Posts Made By: David Simons

Hi Pete,

I made one from an old weighted base reading lamp. A few details are on this posting here:

https://www.astromart.com/forums/viewpost.asp?forum_post_id=229664&poll_id=&news_id=&page=

This lamp is much dimmer than it looks, and works off the 12V battery in the picture. I use it all the time now, as it illuminates a large section of the page, and is also used as a paper weight to keep the pages from turning in the wind.

David Simons

I was rummaging around through my 2004 RTMC pictures and found this one that shows the reflection of the steering flat onto the primary mirror of my 10" Reverse Newtonian (aka Porter Turret). The image is of the Moon's reflection off the famous RTMC dust that had settled on the primary. The dark spot in the center is the non-reflection of the hole in the steering flat where the image passes through to the eyepiece (see optical layout). The RTMC dust shows the small obstruction fairly easily, it is around 12%, which gives 1.2" maximum linear object size. 2" wide field ep's don't add too much here, but high power planetary images are very nice

David Simons

Here is a first rough cut at a simple alt-az mount for my C14 OTA. The Altitude bearing from pipe threads works fairly well. As one pipe unscrews, the other starts to tighten, so it actually has a fairly uniform tension. The Azimuth needs a lot more work. I'm pretty sure I will need a much more rigid base structure with a large bearing surface, ie. teflon, ebony star laminate etc. But the proof of concept is not way out of line.

My eventual plan is to use a Lumicon visual compressor to get an f5 light cone, and use low power ep's. So the setup will be used for low power, and fine critical tracking will not be as important. However quick setup is important, and the mount can be moved easily, as the base rotates and acts like a giant wheel, and the C14 is mounted by rings, so it easily comes off. I only had some rough measurements to estimate the height of the total assy., but I think it came out right. The folding chair height covers most of the altitude range, as the scope balance point is so far back.

David Simons

Here is shot of a homebrew alt-az pipe mount for the C14. Although the setup is a little shaky, my intention was to use it primarily at low powers with a focal reducer, so the shakes would not be too offensive. I tried it first with the reducer off, and used a 40mm Orion Ultrascan ep. This was giving a little less than 100X, and not quite fitting in the whole moon, (0.4 degree?), Then I tried the Lumicon Giant 3" reducer in place and found I could get a little more than 2 full moons in the 40mm Ultrascan. Maybe 1.1 degree? No vignetting on the edge. However the view was not as sharp. I also did a little reading and found out the reducer lens can give either f5, or f6 reduction. I'm thinking I must have been at the f5 setting, and maybe pushing the optical train a little hard and also missing some light, as my eye for sure does not open past 7mm. I will try out the f6 setting, and a 30mm ep. next time. The shakes in the system were dramatically reduced at the lower power, (~44x), and moving the scope around was much more forgiving. I have used this scope a number of times before, and this was the first time I had seen such a wide view from it. I'm hoping to use this on the Sagittarius region as soon as these clouds will give me a break !

Has anyone else used one of the these Giant Lumicon reducers before ?

As an aside, I also tried a Meade 18mm SW without the reducer, giving 217X on the moon, and I had forgot how sharp a C14 can be. My shaky pipe mount was almost useless at this power, but the details on the moon seemed to go on and on. I love tracing rilles and canyons, and the moons phase tonight was very favorable for such details.

David Simons

I finally did an acid test for the C14 pipe mount and brought it to our clubs "Star-B-Que" this last weekend. Here is a picture of it taken down and ready to be packed into my Camry. I had added some no-tools large eyebolts and wingnuts to attach the ring cage to the pipe supports. This came in handy when it was time to pack up at 2:30am. When I was putting it together, I got a few grins, but after about 15 minutes, I had the C14 mounted and ready to go. I had a few observers that night, as I ended up having about the biggest scope on the field except for the 24" in the observatory. I had my lowest power 40mm Ultrascan 70 degree ep. giving a little greater than 0.5 degree FOV. One fellow just sat there panning it around the Sagittarius region and kept exclaiming to his friends what he was finding. It sounded like a kid in a candy shop. I don't blame him a bit

David Simons

I have thought about getting a Giro mount from time to time to allow two OTA's to be used side by side at the same time.

But since I have been building a few pipe mounts recently, I tried to make a similar Alt-Az Giro style mount.

This pipe mount sets up fast, and any scope that can be mounted to a Losmandy plate fits right on. I just have to watch the thread un-winding to make sure the azimuth does not get too loose.

The ST150 acts like an ultimate finderscope for whatever scope goes on the other side : )

David Simons

PS, For what it's worth, I did a quick test of the two refractors, .. and the Takahashi seems to give sharper stars

I was going through some of the clusters in Cassiopeia this weekend, and when I came across NGC225, wrapped around it was a swirl of stars that to me looked like the Ying/Yang symbol.

I was using a Vixen/Orion 125x20 bino in about a mag 5+ sky, but I think 70-100mm aperture would show the swirl of stars pretty well also.


I doctored the Desktop Universe shot below a bit to show the general pattern, as there are many more stars in the eyepiece!

The Milky Way shows a lot of mottling in this area, and a low power view helps to bring it out.

David Simons

Hi Roger,

The Celestron/Vixen achromats were f10, is there any sticker or printing that says either the focal length, or f-ratio?

I had the Achro for a while, and although it gave very sharp images, the excess color after about 125X would be very noticable, especially the moon. An "ED" lens should hold up well past that.

David Simons

I finally got a chance to assemble my surplus 11" triplet lens that came off an aircraft simulation system (see bottom picture)into a tube with a focuser. The lens is reasonably square inside the tube now, but has a very short focal length of 35". I have stopped the lens down to 10", but this still gives a very steep f3.5 light cone. I looked at the moon first, and although the center of the image was sharp, the edges were a little soft. One side of the moon was reddish, while the other was greenish blue. I think I have some alignment/collimation issues. Just for fun I pointed the scope at Vega. Wow, the color on each side of the slightly elongated brilliant star was reminiscent of something you might see in the 60's. I then checked out Cassiopeia, and even with a lot of moon, many stars were visible in the 1.88 degree FOV I was using. Although the alignment is off, I think for low power viewing, the scope shows a lot of promise.

Since the lens almost fit snug inside the 12" aluminum tube I already had, I mounted it inside the tube using a set of rings to hold it in place. (white rings in the picture). But now unfortunately do not have a way to adjust the lens as the internal rings are fixed!

The focuser, however, can be moved laterally, and also tilted by adding shims. Maybe I can collimate from the focuser end only?

Anybody have some thoughts on how to collimate this beast ?

David Simons

I have finally gotten around to mounting an 11" triplet lens I have had for a couple of years that was used in a flight simulator system.

I thought about trying to adjust the 35lb 35" fl lens that I have held in place with two retaining rings, but everything is fairly close to square inside the tube and doing any kind of shimming and adjusting would be pretty scary as I would likely have to remove the lens a few times. The internal mounting rings clear aperture is 10", but this still gives an f3.5 light cone!

For collimation, I made the holes that mount the focuser end plate to the tube quite large, (they can be seen in the second picture) and tilted the end plate a little at a time until star images tightened up. This helped a lot, and now Vega focuses down to a small brilliant point. Outside of focus still shows a lot of color, but inside focus is pretty sharp now, although the Double Double smaller components were showing no sign of splitting at this low power. I have yet to do final critical alignment, as I needed just a little more adjustment range in one axis. I will try it again tonight.

For fun I pointed the scope at the rising moon, and was getting clean low power images, but things went muddy around 122X. I then stopped the lens down to 7", and everything was sharp again. This made an F5 7" refractor, and I was using a 7mm type 1 Nagler, which made a nice combination. I wanted to push this "Comet Finder" scope a little and tried an old 4mm Clave. I don't use this ep. much, but the image was still holding up sharp at 214X. Color was just starting to show. My Skywatcher 6"f5 refractor would be giving me a purple bath at this time. I think I was getting close to the limit of the lense and put in an 8mm Clave and a 2.5X Powermate for 267X, and either the seeing or the lense was setting the limit here, as I no longer would see the glimpses of greater detail, and hints of color error were starting to be more obvious.

Although I did not intend this to be a planetary scope, it's nice to know that with a little decrease in aperture, there is some capability. I have not made any baffles or flocking inside the tube yet, and I was getting a bright background, so this should make a big diffence. But I think with darker skies coming up, there should be some nice wide field viewing with this scope!

David Simons