Flocking SCT :)

DENMONKEY (Brett) · #1 04-04-2009, 05:45 PM

Hi all,

With all of this wet weather I do what we all do when we can't get out and that is have a fiddle.....with my scope of course

When I picked up my c8 SCT I noted there were some condensation streaks on the inside of the corrector plate.
Now up until a little while ago I was ok with this as it didn't appear to effect the image as far as I could tell. Still bugged me though.
That was until a cool night and I saw the effects of the dew on the corrector plate when trying to tweak my collimation.
I was shocked

to say the least how quickly the corrector was affected when I removed the dew shield. It's only a self made soft foam that I got from clark rubber but it's good to know it's doing it's job and damn well.
After a quick blast with the hair dryer I was back to viewing in no time but left the collimation for a later date.

Now whilst shining the torch at the corrector plate to view the dew on it, I again became very aware of the streaking on the back of the plate.
Enough of this, I figured if the dew had such an obvious result on my viewing surely even these light streaks will be taking their toll.

Armed with demineralized water (as advised on IIS) I got all set up.
Unfortunately I don't have an allen key small enough for the corrector plate bolts....if you can call them that . They're tiny

So the question here is, what size are they?
I'll need to grab an allen key to match obviously but in considering their size, I'm guessing I may need to go to a specialty shop ?? jaycar maybe ?

I've read all the advice and how tos I can run my eyes over and am confident as one can be for the first time in getting the job done.

Asides from the question above, I stumbled onto this
http://www.backyardvoyager.com/c11flock.html
and was wondering should I do a job lot and flock the thing whilst I'm in there ?
I know lots of dobs get done but this would be a tad more challenging I guess, but should be easy enough once the corrector plate is off.
Anyone done it ?
Results ?
Anything to be be aware of when I'm doing the job?

Of course any other advice is also appreciated

Cheers Brett

gbeal · #2 04-04-2009, 05:53 PM

Go for it. Apart from dropping something, or over-zealous tightening (causing something to break) you can't really do anything that can't be fixed.
Flocking is well worth the effort even if only in your mind.
If you are at all unsure, then take a heap of pictures as you go, so you can re-trace your steps.
Gary

gb_astro · #3 05-04-2009, 10:14 AM

Flocking material can be a pain to work with.
If you are doing the main OTA tube I would recommend
removing it from the rear cell beforehand.

gb.

Paul Haese · #4 05-04-2009, 10:24 AM

Before you get too carried away, you need to have a bit of a read on dismantling.

I have a how to on doing this for a C14, but the C8 is basically the same. Pay special attention to setting up registration makes. Later in the how to I have talked about flocking etc.

http://paulhaese.net/peltierstoSCT.html

Best of luck.

Starkler (Geoff) · #5 05-04-2009, 12:44 PM

Is flocking necessary? That central tube from the centre rear of the scope acts as a baffle. How much of the side of the ota tube is visible looking into the focuser?

AlexN · #6 05-04-2009, 12:52 PM

I agree with gb, remove the rear cell before you do any flocking, as it will be VERY easy to accidently touch the mirror during the flocking process, and trust me, grubby prints on the mirror are going to bug you a lot more than a few light streaks on the corrector! Whilst a few prints on the very outter edge of the mirror are not going to affect viewing or imaging in any way, you will know they are there, and it will drive you NUTS!

I've looked through 2 C11's one flocked, one unflocked, I must say the difference was MILDLY noticable, probably moreso under dark skies.. Is it worth it? only you can decide.

Alex.

DENMONKEY (Brett) · #7 06-04-2009, 05:42 PM

Cheers all for the replies.

Thanks Paul for the advice and pics on the reg marks.
I'm aware of the requirement to return everything back into it's correct placement and alignment but tbh had only considered maybe 2 marks. I do really like your approach and will use that even if I only end up simply cleaning the corrector.

Quote:

Is flocking necessary?

That is the questions I'm asking really.

from the site I added in the original post they state
"I've flocked a C5 and put it up against an unflocked C8 on deep sky objects, and the flocked C5 shows more contrast and nebulosity extent, cleaner images on bright objects, and more resolution on globulars. I think flocking has the effect of improving an SCT by two magnitudes of light grasp. How can this be? Optical authorities will tell you that an SCT system looses
about 30% of its light grasp in internal reflections and loss of contrast. Flocking is the easiest way to solve this problem."

even Alex's comment of 'I must say the difference was MILDLY noticable'

suggests that it maybe worth the effort considering I'm already in there.
I'd be cool with mildly noticeable .

If it was just to perform this job then I wouldn't be considering it.

While I like to pull stuff apart just to see how it works I'm the sort that usually ends up with a few spare bits at the end of the job and am asking myself where THESE come from

I'd prefer not to pull the whole assembly apart if I could avoid it.
Maybe I could just flock the upper OT and secondary assemblies as a compromise.

Oh and if anyone can still suggest where to get the allen keys for the job or size of the bolts holding the retainer ring from the corrector plate that would be brilliant.

AlexN · #8 06-04-2009, 06:09 PM

I figure if you're already in there, then why not.. It cant hurt, and any improvement is an improvement...

Cant help regarding the size of the bolts holding the retaining ring.. I thought they were phillips head screws?

Robert9 (Robert) · #9 06-04-2009, 06:56 PM

My scope's plate accepts a 3.5mm Philips head screwdriver. Pick up from Jaycar or wherever, a set of small instrument sized Philips screw-drivers. A set won't set you back much.
Robert

Paul Haese · #10 06-04-2009, 08:06 PM

You can pick up imperial allen keys or even metric sets from your local hardware.

I am not sure about flocking the secondary assembly though.

In terms of flocking though, I have noticed quite a lot of contrast boost and colouring in planetary detail as a result of the flocking. So yeah it is worth it.

DENMONKEY (Brett) · #11 06-04-2009, 10:38 PM

Quote:

Originally Posted by Paul Haese

You can pick up imperial allen keys or even metric sets from your local hardware.

Checked again just to be 100% sure and yup allen key required.
I've a few sets both imperial and metrical. I believe they are imperial in size though.
The smallest I have there is 5/64 and even that is still too large

Quote:

In terms of flocking though, I have noticed quite a lot of contrast boost and colouring in planetary detail as a result of the flocking. So yeah it is worth it.

Quote:

It cant hurt, and any improvement is an improvement...

That's what I'm thinking. Any small improvement is still a step in the right direction.
It's almost as much about the act of doing it, as it is for the results.

You know .....get in and have a go

Just hope it's more just trial, rather than trial and error