200P - colimation or poor optics

[mdstuart]

Are the circles the same both sides of focus on a star?

You may have astigmatism in your system?

Mark

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[mdstuart]

Sorry did not see later posts..I see you have cracked it.

Mark

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[malc-c]

thanks for the comments guys.

Mark, I hope to do some further tests including unfocussed stars next session, but looking at that image I'm confident that colimation is good and the rings will be circular

[Teslar]

Great news I'm so glad you finally got to the bottom of this you deserve a medal for your patience and all the energy and time you've put into this. Congratulation

[Aenima]

Yeah, really good to see the right number of diffraction spikes Malc, and you can now continue observing and imaging again with none of the messing about with collimation or spidervanes etc.

Great news.

Regards

Aenima

[malc-c]

well I think I can put this one to bed - I've attached a screen dump whilst capturing M27 - 180 second sub @800ISO no processing

On the screen the background is a lot more even and the bright star at the bottom is nice and round with just 4 refraction spikes

Shame I've not received a responce from the retaler or importer to the e-mail I sent them the other week.

To anyone else who has the same issue with their explorer 200P I would seriously recommend purchasing a 58mm secondary from Orion Optics. It's certainly given my 200P the performance I was expecting. If your scope is still in warranty then push for the cost of a replacement mirror to be paid for by the importer / retailer. I can't comment on how a PDS mirror would perform as it too may suffer from the same flat uncoated areas like that of the stock 200P mirrors seem to.

[Timbo32]

WoW What a read!! I didn't really understand collimation before reading this post but now!!

I am currently reading Wonders of the Universe by Prof Brian Cox and Andrew Cohen and couldnt help notice

the picture on page 13, the stars made me think of reading this post!

Glad that you have resolved the issue, shame you had to go the long way around so publicly!!! not that you have suffered any embarrasment malc-c,

can't say the same of the supplyer/manufacter!! would have cost them peanuts! Now there penny pinching may have cost themselves future sales!!

Clear Skies Tim

[Jason D]

can't say the same of the supplyer/manufacter!! would have cost them peanuts! Now there penny pinching may have cost themselves future sales!!

Since Malcolm resolved the issue with the original mirror -- even if the resolution lasted for a relatively short time -- it would be unfair to blame the original mirror or the manufacturer.

Jason

[malc-c]

Since Malcolm resolved the issue with the original mirror -- even if the resolution lasted for a relatively short time -- it would be unfair to blame the original mirror or the manufacturer.

Jason

I still can't explain why when I thought it was resolved using a stock 200P secondary, the problem reoccurred the next time I used the scope when nothing had been changed between sessions as the scope is parked in an observatory. The only similarity I had with all mirrors from Skywatcher was that all had one or more flat edges on the minor axis, with mirrors having two flats producing two spikes, and that the problem has finally been resolved by using a slightly over sized mirror, which is perfectly elliptical in profile, from a 3rd party manufacture. The consensus between the members of our societies imaging group, some of which are well qualified in optic design, and have shown an documented the theory behind the effect are in full agreement that the "fault" on these SW secondary's is due to the way they are supported during the coating process, which leaves one or more uncoated straight edges on the minor axis. Ergo I think its only fair to document the experience here and lay the blame squarely at Synta feet. IMO their quality control is poor if they are letting non-elliptical secondary's be used in their scopes.

It also seems that at least three other users have now noticed similar issues with their explorer 200P's, which would suggest that this was never an individual problem with just my scope. How wide spread the issue is, or if it's something those users simply put up with rather than resolve I can't say, but must be such that Synta are not bothered by this issue even if those people did complain. The issue I have is with English trading laws, which mean my "contract" is with the retailer, and I have no direct recourse with the importer or the manufacture. The retailer is caught in the middle, and naturally their relationship with the importer means that they could be out of pocket if they haven't got any mans of redress with the importer. Having proved that the scope has had this issue when it was still warrantied, but not to the same degree, which was more likely down to the learning curve I went through with both collimation and imaging making the defect stand out more, which by this time the scope was just out of warranty. The retailer has tried very hard to resolve this through the importer by obtaining various replacement mirrors from the manufacture, all of which failed to resolve the issue, but that is as far as it goes. The request for the cost of the 3rd party mirror to be payable through this chain fell on deaf ears, namely as the manufacture would not back up the importer, who in turn felt they could not back up the retailer. IMO the buck stops with the manufacture and not the retailer, whom (up to now) I've had excellent service from. The result may well of been resolved quicker if I had used a different retailer, as has been commented on in this thread, who knows, as there is only a sole importer, maybe any SW retailer would be in the same position.

However, I'm not pursuing any claim for compensation, and have put the purchase down to an "upgrade" of my 200P's optics which has really proved to be worth while. At the start of this thread I had no idea it would run so long or have such ramifications, but the issue has left me feeling somewhat let down because rather than look on the positive side and take on board the findings here, and thus improve the quality control or increase the secondary size so as not to be so close on the tolerances, they ( and I mean all parties in the supply chain) appear to of erred on the negative aspect and looked on me as an complainant and ignored the findings altogether.

Bottom line is that a year after discovering this issue the problem has been (finally) resolved for good and I am now enjoying the results I'm getting from the scope. This issue hasn't put me off purchasing SW equipment, as generally they provide good value for money.

I'm going to request this thread is now locked as I don't feel there is anything else to discuss regarding the issues I've had and have detailed here. I think it's now time to move on and put this issue behind me.

[MikeP]

I'm going to request this thread is now locked as I don't feel there is anything else to discuss regarding the issues I've had and have detailed here. I think it's now time to move on and put this issue behind me.

Locked per original poster's request.

Mike