Newtonian claiming to be more than it is

[niko]

Hi all,

I've been testing a small newtonian on a manual eq mount (more on that later).

It states that its focal length is 1000mm but the OTA is clearly shorter than that (more like 500mm). It has an extension tube between the focusser and the eyepiece - is that what makes the focal length 1000mm or it is just a case of a lemon in sheep's clothing??

any comment warmly welcomed.

thanks.

niko

[desler]

I don't know how you work it out, But I'm glad to see there has been another purchase in the Family!!!!


Darren

[rmcpb (Rob)]

If the tube is half the focal length then you can almost bet your savings that there is an inbuilt 2x barlow in the focuser. I would tend to avoid such scopes.

Cheers

[Blue Skies (Jacquie)]

Yep, inbuilt barlow at the bottom of the focuser. No , don't stick you finger on it to test that it's there! These scopes will give you average views but if you're trying to get serious about a telescope I'd be looking at something else.

[ausastronomer (John Bambury)]

Originally Posted by Blue Skies

if you're trying to get serious about a telescope I'd be looking at something else.

Jaqui has given you very good advice. Optically these scopes leave a lot to be desired. For similar money you can buy an infinitely better scope optically and mechanically than one of those. I would avoid it if you can.

Cheers,
John B

[TrevorW]

Cheap is as cheap does.

If it sounds too good to be true then it usually is.

A good starter book for amatuers is "All about telescopes" by Sam Brown published through Edmund Scientific may be still in print.

[Ian Robinson]

Originally Posted by TrevorW

Cheap is as cheap does.

If it sounds too good to be true then it usually is.

A good starter book for amatuers is "All about telescopes" by Sam Brown published through Edmund Scientific may be still in print.

Think they saw him coming .... hope he didn't throw many $ at it.

[Glenhuon (Bill)]

I bought one of those too at first. Best advice is, look elsewhere.

Bill

[Screwdriverone (Chris)]

I have a similar Telescope design called a Catadioptric Newtonian, Diameter = 130mm, OTA length 500mm, FL=1000mm due to the 2x lens built in between the Primary and the secondary which focuses the primary's parabolic light onto the secondary and is supposed to remove or minimise coma and other false colour issues.

I had no end of dramas with collimation and ultimately had to get the OTA replaced as it couldnt be collimated to a point that allowed proper focus.

Now that I have a new OTA, the problem has been resolved but for a small newtonian (or any for that matter) I would steer clear of these as a beginner as it just creates too many headaches and introduces another point of failure and complication you just dont need.

Buy a normal length simple Newtonian Dobsonian or GEM mounted tube and enjoy the simplicity instead.

Seriously.

Chris

[niko]

Once again thanks to all within this community for the well considered responses to my query.

I should mention that I am currently assisting a nationwide retailer of related equipment in considering stocking astronomy equipment. It is my hope that they can provide budget priced but reasonable quality equipment in order to promote the hobby/passionate past-time to a wider audience. It is my genuine hope that they will not be in competition to the specialist stockists but rather provide a better alternative to the "toy" store retailers and be in better symbiosis with the specialists. I believe that with an emphasis on customer service and staff training that they can do a lot to bring this hobby to a wider audience. This in turn will hopefully lead to more adopting the hobby and then moving on to better equipment from the specialists (like we all have!!!).

So, once again, thanks for the great feedback and comments it will greatly assist in making better informed decisions.

I should hasten to add that my assistance to this retailer is being provided free of charge in the genuine interest of promoting the hobby - no cash for comment here!!!

If anyone in Melbourne would like to test some of the scopes I'm sure that could be arranged - the more thorough the testing and the more expansive the feedback the better the final result will be.

Thanks again everyone.

cheers

niko

[TrevorW]

I think cheap telescope's do astronomy a dis-service. Promoting high magnifcation and advertising with images that are unacheivable even through larger more expensive telescopes.

How many kids have been put off astronomy by parents buying scopes based on low prices and false or misleading advertising, it really should be banned.

An honest non-specialist ie: other than dedicated astronomic retailer providing and promoting decent scopes at reasonable prices (which is possible with the current exchange rate) without seeking massive mark ups would be a breath of fresh air to the hobby.

Hope things work out well

[Starkler (Geoff)]

The problem with many toy telescopes is that they are often just as expensive as the cheaper real telescopes capable of good performance.

A person looking for their first telescope who has no idea where to look or who to ask for help has to navigate an enormous minefield of ebay type rubbish and clueless camera store type dealers also promoting rubbish.

For mine I wouldn't be selling anything under $600 that wasn't a dobsonian or a small refractor on a alt-az mount of usable sturdiness.

[niko]

Totally agree with your comments - sadly those that visited the factory ignored some of my initial advice and brought back products of inferior quality but I am hoping there is still plenty of wriggle room on a final decision.

Certainly my bottom line is not to bother unless the products offer good value and reasonable seeing otherwise they are doing themselves and the public a dis-service.

n

[Starkler (Geoff)]

If it were my store I would probably have a couple of toy scopes on display if space allowed purely for the purpose of educating buyers on what not to buy and why.

[chris lewis]

Just to confirm what most have said.
I fix and repair 114 mm and 150mm short tube ‘no name ‘reflectors for a local distributor here in Auckland New Zealand.
These telescopes are not recommended.
This design is called a ‘Bird -Jones’ reflector. Occasionally there are also incorrectly referred to as ‘Catadipotrics’ reflectors however this is more to do with advertising and is really misleading.
It uses an inbuilt ‘corrector' lens to increase the focal length. The mirrors used are spherical. The corrector lens attempts to reduce the inherent aberrations and distortions found in spherical mirrors- like marked coma.
They are notoriously difficult to collimate. Images become distorted even at relatively low magnifications.
These designs are not recommend for astro use as they give inferior images.
Money is much better spent on a long tube design with a parabolic mirror. If it is longer then F/7 or F/8 spherical mirrors can work reasonably well.

[Stephen65]

A small refractor of decent quality is a lot easier instrument for absolute beginners to use than Newtonians that require collimation.

The other vice of the awful telescopes that department stores and camera shops sell is that they are usually very under-mounted.

[ausastronomer (John Bambury)]

Originally Posted by Stephen65

A small refractor of decent quality is a lot easier instrument for absolute beginners to use than Newtonians that require collimation..

Whilst a small refractor is what got a lot of people into astronomy, it is also what got a lot of people out of astronomy. This occurs through sheer frustration at the poor finderscope, wobbly mount or the inabality to basically see anything. A small refractor, even a good quality one, provides very uninspiring views of most targets, except Jupiter, Saturn and the Moon. This is particularly so in the case of new observers whose observing skills haven't developed. This is why a small dob in the 6" to 10" size range is an infinitely better instrument for a beginner to start with IMO. They can actually see something with it, it has a decent finderscope, unlike most small refractors, provides a stable observing platform and is very easy to steer and control. The only thing they have to do is learn to collimate it, which isn't that difficult.

Originally Posted by Stephen65

The other vice of the awful telescopes that department stores and camera shops sell is that they are usually very under-mounted.

Another reason why a small/medium dob is a better option. Most cheaper telescopes apart from small to medium dobs are very poorely mounted. By comparison just about all small to medium dobs, whilst still inexpensive, are fairly well mounted and very user friendly.

Cheers
John B

[g__day (Matthew)]

When I picked up a second hand Williams Megrez 80SD for about $400 it had real value. I had gone Newt 6" -> Mak 5" -> SCT 9.25" -> Refractor 3.5" and the sharpness of stars and contrast with the night sky was simply put very impressive. Once I added a 10:1 microfocuser I was in heaven.

A good quality, smaller refractor is a delight when paired with decent diagonal and better than average eye pieces. That said buying better than decent eye pieces of sizes 5mm, 8mm, 11mm, 13mm, 18mm, 22mm and 25+ mm is likely to set one back maybe $2K. And a decent mount to set everything up on is around $1.5K minimum.

So the entry costs are high when you add say 1-2 very decent eye pieces a EQ5 mount and your OTA + attachments. Maybe retailers should try and promote more astronomy clubs - so users could share and swap eye pieces and see the capabilities of different types of OTAs and mounts.

Otherwise it means a 8" -> 10" Dob plus 1-2 good eye pieces is your best lug-able starting point.

[marki]

Yep, an 8 inch dob @ F6 or there abouts is pretty hard to beat as a first scope. Its simple, stable, has a wide field of view, is not too big to store and best of all does not require a big investment. Collimation is reasonably simple to achieve as long as the manufacturer has put the centre spot on and taken the time to make sure the secondary and primary mirrors are properly mounted. I recommended a neighbour buy one a couple of years ago and both he and his young son have had a ball becoming hooked on astronomy which is what a good first scope should do. Whats more they use it often as it is easy to set up and we all know the best scopes are the ones that get used.

Mark

[Blue Skies (Jacquie)]

Originally Posted by niko

I should mention that I am currently assisting a nationwide retailer of related equipment in considering stocking astronomy equipment. It is my hope that they can provide budget priced but reasonable quality equipment in order to promote the hobby/passionate past-time to a wider audience. It is my genuine hope that they will not be in competition to the specialist stockists but rather provide a better alternative to the "toy" store retailers and be in better symbiosis with the specialists. I believe that with an emphasis on customer service and staff training that they can do a lot to bring this hobby to a wider audience. This in turn will hopefully lead to more adopting the hobby and then moving on to better equipment from the specialists (like we all have!!!).

I've been debating whether to add any further comments in this discussion since you admitted this, but wasn't so much niko's remarks as some of people following on that have prompted this reply.

I once tried to get into the telescope selling game. Let's just say it didn't go well and there are things that happen behind the counter that I wish some you 'buyers' out there could see. It would help you understand why the 'junk' telescopes are still around and plentiful.

There are always people who just don't have the budget, but mean well. These aren't the people you need to worry about as they will most likely make the best of what they get and move on bigger things several years down the track.

I could probably put the rest into several loose categories. There are people who just wanted a cheap scope for the kiddies and the people who want a scope that will do both daytime and nighttime equally well. There's also a group of people who don't want to take the time to educate themselves (or its too difficult to) and a group who think "its too big, I wont need that." All these people will choose to purchase the cheap 'junk' we deplore.

The cheap scope for the kiddies Christmas stocking is a necessary evil, unfortunately, it keeps the cash flow going and lets the retailer pay the rent and maybe buy some of those bigger and better telescopes for the serious people.

The daytime/nighttime people usually take refractors as they are easier to convert to daytime use with the use of an inverting prism. They also usually don't want anything too big.

Education is a big issue, there is so much to impart to a person without telescope experience that you can overload them quite easily and make a choice more difficult. Trying to get the info across in an easy to understand manner is real skill.

The 'too big' people are self explanatory!

Other factors you don't see are the factory suppliers trading terms, which might surprise you. The reseller is sometimes at their mercy.

The bottom line is that you can't have stock sitting around gathering dust and the it's minority who buy the 'good' stuff and the majority who buy the 'junk' that pays the bills. The cycle just repeats on itself and I expect will continue to do so for some time.

Staff education is going to be crucial if the store is going to succeed in it's aims. Good luck to them! If they're truly a nationwide chain and can make a difference here in Perth I'll tip my hat to them, for sure.