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digital_davem

Value of flocking/painting inside of tube

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Hi

I was re-fitting the new rings for my classic Prinz 660 today (which required removing the focuser to get them on and off) and I happened to shine a torch down the tube out of curiosity.  There are 4 baffles of various sizes that I could see but everything inside looks like shiny metal (it might possible have had some paint once, there is evidence of what looks likes bits of paint spray - or it might just be dirt).

Does this au naturel metal finish cause a problem of reflections, or do the baffles prevent that?  I've read about people matte black painting their OTAs and/or  flocking. Would there be any value in me investigating these options for a 3" refractor?

Cheers

Dave

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The baffles do reduce internal reflections but it certainly wouldn't hurt to paint as much of the inside as you can. I just used matte black spray paint on the two sections accessible from either end.

Its worth doing the focuser draw tube as well. While you're in there, push out the baffles as they may cause 1.25" eyepieces to vignette.

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I'm not sure with a refractor :huh:

If you think about the light path through the tube, it's narrowing all the time, moving away from the tube walls, from the rear of the objective down to the diagonal and thence to the eyepiece.

I'd flock the interior of the dew shield if that is shiny but I'm not sure I'd bother flocking the tube walls between the light baffles. Might be a pretty tricky operation with a narrow and long refractor tube as well.

I'd also leave any baffles that are in the drawtube in place (sorry Roy) unless you are sure that one is cutting into the light path.

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There's a pretty good Vis on you tube by 'Astro shed' that demonstrates the flocking and painting of an ST80 Ota Tube.

 You may find this useful.

  I think the vids called 'ST80 MODS'.

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I'm not sure with a refractor :huh:

If you think about the light path through the tube, it's narrowing all the time, moving away from the tube walls, from the rear of the objective down to the diagonal and thence to the eyepiece.

I'd flock the interior of the dew shield if that is shiny but I'm not sure I'd bother flocking the tube walls between the light baffles. Might be a pretty tricky operation with a narrow and long refractor tube as well.

I'd also leave any baffles that are in the drawtube in place (sorry Roy) unless you are sure that one is cutting into the light path.

No need for apologies John:), I mentioned doing this because I have the same scope and found it to be minutely beneficial- at least to my eyes. With my scope it's now a moot point as I have upgraded the focuser

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No need for apologies John:), I mentioned doing this because I have the same scope and found it to be minutely beneficial- at least to my eyes. With my scope it's now a moot point as I have upgraded the focuser

What have you upgraded to? Not that I want to seem as if I'm copying everything you do (although I have been looking at the skytee2 ;-) ) - especially as I haven't even looked through it properly yet.

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Well, I haven't actually seen it yet as the scope isn't finished. I've been told it's a standard Synta dual speed- so something that would be supplied with Skywatcher telescopes.

MrsC gave me permission to spend "some money" for my imminent 40th birthday. I wanted something that I wouldn't want sell at some point in the future so I decided to make some improvements to the Prinz. As it isn't finished yet, and the big day hasn't yet arrived, I can't say what the end result will be, although I don't think I'll be disappointed in any way.

Dave, feel free to take influences from my scope setup but beware that it has cost quite a bit so far, and I got lucky with some of my purchases - everything is second hand. Probably more than most would think it was worth for an old 76mm achro.

Edited by Roy Challen

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Well, I haven't actually seen it yet as the scope isn't finished. I've been told it's a standard Synta dual speed- so something that would be supplied with Skywatcher telescopes.

MrsC gave me permission to spend "some money" for my imminent 40th birthday. I wanted something that I wouldn't want sell at some point in the future so I decided to make some improvements to the Prinz. As it isn't finished yet, and the big day hasn't yet arrived, I can't say what the end result will be, although I don't think I'll be disappointed in any way.

Dave, feel free to take influences from my scope setup but beware that it has cost quite a bit so far, and I got lucky with some of my purchases - everything is second hand. Probably more than most would think it was worth for an old 76mm achro.

Don't worry, I'm definitely working on the cheap. My 660 outfit cost £27 and that has set the tone for what seems a sensible price for accessories!

Talking of cheap, I've managed to figure out a way to mount my OTA on the stronger pan and tilt head I have by removing the arca swiss clamp from the ball head and fixing a manfrotto QR plate under it where the ball head normally fits then attaching the whole thing to the arca swiss bar I have fixed to my rings. It's all lighter duty than the usual dovetail stuff but along the same lines. The pan and tilt is a lot easier to use than a ball head.  There is still a bit of flex in the tripod. I haven't yet worked out whether it is it the centre column or the legs. There is a video mod on youtube about how you can do without the centre column for a more rigid mounting. I might try that.

It also occurs to me that if a EQ mount is just a pan and tilt with a built in offset from the horizon, would a 3 way pan and tilt not make a cheap EQ? Just set the offset to match the Earth's inclination, then it should track. Or am I thinking my geometry all wrong?

I was out last night with my camera rather than telescope. Using a 300mm lens, 2x teleconverter and facturing in the 2x crop factor of my m4/3 sensor, I got the equivalent of 12x which was just right for the Pleides.  I found that anything slower than about 1/10th sec was showing some double imaging. Don't know if that is the tripod wobbling - does the earth spin that fast? And boy, are the unprocessed results noisy! I do quite a bit of long exposure photography using 10 stop ND filters so I'm used to 5 minute exposures but that are always at base ISO and of something more substantial than dots of light. I can't see myself being anything other than a dabbler at astro photography, that seems a recipe for poverty...

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Did you get the box, tripod and mount too? £27 for the OTA on its own is a great price.

I very much doubt that a pan and tilt will be much use for AP, but perhaps some of the imagers on here know otherwise?

I did have a go at AP a couple of years ago, but found I was spending far too much time behind a computer and nowhere near enough time behind an eyepiece. I gave up the AP before I spent too much money on something I was only ever going to be average at.

Edited by Roy Challen

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Did you get the box, tripod and mount too? £27 for the OTA on its own is a great price.

I very much doubt that a pan and tilt will be much use for AP, but perhaps some of the imagers on here know otherwise?

I did have a go at AP a couple of years ago, but found I was spending far too much time behind a computer and nowhere near enough time behind an eyepiece. I gave up the AP before I spent too much money on something I was only ever going to be average at.

The £27 got me the box, the OTA, dew shield, visual back, prism diagonal, terrestrial prism corrector, 3 eyepieces, the collection of tubes I now believe to be a Barlow, a mystery naked cemented doublet lens about a centimetre across in a plastic tub, two eyepiece filters, a heavy weight, an arm to put the heavy weight on, two flexible cables with knobs on, a collar and bar for the sun thing, the sun thing plate, some wingnuts and misc bist of foam in plastic bags. Missing was the tripod and most of mount.

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Nice one! The mount is nice but not up to the job of supporting this scope properly- maybe if it was half the length.

I haven't used any of the other bits and bobs except for the eyepieces. If yours are the same as mine, the H20 is actually quite good, the HM6 is not much cop, and the Or4 works but gives too high a mag on anything other than the Moon and even then, it's a bit dim.

Do not use the Sun filter! This type is dangerous.

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....Do not use the Sun filter! This type is dangerous.

A point well worth making Roy :smiley:

If I've ever acquired one of these nasy things with a bunch of eqiupment, I've smashed the thing and thrown it away so that nobody else could ever be tempted to use it.

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Nice one! The mount is nice but not up to the job of supporting this scope properly- maybe if it was half the length.

I haven't used any of the other bits and bobs except for the eyepieces. If yours are the same as mine, the H20 is actually quite good, the HM6 is not much cop, and the Or4 works but gives too high a mag on anything other than the Moon and even then, it's a bit dim.

Do not use the Sun filter! This type is dangerous.

I've not actually been able to see anything through the 6mm or 4mm! The H20 works but is dim and has a very wobbly looking outer image circle. I suspect vignetting. If I screw the little brass lens on the end of the eyepiece (I assume this is the Barlow out of its tube) it works much better with a crisp outer image circle.  The two Antares plossls I got in 1.25" size seem vastly superior.

I'm considering throwing away the sun filter as a threat to live and limb.

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I've not actually been able to see anything through the 6mm or 4mm! The H20 works but is dim and has a very wobbly looking outer image circle. I suspect vignetting. If I screw the little brass lens on the end of the eyepiece (I assume this is the Barlow out of its tube) it works much better with a crisp outer image circle.  The two Antares plossls I got in 1.25" size seem vastly superior.

I'm considering throwing away the sun filter as a threat to live and limb.

Having lived with the H20 and similar eyepieces for a couple of years when I first bought a scope (Japanese 60mm refractor from the 1960's) I can agree that even an average 1.25" plossl is a big step up in performance.

The poor quality eyepieces supplied with these scopes and rather wobbly mounts gave the scopes a rather poor reputation. Put them on a decent mount and stick a decent eyepiece in them and the scopes are transformed into quite nice performers.

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With Newtonian reflectors with white tubes I have found more benefit visually to flock an external portion of the tube opposite the eye that's not in use. That eye is then looking at a black background so no brightness is added to the view of the other.   :smiley: 

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I considered flocking my 8" reflector, but found that by simply placing a foam extension to the end of my scope, this prevented much of the visible stray light from entering the scope, and to my eyes, there is an improvement. I was also concerned in how to get the hose from my Dyson inside the scope to remove any specs on the flocking?

The Refractor will not need dysoning, but do consider a longer dew tube.

I also observe from a double sheeted tent, almost total darkness except for the light in the focuser. No red lights either? To me, this is very important. Dark adapted eyes and a foam extension tube is about as good as it can get from my street light polluted winter garden.

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UPDATE:

I have flocked! 

I did the front section behind the objective to the first baffle and the section in front of the focuser up to the last baffle.  It looks to me like this latter section was originally given some matte black paint in the factory but more a light dusting than a full coating.

I have also flocked either end of the focuser draw tube up to the baffles inside the tube. 

That leaves the baffles and the two middle sections of the OTA between the centre baffles which seem to have been left with a remarkably polished chrome finish out of the factory (!), and the interior and baffles of the draw tube.  I'm considering getting some blackboard paint for these. I read somewhere that it works better if mixed 50:50 with, er, flour. Plain or self raising, I wonder?   It looks pretty tricky to get access but I'm thinking of something like a paintbrush taped to a cane or something.

The flocking material (from Wilkinsons/Wilko) also serves double duty as new felt for the dew shield. Better that the electrical tape I've been using which made the dew shield very difficult to remove. I've also lined the edges of the Finnish Licorice tin lid I use as a lens cap. It's now easier to get on and off.

No idea if any of this will make the slightest difference but it feels like I've done my duty :icon_biggrin:

Dave

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The Prinz 660, so improved, should make for a splendid double-star refractor.

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Flocked the inside of the dew shield.  Blackboard paint to be delivered tomorrow.  Hope I don't make a mess of the internal painting - big gloopy blobs on the knife edges of the baffles probably a bad idea...

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Flocked the inside of the dew shield.  Blackboard paint to be delivered tomorrow.  Hope I don't make a mess of the internal painting - big gloopy blobs on the knife edges of the baffles probably a bad idea...

I use an ultra-flat black spray when blackening an optical tube, focusser drawtube, et al...

post-47381-0-48374400-1453093287.jpg

A spray-finish is more uniform, and the particulate-laden mist might possibly penetrate to areas that a brush would otherwise miss.

The outside of the optical tube would need to protected, using painter's tape and a kitchen trash bag...

post-47381-0-61621700-1453093251.jpg

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I use an ultra-flat black spray when blackening an optical tube, focusser drawtube, et al...

attachicon.gifultra-flat black.jpg

A spray-finish is more uniform, and the particulate-laden mist might possibly penetrate to areas that a brush would otherwise miss.

The outside of the optical tube would need to protected, using painter's tape and a kitchen trash bag...

attachicon.gifinterior glossing2.jpg

The trouble with my telescope is you'd need a 3 foot long spray nozzle to reach the middle!

I'm going to mix my blackboard paint 50:50 with flour (plain, I think) to create a flock-like 3d paint (some suggest crushed walnut shells) and apply it a dab at a time with a small brush attached to a thin stick.  I imagine it will take a while!   The big baffle near the objective and the smaller one at the eyepiece end and the interior of the focus tube should be reason straightforward but it's a long way to the centre sections with access through the baffle holes making it trickier. The two centre sections of the tube walls are a beautiful polished metal as well. In theory, the baffles should make this not matter but from my experience of using old unblackened camera lenses I'm suspicious of unpainted metal.

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The trouble with my telescope is you'd need a 3 foot long spray nozzle to reach the middle!

I'm going to mix my blackboard paint 50:50 with flour (plain, I think) to create a flock-like 3d paint (some suggest crushed walnut shells) and apply it a dab at a time with a small brush attached to a thin stick.  I imagine it will take a while!   The big baffle near the objective and the smaller one at the eyepiece end and the interior of the focus tube should be reason straightforward but it's a long way to the centre sections with access through the baffle holes making it trickier. The two centre sections of the tube walls are a beautiful polished metal as well. In theory, the baffles should make this not matter but from my experience of using old unblackened camera lenses I'm suspicious of unpainted metal.

Done!

I taped a small artist's paintbrush to a chain of wooden cooking skewers. Very bendy! 

I mixed the blackboard paint with flour to give it more texture then painted it on all the baffles and the tube walls in between. Not so easy to paint with a bendy 3 foot long paintbrush but I got there is the end. I also painted the focuser (baffles, inside tube and any external surfaces and edges that looked like they could reflect any light anywhere. 

Looking down the tube from either end reveals it is now very dark in there.

No idea whether it will make the slightest difference, opinion's around the web differ widely, but can't do any harm.

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