corner of the mount because the focuser got in the way even at extreme adjustment.

I can work with/around all these and several other quirks, but there is one problem I can't solve. I have to quote Jimmy here, because he's _spot on_

"You know at the front of a newtonian...the mount where the second mirror sits the looks like a cross... thats what the stars come out as..... unbeleivable shadowy crap."

Amen brother! _I've been where you've been and seen what you've seen and it ain't pretty!_ You can't actually get a sharp focus. The fuzzy view makes you constantly want to try adjusting the focus but all you get is more blur.

This is precisely what I want to solve. What causes this? If collimation doesn't fix it (and it seems not to), then it must be the main mirror, right? Should I get the mirror out and start grinding away?

I've invested so much time and around $250 in this scope, so I would really like to get to find out exactly what is wrong, and if it's fixable.

It's a beautifully clear night in Melbourne tonight, so now I'm going out to the backyard to check out the setting Moon & Saturn. (making the most of my fuzzy DSE scope :-)

BTW. Can anyone guess who the manufacturer is?

ballaratdragons (Ken) · #9 18-01-2005, 10:58 PM

TASCO?

TONKA?

MATTEL?

TANDY?

Am I close yet?

ving (David) · #10 18-01-2005, 10:59 PM

just 2 words...

go buy the 8" dob cause it will be a huge improvement over yous wobbleotronic

welcome to the forum

ballaratdragons (Ken) · #11 18-01-2005, 11:04 PM

Hey Ving,

Is Wobbleotronic a proper scientific term? lol

janoskiss (Steve H) · #12 18-01-2005, 11:48 PM

Back from a quick look at the Moon and Saturn. I still enjoy looking at them through this crappy scope. I could clearly see two moons of Saturn this time.

As for the 8" Dob, I have already ordered it from Andrews Comm. and it should be here within a couple of days.

What makes my crappy 4.5" scope so crappy, I would still like to find out anyway.

ving (David) · #13 19-01-2005, 01:13 PM

Quote:

Originally posted by ballaratdragons
Hey Ving,

Is Wobbleotronic a proper scientific term? lol

more of a brand name i think...

i have a wobbleotronic refractor.

ballaratdragons (Ken) · #14 19-01-2005, 01:19 PM

Did you try everything Starkler suggested?

They are valid pionts and common on some scopes (even expensive ones).

janoskiss (Steve H) · #15 19-01-2005, 02:42 PM

Yes and no.

Sorry for the long post earlier, obviously too long for people to read, which is fair enough, so the gist of it is:

Starkler's advice on collimation I could only take as far as the visual inspection thru the focuser, and it looks OK.

Film canisters do not fit in the focuser.

The star test is a bit hopeless. You can see some fuzzy arcs of circular fringes, and I can't really improve on it at either mirror.

In a scope shop I was told to only adjust the secondary mirror when doing the star test, and I should leave the primary alone. But my not-so-common sense tells me that I should adjust the secondary first until centre of main mirror appears in centre of view at the focuser (easy with a laser) and then adjust the main mirror (so that with a laser the incident & reflected beams follow the same path).

Have I got this right? Then I can try the star test and fiddle with which mirror?

ballaratdragons (Ken) · #16 19-01-2005, 03:06 PM

Hi Janoskiss,

You will need a tube that fits the focuser with a small hole in the exact centre.

Look through the hole at the diagonal mirror. If the Diag is in it's proper place you should see the end of the tube with the Primary mirror dead centred. If not, adjust the positioning screws on the diag until the Primary mirror is dead centre. If you get it right the Primary should take up all or almost all of the diag.

Now look for the image of the diag in the Primary. It should appear in the centre. If not, you can adjust the Primary cell with the adjusters at the back of the mirror cell.

When all is lined up you should see the Diag itself centred in the field of view, an image of the primary filling the diag, a reflected image of the diag centred in the primary and your own eye, seen by double reflection, centred in the diag.

Try that and get back to us.

Good luck!

ballaratdragons (Ken) · #17 19-01-2005, 04:18 PM

Hey Janoskiss,

I just looked at the Dick Smith site. Thats a different model to the one for sale down here.

Dick Smith here has a 3" Reflector (labelled as a Refractor), it's white, Huygenian eyepieces, only $95 and a peice of crap.

Yours might be o.k. Sorry about that, I should have looked at the Dick Smith site first.

Jimmy · #18 19-01-2005, 05:19 PM

all this trouble for a cheap 4.5" relector..... thats why you don't buy from cheap electronic store/depaaato stores

Starkler (Geoff) · #19 19-01-2005, 06:21 PM

Quote:

Originally posted by janoskiss
Yes and no.

Starkler's advice on collimation I could only take as far as the visual inspection thru the focuser, and it looks OK.

Meaning you cant see the primary centred in the secondary?
Adjust secondary tilt to remedy.

Quote:

Film canisters do not fit in the focuser.

Perhaps your eyepieces are 0.95inch and not 1.25inch ?

Quote:

The star test is a bit hopeless. You can see some fuzzy arcs of circular fringes, and I can't really improve on it at either mirror.

Means primary mirror collimation is way out.

Quote:

In a scope shop I was told to only adjust the secondary mirror when doing the star test, and I should leave the primary alone.

This bloke has no idea!

Quote:

But my not-so-common sense tells me that I should adjust the secondary first until centre of main mirror appears in centre of view at the focuser (easy with a laser) and then adjust the main mirror (so that with a laser the incident & reflected beams follow the same path).

Have I got this right? Then I can try the star test and fiddle with which mirror?

Pretty much right although a tiny error in hitting the centre of the primary is magnified when centering the return beam at the focuser. This is why lasers alone arent a complete solution for collimating a scope.

It will help a great deal if you centre spot your mirror. (see google).
Once you get this far, tweak the primary mirror for best star test image.

janoskiss (Steve H) · #20 19-01-2005, 08:11 PM

Starkler wrote: "Meaning you cant see the primary centred in the secondary?"

No... meaning everything looks fine (nicely centred) when I look at the reflection of my eye in the focuser.

About the film canisters not fitting... The scope does have 1.25" / 31.7mm focuser (actually its a bit oversized with the EPs quite sloppy). You guys probably have been using digital cameras too long. Recyclable film canisters these days all seem to be about 1/2-1mm bigger than 32mm in diameter (Agfa, Fuji, other noname brands I bought Europe).

As for the bloke in the shop not having any idea, well, he fooled me. He seemed like an old timer who knows what he's talking about, and was very helpful (or at least willing to be) and instead of trying to sell me stuff he talked me out of buying "upgrades" (EPs & mount).

For now, I'll wait for the laser collimator I ordered with the Dob from Andrews to get here, and see how I go with it then.