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drexelpbp
sage
Reged: 01/21/08
Posts: 269
Loc: Phoenixville,PA
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For a 80mm short tube refractor can the same kind of flocking material used for newtonians be used instead instead of baffles with similar results?
Thanks for your input.
Gary
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Orion 8" intelliscope
Celestron CF 8' SCT
Celestron 8SE
Celestron C80ED
Orion ST120
Orion ST80
Orion 120 f/8.3
Orion Skyview Pro Deluxe 90 f/11
Celesrton SP C102
Celestron SP 150N
Various Televue, Baader, Orion and other EPS
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neo
professor emeritus
Reged: 02/12/08
Posts: 623
Loc: Iasi, Romania
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Yep..it's pretty much the same, although the best choice would be baffles and flocking between them. For newtonians the baffeling is quiet complicated but still I don't know why so many skip this step though. Probabely because of so many open tubes designs. So for a pro job baffles are indicated, but flocking is still a good option if you have a short tube or simply not enough room.
--------------------
Russian 15x50 binos
Home made 8" f/5 Newton on eq mount
Home made 70mm f/6 (Rodenstock Rotelar lens) Apo refractor
www.astronomy.ro
Edited by neo (10/03/09 07:10 PM)
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G Smith
super member
Reged: 11/22/07
Posts: 120
Loc: Central Ohio, USA
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Right On Neo. I am considering a bit of flocking on the front of my baffles also, plus the outside light shield. Gene
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Ian Robinson
Pooh-Bah
Reged: 01/29/09
Posts: 1165
Loc: Gateshead.NSW Nth Coast,Austra...
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Flocking is quicker and easier , I thought long and hard about baffling AND also flocking my OTA , bit decided it was too much bother and I don't have the carpentry skills to make good baffles.
I opted to flock using ProtoStar self adhesive stuff and despite some minor application technique issues (fixed with a stanley knife and some craft glue) , my flocking is stuck OK for a month now (had temps in the garage where the OTA is stored between 11oC and higher than 35oC.
Baffling would have added some mass to my finished OTA too , it's already 20kg with the tube rings attached and finderscope attached.
So far so good.
Edited by Ian Robinson (10/04/09 11:49 AM)
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Ian Robinson
Pooh-Bah
Reged: 01/29/09
Posts: 1165
Loc: Gateshead.NSW Nth Coast,Austra...
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Quote:
For a 80mm short tube refractor can the same kind of flocking material used for newtonians be used instead instead of baffles with similar results?
Thanks for your input.
Gary
Why not , just cut into thin strips and put a paper clamp (on one end attached to some fishing line and pull it through flock side down then lower the tube onto the sticky side and use an offcut of 2" water pipe to "press it" to the tube's interior face.
Heck , I wish I'd thought of that when I was flocking my 316mm OD x 1.270m long tube ....  .... would have made it a lot easier.
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drexelpbp
sage
Reged: 01/21/08
Posts: 269
Loc: Phoenixville,PA
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Thanks for the input.
I think I'll try the flocking and see how it works.
Anybody try this stuff that you apply adhesive to:
http://www.duchekconsult.com/atm_supplies.htm
--------------------
Orion 8" intelliscope
Celestron CF 8' SCT
Celestron 8SE
Celestron C80ED
Orion ST120
Orion ST80
Orion 120 f/8.3
Orion Skyview Pro Deluxe 90 f/11
Celesrton SP C102
Celestron SP 150N
Various Televue, Baader, Orion and other EPS
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Sarkikos
Pooh-Bah
Reged: 12/18/07
Posts: 1071
Loc: Suburban Maryland
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I've fully flocked my 10" Newt with Protostar and have been very pleased with the results. Objects are much more contrasty, backgrounds are darker, faint fuzzies are easier to see. I looked into baffling the tube and used the Newt program, but it is not something I would want to do. It is complicated, much more difficult than flocking to implement, and much more dependent on optical theory than simple flocking. Also, there seems to be more controversy among practitioners as to exactly how to baffle, what should be baffled, etc. I would avoid it for Newts, at any rate. I don't think it would be worth the time and effort required.
In comparison, flocking is very straightforward and driven more by common sense than optical theory. The only real controversies are what material to use for flocking, and whether to flock just opposite the focuser and above the primary or flock everything that light might hit in the optical train. I flocked everything, even the focuser, the diagonal holder, and the back and sides of the primary. I even left a lip of flocking sticking above the edge of the primary so I could bend it down to cover the bevel and a possible turned-down-edge. I'm done. I refuse to baffle!
Clear Skies,
Mike
--------------------
Celestron 10" f5 Newt on 1stBase (DSO)
Zhumell 8" f6 Newt, Bosma 6" f12 MCT (NSO)
6" f5 Newt, 130ST, 4.5" f4.4 Ball w/GLP, ST80 w/Crayford (RFTs)
C4-R (NSO/DS)
90mm f13 MCT (Luna/DS)
SkyMaster 25x100, 15x70
Zhumell 20x80
Barska XWA 10x50, 8x40
OptiView LPR 10x50
Const View 2.3x40
BV-125C
CG5, 2 drv / CG4, 2 drv, wood legs, ScopeStuff saddle / CG3, 1 drv
SV AZ / 501HDV on Bogen 055XB / P+ on Oberwerk
QuikFinder, Telrad
Orion Dynamo Pro 12, Dew-Not
Have GLP and not afraid to use it!
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mark cowan
Vendor (Obsidian Optics)
Reged: 06/03/05
Posts: 2159
Loc: salem, OR
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Both baffling and flocking can be equally effective, if done correctly. I flocked by 8" f/5.8 planetary dob with velvet years ago and the result was immediately apparent.
Flocking is probably easier, as you really need to know what you're doing to baffle properly.  For instance, the one thing you almost never see on truss dobs is a baffle on the focuser, let alone the adjustable (iris) that would work the best.
Best,
Mark
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Sarkikos
Pooh-Bah
Reged: 12/18/07
Posts: 1071
Loc: Suburban Maryland
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Mark,
The only place on my 10" Newt where you could say that I installed a baffle is where the focuser joins the OTA. I cut out a circle of black foam core to fit across the focuser opening at the OTA and then cut a hole in the middle of the foam core to exactly fit the focuser tube as it extends down into the OTA. I flocked both sides of the baffle with ProtoStar and then attached it securely to the focuser mount and the OTA opening. I do think this limited use of a baffle does help in producing nice contrasty views in my scope. However, I steer away from installing baffle rings inside the inner circumference of the OTA or on the diagonal mount. I just don't want to do, and I don't think it's worth my effort. I may be wrong, but from my experience here on CN, it seems that there is a lot of interest in baffling overseas, especially in England, but not so much here. Also, it seems that folks overseas have an interest in installing an adjustable iris in the focuser tube. I've investigated that, also, and I don't think it's worth the trouble. I think my limited use of a fixed baffle at the OTA end of the focuser is the best solution, and is a once-done let-it-alone mod. Those are the best.  IMHO, and YMMV.
Clear Skies,
Mike
--------------------
Celestron 10" f5 Newt on 1stBase (DSO)
Zhumell 8" f6 Newt, Bosma 6" f12 MCT (NSO)
6" f5 Newt, 130ST, 4.5" f4.4 Ball w/GLP, ST80 w/Crayford (RFTs)
C4-R (NSO/DS)
90mm f13 MCT (Luna/DS)
SkyMaster 25x100, 15x70
Zhumell 20x80
Barska XWA 10x50, 8x40
OptiView LPR 10x50
Const View 2.3x40
BV-125C
CG5, 2 drv / CG4, 2 drv, wood legs, ScopeStuff saddle / CG3, 1 drv
SV AZ / 501HDV on Bogen 055XB / P+ on Oberwerk
QuikFinder, Telrad
Orion Dynamo Pro 12, Dew-Not
Have GLP and not afraid to use it!
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mark cowan
Vendor (Obsidian Optics)
Reged: 06/03/05
Posts: 2159
Loc: salem, OR
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The focuser baffle is beyond the focuser tube and irises off everything beyond what the field stop of any given EP sees of the diagonal. It would seem like a lot of trouble because that field stop varies with EPs and so should the iris.
An open truss obviously can't be flocked down the tube, but OTOH there isn't a tube to reflect stray light in the first place. It's possible to baffle open (unshrouded) trusses so that no stray light gets into the focuser.
For a tube OTA newtonian it can be shown that for the tube itself only one (or possibly two) baffle ring is needed, part way up the tube, IIRC, by the geometry of possible reflections. Apparently building a light trap box opposite the focuser is more effective than any flocking, though.
Best,
Mark
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Sarkikos
Pooh-Bah
Reged: 12/18/07
Posts: 1071
Loc: Suburban Maryland
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Mark,
Quote:
The focuser baffle is beyond the focuser tube and irises off everything beyond what the field stop of any given EP sees of the diagonal.
What do you mean exactly by "beyond the focuser" tube? I have trouble following these types of discussions unless you are very specific. IMHO, I don't think it would be wise to have anything "beyond the focuser," if you mean by that, somewhere between where the focuser attaches to the OTA and the diagonal. It is bad enough that the focuser tube enters a bit into the OTA as an obstruction to incoming light during in-focus.
Quote:
It would seem like a lot of trouble because that field stop varies with EPs and so should the iris.
Exactly. That's why I only baffle right at the OTA wall, and I keep the baffle at the constant diameter of the focus tube itself.
Quote:
An open truss obviously can't be flocked down the tube, but OTOH there isn't a tube to reflect stray light in the first place.
I would think that an open truss would experience a greater problem from glare and ambient light entering the open tube from various angles, than it would if the scope were fully enclosed on the sides by an OTA. That would depend, though, on how free the site was from ambient light, and how nonreflective the inner surface of the OTA would be. I'd rather take my chances with a well-flocked OTA.
Quote:
It's possible to baffle open (unshrouded) trusses so that no stray light gets into the focuser.
It's much easier to have a solid tube OTA and flock everything. The only advantages I see to an open truss design is less weight and greater portability.
Quote:
For a tube OTA newtonian it can be shown that for the tube itself only one (or possibly two) baffle ring is needed, part way up the tube, IIRC, by the geometry of possible reflections.
Common sense is much easier and straightforward than optical geometry. Just flock all non-optical surfaces that could possibly be in the light path! (Except the spider vanes, of course, but they can be touched up with flat black paint.)
Quote:
Apparently building a light trap box opposite the focuser is more effective than any flocking, though.
What is a light trap box? How would it be designed and implemented?
Cheers,
Mike
--------------------
Celestron 10" f5 Newt on 1stBase (DSO)
Zhumell 8" f6 Newt, Bosma 6" f12 MCT (NSO)
6" f5 Newt, 130ST, 4.5" f4.4 Ball w/GLP, ST80 w/Crayford (RFTs)
C4-R (NSO/DS)
90mm f13 MCT (Luna/DS)
SkyMaster 25x100, 15x70
Zhumell 20x80
Barska XWA 10x50, 8x40
OptiView LPR 10x50
Const View 2.3x40
BV-125C
CG5, 2 drv / CG4, 2 drv, wood legs, ScopeStuff saddle / CG3, 1 drv
SV AZ / 501HDV on Bogen 055XB / P+ on Oberwerk
QuikFinder, Telrad
Orion Dynamo Pro 12, Dew-Not
Have GLP and not afraid to use it!
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sixela
Postmaster
Reged: 12/23/04
Posts: 10874
Loc: Boechout, Belgium
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Quote:
Both baffling and flocking can be equally effective, if done correctly.
That's a physical impossiblity. A baffle will stop 100% of the light, flocking will still reflect *some* stray light if ight hits it. Little, but *some*.
Equal means equal. On a refractor and between the focuser and the secondary on a Newt, baffling is *very* effective - more than flocking.
It's been easy for me to test: I have a Newt UTA with a ring baffle on the top and a light shield. Putting it in sunlight, it's easy to see the flocked UTA that sees sunlight is "black", but not as black as the flocked bits that are in the shadow of the baffle or the light shield...
--------------------
400mm f/4.46 self made Dobsonian on Tom Osypowski equatorial platform
Orion Starblast (114mm f/4 reflector, Alt/Az)
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Sarkikos
Pooh-Bah
Reged: 12/18/07
Posts: 1071
Loc: Suburban Maryland
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Sixela,
I think we've gotten into a similar discussion in another thread. This all sounds familiar. I do use a flocked, foot-long cylindrical light shield on the sky-end of my OTA, but I don't consider that a baffle. It does help shield the optics from glare and makes the image more contrasty. (I have a suspicion that if the light shield is fairly long, it may also have the added benefit of shielding light from a turned-down-edge on the primary?) I have no doubt that hard-core baffling, where concentric rings are attached inside the OTA, would improve the image, though I am not sure if it would make a very large improvement in a Newt over just a thorough flocking. But I do not think it would be worth the effort required to carefully measure the optical train, do the necessary ray-tracing and/or work through a program like Newt, and actually design and attach the baffles exactly where needed. (There is the additional detail of "sharpening" the baffle edges. Many baffling afficionados have pet theories about how sharp the edges should be, at what angle, etc.) Flocking is much more straight-forward and relys on common sense rather than optical theory and temperamental freeware programs. And I have seen that flocking works. Also, there is no chance that flocking would diminish the light transmission through the optical train to the eye, but there is a definite danger of that occurring if baffling is not installed exactly right. As I said, and keeping all this in mind, I do not think baffling is worth the effort required to do it, at least not for most amateur astronomers with solid tube Newts. Refractors are a different story. But again, baffling requires precision and application of theory, or at least a series of tedious trials and experiments, while flocking does not.
This baffling business does appear to be more popular outside the States. Most conversations I have about baffling are with folks from Europe. Also, here in the US, you almost never hear anyone mention an adjustable iris. I bet every amateur I know from visiting dark sites would not have ever heard about adjustable irises. Just an observation.
Clear Skies,
Mike
--------------------
Celestron 10" f5 Newt on 1stBase (DSO)
Zhumell 8" f6 Newt, Bosma 6" f12 MCT (NSO)
6" f5 Newt, 130ST, 4.5" f4.4 Ball w/GLP, ST80 w/Crayford (RFTs)
C4-R (NSO/DS)
90mm f13 MCT (Luna/DS)
SkyMaster 25x100, 15x70
Zhumell 20x80
Barska XWA 10x50, 8x40
OptiView LPR 10x50
Const View 2.3x40
BV-125C
CG5, 2 drv / CG4, 2 drv, wood legs, ScopeStuff saddle / CG3, 1 drv
SV AZ / 501HDV on Bogen 055XB / P+ on Oberwerk
QuikFinder, Telrad
Orion Dynamo Pro 12, Dew-Not
Have GLP and not afraid to use it!
|
mark cowan
Vendor (Obsidian Optics)
Reged: 06/03/05
Posts: 2159
Loc: salem, OR
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Quote:
That's a physical impossiblity. A baffle will stop 100% of the light, flocking will still reflect *some* stray light if ight hits it. Little, but *some*.
True, but picky.  Good point. Baffles can introduce problems with tube currents, possibly worse than the fractional % of light the flocking reflects.
Anyway, I was only talking about flocking the tube itself.
Best,
Mark
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mark cowan
Vendor (Obsidian Optics)
Reged: 06/03/05
Posts: 2159
Loc: salem, OR
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Quote:
What do you mean exactly by "beyond the focuser" tube?
This has gotten well OT for the original poster, but here's a rough drawing of what I mean (updated - see attached).
The "light trap box" was written up by Harold Suiter somewhere (sorry) in regards to minimizing stray light in a solar scope. It's a box that sits on the opposite side of the focuser, black or flocked inside, and any light that goes into it doesn't easily come out.
Quote:
Common sense is much easier and straightforward than optical geometry.
Not. It's pointless to flock parts that can never reflect light to the focuser, just like it's pointless to install multiple ring baffles all along the tube in a newt, because the angles of reflection (which can just be drawn out on a piece of paper) dictate that stray light can only travel certain limited routes to the focuser, and the rest doesn't matter.
Best,
Mark
Edited by mark cowan (10/06/09 04:37 PM)
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neo
professor emeritus
Reged: 02/12/08
Posts: 623
Loc: Iasi, Romania
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Being such a controversial subject, I guess the most straight foreword thing to do is to do a test.
Two (almost) identical telescopes, one with buffles and the other floacked and some test chart (like those for resolution and contrast tests) placed at distance to be viewed through the scopes. This way the contrast could be judged directly for both situations, with a camera or with naked eye.
--------------------
Russian 15x50 binos
Home made 8" f/5 Newton on eq mount
Home made 70mm f/6 (Rodenstock Rotelar lens) Apo refractor
www.astronomy.ro
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sixela
Postmaster
Reged: 12/23/04
Posts: 10874
Loc: Boechout, Belgium
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Quote:
I do use a flocked, foot-long cylindrical light shield on the sky-end of my OTA, but I don't consider that a baffle.
It is one, though. It's not an OTA ring baffle, but it's a baffle nonetheless.
Quote:
I have no doubt that hard-core baffling, where concentric rings are attached inside the OTA, would improve the image, though I am not sure if it would make a very large improvement in a Newt over just a thorough flocking.
In a *Newt*, I actually have serious doubts that many baffles (except the light shield, a flocked baffle just in front of the primary or on the mirror box, a baffle between focuser and secondary and on some scopes the shroud, which is actually helpful on truss scopes for other reasons than baffling) actually do anything useful.
In fact (as Mark correctly points out) a baffle that's installed where none should live actually hurts if it kicks a tube current into the light path.
But we weren't talking about a Newt.
Quote:
Flocking is much more straight-forward
Flocking is complementary to baffles. Actually, flocking also only works because it uses the same principles as baffling but on a smaller scale.
Quote:
And I have seen that flocking works.
Of course it does. But in a refractor, there's no question that a tube wall in the shadow of a baffle or unseen (because the unlit side of a baffle is in front of it) is darker than a flocked tube wall. No need for fancy theories, it's just Plain Common Sense.
Quote:
but there is a definite danger of that occurring if baffling is not installed exactly right.
Yes, duh!
Quote:
As I said, and keeping all this in mind, I do not think baffling is worth the effort required to do it, at least not for most amateur astronomers with solid tube Newts.
We weren't talking about solid tube Newts. And I disagree as far as some baffles are concerned (see above).
Quote:
Refractors are a different story.
Exactly. Let me quote the first words of this thread: "For a 80mm short tube refractor".
So, what exactly are your on-topic observations?
Quote:
But again, baffling requires precision and application of theory,
Gosh, fancy that. Something which you actually have to design. Surely that's something we must all strive to avoid, especially in the "ATM, Optics and DIY" forum.
Quote:
Also, here in the US, you almost never hear anyone mention an adjustable iris.
My baffle there is not adjustable - just large enough for the widest eyepiece I use. It does make my light shield a lot smaller and makes the UTA a lot lighter. And yes, I'm afraid the dimensions (of the baffle opening and the light shield) are all properly designed.
--------------------
400mm f/4.46 self made Dobsonian on Tom Osypowski equatorial platform
Orion Starblast (114mm f/4 reflector, Alt/Az)
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sixela
Postmaster
Reged: 12/23/04
Posts: 10874
Loc: Boechout, Belgium
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Quote:
Being such a controversial subject,
It's not a controversial subject. At least not for anyone who makes the effort to understand what's going on.
And for refractors, the only controversy I read about are about how some commercial scopes are baffled so aggressively as to vignette the objective and whether that's done on purpose to mask some spherochromaticism or not, and whether that's a Good Thing.
Another subject is whether it's a Good Thing to have an oversized tube (so as to reduce the number of necessary baffles).
I haven't seen anyone advocate "down with baffles" in a refractor forum, and absolutely everyone (Synta, Jinghua, etc., Stellarvue, William Optics, APM, TMB, Astrophysics) except the people selling the lowest of the lowest end baffles their refractors.
--------------------
400mm f/4.46 self made Dobsonian on Tom Osypowski equatorial platform
Orion Starblast (114mm f/4 reflector, Alt/Az)
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davidpitre
Carpal Tunnel
Reged: 05/10/05
Posts: 1826
Loc: Central Texas
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Quote:
absolutely everyone (Synta, Jinghua, etc., Stellarvue, William Optics, APM, TMB, Astrophysics) except the people selling the lowest of the lowest end baffles their refractors.
Not Televue.
Gary. I've used the flocking material from duchekconsult.com, and can say it is very effective.
If you do a good job of flocking and darkening any potential source of reflection along the light path, you can get very close to the effects of baffling.
--------------------
David
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Sarkikos
Pooh-Bah
Reged: 12/18/07
Posts: 1071
Loc: Suburban Maryland
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Mark,
Quote:
This has gotten well OT for the original poster,
Yes, indeed, but that occurred early on in this thread (2nd post). Think of it as somewhat expanding the topic instead of going completely OT.
Quote:
but here's a rough drawing of what I mean (see attached).
This is pretty much what I did but I placed the baffle flush on the inner wall of the OTA at the focuser hole, not out in the OTA. I am reluctant to put anything else out into the initial light path to the primary. It is bad enough that the diagonal, spider vanes, and sometimes the focuser tube are out there. And at least in my focuser, the focuser tube is quite a bit smaller in diameter than the focuser hole itself, so the drawing is not entirely applicable in that respect. At any rate, how would you even place a longitudinally-aligned baffle out in the OTA? Would you suspend it from a diagonal spider vane? There is also the possibility of the baffle dropping onto the primary. I would prefer not to.
Quote:
The "light trap box" was written up by Harold Suiter somewhere (sorry) in regards to minimizing stray light in a solar scope. It's a box that sits on the opposite side of the focuser, black or flocked inside, and any light that goes into it doesn't easily come out.
Well, Suiter IS the man. This LTB sounds like it would make sense in a solar scope, where there is no lack of available light from the object. But IMHO it does not sound like something that would help in a scope used for finding faint fuzzies. Wouldn't it be better to just flock opposite the diagonal and be done with it? Why put another possible obstruction in the light path? But thanks for the concept. I had never heard of an LTB. I'll look it up and do more research.
Quote:
It's pointless to flock parts that can never reflect light to the focuser, just like it's pointless to install multiple ring baffles all along the tube in a newt, because the angles of reflection (which can just be drawn out on a piece of paper) dictate that stray light can only travel certain limited routes to the focuser, and the rest doesn't matter.
There is such a thing as light scatter. If we do a thought experiment and take an OTA in which the inner walls are all glossy white, and we only flock those parts that we think are directly in the light path, even after doing careful ray tracing, I can imagine that we would still get quite a bit of ambient light entering the eyepiece that you might not think would have been reflected there. It's not worth it to be stingy when it comes to flocking. Just basically flock everything inside the OTA except the optical surfaces and the spider vanes. Why not? What do you stand to lose, except a few bucks for the flocking? Compared to $600+ eyepieces, complete flocking is a cheap way to improve your viewing experience.
Cheers,
Mike
--------------------
Celestron 10" f5 Newt on 1stBase (DSO)
Zhumell 8" f6 Newt, Bosma 6" f12 MCT (NSO)
6" f5 Newt, 130ST, 4.5" f4.4 Ball w/GLP, ST80 w/Crayford (RFTs)
C4-R (NSO/DS)
90mm f13 MCT (Luna/DS)
SkyMaster 25x100, 15x70
Zhumell 20x80
Barska XWA 10x50, 8x40
OptiView LPR 10x50
Const View 2.3x40
BV-125C
CG5, 2 drv / CG4, 2 drv, wood legs, ScopeStuff saddle / CG3, 1 drv
SV AZ / 501HDV on Bogen 055XB / P+ on Oberwerk
QuikFinder, Telrad
Orion Dynamo Pro 12, Dew-Not
Have GLP and not afraid to use it!
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