Posts Made By: Ian Van Voorst

I'm sure these ideas have been tried, just wondering why they aren't more common or if anyone on this forum has made a mount like one of these. Both mounts fall into the category of ultraportable equatorials for visual use and as such are alternatives to a GEM (too heavy) or alt-az (hard to track at high power). I envision a small refractor on the mount (could work for newts as well, though the benefits would be questionable).

Mount 1: A fork mount for small refractors: Same construction as any other fork mount, but the fork is not long enough for the OTA to swing far past the zenith towards north. This could be just as simple and lightweight as the popular alt-az mounts for refractors, but could be used by anyone in mid-to-high latitudes to equatorially track planets along the ecliptic. In order to view anything in the northern sky, the mount must be turned around and used as though it was an alt-az. The whole scope and tripod could turn, or a third, simple azimuth axis could be added for this. This seems like a very simple thing to build -- why haven't I seen it before.

Mount 2: A 3 axis mount. The first 2 axes would be in the form of a mount like the Unistar. Below the Unistar-like mount is a third axis that provides an hour or 2 of tracking. This is essentially just like a Dob on a EQ platform, but much, much smaller. A company called Optical Research (or something like that) made a mount like this for a newtonian. The drawbacks would be that the mount is latitude specific and can only track for a limited amount of time before being reset.

Can anyone give an example of a mount built like one of the above?

--Ian

Most cpu fans (used for cooling mirrors) run on 12v, but can they be run off of 9v (and therefore a much smaller 9v battery). If not is there another way to avoid having something large like a power supply or lantern battery?

What about multiple fans?

--Ian

Just bought a dirt-cheap ETX 90RA to tinker with untill I get my 8" dob finished.

The star test is OK, but the scope is out of collimation.

Hmmmm... isn't collimating an ETX about like taking a hamster to the vet?

-- Ian

I'm interested in building a simple alt az mount similar to a Unistar, or Dscmount -- that is a mount for a small refractor that may be used like a dob, without slow mo controls.

How are the bearings made on these mounts? anyone made anything like this? Do you have pictures/links?

thanks,

--Ian

OK, it's raining, it's cloudy, I'm finishing up a scope and thinking about the next project... and I'm bored. I think I've memorized every single ATM web page out there.

PLEASE post some pics, somebody, anybody, lurkers... It doesn't need to be clever or unique -- maybe we've seen your scope before, but you have modified/improved or you just have a better picture. Save me from my boredom... please!

thanks,

Ian

I need a source for refractor tubes. Apogee is currently out.

I recently bought an 80mm F9.4 lens from Stellervue along with a focuser. In the ad for the lens it states that the lens and the focuser mate to a 90mm tube. The lens cell and the focuser actually have a 100mm outer diameter -- perhaps "90mm tube" means a tube that is common for a 90mm objective.

If I manage to locate a threaded 100mm tube, the whole project should be very easy.

One other issue -- the lens cell is not adjustable -- at F9.4 can I get away without adjustment?

--Ian

I am currently in the process of building a "string scope". Last night I temporarily put together the entire telescope together and tested it's ability to hold alignment using a laser collimator. There was some movement (only about a millimeter or 2) in the dot (reflected off the secondary -- I did not have the primary in place).

My question is: how much movement is allowable? The scope is an 8" F6. Does someone know offhand how tollerant the secondary tilt is in an F6 system?

The final design will likely be a bit more rigid. Also, the 1-2MM movement resulted from using a 2" Howie Glattner laser collimator which is probably about 4x the weight of my heaviest EP and the dot movement resulted from moving down to about 15 degrees elevation -- I'm not going to do any critical observing at that elevation anyway.

Any info is appreciated.

Thanks

--Ian

I recently bought a cheapo, Chinese, no-name 6" F5 Newtonian to play around with and possibly leave at my parents house to use when I visited them. I was surprised to find it had a fairly decent mirror.

I checked the website of the retailer who sold me the scope (sylvancompany) the other day and they have Newtonian mirrors sizes 4.5, 6, and 8 for 15, 34, and 90 dollars. From what I can tell from the scope I got and through some Internet research, these are neither Synta nor GSO mirrors, but from Hioptic, a company in mainland China. My good mirror might be a total anomaly and all the rest are horrible, but at this price one could take a risk or at least count on the mirror being a decent low power light bucket.

I bet the company is having a terrible time selling these (it's a specialty item) and I'll bet there are a few folks out there who could put together a nice sub-$100 scope with these.

--Ian

Anyone seen the new Hercules mount from Helix Manufacturing? Looks like a Unistar competitor, but includes dovetail for similar price. I would like to know how the motion/stability is like if anyone has seen one yet.

--Ian

Hi all,

Just finished work on my 8" F6 string scope. It is designed to fit under an airplane seat -- the collapsed scope is 9x14x14 and the two metal tubes break into three sections. The design is pretty much a knock-off of Gary Seronik's travel scope described in Sky and Tel. It is designed for "extreme" observing: NYC sidewalk astronomy, out-of-town trips, and storage in a shared 500 square foot studio apartment.

The original scope was a heavier truss scope and was designed for planetary observing and has an ultra low profile focuser and small diagonal (1.25"). Oddly enough, I find it hard to detect the vignetting, but if I was starting over I would use a larger secondary because it would make baffling easier.

Other Features:
The collimation knobs are tiny brass knurled nuts that my father brought with him from Amsterdam 50 years ago. They allow the boxes to nest and the movement of brass on steel is very smooth. The mirror cell uses a unique curved steel bands as springs(see the link below if interested).

Bungee cord virtual counterweight: still needs a little tweaking but does the job for now.

Pop-on alt bearings: two parallel pins angled up and into the mirror box hold the alt bearings on by gravity alone (see link -- the pics will make more sense). No tools, quick, works great! When not in use the bearings attach by velcro to the mirror cover.

The scope has mirror by Jerry Wilkinson which is very good. Last fall with the mirror in the previous version of this scope, I got the most stunning view of Saturn with this scope. I never thought that I could see so much detail in the rings. I was actually able to observe the Enke division (yes the division, not the minima, I know the difference and yes other experienced observers have confirmed that it is possible). I have an equatorial platform -- now I just need some planets!

more pics at:
http://f1.pg.photos.yahoo.com/ph/ianvanvoorst/album?.dir=/7c9f

--Ian