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!


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.


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.


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.


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.


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.


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.


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.


A hydrogen bomb detonated against your eyeball

November 28, 2013

…would deliver less energy to your retina than a supernova observed from a distance of one astronomical unit (AU; the distance from the Earth to the sun). How much less? From this XKCD What If:

Which of the following would be brighter, in terms of the amount of energy delivered to your retina:

A supernova, seen from as far away as the Sun is from the Earth, or

The detonation of a hydrogen bomb pressed against your eyeball?

Applying the physicist rule of thumb suggests that the supernova is brighter. And indeed, it is … by nine orders of magnitude.

That rocked me back on my heels. And it got me thinking: how far away would one have to be for a supernova to be only as bright as an h-bomb pressed against one’s eyeball?


Radiated energy is subject to the inverse-square law, by which intensity of radiation is inversely proportional to the square of the distance. So the answer  to my question is the square root of billion in AU, which is 31,623 AU, which is almost precisely half a light year. (BTW, Google will translate AU to light years for you!)

So if you’re close enough to a supernova that the light takes six months to reach you, it will still be like being nuked at point-blank range.

How far away from a supernova do you need to be to be safe? According to this article, even at a distance of 3000 light years, a supernova could still wreck the ozone layer of an Earth-like world.

Even more suprisingly (to me, anyway), the 1006 and 1054 supernovae apparently left detectable chemical traces on Earth, despite being 7200 and 6500 light years away, respectively. From farther down in the same article:

Gamma rays from a supernova would induce a chemical reaction in the upper atmosphere converting molecular nitrogen into nitrogen oxides…. In 2009, elevated levels of nitrate ions were found in Antarctic ice, which coincided with the 1006 and 1054 supernovae.

Amazing. The 1054 supernova is near and dear to my heart. Its visible remnant, the Crab Nebula, is also catalogued as Messier 1. I have observed it dozens of times, most notably during my nearly-annual Messier Marathons. I had no idea that it had literally left its mark on Earth.

So, here’s something to be thankful for this Thanksgiving: there are no particularly good supernova candidates close enough to Earth to pose a serious threat. All of the contenders are not massive enough yet (if they’re white dwarfs) or too far away, or won’t blow for millennia, or some combination of the above. So you can tuck in with abandon. We could still be annihilated at any moment by death from space–just ask the folks in Chelyabinsk–but it probably won’t come in form of a supernova.

Hat tip to Mike.


Observing Report: Night of the Refractors redux

November 20, 2013

From left to right: my TravelScope 70, my C102, David’s C102. When I took this picture, we hadn’t put the finders on the big scopes yet, or gotten my stand-alone GalileoScope set up yet.

This one is a little late: David DeLano and I spent the night of Sunday, November 3, observing at the Salton Sea. This is the belated observing report.

We met up at the visitor center at the headquarters campground. We rendezvoused there a little after 3:00 in the afternoon because we had some things to do before sunset, which because of the time change was coming at 4:50. The visitor center gift shop has a little astronomy section and both of us picked up a copy of the Sky Atlas for Small Telescopes and Binoculars, by Billie and David Chandler–more on that atlas another time. David also picked up a nice plasticized version of the Chandler planisphere.

Chandler Sky Atlas

After that we drove down to my favorite spot at the Sea, which is the south end of the Mecca Beach campground. A couple at another site were loading up as we were pulling in, and the left a few minutes later. After that, we were the only humans at the campsite all night long, except for someone in the late evening who pulled in, turned around, and left, all without stopping.

Our first activity was dinner at a picnic table in the shade. We split the gear and groceries like so: David supplied firewood and snacks, and I brought dinner (Subway sandwiches) and cooked breakfast (pancakes).


Even as we were eating, the second activity commenced: the exchange of hostages. As far as I can tell, David is a hot rod mechanic who happens to work on small refractors instead of cars; if that strikes you as hyperbole, just read on. Anyway, he’s way more adept at getting refractors to sing than I am, so I had brought him an unfinished Carton 60mm f/15 refractor and a couple of small objectives that I had rescued from otherwise unsalvageable garage sale scopes. To transfer into my care, David had brought a nice Celestron 2-inch star diagonal for my C102, and–most importantly–a GalileoScope that he had built and modded for me.

Galileo is Rocking Out in His Grave

The GalileoScope was created for the International Year of Astronomy in 2009, when it originally sold for $15. That was mostly down to economy of scale; now that sales have cooled, the price is up to about $50. It’s still a lot of telescope for that price. David’s GalileoScope mods have been featured here before.

The stock GalileoScope is a straight-through instrument with an f/10 objective and a push-pull focuser, which you aim by looking along some gunsight-style ridges on top of the OTA. My GS has had its tube chopped to accommodate a Stellarvue 90-degree diagonal with a helical focuser (the #D1026AF unit here, if you want one for yourself), and has a Daisy red-dot finder perched on the forward gunsight.


Above, my nicely tricked-out GalileoScope. Bottom, David’s insanely modded version–possibly the most attention anyone has ever lavished on a cheap build-it-yourself 50mm refractor.

Lest you get too jealous of my pimped-out GalileoScope, let me describe David’s own GS. He got the aftermarket f/11 objective kit, which lengthens the light path enough to allow the use of a diagonal without chopping the tube. At the back end of the scope, there’s a 2″ Crayford focuser (yes, you read that right) with a 1.25″ adapter. His diagonal also has a helical focuser for fine-tuning; in fact, in use I forgot about the Crayford and used the helical focuser exclusively. At the front end, there’s some kind of fancy RDF, sold by Cabella’s for use by hunters, with the largest eye-lens I’ve ever seen apart from the “boxy” astro-only unit-power finders, the Telrad and the Rigel Quikfinder. A set of nice rings with Delrin-tipped screws completes the instrument, and allows David to mount it coaxially with his larger scopes as possibly the most awesome luxo-finder-slash-second-instrument that I’ve ever encountered (on a small scope; the 9.5-inch refractor mounted on the 12-inch Zeiss in the Griffith Observatory probably takes the cake for larger instruments).

David’s GS really must be seen to be believed. Once on the Dinosaur Mailing List, Mickey Mortimer wrote, “Looks like it’s time to over-technicalize this previously tame post.” I can’t think of David’s GS without those words going through my mind. I wouldn’t be surprised if it is the most extensive hack anyone has done on a GS. It is definitely the most badass.

I should mention that getting both of the GalileoScopes to work as well as they do involved a lot more than just throwing some nice parts on. It required a lot of work and thought and experimentation. Happily, David documented the process and will have a guest post about his adventures in GS-hacking in the not-too-distant future. So stay tuned for that.


David’s GS mounted on his C102 as the luxury finder to end all luxury finders.

After dinner and the exchange of hostages, it was time to set up scopes. I was rolling with the C102/SV50 combo again. I also set up the TravelScope 70 just to have something different to plink around with. David set up his second tripod for my GS, and put his mod-tastic GS on his own C102, using a third tube ring to support the GS stalk and rings. This makes for an imposing setup. I studied it as intently as an American astronaut getting his first look under the hood of a Soyuz capsule. We used some antennas on a distant mountaintop to get everything aligned, and then almost immediately we were off and running.


Our first target, at 5:30, was Venus. There wasn’t much to see–basically a very bright half-circle–but checking in just feels like the right thing to do.

Next we turned to the Double Cluster and Stock 2 and spent a few enjoyable minutes tracing out the loops and chains of stars in our various instruments. Like last time, I could see the red stars in NGC 884, and if anything they were easier this time since I knew what to look for.

After that we turned south and did a big tour of the Sagittarius/Scutum area, eventually going north into Aquila and then west through Serpens to Ophiuchus. But I’m getting ahead of myself.

We started with the teapot asterism in Sagittarius, and let that guide us to M8, the Lagoon Nebula. Then we hopped up just a bit to M20 (the Trifid Nebula) and the open cluster M21. After that we took a break to hit M13 in Hercules before it sank down into the light dome over Palm Springs. We returned to Sagittarius with globs on the brain and took in M22, which I thought was a serious contender in the field of majestic globs. Then it was up to the M24 star cloud, where we got lost for a few minutes at the sight of literally thousands of stars in our eyes. Somewhere in Seeing in the Dark–and irritatingly I cannot find the passage right now–Timothy Ferris describes a swath of the sky, possibly M24, as a “wonderland of far-flung suns”. Whether he intended it for M24 or not, it’s an apt description.

At the risk of letting my current bout of refractoritis get the best of me, I must say, the view of M24 through the C102 was just breathtaking. Now, I have visited M24 before, many times. It is one of my favorite places in the sky. But I had not taken a good look at it through a decent-sized refractor under dark skies. The contrast was superb: against a jet-black background, the stars were so finely graded by brightness that I noticed rivers and shoals among them that I had never been aware of before, including a current of brighter stars running north-south and paralleling the Milky Way. Truly, this is the backbone of night.

But even in a palace, one can want for variety (or so I’ve heard), so we ventured onward. Past the open cluster M18 we came to the Swan Nebula, M17, very bright and clear and looking just like its namesake. Then farther up we found M16, the Eagle Nebula, its tendrils of glowing gas wrapped around a dense cluster of newborn stars. Then back to M24 to pick up the open clusters M25 and M23, which attend the majestic star cloud like obsequious courtiers. M25 is one of my favorites; it sits at the center of a curving arc of stars that David describes as a spiral, but that to me has always looked like a fishhook, with M25 as the bait.

After working through all of those objects with the scopes, we stopped for a binocular tour. I had along my Nikon Action 10x50s and David was rolling with his Nikon action 10x40s. I found that if I held David’s green laser pointer between two fingers of my right hand and the binoculars, I could aim the laser beam at the center of my field of view. We shared many sights over the course of the evening using this trick. For starters, we revisited all of the Sagittarius clusters and nebulae mentioned above, and picked up the little glob M28 as well.

DeLano 1 chart - wide

The asterism “DeLano 1″ next to Mu Aquilae. It is much more obvious than this Stellarium view shows, and looks more like a bright open cluster.

Then we turned north to Scutum and Aquila. Our first stop was M11, the Wild Duck cluster. Then I took a break for bathroom and snacks, and David went crazy finding new things. When I got back to the scope, I had some catching up to do: the open clusters IC 4756 in Serpens, and NGC 6633 and IC  4665 in Ophiuchus. David had also discovered something pretty that was not listed on any of our charts: a small group of bright stars just north of Mu Aquilae. So far I have not found this listed anywhere as a named object; for the heck of it we called it DeLano 1.

DeLano 1 chart 2 - narrow

A closer view of DeLano 1.

Zoom Zoom Zoom

I see that I have not mentioned what I was using for eyepieces. Thanks to the 2″ diagonal I could use my 32mm Astro-Tech Titan, which gives a wider true field than any other eyepiece I own. In the C102 it gives a magnification of 31x and a 2.2-degree true field of view, which was great for framing almost everything we looked at (the Pleiades fit with a little room to spare, even). My only other 2″ or dual-barrel EPs are the 21mm and 13mm Orion Stratus EPs, which I used infrequently Sunday night. When I wanted more power, I put in the 1.25″ adapter and my new toy, the Celestron 8-24mm zoom eyepiece.

My only previous experience with a zoom EP was a Scopetronix 7-21mm, which was pretty stinky. Zoom EPs always have wider apparent fields of view at high magnification and narrower AFOV at low magnification. That is pretty much the opposite of ideal, but physics is physics, and the comparatively narrow apparent field is tolerable as long as it doesn’t get too narrow–below about 40 degrees you feel like you’re looking through a soda straw. Unfortunately, with the Scopetronix zoom, the AFOV started at 40 degrees (at high mag) and ended up somewhere below 30, at which point the image is so small you might as well be looking through the other end of the telescope.

Happily the Celestron 8-24mm zoom has a more generous AFOV. The stated range is 40-60 degrees, and that seems about right to me. What’s not so great? It’s not parfocal across its magnification range (I don’t know how many zoom eyepieces are), so you have to refocus as you change magnification. Also, it’s a little soft at high power. Not egregiously so, but my 8.8mm ES82 is not going to be losing any sleep. On the plus side, it’s decent, convenient, and at a current street price under $55, dirt cheap.

Incidentally, this is the danger of getting a couple of high-end eyepieces: they are so sharp and so clear that when you go back to merely average EPs, the differences are immediately noticeable. It makes you spoiled.

Lyra, Cygnus, Vulpecula, and Sagitta

After I got caught up in Ophiuchus, we turned north, first to Polaris and the “Engagement Ring” asterism, and then to the Lyra/Cygnus/Sagitta area.

Naturally our first stop was Epsilon Lyrae,  the “double double” star, which was cleanly split at 125x with 8-24mm zoom. So if you’re curious about that eyepiece, there’s a point in its favor.

After that we followed my usual J-shaped path through this  region: from the Ring Nebula, M57, on past the fair-to-middlin’ glob M56 to the brilliant, contrastingly-colored double star Albireo. Like a lot of double star observers, I like doubles when they’re not too widely split, and at 31x the 32mm Titan and C102 gave perhaps the best view of Albireo I’ve ever had in a scope. After Albireo, go straight south to find Collinder 399, better known as Brocchi’s Coathanger. Southwest of the Coathanger one comes to the pair of closely-spaced, equally-bright stars that mark the feather end of the constellation Sagitta, the arrow. Halfway along the arrow a zig-zag pattern of stars leads to the faint glob M71. Then proceed along the arrow to the third bright star up from the feathers and hang a right to find M27, the Dumbbell Nebula.

The Dumbbell does a neat trick as either one’s scope or one’s sky conditions improve. From a small scope, or a big one under city lights, it looks like a bow tie. As things get better, the ends of the bow tie sprout extensions to either side, so the nebula starts to look more like an apple core. Finally the area to either side of the apple core starts to fill with nebulosity, so the nebula ends up looking like a football with a bright band–the former bow tie/apple core wrapped around its “waist”.

10-04-2008_DumbellThe football form of the nebula is obvious in most astrophotos of M27. Here’s a nice example by Rogelio Bernal Andreo (DeepSkyColors.com) that shows the different aspects in different colors: white bow tie center, red apple core extensions, blue football wings. I have seen the football before in the XT10, but I had never seen it in a small scope before Sunday night. And, to be clear, the C102 did not show the entire football. But it did definitely show the wisps of nebulosity extending out on either side of the apple core. It’s probably  best to say that M27 was halfway between  the apple core and football forms. It was missing the crisp cut-off at the edge of the football, which the XT10 will show under sufficiently dark skies. But it was still way more than I expected. I am still learning what a 4-inch scope with high contrast can do under dark skies; the answer is, “an awful lot”.

The striking appearance of M27 can in part be chalked up to excellent transparency in the early evening. Another example is that both of us could clearly make out the North American Nebula, NGC 7000, in the binoculars. My best-ever views of the nebula have been with 15×70 bins out at Owl Canyon. I have caught glimpses of it in the 50mm glasses before, but never as good as it was Sunday night. David was getting it clearly in his 40mm bins, which is pretty amazing.

We did another binocular tour in this area, hitting all of the objects listed above as well as M29, M39, the heart-shaped asterism around the bright star Sadr in the heart of Cygnus, and the wide blue/orange binocular double Omicron Cygni. This was about 8:30 PM, four hours into our 9-hour run.

This is pretty much how we proceeded for the rest of the night: pick an area, figure out some of the best and brightest objects therein, and hop our way through them. David was working off the Evening Sky Map and suggesting objects from its lists, and I was working from the PSA and rediscovering some goodies I hadn’t seen in a while. Rather than give an exhaustive list of everything else we saw, I’ll just list some highlights:

NGC 253 and NGC 288 – NGC 253 is the Silver Coin Galaxy. It’s up there with Andromeda (M31), the Whirlpool (M51), the Sombrero (M104), and Bode’s Nebulae (M81 & M82) as one of the best galaxies for northern hemisphere observers. My first view of it was in binoculars from Big Bear Lake, and under those dark mountain skies it looked as good in the 15×70 bins as a lot of galaxies look through a telescope. Mottled details is visible in even small scopes under sufficiently dark skies. While you’re in the area, might as well drop down about one eyepiece field and pick up the globular cluster NGC 288.

NGC 7789 – Here’s one I’d seen before but forgotten about. This is a nice open cluster off the tip of Cassiopeia, sandwiched between two small groups of bright stars. There are a lot of open clusters in Cassiopeia–we did a third binocular tour that encompassed NGC 457, NGC 436, M103, NGC 663, NGC 659, NGC 654, and Cr 463–but NGC 7789 might just be the best, not only for its inherent charm but for the rich surroundings in which it is set.

M37, M36, M38 – This is the famous trio of open clusters in Auriga, which are among the most popular and  most visited objects in the winter sky. The one that impressed us the most Sunday night was M37, the lowest (east-most) one. It is a dense swarm of tiny stars, which David described as “crystals”, and which to me looked like the proverbial scattering of diamonds on black velvet.

M46, M47, M93 – These open clusters in Puppis are also popular winter objects, especially the close pair of M46 and M47. I suspected the planetary nebula NGC 2438 in M46, which I first spotted at the All-Arizona Star Party back in 2010. Since then, I always look for it, and when I do spot it, I wonder how I was able to go  for so long without seeing it.

M76 – This is the Little Dumbbell Nebula in Perseus, and one of just a handful of planetary nebulae in the Messier catalogue (the others are M27, M57, and M97). As its name implies,  the Little Dumbbell is the smallest and probably least impressive of the Messier planetaries, but I’ve always had a fondness for it. Although small, it has a high surface brightness so it’s not hard to spot if you know where to look, and it is not without its charms.

Planetary nebulae illustrate why the Messier catalogue is a two-edged sword. On one hand, the Messier catalogue does include some best-of-class objects in almost every category of DSO; on the other hand, there are numerous objects in other catalogues that outshine (sometimes literally) the less impressive Messiers. For galaxies, you have things like the Silver Coin and NGC 4565 in Coma Berenices; for open clusters, look no farther than the Double Cluster in Perseus and NGC 663 and NGC 7789 in Cassiopeia; for diffuse nebulae, see the Flame Nebula (NGC 2024), the Rosette (NGC 2237), and the Christmas Tree or Cone Nebula (NGC 2264).

But planetary nebulae get especially short shrift; a quick-and-dirty list of impressive non-Messier planetaries in northern skies includes the Cat’s Eye (NGC 6543), the Eskimo (NGC 2392), the Saturn (NGC 7009), the Ghost of Jupiter (NGC 3242), and the Blinking Planetary (NGC  6826). This is not because Messier had anything against planetaries but because his catalogue was discovered rather than assembled post-hoc, and discovery is always a haphazard process. Still, we are not discovering these things for the first time, and with their often high surface brightness and charming array of forms, planetary nebulae are great targets for beginning and city-bound observers.

By 2:00 AM we were winding down, and so were the skies. A cloud mass that had been hovering over Palm Springs started to send forth offspring, and the haze near the horizon was getting worse. A bright star in Leo that I just couldn’t place turned out to be Mars. We had one last look at the Double Cluster and called it a night.

It was one of the most fruitful observing runs I’ve ever had. By my count, we looked at:

  • 49 Messiers
  • 20 NGC, IC, Collinder, etc., objects
  • 4 double stars (counting Epsilon Lyrae only once)
  • 4 asterisms (DeLano 1, the Engagement Ring around Polaris, the Heart around Sadr, and Kemble’s Cascade)
  • 3 planets (Venus, Jupiter, Mars)

So about 80 things in the sky, not counting the numerous shooting stars, which we noted every few minutes all night long. That is by far the most things I’ve seen in one evening when I wasn’t doing a Messier Marathon. But we weren’t rushing or trying to get through a ton of objects, we were just basically out for a spin, and if you cruise around the sky for 9 hours, you are going to end up seeing a lot.


I came away from the evening with a couple of firm directions for future observing.

First, I don’t think I logged anything that I hadn’t seen before (DeLano 1 excepted!), but I saw a lot of stuff that I had forgotten about, like NGC 7789. Most of these were things that I had visited in the course of doing one or another Astronomical League observing program. That’s great because those programs have helped me to learn the sky, and they’ve introduced me to a lot of wonderful objects that I hadn’t seen before. But now that I know the sky, I need to go back and re-observe those things and spend a little more time with them. This is especially true of the many beautiful clusters on the Deep Sky Binocular observing list–I am ashamed to say that there are many of those that I still have not visited with a telescope. So even my terra cognita holds some wonderful things waiting to be rediscovered.

Second, I need to go south (in the sky)! Here’s some relevant math: the Salton Sea campgrounds are at about 33 degrees north latitude. That means that Polaris is 33 degrees above the northern horizon, the celestial equator is 57 degrees above the southern horizon, and with no intervening landforms or atmosphere I should be able to see down to -57 degrees declination when I look south. Now, in practice the near-horizon haze makes the last few degrees pretty worthless. But I have seen the globular cluster Omega Centauri with my naked eyes from the Salton Sea. At -47 degrees declination, it never gets more than 10 degrees from the horizon. If it’s naked-eye visible that low under good conditions, then binoculars and telescopes will reveal much more at the same declination, and maybe even a little lower.

In practice, I have explored almost none of that southern expanse. I am used to thinking of the Silver Coin galaxy as a far southern object, but at -25 degrees it culminates a full 32 degrees above the horizon–more than a third of the way to the zenith! Except for sighting Omega Centauri a couple of times, I have not deliberately gone south of about -30 degrees declination (and I’ve only gotten there in the area around the “tail end” of Canis Major), which leaves a LOT of unexplored sky out there. I was fortunate to get to see most of the best of the southern hemisphere sky when I was in Uruguay in 2010 and it was amazing. Much of what I saw there is visible from here, I just haven’t looked. I need to fix that.


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