Flocking a 6SE

[Cath]

Has anyone ever taken one apart and done it I wonder?

Is their room along the inside of the tube being as the primary moves up and down the tube?

The reason I'd like to is because I get problems with what looks like internal reflections if their is a brightish star just out of the fov - they cause a large halo type ring to appear across images - centered on the edge of an image.

[knobby]

now that is a good question, can imagine it being a big task though !

[seiko]

A number of people have but I doubt you'll see much of an improvement. Are you sure it's caused by the insides of the OTA? I think e baffles more than restrict from stray light. I assume you are using a dew shield? Have you noticed these internal reflections when using all eyepieces etc?

Personally, I wouldn't bother but some people do and say it helps. To what extent though is very subjective.

[Cath]

It's when I'm imaging the effect occurs, no barlow, just camera directly on back of scope.

I'll save an image next time and show what I mean, I normally just delete the images so haven't got one to show at the moment. It really messes up the images.

[username]

Hi Cath,

There's been some discussion about this over the pond. It appears the baffle is the main culprit. There was a more recent thread but I can't find it, here's an older one. Will try and find the more recent one

http://www.cloudynights.com/ubbthreads/showflat.php/Cat/0/Number/2563881/page/291/view/collapsed/sb/5/o/all/fpart/all/vc/1

[Cath]

Thank you username. It sounds like a shiny surface problem in the baffle area then. I shall definitly take the front apart then when I can and flock the baffle. It can't hurt to do it so it'll be done.

[username]

I'm sure you would do all the relevant research before taking it apart but make sure you mark the orientation of your corrector plate, they're unique for each scope and are orientated for optimum correction.

Check out the 'even teddy wept' threadin astro lounge too

[Peter Drew]

Cath. Bear in mind the usual caveats about ensuring that you mark the orientation of the corrector plate for re-assembling after flocking.

[Peter Drew]

Cath. Bear in mind the usual caveats about ensuring that you mark the orientation of the corrector plate for re-assembling after flocking.

[Cath]

Yep thanks guys, marking it all was the first thing on mind to do.

This looks useful for dismantling the celestron sct's ...

http://www.astromart.com/articles/article.asp?article_id=594

When I do mine (very soon) I'll photograph it all as I go and post it all here for anyone else who might be wanting to do the same.

[Peter Drew]

An interesting read. The early orange tubed 8" Celestrons which I dismantled for various reasons when I was "in the trade" did not need to have the front cell removed to extract the primary mirror. There were two internal slots at 180 degrees that gave clearance when the mirror was turned sideways whilst withdrawing it. As mentioned in the article, the corrector plate is often firmly stuck, we found that if you slacken the srews to part release the retaining ring then a couple of slaps on the side of the tube always safely did the trick. The commonest reason for removing the corrector plate was the eventual need to clean the misting build up on the internal face caused by the egassing of the internal paint solvent.

[Cath]

Hi Peter

Interesting, thanks!

The whole tube (corrector plate, primary mirror) all still seem very clean at the moment, although I've only had it for 15 months, but this halo problem has to be fixed, it's messing up the images I try to take when their is a bright star just out of view.

I've just ordered some of this ..

http://www.wilko.com/dc-fix-fablon/d-c-fix-original-deco-self-adhesive-film-velour-black-348-0005/invt/0309578?VBMST=velour

They say it's the same stuff FLO sell so should be OK (I presume). I thought about doing it the easy way and using black board paint, but flocking should be a lot better than paint I guess.

But I'll just strip the tube down in the next couple of days when I have time and just have a look at all the surfaces and take some photos first before deciding what exactly to do. I have a couple of permanent markers so I'll use them rather than tape to mark the orientation of the corrector plate etc.

It's good to know all the in's and out's of your own equipment I think anyway, so will be educational for me.

[billhinge]

I did my C11 when it got damp inside and I decided to clean it out

It isn't hard, just remember to put it back how you found it and you may need to collimate it afterwards (you probably will)

I used the protostar flockboard from lyra optic since it isn't sticky http://www.lyraoptic.co.uk/Telescopes-Accessories.html (near bottom of page)

I don't use the C11 as much now but I did notice glare from the moon prior to flocking when it was just outside view even with a big astrozap dewshield but not after flocking. Not as dramatic with stars so could be wishful thinking

protostar is not sticky so it doesn't stick to everything, its great on a C11 but on an 80mm scopes 3" focuser it is too stiff to conform to the curve of the tube properly so you 6" is somewhere in between

[Cath]

Thank you Bill.

Did you flock the whole tube I wonder?

[billhinge]

Hi Cath

I did from the corrector plate down to just past the mirror, I could have done the inside of the focuser baffle but didn't

Obvious tip, when putting the corrector plate back on, try doing it with the tube pointing to the ceiling with the mirror at the bottom, it makes getting the cardboard spacers lined up easier

[Cath]

All tips are welcomed!

Standing the tube upright with the corrector end up isn't so easy (while keeping both hands free), I'll see what I can do.

[JamesF]

Last time there was a long discussion on corrector plates I believe the conclusion was that the newer Chinese-made OTAs do not have matched correctors and that they could be replaced if broken. Personally I'd still mark the OTA and corrector and return it to the same position.

James

[Cath]

Yes I have read that it is just a myth that the glasses are matched up, I'll still mark them though.

I tend to believe they arn't matched up in production. I've been in electronics since I left school, and soon learnt how much time it takes to start trying to match transistors etc to each other, it's time consuming and very wastful (end up with lots of unmatched parts) - very bad for mass production lines.

[username]

Yep I would still mark the orientation as orientating the plate on a production line wouldn't be that hard a thing to do fast and maximise profit. It's a non-trivial curve on the SCT corrector plate unlike a maks spherical meniscus.

Maybe they've change what they're doing nowadays regarding forming the corrector plate and finding/grinding a mirror that gives lowest spherical abberation and they've sorted the accuracy of fabircation.

I'm looking forward to how you get on, when I use my mak in the daytime I can see that it could do with some flocking. Just waiting to get a new scope before I start dismantling my only one!

[Peter Drew]

I doubt whether blackboard paint would have much of an advantage over the original internal paint, if you do use this then use a water based paint to avoid the egassing of a solvent variety.

[MushroomBill]

A little while back a head pinged off one of the accessory holding screws on my C8. Horrible cheap screws! In order to remove its remains, I decided to remove the corrector. There was little to indicate inside the ota that anyone had marked a postion for the corrector previously so I agree with James:

the conclusion was that the newer Chinese-made OTAs do not have matched correctors and that they could be replaced if broken. Personally I'd still mark the OTA and corrector and return it to the same position.

I believe older models have cork/cardboard shims behind the corrector plate. None on mine - the 2008/09 model. There is a brown gasket of some sort which was just about adhering to the edge of the corrector.

Whilst the corrector was off, it was carefully cleaned. Then I flocked the scope with some flockboard as mentioned above. No adhesive to worry about and it is easily removable if necessary. I've used the wilko stuff on a newt before and its quite good but a bit fiddly in comparison.

Finally put it all back together... Just beware with the corrector plate screws!! Certainly don't overtighten them!!!! Initially though I didn't tighten enough so the corrector would rotate. Then collimate.

Just take it slow and steady.

[Cath]

Roger, roger and roger !

Thank you guys, all notes noted.

Will post some pics as soon as I start it this week.

[billhinge]

Hi Cath

Believe it or not I put the C11 back together on the bed , the weight makes it sink in the mattress a little and you can sit on the bed and steady the tube with your knee/leg or whatever!

[billhinge]

Hi Cath

Believe it or not I put the C11 back together on the bed , the weight makes it sink in the mattress a little and you can sit on the bed and steady the tube with your knee/leg or whatever!

[username]

There was little to indicate inside the ota that anyone had marked a postion for the corrector previously

Not all of them are marked but they suggest serial numbers and focusser positions are the marks on some

http://www.celestron...barticleid=1655

Although not sure if this is to do with matching them.

If you can buy stock plates and replace them that's good but I still can't see how they can get such a high order curve spot on every time so that its radially equal curve. I'd bet my last kroner that there's an optimal orientation for any corrector-mirror pair