John

Baader Optical Wonder fluid applied via a micro fibre cloth will clean the corrector:

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1 hour ago, Deadlake said:

.....Visuals decline is IMHO light pollution….

I wonder though if threats such as light pollution and overcrowded skies (satellites) pose a challenge for amateur astronomy generally, whichever way you choose to pursue it ?

In that respect, there is more that binds all of our interests together than sets them apart I feel. We have a common bond of a love of space 🙂

7 minutes ago, RT65CB-SWL said:

...The Russian space agency during the 1970’s / early 1980’s managed to land some probes [Venera / Венера] on the surface of Venus with great success and got some images and data during the later missions. Even though they remained operational for about one hour, I don’t think NASA or any other space agency has even attempted that amazing feat.

I agree that there have been some really notable Russian space exploration achievements 👍

I am currently reading the excellent book by Dr Ezzy Pearson "Robots in Space" which documents the history of robotic space exploration. Very interesting.

Many years ago I had a C8 SCT which suffered from mirror flop. It was an older one though. Annoying even as a visual astronomer. When the collimation was accurate the scope performed excellently and showed me some of the best views of Saturn that I've ever had. But when the scope moved past a certain angle you could actually see the collimation slip out of alignment and the sharpness and contrast just vanished 😬

Great report @Stu 🙂

I'd like to try that approach with my 11x70's. I can fit 1.25 inch filters over the eyepieces so it will be interesting to see what impact an O-III on one side and a UHC on the other has with those.

I suppose "crashed" could be re-defined as "entered exceptionally low level geostationary orbit followed by widespread surface based hardware deployment" by the PR people. 

I've seen the "sweet spot" also called the "coma-free field" and the "diffraction limited field".

I found these references on another forum which I think are relevant:

Again from Nils Olof Carlin:  

"The allowable tilt of the focuser axis as measured on the primary (e.g. with a laser spot) is some 1/25 of the primary's diameter (actually, the focal ratio is eliminated in the expression) - here, the defocusing from the tilt of the focal plane is negligible compared to the coma everywhere within the FOV.

For an F/5.5, the "diffraction limited field", or more accurately the field where the Strehl ratio is not lowered more than 0.2 from its maximum, is some 3.5 mm diameter...."

and from another poster:

"As far the size of that "coma free" field, watch out, because there are two common criteria; one for the "photographically acceptable" field for prime focus photography (where the comatic spot size in the Newtonian focus reaches typical film resolution, 0.025mm), and one for the "diffraction limited" coma-free field (where the comatic spot size reaches the size of an Airy disc).

The latter dimension is much smaller."

11 minutes ago, paulastro said:

....This myth is encouraged to some degree by magazines and astronomical retailers advertising very expensive imaging equipment.  It's a good business to be in - selling equipment most of which will soon be out if date or incompatable.  Indeed, apart from the telescope or lens used, if its kept long enough it becomes worthless.....

 

That is an interesting point. 

One of my scopes is well over 20 years old now, another two are over 15 years old. My youngest scope was made 7 years ago. A number of my eyepieces are 20+ year old designs. 

I'm not good news for the astro retailer I guess ....... 🙄

It's worth noting that the collimation "sweet spot" gets progressively smaller as the focal ratio reduces. This is from Nils Olaf Carlin writing for Sky & Telescope magazine:

"Surprisingly, the size of the "sweet spot" depends only on the main mirror's focal ratio (the mirror's focal length divided by its diameter) and not its size. For instance, even a perfect f/4.5 mirror, small or large, can provide "diffraction limited" performance only within a 2-millimeter (0.08-inch) circle at the focal plane. An f/10 paraboloid's sweet spot, by contrast, spans 22 mm (0.87 inch). (For the mathematically inclined, the sweet spot's diameter is proportional to the cube of the f/ratio.)"

Because of their proportionally larger secondary obstruction and very "fast" primary mirror (usually F/2 or F/2.5) I believe SCT's are even more sensitive to collimation errors with contrast and sharpness declining markedly when collimation is "off". On the plus side, SCT's tend to hold their collimation better than newtonians once it is correctly adjusted. 

25 minutes ago, paulastro said:

I often talk to the Moon sometimes when I'm observing it, but please don't tell anyone else!

I wink at it. Twice actually. Once for Neil Armstrong (his family suggested this after he passed away in 2012) and once for Sir Patrick Moore who spent so much time studying it.

Silly I know, but there you go 

Nice report Ian 🙂

We are often down on the levels for birding. It's a great place 🙂

They have an active astro society down there:

Somerset Levels Stargazing welcome page (somersetlevelsstargazers.co.uk)

Maplin aluminium cases lined with pluck foam, generally. I seem to have acquired 5 of the things now.

With my old 12 inch dobsonian, the closest focus I could get (without a ridiculously long extension tube) would be around 100 metres away. It would have been interesting to find out what my neighbour a few houses down the road would have said if he had caught me nailing a ruler up on a tree in his back yard. I guess the phrase "It's OK, I'm an astronomer" would have explained everything 🙂

This is worth a look:

Thierry Legault - The collimation (astrophoto.fr)

I think accurate collimation does matter but the differences are seen when pushing the optics towards their limits. Many folks don't push that far so maybe don't notice any improvements 🤔

7 minutes ago, badhex said:

Honestly, no joke - I wrote this yesterday without reading the review. Have now seen the review itself - 4/5 score 😂

I wonder what they have to do to get a 3/5 in S@N ? 😬

This film dates from 2009 but much of it chimes with me. It also features a few of folks from Bristol Astronomical Society including the very much missed Eddie Carpenter:

24 minutes ago, badhex said:

Cheers John. Absolutely, and will be the first to admit I've never collimated a frac and although I understand the general principle, it seems like a terrifying task! I had a crack at it at the time of repair, but it was likely not a very good job! 

I've found the most useful tools are a collimated laser collimator, which is used to check that the focuser optical axis co-incides with that of the objective, and a cheshire eyepiece to check for objective tilt.

The 1st phase involves putting the laser collimator in the drawtube (no diagonal) and seeing where the laser exits the objective lens. It should be pretty much dead centre. If it is not, the focuser needs to be tilted slightly to get that laser in the centre of the objective.

The 2nd phase needs uses the cheshire eyepiece. Again with no diagonal, put the cheshire in the drawtube, illuminate the 45 degree angle face of the collimator and look through the collimator. Ideally you should see 2-3 circular reflections of the collimator face reflected back from the rear of the objective and they should be pretty much on top of each other. If they are separated, the tilt of the objective needs adjustment.

In this image the cheshire is being used to detect focuser tilt or objective tilt. If you use the laser to check / adjust focuser tilt first, you have eliminated that so it is just objective tilt that you are testing for with the cheshire:

Interesting report 👍

I think I would be checking the collimation of the scope as an early measure.

I think the objective cell on those can be collimated.

6 minutes ago, PeterStudz said:

I guess that what I’m trying to say is that in the future you might be able to do it all - visual, AP, EAA - without realising it’s one or the other.

 

That is quite possibly correct. I hope there will remain some distinction though, especially when things are reported. I've very recently read a report (not on SGL) which mentioned "seeing" and "observing" a number of the brighter Cephid Variables within the galaxy M 31. That caused a little confusion because it was my understanding that such targets were beyond most amateur telescopes in terms of visual observing, the brightest bring around magnitude 17 I think. It turned out that the reporter in this case had been referring to seeing these variables on long exposure images they had taken with their scopes. 

3 minutes ago, MalcolmM said:

My phone camera and technique are probably not helping!

I actually find the Kitakaru much easier to look through than the Nagler, but they are very different eyepieces with very different focal lengths, so probably not a fair comparison. 

Malcolm 

Well thanks for trying Malcolm.

I agree that the Nagler 31 does take a little getting used to. Likewise a number of other ultra and hyper wide eyepieces that I can think off.

I am rather astonished at the retail prices that the top end Tele Vue eyepieces have reached these days. I paid £200 for my N31, pre-owned but that was many years ago now. 

I've absolutely nothing against imaging or EAA but they are not for me I'm afraid.

If the LP gets so bad that I can't get satisfying views with a simple scope, an eyepiece and a star chart then I would stop observing.

2 minutes ago, cajen2 said:

The Nagler image is nothing to write home about for the price of the EP.....

They work very well with scopes under a night sky though, I hardly ever look at rulers with my Nagler 31 these days 😉

Even if you don't see the spiral structure in M33, it is worth looking out for a small smudge of light close to a foreground star a little away from the core of the galaxy. That is NGC 604 which is an immense star forming nebula within the galaxy M33. It is quite something to be able to see a deep sky object that is in another galaxy 🙂

This Sky & Telescope article covers how to see this one plus a couple of others in M33. 

I have seen NGC 604 with my 100mm refractor so your 10 inch should be able to spot it relatively easily 👍

Low magnification and a wide field of view for this one.

On 17/08/2023 at 06:08, Gabby76 said:

With these being 4 element in 2 groups I am not surprised that there would be colour and artifacts along the EOF. 

Symmetrical work better at 50-55° AFOV.

You would need to be using a long focal length telescope since you get a exit pupil of 7.7 when used in a f/6 telescope.

The 45 mm  would work in my f/15 as that gives a 2.95 mm exit pupil. 

My F/6 scope would probably be the one that the eyepiece would see little use with. 

I do have the Nagler 31mm and Ethos 21mm already which give very wide fields with more modest exit pupils. I was just curious about the Kitakaru design 🙂

My 12 inch dob was in tube rings so I could have the focuser at whatever angle I liked. After some experimentation I went for this:

I observe standing using my left eye and I am left handed. 

I got the finders and focuser positioned so that I could shift between them with minimal head movement.

It worked well for the 10 years that I owned the scope.