Category Archives: Astronomy Gear

Discovery 12.5 Dobsonian: Initial Thoughts

Discovery 12.5″ at its new home – many new
deep sky explorations await!

When I poked my head out this morning I almost didn’t get up because it looked a bit foggy and there was a halo around the moon indicating a good bit of humidity in the sky… And even a few wisps of clouds. But I had not yet had a chance to look at Jupiter with the new scope so curiosity got the best of me. I was up late last night working on a list of double stars so when I went to bed I did so in all my cozy layers. All I had to do was slip on my boots, a hat and my coat. I grabbed two eyepieces and stepped out the door.

The scope and everything around it was with coated with a thick layer of frost. 19 degrees this morning but, thankfully, no wind. There were birds though, lots of chirpy birds. And a very pretty sunrise. And Jupiter which you don’t see in this picture because the gas giant was out of the range of the photo, just a pinpoint of light high in the western sky. To the untrained eye the largest planet in our solar system would have looked like a star about to fade from view in the brightening sky.

I’m glad I got up when I did because had I waited another 15 minutes I might not have found it. As it was I had just enough time to tilt the scope over and place the Tetrad’s red center point on the fading pinpoint. I was treated to the best view of Jupiter I’ve ever had. Even with the coming daylight I saw three bands of reddish clouds stretching across the white sphere of the planet. The two main bands even hinted at a bit of detail along the edges which exhibited irregularities. Even more,  the white base color of the planet turned into a gradient of a fainter red over the north and south poles. Four moons were easily visible as pinpoints of light.

For a little treat after Jupiter I swung over to the moon (top right corner of the photo) and in its current crescent stage it’s possible to see many more craters along the edge and it was a fantastic view.

This marks the 5th viewing session with the new scope. Well, new to me. It’s actually about 14 years old. Handmade by the folks at Discovery Telescopes, it was a chance find on Craig’s List. With a mirror of 12.5″ it’s only slightly larger than the Zummel’s 12″ mirror. I am not at all unhappy with the Zummel and have enjoyed it a great deal over the past three years but this was a chance at a better scope and thus a better visual experience at a good price so I went for it. Not only are the optics better but it came with an equatorial platform for tracking objects in the eyepiece. So, what are some of the differences and how does it perform?

Most importantly, the Discovery scopes are built with hand-made mirrors that are a step up from mass produced mirrors used in scopes by Zummel, Orion and others. Or so it is said. In terms of the visual experience I have to also mention that the Discovery is built using cardboard Sonotubes. Yes, cardboard. Very well painted and the Sonotube is very, very sturdy so this is not something that will bend or break easily as long as it is taken care of. But most importantly, the interior of the tube is pitch black. Unlike an unflocked metal scope that’s been painted black but appears gray this is completely black. Set this next to the Zummel on a dark night and you’d be amazed at the grayish blue glow that you see when looking down the tube of the Zummel. Look down the tube of the Discovery and it is pitch black. The only light to be seen is that being reflected back up by the primary mirror at the base of the tube.

The result of the improved mirror and the blackened tube in the eyepiece is not just noticeable but dramatic. I can’t say for certain how much of the improvement is the mirror and how much is the darker tube but I can say that in the five sessions I’ve had I am thrilled. As mentioned above, the view of Jupiter this morning was the best I’ve ever had. Did I think my views before were lacking? At the time, no. I was always very happy with them. But it is greatly improved with this scope. I’m looking forward to more viewings with darker skies and greater contrast.  I suspect that for the most part the views will only be better.

Another object I’ve viewed during four of the sessions that needs special attention is the Orion Nebula. WOW. The view with this scope is nothing short of spectacular. When viewing astronomical objects, especially nebulosity, the key is contrast which translates into increased detail. With such low light the observer is always looking for the subtle details to be found in gradients of gray and usually blueish light. So, in an object such as the Orion Nebula which is easy to see even in binoculars the details emerge as you improve your practice viewing and as you observe with better equipment. I’ve had a good bit of practice and am seeing more all the time just because I’ve been looking at it now for 3+ years with several different scopes. In some ways it’s like other visual activities that one learns in practice.

For example, as a bird watcher I’m still learning new things about birds and learning how not just identify them but to really see the details. With birds it’s everything from the shape of the beak to the colorful feather markings, the shape of it’s body, to the way the bird flies and more.

In visual astronomy practice helps one to see more details in any instrument but it also helps one notice the refined details in better instruments. If I were to look at the Orion Nebula with my 8″ scope now I would see more than I did 3 years ago when I first looked using that scope because I know how too look. I know about averted vision and about spending enough time on an object. I know more of the details and about looking at dark areas as much as the light areas. So, regardless of instrument the view is always getting better with practice and familiarity. But with the Discovery I can safely say that I am seeing an amazing amount of new detail. The increased contrast means the subtle details that would have been lacking before now stand out. Differences in color and brightness mean differences in gradient which, in the case of this particular object, means a new sense of visual depth, of dimension. Honestly, this wasn’t something I was expecting. Yes, I was hoping for a better view, better detail, but I didn’t quite understand what that would be. Now I know.

Viewing the nebula now means seeing new detail everywhere which leads to this added sense of dimension. It’s no longer a flat view. Now, I expect not all objects will benefit in the same way. In fact, I know they will not. My view of the Crab nebula is improved but not by much. It is a much dimmer object to begin with and as I understand it details only emerge with scopes larger than 16″. I can’t say that’s true but I can say that my view is largely the same with all three of the scopes I have at my disposal: 8″, 12″ and the 12.5″. In all three it is an irregular, somewhat spherical gray nebulosity that offers little to no detail. But M82, one of the two Bode’s galaxies?  I’ve not had nearly as much time with M82 with the new scope but in the brief time I’ve had I’d say it is improved a good bit. It might not prove to be as dramatic as the view of the Orion Nebula but it’s definitely better. The same for the Andromeda Galaxy and the Triangulum Galaxy. My expectation is that objects such as galaxies that can offer a view of spiral arm structure will benefit a good bit which is great because they are some of my favorite objects to view. Some nebulae will be improved, others won’t. I doubt larger open clusters of stars will be improved but I suspect the resolution of some of the fainter stars in some open clusters will be as will some globular clusters.

Second night with the Z12

Little Dumbbell

My planned highlight for Sunday night’s chilly adventure was the Crab Nebula, but, though it was nice, it was not much improved over what is visible with the 8″.  The highlight of the night, as it turned out, was the Little Dumbbell Nebula. While it is less impressive in what it is (when compared to the Crab), it was a bit more interesting to look at! While the Crab presents a fairly large object in the eyepiece it is mostly just a nebulous cloud with no structure. I have read that with scopes of 16″ structure and detail begin to emerge but at 12″ it’s still just a gas cloud. The Little Dumbbell presents a nice object with a very interesting, much more compact and defined shape.

There were several nice open clusters in the constellation Monocerus and a whole slew of galaxies in Leo. 14 objects knocked off my Herschel 400 list plus just for fun looks at Andromeda, Jupiter and the Orion Nebula. Almost 7 hours, 21 degrees when I came inside and started a fire at 2am! A great night!

12″ Zhumell Dobsonian Review and First Light

Pardon the rope, the Telrad was not permanently
attached at the time fo the photo!

This post will serve both as a review of the new telescope as well as a report on the previous two nights of viewing with it. So, yes, unexpectedly I purchased a new scope. I’d planned to purchase a 16″ this spring/summer but upon seeing the current prices of the Z12 I decided that, based on my budget, spending $750 now would be much wiser than $2,000 later. As much as I would appreciate the added light gathering of the 16″ the 12″ is a substantial upgrade from the 8″ and should be enough for now.

The scope arrived in good shape in undamaged boxes. I had it put together in an hour and that was taking my time. This is a huge scope for one person to safely maneuver. I’ll be happy to have it in a permanent location with shed that will get rolled back during use.

Collimation before first light was a bit tricky. I’d read that the laser collimators that ship with these are out of collimation themselves and are of no use until they are collimated first. I set about doing that but adjustment screws are of a size (allen wrench) I do not have. Luckily my observing buddy Russ had his. Getting the secondary aligned was easy enough. The primary mirror, on the other hand, not so much. It seems that the tension springs in the adjustment bolts are pretty weak. As I turned them this way and that it became clear that I was going to have a hard time getting the mirror where it needed to go. Then it occurred to me that the lock screws, while not intended for adjustment, often do effect the mirror when tightened down so I tried turning a them a bit and presto, I had a collimated mirror.

This is a big mirror that will often need cooling down which is why they include a fan. I have not used it yet because I had it out in the shade on the first day and in the well house the second day so it was cooled off and ready to go at dark.

A few words about the hardware on the scope before I delve into what I saw with it. Everything seems very solid.  I’ve not used the finder scope yet because I ordered a Telrad and have used it both nights. That said, the finder seems decent in terms of construction. The big plastic cover for the OTA (optical tube assembly) is a pretty loose fit so I’ll have to do something about that. Of course the stand is particle board like all of these mass production units but seems solid enough for now. Movement of the scope is very smooth and it is very well balanced. I WILL upgrade to a home built birch plywood stand at some point. All in all, the scope seems very well built. I’ve encountered no problem other than the above mentioned weak tension springs on the collimation screws that I’ll replace and the loose cover.  As you can see from the photo, this is a huge scope and not something I want to move much.

The dual-speed Crayford focuser is very smooth and a nice upgrade over the focuser on the XT8. Being able to fine tune the adjustment is a very nice benefit of this focuser.

First Light for the new scope was Friday night and it was perfectly clear for it! My intent was to spend some time just getting familiar with the bigger scope and compare some of the views with what I’ve seen with the 8″. There’s no doubt it is impressive.

First object viewed was Jupiter and it looked great. The main difference, given good seeing conditions, is a sharper image. The 8″ struggles with the 5mm EP but provides a fairly crisp image with really good seeing conditions. The 12″ provides an even sharper image with a few more details  in the cloud bands and also seems to have a little more tolerance of poorer conditions though I won’t know for certain until I’ve used it more. Of course the same eyepieces also provide higher magnification due to the different focal length. The 5mm needed for detailed planetary viewing gives me 240x in 8″, but 300x in the 12″. So, not only is it a sharper image but it is also more magnified. Even better, I could, push it to even higher magnification if given the right eyepieces/barlow whereas 240x is the upward limit for the 8″.

Next up for comparison was M31, M32, M110: The Andromeda Galaxy and it’s satellites. This is a big and very bright object so what I was hoping for was some detail. With the 8″ I get a big and beautiful view but no detail. With the 12″ I am seeing some structure. It is especially noticeable with the 11mm Explore Scientific 82 degree (provides a wider field of view than standard lenses). At that level of magnification I am seeing a smaller picture but I do see the dust lanes which I don’t think I’m seeing at lower magnification. In all the EPs the 3 objects are beautiful and the more faint M110 is much more defined and easy to see.

Next on the list, the Orion Nebula which never disappoints! In the 8″ the nebula presents a fantastic view and in the 12″ it is a fantastic view. More detail is visible and some of the dark areas are more pronounced. I’ll have to spend more time observing before I can offer any more detail.

Now we are getting closer to those things which I expect will really benefit from the 12″. Specifically, globular clusters, faint nebula, and distant galaxies. A great example would be something like NGC 2158 which is very rich open cluster in Gemini which almost seems like a loose globular cluster. In the 8″ it presents as a nebulous sphere with little to no resolution of stars. In my first attempt to see it back in September I failed with the 8″ due to deteriorating atmospheric conditions. The second attempt the next night was a success but the view provided little detail. By contrast, the 12″ presented  this cluster as very easy to see and with much greater detail as many stars are resolved. Through the 12″ this cluster of stars is now exactly that, a cluster of stars and not just a nebulous sphere.

My next target was the Pacman Nebula, NGC 281 in Cassiopeia. With the 8″  I had no success finding it even with the NPB nebula filter. With the 12″ it was easy to see.

After that, a trip to Bode’s Nebulae, two easily visible galaxies in Ursa Major. These are easy to find, I was hoping for greater detail. Unfortunately I didn’t get much but more than likely that was due to my not taking the time. The night was getting on and I wanted to get some of my remaining Herschel 400 so this is by no means conclusive. I fully suspect that when I revisit and spend more time on these I will indeed see some new structure.

Last on the list were my remaining Herschel 400 galaxies in Ursa Major, 11 to 12 magnitude. While the 8″ would make these visible they are often incredibly faint. With the 12″ they were easy to find with little to no effort… it was so easy I almost felt like I was cheating! They don’t provide much in the way of detail but certainly more than is visible with the smaller scope. I’m sure I’ll have more to say about viewing these fainter objects as I spend more time with the Z12. Suffice it to say that the light gathering capability of a 12″ scope is fantastic.

I’d intended to offer up the second night’s viewing but I’m going to save it for the next post as this is getting quite long! Stay tuned.