Giles_B

2 hours ago, Louis D said:

Try a #56 green filter to block unfocused red and blue wavelengths on bright planets to see if it improves overall sharpness.  It sharpens up Venus tremendously for me.

Yes, blue worked well for me on Venus too (didn't try green) - not sure why I didn't play with filters the last couple of times. I'll make sure I try it next time. I didn't find brightness was a big problem once I'd got to high magnifications.

Has anyone had good experiences using an atmospheric dispersion corrector? The way my Newtonian is now set up I use a 3.5" extension, so I have a *lot* of potential in-focus (which seems to be the major barrier to using an ADC on a newt).

Another year, another planetary observing season - I've managed to get out a couple of times this month in the small hours for an hour or so. I've worked out I can manage about an hour between 1am-3am and still work okay the next day if I get an early night and don't have too early a start.

As with the previous two years, I'm off to an enthusiastic start, but I'm plagued by the muddiness and lack of detail in the views I'm getting. DSO views are fine, although they lack contrast when I observe in my Bortle 5 garden. They are better when I get to the countryside. But planets... Last night I felt I could make out Jupiter's banding but not much else. After 45 minutes at the eyepiece I could barely make out the Cassini gap on Saturn, just a faint hint of the gap coming and going at the ring edges.

I'm using a 10" Newtonian (an Orion Optics VX10, mounted on a dobsonian base). I have had very good views of the planets, but only on 1 or two nights a year where the seeing has been exceptional. Mostly the visuals are annoyingly muddy.

I find myself ticking off the list of things that might be contributing to dull views, and what I might do to help make them better. I once suspected that my collimation might be a problem, and I'm now absolutely sure it is not. Laser collimation is bang on and confirmed in star testing. The other culprits may be the generally limited time at the eyepiece, poor seeing and the mirrors themselves.

By limited time at the eyepiece I mean limited both in session length (usually not more than 90 minutes) and limited quantity of sessions (maximum four per month). I try to spend a lot of time physically at the eyepiece, but inevitably pushing the dob means that I occasionally lose the target at high magnification. 

Seeing-wise, there are not many stars in the sky to the naked eye and they generally show atmospheric wobbliness. Bristol isn't very high above sea level so the atmosphere is pretty thick. The planets shimmer about a bit in the eyepiece once I get to around 13mm.

The primary mirror looks in good condition. I cleaned it using the suggested methods (slightly soapy water, gentle wiping with wet cotton wool and rinsing with distilled water) last time I took the scope apart to fit a new focuser. There are a few very light scratches (I fear I could have caused some when I cleaned it) but nothing that leads me to think they may be causing the problem. The mirror seems bright. A label on the mirror side dates it to 11/07/08 - so a good 15 years. I haven't given as thorough attention to the secondary, but it seemed bright when I dismantled the scope.

Is there a way I can improve the visuals I'm getting? As I see it the options are:

1. Invest in some sort of EQ tracking system. For a 10" newtonian an EQ6 will be necessary, which feels like overkill for visual. However, there are some EQ bases for dobs - could this help me to stay at the eyepiece more and fiddle around finding the target less?

2. Recoat the mirrors: While I don't see an indication that I need to coat the mirrors, the coatings are 15 years old and show a bit of use (i.e. the light scratches) - could recoating potentially give a minor boost to the contrast and improve the planetary views?

3. Use an atmospheric dispersion corrector: I only became aware of these in the last 12 months but I'm aware they are used for visual as well as well as AP - could this help given that Jupiter and Saturn are generally low or low-ish in the sky?

I do realise I should take in the usual caveats - that I am expecting too much from the actual conditions. That if I want amazing results I should do AP... etc. so these are not the answers I am looking for - I do enjoy visual and love the time I get observing. But like most amateurs, I just want to push the envelope a little bit further. Do let me know your thoughts.

Ditto that - last year I bought my Nagler zoom second-hand from a seller in the USA through Astromart. I paid $350 (£290 at the time) for the zoom, but then had £75 of fees added for customs and import.

There was no UK stock at the time, so saving money was not the primary motivation, however, the total came to close to the price of a new zoom (£400 at the time) once customs was factored in.

2 hours ago, LDW1 said:

If you are thinking my post(s) remember the old time worn saying ' if the shoe fits then wear it but if not don't ' !  Tar !!  Really ?  But many, many, many don't think your way in any of these types of forums / posts and I really can't figure out who they think they are, who they think they are talking to, this is supposed to be a broad, fun hobby ! 

I agree - 'horses for courses' as we say in the UK. It should go without saying that what is 'dull and monotonous' for one person is another person's all-consuming interest - and quite right too. All that diversity brings a lot of extra colour and interest to us all. The world would be pretty boring if we all liked the same things.

ZWO posted on the FB group that shipping is still on track for late August with first units arriving in our sticky hands by September

I think it might be simpler than that - the impression I get is that the software will plate solve and, since the mount is alt-az there is no polar alignment (derotation of the images will be accomplished using software).

However, @Rileybowler there is not a great deal of info on this scope and people are mainly getting excited because the spec is high and ZWO have thus-far produced good equipment. No reason this scope could not be a clanger though. You are pricing in a risk to preorder and get one at a promotional price now (offer closes today) - you may want to spend £100 more and get some reviews and give the software time to mature.

Certainly this device is marketed at absolute beginners, however, at least initially (a pro- mode for the software is promised), it will totally automate the process. The question is whether that is the right entry level for astronomy. In my view the s50 fills a niche (allows imaging of DSOs which are otherwise very faint, hard - or downright impossible - to see, and visually unimpressive on first blush) however it will not allow you to directly interact with the sky, won't give much sense of where you are pointing or how the stars are laid out. For me these two are important reasons why I continue to enjoy visual astronomy - there is a sheer wonder in finding and looking at an object in the eyepiece, seeing what detail you can pick out and feeling like you are having an interaction with it. I gradually learn how the constellations are laid out (albeit aided by a celestron starsense unit), what the lunar phases are and what to look for at particular times, what times of year I can spot the planets, how the seeing varies from one hour to the next.  I'm not sure the S50 will give a novice any of this.

But maybe I'm too focused on how it works for me. Certainly as a one-time purchase the S50 is likely to do a lot.

Edit: just realised I may also have given the impression that the S50 will allow detailed visualisation planets - it won't - only the moon and sun will be large enough in this scope to see any detail.

New since when? Most of it is excited speculation on the Facebook thread. Dithering, access to unstacked subs in FITS and the availability of a replacement battery was confirmed on 19th July.  AT some point it was mentioned that a combined Ha and OIII filter was included. Today's news is that potentially a solar filter is now included as well as standard (potentially because they are asking for 1000 total facebook shares of this information by 31st July to do this). Other than this, it's just the usual teasers of photos from beta-testers. The DSOs look impressive to me (a non astrophotographer) at this spec and price point - I'm less sold by the solar pictures, but that's because I already have a good visual solar setup. Certainly if the DSO views posted are the norm I will be very satisfied with these as a sort of camera assisted EEA for faint DSOs (which is most of them from my garden).

Incidently I am not on Facebook either. Checking the ZWO s50 owners thread on Facebook is made easier by using duckduckgo as a browser - on chrome I get locked out by a demand to login to Facebook.

Update 27/7: the solar filter is now definitely included (they got their 1000 shares - mainly spammed over the ZWO s50 owners thread!) - applies to all orders whenever they are/were made.

4 hours ago, Louis D said:

I had kind of thought you had saved up enough for the Terminagler.  Since the S50 is $300 less than the Terminagler, I figured you had enough to pick up a 30mm APM UFF for $200.

Okay,, I understand - thanks for the recommendation. I hadn't saved enough for the TV, so no cash to spare for now, but I'll bear APM in mind going forward.

2 hours ago, Louis D said:

Unless you're dead set on the last 6mm of field stop diameter and 9 degrees of AFOV, I'd get some variation of the 30mm APM UFF.  I much prefer it to my 30mm ES-82 for many reasons (lower weight and bulk, greater eye relief, near perfect edge to edge sharpness, lack of ring of fire, etc.).  That, and you'll save a nice chunk of change.

Hum. My reasoning for that particular item was that I love my 20mm T5 Nagler, and I really don't enjoy my 34mm ES 68. Admittedly the reasons are a bit superficial - ES eye guards are flimsy and I get frequent kidney beaning, also compared to my Naglers I find the ES relatively low contrast in local bortle 5-6 skies. All things I can live with, but would rather not. The big Nagler seemed an obvious, if expensive, choice. I did consider the Panoptic.

It's moot now, the cash is spent on the s50. It'll be a good six months before I'm anywhere near the next big astro buy - hopefully I'll see the s50 before that!

Just taken the plunge and preordered an S50 from Flo.

Was saving for a 31mm Nagler - but family and work pressures, plus the endlessly cloudy weather seem to be conspiring to keep me away from the night sky at the moment (even solar is a bit dicey).

I'm hoping a easy eaa setup will let me scratch the astro itch a bit more regularly.

13 hours ago, PatientObserver said:

I most recently bought the Pentax XW 30. Makes scanning the sky so much easier. Might not have needed the finderscope afterall. Will likely get the 40 mm eventually, but I need to build up the astronomy savings account again.

How do you build up an account? I started an astro savings account, but I keep spending it before gets into 3 figures!

Yep, fully agree I'm just looking for trouble. That's what these short cloudy nights have driven me to!

1 hour ago, vlaiv said:

One of distances is related to resolving the small opening of artificial star - your being 50 micron star.

Other has to do with spherical aberration.

You can calculate first distance quite easily - look into what is resolving power of your aperture and then look at which distance star presents angular size that is smaller than this value.

For spherical aberration - things are not quite as easy as you need to understand quite a bit of optics to calculate that one - but it boils down to this:

Point source "radiates spherical wavefront" around it. When this wavefront hits aperture - it is slightly bent. When we look at objects that are far away - they are effectively at "infinity" as far as numbers are concerned - and that sphere has infinite radius and thus is almost flat - we get flat wavefront. This is what we want, and what the scopes are optimized for.

If our point source is not at infinity - it will introduce some level of spherical aberration to the wave front. When you examine image in telescope - you won't know how much of spherical aberration comes from telescope itself and how much is from the fact that source is close and not at infinity. Closer the source - more spherical aberration there will be (ratio of distance to aperture changes - so part of sphere changes - this is because aperture is fixed but we change the distance).

at some distance this spherical aberration induced by closeness of the target gets very small and can't be detected and won't affect results of optical tests. That is the second distance at which you need to place artificial star if you want to check for spherical aberration of your telescope and want to get accurate results.

That is the clearest explanation I could wish for! Amazing

certainly the image looked similar to the aberration caused by the spider @pipnina - and i'm reassured by vlav's point that it is unlikely pinching is even across the mirror. However I will take another look with these answers in mind - if nothing else it gives me something constructive to do with scope when the cloud comes in!

I have become the proud owner of a Geoptik artificial star, and got a chance to try it out a few days ago.

Testing the collimation of my 10" dobsonian from a distance of 23m away from the (50 micron) star showed a good pattern of concentric rings, but unexpectedly the circle of the airy disk was not perfectly round, but a bit more like a 20 pence piece.

Somewhere in my mind the cogs began to turn and I eventually remembered (a few days later) that an off-round airy disk of this sort was the result of the mirror being pinched. In the last 9 months I've changed my old 3 point mirror cell to one of the newer Orion Optics 9-point cell.

Now I've been wondering if I pinched the mirror when fitting it to the new cell - although I have generally felt the mirror has some play in the cell, rather than being tightly held (I can hear it shifting slightly when I take the scope out of the dobsonian base and lay it flat - and vice versa)

However the artificial star has two distances quoted for testing for a 250mm aperture - 21m and 1km - the smaller distance is for collimation and the latter for testing optical quality (or so I believe - I'm a bit sketchy about why there are two distances!)

So before I strip the scope down again to test the mirror, I was wondering if what I am seeing is an artefact of using a very close light source, rather than a genuine aberration in the optics?

Wise thoughts and explanations would be very welcome!

Apologies for this very belated follow up to the original post.

It took a long time to get the part, the original shop going incommunicado to my emails, more shopping around and finally finding a second well reputed local engineers who specialise in making custom parts, but at a much higher quote than the original one, which meant further saving and delaying.

After some discussion they recommended keeping thing simple with a connector that would attach to the M68 adaptor. This meant that the adaptor could stay short and achieve maximum robustness at minimum length. I was happy with part when it turned up, and it mated the two parts well - the little movement on the telescope side disappeared after painting the part:

I've now had the part about eight weeks. Initially had to return it for a skim of the inside diameter so there was better side to side movement of the focuser to allow collimation. As you see on the photo the collimation is not quite there when checked with a laser, but there is no splitting of the laser as it passes through the objective, nor is any miscollimation visible to me on a star test. In any event my experiments with realigning using the adjustment screws on the focuser have shown it is tricky to achieve a better result than the one shown.

The scope is well balanced despite the extra weight of the Steeltrack focuser, and the most important result - to achieve more in-focus with this excellent scope, has been achieved very nicely - I have a massive 35-40mm more in focus and am able to achieve focus even with my Naglers (although they aren't well suited to the usual seeing conditions of solar observation). After painting the part with blackboard paint inside and out, I am also very pleased with the visual appearance as well as the performance

I think there is a false dichotomy here between using push-to / go-to to assist finding astronomical objects, and learning the night sky.

I got into the hobby around lockdown, so a couple of years ago, and from the start have used the Celestron StarSense tech to get around, unless I am looking for something very obvious like the bright planets. However, I do find that I am also gradually learning the sky despite this reliance on technology - perhaps this is not in the immersive, all or nothing, sense that comes from being under the skies exclusively with a red light and a star map, but for me the star map comes on the journey as well, and is part of the overall experience. I'll spend time at the eyepiece, and time sitting back and looking at the sky in its entirety.

These are not mutually exclusive activities.

My biggest impediment is having a garden that faces west - the view south has trees and houses close by, so I have a very narrow window for observing Venus before it gets into the tree tops and yesterday was my first opportunity this year. I used my 80mm refractor with a Baader contrast booster and a variable polarising filter. Venus presented a well defined disk at roughly 3/4 phase, and with the contrast booster added there was just a hint of the cloud tops - but very little time for my eyes to acclimatise before it got too low

The positioning would be very awkward, but I'm tempted to mount my 10" Newtonian on the tripod to see how it performs in contrast on the next opportunity.

I agree with @SuburbanMak that Baader Orthoscopics are a good place to start. You could also consider the BST starguider eyepieces https://www.365astronomy.com/index.php?route=product/category&path=146_244 - they give a wider field of view and are more comfortable to use than Orthos, and fit a reasonable budget. I got along very happily with them for a while, but moved on to more expensive eyepieces that dealt better with coma at the edge of the field (not a problem for planets). If you are also looking at filters, I'd recommend a Baader Neodymium - expensive but in my opinion really improves the contrast on planets. On the expense side, I'd recommend checking out sites like UK Astro Buy and Sell, as well as the forums here for second hand gear.

What magnification to go for depends on the seeing you expect to have -  seeing is the limiting factor for planetary work. I usually observe from a city location in the evening before midnight - it's exceptional for my 10" dob to give useful magnification on planets beyond about x170 (i.e. a 7mm focal length eyepiece). A few times a year the seeing is better at that time and I might get down to 5mm or even 4mm. On the rare occasions I've been out at 4am, the seeing is better - but my productivity at work that day is pretty rubbish!

Great video, thanks for uploading. I've been so tied up with work I've not managed to get any time with the telescope during the daytime, despite some brilliant conditions

Hope I'm in a better position to see the next one.

Thanks Mark, that's good advice. I appreciate having talked it through. I  think I'll increase the wall thickness by another millimetre at that end of the connector.

The lead time from the engineers is about 5 weeks on the part, but I'll post back with a full report once I've received it.

Thanks Mark. The baader comes with m5 grub screws to fix to the dovetail. It also has a locking screw - so long as this is loose the part mounted on the dovetail can rotate, so the m68 adaptor can be reoriented.

One of my worries was that the dovetail would be secured by a 2mm thick piece of aluminium in design A, and this wouldn't be strong enough - but this doesn't seem to be a concern you have, so I'm reassured on that front.

Thanks Mark  - the dovetail part of the sketch is confusing, because the steeltrack has an integral dovetail:

Moreover the photo on astrosurf doesn't seem to show a dovetail - or am I missing it?

I really can't see how the dovetail in the sketch would connect to the steeltrack (unless the steeltrack is of an earlier design than the one above)

I'd like to connect a Baader Steeltrack to my ScopeTech STL80A-L - I've come across this thread on astrosurf - a french astonomy website - which suggests it is feasible http://www.astrosurf.com/topic/137491-changement-porte-oculaire-critères/ although I can't quite work out what is going on with the Baader side of the connection from the design sketch.

I've also found an engineering shop nearby who are willing to take on the production of a one-off part.

As the Baader side of the connection is not clear in the thread I can think of two possible design options, sketched in section below, but I'm very new to doing DIY on the telescope and I'd be interested which you thought would be the better design (or if an alternative would be better).

The options are

A - Connect to the Baader steeltrack using the steeltrack's integral 88mm dovetail. The custom part slides over the outside of the steeltrack and is screwed into the dovetail with 6x M5 screws

B- Connect to the Baader steeltrack using the M68 connector it comes with. The custom part is machined with a M68 thread and screws on.

In both cases the connecting piece slides inside the Scopetech tube, and is connected with 3x M4 screws.

Apologies for my sketch, but hopefully the options are clear:

On 06/01/2023 at 11:26, doublevodka said:

Definitely join your local Astro club, lots can be found on Facebook, that's how I got back into astronomy and purchased my first got from a club member. Bargains can be had from Facebook marketplace, but it certainly can be like the wild west too. There is a for sale section on this forum, but it won't appear until you've made enough posts on here (25 I think) or sites like https://www.astrobuysell.com/uk/index.php where everyone is generally an astronomer and helpful

Goto does add to costs, absolutely and to an extent anything electronic will devalue, but if you are buying used then someone else has already taken the initial hit. Smartphone apps like Astrohopper will get you in the general area

As for tabletop dobs in the garden, if you have an Ikea nearby - https://www.ikea.com/gb/en/p/kyrre-stool-birch-60416925/ 3 legged stools like this give decent stability like a tripod even on uneven surfaces, I use 2 with my starblast, on to sit on and one for the dob to sit on

Given an example of used - https://www.astrobuysell.com/uk/propview.php?view=193136 Skywatcher 130 Dob, pretty much half retail price and an honest ad with plenty of pics, it's really worth a look

Also worth updating your location on your profile, there may even be someone here on the forum nearby willing to help if you do end up looking at used equipment, on a tight budget it really helps you get more for your money 👍

Just to add to the tips for second hand equipment, members of this forum are very helpful if you want to talk potential purchases through and identify any pitfalls. My experience of buying second hand from here and from Astro Buy and Sell is that people are helpful, and equipment is well looked after.

With the caveat that I'm relatively new to this (got my first scope a couple of years ago - I'm sure more expert voices on the forum will have more insight) the optical quality will be good. A 150mm aperture will give decent views of the moon, Jupiter and Saturn, and deep sky objects, although the best views of the latter will need dark skies (and would be with any scope).

It won't be ideal for photography, but you should be able to get some pictures at the eyepiece. It has tracking capability so this will help a great deal.

I'm not familiar with the "astroseeker" part of the setup, but it looks Iike some kind of go-to system. This will probably need alignment with 3 bright stars to get started, but will be helpful navigating the skies.

the general recommendation on this forum is that it's a good scope (discussed under its skywatcher branding).

Overall it sounds like a decent telescope, so go for it!