Jupiter, at last! (And oh, Messier 31 and Messier 42)

The weather was OK today, so I had to do some observations – this might have been my first "proper" deep-sky session. So far I my only "proper" observations were of the Moon, Saturn and the Pleiades. Some time ago I got some first (and suboptimal) glances at M31, M13 with my 70mm refractor, and of Jupiter, Venus and Mercury by naked eye, and recently first glances of Jupiter with two scopes.

But today I used the 5.9-inch Newton scope for my first "proper" session of M31, M45, M42 and then Jupiter – though first I took some wide-angle images, with the 400D and the 10-22mm lens, at 10mm, f/4, ISO1600 and over 1 minute exposure – just to do some long-exposure photography again after a long hiatus.

The house of our friendly yet annoying neighbour… Light pollution to the left came from a sports-ground – they later switched off their flood lights.

My small slice of the milky way – and some undefined orangeish streak (probably clouds illuminated by our beautiful high-pressure-sodium lights). I intentionally photographed the airplane passing through the photo.

First I observed the Andromeda galaxy (Messier 31) while it was at about 40° altitude. Frankly, I'm still a bit underwhelmed by M31 in my 5.9-inch (150/750) scope – yes, it is noticebly brighter than in my 70mm refractor (and I am not experienced, and not properly dark adapted), but still… Lacking a light-pollution filter, I tried the poor man's substitute: color filters. I tried blue and green filters, and they increase contrast (and make the periphery discernable), but obviously they make the whole image darker. I tried the 40mm, the 30mm, the 25mm and the 20mm (all Plössls). Still undecided whether color filters are recommendable as a cheap light-pollution filter.

Later on I observed M31 as it was almost in the zenith, and I was under the impression that the image was slightly better.

Regarding the Orbinar 40mm and 30mm Plössls I must notice that the eye-relief is too long, the eye position is critical (kidney-beaning) and the lack of an eye-cup is sorely noted.

I then shortly moved on to the Pleiades (Messier 45). The "tail" was visible to me, but the "last two" stars only barely (TYC 1800-1783-1 with magnitude 10.12 and TYC 1800-1804-1 with magnitude 10.32).

Later on Orion became visible and I had to check out the Orion nebula (Messier 42). It was more impressive than M31, but still it lacked the "Awwwh!" moment that seeing Saturn's rings for the first gave to me.

As a last observation I waited for Jupiter to clear some roofs here. It was a much superior view of Jupiter compared to my past encounters – I have finally "really" seen Jupiter. Well, not "really" actually but the two dark equatorial bands I saw were an improvement. (And little Io was there close to Jupiter, Ganymede on his side, Europa and Callisto on the other side)

Now my muscles hurt and I had to stop. It was a bit too much cramped into one session for me with my health problems – but the weather was good and I don't know when I will get the next chance (yeah, someone give a house in the south of France, please?!?).

I must admit: I'm a sucker for eye-candy, for high-contrast images that are bright enough – oh well. The craters of the Moon, or Saturn's rings, that is my catnip – and even the Jupiter's limb. But Jupiter's bands? Oh, well, I've seen two of them now. I guess seeing wasn't that good, and the scope maybe was not good as well, and I lack the experience, but compared to the high-contrast views this is visually a bit lacking. I'll see if I can squeeze some better views out this scope.

And I need to remind myself of the wonder of what I'm seeing.

Plato Crater, Stray Light

Just doing a quick observation session, the full Moon beckons, and the weather is (almost) good.

• Full Moon was yesterday (and even a partial lunar eclipse), today the Moon was waning gibbous (Illuminated fraction: 0.993 Phase: 350°)
• Some seeing visible on the Moon's limb (in both the 150/750 and the 114/500), still not sure if this is atmospheric seeing or tube seeing
• The 114/500 has awful stray light problems. It depends a bit on where the Moon is in the FOV, and at what angle one looks into the eyepiece. I then looked into the focuser's tube without an eyepiece: The body of the secondary is made from shiny plastic – what could possibly go wrong with such an design??? Well for one thing: the light passing the plastic obstruction before hitting the primary is glaring, which is visible through the focuser tube (when viewed without an eyepiece). And secondly the area around the secondary is visibly shiny when viewed through the focuser.
• The 150/750's secondary has an similar plastic body, but much less problems. I will have to baffle both, I'm afraid…
• Plato Crater really stands out quite dark from the somewhat brighter Montes Alpes.
• The Moon is a good target to asses things like stray light and focusing. 
• I'm so glad to have bought the 150/750 Newton! 6-inch vs. 3-inch means twice the resolution and four times the light gathering. Can't wait to take a shot at Jupiter, and the Andromeda galaxy.
• My eyepieces are fogging over. Had to take a break and put the eyepiece case inside to warm up again… (Maybe I'm dressed a bit too warm, as I'm slightly sweaty…)
• I wanted to hold out and view Jupiter – but I got unbearably tired, my muscles started to hurt and clouds started to roll in – so I packed up again.
• I ask for only one thing: A house in the south of France…

Improving My Chinese-Build 6-inch f/5 Newtonian Telescope (Mainly Cooling)

I am currently looking into ways how to get the maximum performance of my cheap "light-bucket" 5.9-inch Newton scope, with minimal resources. Unfortunately – as with all affordable Chinese-build scopes – it is far from being "well-designed" and has several shortcomings, some of which should be addressed.

First of all, there are some points that might need addressing to get the maximum performance (the "last ten percent"), but which I will probably not do:

• Increase the Fully Illuminated Field. The position and size of the secondary are such that only the central on-axis point is fully illuminated (and only just about). But then again the obstruction through the secondary is small (about 25%), so for visual use this should be fine.
• Wider Tube. At the moment the tube is just a whee bit larger then the mirror – the diameter of the tube is about 170mm (6.7 inch, haven't properly measured it yet), with the mirror diameter (hopefully) being 150mm (5.9 inch). A wider tube might aid the cooling, but that would mean a complete rebuild – but in that case I would probably try some sort of portable design or even some ultra-light Dobsonian design for that scope.
• Thinner Spider Vanes. These things are thick! Cast metal, baby! But probably the spikes won't bother me…

But if I wanted a perfect scope, I should start by getting a perfect mirror (and probably a larger one at that!), because my mirror is most certainly not top notch. So as my time&energy&money are limited (and as I will not buy a better mirror), next are some points which should be reasonable, and which I will therefore address:

• Focuser shifting. While I have addressed this already, the focuser is now too stiff and I need to readdress this problem once more.
• Baffling. I will have to add some felt in to focuser tube and opposite the focuser, and possibly baffle(s) in the focuser and at the mirror cell. Plus the secondary's holder is made from shiny plastic – I should baffle this as well.
• Cooling. This is at the moment the most obvious problem: Tube currents despite ample cool down time.

With regards to focuser shifting, I will have to see what I will come up with.

Mel Bartels has something to say about baffling:

Proper baffling ensures that no unwanted light enters the focuser. There is a baffle just below the focuser and a baffle opposite the diagonal. The focuser baffle is particularly important.  Both are covered with Edmund Scientific black felt. The primary is also baffled, just in front of the glass, and totally enclosed in ultra flat black. It is an impressive demonstration to shine a powerful flashlight on any part of the scope, and discover that your observing buddy looking through the eyepiece with his eye cupped cannot tell you when you have the light on or off. The goal in baffling a minimalist ultra light is to block every ray of light not coming from the primary mirror. Extra baffling to absorb secondary reflections from the baffles is used in high performance refractors, but this is a luxury we can forego since the flashlight test is quite convincing when using light trapping felt or velvet.

With regards to cooling, the simplest way is to add a fan is at the rear. There are more elaborate ways of cooling (and the first order of business is keep the primary mirror as thin as possible), but these methods are overkill for my puny 6-incher: One could add a fan in front of the primary, blowing on the primary. Or one could add a fan at the side, creating a laminar flow across the front face of the primary, and scrubbing that darned boundary layer of the primary. Best would be to actively cool the primary through some attached machinery (cooling pipes, peltier elements, and somesuch black magic).

Bah humbug, too complicated and not needed for my scope. (Though I would love for a bigger mirror to combine electronically controlled peltier elements at the rear of the primary, with a laminar flow across the front face of the primary – should make one heck of a good scope I'd reckon.)

Instead I will stick to putting a fan to the rear end of my scope, and call it a day. But should it act as an "rear exhaust", sucking out warm air? Or should it be a "rear intake", blowing cold air at the back of the primary?

	Advantage	Disadvantage
"Rear Exhaust"	– Motor heat is kept away from the primary – Better scrubs that boundary layer off the primary (maybe) – Less dirt in the tube (maybe)	– Less efficient cooling of the primary – Increases the dew-risk for the secondary (maybe) – Works against the natural convection (possibly maybe more turbulent)
"Rear Intake"	– More efficient cooling of the entire rear face of the primary – Keeps dew away from the secondary (maybe) – Works with the natural convection, not against it (should be less turbulent, maybe)	– Motor warms the air – Sucks in more dirt from the ground (maybe) – Not so good in scrubbing the boundary layer off the primary (maybe)

So I will go for the "rear intake" solution, and mount it on "some sort of circular mask" so the fan is decoupled from the scope, and air is forced in. With a 6-inch diameter primary I count on the glass being 2-inch or less, so it should be enough to cool it from the rear.

What I dread is adding batteries, cables, connectors and the like – it will complicate the setup, and I already hate the thought of it. And I need to take care of my powersource, change/charge the batteries – bah!

And to add a fan I have to take the scope apart, I guess…

Quick Look at the "Roegger PEGASUS" 150/750 Newton

On Sunday I bought another scope: An Newton reflector, called "Roegger PEGASUS", with 150mm aperture and 750mm focal length (which works out to f/5 focal ratio) – a big mirror in a cheap package. 

Prices range from 90€ (used on eBay) to 140€ (new on eBay), and up to 230€ (if you buy new from an "proper" scope shop on the internet) so I was lucky to get one for 70€. With prices about twice of an 70/700 refractor, will this be twice as much fun? It is cheaply made, but has some potential as a fun scope. :-) I will use it less on planets (my long focal length refractors are probably better suited here) but more on Deep Sky objects.

My scope was branded as "Roegger PEGASUS", but can be found here under various other "brand-names" (and color schemes). There are different versions floating around:

• The version without an corrector (focal length 750mm), available as an "Roegger PEGASUS". Seems very similar to the "TS Optics Starscope 1507", and somewhat similar the "OMEGON N 150/750 EQ-3".
• The version with an corrector (focal length 1400m), available as an "Seben Big Boss", "TS Optics Megastar 1550" or "Bresser Pollux N 150/1400 EQ-2".
• And then there are hugely better versions: Three is e.g. the "Celestron OMNI 150XLT", or the "Sky-Watcher Explorer 150P EQ3" (and possibly the GSO). These have an parabolic mirror and much much better EQ-3-2 mount (aka "NEQ-3"). These telescopes are for all practical purposes completely different scopes.

Beware: Even if the numbers are the same, there can be differences between the brands!

What was included with mine:

• The OTA with 1.25" focuser (rack and pinion)
• A corrector lens ("Bird-Jones") was not included
• An EQ-3-1 mount An EQ-2-2 mount
• Two mounting rings and one "screw on" rail (that almost looks like a thin dovetail rail)
• One Plössl 25mm eyepiece (1.25", non-standard filter size) 
• One Plössl 6.5mm eyepiece (1.25", non-standard filter size)
• One 2x Barlow (plastic housing, singlet glass lens, lots of stray light, same Barlow as the one supplied with my 76/350 table-top Dobson)
• One "1.5x erecting eyepiece" (ignored)
• A "6x30" finderscope (which I ignored mostly, for now) with 30mm aperture and achromatic lens
• A flabby finderscope-bracket

Some of the things worthy of notice:

• The primary is in all likelihood spherical.
• [Update 2013-11-01] The diameter of the primary is 153mm (6 inch), it has a grinded bevel of about 1mm width, and the edge of the primary is 14.5mm thick. (BTW: I used a black marker to darken the bevel.) 
• [Update 2013-11-01] The adjustment of the primary cell is done via three sets of push/pull screws, but no springs – longer screws and a set springs will greatly benefit the collimation process. BTW: The scope was only "screwed together" (one could see that all three "pull screws" were screwed in first, and the "push screws" were barely threaded out) – but collimation was somewhat OK, I have seen worse.
• [Update 2013-11-01] The secondary needs slight adjustment – I will have to do a proper collimation.
• [Update 2013-11-01] The full diameter of the back of the primary is covered by a foam pad, a piece of cardboard and on the outside a piece of camera leather (together about 6mm thick). I removed all three and put in some small DIY pads underneath the clips of the mirror cell.
• The secondary mirror is rather small (roughly 38mm, about 25% central obstruction) and does not fully illuminate the primary. I suspect that the effective aperture is more likely to be 120mm to 130mm (very rough estimate). [Update] I've done the numbers and a 38mm secondary (at an distance of roughly 560mm from the mirror) will fully illuminate 150mm (on axis, that is). Some off-axis vignetting will occur however: to illuminate a diameter of 20mm at the eyepiece one needs an secondary of about 52mm diameter. (If used with a Barlow the vignetting will be reduced. One needs however to make sure that the Barlow itself does not add vignetting…)
• The spider holding the secondary has three vanes which are rather thick (5.5mm). But people who done tests write that it won't hamper contrast much (if it is noticeable by me anyway) – collimating (and a good figure of the mirror) is more important.
• The diameter of the OTA tube seems to be a bit too small.
• At the outside of the OTA one can see that the scope is cheap: The seam of the OTA protrudes a bit, and when you rotate the OTA in the mounting rings you the OTA seam will "bump" against the hinges of the rings… But that is only a minor problem.  
• The OTA tube is deformed at the end of the mirror. O.o This is caused by the OTA end ring being too large, and the screws connecting the end ring with OTA tube cause the tube to be deformed. (Furthermore some light can get inside the tube through the gap between end ring and OTA tube.) [Update] For each screw holding the rear cell to the OTA, I put some one washer inbetween the OTA and the rear cell.
• There is a thread at the inner end of the focuser's tube, probably for an Bird-Jones corrector to double the focal length to 1400mm. (With this corrector the secondary might fully illuminate the primary – don't know, sure would like to know.)
• The focuser itself is quite nice. Only major problem was that the focuser's tube was loose! The tube had at least a couple of degrees play! However with a bit of flocking material I took take care of it. Otherwise the focuser's tube does protrude a bit into the OTA, if fully racked in (but not too much). The eyepiece retaining ring is made of metal and quite solid (nice), the focuser's tube is made of metal (nice), the focuser's casing is plastic (but OKish), the tube has lot's of travel (nice), the knobs are large enough (nice).
• The filter threads of the eyepieces is non-standard. (At least the barrels are interchangeable with the eyepieces from the 76/350 – those have a standard thread at one end and a "coarse" thread at the other. So I could exchange the 1.25" barrel from the useless H20mm eyepiece and put in on the PL25mm – now I can use standard filters with PL25mm)
• The supplied "Moon filter" is the most nonsensical piece of astronomical equipment I have ever seen. It is a (heavily over-engineered) disc of solid aluminium painted in black, with about 8mm thickness (!) and 30mm diameter. The filter is held by an screw-in plastic retaining ring with an clear aperture of about 12mm. The filter itself has about 15mm diameter. And now comes the real kicker: The green plastic filter has curved surfaces in the center and flat on the periphery of the filter! This thing looks like the bottom of a green Coke bottle… With the non-standard filter-thread, it doesn't even make sense to replace the filter glass, if you happen to have an 15mm diameter filter lying around.
• The PL25mm eyepiece has an "additional" section between the 1.25" barrel and the optics. This section seems to be designed to hold an reticle (again heavily over-engineered).
• The finderscope bracket is very awful.
• An EQ-3-1 EQ-2-2 mount (and tripod) was not made for such heavy scopes. The problem is that the axis have to much play and I haven't found a way to reduce the play any further. My EQ1 (adjusted, with DIY wooden legs) seems more up to the task… But the legs of the EQ-2-2 are better than those of the the EQ-3-1.
• The counterweight rod is 10mm (like my EQ-1/EQ-2) and not 12mm (like my other EQ-3-1).
• The counter weight is one piece of about 2.9 kg.
• The counter weight rod does not rotate (like my other EQ-3-1 mount).
• The "north adjustment" of the EQ-3-1 EQ-2-2 is slightly different than my other EQ-1/EQ-2/EQ-3-1 mounts: Normally there is a machine screw at the bottom (that you don't need to touch), and a tommy screw at the side to fix the north position. But here there is only one tommy screw at the bottom. The advantage is that you can easily separate the mount from the tripod.
• The tripod legs are more stable than those from my EQ-3-1 (from my 70/700).
• The mounting rings seem quite sturdy. Opening the rings requires completely unscrewing two screws, which is a pain in the proverbial behind.
• I have mounted the scope on the dovetail and mount from my 70/700 – but without a supplied quick-release the combination of scope and mount is quite unwieldy.

  Enough written today, hopefully more once I played around with it a bit.

Serendipity – Broken Glasses and the Pleiades

Yesterday I bought an used 150/750 Newton telescope, of course I got it rather cheaply (this *is* Cheap Astronomy, after all). The 150/750 telescope is everything it promises: a large mirror in a cheap package, with quite a few quirks – it will be fun playing around with it.

I choose a scenic route back from the seller (having no chance to do otherwise an vacation, this was quite nice), and while I was exhausted from the journey I had to try out the new scope at the night sky. And then it's when it happened: I had the glasses rather carelessly on top of my head, they fell down and broke (right in the middle) into two pieces. Though I don't need them to look through the scope (and prefer rather not to wear them at the eyepiece) they are necessary for me to look with the naked eye at the night-sky. Without glasses, the stars are quite blurry – which proved to be a fortunate accident. When I later scanned the night sky with the truly naked eye (after having possibly seen the California Nebula in the 150mm Newton) I stumbled without glasses upon the Alpha Persei Cluster, (aka Mel 20, Melotte 20 or Collinder 39) the Pleiades.

[Update] I am such a noob. I got side-tracked in my star-charts and can't properly tell altitude. The object I saw was much lower in the sky (about 20 degrees) than Mel20 (about 45 degrees) – it was the Pleiades! In a 70mm scope at 12x magnification they look a little bit different than the photos: much more lively. Though I should have recognized them in the binoculars. Doh. m( Thankfully nobody reads this. :-) [/Update]

For me, without glasses, the Pleiades seem like a longish blur, a bit reminiscent of an elongated galaxy – standing out quite clearly against the night-sky. There is something there! I grabbed my 7x60 binoculars, and sure enough there is a nice star cluster there.

Next my modified 70/300 refractor came in rather nicely. With a 25mm Plössl (at 12x magnification) it was splendid. The refractor revealed more than my (bad, bad) 7x60 binoculars, showing the brilliance of the stars in that cluster rather nicely.

What is important to have a large field of view to reveal the contrast between the star-rich cluster and the "normal" night-sky with a lower star density – if you yank up the magnification then the star cluster will look like any other star-field… Though (at 300mm focal length) a PL30mm, PL32mm or PL35mm eyepiece would probably be nice, as with the lower magnification (10x, 9.4x or 8.5x respectively) it might reveal more of the surrounding sky, and frame the cluster better.

I must say, the Pleiades are a night-sky target well suited for binoculars and small telescopes with low magnification (in the range between 7x and 15x) – highly recommended eye-candy!

[Update 2013-10-05] Now that I know what to look for I took another look a the Pleiades yesterday. Some cloud-ish something was hanging in the East and the view of the Pleiades wasn't nearly as vivid as I the first time I saw them. I could have sworn: the first time I say the Pleiades I thought I could discern different star colors. Mainly blue for the brighter ones, but some orange-ish dimmer ones interspersed. (I think my memory is playing tricks on me).

No colorful stars yesterday, and much less vivid – the weather was not as good last night. At both nights I tried the Pleiades with the 70/300 Refractor and a PL25mm (12x magnification) and my new 150/750 Newton and the same eyepiece (30x magnification). The 5.9 inch Newton is significantly brighter, as was to be expected. The images at that magnification are good in the 5.9 inch Newton, but of course the Pleiades now fill the entire FOV of the Plössl. A PL32mm or maybe a PL35mm would be a welcome addition to my eyepiece collection – maybe for Christmas. :-)

I am very happy to have bought that cheap 150/750 Newton. The EQ-3-1 mount and tripod isn't great, but I got it to behave with some small mechanical modifications.

On the first night I saw the Pleiades I tried the little 76/350 Newton as well (which has an effective aperture of about 60mm) and I must say the images are not good compared with the 70/300 Refractor (which is a badly collimated instrument). Viewed through the focuser's tube it is obvious that the secondary of that little Newton is too much to the front. The primary is not adjustable (at least without some DIY modifications) – but adjusting the secondary might help a lot.