Which of these Barlows should I buy?

[D Med]

54 minutes ago, Charic said:

You're not supposed to remove the corrective lens.

This type of telescope can be collimated by eye alone, no tools if the user needs. Its a spherical  mirror setup, you just need to see the mirror clips,  its in the user guide, but you could send it back  to get it collimated, but they'll do just the same, and charge you for it?

In order for the system to work with the eyepieces the corrector lens needs to be in place, so why remove it!!!!! 

I went the whole hog, strip, cleanse, build, adjust, collimate, no better, even with better eyepieces. 

I took the lens out to use a laser collimator, then I put the lens back when I was done.

[Charic]

15 minutes ago, D Med said:

I took the lens out to use a laser collimator, then I put the lens back when I was done.

That you did, but a spherical mirror is  for practical reasons, immune to misalignment on axis, so as long as you can see the three primary mirror clips as viewed through the focuser housing, your primary mirror will be setup as good as it can be. You don't need a laser or to strip the scope.

 

[John]

I've collimated a few scopes of this design and found the easiest and most accurate way was to use an artifical star several metres away from the scope rather than removing optical componants. That way at least you can be confident that the optical system as a whole (ie: primary, secondary, corrector and focuser optical axis) are reasonably well aligned rather than having to re-assemble things post-adjustment.

I use one of these relatively low cost artificial star generators:

https://www.firstlightoptics.com/other-collimation-tools/hubble-optics-5-star-artificial-star.html

 

 

[Alan64]

49 minutes ago, D Med said:

I took the lens out to use a laser collimator, then I put the lens back when I was done.

About your laser collimator, if similar to this one...

...they usually arrive, more often than not, with the need to be collimated themselves, and before using to collimate a telescope; else, it can worsen the collimation of a telescope.  In any event, I prefer the old-school tools, a Cheshire or collimation-cap, or both.  The kit at hand is an ideal candidate with which to learn about reflectors of all designs.  Indeed, once one learns to collimate a Newtonian or similar successfully, no design of telescope will remain a mystery.  I should include that when removing the lens assembly, it must be returned in the same order as it was before.  I've made it a practice to take multiple photographs when breaking down a telescope, and a very good practice at that.

[tonyowens_uk]

3 hours ago, Alan64 said:

I'll tell you what I will be doing to mine, when I get it.  First, I'll take the telescope completely apart.  I'll place a polyvinyl(plastic, not paper) notebook reinforcement precisely in the center of the primary-mirror...

That way, I can use a collimation-cap...

I will then be able to see the exact nature of the collimation, and at a glance...

...and correct it where necessary.  But I'll need to remove the barlowing-element beforehand, and whilst I have it out, I'll blacken the edges of the lenses with chalkboard-black paint...

The inside of the drawtube would also be blackened with same, even over that of the factory's.  The paint I use is blacker than Synta's, incidentally.  The edge of the secondary-mirror , its backside, and the spider even, would get it too...

Not to mention anything else inside the tube that might reflect stray-light sources; shiny, black plastics...chromed nuts and screws...

...and all to improve contrast, to be seen to be believed when observing.  I viewed the Trapezium of Orion recently with a recently blackened and flocked telescope.  Instead of the edges of the grey cloud-like nebula blending and oozing into a not-quite-black sky background, the edges of the nebula stood out in stark contrast against a jet-black background. 

Flocking is like very-low pile carpeting... 

http://www.fpi-protostar.com/hitack.htm

All telescopes that come out of China, the tube interiors are of a greyish black paint, and with a bit of rust as a "bonus".  Apparently the unpainted, steel tubes are not kept in a dry place before the paint is applied...

Even the tubes of the more costly Schmidt- and Maksutov-Cassegrains appear as that on the inside, I'd wager.

In the end, you want the inside of any telescope to be utterly dead to all sources of stray light.  Contrast: that's what it's all about; mostly anyway.  The same goes for refractor diagonals and any other accessories that have reflective, shiny surfaces within.

 

With respect I wouldn't agree with your comments about Synta telescope tubes Alan and how they are made and painted. A just-in-time procedure is used to convert flat cut tube blanks into welded tubes, these are machined, epoxy powder painted on a first class automated line, and matified internally. I've actually seen the entire process of making these scopes relatively recently. No corners were being cut. They use a semi-automated manufacturing system that pays as much attention to quality assurance in beginner scope models as in semi-pro models. 

Tony Owens

[Alan64]

2 minutes ago, tonyowens_uk said:

With respect I wouldn't agree with your comments about Synta telescope tubes Alan and how they are made and painted. A just-in-time procedure is used to convert flat cut tube blanks into welded tubes, these are machined, epoxy powder painted on a first class automated line, and matified internally. I've actually seen the entire process of making these scopes relatively recently. No corners were being cut. They use a semi-automated manufacturing system that pays as much attention to quality assurance in beginner scope models as in semi-pro models. 

Tony Owens

I have several of these Synta telescopes, Newtonians and refractors.  The deplorable finish on their interiors is just that; the same rusty, grey-black finish.  However, I just shone a light into the tube of Synta Maksutov here in the household, and I didn't see the orangey cast to the usual grey-black finish, therefore perhaps the Cassegrains are exempt?

[D Med]

Yes, my laser collimator is collimated, too. I already knew to do that in advance. 

[tonyowens_uk]

23 minutes ago, Alan64 said:

I have several of these Synta telescopes, Newtonians and refractors.  The deplorable finish on their interiors is just that; the same rusty, grey-black finish.  However, I just shone a light into the tube of Synta Maksutov here in the household, and I didn't see the orangey cast to the usual grey-black finish, therefore perhaps the Cassegrains are exempt?

My observations are reconcilable with yours Alan. All Synta scopes all are manufactured on the same lines using the same machinery and similar materials. I don't know whether any of the Mak's and SCT's use steel tubes. The differences in the various scope lines Synta produce are principally about the nature of the design engineering solutions applied, not the quality of the manufacturing processes. Its always possible to boost the quality of the design solution using things like microfibre light trapping fabric. The cost of this is not insignificant however relative to the cost of the rest of the scope.

Tony Owens

[Alan64]

7 minutes ago, tonyowens_uk said:

My observations are reconcilable with yours Alan. All Synta scopes all are manufactured on the same lines using the same machinery and similar materials. I don't know whether any of the Mak's and SCT's use steel tubes. The differences in the various scope lines Synta produce are principally about the nature of the design engineering solutions applied, not the quality of the manufacturing processes. Its always possible to boost the quality of the design solution using things like microfibre light trapping fabric. The cost of this is not insignificant however relative to the cost of the rest of the scope.

Tony Owens

Synta's Schmidts and Maksutovs may have aluminum(hopefully not plastic) tubes, as I just held a magnet to that of this Maksutov on hand, and it didn't stick.  I suppose, in the end, one gets that for which they pay.

Incidentally, Celestron began, originally, producing only Schmidt-Cassegrains; Tom Johnson and all that.  Naturally, Synta is going to prioritise the manufacturing of those; special handling. 

Other than those, the outsides of Synta's steel tubes are finished rather nicely.  Would that the insides were just as nice, and where it really counts, but alas...

   

Incidentally, that's one of Synta's Orion-branded products, before.  And after...

https://www.firstlightoptics.com/misc/black-velour-telescope-flocking-material.html

That doesn't seem to be too terribly costly.  One might flock quite a few smaller telescopes at that price; and a rattle-can of paint from the local hardware is next to nothing.

In any event, you do get your money's worth, for the most part, fresh off the boat.  But there's just something about them that leaves one with a burning that they're just not quite finished, polished; hence, my enhancements and improvements, and that most anyone may perform; simple arts and crafts.

[Stub Mandrel]

While I would concur that the 'matt black' paint inside these scopes isn't as flat as it could be, I can't see any signs of rust on any of my three synta scopes (2 newts and a mak). Do all your scopes show the rust as well?

The journey from factory to customer is along one; it is possible that yours have been stored in damp surroundings on their journey?

Another possibility is that some importers save money by buying QC rejects that don't make the cut for higher-paying customers, but I think this is unlikely if the scopes you refer to are the ones in your signature.

[Alan64]

4 hours ago, Stub Mandrel said:

While I would concur that the 'matt black' paint inside these scopes isn't as flat as it could be, I can't see any signs of rust on any of my three synta scopes (2 newts and a mak). Do all your scopes show the rust as well?

The journey from factory to customer is along one; it is possible that yours have been stored in damp surroundings on their journey?

Another possibility is that some importers save money by buying QC rejects that don't make the cut for higher-paying customers, but I think this is unlikely if the scopes you refer to are the ones in your signature.

I have not seen the orange cast within the tubes of the Zhumell 100mm f/4 Zhumell(GSO?), nor the Meade 90mm f/10(Ningbo Sunny); but I have seen it within the Celestron 70mm f/13 and the Orion(of California) 150mm f/5, both Synta products.  The detriment goes so far as to impart a colouration, a hue, to the Moon when taking an afocal photograph through same.  Mind you, it's not rust outright, rising above the surface, flaking, but it's bad enough as it is.

All of said telescopes were purchased new, with their dust-caps in place, well-packaged, bagged with dessicant packs, therefore I'm quite convinced that the slight rust was present before the tubes were even painted.  I can envision a warehousing there, where the steel tubes are stored prior to being finished, and all that that entails.

In any event, the grey-black paint utilised could be blacker, and blackest even.  It's almost 2019.  There's no excuse otherwise.  It's apparent that the manufacturers expect the end-users to complete these telescopes, and that's not just the paint.

[tonyowens_uk]

On 28/12/2018 at 13:54, Alan64 said:

I have not seen the orange cast within the tubes of the Zhumell 100mm f/4 Zhumell(GSO?), nor the Meade 90mm f/10(Ningbo Sunny); but I have seen it within the Celestron 70mm f/13 and the Orion(of California) 150mm f/5, both Synta products.  The detriment goes so far as to impart a colouration, a hue, to the Moon when taking an afocal photograph through same.  Mind you, it's not rust outright, rising above the surface, flaking, but it's bad enough as it is.

All of said telescopes were purchased new, with their dust-caps in place, well-packaged, bagged with dessicant packs, therefore I'm quite convinced that the slight rust was present before the tubes were even painted.  I can envision a warehousing there, where the steel tubes are stored prior to being finished, and all that that entails.

In any event, the grey-black paint utilised could be blacker, and blackest even.  It's almost 2019.  There's no excuse otherwise.  It's apparent that the manufacturers expect the end-users to complete these telescopes, and that's not just the paint.

As I've said Alan there is no warehousing of tubes at Synta - so unless your scopes are some years old that cannot be a factor. I've inspected the manufacturing setup used in person and its leading edge.

As for the scopes themselves - these are cheap instruments that nevertheless need to be packed and shipped internationally, and make margin for the importer, the supplying dealer, and Synta. Deduct that from the retail price and the residual has to cover a large mechanical parts count, running a vacuum evaporation plant, manufacture of diffraction-limited optics, assembly and warranty costs. Looking at the numbers, these scopes are amazing bargains. So what if the focusers are basic, or the tubes a bit heavy, or the blacking less than ideal. Half the people who buy these scopes have technical or scientific backgrounds and many will be well able to flock a tube, upgrade a focuser or apply blackboard paint to the interior if they are bothered.

Unless your experience of rusty tubes has been reported by other users I'd say yours are not representative. Do other users have this problem?

[Alan64]

35 minutes ago, tonyowens_uk said:

As I've said Alan there is no warehousing of tubes at Synta - so unless your scopes are some years old that cannot be a factor. I've inspected the manufacturing setup used in person and its leading edge.

As for the scopes themselves - these are cheap instruments that nevertheless need to be packed and shipped internationally, and make margin for the importer, the supplying dealer, and Synta. Deduct that from the retail price and the residual has to cover a large mechanical parts count, running a vacuum evaporation plant, manufacture of diffraction-limited optics, assembly and warranty costs. Looking at the numbers, these scopes are amazing bargains. So what if the focusers are basic, or the tubes a bit heavy, or the blacking less than ideal. Half the people who buy these scopes have technical or scientific backgrounds and many will be well able to flock a tube, upgrade a focuser or apply blackboard paint to the interior if they are bothered.

Unless your experience of rusty tubes has been reported by other users I'd say yours are not representative. Do other users have this problem?

I said nothing as to their being overweight.  After all, in this day and age, plastic has replaced metal within these kits.  There's nothing wrong with a focusser being basic, but as for the bearings for the drawtubes being poorly executed, actually a joke, resulting in considerable slop, not to mention collimation misalignment, making collimation more difficult, is quite another matter...

What do you make of those bearings?  I think they're a lot like a corrugated strip from a packaged pastry's liner...

I've found that PTFE(Teflon) strips instead makes for a marked improvement...

The vast majority who purchase these entry-level kits never open the tubes of their refractors, nor do I think that they would notice the detriment within their Newtonians, either, as they do perform "good enough".  I didn't notice it until I broke the Orion Newtonian down.  The two Synta telescopes that I have were purchased about six years apart.  It seems to be a going concern.  A coincidence that both exhibit such, and no others?  I don't think so.