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flocking a skywatcher 180 mak-cass


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Some very dubious statements in that article.

I'm not even going to comment on these:

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.
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.
I think that removing all extraneous reflections inside your ota mitigates if not eliminates the need to flock the inside of the baffle tube.
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Hi all.

Has anybody here tryed flocking a skywatcher 180 mak-cass.

I have some left over prostar flocking.

No, but i'm considering doing my mak 127. The main sticking point is the need to disassemble- apparently the rear cells are a bit tricky to get back right.

Will let you know how i get on if i pluck up the courage :)

Nb:my tentative experiments with a refractor suggest the main benefit to be had from flocking is with bright objects such as moon & planets.

Flocking the interior of the baffle-tube might make a difference (hard to do, I'd think), but flocking the main tube would be pointless (it wouldn't do anything)

Could you elaborate on why flocking the main tube would be pointless please?

My understanding is the light cone on a mak-cass expands from corrector to primary mirror, suggesting to me ,a good chance of "stray" light hitting the tube wall & reflecting back into the light path.

Of course, i may be labouring under a misunderstanding of the issues?

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Thanks for the flocking link. The inside of my tube has a nice shine to it just like that C11.

Im looking at removing the tube from the bottom of the ota and doing doing the flocking and then refit the tube.

I been sent a picture of a IM 715 delux thats been done.

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post-22110-133877539041_thumb.jpg

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my tentative experiments with a refractor suggest the main benefit to be had from flocking is with bright objects such as moon & planets.

With a Refractor, yes - and with a Newtonian even more so.

Could you elaborate on why flocking the main tube would be pointless please?

Sure: When benefits are to be had with flocking, it is abundantly clear simply by looking into the telescope with no eyepiece in place.

Just look! :) It's quite clear what's going on. In a refractor (for example), the eyepiece can clearly "see" the inside of the refractor tube. Any stray light seen on the sides of the tube here get focused directly into the image. On a well-made refractor with a well-baffled tube however, the inside of the OTA should be inky-black, so there's no problem.

When you look into the focuser tube of a Newtonian however, you can identify three main area which the eyepiece "sees" which will reduce the contrast - the inside of the tube directly opposite the focuser, and (reflected in the secondary) the inside edge of the OTA leading down towards the primary, and also that same section of tube, but seen from the opposite direction as reflected in the primary.

In an off-the-shelf Newtonian then, there's an awful lot of tube surface area throwing light directly into the eyepiece. Flock those surfaces, and you will see a huge improvement in contrast.

In a Mak-Cass however, all such reflections are masked off by the baffle-tube. There's no significant part of the inner surface of the main tube visible from the viewpoint of the eyepiece (there may be a little bit surrounding the reflection of the primary in the secondary, but not much).

What is visible - and quite clearly so - are stray reflections from the (typically poorly-baffled) baffle-tube itself. Point the tube at (e.g.) the moon and see just how much stray light is bouncing off the baffle-tube walls - quite a lot in my Mak 180 Pro. In and of itself, this isn't necessarily an issue, since it's proportional to the light of interest anyhow. Where it is a potentially a problem is where something is just outside the field of view. In that case, there is no light shown in the secondary, but the is a stray shard of it bleeding down the inside edge of the baffle-tube - this would suggest to me that it contributes to a potential loss of available sharpness and is a good candidate for some careful baffling (hard to do though).

In summary, if you can't see the stray light when looking into the focuser tube of a telescope, then there's no problem.

Edited by great_bear
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Sure: When benefits are to be had with flocking, it is abundantly clear simply by looking into the telescope with no eyepiece in place.

Just look! :( It's quite clear what's going on.......

In summary, if you can't see the stray light when looking into the focuser tube of a telescope, then there's no problem.

I've looked Great Bear, & i have to say, you are indeed quite correct!:)

Thankyou,

that's saved me one potential nightmare of a job....& created another....

Now were's my blackboard paint & sawdust for that shiny baffle tube? :(;)

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It's hard to do better than factory (unless there is a real issue). Most common cause of flocking Maks or SCTs are that someone else did that and you want to do it too :)

When I was collimating the SCT I had a standard flashlight pointed on the colimation screws and camera at the visualback showing the defocused star. The only way to cast light on the image was to direct the flash light directly on the mirror or draw tube. Flashing on the sides didn't do anything noticable with the image.

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Interesting - think I'll leave it alone as well.

Course if the 180 does ever get used and its as good as its supposed to be I will still want push me-pull me fans and an external focuser, oh and a Losmandy dovetail and a few other things.

To be honest the 180 has been a bit of a Jonah - everytime I take it out it clouds over.

Its probably going to be sold before I ever get to use it.

Edited by Astro_Baby
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