great_bear

Just by checking out astrobuysell UK twice a day, and immediately expressing interest the moment something comes up. Sellers might be slow at updating to ‘sold’ or often don’t seem to bother doing so at all, so it’s quite common to think something is available but discover it was already sold the day before - it can be frustrating. I think at least one on the list came from here on Stargazers Lounge.

I started collecting these a few years back after noticing that Bill Paulini liked them.

It didn’t take long to build up a full set:

I didn’t get the 40mm as it does not appeal to me.

When I look at this assembly video for the Vixen, the centre section doesn’t fill me with confidence. It doesn’t look designed to withstand the twisting/flapping that a long-length scope might place upon it. 
 

8 hours ago, AstroKeith said:

They can be had for half the price elsewhere. Typical Selfridges mark-up.

Indeed - I probably should explain that to my kids, who I think left Selfridges a bit depressed and thinking they’d never be able to afford any nice things in life. 

https://www.astroshop.eu/instruments/fujinon-binoculars-lb-25x150-mt-sx/p,23647

(although note that the above doesn’t include the mount and tripod, which Selfridges does in their price)

28 minutes ago, bosun21 said:

I have reached the end of the adjustment for the fulcrum point

Ah OK - I was referring to balancing between lightest and heaviest loads. 

But I do see how you’ve reached the absolute limit. Looking at mine there’s only about 15mm of adjustment left, which wouldn’t allow much more than the load I’ve got. Easy to fix by counterbalancing but it is indeed surprising that they didn’t provide for a at least a bit more travel on that adjuster.  

Unfortunately a little out of my price range for my Christmas present:

1 hour ago, bosun21 said:

Not so for me. I also have the Starsense unit and a RQ on mine and when I add my phone and a Baader Morpheus into the equation it most definitely needs a counterweight.

Do you mean that you’ve reached the end of travel for the adjustment? - or that the difference between your lightest and heaviest loads is too great?

Anyone used that Vixen at all?

Oh, one other thing for those who decide to use magnets, if you don’t want to stick anything on the scope, you could wrap a magnet in sticky-backed foam, as I did with this one I use on my 150PL (note also the thick red rubber-band as a handgrip) This is the size of a large bar of soap, and I have used it for many years now:

On 10/11/2022 at 14:11, Louis D said:

these GSO scopes have been available under multiple other brands for years.

Yes, I have the Telescope House one, under their Revelation brand.

I found that when the correct balance position and tension is dialled in, no magnets are required for balancing, regardless of what eyepiece is used (note that Delos are the heaviest that I use). I did upgrade to the (now standard) RACI finder but went back to the straight-through finder. I operate this scope sat next to it and in this position straight-through is much more intuitive to use and doesn’t seem to cause me any neck strain.

The only extra thing I bought was a (very expensive) shoulder bag (Orion USA) for the OTA. I agree a handle would be a better (and cheaper!) option, although I suspect the shoulder bag could help avoid condensation when bringing into the house but proving that, would be a Schrödinger’s Cat exercise 🙂

I bought the scope for use at the Baker Street Irregular Astronomers’ meetings because I discovered only Dobs can withstand the breeze at The Hub in Regent’s Park and give rock-steady views. Experienced and new stargazers alike never fail to be taken aback at how startlingly good the views are through this scope - it has a fine mirror. 
 

Does anyone have thoughts on the relative merits of these three mounts (it will be for a 150PL scope):

• Berlebach Castor II
• Sky-Watcher SkyTee 2
• Vixen Advanced Polaris Altazimuth APZ

Which is best?
(it will sit on a Berlebach Planet)
- Is there much difference in smoothness/stability?
- Do any fall into the “avoid” category?
 

My 150PL is a heavy scope (maybe 7Kg) so minor differences in smoothness will probably make little difference. 
(I am currently using a Sky-Watcher AZ4 head and it has too much backlash and wobble with this long, heavy scope)

Happy to hear alternative suggestions too. 

Mirror now moved - hoping this doesn’t cause a problem reaching focus in the opposite direction 🙂

Looks like it’ll be a couple of nights before it’s clear enough outside for me to try…

2 hours ago, AstroKeith said:

I believe Televue do a special "in-focus adapter" that brings the 'pesky' Delos par focal.

The downside is it’s pricey, and that the design necessitates an Allen key rather than a thumbscrew to secure the eyepiece (great suggestion nonetheless!):

(probably worth noting that it’s only parfocal when used with a paracorr, but is nonetheless still useful for reaching focus with eyepieces like the 17.3mm and 14mm Delos which some scopes can struggle with)

3 hours ago, Spile said:

Would there not be enough tolerance in the 35mm to allow you to achieve focus?

Unfortunately not - it’s that pesky non-parfocal 17.3mm Delos and the extra infocus that it requires!

In light of the comment from @AstroKeith I guess I’ll just move the primary forward instead; it’s easy enough to do. 

2 hours ago, AstroKeith said:

There is a minimum length to extension tubes as it has to be able to accommodate the whole of the 2" nose of the eyepiece. 35mm is probably the shortest you'll find.

D’Oh! Of course! That makes sense now - thank-you. 

The new mirror in my scope seems to have a slightly different focal length than the previous one.

This means I need to get a 25mm extension tube for the 2" focusser. 35mm seems common, as does 50mm - but I need a 25mm one.

Anyone know where I can get one?

The argument goes, at that particular exit pupil, why not just haul out a smaller telescope

If that’s the only eyepiece you’ll be using for the night, that’s a perfectly good argument for choosing a smaller, lighter scope to take that evening. 

Similarly it’s a reasonable argument to say that I’ve “wasted money” on this eyepiece (for my 8” Dob) when I can get an almost identical view in my wife’s 130P with the Meade 24mm SWA that I already have.

I do think that unnecessary cost is something that owners of multiple scopes should consider at low magnifications. 

In my case, I felt the hassle of setting up a second scope was worth eliminating by purchasing this relatively inexpensive eyepiece (in practice the central obstruction issue is easily avoided by off-centre eye-placement)

In the case of refractors however, it’s important to point out that there is precisely nothing to be gained by changing scopes - the view is identical in both cases - that’s why “wasted light” as a concept is a nonsense idea - there are no optical efficiencies to be gained. 

34 minutes ago, badhex said:

Ah, sorry for clarity I meant that an overly large exit pupil results in wasted light if your own pupil cannot dilate that much. I'm don't know for certain what my pupil dilates to but as I'm approaching 40 I suspect it's less than 7mm. 

Regarding mention of edge performance, I meant more the eyepiece edge performance than your own eye specifically. 

I know - it isn’t wasted light - that’s the myth (albeit a common one). 
 

It’s not “wasted” any more than the sunlight on the ground when you go out for a walk during the day. 
 

That’s because there is no optical configuration for that magnification that could “squeeze” that light into your eyeball. Your eye is already fully illuminated - no waste. 

On 16/09/2022 at 15:28, badhex said:

I have been thinking that I need to try out the 40mm and 35mm side by side in my ZS73. Have been using the 40mm and ZS73 quite a lot recently and in general I really enjoy it. It definitely suffers at the edge but I'm not sure which performs better in that scope. 

I also recently read that as well as obviously wasted light which I knew about, an overly large exit pupil can supposedly exacerbate some potential aberrations caused by your own eye? Trying to remember where I saw this. Last time I had an eye test a few years ago, the doctor said I had excellent vision with no issues, but maybe the larger exit pupil on the 40mm is causing some issues too?

No such thing as “wasted light” - at least not as far as refractors are concerned. It just means that you’ve reached the maximum light-gathering capability that’s physically possible (with any scope) for that specific power of magnification (and perhaps could achieve that same view with a smaller scope - not that there’d be any benefit in doing so, unless you’re planning on spending the entire evening in that view).

On the aberration front yes, the outer edge of the eye’s lens will - for some people - be not-so-good in terms of focusing the light bundle, so it’s entirely possible that optical quality might drop off for some individuals when you reach that point.

3 hours ago, Stu1smartcookie said:

Sorry to revive this but i think the statement is quite interesting .... Sure , i agree there is too much talk about ED glass types , but , when its used as a marketing tool , surely it HAS to be investigated as to whether its worth something . 

 

But a quite important part ? 

 

I think the key point is that ED is not a 'better' kind of glass - it's just glass with a different refractive index. The balancing of glasses of different indexes is a key tool to make sure the different wavelengths of light converge as closely as possible. There may be other emerging techniques in the optical designers toolbox that Sky-Watcher and others might not necessarily want to divulge.

The main thing the customer cares about is the performance of the scope overall. Agreeing on industry-standard, unambiguous ways of measuring, reporting and comparing scope performance is probably the thing to focus on (no pun intended). 

11 minutes ago, Ricochet said:

If the baffle tube is smooth internally there will be no issue with the flocking coming unstuck. If it has loads of microbaffles/is threaded then you might find it won't stick at all. If there is enough room inside the tube that there is no chance of diagonals, barlows etc coming into contact with the flocking then as in my photos above, I would recommend painting the flocking as well. 

Interesting.
 

I have next to me the chunk of sponge that I used to paint the Mak tube. Although the sponge is very stiff, I can squash it around and the dried paint shows no signs of shedding, which is good, and the paint hasn’t changed the visible appearance of the sponge (other than making it very black!). In a way, it’s behaving almost like ink, which is why I can see that painting the flocking paper might - under the right conditions - be beneficial. I’m just a bit worried about flattening the fibres in a way that spoils the flocking. 
 

I guess I could take two small test samples of flocking side-by-side, paint one of them and then test the result. 

1 hour ago, Louis D said:

What is the rear port diameter?  In my 127 Mak, I get reflections off the rear baffle tube from bright stars when using 2" eyepieces because the rear port is only 27mm in diameter at best.  I keep thinking I'll install flocking inside the rear tube someday to tame those reflections.

I’ve got the older, gold-tube version which out-of-the-box only handles 1.25” eyepieces. I upgraded the diagonal to a Revelation 1/20th Wave 2” one but only for the rigidity and optical improvement (which was significant). So in my case, I’m not worried about 2” EPs because I never expect them to work anyway (although I do have a GSO Superview 30mm, which works well with no significant vignetting).

On 05/05/2022 at 18:49, Mr Spock said:

My 12" needs flocking. It won't get to see this paint, not at those prices. The paint would cost as much as the scope!

You’ll only need to paint the area directly opposite the focuser and just the small length of the tube base that is visible from its reflection in the secondary mirror.

On 05/05/2022 at 06:06, Alien 13 said:

Nice, have thought about getting some of that paint for the focus tube of my Mak. maybe it will then transform into a "Questar" 😀

I imagine that paint would be brilliant for camera lens hoods too.

 

Alan

I have recently painted the inside of the baffle tube for my Mak 180 Pro with the paint mentioned in the original post.

I was pleased at the very neat job that I did, but to be honest it has made absolutely no difference (thankfully it didn’t make it worse!). So it seems that at the very oblique angles that light strikes a Mak baffle tube, this paint offers no benefit. 

So don’t bother doing this on a Mak.

I may have an attempt at flocking instead at some point in the future - there is just about enough room in the Mak 180 if the flocking material isn’t too thick and will stay stuck down.

1 hour ago, F15Rules said:

It's often been said that single high power, medium and low power eyepieces (or a good zoom and one wide field low power eyepiece eg 24mm-32mm) could give you all you need for many years of observing..

But I note with interest it’s normally stated by people with vast eyepiece collections! 🙂

If you quiz those wise only sages that say “you only need three powers - high, medium and low” it unravels pretty quickly:

• What do you use for your low-power eyepiece? “Oh… Well… I split that across two eyepieces actually”
• What do you use for high-power? “I have just one high-power eyepiece… Plus a special extra-high-power one for truly exceptional nights, but that’s not really in the collection”
• - and medium-power? “I only use my 12.5mm wide field… Although I do have a 12.5mm ortho on standby if I need to pick out fine details… - and a 9mm one…”

- and so on 😁