Posts Made By: Doug Scobel

What is the NGC designation for Caldwell 64? I don't know if many of us use the Caldwell designations.

Personally, I really like M35, with NGC 2158 in the same field. The contrast between the two really gives you a visual impression of their relative distances.

Thanks,
Doug

Jeremy, if you’re dealing with a sphere with a TDE, then there are two approaches you can take.

The first is to work at the COC of the main mirror and plane the whole thing down to the level of the extreme edge. That’s I think what your currently doing, but that’s a lot of glass to remove, so it’s gonna be slow.

The second approach is to move the knife away from the mirror, until the edge and center now appear to be at the same level. Now the bulk of the glass to remove is concentrated at the outer zones, up to but not including the edge. I think the zig-zag stroke with accentuated pressure (not too much) towards the edge of the tool that Norman described works this way. Should be faster, but it will be more difficult to maintain a sphere and you may have to do some additional correcting later.

Either way is OK, it’s just going to take some time. And yes, it is important to get the edge right first, then go after the rest of the figure.

Good luck!

DS

Yes, Chris, this is common for newts on an equatorial. The problem is indeed because you have the focuser, eyepiece, and probably a finder hanging off one side of the tube. In some positions (let’s say horizontally) it’s balanced, but then point the thing up and not it’s not – the weight of those components pulls it over. You can either add a counterweight to the opposite side of the tube, or increase the friction in your mounting.

Happens all the time with my 8-inch f/8, now that I’ve added a 9x50 finder. I’m contemplating installing some kind of counterweight.

Doug Scobel

If you read Orion's description of their Expanse eyepieces, you will see that they are not fully multi-coated. Meaning some air-to-glass surfaces are multi-coated, some (probably most) are not. It's a conscious trade off in favor of low price that they admit to.

I would expect to see ghosting in all FLs. My guess is the 6mm just happens to be worse.

Regards,
Doug

Exactly the question I've been trying to answer. I've never cared a whole lot about eye relief until last year's Mars opposition when I started sketching at the eyepiece. I needed my glasses in order to sketch, but had to take them off to look through the eyepiece. Glasses on. Glasses off. Glasses on. Glasses off. It got really old after a while. I've since picked up a couple Radians (4mm & 5mm) off AM, which are nice and sharp (although with some false color off axis), but pricey even used. Lately I've been looking for a high quality but lower priced alternative (if it exists) in the 7-8mm range. In particular, I'm wondering about the Orion Epic-ED 7.5mm, and the Siebert Ultra Superwide 7mm.

Doug Scobel

Ditto what Tom and Warren said. As an experiment, I made a copy of the "after" photo to try to brighten it to match the before pic more closely. Lo and behold, if you look inside the tube in my brightened picture, the velvet part looks brighter than the old flat black portion further inside!

My guess is that it's the flash that's making it look brighter. The individual velvet fibers are probably somewhat shiny, and you're getting minute but numerous specular reflections off each one, making it look brighter. I would think that such photo comparisons ought to be done outside, out of direct sunlight, and without flash. Guy, any way you can take another shot of it like I described?

Best regards,
Doug

Leif, I would think a good, slow-curing epoxy would work well. But not if you want to disassemble it some day!

Doug Scobel

I agree with you, Tom. The only time I've been able to observe it was at the 1998 Texas Star Party (I live in Michigan - and don't tell me about cold winter nights!). In my 13.1" at 215x (7mm Nagler) I recall seeing nothing but stars across the entire field! Definitely one of the most incredible sights I've ever seen.

Doug

Stephen, I'm one of the folks buying up the Radians on AM. Over the past few months I've picked up a 4mm, 5mm, and 14mm. I love them all.

I compared the 4mm with my 4.8mm Nagler in my 8-inch f/8 during the Mars opposition and found:
- The Radian was slightly sharper, right out to the edge
- The Radian had less distortion. Mars had a distinctly out-of-round appearance near the edge in the Nagler, but was perfectly round in the Radian.
- No ghosting in either.
- Some false color in the Radian when my eye was not centered in the exit pupil correctly. Not possible in the Nagler because of the short eye relief, but with the Radian the eye lens is large even in short FLs, so it's harder to keep your eye centered. Setting the sliding sleeve helps.

Ditto the 5mm.

I also compared the 14mm with a 13mm Nagler (type 1) with in my 13" f/4.5. Again, the Radian was sharper.

Perhaps the new Naglers (Type 5, Type 6, etc.) are better, but eye relief is still a problem for me in the short FLs. So I've since sold both Naglers and kept the Radians. Right now I'm saving my pennies for a 6mm and maybe a 10.

Best regards,
Doug Scobel

All three of mine are made in Taiwan R.O.C. also.