Posts Made By: Mike Hosea

As I indicated before, I purchased a curved spider from 1800Destiny for my 7" f/6.7 Newt, which had a 1.3" ULS Quartz secondary in Protostar 3-vane spider. I also lowered the secondary obstruction to 1" because I wanted to try the smaller obstruction on for size. Despite the reduction in secondary size, the total obstruction increased by about 12% due to the wider vane thickness on the curved spider.

This dual change of course makes comparisons doubly difficult, and they would have been difficult enough given the amount of time required to install the new secondary and collimate. So, rather than talking about relative contrast between the two setups, let me just tell you how I like the new set up. I LIKE it. I really do. I took the scope out this evening and took a good look at Jupiter and saw some of the best views I've ever had through the scope. Again, I'm not sure how on-disk contrast compared, but the in-your-face, no-spikes view was clearly as good as any I'd had with that telescope, and it has always been a good planetary performer.

A word about the 1800Destiny spider. I ordered the smaller one, of course, for about $50 + shipping. It looked like the photo on their web site only somewhat better, actually, not as rough-cut as the picture made that one look. The paint was good and uniform, but a little gray I thought, but a quick overcoat with Krylon ultra-flat-black had that fixed up. The collimation system is simple and effective. My only concern with the design is that once you attach the secondary with RTV, removal and reinstallation of the holder from the spider may be a little bit tricky with the center bolt both loose and its Philips head inaccessible behind the secondary mirror. It may not be much of a problem, but we'll have to see when the time comes to clean the secondary. I would have appreciated smaller holes at the end of the vane, in fact just small pilot holes would have been fine with me. I was using 8x32 screws, and the holes were quite a bit larger (but I didn't measure).

The vanes themselves are, as you can see, thicker than quality straight spiders, but they aren't objectionably thick, and off-axis even the straight spiders will present a wider obstruction than their straight-on thickness. I was happy to trade a bit of obstruction for the stability, and the spider seemed quite stable and vibration free. Very likely somewhat thinner material would have sufficed, though, and I hope there are future options that will offer the same stability and freedom of vibration with somewhat thinner material.

IMO this spider is a great product and well worth $50. Some of you ATMs will realize that you could have made this yourself for $10 in parts and $100 in labor, but I think those numbers speak for themselves if what you really want is the spider rather than the experience of making it.
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Mike

I think it's good for holding tequila and whisky. ;-)
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Mike

For those with a passing interest, my 7" f/6.7 (Mark Harry primary) has been updated little by little since it was first "completed". I have just posted some new photos on my web site at

http://home1.gte.net/hosea/7f67.htm

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Mike

Looks like this is just an isolated case. The guy strolls into "town", doesn't know the customs, doesn't communicate clearly, and leaves bad feedback when it was not appropriate to leave any feedback at all. I've seen it go the same way with domestic newbies.

If anything it will make more people look at your feedback to see what the deal was, and they'll quickly figure it out. Just put it out of your mind.
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Mike

Supply and Demand. For "average" scopes supply usually exceeds demand. For AP refractors demand exceeds supply.
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Mike

I think the reasoning is based on the idea that 2mm is the MAXIMUM exit pupil at which one expects the macula to be able to resolve the smallest details present in the image. BTW, I don't know where this information comes from, but it is in the lore of amateur astronomy. Smaller exit pupils make it easier to see fine details by spreading them over more retina, but this comes at the cost of brightness per unit area on the retina, so 2mm is supposedly all the detail at maximum brightness. In practice, though, I think higher magnification helps immensely for resolving bright detail, and with DSOs that require averted vision a larger exit pupil may be preferred. Interestingly enough, I actually found ~2mm to be in a sort of no-man's land in my 10" f/5 where I was always wanting either more magnification or less. But go ahead and buy the eyepiece. Life is short. :-) -- Mike

Ed, was everybody using the exact same magnification?
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Mike

Just put on a Kineoptics HC-2 on both my 10" Teleport (an older model that came with Tom Noe's Delrin focuser) and on 7" f/6.7 Newt. I really liked the Wolanksi focusers, but the slow rate of travel (which some would see as a really good thing) and the need to keep them clean and lubed became a drag on my mind. I found myself becoming overly concerned with parfocalization. Parfocalization is a good thing, of course, but it shouldn't rule your life or anything.

These Kineoptics helical Crayford focusers have a much faster rate of turn, and if that isn't good enough, you can just push the drawtube, loosening it if need be, depending on how tight you like to keep the focuser set up.

I got mine from Tom Noe and so they are Teleport versions, which just means the drawtube is a little shorter, the focuser lock screw is an Allen head set screw, and the eyepiece thumbscrew is stainless instead of Nylon. Truth be told, I think I'm going to go back to standard lock and thumbscrews because I prefer Nylon on eyepieces and the convenience of a knurled head lock screw (I think Tom was concerned that it would be a nuisance grabbing the wrong screw from time to time, hence the Allen head set screw, and the stainless thumbscrew does LOOK better than the Nylon). Anyway, I sent Joe at Kineoptics and email, and he seems very friendly and accommodating about this.

The baseplate is particular to the Teleport, but I used the Teleport baseplate on my 7" because my focuser hole was already too wide.

I've used them in a few observing sessions already, and I am well pleased. If you're building a Newt, particularly a small one that you are trying to keep light, simple, and relatively inexpensive, these are just the ticket.
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Mike

David,

Don't know. I've owned both, but not really as planetary eyepieces. The Pentax XLs are nice, but I doubt they will do better than the Radians. The new Pentax XWs would be interesting to hear about, but, alas, the only XW report I've seen so far has been from Markus Ludes with the 40mm. With the TMB SuperMonos out, I doubt Markus has spent a lot of time with big multi-element eyepieces in his focuser assessing planetary performance, except perhaps for "grins" to see how much better the SuperMonos are.
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Mike

Perhaps he meant that there was no reason why we should have to put up with astigmatism in Newtonians, even with inexpensive primaries. Obviously a Newtonian can have astigmatism if the figure of the primary has it, or if the primary is heavily glued into a cell (an all too common cause), or if the primary or secondary are pinched. Newtonian optics need freedom to expand or contract as the temperature of the optic changes.
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Mike