9694 replies to this topic

[Orion68]

Part of the reason I made the replacement dew shield too long is because the lens cell is 

projecting about 3 inches into the dew shield. You can see this projection in my photo.

My 12 inch dew shield weighs one and a half pounds. I can shave over a pound if I make

a new one from 30 gauge aluminum sheet. A pound way out there at the end of the telescope

tube makes a huge difference. I can add a pound at the focuser end like a lot of our classics

have cast iron focusers just for this reason, I don't want to do that.

I made the cell adapter to match up to the existing countercell on the tube and used the plastic

shipping cell that came with the lens. I don't mind using a plastic cell, just keep an eye on the

lens element retaining ring because the plastic grows and shrinks a lot with temperature.

I'm sure it came with this cell for shipping purposes, I've never seen a Antares telescope with

research grade lens and a plastic cell.

Robert

 

post-50896-0-36798200-1488159173_thumb.jpg

post-50896-0-39877100-1488132169_thumb.jpg

post-50896-0-76548100-1488132205_thumb.jpg

post-50896-0-83328100-1488132228_thumb.jpg

I have an "Orbit Scope" which has a steel ring spacer between the Flint and Crown lens elements. I've replaced the ring spacer with individual foil spacers, but I find it impossible to get Newton's rings centered.  If I separate the lens elements to make an adjustment, the foil spacers move so I am starting from scratch all over again.

 

Is there a secret to making small adjustments to the spacers or is it just a matter of trial and error to get the correct alignment?

[jragsdale]

I was tasked to mount this AT66ED as a piggyback scope on an 8" LX50 that's on an MTS-SC8 mount. I got a 2" x ⅛" thick piece of aluminum and cut it to size, drilled several mounting holes to attach to the scope and to the rings. 3D printed rings and riser blocks and used brass threaded inserts and nylon thumb screws to hold the AT66 so it can be aimed at the same target simultaneously.

Attached Thumbnails

• 
• 

[clamchip]

I have an "Orbit Scope" which has a steel ring spacer between the Flint and Crown lens elements. I've replaced the ring spacer with individual foil spacers, but I find it impossible to get Newton's rings centered.  If I separate the lens elements to make an adjustment, the foil spacers move so I am starting from scratch all over again.

 

Is there a secret to making small adjustments to the spacers or is it just a matter of trial and error to get the correct alignment?

You need to attach the foil spacers, usually to the sky side of the the element closest to your eye the flint.

Finger nail polish or self adhesive foil. The spacers should be large enough so all three sit evenly and if

the retaining ring is applying even pressure newton's rings should be centered. Try checking the rings

before you tighten snug down the retainer.

I'm not so sure you should change the air space, the ring spacer I'll bet is much thicker than foil and the

lens is designed for best correction with that particular spacer thickness.

 

Robert 

Edited by clamchip, 26 November 2024 - 12:17 AM.

[Michael Covington]

Important point.  The amount of spacing (thickness of the ring) is part of the optical design.

[deSitter]

I have an "Orbit Scope" which has a steel ring spacer between the Flint and Crown lens elements. I've replaced the ring spacer with individual foil spacers, but I find it impossible to get Newton's rings centered.  If I separate the lens elements to make an adjustment, the foil spacers move so I am starting from scratch all over again.

 

Is there a secret to making small adjustments to the spacers or is it just a matter of trial and error to get the correct alignment?

The metal ring may be warped or pinched between the elements. Tighten the retaining ring more. Also, forget about those rings. The Airy pattern at focus is what you want to see nice and symmetrical.

 

As mentioned above, foil spacers not an option. Needs the thicker spacing. I use adhesive backed foil. It's 0.1mm. You can get this is rolls for HVAC or in sheets from a craft store.

 

-drl

[clamchip]

I built my new dew shield today.

The aluminum pipe with snap-lock came from a HVAC supply. It's 6 inch and I made it one and a half

times the diameter making it 9 inches long. It looks like a paint can, maybe it will be better looking once

I paint it. This is a difficult scope to improve the looks, the objective cell is not very stylish.

It accomplished what I was after, moving the OTA balance point closer to the center of the tube by

reducing the dew shield weight by a pound. Most sheet metal shops have a Snaplock machine and

can make a dew shield any size you want. Bring candy for the counter sales person.

Today I was doing a bit of observing around the valley because the see was excellent. When its cloudy

and the ground and air are the same temp I can go to very high power. The shortest eyepiece I have

in my shop right now is 5mm and in this telescope that is 300 power, still reasonably bright at that

power and very very sharp. I noticed today on a cloudy day there's quite a big difference between a 3.5"

and a 4 inch, physically not much difference but a fairly substantial difference in the eyepiece.

Robert

 

Edited by clamchip, 26 November 2024 - 07:54 PM.

[jgraham]

I added an addition heavy-duty mounting option for my 1969 Questar Standard...

 

 

The Questar is mounted on a classic Celestron wedge which in turn is mounted on a Meade standard field tripod. This makes it easy to adjust the height and to level the wedge which makes it easier to align the setting circles. This configuration is so stable I can rest my hands on the mount without seeing any shakes in the view. Power is provided by a small lithium-ion battery. I ran this for about 11 hours and there was still over half charge available on the battery.

 

 

[jgraham]

Today I swapped out some of the bolts for knobs to make it easier to adjust the wedge without needing tools...

 

 

If you look closely, you can also see my simple fix for a slipping dew shield. I wrap a narrow band of Velcro around the tube with the dew shield extended. This is the thin, lightweight Velcro that is usually used to bundle cables. When the dew shield is retracted and stowed, I wrap the strap around the dew shield. It's pretty unobtrusive.

 

[Orion68]

The individual spacers on my Unitron 114 were degraded and I was able to successfully replace them and get Newton's rings centered.

 

Sounds like I might be better off using the original spacer ring with the Orbit Scope, It is thicker than the foil spacers. I'll go that route.

[kjkrum]

I'm not so sure you should change the air space, the ring spacer I'll bet is much thicker than foil and the

lens is designed for best correction with that particular spacer thickness.

I played around with this (and continue to do so) with some cheapo achros. One of them was a moderately terrible GSkyer around 90mm f/7. I found I could minimize color fringing on the Moon by increasing the spacing a lot, like 2 mm. At the time I didn't know about the test where you minimize spherical aberration by creating an artificial center obstruction and comparing the apparent size of the obstruction with star tests the same distance inside and outside of focus. I'm inspired to get it out again and see if minimizing CA also minimizes SA. I've read that it often doesn't. Magically good achros may be those with just the right combination of glass types and lens figure where CA and SA are both minimized with the same spacing. Designing for this is one thing, but everything has tolerances and you'll find gems and lemons.

Edited by kjkrum, 29 November 2024 - 02:57 PM.

[ErnH2O]

I put together this Mighty Mite from my new Sears 6345's guide scope.

This is the 3rd 6345 I've owned and I really hope I hang on to this one because I really like the model.

I think its amazing I've owned so many of them. The only thing it could be is Sears is saying 'Thank You Robert' for

all the millions of pennies' I spent at the candy counter over the years.

I've got a lot to do to the main telescope and I thought I would do a little 40mm astronomy with this spectacular

40 x 500 f/12.5 guide scope.

I'm very lucky a few of my favorite eyepieces just focus with a hybrid prism. Not that I wouldn't mind using the .965's

in the kit, you know how it is with eyepieces, we all have our favorites.

You can get just as happily lost with a 40mm as you can with a 400mm, why not give your back a vacation!

Robert

 

Yep yep. The 40mm guide scope is a marvel on its own.

Ern

[Kitfox]

Am I the only one not quite ready for winter?  This should have been done in those warm nights under the summer Milky Way, but, alas, nothing ever happens that way.  Polar aligning the Losmandy Titan in advance of that big, off-white tube behind it getting perched up top:

 

 

 

The featherweight Tinsley will have to wait until tomorrow afternoon to be hoisted up.  Had to move the diminutive Vixen VSD100 (EAA setup and awesome SharpCap polar alignment scope) over to the AP1200 to align it, as well, and the WINTER Milky Way was throwing way too much wind chill my way!  My muscle (read: 15 yo son) was having none of this cold snap, so tomorrow afternoon, it is.  

[deSitter]

Am I the only one not quite ready for winter?  This should have been done in those warm nights under the summer Milky Way, but, alas, nothing ever happens that way.  Polar aligning the Losmandy Titan in advance of that big, off-white tube behind it getting perched up top:

 

IMG_0652.jpeg

 

IMG_0651.jpeg

 

The featherweight Tinsley will have to wait until tomorrow afternoon to be hoisted up.  Had to move the diminutive Vixen VSD100 (EAA setup and awesome SharpCap polar alignment scope) over to the AP1200 to align it, as well, and the WINTER Milky Way was throwing way too much wind chill my way!  My muscle (read: 15 yo son) was having none of this cold snap, so tomorrow afternoon, it is.  

I hate winter but Mars demands some gumption. It's winter there too

 

-drl

[CHASLX200]

Never any more winters in FL.

[ngc4910]

I recently bought an old Japanese Celestron 1.25 inch prism diagonal; I already had another one of those, but wanted a separate one for my C5.

 

I noticed only a bit too late a small scratch on one of the prism faces, but it's outside of the illuminated field for most of my eyepieces, so I decided not to be bothered by it. But, a small defect like this means that I feel less protective of the 'original state', and decided to blacken the prism edges, and re-apply some flat black paint to the 1.25 inch nose piece.

 

For the nose piece, I applied 4 very thin coats of flat black chalkboard spray paint, which results in a somewhat more textured and substantially less reflective finish than the original "factory" surface. Admittedly, I had four goes at this until I was satisfied with the result, and completely stripped the paint in between attempts. A single coat or two thicker coats dried to a very smooth finish that reflected too much light for my taste at low angles of incidence.

 

I left the second prism untouched, but did re-blacken the 1.25 inch nose piece as well once I had settled on the 4-thin-coats procedure.

 

Below, images takes through the eyepiece barrels; at the top, the diagonal with "untouched" prism; below: the diagonal with blackened edges. The sun shines straight into the nose piece, right outside the field of view of the camera. With that much contrast, my flat black nose piece unfortunately seem rather reflective! Still, much better than the beaten up factory finish. Overall, the diagonal with blackened edges appears substantially darker inside. I did not apply any paint to the sharp edge between "side" and hypotenuse, those now show as a white "stripes"  when illuminated by light among the darker prism sides.

 

(no paint applied to prism edges)

 

(prism edges blackened)

 

 

[deSitter]

I recently bought an old Japanese Celestron 1.25 inch prism diagonal; I already had another one of those, but wanted a separate one for my C5.

 

I noticed only a bit too late a small scratch on one of the prism faces, but it's outside of the illuminated field for most of my eyepieces, so I decided not to be bothered by it. But, a small defect like this means that I feel less protective of the 'original state', and decided to blacken the prism edges, and re-apply some flat black paint to the 1.25 inch nose piece.

 

For the nose piece, I applied 4 very thin coats of flat black chalkboard spray paint, which results in a somewhat more textured and substantially less reflective finish than the original "factory" surface. Admittedly, I had four goes at this until I was satisfied with the result, and completely stripped the paint in between attempts. A single coat or two thicker coats dried to a very smooth finish that reflected too much light for my taste at low angles of incidence.

 

I left the second prism untouched, but did re-blacken the 1.25 inch nose piece as well once I had settled on the 4-thin-coats procedure.

 

Below, images takes through the eyepiece barrels; at the top, the diagonal with "untouched" prism; below: the diagonal with blackened edges. The sun shines straight into the nose piece, right outside the field of view of the camera. With that much contrast, my flat black nose piece unfortunately seem rather reflective! Still, much better than the beaten up factory finish. Overall, the diagonal with blackened edges appears substantially darker inside. I did not apply any paint to the sharp edge between "side" and hypotenuse, those now show as a white "stripes"  when illuminated by light among the darker prism sides.

 

22.jpeg

(no paint applied to prism edges)

 

11.jpeg

(prism edges blackened)

Blackening edges is mostly a waste of effort. But flocking the tubes when they are not knife-edge threaded makes a real difference. This is way too reflective! Paint does not cut it. Only that Black 2.0 super-expensive paint is even worth considering. A small tube of flock paper formed into a cylinder will make a huge difference.

 

-drl

[ngc4910]

 This is way too reflective! Paint does not cut it. Only that Black 2.0 super-expensive paint is even worth considering. A small tube of flock paper formed into a cylinder will make a huge difference.

Thanks for your feedback! I have not considered flocking as I'd be worried of the material protruding too much into the illuminated field, and potentially absorbing moisture over night. That said, I agree that flocking is much darker than all paints I have seen myself.

 

Below a picture of the factory finish of a Televue Plossl, vs the 4 thin spray coats on the diagonal. Given that the diagonal barrel is not threaded, I was quite pleased to find that the painted surface does appear to be somewhat less reflective than whatever Televue uses in their Plossls (which to me seemed sufficient so far; these are my most-used eyepieces).

 

[deSitter]

Thanks for your feedback! I have not considered flocking as I'd be worried of the material protruding too much into the illuminated field, and potentially absorbing moisture over night. That said, I agree that flocking is much darker than all paints I have seen myself.

 

Below a picture of the factory finish of a Televue Plossl, vs the 4 thin spray coats on the diagonal. Given that the diagonal barrel is not threaded, I was quite pleased to find that the painted surface does appear to be somewhat less reflective than whatever Televue uses in their Plossls (which to me seemed sufficient so far; these are my most-used eyepieces).

 

33.jpeg

If done carefully the flock cylinder will stay put by friction alone and can be easily remade if necessary. Generally I make them just tight enough that the edges of the rolled up cylinder butt up against each other and make a tight fit. Start a little too big and whittle it down with an Xacto knife as necessary. It should slightly resist being pushed into the tube. I've done this with large finders (no baffles needed) and long refractor drawtubes.

 

-drl

[jgraham]

This shows the underside of how I attach my Questar Standard to a vintage Celestron wedge. The hardware is a section of 1/8" x 1-1/2" aluminum flat stock from a hardware store with a 1/4-20 bolt, washer, and a star knob. Very little force is needed to hold the scope, and the flat stock serves as a stiff spring so it's pretty easy on the mount.

 

 

Enjoy!

 

[harpo80]

I bought a used Atlas EQ-G in great mechanical shape a couple of weeks ago; it had the old board with RS-232 type hand controller connection.  Like so many others, it went *POP* when I powered it up the first time.  Top right in the photo is the burn.

 

First Light Optics got me a replacement board in two weeks (https://www.firstlig...usb-models.html).  It was installed Saturday and it runs flawlessly.  The new board has more modern electronics, new style power cable and hand controller connector, and USB (what I'll do with that as a non-imager I don't know yet). The mount replaces the AZ-EQ5 that is overtasked by the 8" scopes I was putting on it; the EQ-G is just so much more stable and solid.

 

Just in time for a week of clouds!  Looking forward to some planetary and lunar work once they clear.

 

Attached Thumbnails

•