36 replies to this topic

[Princess Leah]

I read many posts of people removing the baffles of 'Classic Refractors' to prevent vignetting and allow the use of 1.25 inch EPs.

 

Why bother for a 0.25mm increase in field stop?

 

These telescopes always seem best used for high power; planets, double stars etc.

A 0.965 focuser can still fully illuminated a ES 14mm 82 degrees.

 

Am I missing something?

 

Leah.

 

[RichA]

Would you really mount a wide field eyepiece in a crappy 0.965 (excluding Takahashi's) diagonal and PRAY the ONE set-screw will holds the thing?

[Princess Leah]

No I normally attach a 0.965 to 1.25 adapter (providing there is enough in focus). Then use a 1.25 inch prism 

 

I'm talking about removing baffles, not diagonals?

[Max Coe]

I leave the baffles alone and use a .965 - 1.25 diagonal like you do. The only modification that I have done is to flock the drawtube. 

[apfever]

 

Why bother for a 0.25mm increase in field stop?

 

You mean 0.285 inch diameter larger field stop?  That is significant. 

A lot of times the baffles are not correctly placed and vignette quite a bit of the primary. I think most baffling issues are due to vignetting period, and not necessarily just to increase from a 0.965" to 1.25" field.  

[jgraham]

It depends on the scope, but I use my trusty old 0.965” to 1.25” conversion diagonal with excellent results.

[Princess Leah]

You mean 0.285 inch diameter larger field stop?  That is significant. 

A lot of times the baffles are not correctly placed and vignette quite a bit of the primary. I think most baffling issues are due to vignetting period, and not necessarily just to increase from a 0.965" to 1.25" field.  

Good spot. So more like 7mm.

 

So I guess people remove them to get another 0.5-1 degree FOV.

Personally I have found the baffling to be so good in the majority of old Towa, Pentax,Carton etc that I'd be loath to touch them. I believe the excellent baffling of these scopes are partly responsible for the excellent contrast they provide.

I've rarely came across an 'old' scope with incorrect baffling.

The new 60mm Synta F15s have one single incorrectly placed baffle and a shiny interior/ tube.

 

However when I read on these threads that people are removing baffles and 'getting much more light to the eyepiece ' I do wonder if that is the right phrase to use.

Maybe better try a shorter focal length eyepiece that doesn't vignette (16mm for instance) and try the telescope on a bright object like the moon. Then decide if you need to make any alterations.

[deSitter]

The fundamental problem is specular reflection from both the tube wall and focuser tube. You can remove any drawtube baffle and use flock paper instead, with better performance. When I upgraded my modern 90mm refractor to 2' I had to move the tube baffle closer to the focuser..

 

-drl

[Princess Leah]

The fundamental problem is specular reflection from both the tube wall and focuser tube. You can remove any drawtube baffle and use flock paper instead, with better performance. When I upgraded my modern 90mm refractor to 2' I had to move the tube baffle closer to the focuser..

 

-drl

Yes I did that with my TS optics 60/900. And I refitted the baffle in the correct place. Turns out the optics are very good!

[ccwemyss]

Baffles should be designed with the field stop of the widest eyepiece, or the diagonal of the sensor, in mind. If the baffles produce a cone that is smaller at that point, then the field of view will not be fully illuminated. For visual use, a small amount of falloff will not be noticed, while in imaging vignetting will be visible.

 

Adapting a 0.965" telescope to 2" eyepieces for a wide FOV will likely result in perception of a dimmer view, and moving the baffles further back will relieve that. But if another baffle isn't inserted closer to the objective (or flocking added) it can also result in stray light reaching the eyepiece, resulting in a brighter field with lower contrast. Of course, if someone is doing that for a 60mm objective, there's such a small difference between the aperture and the field stop that it may be better to take out the baffles and simply flock the tube. 

 

The classic Pentax 65/85/100 series is easier to adapt because Pentax designed for a 38mm diameter set of eyepieces that they sold for straight-through use. I can use 2" eyepieces with my 85 and 100, and see a bright, high contrast field.  On the other hand, my AP 6"f9 came with one 3" baffle, at the mid-point of the focal length, which gave it a very small fully illuminated field. Replacing that with a six baffle system significantly increased the brightness of wide fields, while retaining the contrast. 

 

For high power viewing, where an eyepiece such as a 4 to 6mm ortho has a tiny eye lens, moving the baffles doesn't offer any benefit. Because lunar and planetary observing at high power is a common use for a small aperture, f15 refractor, moving the baffles may not be worth the effort. Such a scope wouldn't be a top choice for wide field sweeping.

 

That said, in some cases, the baffles are just held by friction, and with some bumping, they can slide forward without it being noticed. In that case, it's still worth moving them back, but not removing them. 

 

Chip W. 

[deSitter]

Baffles should be designed with the field stop of the widest eyepiece, or the diagonal of the sensor, in mind. If the baffles produce a cone that is smaller at that point, then the field of view will not be fully illuminated. For visual use, a small amount of falloff will not be noticed, while in imaging vignetting will be visible.

 

Adapting a 0.965" telescope to 2" eyepieces for a wide FOV will likely result in perception of a dimmer view, and moving the baffles further back will relieve that. But if another baffle isn't inserted closer to the objective (or flocking added) it can also result in stray light reaching the eyepiece, resulting in a brighter field with lower contrast. Of course, if someone is doing that for a 60mm objective, there's such a small difference between the aperture and the field stop that it may be better to take out the baffles and simply flock the tube. 

 

The classic Pentax 65/85/100 series is easier to adapt because Pentax designed for a 38mm diameter set of eyepieces that they sold for straight-through use. I can use 2" eyepieces with my 85 and 100, and see a bright, high contrast field.  On the other hand, my AP 6"f9 came with one 3" baffle, at the mid-point of the focal length, which gave it a very small fully illuminated field. Replacing that with a six baffle system significantly increased the brightness of wide fields, while retaining the contrast. 

 

For high power viewing, where an eyepiece such as a 4 to 6mm ortho has a tiny eye lens, moving the baffles doesn't offer any benefit. Because lunar and planetary observing at high power is a common use for a small aperture, f15 refractor, moving the baffles may not be worth the effort. Such a scope wouldn't be a top choice for wide field sweeping.

 

That said, in some cases, the baffles are just held by friction, and with some bumping, they can slide forward without it being noticed. In that case, it's still worth moving them back, but not removing them. 

 

Chip W. 

 

I would not even attempt to upgrade a classic < 4" to a 2" focuser. Yes in that case a lot of checking is going to be needed.

 

-drl

[T1R2]

Sometimes the main tube baffles are right, sometimes they are wrong, usually when you hear of us knocking out baffles its the ones in the drawtube, but we usually go for both to make them perfect. going from .965 to 1.25" accessories, the smaller aperture baffles in the drawtube for the 965 will not allow full illumination of the 1.25 diagonal, sometimes its quite noticeable vignetting.   

[Princess Leah]

Sometimes the main tube baffles are right, sometimes they are wrong, usually when you hear of us knocking out baffles its the ones in the drawtube, but we usually go for both to make them perfect. going from .965 to 1.25" accessories, the smaller aperture baffles in the drawtube for the 965 will not allow full illumination of the 1.25 diagonal, sometimes its quite noticeable vignetting.   

So quite a few of the older scopes have baffles placed incorrectly even for a 0.965 focuser?

I haven't came across that yet. Maybe I should check my old Towa and Tasco.

I thought QC standards were much better in the 'good old days.'

[T1R2]

So quite a few of the older scopes have baffles placed incorrectly even for a 0.965 focuser?

I haven't came across that yet. Maybe I should check my old Towa and Tasco.

I thought QC standards were much better in the 'good old days.'

Yes, my old tasco has one main tube baffle that was waay to small (its aperture was 26.5mm) , it was placed right before the altitude bolts halfway down the tube and effectively reduced the aperture of the scope, I knocked it out and made some baffles with craft foam. and knocked out the two 14mm drawtube baffles and made a few more but they were all the same size, just one layer in diameter placed evenly throughout the drawtube to stop tube wall reflections which are the most problematic in the old .965 drawtubes because they are a little narrower and harder to baffle without clipping the light cone, Since my tasco has a 1.25" OD drawtube the Celestron 1.25" prism attaches directly to the end of the drawtube with a hose clamp and it works perfect, I don't like the .965- 1.25" hybrid diagonals.  

[Princess Leah]

Yes, my old tasco has one main tube baffle that was waay to small (its aperture was 26.5mm) , it was placed right before the altitude bolts halfway down the tube and effectively reduced the aperture of the scope, I knocked it out and made some baffles with craft foam. and knocked out the two 14mm drawtube baffles and made a few more but they were all the same size, just one layer in diameter placed evenly throughout the drawtube to stop tube wall reflections which are the most problematic in the old .965 drawtubes because they are a little narrower and harder to baffle without clipping the light cone, Since my tasco has a 1.25" OD drawtube the Celestron 1.25" prism attaches directly to the end of the drawtube with a hose clamp and it works perfect, I don't like the .965- 1.25" hybrid diagonals.  

By itself was the craft foam not a bit floppy, or did you adhere it to a rigid support?

I think my Tasco is the same, that's a good tip thanks. 

0.965 to 1.25 inch hybrids seem to be an extinct species in Ireland. 

[Kasmos]

So quite a few of the older scopes have baffles placed incorrectly even for a 0.965 focuser?

I haven't came across that yet. Maybe I should check my old Towa and Tasco.

I thought QC standards were much better in the 'good old days.'

My '57 Unitron 114's baffles cut off the light cone more than a few other 60mm scopes I've compared it to. I'd like to move one or both. But while working on another 114 dented tube, I found they were in so tight I bent them getting them out. Afterwards I straightened them, but the effort makes me hesistant and procrastinate fussing with the '57's mint tube.

[T1R2]

By itself was the craft foam not a bit floppy, or did you adhere it to a rigid support?

I think my Tasco is the same, that's a good tip thanks. 

0.965 to 1.25 inch hybrids seem to be an extinct species in Ireland. 

Its much harder to make them by cutting out circles and putting a centered hole of a certain size in the baffle, instead I cut 10mm wide strips and lined them one inside the other until it was the right size, then press fitted then inside the tube with a PVC pipe with a circle of cardboard on the end that is just a few millimeters smaller than the diameter of the tube, and placed depth marks on the pipe, that way I knew how deep to push them in.  

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[deSitter]

BTW if the scope is going to be used for direct solar viewing, having non-metal innards of any sort is probably not the best idea You can probably get away with a tube of flock at f/15.

 

-drl

[T1R2]

BTW if the scope is going to be used for direct solar viewing, having non-metal innards of any sort is probably not the best idea You can probably get away with a tube of flock at f/15.

 

-drl

Well, people use enamel paint on baffles inside drawtubes..etc, , and as long as the foam is not at the focus point its not gonna do much, it might get warm but not any warmer than it setting out in direct sunlight. 

[highfnum]

A CN user  removed baffles to reduce light scatter in  solar coronagraph usage

seems counter intuitive

but needed in this specific case

[Bomber Bob]

... in some cases, the baffles are just held by friction, and with some bumping, they can slide forward without it being noticed. In that case, it's still worth moving them back, but not removing them.

 

I leave them in - and make sure they're positioned correctly; or, where I need them to be.

 

For my 1970s Jaegers 50mm F12 kit build, I had a CNer make custom 3D-printed disks with the correct apertures; then, I glued these to antique brass tube sections:

 

 

My idea was to wring every last photon of contrast & resolution from this excellent small lens.

[Princess Leah]

Its much harder to make them by cutting out circles and putting a centered hole of a certain size in the baffle, instead I cut 10mm wide strips and lined them one inside the other until it was the right size, then press fitted then inside the tube with a PVC pipe with a circle of cardboard on the end that is just a few millimeters smaller than the diameter of the tube, and placed depth marks on the pipe, that way I knew how deep to push them in.  

This is a very interesting and cleverly engineered technique. Thanks for sharing.

[T1R2]

This is a very interesting and cleverly engineered technique. Thanks for sharing.

You're welcome, just keep in mind that I do not use any glue, and I unscrew the lens cell from the tube and use the inside of the tube to make them the right size by cutting them a couple millimeters longer in length, then wrapping inside the tube and cutting it where the ends overlap, I trim off 1mm at a time until they fit together end to end, then I take it out and secure that with a small sliver of electrical tape on the outside side that goes up against the tube wall, then I finish lining the right amount of pieces inside that one. 

 

Just remember that you start by pushing the deepest ones in first and work your way toward the front opening.  I also measure where they are placed by using the front edge because these are not razor edge baffles but they work great if placed correctly, I can place the full moon outside the edge fov and get no glare.

I have 5 baffles in my 60x800mm tasco main tube and they are all in the first half of the tube, starting at the front of the scope to right before where Yoke altitude screws attach halfway down. The first baffle after the lens is one single layer of craft foam, the next baffle is 2 layers, the next one is 3...etc

 

Then the rest are in the drawtube, but these are just one single strip of that 1/16" craft foam, placed evenly spaced so that when I look through the tube at my kitchen light one ends when the other begins.  Also these are a little thinner at 3/16" - 1/4" wide, I used an old piece of wooden broom handle to make the baffle pusher for the drawtube, it has a thick circular disk of corrugated cardboard screwed to the end just a millimeter smaller diameter than the drawtube to push these in,  the large sized Elmers Purple Glue Stick I have also used to push in drawtube baffles this is a tight fit, but works on my red / black tasco 49TR drawtube, though I do not know if this will work on other tasco drawtubes.

[ccwemyss]

Its much harder to make them by cutting out circles and putting a centered hole of a certain size in the baffle, instead I cut 10mm wide strips and lined them one inside the other until it was the right size, then press fitted then inside the tube with a PVC pipe with a circle of cardboard on the end that is just a few millimeters smaller than the diameter of the tube, and placed depth marks on the pipe, that way I knew how deep to push them in.  

I use a fly-cutter in my drill press, but I turn it by hand -- doesn't take long with 1/32" aluminum. First I cut the circles, with the corners of the sheet clamped to a piece of plywood on the drill press table. The fly cutter uses a brill bit in the center in addition to the bit on the arm, so there is a centered hole. Then I adjust the arm to the different diameters to cut the holes, with the center bit keeping them centered on the outer diameter.

 

I position them either using three pieces of long, 6/32 all-thread and black nylon nuts (as a complete, slide-in assembly), or just cut flock paper to go in front and behind each one.

 

Chip W.  

[Princess Leah]

You're welcome, just keep in mind that I do not use any glue, and I unscrew the lens cell from the tube and use the inside of the tube to make them the right size by cutting them a couple millimeters longer in length, then wrapping inside the tube and cutting it where the ends overlap, I trim off 1mm at a time until they fit together end to end, then I take it out and secure that with a small sliver of electrical tape on the outside side that goes up against the tube wall, then I finish lining the right amount of pieces inside that one. 

 

Just remember that you start by pushing the deepest ones in first and work your way toward the front opening.  

Great info, thanks again.

I found the 'deepest one' best inserted lens side first (put in approximate position). Was using an old fishing rod protector tube to reposition!

L.