Piero

In my opinion, labelling an eyepiece as premium is a bit meaningless.

If one evaluates an eyepiece as highly controlled regarding aberrations and distortion across the field of view down to F3, Televue wins hands down. They also offer the widest ranges on several criteria. Televue quality is also consistent over samples. Said this, I would not consider the eyecup of the Delos / delite lines as premium.

The optical quality of the Docter/ Noblex is not affected at f4, but shows AMD, which is not wanted by some users. 

The BCO 10mm I had was fine, but not special on axis at f6 and f7.4. Off-axis was so and so.. Bad sample? Maybe, but if so, then there are inconsistencies between samples, which suggests that the standard could be improved.

The Zeiss zoom I have is outstanding on axis, better than all the TV eyepieces I tried. It does show astigmatism off axis, and although this is acceptable to me at f6, I don't tolerate it at all at f4.

This Baader Morpheus could be called premium at f4.5-f5, but to my eye, it is clearly behind TV eps at F4.

At f10, many eyepieces are much more comparable..

In summary, to me there isn't a premium class. It depends on the telescope focal ratio and personal tastes too (e.g. regarding optical quality only - how much FOV correction is important to you).

Great report Gerry. 🙂

On my Tak, ZZ+VIP is a bit shaper than my Delos EPs and on par with the HR 3.4mm. For planets / solar / lunar observing, I prefer the combo above, as it allows me to fine tune the power for the evening. I seem to prefer the 5mm ortho and the HRs on double stars though.

On 09/08/2021 at 08:46, Stu1smartcookie said:

 It had stood in storage for many years and the primary needed some TLC . Took the mirror off and cleaned it as best as i could , but unfortunately the mirror will need a re-coat . This was not a surprise and was understood at the point of purchase . So after cleaning the mirror as best i could i used the scope for the first time last night . I have to say , i had no right to expect the view that i had ... just viewing bright stars , such as Arcturus and Vega as well as the lovely Albireo and its blue companion . The stars were all bright and if anything , although i think the mirror degradation has meant a little lack of contrast they seemed to show colour very well . The scope is well out of collimation ( i thought i had done a reasonable job after putting the primary back but a star test soon told me otherwise) . But as i didn't have a collimating device it was a shot to nothing and something that will be addressed this evening . I was shocked how a mirror, when in poor condition , can "work" so well . Now i realise that mirrors should only be cleaned when absolutely necessary !

I'm glad that you bought a new telescope, but I'm a bit confused when reading your first post.

- First of all, I don't understand why you thought that the mirror needed to be recoated. Was this suggested by the previous owner?

- if the telescope is not collimated, it isn't possible to assess how it performs.

- if the coatings are damaged, the effect is more light scattering and a dimmer field of view, due to the reduction in reflectivity.

- whether the coatings are damaged (erosion, many many scratches) or the surface is significantly dirty / dusty, the effect on the views is pretty much the same. Therefore, I don't understand your statement when you said that a mirror should be cleaned only when absolutely necessary..

- finally, don't you think that if your mirror hadn't been left covered with dust and particles, fungi etc, maybe, this recoat would not have been necessary?

There is nothing wrong with cleaning optics, it's just maintenance really.  Recoatings is also maintenance although a bit more invasive.

If done properly, there is no harm.

Regarding the central spot, I use the Catseye 1/4” white triangle on my 12" and 16" reflectors. The mirror is rotated as Craig said in a previous post.

I would also flock the internal wall, at least the area opposite to the focuser.

I assume the focal ratio is F5. At some point you might want to replace those Philips screws for collimating the secondary with hand knobs, so that the process becomes tool free.

Regarding the fan at the back of the primary mirror, well, to me it is required for cooling the mirror faster and keeping it close to the ambient temperature. However, I'm in the group of less than 1% of SGL members thinking so.. 

The cell holding the lenses is collimated by the manufacturer. You should not try to adjust that as this might void your warranty.

It is possible to collimate the focuser. Not all focusers are designed for easy collimation. Focuser collimation involves the adjustment of certain small screws in order to make sure that the drawtube is orthogonal to the light path. Specifically on refractors, the only focuser I collimated was the helical focuser in my TV-60 and the collimation was generally done with a Glatter laser collimator plus square attachment, although it can also be done on a star field. It generally reveals as unbalanced field curvature. When severe, it also shows unbalance field illumination and vignetting. Although focuser miscollimation can be a bit annoying, it does not affect the optical performance of a telescope, it the sense that you can still observe with it.

On refractors using standard focusers, I would not generally worry it, unless a star test or general observing shows otherwise.

Quick heads-up!

The seeing is incredibly steady right now over here and Jupiter looks superb with a very distinct hollow surrounding the GRS and plenty of details on the belts. The GRS is also showing some rounded features. One moon (not yet checked out - could be Io) has just started its transit.

Typing while observing.. 🙂

Telescope: 4" Tak;

eyepiece: Zeiss zoom 25.1-6.7mm + VIP barlow operating at about 200-220x

Congratulations Stu! That's a great move!

Working from offers some new opportunities. 

Wow! Excellent progress and in general fantastic images.

The image of Venus is one of the most beautiful I've seen (as taken by an amateur).

Excellent work! 🙂 

Looks very neat!

55 minutes ago, jetstream said:

Congrats!

Another milestone achieved Piero!

I see it in the 15" f4.8 easiest and most consistent using a vg sample of a KK 7mm ortho at 261x. Your right about seeing... if really high mag is needed everything becomes more seeing dependent IMHO. Dark adaptation is crucial as you say as are other things.

Cant wait to hear your sightings of those faint little lettered stars near the trapezium in M42!👍

I think you can use lower mag due to the darkness of your skies. Under my skies, I am not sure there is enough contrast to temporarily spot it under 300x, but I might be wrong.

How does the nearby faint IC 1296 look like over there? (Apparent "nearby" - that barred spiral galaxy is 256Mly distant from us, compared to the 'just' 2Kly of M57). Although there seemed to be something small and fuzzy where that object is located, I would not bet on it as it could have just been a faint star rather than the core. 

3 hours ago, jetstream said:

Rumor at the coffee shop has it that the 9mm Morph is the sweetheart of the line- thoughts?

I compared my Baader Morpheus 9mm against a Nagler T6 9mm and Delos 8mm using my 16" F4 reflector + PC2. In my opinion:

- the BM9 is as immersive as the N9

- the BM9 is more comfortable, although without spectacles, I find the T6 naglers quite comfortable..

- on-axial sharpness / contrast seem identical to me. I would say they go deep in a very similar way

- off-axial sharpness / contrast, the Nagler is better (from 50% of the fov). In particular, the BM9 shows some astigmatism (nothing terrible, but noticeable). Stars are consistently tight in the Nagler across the whole FOV

- colour rendition... well, to me the Nagler is more engaging here, as stars seem more colourful and vibrant.

- field curvature: none of them showed FC to my eye, but 1) the focal length of my 16" +PC2 is 1870mm, 2) my observing eye is only 38 years old

- chromatic aberrations: to my eye none was visible 

The Delos 8 is sharper and goes a bit deeper than both and colour rendition is excellent to me. I am not a great fan of their eye cup sliding mechanism, but maybe it's just me being a drama-queen  . My favourite eye cup design is like the Docter or APM UFF 30mm, but I'm also fine with the Vixen SLV style. Oh well, I guess I will need to adapt and get used to it.

I haven't tried he Nagler T6 9mm with the VIP barlow, but I did with the BM 9. With the latter, I have not seen an appreciable improvement which instead I've consistently seen when the VIP is added to other eyepieces (e.g. Zeiss zoom 20-75x, Nikon zoom, Vixen SLV, Delos). It was as if the VIP barlow was out of the way and the eyepiece showed a magnified field. With the other eyepieces, the VIP tends to make stars tighter, sharpening the views.. I still remember that time when I VIP barlowed my Vixen SLV 5mm and compared against the Vixen HR 2.4mm on my TV-60 observing Jupiter.. The barlowed SLV was just a tad behind, but really not much at all. At ~150x, both eyepieces showed far more detail (sharp detail) than the Nagler T6 3.5mm at ~100x. That was probably the most beautiful observation I had of that planet with that small telescope. Also the Delos responds well with the VIP.

In summary, I agree with Don that the BM works very well up to probably f/4.5 - 4.7 . Above that, they are real bargain eyepieces. Below that, one might start thinking about other options if the desire is to have a highly and consistently corrected FOV. 

8 hours ago, John said:

I'm sure the NW 17 is superb. I used to have the Ethos 17 but as a focal length that I don't personally use I thought it excessive to have an expensive "place filler" in the eyepiece case so moved that one one to a home where it would be used more often. The ES 92 / 17mm fills the space in the foam less expensively and is a pretty good experience when I do use that focal length.

Can't see the point of of investing close to £1K on another 17mm eyepiece, even if it is the best 17mm in the world,  given the use that I make of that focal length

Personally, I've given up chasing ultimates in each focal length now. Mind you that pursuit does keep the eyepiece forums ticking over

I've an excellent couple of eyepiece sets now and I'm, content. Many folks would give their right arms to own the 17.3 Delos or the ES 17 / 92 and I still have both. Got to draw a line somewhere and carry on with improving the viewing skills I think

Similar here.. With my scope and observing style, I never felt the need for a 18-16mm eyepiece. I tend to skip that range even with my zoom eyepiece. 

Last night I was out with my 16" f4 + PC2. Most of the time was spent on Cygnus and M56 in Lyra, although M57 near the zenith is difficult to ignore.

This planetary nebula looks beautiful in this telescope. This time I was not interested in its nebulosity, but in the white dwarf at its centre. This star is estimated between 15 and 15.2 mag, but the main difficulty is the presence of the gas surrounding the nebula. To decrease the apparent surface brightness of the nebula and increase the brightness of the star, high magnification is required. My Delos 6mm gives 311x. Although at this magnification a lot of dim stars become kind of more visible, after spending time observing it was clear that the gas of planetary nebula was still too bright. Therefore, I added my modded Baader VIP barlow (1.83x) and used first my Delos 8mm (427x) and then the Delos 6mm (570x). Using either these two eyepieces, I managed to detect a faint glimpse of the central star. It was not easy though. First of all, I needed to use an eye patch on my other eye to relax my observing eye. Secondly, my observing eye had to be dark adapted. This meant to continue observing the nebula for a few minutes constantly, wearing an observing hood. Although I spotted the central star in direct vision, I used to slowly rotate my eye around the nebula ring to help the eye rods. The central star is elusive. It was not visible all the time, but its visibility is heavily seeing-dependent. For instance, it was literally invisible, then it popped up for 1-2 second very faintly, and then it disappeared from my eye. I managed to see it three times last night: two times with the Delos 8 + VIP, 1 time with Delos 6 + VIP. 

It is also quite interesting to see how the M57 surrounding landscape gets populated by stars as the magnification increases.

Once indoors, I did some research and found this image compiled by Brian Skiff (Lowell Observatory) showing the nearby faint stars and their magnitude: 

Here is an amazing video about M57: 

https://youtu.be/6FSIfUYFeTM

2 minutes ago, ollypenrice said:

Ah, right, so you have a half-round router tool? I don't have one but that makes sense.

Olly

That's correct. A 25mm diameter half-round bit matching the 25mm diameter solid oak rods used for the seat and footrest.

2 hours ago, TerryMcK said:

Similar design as mine that I made in 2013 also from plywood but not birch just cheap stuff - I can't remember the original designer but think it was on a Dobsonian user group website.

The main hinge is made from a broom handle as is the location pin for the seat.

I didn't bother with a footrest as my Dob is an 8" x 1000mm focal length so not a tall as yours.

That's lovely! 

2 hours ago, Spile said:

I have a similar chair but find it rather heavy (base 8.8Kg) and I am considering cutting holes especially in the seat (3kg) to reduce weight.

How do you get on with yours in that respect.?

You built a very fine chair. Nice design! 🙂

Although I haven't measured mine after applying the finish, the total weight is about 9kg. I don't mind this weight as long as it is stable and comfortable. 

There are times when I also use it indoors for other reasons. The seats can be removed any way.

3 hours ago, ian2 said:

Your scope looks superb. 👍 

Thank you, sir! 🙂

I often think that all started from here:

7 hours ago, skyhog said:

Very nice indeed. Must be very satisfying observing with and on things you have built yourself. Always tip the hat to ATMs... 

Thank you very much! 🙂

It has been a very nice experience. The telescope, bookcase, and observing chair are my first wood (and metal if we consider the dobson mirror cell) projects.

The holes on the mirror cells were my first holes with a drill. Yeah, a steep learning curve as one has to study the physics of good designs, telescope making, but also how to use those tools. In my case those three projects were done with a drill, jigsaw, a router (both fix and plunge base), and a random orbital sander. I bought the latter half way through as I was getting bored at sanding, really. It helped me quite a lot though.

7 hours ago, ollypenrice said:

Lovely. How did you make the half-round cutouts on the reverse side of the seat back? Were they holes drilled in a plank which was originally twice as thick and then split? I'm most intrigued!

Olly

After gluing the two panels together, I cut the horizontal slots with my router using a plunge base. It wasn't difficult, only a bit repetitive.

I use a Tracer 12V 7Ah LiFePO4 Battery ( https://www.tracerpower.com/tracer-12v-7ah-lifepo4-battery-2.html ) to power a 4 channel controller which regulates the mirror fan and 3 dew heaters (Rigel finder, astrosystems secondary mirror, 2" ep which I actually use for the RACI finder). The battery is light and small. It fits in the rocker box of my 16" without any issue. I charge it two times per year, because it is advisable, rather than because it runs out.

It's a great device in my opinion. I want to get a cable to power USB devices too, but always forget..

@popeye85 30 ES 82 or Nagler 31 ("the terminagler") are big and heavy beasts. It might be fine with you, but something to take in consideration.

I personally prefer eyepieces of about 500g.

2 hours ago, Ags said:

Well, in an F4 scope a 30mm eyepiece is giving a 7.5mm exit pupil, so the F4 scope would be stopped down by the eye. So the Nagler advantage in fast scopes evaporates at long EP focal lengths...

Mm.. although what you say is correct, in practice an F4 newtonian requires a coma corrector. With the TV paracorr 2, the F4 becomes an F4.6, and the 30mm eyepiece delivers 6.5mm exit pupil. 

My eyes are not old and can definitely handle that exit pupil. My 30mm APM UFF gives wonderful views with my F4 dob + PC2. This works particularly well with OIII or NPB filters when observing extended nebulae.

In an F4, a 20-22mm eyepiece is also well suited and more general purpose. The 30mm is more of a dedicated eyepiece or when one wants a larger fov. It certainly has its use case though.

1 hour ago, JeremyS said:

Now that the scope is completed @Piero, I hope we will have threads aplenty about your experiences with it 👍🏻

Will do, but not regularly. For the time being I want to spend more time studying the objects visually at the eyepiece, rather than taking notes.

1 hour ago, Stu said:

Fabulous work Porto, all looks amazing.

I somehow missed the arrival of your 16” dob; beautiful! Did you build that too?

Thanks Stu 🙂

Yeah, I completed the 16" in April. It took 10 months of work. It was a great experience to design and make it I have to say. 

Now, it's a joy to use it. 🙂

I didn't write a thread about it because I wanted to avoid distractions. 

If you are interested, you can see the whole development on this Google photo album here: 

https://photos.app.goo.gl/DAZ8CqeRtJGe83jF8

It's an hybrid design really, with ideas from many telescope makers. 

The primary mirror is a 16" f4, figured by John Lightholder. He kindly sent me videos about his work on it. You can see them in the album above. The secondary is a 3.5" Antares, supported by an Astrosystems heavy duty spider and holder.