John

The prism should compare similarly to your mirror diagonal as it does with mine.

I really hope so anyway 🤞

Have you any idea how many mm of inwards focuser travel you need to gain to get the 3-8 Svbony zoom to focus ?

What diagonal have you been using up to now Paul ?

The 10-12mm of in focus gain that I mentioned was compared with an Altair 1.25 mirror diagonal, like this:

3 hours ago, vlaiv said:

Just went to check it - and sure enough:

What do you think is scope / mount combination in the image?

Bresser 70mm F/10 achro on an EQ5 Pro GOTO mount ?

There seems to be an erecting eyepiece and possibly a barlow in the diagonal - not much use for celestial observing !

1 hour ago, RobertI said:

My suggestion is to see a “two in a view” where Jupiter, Saturn, Mars or Venus can be seen in the same field of view as another well known object such as a DSO. I remember seeing Venus lying in the Pleiades and it was a spectacular sight. 

"two in a view" are great targets, especially where one is easy and the other more difficult.

Messier 13 and the galaxy NGC 6207 are a good example and about 1 degree apart so visible in the same eyepiece view.

Messier 97 (planetary nebula) and galaxy Messier 108 are a little further apart but possible with a wide field view. The O-III filter that helps see M97 does the opposite for M108 though so that's a challenge.

4 minutes ago, John said:

....One of the "Sky at Night" presenters was once posed beside a scope on an EQ mount but with no C/W shaft or weights fitted !

I can't recall who it was though 🙄

It was Maggie. No finder either !

I thought NP101 with it's dew shield and focuser fully extended.

The Skywatcher type tube rings don't help - it is much more common to see TV scopes in their black tube clamps.

Scopes used in photo shoots are often messed around with by photographers who don't know one end of a scope from the other but think they know what "looks good" 🙂

One of the "Sky at Night" presenters was once posed beside a scope on an EQ mount but with no C/W shaft or weights fitted !

I can't recall who it was though 🙄

Seeing the zodiacal light seems to be pretty challenging. No scope needed though.

Naked eye comets - Neowise was superb and Pons-Brooks has just about got there. Could do with some more 👍

They seem good value for their specification 🙂

The shorter focal lengths have good eye relief, which is more than can be said of a shorter focal length plossl.

Very promising I think 👍

- Dust lanes in a galaxy. Lots have them but, personally, I've found them quite difficult to see clearly. 

- DSO's in another galaxy. NGC 604 in Messier 33 is an obvious contender. Some of M31's globular clusters are observable visually as well.

- Although it's been downgraded, for some of us of a more "vintage" age, actually seeing Pluto has a certain appeal to it 🙂

Quite close to the figures that I had for my Orion Optics 12 inch F/5.3 which had Orion Optic's mid-ranking optics. Good optics. Probably a little bit better than the average chinese made primary mirror. 

23 minutes ago, saac said:

Do we need an emergency alert sticky banner along the lines "Get Out And Look Up Now - No Seriously Do It" Maybe with an audible alert along the lines of the Enterprise Battle Stations.

Jim

I found quite a few positive reports on the Celestron branded (China made of course) prism diagonal - the one with the part number of 94115-A.

They chimed with good experiences I had quite a few years back with the same diagonal which came with a C5 scope that I owned back then.

Given that the scope that I wanted it for was F/16 I felt that the risk of 20 quid for the thing was worth taking. It's not in the same league build-wise as my Baader T2 Zeiss prism of course but that cost more than 10x as much !

I probably won't be comparing these two, in case the 20 quid prism performs just as well as the 200 quid one 😉

So far though the cheapie prism has done fine in the undemanding long refractor. I have replaced the chromed set screws with nylon ones to give my eyepiece barrels a chance though 😬

Spotting a bag of tools let go by accident by an astronaut working outside the ISS 🙂

I think that has happened twice now.

Just thought of another one:

- Spotting the central star in Messier 57, the Ring Nebula.

8 minutes ago, wookie1965 said:

Hi John is that inward travel.

Yes - the prism diagonal uses 10-12mm less of the light path of the scope so eyepieces focus that much further outwards / you gain inwards travel.

We have been talking quite a bit lately about a couple of observational astronomy challenges, namely:

- Seeing "the Pup Star" Sirius B

- Spotting the E & F members of the Trapezium group of stars in Orion

I thought it might be useful to start a thread on such challenges which might, over time, build into a useful memory prompt / suggestion box for the visual observers amongst us.

I'm intending to stick with challenges for the visual observer rather than for EEVA and similar approaches, which will have their own boundaries I'm sure.

To get the ball rolling I'll add a few more to the ones above. Some tougher than others, some more personal challenges rather than "classic" ones, and quite a few of course will have already been achieved by observers on SGL:

- Spotting the Encke Gap or Encke Minima in Saturn's A-ring

- Spotting Saturn's C-ring or Crepe Ring

- Seeing white spots in Jupiter's cloud systems

- Spotting the Martian moons Phobos and / or Deimos

- Seeing Neptune's moon, Triton

- Seeing some of Uranus's 4 brightest moons (all still rather faint !)

- Splitting Antares

- Spotting quasars

- Splitting Zeta Herculis

Please feel free to add some more of your own - the more the merrier 🙂

12 minutes ago, wookie1965 said:

Is the light path shorter in a prism diagonal than a mirror diagonal. My Svbony 3-8mm wont focus in my Vixen 102m.

Yes. I recently picked up a cheap Celestron branded 1.25 inch prism diagonal for use with my 75mm F/16 refractor and gained around 10mm-12mm of focuser travel. The optical performance seems quite good too.

On 02/04/2024 at 19:38, Flame Nebula said:

Hi, 

I'm wondering if this is within range of an 8" newt. 

Triton should be, on a good, dark night.

The moons of Uranus have so far eluded me at apertures less than 12 inches. Even the brightest of those is a magnitude fainter than Triton.

Edit: apologies, I realise that I've to some extent repeated what I posted earlier in this thread - I lost track !

Pentax XW's and Baader Morpheus have very good performance, generous eye relief and a wide AFoV. The Svbony 3-8 zoom is very good optically but the eye relief is too short for many glasses wearers I would think (I'm not one).

@Stu is quite right about the seeing being a very important factor in these challenges.

Another one, IMHO, is recognising that you are actually seeing something. That might sound an odd way to put it but these tougher challenges don't just pop into clear view when you get the goldilocks aperture / seeing combination. They go from being just beyond the threshold of being seen to just being on the right side of it but still can be very transitory, fleeting, vague and barely sensed rather than a "clean spot". With my 12 inch dob under the right conditions, E & F were so clear you simply could not miss them. With the ED120 under middling conditions, they could be hard to spot, especially F. 

So as well as "seeing, seeing, seeing" I would add "practice, practice, practice". Your 127 mak is up to these tasks I would think - you just need to keep at it, and at it, and at it ........ 

Challenging lately with the volumes of cloud and rain that we have experienced in the UK of course 🙄

Plus, the Orion and Sirius "season" is nearly over now of course.

52 minutes ago, IB20 said:

I have an 8” dob and seen E & F stars - not particularly challenging if transparency is good.

Sirius B in theory should be easy but I haven’t managed it yet. Found the scope fails to acclimate and control the roiling mess of light that is Sirius. I’d fancy my 4” or 5” APOs would be better suited for this split.

They are not quite equally difficult tasks from my experience. Spotting Sirius B is the tougher one and very much seeing dependant. Of course the further north you observe, the harder Sirius gets. 

Lovely drawing Mike, as usual 🙂 👍

56 minutes ago, John said:

Quite nice here. A little hazy perhaps but a good double star night, currently.

Best split tonight with the Elliott 3 inch refractor was Iota Leonis. Here is what the Webb Society's Bob Argyle said back in April 2017 about this uneven brightness pair:

Webb Deep-Sky Society: Double Star of the Month: Iota Leonis (webbdeepsky.com)

Pleased to get it with the 3 inch tonight at 171x. Secondary was close in but clearly split and more or less due east of the primary. Quite testing for sub-4 inch aperture scopes I reckon.

Quite nice here. A little hazy perhaps but a good double star night, currently.

Class Brass this evening 🙂