Piero

Thanks ☺️ I'm 1.76 m tall and the eyepiece is right where my eye is, when the telescope is vertical. I have a ladder with 3 large steps, but this is used for sitting until the adjustable chair is ready.

My mirror is 1.5" thick. I start the fan at the highest speed when the telescope is still inside. So, I "wheel" it out, then go back inside to get better clothes, then go back outside with eyepiece case, collimate the telescope, and start observing. At this point I reduce the speed of the fan by half - the views are already acceptable (that's about 1/2 h fan on). Within another half an hour I might switch it off or just leave it at low speed, depending on how the night temperature goes. P.S. grip material on wheelbarrow handles is now yellow (black looks cool, but invisible at night time). Wood blocks for making that step ramp were a very temporary solution. I now use the following: Next step is to make a good adjustable chair to be used with both the refractor and the dobson.

My 16" F4, but also my 12" F6, regularly show far more details than my 4" Tak DF. The refractor "wins" on wide field (3" Deg Vs 1 Deg fov) and solar observing (only possible with the refractor). Side note.. comparing top notch refractors like Tak, TEC, TV against low-end commercial dobsons is unfair. The optical quality is a major component, but there are other critical aspects in a newtonian telescope which must be considered to make it really fly.. at least the following: collimation (process+telescope mechanics for retaining it), mirror cell supports (back+side), mirror cooling, focuser quality, baffling, thermal currents, and (drum sound..) boundary layer above the primary. Whilst working on most of the list above reduces imperfections to a level in which these can be invisible to the eye, the last one can play like a "turbo" for magnification. After testing this, I really agree with the statement that a lot of the reported atmospheric seeing issues are actually 1-2" above the primary mirror surface. As an example, the mirror box of my 16" is 11" deep and open at the back (Kriege design). Observing the moon, ~300x seemed the highest I could go before the image started softening. After pulling up the light shroud for 5-6" (this is enough to move the boundary layer away, as the mirror box is shallow) from the mirror box and defocusing the image intentionally, I could see substantial air turbulence going towards one direction (the warm air was blown away and moved up). Note that, this air flow only affects the air above the mirror surface, not the mirror side wall! An air flow directed at the mirror wall can impair the temperature across the mirror causing astigmatism and spherical aberration (tested on the other dob). After refocusing back, the image was getting better and better as the air flow stabilised.. the limit of 300x was pushed forward to about 650x (crisp). The images was still acceptable at around 800x (yeah.. viewing craters and details like from an Apollo spacecraft). What about stars? Thin diffraction cross on the bright stars, otherwise stars were pin points. Globulars? M13 or M3 at 300x were bright, with pin point stars all over and kind of star dust (not a diffuse cloud) near the core.

Yeah, the 24 Pan is another great eyepieces (currently my only TeleVue!), not ideal for observing the Moon, but lovely for other things (like star fields). You made a good point regarding on/off axis. Both AMD and RD are off-axis. Not everyone observes planets or double stars off-axis.. In a dob at high power, one could end up observing the target at the edge to avoid constant nudging. I am aware of that link, but I am not sure whether it is fully correct regarding AMD / RD. In fact, the text calls RD as positive distortion, whereas AMD as negative distortion, letting one feel that they are kind of opposite. As far as I know, both can be positive or negative. For example, regarding AMD, if positive the image is "magnified" on-axis, and "minimised" off-axis, whereas negative AMD is the other way around. Not sure how common negative AMD is. Regarding RD, it is easier to think as if the image is projected on a sphere. If positive, you are looking at this image from the inside of the sphere, whereas if negative, you are looking from the outside. Not sure how common negative RD is. What we see near the edge with common eyepieces having these distortions: - AMD: the moon pretty much remains round, distance between stars shrinks - RD: the moon becomes an egg, distance between stars pretty much remains unchanged Anyway, this is a bit off topic. Personally, I would not bother too much about the presence of some AMD in this eyepiece. To me, there are more important factors (e.g. how much back focus needs, how much the view remains sharp at the high-end of the magnification range, comfort, colour tone, etc). Very pleased to hear that this new zoom will be available in the astro market. If it has the optical quality of a Pentax XW / Delos, ~ £400 does not sound much to me. The Zeiss zoom I have is out of production, the Leica zoom costs nearly two times. Zooms are great not just for slimming down, but for the added practicality of getting your favourite magnification for a certain target without having to swap eyepieces.

Although there are zoom eyepieces with a much larger range, I would not say that a range of 15.4-7.7 is narrow. All depends on the telescope focal length. In my dobson, f.l. = 1869.9mm with PC2, this zoom has a range of magnifications from 121x to 242x . When used with a VIP Barlow at ~2x, it can deliver something like: 259x - 519x . Using an spacer of 40mm, it would go from ~317x to ~614x . Yeah, I would possibly like something more for the "exquisite" nights, but I can always stick a Vixen HR if needed. Anyway, my point is that zooms really kick when a very good Barlow can be added, in my opinion. One could just use a low power eyepiece, a zoom, and a barlow, as "eyepiece" set. Minimalistic yes, but not necessarily less powerful. Some users dislike AMD. There is this long living (and artificial) statement that astronomical eyepieces should not have AMD. Being optimised for nearly lack of AMD, means that they have a lot of RD. TeleVue is a brand which goes in this direction. One of the main reasons for this is the separation of double stars near the edge. If the eyepiece has positive AMD, the separation between a pair of stars decreases as this shifts towards the edge. RD is not free of defects either, though. If you look at the moon with a 24mm Panoptic, you will see an oval as our satellite moves towards the edge. As far as I know it is not possible to correct both AMD and RD at the same time. Choices really. Personally, I like a trade-off between RD and AMD. The Docter UWA 12.5mm (nowadays called Noblex) does show AMD as well as some RD. Those who don't like AMD, tend not to like this eyepiece (not a surprise). To me, this eyepiece is one of the finest eyepieces in the market. I would call it a gem.

I had a s/h Lunt 50mm.. it remained with me just one month.. To my taste, it does not allow enough mag, so I sold it. I have never looked thought a Lunt 60.

An exit pupil of 2.0mm is a good all-around, a trade-off between brightness and magnification. In my opinion, it is good to consider it as a reference for a medium power when building up an eyepiece set, not as a rigid constraint.

That's correct. UNI19, with AOK AYO 2 head. It dries clothes incredibly well. Time to time it is also used for holding my 4" Tak.

Possibly yes. We are not snobbish, but just simple people attracted to simple things, like reading a nice book, rather than having a cinema at home and being fed by Hollywood products.

Like this? 😁 Honestly, my girlfriend is actually happy about having it in the living room as it looks nice. She only asked me not to store both this 16" F4 and the other 12" F6 next to each other!

Almost 6ft wheelbarrow handles for me. The telescope is left assembled in the living room and wheeled outside through ramps. Little effort and quick. Kind of funny that I find easier to take a 16" out than a 4" tak + its tripod!

Thanks Craig! 🙂 I replaced the original wood plate where the 4 long collimation bolts connect to, with a custom one in aluminium. Probably, not necessary, but I wanted as little as possible secondary shift in collimation. This aluminium plate was drilled and tapped at the centre and each edge. The central thread allowed me to remove the nut fixing the stud at the bottom of the spider hub. As a consequence, the plate "binds" to the 4 vanes. Regarding the Glatter sling VS whiffletree, i chose the former due to its simplicity. This is the first telescope I made, and also my first wood/metal project ever. To be honest, I never drilled a hole before this work, so there was a bit of learning curve for me. I think both solutions work without issues as long as implemented and installed correctly. Feel free to PM me if you want to see more photos about the construction of my dob.

SkyVision makes some very fine dobsons. The 16" F4 primary mirror was made by John Lightholder (very nice guy) and coated by spectrum coatings in Florida. The 3.5" secondary mirror is from Antares (the shop, not the star). Focuser is a Feathertouch. Telescope designed and made by me, so that I didn't have to compromise with anyone. Secondary spider and holder are from astrosystems, although part of the holder was modified. The mirror cell is based on a slightly modified Kriege design and includes a (real) Glatter sling. Truss attachments were design based on Highe and John Pratte's work. Mirror box has tongue and groove joints like in Teeter, but more shallow. Trunnions are based on Fiske's 22" design, although mine have a little bit more maths. Rocker box has dowel joints, design taken here and there. Ground board was custom designed by me. Light shroud is by Heather Teeter.

Not sure why 2 identical posts.. mobiles..! Mods, feel free to delete the latter one.

They are both middle size, but with different specs. In terms of primary mirrors, the other one is a 12" F6, whereas this one is 16" F4. Optics, design, and mechanics are generally different though. Here's an old photo of the 12":

Thanks John 🙂 I started testing it only recently, but it has so far impressed me quite a lot.

My new 16" dobson cooling down 🙂

^^^ I agree! My refractors are used on solar observing or grab and go, mostly. For proper DSO observing, the cannon is out 95% of the time.

Are those star nuts new or used? What is the diameter of your pole using a caliper?

Not sure how you tried to insert it, but there are tools in the bike industry which can make the process very straightforward.

Interesting. Hopefully it will work well on fast telescopes too.

Excellent review, Neil! The VIP is a great piece of equipment. In my opinion, the 2" modded version is even more useful than the standard version as it is sold. As the former configuration does not extend inside the focuser, it does not have all the focus issues of the latter. Just to balance things, as far as I know, the finding of the tak adapter to get rid of the 1.25" nosepiece is credited to @YKSE (Yong). I only started using the pushfix adapter with the docter because a) I like 2" nosepieces in medium large eyepieces, and b) it allowed me to screw the VIP Barlow into it in the same way I do with the Zeiss zoom I have ( which uses another Baader adapter). Both connect via T2.

Good set! I have the same diagonal as well as the 2" prism model. Both are very fine.

A 24mm 82 is a nice low power ep using that f-ratio. . Again, choosing eyepieces is really a personal matter. Personally, I would prefer a bigger "jump" and go from 24mm to 10mm. Then, I would choose a 6mm for a "zoom-in". Later on, something like a 4.7mm-4mm for close-up (e.g. moons, planetary nebulae, small galaxies). Said this, those 3 eyepieces (24mm, 10mm, and 6mm) would stay in the focuser most of the time. Few eyepieces means less swapping and less financial drain. Ethos, Pentax, Delos, APM XWA will all be fine. I find that that is more about loyalty to a certain brand, ergonomics, AFOV, rather than delivered quality.