Focus and Diffraction Spikes

[AlistairW]

FLO have been brilliant and are helping me to understand where the issue lies. We are just taking a step at a time to eliminate possible issues one by one, which is the sensible thing to do. Their support is second to none, and I look forward to coming to a resolution :-) - but I also greatly appreciate all the help and suggestions I get here on Stargazers, all of which is helping me learn more each day. Thanks everyone. 

[salas]

Hi Alistair, it looks like I'm having the same issue with the same scope, I posted about it last night and was helpfully directed to this thread, see link to my post with star photo.

http://stargazerslounge.com/topic/256149-star-shape-query/

Your diffraction spikes seem more evenly distributed than mine. I would be very interested if you arrive at a conclusion on the cause of what's being seen. If you want any comparison work doing let me know. I have seen the effect using the WO reducer or a straight through 1.25" camera adapter.

Thanks,

Steve

[Alien 13]

Just a thought have you tried shining a UV light down the tube it can sometimes detect shiny surfaces that might cause the effect you are seeing. I had a couple of screws in my WO71 that I re painted.

Alan

PS if you have no UV source a blue LED will often work.

[Galaxyfaraway]

I have the same issue and the stars look exactly the same as yours. What is the usual policy when it comes to returns? I have had mine for a few weeks and there might be minor marks on it (from to mounting/taking off).

[D4N]

I have the same issue and the stars look exactly the same as yours. What is the usual policy when it comes to returns? I have had mine for a few weeks and there might be minor marks on it (from to mounting/taking off).

Assuming you are in the EU you will have a two year warranty as a minimum.

Your right to withdraw under the consumer rights directive ends after 14 days however so the supplier is not legally bound to offer you a full refund but some suppliers may do so out of good will.

/Dan

Sent from my iPad using Tapatalk

[Galaxyfaraway]

Btw I found this thread: http://www.cloudynights.com/topic/491910-william-optics-star-71-first-light/

and a reply from William Optics:

Subject: Re: WO Star71  Hi,  Its absolutely normal for the  design, those spikes are from the lens cells (the 4 soft  plastic tips from adjustment screw is creating the spikes) ,  all Wostar 71 are the same, it's not the pitched  optics.If  pitched optics stars will be triangle shape, it's easy  to see from high power 4~5mm eyepiece.  Some people like the unique  spikes and some people don't  likes.  Thank you.
Best Regards,
 
William Yang William Optics USA

Perhaps it is normal?? I know it's the WOstar 71 but the pics of stars look the same. If it's correctable with software, I might be able to live with it (just).

[FLO]

I have the same issue and the stars look exactly the same as yours. What is the usual policy when it comes to returns? I have had mine for a few weeks and there might be minor marks on it (from to mounting/taking off).

It depends on your supplier, is it one of ours? 

Steve 

[Galaxyfaraway]

No, but I now wish it was! I emailed WO and my supplier to check: if the issue is typical to a scope in this price range then perhaps I need to adjust expectations (for not owning a Tak)..I wouldn't want to return it unless necessary and a clear fault.

[AlistairW]

FLO are providing me with first class assistance with my situation. No further updates at the moment.

[ollypenrice]

Have you tried turning the camera to see if the spikes follow it? If they do then it isn't the scope. Micro lensing or other chip effects might be at play.

My own observations of this effect in some WO scopes certainly doesn't trace back to one article. I've been sent quite a few examples for comment over the years. However, it is perfectly true that other manufacturers manage to leave a 'signature' effect on stars as well. Takahashi are amongst the most consistent in this. I've discussed their 'inverse light house beams' on here several times. This effect may arise from pinching but it is very common in Taks. It doesn't bug me but it clearly is an issue for some owners and I don't judge them for that. It upsets you or it doesn't, just like Newtonian spikes etc.

Olly

[Galaxyfaraway]

@Alistair: are you shipping the telescope back for testing or what's the plan? Not certain what to do with mine but would be interested to hear what you are doing.

[FLO]

I can answer that one  

We have offered to either send Alistair a new GT81 or send his existing scope to SCTelescopes for testing/adjustment. He chose the latter. We suspect the spikes are caused by the lens cell's collimation screws so it might be possible to adjust them out. We'll know later this month. 

HTH, 

Steve 

[Galaxyfaraway]

Great, please let me know. I will try testing it as per Olly's suggestion to rule out DSLR causing it. (although I will be getting a CCD so useful to compare). Just need one star in front of the cloud! (among trillions behind them)

I emailed William Optics: they seem to be answering from Taiwan and asked me if I wanted to ship it to them for testing. Who bears the shipping costs usually? Also the customs & duty import will surely go nuts.

[FLO]

I emailed William Optics: they seem to be answering from Taiwan and asked me if I wanted to ship it to them for testing. Who bears the shipping costs usually? Also the customs & duty import will surely go nuts.

That is something you need to discuss with your supplier. 

Steve

[Galaxyfaraway]

Ok, what is your policy in a case like this with regards to shipping costs & customs? Would be good to know for the future.

Seems a bit ott that it needs to go all the way to Taiwan for testing...I would have thought WO have UK premises.

[FLO]

Ok, what is your policy in a case like this with regards to shipping costs & customs? Would be good to know for the future.

We cover the costs associated with warranty repairs. We always have 

You really should discuss this with your supplier, not us or WO. Give your supplier an opportunity to look after you. 

Steve

[Galaxyfaraway]

Just trying to make sure it's not my own stupidity (pretty sure it is).

I performed an obgyn-type examination of the objective of the GT81 and can't see anything (no screws that hold the lens elements etc. Where are they supposed to be?). The only 2 screws I can see inside are the ones from the top (where the holding bar/rings are normally situated which I took off but put the screws back in). See pics: I loosened them for the 1st pic but tightened them for the second. ). Could those be it???!!!

(Really don't want to part with my scope). When I assemble the bar with the screws I can't seem them inside the objective anymore.

Unfortunately can't test it on stars: there aren't any.

[FLO]

We have offered to either send Alistair a new GT81 or send his existing scope to SCTelescopes for testing/adjustment. He chose the latter. We suspect the spikes are caused by the lens cell's collimation screws so it might be possible to adjust them out. We'll know later this month. 

We have Steve Collingwood's report. Apparently the manufacturer has switched to using six adjustment screws for each element (they used to use three). This change is not unique to WO, most Chinese manufacturers have done the same. No doubt it reduces the number of issues caused by impact during transit but it might also have increased the likelihood of one intruding into the light path. Regarding AlistairW's telescope he says "this one’s not terrible at all, but something is clearly amiss and it hasn’t been constructed in a way that makes adjustment very practical". 

With this in mind we have offered to replace the telescope.

HTH, 

Steve  

[FLO]

@Galaxyfaraway, you would need to remove the lens cell to see the screws but I strongly advise you not to.

Please contact your supplier, if he isn't being helpful or responsive then contact William Optics. 

[HenryNZ]

@Galaxyfaraway, you would need to remove the lens cell to see the screws but I strongly advise you not to.

Please contact your supplier, if he isn't being helpful or responsive then contact William Optics.

I have invested interest in this topic as I have the same problem with my GT81. I bought mine while I was in the states from Optcorp. Warranty claim necessitates sending the whole ota back from New Zealand, not a cost effective option. So I ended up dealing with William at WO directly. I sent back the lens cell and tried a replacement lens cell, and it has it too but to a different degree and pattern of diffraction.

At the end it becomes uneconomical for me to keep sending the lens cell back, so I made William hand pick the best lens cell in exchange for dropping the matter. Unfortunately the hand pick lens cell still shows the same problem and I have no more recourse.

Anyway I do have a spare lens cell and I am tempted to try the adjustment myself.

[salas]

So it seems as I bought this scope 2nd hand (under a year old) I have limited options to try solve the issue a few people seem to be having. I've had it on expert advice that the artefact being seen is not actually that bad and I would have to agree - except I'm a bit of a perfectionist.

I disassembled the scope for a closer look (its not like I'm going to void a warranty claim). I swapped the main body round so the lens cell is now screwed on to the focuser end of the body and visa versa. Interesting results. I've attached a before and after image of Vega. Now it has to be noted I had a pretty cloudy sky on and off and I think the baffles in the main body of the scope could now be acting as an aperture mask because I swapped it around. The artefact of the star being cut in to is gone but I've now introduced a halo around the star.

Conclusion at the moment is inconclusive! I will have another go when it's not blowing a gale and cloud free.

[D4N]

Interesting, I would guess that not having baffles where they are supposed to be has introduced internal reflections that cause the halo.

What you say about the baffles acting as an internal aperture mask makes sense too.

/Dan

Sent from my iPad using Tapatalk

[Alien 13]

Makes you wonder if the artifacts are light scatter within the tube and if baffles etc have moved or the wrong paint. It would also be nice to know if WO check the lens cell on a rig or the whole scope with returned units.

Alan

[salas]

In the photo galaxyfaraway posted above it shows the arrangement and design of the baffles. I can't help but think the design pattern of these has something to do with it.

[salas]

One other observation I made when I took it to bits was that there were more threads at the lens end of the main body than the end the focuser screws onto. From a design point of view surely the end supporting most load (the focuser) would have had the most threads?