Orion Optics 14 inch Dobsonian mirror issue....

[Astro_Nic]

Hi everyone

Hopefully you can offer your advice.  I have finally taken delivery of my 14" Orion Optics (UK) dob.  Looks great and I got the 1/10PV mirror and zygo report.  However, I have a couple of issues with the primary mirror that I was hoping you could advise on:

• There are two jet black spots on the mirror - one a few mm in diameter - please see pic.  This is clearly visible looking down the tube - I can't get close to the mirror to determine what it is and am reluctant to start dismantling anything as am a complete telescope novice.  I've tried using a hairdryer down the tube incase it's something that will come off - it doesn't move;
• When a torch is shone down, the mirror has small dots and dashes on the surface - nothing significant, just very faint - I assumed it would be absolutely crystal clear.

I have gone back to OO and they have said that the mirror has passed all QC and that there are no problems and the mirror is significantly better quality than I would get elsewhere.  I do not doubt this, but there are two black spots on the mirror!  This can't be right can it?  I assume the dots/dashes are not scratches but related to the coating process in someway and I am less bothered about that.  But the black spots?  Many thanks for any advice you can give.

The zygo report shows Strehl of 0.992 and 1/10 PV and very low astigmatism.

Nic

[rl]

Nic

I've got the same scope (bought secondhand). The mirror on mine is pretty much perfect after a clean..i.e once a year. The rest of the time there is always some small quantity of dust/ specks seems to accumulate. 

They might be paint flecks that have come off the inside of the tube. It's very annoying on a brand new scope, but practically speaking, the area involved is so tiny it's not going to have any visible effect. I think I'd try out the scope first and make sure everything else is ok in case there is some other reason to return it. Shining a light down the tube shows up every minor defect in the worst possible way. 

Best option: It looks like you live close enough to take the scope back and let them have a proper look (assuming you have a car), rather than clean it yourself. Otherwise you can drop out the cell / mirror by removing the 6 bolts at the bottom. It's heavy, be careful! But I'd get the ok from OO first regarding the guarantee...... 

If you do take it out it's worth noting which of the 3 possible orientations is the correct one for reassembly. And there are 2 options for the height of the cell in the tube...

 

[dweller25]

A slightly strange response from OO as you were talking about blemishes not the mirror’s optical quality !

My 8” OO mirror turned up blemish free - as did my 10” mirror from Skywatcher - I would expect yours to be the same.

It could be a loose paint fleck from the inside of the tube that’s fallen on the mirror ?

It is fairly easy to take the mirror out for cleaning - which you will have to do one day.

It probably has no effect on performance but it would bug me.

[Martyn A E]

Perhaps if you have access to an air compressor or even a keyboard air cleaner spray can you could see it moves when a jet of air is pointed at the specs.

 

[NGC 1502]

Of course if your scope is brand new it should be pristine. Having said that those spots will not be visible at the eyepiece or affect the view.  If it were mine however it would annoy me.

Best guess is the spots are some sort of debris. Blowing a hair dryer down the tube doesn’t concentrate on a specific area.  If it were me I’d remove the primary and cell and using a contact free method (large rubber bulb blower) see if they come off.  The construction is simple, you only need basic DIY tools and skill level.  You will need to collimate.

[dweller25]

36 minutes ago, Martyn A E said:

Perhaps if you have access to an air compressor or even a keyboard air cleaner spray can you could see it moves when a jet of air is pointed at the specs.

 

Perhaps the air compressor could cause more problems than it solves ?

Edited February 23, 2022 by dweller25

[Astro_Nic]

Many thanks for your advice.  I've agreed with OO that I will use it for a few months and see if it is noticeable in real life and then I can pop in with it next time I am passing and they will take a look just to confirm nothing is wrong.  I certainly don't want to take it apart or try to blow air on the mirror!  But I am the sort of person who will think about that spot everytime I get the scope out!

On another point - the 12v DC fan at the bottom comes with two crocodile clips!  What on earth do I attach those to?  Or is there an alternative cable I can buy to plug into a 12v power supply?  Thanks

Am looking forward to first light with my first ever telescope!

[Whistlin Bob]

That's a mighty telescope to be starting with! I'm sure it will perform fantastically with or without those spots.

I noticed that you're in Burton. There's an Astronomy Group at Rosliston Forestry Centre- we have a mid month meeting which is all about practical astronomy, and especially helping people get kicked off with astronomy. If you bring your scope along we'd be more than happy to have a look at it and let you know if we think OO are being fair in their response, and also help you get started with it.

You can find out more details here https://www.roslistonastronomy.org.uk/

[Astro_Nic]

2 hours ago, Whistlin Bob said:

That's a mighty telescope to be starting with! I'm sure it will perform fantastically with or without those spots.

I noticed that you're in Burton. There's an Astronomy Group at Rosliston Forestry Centre- we have a mid month meeting which is all about practical astronomy, and especially helping people get kicked off with astronomy. If you bring your scope along we'd be more than happy to have a look at it and let you know if we think OO are being fair in their response, and also help you get started with it.

You can find out more details here https://www.roslistonastronomy.org.uk/

Hi, thanks for your reply.  Yes, I definitely need to join! I know nothing about how to use this beast!  I’d love some help.  All I know is that it’s a lot heavier than I was expecting! Lol

i still need to work out how to power the fan with crocodile clips! 
 

thanks

 

nic

[Second Time Around]

Just clip them onto a 12 volt battery.  I use Yuasa ones, either the hand size 7Ah ones that fit burglar alarms or for my short sessions the tiny 1.2 Ah size. Either fit on the rocker box of my 8 and 10 inch OOUK Dobs.

I suggest you buy 2 so that you always have a spare.  I've got 3 of the 1.2Ah size and 1 of the 7Ah size. (I've just given 4 of the latter to a fellow club member).  I rotate them, keeping 1 permanently on charge and use this one the next session.

 

[Whistlin Bob]

13 hours ago, Astro_Nic said:

Hi, thanks for your reply.  Yes, I definitely need to join! I know nothing about how to use this beast!  I’d love some help.  All I know is that it’s a lot heavier than I was expecting! Lol

Yeah- they're pretty big aren't they! You'd be very welcome- if people are interested in joining we let them have a few free meetings to make sure it works for them.

[Astro_Nic]

OK, so no idea how to collimate! What’s the best guide? I have a cap and a Cheshire eyepiece.

 

so the black spot is clearly seen through the cap - not surprising as still just looking at the mirror? Or more worrying?

 

secondly, I attach a back view of the mirror - every guide I’ve seen shows lock screws on the mirror - mine has none, even though there are clear instructions to only finger tighten - finger tighten what? Please see image.  Is this normal for OO or do I have an issue?

 

many thanks as always!

Nic

[Starflyer]

The black thumbscrews are for collimating, the threaded studs next to them is for locking.

My brother had a similar experience to you, a brand new reflector arrived with a screw loose in the tube that had obviously scratched the mirror in transport.  It took a few emails / phone calls to get OO to agree it wasn't right and to take it back, when it was delivered again, took a few weeks, they said they'd found no problems even though it was clear they'd either swapped the mirror or recoated it.

My £0.02, get them to fix it, I'm sure you paid a lot for your new scope, if it isn't right keep insisting they fix it.

[Spile]

On 25/02/2022 at 20:55, Astro_Nic said:

OK, so no idea how to collimate! What’s the best guide? I have a cap and a Cheshire eyepiece.

 

 

 

Do give my guide a try and see how you get on https://astro.catshill.com/collimation-guide/

[jetstream]

On 23/02/2022 at 06:15, Astro_Nic said:

But the black spots?

Take a flashlight and shine it on the mirror from the back in the dark and see if any light is visible through the mirror as seen from the front ( coated side).

[Richard W]

Hello

I have a OOUK 10" and funny you should say that I have 2 small black specks when it arrive in November last year and after last nights session I just checked and I have 6!  So I'm guessing the posts are correct and it is from the matt pain on the inside!  It is annoying and I'm afraid to take out the primary and use 'air' to blow it clean.  Guess it needs to be done at some point.  When I climate (I use a the deluxe Cheshire from Flo plus I'm paranoid about the Secondary so I use the Concenter and for me it helped the paranoia and it was a 'Ureka' moment when I understood what I was looking at from the great instructions given to me through this site) I use paper to block of the primary and I know I'm prushing the inside of the tube and that is dislodging very small loose paint!  The Concenter was expensive but really worked by the way.

I'm also new into astronomy and last night was great (after spending Saturday afternoon for nearly an hour collimating) so I'm not seeing issues ..... ACTUALLY the real issue is at my age is I have a floater in the eye and looking at the Trapezium in the Orion nebular (I think that's correct??) on high power it did flick across my field of view and this is the first time I noticed it!!

Power Pack for fan I got from Flo (honestly I'm not promoting them deliberately, I just have had great advice) a Celestron Powertank Lithium LT plus I got a pack of male and female connectors from Amazon from a suggestion from Flo support and I cut the crocodile clips off and connected the correct polarities on the male plug and 12v supply works perfect!  I was just nervous of using open terminal clips as I have a 6 year old with interest and I could see her touching thinks or knocking them very easily.  

To be honest it can be a little daunting att first but my local group Astronomy group chairman came to my house to collimating initially as I was in a panic - so great people out there to help on the journey!

Cheers Richard

[dweller25]

1 hour ago, Richard W said:

Power Pack for fan I got from Flo (honestly I'm not promoting them deliberately, I just have had great advice) a Celestron Powertank Lithium LT plus I got a pack of male and female connectors from Amazon from a suggestion from Flo support and I cut the crocodile clips off and connected the correct polarities on the male plug and 12v supply works perfect!

Can you share a link for those Amazon connectors please ? 🙂

[scarp15]

Congrats on a lovely scope. Agree with rl and other related comments, as this will almost certainly be dislodged flaky black paint specs and ought be removable when you take out the mirror, which would not be advisable immediately or perhaps necessary in terms of observing. It is unfortunate that this has occurred, but don't become undaunted by this and take time familiarising with this scope, its characteristics and gaining an understanding to the collimation procedure, which is fairly quick to gain an informed rudimental understanding. There are plenty of good Newtonian collimation guides available, to get started.  

In terms of 12V battery, when I first began using my VX14 Dob, I took along a 12V 7AH battery. The former user of mine, had replaced the clips with a jack plug therefore I additionally used a transformer lead and inverter. However as I mostly transport it to infrequent dark sky trips, this soon was deemed a faff and I never even bother taking it. I also have a VX8L dob purchased new with the crocodile leads and bedsides testing to ensure that the fan worked, have never used it.

When (not if) you do get to remove the mirror, firstly there is no need to undertake this procedure for sometime, second just be organised, have the time and room set up. Take time over each stage and as mentioned, mark an alignment for a mirror cell bolt hole; I use masking tape as a matching marker on one tube hole and mirror cell bolt thread.  When the mirror cell has been removed, an air blower ought extract the specks, if not use a soft sable haired artists brush. I have periodically removed each mirror. The VX8L when still new as I became irritated by a hair that had lodged on the mirror, then later by a speck that could had been pollen, so have to be guarded about that to. Just something to get use to but very occasional. 

Look forward to hearing of your reports.

Edited February 27, 2022 by scarp15

[faulksy]

wow, what a first scope to buy. i had one hence buying a 20" orion mirror brilliant scope. as said above just remove the mirror cell with the mirror and use a blower. this would annoy me as well.

look foward to your first light report

[Astro_Nic]

Panicking about collimation now.  Really have zero idea what I'm doing!  Last night I centred the secondary adjusting the spider vanes.  But then I'm a bit lost.  I have a collimation cap and looking through it and things seem ok - or rather I can understand what I'm looking at, but I have the red cheshire/sight tube from FLO - and this shows a completely different view - the cross hairs are no where near where they should be - but it wobbles so much in the focuser that it flies around depending where you bend it - the OO has a plastic 1.25" adapter - I've just ordered a Baader 2" to 1.25" clicklock adapter to help with this.  But still no idea what I am supposed to do!

I will read the guide posted above.  If anyone else has any advice, that would help as well.  Or any local people would be most welcome to visit and assist! lol

Many thanks everyone!  Clear skies!

[Astro_Nic]

On 26/02/2022 at 22:41, Spile said:

Do give my guide a try and see how you get on https://astro.catshill.com/collimation-guide/

Thanks for the guide….I attach my views - firstly through a collimation cap and second one through the site tube/Cheshire.

what on earth does it all mean?! Please go easy on me! Lol

thanks! 

[Spile]

The camera view may not be agreeing with you are seeing with your eyes due to parallax errors. Cap view looks fine but the Cheshire view does not. Therefore trust your eyes using the Sight tube. The cross hairs of the sight tube should intersect with the bright ring of the Cheshire. Does it?

If you followed the guide you will have placed a coloured piece of card behind the secondary mirror.

This is what you are aiming for…

[Astro_Nic]

The photos accurately reflect what I was seeing with my eyes.  The two views are very different.  Assuming the Cheshire/sight tube is correct, where do I start?! 

[Astro_Nic]

The photos accurately reflect what I was seeing with my eyes.  The two views are very different.  Assuming the Cheshire/sight tube is correct, where do I start?! 
 

why are they so different? Maybe the issue is the plastic 2” to 1.25” adapter and I should wait for the baader to turn up.  

[ollypenrice]

For the bad news, Google Orion Optics UK customer service.

For the good news, look through the scope, not at it.  Such blemishes will have no effect on the view whatever.  If the figure of the mirror is as they say then the views will be excellent.

Olly