Flocking Advice

[mental4astro (Alexander)]

David,

This is the sort of thing that SHOULD be done in factory. Yet for their own reasons they don't and it has consequences for the end user. Yes, there is an element of risk for us as end users to do this and as a result it is up to the individual to decide if they want to undertake this and if they are then planning is important so to reduce the risk. There are ways to reduce the risk to the optics (not getting paint on them, etc), such as masking in ways that does not involve getting sticky stuff on the optics, or even leaving a short distance between base of say the baffle and where the paint starts. It may leave a short unpainted gap of a couple of mm, but will improve things in a significant way.

It is not just the outside of the baffle tube but the inside too. Look up the tube from the back end of the OTA and you will see a series of bright edges - these are the edges of the machined and black anodised aluminium. These also introduce stray light/scatter that impacts on contrast.

Eyepieces are less problematic. Even many inexpensive eyepieces come with blackened elements and good coatings to control internal reflections. There are some problematic eyepieces due to their design, but problematic eyepieces can be ferreted out quickly by doing side by side comparisons with the same scope. And this too may be a product of stray light from internal reflections from the scope if these have not been tempered. I have come across some contemporary (not cheap either) eyepieces that have internal reflection issues with small bright objects such as Jupiter and Venus, but these eyepieces thankfully are the exception.

The scope is the first point in the optical train, followed by the eyepiece and even your eyeball can have an impact as light reflects off the cornea from a bright source. Just don't fall into the trap of blaming a convenient scapegoat. It took me a long time to come to recognise the shortcomings of naked black anodised aluminium and how this impacts on contrast WAY MORE than we think, blaming the poor secondary mirror instead... When you look through other scopes of similar design and how their contrast is significantly better you need to look inside to see what THAT scope is doing different and not think it just because it is Brand "X" that that is the reason why. Brand "X" is not doing anything unobtanium-like. So what are the differences... It may surprise you how "simple" what they do is, though doing the fix is not necessarily easy as the end user.

Black 2.0 & Black 3.0

Remember that these are specialist paints designed for a specific purpose with artworks. These may not have the same adhesion properties that we expect the paint on our scopes to have. On bare anodised aluminium I would hazard a guess that there would need to be a primer used to ensure better adhesion of these specialist paints.

With this in mind, I looked back to my correspondence with the maker of these paints and I have emailed them today asking them about this aspect of using a primer first on bare metal. I'll report back on what they say.

Alex.

[wayne anderson (Wayne)]

Around 6 years ago I flocked the inside of my 12 inch Meade LX200, the resulting increase in contrast was not that noticeable, however when I painted the inside of the baffle tube with ultra-flat black paint the increase in contrast was indeed very noticeable, much less scattered light from the sharp edges of the baffles resulted in much better contrast on all objects, take note of the potential for scattered light from the sharp edges of the internal baffles in the photo.

[Dave882 (David)]

Alex- thanks so much I’ll be interested to hear what they say. I agree it makes perfect sense to tackle the biggest issues first. If there is a noticeable gain in contrast to be had with planetary viewing I’m keen to give it a go.

[Dave882 (David)]

Originally Posted by wayne anderson

Around 6 years ago I flocked the inside of my 12 inch Meade LX200, the resulting increase in contrast was not that noticeable, however when I painted the inside of the baffle tube with ultra-flat black paint the increase in contrast was indeed very noticeable, much less scattered light from the sharp edges of the baffles resulted in much better contrast on all objects, take note of the potential for scattered light from the sharp edges of the internal baffles in the photo.

Wayne that’s very encouraging to hear. Can I ask how you went about painting the inside of the baffle tube and what paint you used?

[wayne anderson (Wayne)]

There were many threads on the Cloudy Nights forum stating that krylon 1602 ultra flat black paint was good to use but very hard to find
even in the USA, this is just one of many discussions on krylon 1602 ultra flat black paint

https://www.cloudynights.com/topic/8...at-black-1602/

However I realised I already had a business account with an Australian supplier CRLaurence that stocks krylon 1602 ultra flat black paint , so I purchased a few cans.

https://www.crlaurence.com.au/crlapp...2&ModelID=4314


The painting process was a little tricky, I did not want to go through the detailed process of removing the primary mirror or baffle tube so after
carefully removing the corrector plate I made a protective donut shaped cover for the primary mirror out of card board and tape then using
card board, cling wrap and tape I carefully masked off all other areas so only the inside of the baffle tube was exposed. Then I cleaned off any
oily residue inside the baffle tube with a cloth and isopropyl alcohol and allowed to dry.

I starting with several light coats of paint until the inside of the baffle tube was fully coated then I allowed a further 14 days for a complete
outgassing of the paint before re-assembly, this paint is very smelly and gassy.

All went very well and there has been no issues with it for 6 years and it should do very well for many years to come.