200P - colimation or poor optics

[Freff]

Hi Malcolm. I'm sure you're not in the mood to hear anymore on the subject, but I came across this

http://www.imagingdeepsky.com/Equipment.html and thought it may or not be relevant.

[malc-c]

OMG - that scope must be in excess of $100K - I think I would be a bit peeved having spent that amount of cash and had poor results... But it does go some way to confirm that you can get these strange additional spikes from errors in the optics rather than physical obstructions. This is why I'm not 100% sold on the theory that the issue with my scope is spider related, especially given the fact the replacement secondary I was sent from OVL resulted in poorer images than that produced by the original that came with the scope.

Having not used the scope for over two months I must admit it's dented my enthusiasm for the hobby. If OVL can't supply the replacement by end of January I might look at the costs of having the mirror set re-ground and re-coated and see if that resolves the issue once and for all, but with my current circumstances my redundancy reserves are running low and paying the mortgage is more important than having the scope in working order. I have had the offer from one kind SGL member who is fairly local of a loan of a refractor, which I may take up if my enthusiasm is re-kindled...

[tich]

I know how you feel Malc as I'm in the same boat as you as regards redundancy so major spends have been halted. The weather certainly isn't helping either as I haven't managed to get 200P out for about a month now. At least I managed to build the DIY dew controller as I've some spare time on my hands.

It's nice to know another member are willing to loan you their scope it just shows what a great community we are in. I had a member pop over to mine due to my guide camera troubles & thanks to them it's working although I still haven't had a chance to try it out yet.

Lets hope 2013 is a good one.

[malc-c]

Well having spoken to RVO it would appear that it will be approx mid February before I'll receive the PDS secondary as it's had to be made. I'm presuming that's down to production runs at the Synta factort, but it does seem strange that spares are not readily available, even from the manufacture. Would I be correct in thinking that three and a half months is rather a long time to wait for replacement parts ?

Guess I shouldn't complain as RVO and OVL are assisting me at no cost, so I should be thankful, but having a scope out of action for three months has been a bit of a downer !

[russ.will]

Well having spoken to RVO it would appear that it will be approx mid February before I'll receive the PDS secondary as it's had to be made. I'm presuming that's down to production runs at the Synta factort, but it does seem strange that spares are not readily available, even from the manufacture. Would I be correct in thinking that three and a half months is rather a long time to wait for replacement parts ?

Guess I shouldn't complain as RVO and OVL are assisting me at no cost, so I should be thankful, but having a scope out of action for three months has been a bit of a downer !

When I blew up the control board of my FlexTube Auto, I was quoted 2 months and it turned up in 6 weeks. No, OVL don't hold spare parts and basically, anything that's needed, comes in the next container for Synta. This can be subject to the vagries of how long UK customs take to process the shipment.

If funds were less of an issue, it is worth scouring Astroboot as S'n'S take most of the warranty returns, plus odds and sods off OVL. For instance, they had a load of 250px FlexTube OTAs, but no Dob bases. The Chinese got to point where nothing else would fit in the container, so the bases got left off the shipment. With little chance of them following, OVL off loaded the OTAs. Weird, but true!

Russell

[malc-c]

I received a phone call from RVO the other day, confirmed my address and in the last half an hour have taken delivery of a new PDS mirror and support

I'll be fitting it over the weekend and hopefully will have the thing professionally collimated by Es before I run some tests

Just like to thank Ian and Adam at RVO for all their help and assistance with this issue

[Black Knight]

That's good news. I really hope this is the last hurdle for you

[malc-c]

One thing that concerns me, which has been reported to RVO is that it looks like someone has used a black marking pen to draw a circle in the centre of the mirror - I've been assured that it won't affect the optical image, but I have my doubts. Thing is I can't send it back (and wait another 5 months), and have no idea how to remove it without damaging the coating of the mirror.

[nightvision]

That's crazy!!

[MadAlbert]

Guessing the grey is just a relection of something but does look like a piece of paper stuck over the top!

The circle will be out of focus but it's still very annoying!

[malc-c]

Guessing the grey is just a relection of something but does look like a piece of paper stuck over the top!

The circle will be out of focus but it's still very annoying!

That grey is the sky through the window reflecting on the mirror

[Freff]

Hi Malcolm

That mark is probably water soluble, I can't imagine that they would use an indelible marker that crudely.

[malc-c]

Thanks Tony, I may give it a clean later,.

Well the new mirror turned out to be a standard 200P and not a DPS version which peeved me off a little as that was the whole purpose of ordering one from Synta as the consensus was that it was the size of the secondary that was the issue. Anyway this along with a brand new spider and centre block was fitted and a good hour or so spent fine tuning the collimation. Tonight was clear enough to do some star tests and it was disappointing to find that the problem was still present, although the central star and halo was nice, round and even. I then placed a small fold of paper over each vein of the spider and found that when placed on one the additional spike became a lot fainter, almost disheartening. I've attached images showing the results and the orientation of the strip of paper to the camera.

I went on to try a small stack of subs of the leo triplet and they came out OK, but then there are few really bright stars in that area, Images of M45 or something like the Horsehead nebula which has a large bright star may be different.

So that's 3 secondary's and spiders, and full rotation of the primary, and still the problem appears,,,,, where's that hammer !!!!!!!!

[Chris]

Its mind boggling the problems you've had with this scope since flocking, it doesn't make any sense? Its also totally bonkers that you were sent the wrong mirror and with a weird circle drawn on it, Why?? I'm also baffled by why placing a piece of paper over one vane would stop the issue, I'm racking my brain for a reason?

I really hope your luck picks up soon:)

Chris

[Jason D]

… the whole purpose of ordering one from Synta as the consensus was that it was the size of the secondary that was the issue…. Tonight was clear enough to do some star tests and it was disappointing to find that the problem was still present… I then placed a small fold of paper over each vein of the spider and found that when placed on one the additional spike became a lot fainter, almost disheartening.

Malcolm, sorry to hear about your continued problems. As I indicated in my earlier posts in this thread, I never believed the secondary mirror was your problem. I still believe your issue relates to what I described in my last post in this thread (below). In that post I suggested you do the very experiment you did above and your findings support my theory. Do not cover only one spider vane; cover two opposite spider vanes as I described in my last post. In addition, look for localized protrusions as I described.

http://stargazerslou...40#entry1740804

Jason

[Chris]

Would blackening the sides and back of the secondary help, maybe the shiny sides of the secondary are reflecting light causing artifact? long shot I know but it wouldn't hurt.

[MadAlbert]

Just a suggestion (and sorry if this is already out there), perhaps it's worth meeting up with another person (or persons) on here local to you?

It may be that two (or more) heads would be better and would remove any disconnect/misunderstanding/translation errors in the process...

[malc-c]

What puzzles me is that I've stripped and replaced the spider so many times the odds of a twisted vein each time in the same place makes me question that as being the cause, especially as placing an obstruction in the path improves things ! Admitted this new mirror has a better finish that the last one, but there is still a straight edge on one side of the minor axis. If it was the PDS secondary I was promised it would of ruled out the theory of the uncoated sections being the cause. Thing is I'm not prepared to wait another 5 months for a PDS secondary to come from the far east.

Jason, I'll repeat the experiment the next clear night and will use two strips on opposing veins.

My only other thought was that the flocking has pulled the tube out of shape in some way, but I would of thought it wouldn't be enough to cause any obstruction in the light path.

I'll post up the results from the test session of the Leo triplet. It won't be pretty as there were no darks / lights etc - just the 8 subs. At least it will tell me if this issue is going to interfere with the faint fuzzys

[malc-c]

Here is the stack of 8 x 300s 800ISO subs - stacked in DSS - no tweaking.

I've also included a crop of two of the galaxies... with a bright star in the FOV

To be honest I can live with that. There is enough detail structure in the galaxies, and the additional spike is hardly visible.

[nightvision]

Such a long thread I haven't been able to find if you tried testing with a webcam instead of the DSLR.

Looking at your second test star I would say you have at least a path back to imaging (not a real fix but a get-it-working again lash-up); If you get vignetting you could re-fit the PDS mirror, install a piece of paper (maybe black paper) and get back imaging, then really understanding and addressing the problem will become secondary.

Edit: Just seen your galaxies, look fine!

[Aenima]

Malc, are you saying after all that you still have the extra spike on the stars?

Its still there on mine btw, not a clue as to what it is.

Hope you can get to the bottom of it while keeping your sanity!

All the best

Aenima

[Mr Fiery Jack]

I have to admire your tenacity, I would have sold it and bought a refractor or Mak by now if I was in your place.

[dark knight]

Malc, I feel your pain,, it's been a long slog for you and your tenacity is admirable, I've gone brain dead from just reading about your experience (no offence intended), so goodness knows how you're feeling. My only input would be to mark one vane with a bit of tape, and match that with one on the tube where they screw together, take test shot on bright star, remove the spider vane and rotate 90 degrees and reaffix in the tube, do some test shots, see if the extra spike moves around in your image. I know you will need to remove and then accurately put it back in and collimate between test, but reckon you're a master at this now. Sorry if this has already been suggested, but it would surely confirm the vane as culprit or not.

[bingevader]

I admire your perseverance!

I know nothing about AP, but the detail on those galaxies is splendid.

Cheers

[malc-c]

Malc, are you saying after all that you still have the extra spike on the stars?

Aenima

Yup, that's correct... but at least the mirror I've just received was better than the first replacement

I have to admire your tenacity, I would have sold it and bought a refractor or Mak by now if I was in your place.

Oh trust me I've thought about that many a time, but personal circumstances mean that replacing the ota is out of the question

My only input would be to mark one vane with a bit of tape, and match that with one on the tube where they screw together, take test shot on bright star, remove the spider vane and rotate 90 degrees and reaffix in the tube, do some test shots, see if the extra spike moves around in your image. I know you will need to remove and then accurately put it back in and collimate between test, but reckon you're a master at this now. Sorry if this has already been suggested, but it would surely confirm the vane as culprit or not.

Thanks for the suggestion but having fitted three different spiders the chances of all three having the same issue must be slim

I admire your perseverance!

I know nothing about AP, but the detail on those galaxies is splendid.

Cheers

Thanks, I must admit I'm quite happy with how the scope performed when there isn't a bright star in the fov