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Pompey Monkey

Collimating a William Optics Star 71

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I can see how the travel will be reduced. It only needs to travel around 5mm or less anyway to reach focus. M5? That seems quite big but OK you have them installed. I may have some already in the garage in my bike spares.

I tightened the retaining rings just until the rattle stopped. In fact the flattener one may even have a slight rattle. It is no where near how tight it was when glued. It did take some force to loosen both using the cone spanners but well worth it.

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11 minutes ago, ianaiken said:

I can see how the travel will be reduced. It only needs to travel around 5mm or less anyway to reach focus. M5? That seems quite big but OK you have them installed. I may have some already in the garage in my bike spares.

I tightened the retaining rings just until the rattle stopped. In fact the flattener one may even have a slight rattle. It is no where near how tight it was when glued. It did take some force to loosen both using the cone spanners but well worth it.

So just the retaining rings then? not the collimating screws?

I might just give this a go tonight (after vowing never to put it on my mount again! lol)

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4 minutes ago, Pompey Monkey said:

So just the retaining rings then? not the collimating screws?

I might just give this a go tonight (after vowing never to put it on my mount again! lol)

The nylon collimating screws look like they are for show more than anything else. I think I tried to turn them a bit but if I recall they didn't want to move, probably glued too. The main adjustment was loosening the retaining ring. Since I did both the flattener and the primary at the same time I cannot state for sure which one resolved the problem but I can say that both were on stupidly tight. Worth giving it a go I'm starting to have faith now in the scope and now I've fixed the backlash problem (by backlash compensatio) my stars are tighter than ever, if some what tilted still for now.

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48 minutes ago, ianaiken said:

I can see how the travel will be reduced. It only needs to travel around 5mm or less anyway to reach focus. M5? That seems quite big but OK you have them installed. I may have some already in the garage in my bike spares.

I tightened the retaining rings just until the rattle stopped. In fact the flattener one may even have a slight rattle. It is no where near how tight it was when glued. It did take some force to loosen both using the cone spanners but well worth it.

Forgot to say earlier but, FWIW, I initially bought M4 grub screws, only to find out that they were too small. I think the finder bracket screws are M4, which begs the question of what the supplied grub screws are for in the first place? I suspect that there was a bunch of castings with redundant holes in.... ;)

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Well I took it apart again - the retaining rings for both of the elements of the flattener were not over tightened at all. In fact the inner most forward element was actually a bit loose.

Anyways, I loosened all three rings a little and gently shook the scope before tightening the rings back up.

Interestingly, there did not appear to be any collimation screws for the forward element, suggesting that this is the datum in any collimation process. Also, from pointing the scope at the light fitting, it looks like it would be possible to achieve focus with the rear element out of the train completely, meaning that at least one variable could be eliminated from an alignment process. It still seems a bit too daunting for me to attempt!

Dang! I just can't put the blinking thing down! :mad:

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I've given in!

I now have a Esprit 80 ED pro triplet and appropriate flattener on order from our sponsors. It's great - now, instead of fretting about what move to make next in the search for "perfection", I am planning imaging projects and experiments again. Hurrah!!! :) 

As for the Star 71, it can now be found on a well known internet auction site, with full disclosure of course.

Thanks for everybody's help and suggestions :)

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Ha :-) that's interesting as last week that's the scope I was looking at but then realised that with the flatenner and the required spacing I would not fit all my kit in, plus I hate trying to get spacing right  (well at least until I got a Baader variable t adaptor). But I thought I'd keep going with the ts71 for now it's out if season now I'll have another go at collimating in August. Failing that it might turn into a plant pot or some kind of solar scope.

In hindsight I wish I had kept my GT81 Gold with flat 6A flatenner.

You will enjoy the 80. My friend has a 120 and his stars are lovely and round.

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12 minutes ago, ianaiken said:

Ha :-) that's interesting as last week that's the scope I was looking at but then realised that with the flatenner and the required spacing I would not fit all my kit in, plus I hate trying to get spacing right  (well at least until I got a Baader variable t adaptor). But I thought I'd keep going with the ts71 for now it's out if season now I'll have another go at collimating in August. Failing that it might turn into a plant pot or some kind of solar scope.

In hindsight I wish I had kept my GT81 Gold with flat 6A flatenner.

You will enjoy the 80. My friend has a 120 and his stars are lovely and round.

54.9 mm is within a gnat's whisker of the 55 mm required for the SW coma correcter that I was using with my 150 pds, so I'm already set up with the correct spacers to go! :)

Thanks for the warm feeling about the round stars on the 120 too - I was seriously considering the 100, but it's another half a grand over the 80, and it wouldn't actually be much different from my mothballed 105 pds. A new spider (with curved vanes), a s/h moonlite focuser and some flocking would bring the 150 pds very close in performance to the Esprit 100 for just a few hundred quid :)

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2 hours ago, ianaiken said:

 Failing that it might turn into a plant pot or some kind of solar scope.

 

All donations to my triple wide field rig are welcome :grin:

Dave

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2 hours ago, Pompey Monkey said:

54.9 mm is within a gnat's whisker of the 55 mm required for the SW coma correcter that I was using with my 150 pds, so I'm already set up with the correct spacers to go! :)

Thanks for the warm feeling about the round stars on the 120 too - I was seriously considering the 100, but it's another half a grand over the 80, and it wouldn't actually be much different from my mothballed 105 pds. A new spider (with curved vanes), a s/h moonlite focuser and some flocking would bring the 150 pds very close in performance to the Esprit 100 for just a few hundred quid :)

Oh so very close. Unfortunately I'm at around 59mm maybe even 60mm so too much. That's with Atik 460EXM,  Atik EFW2 and Atik OAG. If I went to finder guider then I could do it but means messing about when I switch the cam to the c9.25 which does need oag.

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On 24/04/2016 at 19:21, ianaiken said:

Oh so very close. Unfortunately I'm at around 59mm maybe even 60mm so too much. That's with Atik 460EXM,  Atik EFW2 and Atik OAG. If I went to finder guider then I could do it but means messing about when I switch the cam to the c9.25 which does need oag.

You can unscrew an 11 mm spacer from the flattener to give 66 mm distance to the chip; Page 8 here: https://ca.skywatcher.com/upfiles/en_download_caty01410467945.pdf

I'm just knocking up a Bahtinov mask from a shreddies packet ('cos FLO didn't have one in stock) for first light!!! :)

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6 minutes ago, Pompey Monkey said:

You can unscrew an 11 mm spacer from the flattener to give 66 mm distance to the chip; Page 8 here: https://ca.skywatcher.com/upfiles/en_download_caty01410467945.pdf

I'm just knocking up a Bahtinov mask from a shreddies packet ('cos FLO didn't have one in stock) for first light!!! :)

Oh no really? Then it would work...

Good luck with the first light I'd be interested to see the results. And good luck with the sale of the scope too!

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2 hours ago, ianaiken said:

Oh no really? Then it would work...

Good luck with the first light I'd be interested to see the results. And good luck with the sale of the scope too!

Thanks Ian.

Got out, got focussed - so far so good, then went to plate solve in preparation to find a good patch of sky with lots of stars for a test image... hmmm not working? Check the new focal length...check...?? I know - a reboot usually does the trick...reboot the remote PC then...nothing. nowt...nada - "Unable to establish connection with remote desktop - STAR-PC is not on the network".... Dead as the proverbial parrot.

How I laughed ;)

Tomorrow's always another day I suppose. lol.

 

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Hi Paul,

Oh no! I hope you've had some luck since then. I took the TS71 apart again and I've cured the backlash and I also noticed that the tilt adaptor was still not zeroed so I've set that too. The tilt adaptor comes on later models, obviously because they know the optics are maybe not quite right!

The Esprit still seems tempting.

 

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Just now, ianaiken said:

Hi Paul,

Oh no! I hope you've had some luck since then. I took the TS71 apart again and I've cured the backlash and I also noticed that the tilt adaptor was still not zeroed so I've set that too. The tilt adaptor comes on later models, obviously because they know the optics are maybe not quite right!

The Esprit still seems tempting.

 

Rapid response:

I'm just processing some subs I did last night of M13:

There is some star distortion in two corners that looks like the result of tilt somewhere - but it is still much much better than the WO :)

Also, the sheer number of square stars in the cluster, where I am under-sampling, is a very good indicator of the quality of the optics: I am imaging at about 2.7" pp, but I suspect the scope could work well at very close to its theoretical diffraction limit!

If the clouds don't clear too soon, I'll be posting my findings in the imaging discussion section tonight :)

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Paul,

Sounds great I will go take a look. I think I got somewhere last night with the scope but I need to test it. Hopefully I get to do that (unless I sell it lol).

 

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Hijacking the topic because I just join the second hand WO 71mm Star f/4.9 club :D My stars look ok - until they don't which means being on the brighter side. Did any of you guys have similar problems? I already talked to Steve Collingwood who said he doesnt collimate WO 71mm Star f/4.9 anymore: "I’m afraid I no longer work on Star 71 telescopes as they are not assembled in a way that allows me to properly align them and guarantee it will stay in. " 

FLO isnt of any help either because they only fix telescopes bought from them... and I don't have Ed Reids contact to at least ask him for opinion :) 

I am about to give up on this telescope. A few images:

This is Vega, 60s@ISO1250 with Canon EOS 50D:

unnamed.png

This is NGC7000 100x2min with Sony A7r:

Autosave-2.jpg

However images of dimmer stars with ASI174MM look okish:

file (1).jpg

file (2).jpg

 

file.jpg

Edited by sunka

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Have you asked FLO if they would pass on Es Reid's contact information so that you could speak to him yourself? Interesting that Steve says that he cannot work on the Star 71, but that Es can clearly sort them out as he does for FLO.

Have you tried a Google search for Es Reid? I can't think he'd be too hard to find? He clearly is the only guy who can fix these scopes.

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We like to help whenever we can but sunka lives abroad and the telescope isn't one of ours so there is little we can do. He asked us for Es' contact details but Es is extraordinarily busy so prefers us to keep his details private. Instead I refered sunka to SCTelescopes. 

HTH, 

Steve 

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15 minutes ago, FLO said:

We like to help whenever we can but sunka lives abroad and the telescope isn't one of ours so there is little we can do. He asked us for Es' contact details but Es is extraordinarily busy so prefers us to keep his details private. Instead I refered sunka to SCTelescopes. 

Gotcha..... I hope you didn't think I was suggesting that you should actually deal with it yourselves ...... that was certainly not my intention. I was just thinking about ways that Sunka could get the details he needed. :) I wonder if SCTelescopes would be able to help if Steve can't? Does Es have access to different 'machinery' or stuff than Steve if he can collimate and fix the Star 71 and Steve can't? Genuinely interested, hope you don't mind me asking :)

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25 minutes ago, FLO said:

We like to help whenever we can but sunka lives abroad and the telescope isn't one of ours so there is little we can do. He asked us for Es' contact details but Es is extraordinarily busy so prefers us to keep his details private. Instead I refered sunka to SCTelescopes. 

HTH, 

Steve 

FLO, thanks for referring me to scttelescopes! I used wrong wording so I apologize :) (writing "any help"). If you dont mind me asking - did you get a lot of WO 71mm to be repaired/replaced, because I found a few througout the forums :)

7 minutes ago, swag72 said:

Gotcha..... I hope you didn't think I was suggesting that you should actually deal with it yourselves ...... that was certainly not my intention. I was just thinking about ways that Sunka could get the details he needed. :) I wonder if SCTelescopes would be able to help if Steve can't? Does Es have access to different 'machinery' or stuff than Steve if he can collimate and fix the Star 71 and Steve can't? Genuinely interested, hope you don't mind me asking :)

Sara, Steve works for SCTelescopes so that was actually their response, now I realize I wasn't clear enough. I am curious about Es 'machinery' too! :)

Again, sorry for my english, it is not very good :) 

Edited by sunka

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2 hours ago, swag72 said:

Does Es have access to different 'machinery' or stuff than Steve if he can collimate and fix the Star 71 and Steve can't? Genuinely interested, hope you don't mind me asking :)

When it comes to leading questions, you are the best! :biggrin:

FLO has worked with ER and SC, both have done good work and both have well equipped workshops. I can understand why they might not want to work on a 5-element refractor purchased secondhand in Slovenia. 

2 hours ago, sunka said:

... did you get a lot of WO 71mm to be repaired/replaced, because I found a few througout the forums :)

Yes, but that is understandable. Doublets are relatively bomb-proof, triplets are more challenging and four and five-element refractors even more so. For this reason all our William Optics GT81, GT102 & Star-71 are now checked on ER's bench before dispatch. We began doing this only two months ago but it is already working well. So far only one Star-71 has been returned for re-alignment, though I expect we'll see one or two more after the first cold winter night. 

FWIW I wouldn't buy a secondhand 5-element refractor, regardless of the brand, unless I knew it's history and it's owner well. The same applies to triplets, though less so. 

HTH, 

Steve 

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