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Sky-Watcher Evostar 72ED DS-Pro OTA

FLO

By FLO
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FLO

FLO

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20 minutes ago, Stub Mandrel said:

Ha.

The Mitutoyo caliper does not lie, they are strictly not metric form as they have sharp crests that take them 0.33mm over size :icon_biggrin:

The female threads are probably cut with a sharp root too.

Not sure I understand, has your Mitutoyo caliper confirmed it is M54? 

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RayD

RayD

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I can confirm for visual this little thing is a gem. Had it out last night with WO 2" diagonal and ES 18mm 82 degree and it was spot on. Pin point stars, focuser silky smooth and no slip. Being critical I would say there was the slightest hint of CA way at the edge of the reasonably large FOV, but nothing that you wouldn't expect from even a very hight quality doublet. 

FPL53 or not, this is a stonking little travel scope. 

Can't confirm for definite on thread size which is why I deleted my post as I don't want to confuse things, but it measures at M54, although I do have some adaptors to try so will confirm either way. 

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FLO

FLO

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35 minutes ago, gtis said:

Sure is 

Is the dew sheild on a bayonet fitting

or just push on

It is push-on. It is quite a firm fit. When I first tried removing it I concluded it wasn't supposed to come off then I read RayD's post saying he had removed his. So I pulled a little harder, and off it came :smile: 

I daresay it will come off more easily over time but I cannot think of why you would want to remove it, unless you want to pack it in a case smaller than the one already supplied. I removed it only because I wanted to photograph the optics. 

HTH, 

Steve 

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Stub Mandrel

Stub Mandrel

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9 hours ago, FLO said:

Not sure I understand, has your Mitutoyo caliper confirmed it is M54? 

Metric threads (see diagram above) are meant to be flat on the top of the thread form and have rounded bottoms to the grooves. This means you can cut a metric thread by turning or boring the blank to size then cutting the thread with a tool that has a 60 degree point with a rounded tip (for long life). In fact by changing the feed rate (easy on a well set up CNC machine) you can cut a perfect thread with two passes of the same tool.

The Skywatcher adaptor is clearly meant to be an M54 thread, but it seems they cut the thread with a sharp pointed 60-degree tool plunged to give the correct thread minor diameter for M54, but use an oversize blank. This means the top of the thread form is left sharp and has the effect of the OD being about 0.3mm oversize.

If the matching internal thread was a perfectly formed M54 thread, they wouldn't work together, but it looks like they use a sharp pointed tool to cut the internal thread (or cut the internal thread a touch deep) and everything works OK.

When I made the parts for my scope I cut the drawtube so the Skywatcher adaptor of my 130P-DS fitted it, and made my adaptor to fit the 130P-DS drawtube. As I then found another Skywatcher adaptor the happy result is three adaptors and two drawtubes, all interchangeable. My approach to screw cutting is always to make them to fit rather than relying on  the theoretical sizes coming out right :icon_biggrin:

My impression is that most filters/adaptors/t-mounts use sharp-topped threads. I hate to say it but this is probably fine because such things are generally made quite an easy fit, as they are repeatedly assembled and dis-assembled and tight fitting threads would be liable to galling and cold welding. No-one wants to put copper-ease on their telescope accessories!

 

I've just measured the external threads on several 1.25" filters. These are meant to be 1.125" by 42 tpi. They are ALL sharp topped and vary in diameter from 1.111" to 1.119", plenty undersize enough to mate with a 1.125" female thread. They are too small to judge if they are 60 degree metric or 55 degree whitworth form.

I am NOT going to cut a filter in half to see how accurately made the internal thread is :icon_biggrin:

<edit> It seems some 1.25" filters use 28mm x 0.6mm pitch. Cutting the male thread undersize (whichever spec you use) should allow them to fit together well enough in this far from critical application)</edit>

Bottom line, none of this really matters UNLESS you are asking someone to make you a custom adaptor or accessory in which case I would recommend giving them any unusual mating parts.

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FLO

FLO

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55 minutes ago, Stub Mandrel said:

Adaptor bottom left, drawtube top right :-)

Your ED66 project? :smile: 

It must be immensely satisfying making a scope that fulfills your needs precisely and to such a high standard of workmanship. I will watch with interest. 

Steve 

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Shera

Shera

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Can someone tell me (as a Newbie) will this work with my Canon DSLR T ring adapter and is it capable of photographing and viewing deep sky objects like galaxies as well as planets? I've got a Star Adventurer as a mount. I've got a Skywatcher Explorer reflector scope which came with 1.25" 10mm & 25mm eyepieces and a x2 Barlow lens, would these be ok to use as I noticed it says it doesn't come with any eyepieces? Thanks.

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SilverAstro

SilverAstro

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10 hours ago, Shera said:

Can someone tell me (as a Newbie) will this work with my Canon DSLR T ring adapter and is it capable of photographing and viewing deep sky objects like galaxies as well as planets? I've got a Star Adventurer as a mount. I've got a Skywatcher Explorer reflector scope which came with 1.25" 10mm & 25mm eyepieces and a x2 Barlow lens, would these be ok to use as I noticed it says it doesn't come with any eyepieces? Thanks.

I guess your DSLR T-ring/adapter? is 1.25" so you will need a 2" to 1.25" adapter, I think. ( I have not yet done anything yet in that line with my DSLR.) or a 2" T jobbie.
 
Skywatcher adverts like to talk about "light gathering", so in like style :-
this will gather about 1/4 *of the light of your Explorer if it is the 130, or about 1/9th * the light of the Explorer 200.

Photographing galaxies is doable but will need very approx. 4x longer exposures (or equivalent more subs to stack) than an Explorer130. Visually it will not show you many more galaxies than your average binoculars, 50mm vs. this at 70mm. What it will do is show you what it can see with excellent clatrity, we hope (that is a tremendous simplification ! think of it as a HiFi 70mm glass)

Your eyepieces will work but you will need a 2" to 1.25" adapter and a star diagonal (or the other way round).

Perhaps  !  Me no expert, an expert should be here soon :)

Edit * 75% less and 90% less  light than

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Shera

Shera

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58 minutes ago, SilverAstro said:

I guess your DSLR T-ring/adapter? is 1.25" so you will need a 2" to 1.25" adapter, I think. ( I have not yet done anything yet in that line with my DSLR.) or a 2" T jobbie.
 
Skywatcher adverts like to talk about "light gathering", so in like style :-
this will gather about 1/4 *of the light of your Explorer if it is the 130, or about 1/9th * the light of the Explorer 200.

Photographing galaxies is doable but will need very approx. 4x longer exposures (or equivalent more subs to stack) than an Explorer130. Visually it will not show you many more galaxies than your average binoculars, 50mm vs. this at 70mm. What it will do is show you what it can see with excellent clatrity, we hope (that is a tremendous simplification ! think of it as a HiFi 70mm glass)

Your eyepieces will work but you will need a 2" to 1.25" adapter and a star diagonal (or the other way round).

Perhaps  !  Me no expert, an expert should be here soon :)

Edit * 75% less and 90% less  light than

Thanks for the record, it is the 130 Explorer I think but I only have an EQ2 mount for it and it's very heavy so I was looking for something that would sit on my Star Adventurer and is capable of getting more detail than the lenses that are supplied with my DSLR the biggest being 70-300mm. I have managed to get the Orion Nebula with decent detail (see attached photo of single exposure 139 secs on SA) but I want more detail and someone suggested this scope. 

Screen Shot 2018-02-18 at 19.41.02.png

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SilverAstro

SilverAstro

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9 minutes ago, Shera said:

 that would sit on my Star Adventurer and is capable of getting more detail than the lenses that are supplied with my DSLR the biggest being 70-300mm.

Ah yes ok, I see that I tried to cover too much all in one go, but as it had been a few hours 'hanging' I tried to cover various :)

So 'Dual-Speed 2” Crayford Focuser '  is the bit to take advice on to be able to use your 1.25" kit then. You wouldnt need the star diagonal for the camera but would need an equivalent extension I suppose.

 

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alexbb

alexbb

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Mine arrived too. First impressions are pretty good, it's very light, also the suitcase is very light. Focuser is smooth, doesn't seem to slip with the DSLR attached. On the cons side, it doesn't balance properly with the 550D and I dislike the locking screws, a 2" locking mechanism with compression rings would have been much nicer, perhaps not much more expensive.

And a quick picture of it, looks lovely, doesn't it? Currently I'm at work so I will inspect it later. And perhaps it's not going to see it's first light too soon as the forecast looks :(

Clear skies!

Alex

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Skyline

Skyline

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On ‎14‎/‎02‎/‎2018 at 14:44, FLO said:

Our entire first delivery has sold out!  We have another smaller delivery arriving tomorrow/Friday but they will probably sell out in the next day or two.  It will be difficult for us to forecast availability thereafter. 

If you have already ordered an Evostar 72ED you will receive one tomorrow or Friday and if you have chosen to collect one from our warehouse there will be one here reserved for you.  Promise :smile:

We have been assured there will be a lot more available when the next shipment arrives. 

HTH, 

Steve 

I forgot about this thread, and now I'm off to beg to the Missus and tell how much I love her :icon_mrgreen:

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