Improvements from a flocked scope

[Size9Hex]

I recently lined my scope with black flocking material and wondered whether my experiences might help other folks decide whether it's something they want to do.

Before I lined it, I saw a number of good before/after photos of flocked scopes online, confirming the scopes look blacker inside, but I didn't find much solid information on the benefit when observing. Not easy in the absence of two otherwise identical scopes side by side on the same night pointed at the same target, although it would be interesting to know if anyone has done this!

My own experience over four sessions since flocking the scope (a 10 inch Skywatcher solid tub Dob) and observing from a suburban garden with a few surrounding houses and streetlights is as follows:

The glare when observing the moon was significantly reduced in comparison to a few months of sessions with an un-flocked scope. This improvement was pretty obvious and made for much more pleasant viewing. Despite this, I'm not convinced I could see anything extra that I couldn't see before. Possibly this is because the moon is high enough contrast to break through the glare. Nonetheless, the removal of the annoying glare on the moon, by itself, has made me very happy I went to the effort.

I also tried a before/after comparison (a couple of weeks apart) with an area of sky perhaps ten degrees above an upstairs window in my house. With the window lit, the glare was obvious and distracting in the eyepiece, but was no longer evident when the scope was flocked. This glare was previously bright enough to spoil low contrast targets. Unfortunately, the sky had moved on a bit, and the seeing/transparency were no doubt different on the nights I compared it on, so it's hard to quantify, but I'm fairly confident there would be a noticeable side by side difference on DSOs in these conditions.

I've not noticed any difference at all on targets (mainly DSOs) further away from lights (e.g. near the zenith). That's not to say there is/isn't a difference, but if there is then it's minor enough that I didn't spot it. Maybe a side by side comparison would be different. Based on this, I'm not expecting to see a difference when I observe from darker locations with no surrounding lights.

Jupiter I think might be marginally better than before with less glare reducing the contrast.

Overall, a few quid and a couple of hours were very well spent in my opinion. The benefit was much greater than when I tried a dew shield type of light shield. There have been some interesting posts recently on the merit of top end refractors and eyepieces for improving the view. In terms of benefit per cost of flocking, the gains on observing the moon and near the surrounding lights have been anything but marginal!

Three sheets of the flocking material were needed to line the 250px and the focuser tube, with plenty left over. Taking the scope apart wasn't hard, but the primary mirror needed a bit of persuasion to go back in.

Hope that's helpful/interesting!

[acey]

Very useful, thanks. I baffled my 12" Skywatcher Flextube a few years ago, and found that the focuser was particularly worth dealing with to reduce stray light at the eyepiece. I took advice from an S&T article by Gary Seronik (2001   Apr    128    Telescope Techniques : Newtonian Baffling Made Easy - can't find online, unfortunately). The basic principle is to look through the focuser in daylight (without eyepiece) and deal with any light you can see. With that approach you don't need to flock an entire tube; the extra gain from complete flocking is probably minimal. It's light reflecting into the focuser that causes all the issues.

 

[Knighty2112]

Just in the process of flocking my ST120 frac. I flocked the main lens dew shield over the main objective lens last night, and will start to flock inside of the telescope next weekend. Not sure how much better the detail and contrast may be on objects as clouds stopped play, but observing from a light polluted back garden mostly I'm hoping to cut down the glare from street lamps, and also tone down the glare from the moon, Jupter & Venus when observing. If I do find some better sky contrast when observing galaxies or other DSO's then that will be a bonus too. 

[Dave Lloyd]

Watching this with interest mate. If you've got oblique light striking internal surfaces and being scattered it's got to be better to absorb it. I'm not particularly plagued with light pollution but if it works for you I reckon I'll give it a go.

[Size9Hex]

39 minutes ago, acey said:

Very useful, thanks. I baffled my 12" Skywatcher Flextube a few years ago, and found that the focuser was particularly worth dealing with to reduce stray light at the eyepiece. I took advice from an S&T article by Gary Seronik (2001   Apr    128    Telescope Techniques : Newtonian Baffling Made Easy - can't find online, unfortunately). The basic principle is to look through the focuser in daylight (without eyepiece) and deal with any light you can see. With that approach you don't need to flock an entire tube; the extra gain from complete flocking is probably minimal. It's light reflecting into the focuser that causes all the issues.

 

Agreed about the area opposite the focuser being the most important. I figured if I was taking the scope apart anyway to reach it, then I may as well do the whole lot, and then I wouldn't be wondering "what if" . For what it's worth, when I was halfway through the job, the flocking inside of the tube didn't appear all that black when I'd only done part of it, but did appear very black when I'd done all of it, so I think the cumulative effect of killing as much of the double/triple/etc reflected light as possible might make a bit of a difference.

[ronl]

I'll be flocking my 200p sometime soon, I have the flocking materiel from Flo, but I will be replacing the focuser, a MoonLite CR2 dual rate, I'm 

wondering if the MoonLite will need flocking, maybe, I'm sure someone will know, haven't ordered the focuser yet, as it's a birthday present from 

my wife, even she doesn't know yet, so I'm leaving it till the last minute.  

I will be following this thread with interest.

[Knighty2112]

I had a little more time on my hands today than I thought I would do, so to kill the boredom (hehe!) I set to flocking inside the tube of my new 2" Crayford focuser. Certainly seems darker, especially when looking at an angle through the focuser with the diagonal out of the way. Next week I'll do all the inside of my frac. For now I'm hoping for a little clear sky at some point tonight to have a looksie through!  

[John]

I have the Moonlite CR2 focuser fitted to my 12" dobsonian. The inside of the drawtube seems very black to me.

On my dob I've only flocked the section of the tube opposite the focuser and a 12" deep strip around the tube immediately above the primary mirror. I didn't notice any difference to the views so it was a "peace of mind" thing.

I've found using a semi-circular light shield around the top aperture of the scope makes far more difference because it keeps stray light out of the top of the tube and off the secondary mirror.

 

 

[Piero]

Interesting thread and a very honest opinion, Paul  

I always wondered about the benefits of flocking the tube. Well, now I know a bit more!  

Thanks for sharing!

Piero

[Knighty2112]

Just finished flocking my ST120 frac this afternoon. Certainly much darker inside of it, so much so that when I was applying the flocking I was doing it blindly mostly, which made it a little tricky. Now I just need to do some observations with it and see how it all goes. Hopefully there will be an improvement, but time will tell.