Posts Made By: Jim Richberg

When I had a computer destroyed in shipping by UPS ground some years ago, they informed me that a 6 foot vertical drop was "within spec" for their automated handling/sorting equipment. They also like to say that if your seller shipped the merchandise in the same packaging that it was sent to them in from the manufacturer, it is "used" and voids insurance. This applies even if the packaging is in mint condition, custom-form fitted, intended for re-use, etc.

I wouldn't trust anything more fragile than bricks to the tender mercies of UPS.

Jim

The only issue with using jump-start or lawn mower batteries is that they are made with thin plates inside and are designed (like car batteries) to provide relatively high amperage but only discharge ~5-10%. Running these types of batteries down can cause them to lose capacity in a relatively small number of discharge cycles. I had a 17 AH battery of this type drop to only taking a 50 percent charge in a scant four cycles. Gel cell batteries are supposed to be better at resisting this-- but the one I killed (or at least crippled) was a gel unit.

Marine/deep cycle batteries, OTOH, are designed to be run down and recharge fully-- although you can still do harm to one of these if you run it to full discharge. (Evidently some type of electrolytic scale can form on the plate.)

Marine batteries are certainly heavier, but make up for it by being virtually unkillable in my experience.

Jim

Floyd, that sounds about right. My Sonotube 16" (Meade Starfinder with 1 5/8" thick mirror) was ~180 lbs in its original condition. After numerous rebuilds and add-ons I'm certain it now tops 300 lbs. I can carry it outdoors and assemble it in three minutes, though, and the high winds I sometimes observe in don't seem to cause *any* weathervaning. Jim

Tom,
I no longer have the scope, having sold it a couple of years ago, but I had a C-8, serial # in the 9,000's. I believe the serial # was located under the corrector plate retaining ring, which was metal (Gary Hand helped me take it apart, and said that Celestron switched to plastic later in the 1970's.). It had sandcast forks and sported the enhanced optics label. I purchased it second-hand in 1977; I believe the original owner had it for ~three years before selling it to me.

I discovered the hard way that the rear cell threads on these old Celestron's are not compatible with contemporary Celestron parts-- like focal reducers or filters.

Jim

Lee,
I've cut the margin between putting the silicone in place and using the diagonal to as little as three hours with no problem. Of course, I have a safety net (cord affixed to back of mirror and duct taped to inside of diagonal holder) to prevent a catastrophic accident if the silicone does come loose, but it turns out to have cured adequately within a few hours. This was on a fairly hefty secondary too(4"), so I can't think you'll run into much problem if you need to cut your customary multi-day curing period short.
Jim

I *always* run a variable speed 120mm side mounted fan and an 80mm rear mounted one in my 16" f/4.5. I have an insulated temperature probe affixed to the side of the mirror and another probe to monitor air temperature, but in practice I don't usually bother turning the fans off even when the temperature differential is within 2 degrees. I used a sandwich of open and closed cell foam to mount each fan, which seems to have done a good enough job isolating vibrations that I consistently observed Mars @ 600X during the recent opposition whenever the seeing permitted.

This last Sunday we had truly exceptional seeing, and just for fun I decided to see how high I could push the magnification. I was able to get good views of Saturn @900X and decent ones at 1200X. I am convinced that this would not have been possible without these fans in place.

Get yourself a bigger battery so you don't have to worry about losing power during an observing session.
Jim

Dmitri,
I'd recommend hooking up with a local club that runs a mirror-making class, or find someone in your area who makes mirrors. You'll learn faster from watching someone else--assuming they know what they're doing-- and a club may already have the necessary equipment.

A club in my area offers a dedicated mirror-making workshop each year, and gets Steve Swayze to come teach it. Starting with a pre-generated curve in a Newport glass blank, I was able to make a well-polished 10" f/6.5 of > 1/10th PV wavefront in 14 hours of work. I think the cost for the blank, materials, room & board was $375.

I assume you're doing this because you want to learn, not because it is the cheapest path to a decent mirror? Unless you can hook up with some workshop like the one I used (DelMarVa Stargazers) I'm not sure how much you'll save over buying a Discovery or similar mirror in the 8" range. Still, it won't match the thrill of looking at images through a primary you ground yourself.

Jim

John,
I received unit #1 (I think), and posted my first impressions review a few threads below.

http://www.astromart.com/forums/viewpost.asp?forum_post_id=286061&poll_id=&news_id=&page=

My more definitive review, based on approximately five sessions with the unit, is posted on our club's web site:

http://www.novac.com/solar/siebertOCA.php

Bottom line, though, is that the 1.3X OCA works beautifully on the Black Night binoviewers. It is tall and somewhat ungainly, but does the job. 8O

Jim

Vars,
Yes, it took some fiddling with the T-max tuner on the SolarMax to get rid of the ghost image, but I was able to find a satisfactory position after a bit of trial and error.

Jim

Vars,
If money was not an issue-- which I take to mean you ignore the cost effectiveness of the PST (i.e., at worst nearly the perforance of a Maxscope for 1/3 the price)-- I'd probably go with a Maxscope 40/BF5, all things being equal.
The Maxscope has:
-- better baffling, which produces a darker sky,
--easier focusing (even the original helical focuser is easier to focus accurately than the knob on the PST),
--superior performance when stacked
-- and better nominal resolution, since I think that the Maxscope beats the performance of most PST's.

Things aren't always equal, of course. If you are more interested in solar prominences that surface detail, I think even Coronado concedes that the PST's broader bandwidth renders them superior instruments for that. And there are those "super PST's" like mine that beat the Maxscope on both proms and surface details. The problem is you have no way of predicting whether you'll get one of those, and we have no idea what percentage are "uber PST's" anyway. With the PST in such short supply, it would be difficult to go with the approach I've seen used on "prosumer" CCD cameras used for astro imaging where a committed buyer will purchase multiple units, test them all, and sell all but the best performer.

Jim