parallaxerr

The shorter EQ6 extension arrived today. The mount looks far better proportioned now and giving it a tap results is significantly less vibration, dare I say close to none! Let's hope that's the case in practice.

3 hours ago, andrew s said:

New clutch bolt in place and sitting on a slightly over engineered pier with the Mewlon ready to go. Still have to add the DSC.

Looking good Andrew, glad it's all sorted. That pier sure looks a beast!

I ordered from onbuy once. Waited a long time with no delivery before making enquiries. They said the item was posted but could not provide tracking. I requested a refund which was duly paid.

Probably wouldn't bother again!

On 27/06/2020 at 18:38, garryblueboy said:

I purchased mine direct from Rowan and found the packaging was substantial along with info about the shelf directly below the mount under the accessories listed 

Andrew bought his from FLO, to whose website my comment applies.

Glad he's getting it sorted now, that's what matters 🙂

1 minute ago, andrew s said:

Thanks, FLO have sorted it out for me. I did not examine the Rowan site as I did not see any need to. Interesting to note that the altitude clamp is bent in the unpacking photo. 

Regards Andrew 

I think I would have assumed the shelf came with the Nexus DSC too. Looking at the site it doesn't show the shelf under the "frequently bought with this product" section, so is easily missed.

Shame about the bent altitude knob. I do think this mount needs more robust packaging. FLO did a good job with the amount of flo-pack they crammed in, but your experience goes to show that the mount is heavy enough to make contact with the outer packaging given enough of a thump. Moulded polystyrene would be the best bet I suppose, but acknowledge the fact that Rowan are only just getting going with this mount.

Hopefully you get it all sorted asap and can start to enjoy your purchase

Hi rideway,

The azimuth adjustment knobs should prevent the mount head rotating by being snug up against the North pin. I can't see how it can rotate if this is the case.

Also, you don't want lot's of friction between the tripod and mount otherwise you won't be able to adjust the azimuth during polar alignment.

Is the North pin fitted to the tripod?

2 minutes ago, johninderby said:

The worst for vibration I found was the Skywatcher pillar Tried it with a Skytee and it resonated and vibrated so much soon replaced it with a regular tripod.🙁

There's definitely a pattern forming John. Any sort of piers or extensions are prime candidates for vibration issues apparently, that SW Pier being the longest of them all!

Pretty sure you should have the DSC mount plate @andrew s. Looks like you got a manual though, which I didn't. Maybe they haven't quite nailed the packing lists for the various combinations yet!

13 minutes ago, andrew s said:

What could this be? Regards Andrew 

Exciting times.....Enjoy the flo-pack 🙄

17 minutes ago, John said:

I have a Uni 28 and an EQ6 2 inch steel tube tripod. They seem to be about as stable as each other but the Uni 28 goes a lot taller. The EQ6 is still a good height but you need the legs fully extended with a long refractor on board. The Uni 28 legs don't need to be  anywhere near fully extended to get the mount to a decent height. The only reason you might want to use a pillar extension with the Uni 28 is to ensure that a long scope clears the tripod legs all the time, not for additional height.

I have the 8 inch pillar extension with the EQ6 tripod but I don't find that I really need it.

An EQ6 tripod plus the 8 inch pillar might be a lower cost alternative to a BB Uni / Planet for the AZ100. It does not have the looks but it is a stable tripod.

My T-Rex mount is similar in bulk and weight to the AZ100 but does not use counterweights.

 

Thanks John, shame I moved the old Celestron CG5 2" tripod on. I did so though because my setup all got too heavy, ironically here I am moving towards a heavier setup again but I accept it more now having realised that the smaller setup I went with didn't give me the views I wanted.

Tripod clearance was always my reasoning behind using extensions, I think it's needed with the current refractor but the 8" should suffice, the 16" is a bit excessive. If the Uni 28 is as stable as the 2" steel, then I may go for that but use it collapsed with the 8" extension fitted.

That's exactly what I am using, a 16" Orion HEQ5/SVP extension with machined bottom adapter and a cast EQ6 adapter in the top (machined down and painted). I noticed some movement in the lower bolts and torqued them satisfactorily in the machined adapter, but you're right - I fear I may strip the cast threads up top so I'm using knurled knobs done up as tightly as I can by hand. There doesn't appear to be any movement there though.

I hope the incoming 8" extension improves matters and if the tripod is then identified as the weak spot, a Berlebach with EQ6 fitting will be next. Uni or Planet is the question, but the picture you shared suggests even the Uni is significantly chunkier than the 1.75" steel SW tripod, at least in the collapsed position.

That's a very handy picture @Split Zygote2, it is the setup I envision - Uni 28 with short extension.

It looks far sturdier than my current tripod and extension combination and your timing of 1 to 1 1/2 confirms it is better damped. Mine was taking several seconds after a lighter tap.

I looked up the Uni vs Planet specs. The Planet is the same collapsed height as my steel tripod, whereas the Uni 28 is taller. Infact the Uni 28 with 8" extension would be slightly taller than my steel tripod with 16" extension when both collapsed. The Planet would need the legs extending to a degree to reach the same height.

Therefore it's a toss up between a Uni 28 with fully collapsed legs vs a Planet with partially extended legs......there may not be a lot in it and the lighter weight of the Uni would be appreciated 🤔 This would dictate seated observing as opposed to my usual standing though as the EP gets quite low......so if legs needed to be extended then the balance may shift to the Planet.

I'll try the new 8" extension on the steel tripod and match the BB heights to get a feel for the options.

27 minutes ago, Stu said:

I currently have both a Planet and a Uni-28, the latter on loan from FLO. I use the Planet most of the time but could try them both out to see the difference in stability.

That would be much appreciated Stu. No doubt the Planet will be better, but by how much I wonder?

In the grand scheme of things the Planet is not that much more than the Uni but I do like the look of the metal spreader for the uni that enables the legs to be "kicked out" as I read. 

@johninderby how do you find the Uni copes with the AZ100 and big red? Do you extend the legs on the tripod when in use?

The planet would be nice, but £££!

Before trying a BB tripod I've ordered the somewhat cheaper Orion Atlas 8" pillar extension (same as EQ6 but black) which is half the length of my current one. I'll try that with the steel tripod in a lower position to start with to see if the situation improves. If not it will fit on the BB at a later date.

I'm reasonably tall and had everything set up to reduce back bending as much as possible so the saddle was at head height, maybe just too much mass up high.

Can someone confirm the correct Berlebach tripod to fit the AZ100? I read it is the EQ6 version, closest I can find on FLO is "Uni-28 for NEQ-6, EQ6-R & AZ-EQ6", is that the right one?

Unfortunately I found out tonight the 1.75" steel tripod and 16" pillar extension aren't really up to the job. There's a wobble (very low frequency vibration) due to the weight of it all up high, even using the slow mo's was causing a wobble  

41 minutes ago, John said:

Clear night forecast again. A chance to try experimenting perhaps ?

 

Definitely!

8 minutes ago, vlaiv said:

Do consider that faster scopes require more expensive eyepieces to produce equally pleasing images and that longer FL scopes make it easier to achieve high mags while short FL scope makes it easier to achieve low mags. If you primary interest is high power viewing - slower scope. If you enjoy wide field view more - faster scope.

Agreed, I can make those more my primary considerations now.

To be fair the scopes I am considering are not vastly different, F7-F8 mostly so my reasonable quality EP's should cope OK. It's the resultant tube length that makes a difference to me at 130-150mm objective diameter sizes.

What is becoming readily apparent is that different people have vastly differing views on the subject and we may have strayed a little!

For me, it's simple now. When considering two scopes of equal aperture, in most cases the view at the eyepiece can be matched (notwithstanding minor optical differences) by the use of different focal length eyepieces, such that I can make a decision based on physical practicalities alone, i.e shorter faster scope is easier to handle and mount.

Thanks everyone for your input, it has definitely helped!

1 minute ago, vlaiv said:

Only when comparing two scopes with same aperture - same light gathering ability.

Not the same if aperture size is different.

Agreed, which is what I am comparing as per OP

2 minutes ago, jetstream said:

More mag at the same eye illumination in general.

Mag matters ie Blackwell and Clark and eye illumination matters as we all know.

This is pretty much it IMHO and its hugely important again IMHO.

Well that's what the FoV calculator screenshot in my original post kind of disagrees with. Same exit pupil, same mag....perhaps those two examples are too closely matched? Anyway, they are of the rough sizes I am considering so the difference appear to be negligible.

1 minute ago, pete_l said:

ISTM that "fast"-ness is purely an imaging term. Since the size of the sensor is fixed. With optics use, as you say, the two optical elements: objective and eyepiece interact.

When eyeballing, greater magnification gives more detail (and darker backgrounds)  but at the cost of reduced intensity. Wide field / low FR gives brighter extended objects, but at the price of smaller size.

Yes, fast-ness is definitely an imaging hot topic and I did wonder if I'd confused myself with that at first.

5 minutes ago, vlaiv said:

And there you go - why two seemingly same setups provide viewer with different experience.

....OK...A little beyond the scope of my initial enquiry, but interesting information nonetheless.

I guess the takeaway for me is that there are many factors to consider including variations in glass quality etc.....but most importantly my rationale behind same mag/exit pupil/FoV is sound and I'm not missing or misunderstanding something fundamental.

I can now consider the practicalities of different focal length scopes of around the same aperture, without worrying that one will be more or less suited to the type of observing I do!

An interesting excerpt from an article I saved to disk some time ago...

"The brightness of extended objects (galaxies and nebulas) is proportional to the square of the exit pupil. Therefore, a low power 4mm exit pupil (4 squared = 16) is four times as bright on galaxies and nebulas as a medium power 2mm exit pupil (2 squared = 4). To put it another way, twice the power results in one-fourth the brightness on the faint fuzzies outside our solar system.

On the other hand, the brightness of a point of light (a star) is a function of the aperture of your scope – not the exit pupil. The bigger the aperture, the fainter the star you can see. Stars do not get dimmer as a scope’s power increases and the exit pupil gets smaller. Extended objects do, however, and the sky (the most extended object you’ll ever see through your scope) becomes progressively darker as the power goes up. The result is that faint stars are usually more visible at higher powers, as the contrast between the unchanging star brightness and the progressively darker sky background increases."

It would suggest that equal magnification and exit pupil should provide much the same image between two scopes of equal objective diameter but differing focal length as sky brightness is a function of power, which by default is a function of EP focal length AND telescope focal length...

I think this calls for a multi scope, exit pupil matched shoot out.

7 minutes ago, John said:

Well it does not seem to work like that in practice

 

Maybe that's the bit I'm missing then John - that regardless of exit pupil, the sky background brightness is a function of the eyepiece focal length only?

1 minute ago, John said:

The background sky would not be as dark with the longer focal length eyepiece. I have some light pollution here and that really makes a difference.

I do have a 40mm eyepiece with a 70 degree AFoV so I can see the above very clearly when I compare the views of the Veil Nebula with the 31mm Nagler, the 40mm SWA and indeed the 21mm Ethos which shows a little less sky but darkens the background sky even more.

Also certain exit pupils are more effective when using O-III and UHC filters.

I think I would need to move to the 3 inch format to get an AFoV that is large enough to show 3.8 degrees with the F/9.

 

 

But I guess this comparison is in the same scope, correct? - The 40mm in the Tak would produce a smaller exit pupil, thus I assume darker sky background than the 31mm Nagler in the Vixen.