jetstream

A shim?

Great report Stephan! I too try to get some late night obs in at 48.6 latitude. Some of the nights are very rewarding and I must try some of your targets.

Under very dark skies and using eyes that have observed Barnards Loop many (hundreds of) times with an Hb, yes a UHC will work. Barnards Loop is one example of a really fussy object exit pupil wise. A prime target for the Hb is the California neb, which is also tough. I'd pick easier targets to consider at first like the Flame neb near Alnitak- this one will teach much about scatter, filters and non filter observing. The H130 is a prime scope to use on the large targets like Barnards Loop etc and shows it easily with the NPB.

Ok, I'll use a filter at 1.7mm exit pupil for small planetary nebula. Some of this stuff is object specific but in general a tight OIII likes 4mm-6mm with 5mm being preferred by many in dark skies and 4ishmm in lighter skies. The only real way to find out is to try different fl eyepieces but it is a mistake to use a higher power eyepiece right off the bat IMHO. Many have done this only to think filter performance is marginal. Our H130 with a vg copy of the DGM NPB and a 5mm exit pupil shows: Veil-both plus Pickerings Wisp, Flaming Star, Pacman. Monkeyhead,Rosette, Merope, IC 1318, Nort American neb, Pelican ....

How dark are your skies? The old exit pupil deal applies- both OIII and UHC like a bit more than the 21mm Hyperion gives at f6.3. For the Veil itself the OIII is what you want and it will also excel on many other targets. The extra detail you might have heard about with a UHC typically comes from using one under dark skies IMHO. The newest Astronomik OIIIs have a vg tight passband, the older ones are a bit wider.

John has much experience. I use a soapy mixture to first rinse the mirror then use the soapy mixture again as I gently rob the primary with my fingers. The fingers allow to feel any grit and to stop and re lube with soapy water. I use RO or distilled water for the final rinses. I use more dish soap than suggested but this gives much lube. I do not soak any of my mirrors. Dirty mirrors cause scatter among other things. As long as there are coatings in the first place and theyre intact and complete things like acetone and alcohol can work for stubborn oil based contamination. I've used it for removing center spot glue when replacing with Catseye triangles. DO NOT take my word on all this however, its just worked for me and my mirrors.

My coater says to clean regularly as any organic material on the surface in conjunction with moisture (dew etc) will cause etching of the surface. I only use de mineralized water and Sunlight(mild) dish soap.

Great idea! In reality I want to get this bad boy on the Pleiades...

Great review Jeremy thanks for the info- I'm going to get one soon myself.

I think you and I get very good views with basic cooling - my VX10 got Mars at 400x years ago and gave a view thats still burned in my brain. Not sure about others but if basic cooling is done the sky is normally the limiting factor.

Excellent review.

There should be no air movement... if the primary mirror is equalized along with the rest of the scope there will be no convection- and no need for induced air movement. As always we observe with whatever is the least of ills- if my view is better with the fan I use it. My very best views are with no fan- the 15" dob goes 600x on Jupiter and over 760x on lunar when equalized - very very sharp. Obviously seeing has to support this. Testing has shown me that even 2c-3c temp diff is enough to hinder views. I use a Fluke IR heat gun to test. Suiters wobbly stack definitely at play here.

Intuitive thought JOC "Fan Vibration Detecting vibration Microvibration in the image frequently goes undetected. The best way to detect it is by examining the Airy disk of a bright star at high magnification, and switching the fans on or off. The size of the Airy disk should not change. This test requires magnifications of at least 30X your aperture in inches (the May 2004 Sky & Telescope article describes this test in more detail). Sources of vibration All fans vibrate, and even the smoothest fans create a microvibration problem if improperly mounted. The primary sources of fan vibration are a) impeller blade imbalance, b) slight variations in the airfoil shape of each blade (called "reaction imbalance"), and c) bearing resonance" https://www.fpi-protostar.com/bgreer/fanselect.htm.

Not sure if youve seen this John but I found it interesting https://www.fpi-protostar.com/bgreer/sep2000st.htm

I did this too. I think that it might make a difference depending on the scope design ie fast newt with stray light issues itself but in my Astrosystems which has a focuser baffle (the filter slide, matte black) no difference is seen. I did my diagonal barrels as well and on the mirror diag a difference was noted but not the prism. If a newt is not flocked or painted, the edges not blackened etc painting the EP barrels will most likely show a difference, however its not the first place I'd start. The Astrosystems dobs have superb stray light control, my VX10 needed some help in this regard. The 10BCO is the deepest eyepiece I own.

I think most astronomers should own one of these or the H130- for travel or the quick unexpected session- or just plain old observing. Personally I respect the simple, rugged, nothing go wrong focuser and the ability of these light mirrored scopes to hold collimation. The secondary on the H130 has never been touched and the primary is never far off even after a snowmobile ride. I'll burrow into areas with this scope in the snowmobile bag that would surprise many here- zero problems with the scope or mount.

Me too, but these 2 filters are welcome additions to the permanent line up. I understand these Televue filters are individually tested, no hocus pocus surrounding batch testing and this should eliminate the "good one" issue. So unless I got "good ones" all their filters should perform this way- I never thought my 2 older Lumicons could be equaled or actually be edged out and beat. You know, I had these 2 filters checked on an independent spectra analyser via Astrosystems and the numbers and profile were confirmed before I got them. I then put them side by side in the filter slide(s) to see what the visual differences were there. My current thought is that these filters maintain a tight profile but with better transmission- my Lumicons numbers "might" be a bit optimistic in the transmission dept. Eventhough experts say "small" differences in transmission cannot be detected I humbly think that when it comes to tight filters we can. Oddly enough the Lumicon UHC feels tighter but the Televue Nebustar II shows more? Man, you should have seen IC1318 last night John, this is a huge area of nebulosity and the Nebustar performed beyond expectations again.

I believe this telescope will excel under these conditions Stu, espc in the IC1318 area and the North American nebula. It will be perfect for the Pleiades Bubble, an object complex that I truly hope others can observe. The f5 gives flexibility to up the mag a bit on objects like the Swan etc. It will also be perfect on the Rosette nebula and many more. Once I can get astro equipment again, I will have the H150 sitting here for my grab and go- the H130 is actually my grand daughters that she kindly lets me use. Skywatcher has stepped up and created another affordable, portable and super effective telescope in the H130.

We have had a few days of heavy rain and thunderstorms which have cleaned the sky - tonight was super transparent with the sky offering 17 Umi at 6.8 mag in direct vision.I believe averted would approach 7 mag. Under these conditions so many targets reveal features brightly including the mass of nebulosity in IC1318, unbelievable actually. The 15"/21E and the new and excellent Televue Nebustar II worked magic here, it is a must see. Using the new Televue OIII (top of the top in OIIIs) Pickerings Wisp started to show features that the 24" presents easily such as a "bubble" in the tail end of the Wisp. The whole Veil was photographic like. I got hung up here for about 45 min lol! And then there was the Pelicans head... I love this feature and obviously the NAN was very bright and again the Nebustar II proved itself again. This was a really simple observing session, no DSC and 2 eyepieces, the 21E and 10mm Delos, the latter chewing up M51 spirals so easily, another wicked sight. I'm pumped that a mag 6.8 star showed so well in direct vision, a testament to the rains power to clean the sky and the MW showed its split brightly up over my pine trees. I need skies just like this- great seeing and super transparency to have a chance on Einsteins Cross, its too bad they both don't happen together often here. Good seeing with good trans yes but skies like tonight are just a teasing gift I recon!

Just look through one... In comaparison to my 17E the Nikon 17 HW offers a more contrasted view on nebula which is quite a feat actually. The Swan, through the 17HW is a stunning stunning sight, filtered or not. Thing is you get both a 17mmm and 14mm for the huge price... I bought mine directly from Japan when our dollar was more friendly to the Yen and did not pay near the quoted price in this thread. And yet! the 20mm Lunt can hold its own in this crowd...

We love the H130 and the H150 is going to end up in my scope collection. From our perspective the helical focuser is very practical- it works in extreme cold down to -40c where my other focusers do not, yes we observe in these temps. I'm happy to see the H150 offered for sale.

If we were going to replace the word "bang" what would it be with? What is the proper description of the event? I want to drop the phrase big bang and replace it with something so when I ask about it at least I know what to call it lol!

I am humbly going to ask what the definition of a singularity is? Any and all aspects of its definition is greatly appreciated and is the instant of the universe creation a singularity?

Good to know- I was asked about this Docter clone and if it was a contender. Maybe I'll pick one up to compare to my Docter.

Yes a singularity was explained to me as point where the math breaks down. I guess my concept of infinity (in reference to the dense state) needs work- I think by framing it as an object I'm wrongly imposing spatial limits. I sure like these threads thats for sure.