Louis D

45 minutes ago, fozzybear said:

windex=windolene SC Johnson equiv in Europe? (glass cleaner) well I never...

The only ingredient in it that concerns me is the blue food coloring.  Hopefully, it all wipes off.

For really grungy eyepieces on old eyepieces, I've had to disassemble them, note the order and direction of each element and spacer ring, and wash the elements with dish detergent over a thick towel (in case it slips out) in the kitchen sink using my fingertips as scrub pads.  I then lay them on a dry, clean cotton cloth to dry it, giving them a light wiping to avoid spotting.  That's the only way I've found to git rid of some tough grime.

Al Nagler has recommended Windex in the past.  I've used it and it works well.

3 hours ago, vineyard said:

maybe filters are like fine wine & get better w age?

Lumicon had an issue with some of their filters oxidizing from the outside in.  There are tests of H-Beta and O-III oxidized filters on the SearchLight website showing how much they have shifted off of their emission lines.

@bomberbaz How of the field of view is visible when wearing eyeglasses in the NAV-HWs?  I would estimate about 80 degrees or so.

I assume the OP has both OTAs right now and can swap the primary mirror cells between the two before sending the original with the chipped secondary back.  I'd probably take them both out and do some critical observing with them to see if there is any difference between them first.  Perhaps one primary has a better figure than the other.

Here's a design plan for a Dob along the lines of what you want to accomplish.

Here are some instructions for building a Dob.  The structure instructions are toward at bottom under "A Dobsonian Mount".

I would try to make the trunnions as large as possible like the Bresser Dob's.  It really improves the altitude motion a great deal.  Also, try to mount the scope dead center to minimize the swing from horizon to zenith and to get the best possible balance.  This may mean adding weights somewhere for balance (likely at the top end).  There's not much reason if any to cantilever the mount backward as shown in your diagram.  Straight up and down is perfect.

Nylon chair slides can also work great for the bearing surface.  Teflon can sometimes be too slippery.  A matte to satin pebbly surface for the bearings is ideal.  Smooth glossy is actually too "sticky" in use.  It doesn't want to let go easily to track an object.  Some smooth satin surfaces will also work, depending on the material.  Think about a chair sliding on a floor with those glides on the bottom of each leg.  You can actually try out different combinations with this method.

The Dobsonian design at 8" f/5 excels when used while sitting.  You want to be bending over the telescope when viewing about 25 degrees above the horizon, typically about as low as you'll want to go.  You want to be sitting straight up when viewing at (or near) the zenith.  This is why minimizing the swing is important.  Mounting it too far back causes a large low to high swing.  That 1000mm focal length will be just about perfect if you can mount the scope's trunnion's center point about 27 to 28 inches about the ground in my experience.  I'm 5' 8", so your comfortable mount height might be higher or lower depending on your height.

Here are some examples of what I'm describing:

Seems like having multiple co-mounted scopes with dedicated cameras would be less troublesome.

Has anyone tried those new dual, tri, and quad band nebula filters intended for single shot astrophotography visually?  They're pretty expensive, but if they work under light polluted skies, they might be worth it.

2 minutes ago, andrew s said:

Yes indeed compared to an eyepiece objective design is trivial.

Regards  Andrew 

And yet actually successfully fabricating an advanced refractor objective design seems to be much more difficult and expensive.  It can't just be about the vast amount of expensive glass involved, or perhaps it is.

Very cool looking effect.  Now your scope is unique and you can ask for a premium sales price should you ever decide to sell it. 😉

1 hour ago, Don Pensack said:

There is a very slight SAEP there, too.

Yes, but I have never been able to detect it in use.

1 hour ago, Don Pensack said:

The ring at the edge extends farther into the field on the 31mm Nagler.

Naked eye, I was able to clearly see the orange/red ring, but not the other ring colors.  The camera was way more color sensitive.  I was flabbergasted when I reviewed the image.  Apparently, it's actually a ring of rainbow rather than fire, but the non-orange/red colors are harder for the human eye to detect.

Here is Ernest's post about CAEP on CN.  I've reproduced the image here:

That is the exact same version of the ES-82 30mm (mine is decloaked) that I shot my rainbow AFOV image through.

I captured the CAEP of my ES-82 30mm pretty conclusively in my 127 Mak in the following image:

I've never captured anything close to this through any of my other 50+ eyepieces.  Notice there's no chromatic smearing of the individual tick marks or numbers, so there's no classic chromatic aberration as seen in many lesser wide field eyepieces such as the Kasai Super WideView 90° 30mm below:

Notice how the tick marks and numbers nearing the edge get progressively more blue-green shifted to the left and red to the right?  Also notice how the field stop is a rainbow of colors going from reg/orange/yellow to green/blue?  These are all classic chromatic aberrations.

Compare it to the minor SAEP of my 12mm ES-92 in the 127 Mak:

Notice the thin blue line at the ES-92 field stop but no rainbow spread of light in the outer field and no spread of colors within a detail?  The ES-92 has minor SAEP, no ring of fire (CAEP) and no classic chromatic aberration, the ES-82 has CAEP but no classic SAEP or chromatic aberration and the Kasai has classic chromatic aberration but no SAEP or CAEP (it's not there in the full images, take my word on that).  @Ruud is probably correct that if the negative group were to be removed from the ES-92, it would have pronounced classic chromatic aberration.

CAEP is caused by the blue end of the spectrum being focused further away from the eye lens and the red end closer.  At the best exit pupil, you get fairly close to white, but in a very broad exit pupil circle compared to an eyepiece without CAEP.  Notice there's no rainbow effect in the ES-92's SAEP ring?  That's because all the light wavelengths from any given ray bundle are focused at the same point.

18 hours ago, Dr Strange said:

As to GOTO vs. star hopping, there are two schools of thought. One is the star hopping crowd. They range in passion and tolerance for anything other than star hopping from "Death before GOTO/Push To! You are not doing astronomy unless you star hop!" to "GOTO is a tool like any other but I would rather star hop". The same applies to GOTO or Push To users. So the first question you have to ask yourself is: Do you enjoy hunting for things more or do you enjoy looking at things or both?" The other factor in play is how bad is your light pollution. If you are in a large town or city then star hopping can be much less rewarding and much more frustrating. It can still be done but it isn't as easy as it is from a dark sky location. 

Another factor is how many alignment stars can you see at once from a single location at your observing site?  Since my trees have matured in my backyard, I have a pretty narrow wedge to the south that is clear.  I usually try to find one alignment star within that wedge for one star and roughly align on Polaris through the tree branches to my north for the second star and then do several align on objects to refine my alignment from there.

2 hours ago, Jiggy 67 said:

I would like to use them as 2 inch but I'm afraid all my filters are 1.25" so I may have to put my hand in my pocket again in the near future!!!!

You would continue to screw filters onto the bottom 1.25" thread, so no change there in 2" mode.  In 2" mode, you do have to rack your focuser out by the difference between the 1.25" shoulder and the 2" shoulder because the eyepiece is seated more deeply in 2" mode.

If you never use goto, you'll never miss it.  I did add DSCs to my Dob to find Neptune, Uranus, and some planetary nebula that had eluded me.  However, I rarely turn them on.  The only time I've found goto or tracking truly useful is when sharing the view with others.

1 hour ago, Stardaze said:

Sorry to gatecrash the OP's thread. How do the ES 92 stack up against the APM HDC's? 

I don't have the APM HDCs, but I do have both ES-92s.  The biggest difference aside from the 8° AFOV and size difference, the ES-92s are completely usable with eyeglasses while the HDCs would be somewhere around 70° to 75° AFOV with eyeglasses due to their relatively small eye lenses for their AFOV.  Edge correction is also better in the ES-92s than the HDCs by all accounts.  Only the Ethos and Nikon NAV-HW have better edge correction in that AFOV range.

I always wear eyeglasses with long eye relief eyepieces when observing due to strong astigmatism (2.0 diopters), so my eye lenses rarely need cleaning because of that barrier.  I've probably only ever cleaned the eye lenses every 5 or 10 years unless there's obvious image degradation from eye lens crud.  More often, it's my eyeglasses to blame.

Astrophography is a mighty slippery slope.  It starts out innocent enough as with your example.  The next thing you know, this is in your backyard observatory:

Remember, scratches on the objective lens of a photographic lens have almost no effect on image quality unless a bright light is in the field of view and is projected right through it.  Then you'll see flaring.

Scratches on the objective lens of an eyepiece may be very near to the focal plane (field stop) of an eyepiece and thus very easy to see.  Scratches on the eye lens of an eyepiece will cause flaring on every bright star that passes light bundles through that spot.

Just be very careful when cleaning eyepieces.  Resist the urge to clean them in the field in the dark.  Do it in a well lit, dust free area indoors.  Make sure to flick all particles off the lenses prior to cleaning them with a liquid and cloth to remove oils and sap.  Resist the urge to disassemble an eyepiece to clean the interior unless there's obvious fungus.  Rarely does anything good come of disassembly.

I would choose Pentax XW, Baader Morpheus, Tele Vue Delos, Delite, and Panoptic, Nikon NAV-SW, Vixen HR, and Takahashi TOE eyepieces.  If you want 100 degrees, probably the APM XWA HDC.

10 hours ago, Stardaze said:

Thinking either the Nagler 17T4 or maybe the ES 17 92 or 100 deg?

The NT4 17mm is very sharp, but has field curvature and some mild SAEP (kidney-beaning) when you press in enough to see the field stop.  It's hefty (heaviest of all the NT4s), but relatively compact.

The ES-92 17mm is better in every way except size and weight.  It has a wider AFOV, no field curvature, no edge of field astigmatism, no SAEP, and better eye relief for eyeglass wearers.

Below is a comparison image showing the view through several of my eyepieces in this size range.

If you can get them for between $50 and $100, they should be a good deal.  Check that the images align, look down into them to see if there is obvious fogging or mold on any of the optics.  Minor dust isn't much of an issue.  Make sure that the focus and eyepiece diopter move smoothly.  If they are near mint, you could go over $100 for them.

These were made in Japan in the 50s and early 60s.  They had oversized prisms and usually had large eye lenses.  Eye relief is tight to get the 77° AFOV.  They often employed aspherics in the eyepiece to get decent correction in the outer parts of the image.

I would contact SMark on CN for further guidance.  He is about the most knowledgeable person on these vintage binoculars on the planet.

To avoid your dome shifting between wet and dry seasons, I would want to get down below the top few feet of soil with concrete pillars unless you sit directly on bedrock.