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A birthday observing run at the Webb Schools Hefner Observatory

June 16, 2014
Spiral galaxy M81

Spiral galaxy M81

My birthday was June 3. That evening, fellow PVAA member Steve Sittig invited me up to the Hefner Observatory at the Webb Schools in north Claremont. Steve teaches science at the Webb Schools, and he has a particular interest in physics and astronomy. The dome at the Hefner Observatory houses an orange-tube C14 Schmidt-Cassegrain. Observing with us were two other Webb faculty members, Andy Farke (paleontologist, blogger) and science teacher Andrew Hamilton. Andrew Hamilton had brought along his DLSR, a Sony Alpha33—this would turn out to be important.

Starburst galaxy M82

Starburst galaxy M82

We got started a little after 9:00 PM with a look at Jupiter, which was low in the west. We noticed right away that the seeing was pretty darned good. We went on to the waxing crescent moon and then Mars and Saturn. After that we turned to the deep sky. M81 and M82 looked great, so we hooked up Andrew’s DSLR and attempted some photography. We didn’t have a remote shutter or computer control, so we were using only the camera’s native controls, and assessing the results on the LCD screen.

Planetary nebula M57, the Ring Nebula

Planetary nebula M57, the Ring Nebula

After the galaxies, we went on to the Ring Nebula, M57, and then the Great Globular Cluster in Hercules, M13. Even with the 30-second exposures that the camera was natively limited to, we were getting very respectable images. I am including a few here.

M13, the Great Globular Cluster in Hercules

M13, the Great Globular Cluster in Hercules

Our results were pretty primitive compared to what people can do with dedicated astro cameras and post-processing, but we still had a grand time, and the process was sufficiently rewarding that we stayed out until almost two in the morning. All in all, a pretty darned good birthday present. Hopefully we’ll be able to reconvene and shoot some more this summer. I’ll keep you posted.

Many thanks to Andrew Hamilton for permission to post these photos.

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Earth-moon distance and the diameters of the planets

June 15, 2014

A few days ago Mike sent me this:

Earth-moon distance and planetary diameters

I was surprised to see so many people calling BS on this–it’s simple enough to double-check. So I did. Here are the results.

Mean radii in km, from Wikipedia:

  • Mercury – 2400
  • Venus – 6100
  • Mars – 3400
  • Jupiter – 69,900
  • Saturn – 58,200
  • Uranus – 25,400
  • Neptune – 24,600
  • Total – 190,000

Doubled, to convert to diameters – 380,000 km

Average Earth-moon distance, also from Wikipedia: 384,000 km.

Yep, this checks out. With the proviso that the Earth-moon distance actually varies from 363,000 to 405,000 km, so sometimes you’d have to leave out Mars and Venus, and other times you’d have to clone them to fill the extra space.

If you want a remarkable coincidence, the moon formed maybe only 10,000 miles from Earth and has been gradually receding ever since. So we are living in the tiny slice of Earth history when the moon is at just the right distance to appear the same relative size as the sun, and thus produce total eclipses as we know them. Annular eclipses have only been around for a few tens of millions of years, and in another few tens of millions of years, they’re all we’ll ever get, because the moon will be too distant to completely block the sun.

Anyway, after I sent Mike this reply, he said, “That is a whole lot of awesome, which clearly ought to be a 10MA post”. And now it is.

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Guest post: David DeLano’s ultimate Galileoscope quest, Part 5 – SCT focuser notes

March 15, 2014

Well, our long journey is at an end (for now!). No new pictures, just some notes on how long the various bits are, should you want to add an SCT focuser to your GS (or just about anything else). For previous posts in this series, go here. Thanks, David!

IMG_1242

Yes, that is a 2-inch focuser on David’s Galileoscope. Why do you ask?

SCT Focuser – 90mm
Low Profile 2″ – 1.25″ adapter – 10mm
Tele Vue Low Profile SCT adapter – 38mm
SCT M-M – 10mm

For F/11 objective, need something close to 75mm + 50mm = 125mm
Above parts are 90mm + 10mm + 38mm + 10mm = 138mm
Need to cut down 23mm, though 20mm might be enough.

Could use a zero clearance 2″ – 1.25″ adapter or negative adapter (ScopeStuff) (negative won’t work, since the diag won’t slide into it).

From Agena

SCT Focuser – 90mm
Low Profile 2″ – 1.25″ adapter – 1mm
TV Low Profile SCT adapter – 40mm (probably a better figure than OPT)
SCT M-M – 1mm

Total – 90mm + 1mm + 40mm + 1mm = 132mm (5-7mm too much)

However……since not using the SV helical, there might be gain on the diag EP end.

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Guest post: David DeLano’s ultimate Galileoscope quest, Part 4 – The GS F11 SCT GS to end all GS

March 9, 2014

The moment you’ve all been waiting for–I would be shocked if anyone, anywhere, ever, has put this much time, thought, experimentation, and additional gear into their GS. But having used it in the field, I can tell you that David’s monster GS is both a potent observing tool and a real pleasure to use. To see how David got from the stock GS to this, see the previous posts in this series.

GS F11 SCT

There is actually one other way to solve the Galileoscope focal length issue. When the Learning Encounters site (http://www.leosciencelab.com/ [not linked here because there is nowhere to go--MW]) was functional, they carried a diagonal kit, with which you could construct your own diagonal to go with your Gallileoscope. Part of the kit was a new, F11, objective. With this longer focal length objective, a diagonal will work in the GS without shortening it. This is the ideal solution, but it is likely very difficult to find one at this point. I had modified my daughter’s GS with this kit, and it worked perfectly well with a Stellarvue diagonal w/helical focuser. I also had a spare kit, originally bought for my son, but he lost interest. So, I decided to use it for myself.

Somewhere along the way in this project I also bought a used SCT focuser off of Cloudy Nights. The SCT focuser ended up to be a lot larger than I had thought it would be. It was far to long to use the original F10 objective, but since I had the F11 objective I decided to give it a try.

I had a 2″ adapter with SCT threads from my previous experimenting. I had to buy a M-M ring to mate it to the focuser, and the first one I tried didn’t quite work. I found a second one that had a lower outer profile, and it actually nestles inside the focuser barrel so that the 2″ adapter and focuser are mated with no additional length. I tested this out, and it was almost short enough to focus, but not quite. The SCT focuser has a 2″ EP holder on it, and I used the shortest 2″ to 1.25″ adapter I could find, but was still in need of a couple mm in length. I also found that the tube was butting up against the inside of the 2″ barrel, so I shortened that a bit (and at this point it barely touches, which is the best length to have), but I was still not satisfied. I found a prism diagonal with a lower profile EP holder, but was still not quite satisfied. I found a 2″ to 1.25″ adapter at ScopeStuff that was almost zero clearance. It would be zero clearance with an EP but since I was attaching a diagonal, it added 1-2mm. ScopeStuff, however, removed the lip on the adapter for a small fee, and this gave me the focal length I desired – I can focus with my glasses on or off! The adapter attaches to the diagonal barrel with a couple of inset hex screws, which works perfectly.

I added a more than necessary red dot finder that I had bought cheap somewhere along the way. It looks like overkill, but actually helps with the balance. This scope is really too much for a finder, though I did use it while observing at the Salton Sea with Matt. It will likely end up as my lightest grab and go as the mount it is attached to in the picture rides on a photo tripod, and both the scope and tripod fit into a bag together. All that is needed is an EP or two. As a finder, I had been permanently using a 32mm Plossl, but as a viewing scope I’d likely take along a couple of other EPs to use.

Modded GS compared to GS F11 SCT

Side by side with Matt’s modded GS you can see that it is about 50mm longer, which is what the F11 objective gives you. The SCT focuser makes it look even more massive, but it still is a GS at heart.

And also to give some comparison, here are, top to bottom, the SCT set, Matt’s set, and the ABS part, so you can see how much focal length each adds.

attachment comparison

I think I’ve covered everything. If you are still reading this, I hope you enjoyed the ride. If you have a Galileoscope kit, I hope that I have inspired you to turn it into a usable scope or finder. If you have questions, please post them to the blog comments, and I’ll try to clarify.

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Guest post: David DeLano’s ultimate Galileoscope quest, Part 3 – The Difficult Solutions

March 2, 2014

The third installment in David DeLano’s GS-hack-a-thon guest post series. For the rest of the series, click here.

To make the Galileoscope really useful you need to have a better way to focus it, and need to be able to use a diagonal with it, for comfort of viewing. These are difficult problems to solve, but hopefully the information given here will resolve these issues in a relatively easy fashion. I’ll give a little bit of the process I went through to come to a usable solution, to help others come up with their own solutions. At the end, I’ll give what should be an off-the-shelf solution, though I have not used it myself.

First, the focus issue – the only reasonable solution is to find a helical focuser, though in the next post I’ll show another possible solution. When I first started looking for a helical focuser, they were difficult to find, at least at a reasonable price. I eventually found a diagonal with a helical focuser at Stellarvue, but only by sending them an email and asking if they had any available standalone, as they packaged it with one of their finders. Now, however, I see that they have them on their web site, so hopefully they will remain available for anyone wanting to mod their GS.

You might ask, why not just use the diagonal with the helical focuser with a Barlow lens attached, and not have to mod anything. Well, I tried this. It was a bit baffling at first, and I could not get the focus to really do anything. Then it occurred to me…by lengthening the distance between the Barlow lens and the EP lens, all I was doing was changing the magnification due to the Barlow lens. I would still need to use the push-pull focus.

StellarVue diagonal

Stellarvue diagonal, from the Stellarvue website.

I should also note that I have received two different helical focusers from Stellarvue. The original one “worked”. The newer ones have more travel, but add a bit more to the focal length, and won’t work for all cases. What this really means is, you need to find a focal length solution that takes into account this additional length.

Now on to the real mod work. The focal length needs to be shortened. I wish I could tell you how much the length needs to be shortened, but measuring the light path is not as easy as it sounds, especially through a diagonal. I should also note that this diagonal has a prism, rather than a mirror, making the measurement even more complicated. The prism does give a correct image, though, which is what you really want in a finder.

So…the tube needs to be cut. This is the most difficult part of the mod, but it isn’t impossible to do. I happen to also have woodworking as a hobby, and have a nice crosscut saw, but any saw that will cut ABS plastic and give you a straight, flat cut will work. The cut will leave a bit of a rough edge, but it can be sanded or filed smooth(er). This edge will not really be seen, so don’t sweat it much. However, the truer the cut and edge you create, the easier it will be to collimate the scope, or to at least assure that it’s close to a parallel light path. Note that I’m avoiding saying this is easy to do. I run into instructions that state something is easy or simple all the time, only to find out that it’s next to impossible to do with the tools I have. But it is a reasonable, not impossible, task.

cutoff point

I came across the place to cut the tube by experimenting. In fact, I have one tube that ended up cut too short, but I think I can give enough instructions so that others will avoid this issue. The tube itself actually gives you the spot to start, so you don’t need to measure anything. There is a baffle inside the tube at the rear. Cutting just one side or the other of this baffle is the spot to start.

Once the tube is cut at this point, the focal length is very close to where it needs to be, in order to bring a diagonal into focus. The cut will look like this, to top half being cut and the bottom half not yet modified.

Note that while doing all this work, remove the objective and keep it protected. Don’t add it back into the tube until you are ready to test the focus.

cutoff illustration

A can of compressed air comes in handy here. You will likely have ABS chips all over the place, and they tend to cling to the tube due to static electricity. Blow everything off as cleanly as possible. If you don’t, you’ll end up with whatever is left clinging to the back side of the objective. I should also note that I use the compressed air to clean dust off the objectives. Yeah, I know you aren’t supposed to do that, but it actually works a lot better than trying to clean the objective with a cloth, and let’s face it – this objective cost all of about $15. I have yet to find any scratches on mine.

Now, you have a shorter tube, but nothing to hold the tail end together, other than the O-rings, and the resulting hole is really too large for the diagonal. You could probably modify the focus tube to somehow hold the diagonal, but I could not come up with a decent solution that I was satisfied with. So I set out to find something that would fit over the newly made end of the scope.

This brings me to the GS3 mod. In searching through the ABS plumbing parts, and believe me, I bought and tried a LOT of different parts, I came across a part that I think is a 2″ to 1.5″ reducer. Note that plumbing parts measure things in several different manners, and like threads, nothing appears consistent. In any case, the part will friction fit over the end of a pipe, and thus the scope, and the other end has a threaded cap and compression ring that just happens to have in ID of 1.25″. The cap will actually tighten around the diagonal barrel quite nicely.

ABS plumbing part mod

The story could end here. I used a GS with this mod for quite some time, but there are a few issues with it, and that is what set me out to find something better. First, the focal length just barely works. I could just get it to focus, most of the time, while wearing my glasses, but not without them. Matt didn’t have any issue, though he was wearing glasses also. I probably could have cut just a bit more off the tube to give more in-focus, but only if the plumbing part would actually push on further and wasn’t at it’s limit. The tube is sloped at this point, so the more you cut off, the larger the OD. It was an iffy situation that would have rendered the scope unusable if the cut didn’t work. Also, over time, the force fit became loose and I was always having to force the end back on, sometimes in the middle of a viewing session. And, one thing that I had not considered was that the scope was poorly collimated. I verified this with a refractor collimator and I wasn’t getting near the views that I should have been getting.

2-inch adapter mod

Off to experimenting again. The breaking point was when I realized that a 2″ EP holder could be fitted over the end. This also fit more deeply onto the tube, making the cut off point more forgiving.

Now I just had to figure out what to fit onto the 2″ EP holder and make it short enough to bring the scope to focus. I started out with a 2″ extender that just happened to have a barrel that screwed off and had a 48mm thread. This is the same thread as a 2″ filter. Note that a 2″ to 1.25″ adapter usually has a filter thread on the bottom, and thus the two could be mated.

2-inch to 1-25-inch adapters

Alas, this solution was just a bit too long. However, your mileage may vary, so feel free to experiment with parts you have on hand before buying any new parts. Actually, with the lowest profile adapter that I could find, I could barely get the scope to focus, but with no leeway, so I kept looking for another solution.

In my searching, I found three different ways to mate a 2″ holder to a 1.25″ holder. There are parts with a 48mm thread, an SCT thread, and a T-thread. Some of these solutions need a Male-Male or Female-Female adapter, depending on what threads the parts have. Experiment with any of these that you might have on hand.

Note that if you can put the 2″ part completely on the scope tube, you can either mark it with a pencil, or just turn it around the tube a few times. You may not be able to get the 2″ part on all the way, in which case you’ll need to estimate how much more of the tube to remove. But, as long as you leave enough room for the 2″ part to grip, you can now cut anywhere between the baffle point and the 2″ mark. I also found that the closer you can come to the inside limit of the 2″ tube, the easier it is to keep the part square as you fasten it down. Having a 2″ part with a compression ring and two or more screws also helps.

There is actually a fourth solution, and it’s the one I ended up using for Matt’s scope. A 1.25″ to 2″ adapter will work if you have the right parts. This is an adapter that allows you to use a 2″ EP in a 1.25″ focuser, not the normal 2″ to 1.25″ adapter. My original solution was to thread a spare EP holder onto the scope end of a diagonal. But, I just happened to have this part spare after converting a prism diagonal to use a helical focuser (at one point I was able to obtain a few of the helical focus EP holders as parts, not mounted on a diagonal). You are at the mercy of the threads matching if you go this route. That was the first version. I ended up buying a prism diagonal from ScopeStuff, though, to get a shorter EP holder. This diagonal happened to also take a helical focuser (threads matched) and the scope end had a barrel that was held on via a 1.25″ filter thread. So, on Matt’s final mod, the 1.25″ to 2″ adapter was screwed directly onto the diagonal body, giving the absolute maximum amount of in-focus (minimum focal length). In fact, the focal point, at least with glass on, is about in the middle of the helical focuser, which is ideal. The 2″ mated with a 1.25″ adapter is shown beside it, so that you can see the difference, around 10mm, in the focal length.

GS Matt version

After looking at the measurements of all the parts I came across I think I have a solution that should be fairly cut and dried (note I didn’t say simple or easy). It ends up that the T-thread adapters that Agena Astro covers are the shortest I could find. I think you will still need a M-M or F-F adapter to connect them, but this only adds a mm or two. This along with the Stellarvue diagonal w/helical focuser should put you in business.

update kit

And to answer Matt’s question…..by the time you get a decent way to focus and add a RACI diagonal to an otherwise inexpensive scope, you might as well buy a RACI finder.

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Guest post: David DeLano’s ultimate Galileoscope quest, Part 2 – The Easy Solutions

February 24, 2014

Welcome to the second post in David’s series on hot-rodding a Galileoscope. The rest of the posts in the series are here.

There are several easy modifications that can be made to the Galileoscope to make it more usable. This post is going to be short, but I decided to break these off separately and document them as a group, because they do need to be documented.

Daisy finder

The first mod is to add a finder. Track down one with a 3/8″ rail. The BSA Daisy BB Gun Site works well, and is relatively inexpensive, but whatever you have on hand or can dig up will work. Fit it onto the front sight, and make sure it’s on as flat as possible. This probably means centering the sight between the screws that hold the finder to the rail. Tighten it snug, but so that it will slide back and forth. Slide it back and forth a few times, making sure to maintain the position on the sight. This will give you a bit of a groove for the rail cleats (I don’t know what else to call them) to ride in. Tighten it down a bit and repeat, a couple of times. Now tighten it as much as feasible, and it should stay firmly attached.

This next step is optional. Remove the sight, and take a nail file or a small saw and deepen the groove that you started on the sight. I highly recommend this, as it will give the finder a bit more grip and prevent it from coming loose, or tilting during use.

The Galileoscope kit does not come with a cover for the objective. It does have a nice dew shield, which also holds the two halves of the tube firmly around the objective, but no cover. I originally found that a plastic cap from a shipping tube, probably a 2″ size, fit nicely into the dew shield. However, I eventually figured out that a 70mm binocular cover is exactly the right size to go over the dew shield. The ones I use came from Agena Astro.

O-ring reminder v2

While you are still in mod mode, replace the O-rings that hold the tube together. In reality, the O-rings aren’t absolutely required, but because there is some stress in holding everything together, use the O-rings. I replaced mine with a bit of a heavier duty version measuring 1-5/8″ ID, 1-7/8″ OD, 1/8″ thick. They are a bit more difficult to install, but should hold up better over the long haul.

Be careful with the 1/4″-20 mounting nut on the bottom of the scope. If you over tighten when fastening to it, the nut will start to pull out of the tube halves, splitting them apart. This is one reason I recommend using the O-rings, as they are closer to the center of the scope. However, I highly recommend using finder rings instead. For one, if you are going to use the GS as a finder, you need to be able to align it to your telescope. Beyond that, it is a much more secure way to mount the GS. Be careful when tracking down the rings. You would think a 50mm to 60mm set of rings would work, but they are almost impossible to get over the front or rear sights, along with the block where the mount nut is located. Go with a 80mm to 90mm set, making sure that the minimum tube they can accommodate is around 55mm.

IMG_0806

I’ll add this mod for Matt. I didn’t do this, but you can also blacken the edges of the objective. I believe Matt uses a black permanent marker. This might reduce any internal reflections in the lens. (That photo is actually from my Celestron TravelScope 70 overhaul, but the procedure would be the same for the GS.–Matt)

And lastly, use a Plossl EP instead of using the ones from kit. Go ahead and make and try out the ones from the kit for the experience, but if you really want to use the GS for viewing, use a better EP. You don’t need an expensive one. Something in the 20mm to 25mm range is probably the most useful, though I have had a 4mm in the GS viewing the moon, and other than the moon moving rather quickly, it was an interesting view! The 4mm I used was from a Celestron Firstscope reflector, another nice scope to play with if you can track one down. The Plossl EP can be used in the GS without any modifications if you can put up with the push-pull focus and having no diagonal.

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Guest post: David DeLano’s ultimate Galileoscope quest, Part 1 – Introduction

February 18, 2014

I’ve been fortunate to have my electronic pen pal and sometime observing partner David DeLano contribute several guest posts in the past (sun funnel, diagonal comparo), and I wrote about one of his early Galileoscope hacks way back when this blog was only four months old. But now he’s pulled out all the stops, and written a multi-part epic explaining in detail how he evolved his stock Galileoscope into the hypertuned monster it is today. The best thing I can do at this point is shut up and get out of his way!

I have owned a Galileoscope (GS) from day one.  I’ve also been on a quest to make the GS better from day one.  I hit a stale point in the quest, though, when Matt set me off again.  I was using the GS3 (third iteration, though I’d be hard pressed to figure out what GS1 and GS2 were at this point) as a finder.  Matt was working on the question of why finders cost so much, when something like the GS could be had for half the price.  So, I was off again to make the GS better.

GS box

I don’t want to reiterate the Galileoscope history. Instead, refer to http://galileoscope.org/. Also note that there are now vendors that carry the kits, so you don’t have to buy them directly and pay shipping that increases the cost by 50%. I recently ran across them at http://www.scopestuff.com/ss_gscope.htm. There may also be some interesting additions for the GS at http://www.leosciencelab.com/, though the site appears to be down at the moment, maybe permanently, and the last time I visited the site, you couldn’t buy anything.

When I first received my GS (well, one of the Galileoscopes from a case that I bought and distributed to family and friends) I found it interesting to build, but frustrating to use. I immediately picked up on a few modifications that made it useful. There are three shortcomings to the design that needed remedied: the gun sight finder was difficult, if not impossible, to use in the dark; the focal length was too short to use a diagonal; the push-pull focusing was very frustrating to use.

GS box contents

The finder update was the simplest. A very inexpensive Daisy BB gun RDF clamps nicely to the front of the gun sight.

The focal length was relatively easy to fix, though the solution had it’s drawbacks. I bought a diagonal, a Barlow, and while I was at it, a 25mm Plossl Eye Piece, since that is what the scope kit came with, from OPT.  The Barlow needed to have a removable lens, which was removed and screwed onto the end of the diagonal. This extended the focal point into the drawtube, and gave enough in-focus to make the design work. I was up and running with a working scope, and could verify that the objectives in these scopes were very well made. In fact, during design, the objective was where most of the effort and cost went. I got lucky in that all the parts I ordered from OPT fit together. I’ve since learned that this is NOT always the case, and many of the dead ends I ran into were because threads didn’t match.

Now I had a working scope, but one that was still difficult to focus (though I think with my current level of experience I could likely make it work better). So I set out to solve the problem of focusing. I’m still on that quest for the perfect focusing solution, but I can now at least suggest some ways to solve the issue. The focusing issue is tightly coupled with the diagonal issue, and invariably lead to focal length being the issue.

GS main parts

My hope with these posts is to give an update with off-the-shelf, readily available, parts. However, with the information I share, anyone with spare parts on hand might be able to put together a workable solution. In the end, the tube halves, the dewshield, and the objective are the only parts of the kit that I used, the objective being the important part.

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