Posts Made By: dan hilts

Typically there would have been some in focus for the original configuration to allow for the use of erecting prisms and barlows. This allowance may have been quite small but then again you may pick up 25-30mm or more here. This would give you about 115-120mm extra path length to use with a bino viewer. It may be enough for your bino viewer. Don't forget to include a diagonal in your path length calculations.

You can use a hack saw if necessary to cut the tube. Aluminum is not difficult to work with. Put a ring of masking tape around the tube to mark the end postion for the cut. Adjust it until it is nice and straight. (You can measure with a ruler from the existing edge to the masking tape.) Then put several layers of paper on the tube to protect the finish. Don't bother to protect the part you are going to cut off. Stuff something (an old rag or tissue paper will work) into the tube to keep metal filings and bits from getting into the tube. They are a pain to get out. Assemble some sort of a vee block to hold the tube and cut away. I have found it helpful to make a cut all the way around with going all the way through the metal. This provides a good guide for the final cut. Don't allow yourself to get too close to the edge of the tape. Cleanthe cut edge right up to the tape with a file and you are done. You can use a square to check the edge to see how accurate it is or you can simply stand the tube up on a flat surface and gently rotate it. You can tell by the way the tube leans where you need to file a little more off.

Note that if you cut the tube you probably won't be able to use a barlow with your binoviewer.
good luck with your project,
dan

Tom,

Nice job! It's a great looking scope. I'd sure be proud if I had made it.

enjoy,
dan

I have one of the Apogee zooms, 7-21mm, supposedly a Nikon repackaged. Optically it is just fine, particularly at the 8mm end where it has a wider FOV. There are no ghosting issues or lateral colour problems. I have to refocus ever so slightly when zooming.

But.... I rarely if ever use it. The low power views are uninspiring due to the restricted FOV so I don't like it for that. I tended to locate a target and zoom in right away. Once I realized that I quit using it. Your friend may be better off with a couple of well chosen inexpensive plossls like the Orion Sirius or GSOs. Particularly for starting out. The narrow FOV at low power won't help him find things.

dan

Hi Judson,

I have a 120mm F12.5 achromat and I use a MV-1 almost permanently mounted in my diagonal. I think it helps for Jupiter and Saturn,

I also have a Contrast Booster. I don't like the green tinge it imparts on everything. I also don't think it does that much. I did see some craterlets in Plato a little easier with it but not enough that I would recommend you run out and get one. I don't think it did anything for Mars or Jupiter. Others may feel differently.

dan

You could always replace the foils with postage stamp material. It is self adhesive and easy to obtain.

good luck,
dan

Nicely done. Does it come in any other colours?

dan

Bruce,

I don't recall ever seeing both sides of a foil spacer with adhesive. I can imagine if it was done there might be a time when you would have to pry the elements apart.

Once a lens is assembled, a little cellophane tape spaced around the edge will go a long way to reduce movement of the glasses. These don't need to cover the entire edge. Three strips about 1" long are adequate for a 4-6" lens. The lens can then be handled to get it securely into the cell.

dan

I think Herbert has nailed it for you. Here's a quick clip from Cartes Du Ciel. It Shows Mizar as a double but not cleanly split.

What you have heard is true. Inexpensive wide field eyepieces don't perform very well in fast scopes. Many of them are actually very, very poor. If you can, try before you buy.

The 24mm Pan is a nice eyepiece and provides 68 degree view. It will work in fast scopes. Not as wide a field as a Nagler but very nice views just the same. Still, it will cost over $200 even for a used one. It will be about 50X in your scope and provide a 5mm exit pupil.

A run of the mill 26mm Plossl will give a slightly narrower view at 45X. A 32mm Plossl will give the same view as the 24 Pan but at much less magnification and a wider exit pupil. You can expect to see some bloating and astigmatism on stars at the edge of field in the Plossls when used in a fast scope. Low power yes, but not wide field.


good luck,
dan

ED refers to a family of glass types that have extra-low dispersion when compared to the normal glass types. Use of these glasses can help to reduce secondary spectrum (color) in lenses. Naturally, these glasses cost more than the usual glass types.

You hear it a lot because some manufacturers use the ED term to differentiate their scopes from the run of the mill achromats. Typically, the ED scopes do have less color but it is not guaranteed. There are a lot of other factors that contribute to the lens performance.

hope this helps,
dan