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Deadening a 6" f/5 Newtonian

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#1 Sky Muse

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Posted 07 January 2016 - 09:26 AM

...and to all manner of stray-light, whether it be artificial or natural.  Blacker than the darkest of dark nebulae it shall become wi'in; as black as a black hole e'en.

 

The patient is ready...

 

 

6 f5 optical tube.jpg

 


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#2 gene 4181

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Posted 07 January 2016 - 09:40 AM

 Ever thought of covering the outside , insulating the tube. Neopreme insulation, or reflectix a foam covering with the silver ?  It does help with thermals from your own body in use. The skyward side of the scope continues to super cool while the ground side retains some heat and from your legs , just a thought. I've been doing it , I think it helps, but YMMV.


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#3 Sky Muse

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Posted 07 January 2016 - 10:29 AM

Can you post an image of yours as described.  I, and others, would like to see it.  However, I'm afraid that my extremities(arms and legs) don't put off much heat; metabolism, you know.  In any event, I moved the optical tube over to a traditional alt-azimuth quite some time ago.  The ground-end of the optical tube is no longer near the ground, nor near my legs...

 

6 f5v2.jpg


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#4 Sky Muse

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Posted 07 January 2016 - 10:46 AM

Just look at what I had had some inkling of, but now revealed in its entirety; appalling.  The image of the tube interior on the left was taken without the flash; and the one on the right, with...

 

tube interior-before.jpg

 

 

Be careful when removing the base of the red-dot finder from the optical tube.  This threaded reinforcement plate on the inside came close to hitting the secondary when it fell...

 

base plate.jpg


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#5 cliff mygatt

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Posted 07 January 2016 - 11:14 AM

Do you plan to flock the inside of the tube?  Scope Stuff has what you need.  I flocked my 12 inch Orion XTi and Meade 8" SCT and am very happy with the improvement to contrast!


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#6 Sky Muse

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Posted 07 January 2016 - 12:48 PM

As a matter of fact, I have most of a roll of Protostar left over; and after a failed attempt at flocking the 8" f/5, given its rough and uneven interior, but I will be flocking the area opposite its focusser however, at least.  It'll be a cinch to flock with the ultra-smooth interior of the steel-tubed Orion.  I plan on flocking the focusser's drawtube as well.  The back and edges of the secondary mirror will be painted with ultra-flat black, and also the edge of the primary.



#7 havasman

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Posted 07 January 2016 - 12:48 PM

I'm not completely sure what your project is but if you're manipulating the tube and you've got it stripped then you should flock it and the Scopestuff material works very well. All that shiney interior will be cured. Different folks prefer different strategies as to where and how much of the tube to flock but your scope might be entirely flocked with one large size order from Jim.


Edited by havasman, 07 January 2016 - 03:50 PM.

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#8 Sky Muse

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Posted 07 January 2016 - 04:09 PM

And all this time I thought that the front cowling, or collar, was of metal, and as that of the primary mirror cell on the opposite end.  It's plastic, but since it serves only to stiffen the front edge of the metal tube, that's fine.  I won't be overlapping the flocking into and onto the inner surface of the cowling once it's back in place, and since the surface was satinised, I took sandpaper to it then painted it with the ultra-flat black...

 

front cowl.jpg



#9 Sky Muse

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Posted 07 January 2016 - 07:47 PM

To ensure that the flocking will adhere to the interior of the metal optical tube, glossing of same will be required, and with a clear gloss enamel.  All of the holes on the outside were sealed with cheap painter's tape from Dollar Tree; no Scotch-brand required in this case, and the cheap tape works just as well and for a fraction of the price.  An equally-cheap kitchen-type trash bag was then cut to size, placed around the tube and sealed with said tape, thereby preventing any overspray from reaching the outside of the tube ...

 

interior glossing.jpg

 

After a day of drying and curing, the tube will then be flocked.



#10 Sky Muse

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Posted 07 January 2016 - 09:17 PM

Nice and glossy and shiny...

 

tube interior-before2.jpg



#11 Sky Muse

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Posted 12 January 2016 - 01:52 AM

I decided to flock the optical tube with six 4" wide strips, each the length of the tube, save the front-cowling and mirror-cell spacings: 25 & 3/8"...

 

flocking2.jpg

 

 

The camera was thrown for a loop when taking the photo of the flocked side of the strips, as though "they" forcibly expelled all light away from "themselves", thereby illuminating "their" surroundings; interesting...

 

Each strip was numbered to ensure that the scissor-cut edges of the strips would mate perfectly once installed, not unlike a puzzle...

 

flocking5.jpg

 

 

Painter's tape was used to mark the position of the first strip, precisely along the tube's axis, and where it would straddle the tube's seam...
 

flocking7.jpg

 

 

Each strip had its backing folded back a bit from one side, which made the installation practically a "snap"...

 

flocking3.jpg

 

 

The following images were only resized then sharpened.  Believe it or not, the room was fully-illuminated by the six-light(60W each) ceiling fixture and two table lamps; "curiouser and curiouser"...

 

flocking4.jpg

 

 

The first strip was actually #2, as I wanted #1 to "lie" near to the focusser's opening.  As seen in the right image, that most-critical area opposite the focusser is flocked seamlessly, the strips laid so that the last, odd strip would land near the focusser's opening as well.  The last strip, #6, will be installed once careful measurements are made.

 

 

This, my first attempt at flocking any telescope, ever.  Thank you for looking.


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#12 buddyjesus

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Posted 12 January 2016 - 09:35 PM

much cleaner job putting in the flocking than I did.  well done.


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#13 Sky Muse

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Posted 16 January 2016 - 06:18 PM

The optical tube is now fully flocked, and with the last strip slightly overlapping the first.  The second and third images from the top were taken with the flash enabled...

 

flocking10.jpg

 

flocking9.jpg

 

flocking11.jpg

 

 

Next, the flocking and blackening of the components...

 

tube components.jpg



#14 Sky Muse

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Posted 16 January 2016 - 08:11 PM

I see a reflection upon the flocking...

 

reflection.jpg



#15 Sky Muse

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Posted 17 January 2016 - 06:21 AM

The mostly-plastic 1.25" focusser, disassembled.  What little glue-grease there was was cleaned/removed from the rack and pinion and later replaced with Teflon-based Superlube...

 

focusser.jpg

 

Something tells me that those three drawtube shims came from spare parts totally unrelated to telescopes.

 

 

The drawtube requires flocking and blackening, of course.  The inside of the drawtube has been prepped with clear gloss enamel, and portions of the drawtube de-chromed and blackened...

 

focusser2.jpg

 

 

I had flocked the bottom portion of the outside of the drawtube, but it didn't work out as planned, so I blackened it instead.  Flocking of the drawtube was successful...

 

focusser4.jpg

 

 

In place of the shims for the drawtube, self-adhesive green felt was used.  The focusser seems smoother as a result...

 

focusser3.jpg

 

 

Next, the primary and secondary mirrors/assemblies...



#16 Sky Muse

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Posted 19 January 2016 - 01:46 AM

The secondary mirror assembly exploded...

 

secondary assembly.jpg

 

What a reflective mess.

 

The spider assembly, now deadened with the ultra-flat black spray...

 

secondary assembly2.jpg

 

 

Scotch-brand painter's tape was used to protect the mirror's surface during painting...

 

secondary assembly3.jpg

 

*WARNING: I don't know if I would apply even painter's tape onto a mirror that's showing signs of deterioration, however slight, as it might lift the coating; nor to a coating that's much more than five years old, or has been exposed to extreme conditions for less than that.  The mirror shown is almost three years old, but has only been exposed to the elements for less than a year.

 

 

Finished...

 

secondary assembly4.jpg

 

birds.jpg


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#17 Sky Muse

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Posted 20 January 2016 - 02:03 AM

The primary mirror assembly exploded...

 

primary mirror assembly.jpg

 

 

First, selected areas of the mirror cell were masked, then the cell was painted with the ultra-flat black spray...

 

primary mirror assembly2.jpg

 

About 25% of the shiny heads of those three screws jutted out beyond the mirror's edge before, but are now quite dead.

 

 

My flat-black is noticeably blacker than Synta's.  Naughty, naughty, Synta...

 

black shades.jpg

 

 

I decided against painting the primary mirror's edge, and for ease in re-coating in future, notwithstanding replacing both mirrors outright.  But, I had no choice in painting the secondary mirror, as I didn't want to add any thickness, however slight, to its edge.  It's obstructive enough as it is.  However, I did flock the edge of the primary mirror...

 

primary mirror assembly4.jpg

 

 

The primary mirror assembly before and after; note the slight brightening of the background within the right, "after" image...

 

primary mirror assembly3.jpg

 

The heads of the screws and the tops of the metal plates of the mirror clamps were also painted.  Every little bit helps.

 

:whee:



#18 Abhat

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Posted 20 January 2016 - 06:57 AM

Skymuse thanks for posting the photos. I would love hear your report on what kind of difference this makes in the contrast i.e before flocking and after flocking.


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#19 jkwhinfrey

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Posted 20 January 2016 - 09:36 AM

So would I.

 

I've been following with interest because I'd like to do the same with my Skywatcher 150PDS. I have quite a lots of light bouncing around my back garden location, so I have an ongoing programme of mitigation  ;)

 

James


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#20 Kipper-Feet

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Posted 20 January 2016 - 12:54 PM

Sky Muse; see re-attached, here, your single composite image of the Before and After photos from your post #17.

 

The only difference is that I have partially boosted the gamma brightness of the entire image. As such, the Before and After photos, contained in the composite image, have been boosted by the exact same amount.

 

Notice how incredibly well the ultra-flat black painted flocking of your bezel ring and cell has worked in this exaggerated image.

 

I have a primary mirror washing coming up this Spring and now want to emulate your flocking treatment of both mirrors.  I've already flocked my focuser's draw-tube as well as the OTA wall opposite the focuser.

 

Thank you for posting as you've done.  

 

One other suggestion here but I have no photos to show you.  Purposefully set up your scope such that the back outside face of the primary is pointing towards a well illuminated, light colored wall or garage door.  Do this at night in the dark.  Now look down the front end of the tube towards the primary.  

 

Notice whether you have a halo of light entering the back end of the tube through the gap in between the back face of the cell and the front face of the bezel ring.  This gap is caused by the space required for the primary collimation screws. Light reflected off the wall or garage door can enter through here partially defeating all the good work that you've already done above.

 

In real life applications, dimmer sources of this back end light intrusion might be concrete surfaces, paved road surfaces and deck surfaces.  All of which would effect a Dobsonian type reflector even more egregiously than a Newtonian reflector sitting way up there on a tripod mount.

 

One way to solve this is to attach a foam-rubber light baffle to the back-end such that it covers the gap.  In mine, and since I'm not presently using a fan, I made provision for a covered vent to allow the free passage of air.  This permits the flow of air but prevents the intrusion of unwanted light.

 

I really do appreciate the learning and motivation that you've brought to me with this 'deadening' thread of yours.  Thank you.


Edited by Richard Roseweir, 20 January 2016 - 03:16 PM.

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#21 Sky Muse

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Posted 20 January 2016 - 07:44 PM

Hi Richard,

 

Thank you for your comments and the altered example.  Here's the paint itself...

 

ultra-flat black.jpg

 

 

It's also the same paint I used for my Parks fibreglass 8" f/5 optical tube...

 

Parks fibreglass ota9a.jpg

 

Its primary mirror cell might exhibit said halo within described exercise, as it's quite open and airy...

 

primary assembly5.jpg

 

 

Back to the 6" f/5 primary, these are the original images, straight from the camera, unretouched, other than re-sizing and sharpening; the brightness and contrast were not altered, as I had done in addition with the first image.  At the time of the shots, there were two table lamps and an overhead light-fixture of six 60W candelabra-type bulbs illuminating the area; in other words, full, normal lighting...

 

primary mirror assembly5.jpg

 

 

...odd, that.

 

 

Cheers,

 

Alan


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#22 Sky Muse

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Posted 20 January 2016 - 07:51 PM

Skymuse thanks for posting the photos. I would love hear your report on what kind of difference this makes in the contrast i.e before flocking and after flocking.

 

Thank you, and I certainly will after it's finished.  I especially want to try out the new 30mm again on Orion's Trapezium.  Before, at 25x, I could barely detect a separation between the close pair of the four stars.



#23 Sky Muse

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Posted 20 January 2016 - 08:02 PM

So would I.

 

I've been following with interest because I'd like to do the same with my Skywatcher 150PDS. I have quite a lots of light bouncing around my back garden location, so I have an ongoing programme of mitigation  ;)

 

James

 

I didn't feel comfortable doing it until I understood the process of collimation to my satisfaction, and in order to reinstall the components and re-collimate successfully.  The inspiration to finally do so was due solely to the recent acquisition of a single 1.25" ocular.  I chose it over the GSO and Baader 32mm Plossls, and I'm quite glad that I did...

 

Vixen NPL 30mm2.jpg



#24 Sky Muse

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Posted 21 January 2016 - 02:22 AM

My, it's awfully dark down there...

 

flocking12.jpg

 

However...

 

 

I thought I might get away with not having to glue the self-adhesive underside of the long edge of the last strip over and on top of the flocked edge of the first strip, but to no avail... :fingertap:

 

epoxy.jpg

 

 

I've epoxied the short length from the front of the tube to the focusser's opening, at present, and successfully...

 

epoxy2.jpg

 

 

The remaining length will be cut/notched into three sections, then epoxied one section at a time.  The trick is is to coat both the self-adhesive side of the edge of the last strip applied, and the flocked side of the first and slightly less than the width of the former, then to wait until the epoxy almost hardens before pressing down.  This can be determined by keeping a watchful eye on the remaining epoxy, and by constantly twirling a toothpick through it.  Applying too much epoxy, of course, will result in excess being squeezed out and onto the flocking beyond the joint, so do be careful.

 

 



#25 jkwhinfrey

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Posted 21 January 2016 - 05:56 AM

I didn't feel comfortable doing it until I understood the process of collimation to my satisfaction, and in order to reinstall the components and re-collimate successfully. 

 

I know what you mean. I've just reached that point myself and I'm thinking it's time to give it a go.

 

I use Vixen SLVs which can be had relatively cheaply secondhand, but my longest is 12mm. Vixen make some good eyepieces. I've never tried their Plossl range but they do seem highly rated.

 

I'm looking forward to the results!

 

James


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