cwis

1 hour ago, craftui said:

Thank you for sharing your perspective and experience @cwis - enormously helpful.

Well, I'm not sure what an "Airy disk" looks like but when I stuck a 5mm eyepiece into Heritage a while ago I really didn't like what I saw. So I replaced it with a 7mm and concluded that's the highest power I should use on most nights. Would I be able to increase power with an 8 or 10 inch? Because my 7mm would yield 170x or more at that point - would it look better than Heritage what showed at 150x with a 5mm? I imagine so because it would gather more light to compensate for higher power? But I maybe completely wrong, in which case I'd need to replace my treasured 7mm 😢.  

Have a read of this:

https://calgary.rasc.ca/seeing.htm

On a perfect still clear night, the stars through the telescope look like blobs, with a ring round them. You may see more than one ring, I never have. It's basically a diffraction pattern.

The larger diameter the telescope, the smaller the blobs and rings for the same magnification, as the resolution of the telescope increases it resolves the point light source of the stars more accurately, if you will. And of course they will be brighter.

On more normal nights with poor seeing, the wibble from the atmosphere interferes with the starlight and the patterns start to move - the blob wiggles about and the rings break and reform. That page I linked has very accurate simulations and tables showing various scales for estimating seeing - others may disagree but what I expect in the UK when I step outside on an average clear night is a Pickering 4 or 5 - or "Poor" seeing. This btw will make Jupiter look like it's on fire as your description states - so you were using too much magnification for the seeing you were experiencing. 

Winding back the mag decreases the wobble and sharpens the image. But it obviously makes everything smaller!

@sorrimen makes some very good points about exit pupil too but you're probably too young to have to deal with too many floaters etc so this probably isn't the issue you were experiencing. What 5mm eyepiece did you try, out of interest? It wasn't a Plossl was it?

2 hours ago, craftui said:

Andromeda is a smudge but clusters and double stars are very beautiful from here, and so are the planets. Also my Hertitage frames everything so well with the 7 and 11mm eyepieces. I just want a little more detail to enjoy the viewing from where I am, without having to travel. 

For example, I’d love to be able to resolve objects like the double double, see the banding on Jupiter more clearly, see M13 with a bit more sparkle of individual stars. It always feels like I’m just outside of my ability to resolve some of the objects... Higher powers don’t solve it for me with the Heritage, everything just gets dark and noisy and I start loosing detail above 100x. Just a few examples to explain what I’m after.

I'm in a BortIe 5 area and went from a 5 inch newt on a goto to a 10 inch dob so I might have some useful input...

Yup - it's better. Much better. More light, more resolution. Sharper larger planets. Barges on Jupiter! Big red spot! Deeper resolution of clusters! Colour in clusters! Amazing moon! Craters less than 3km across!  E and F in Orion! 

When the sky is perfect that is...

So most of the time it's better. Slightly better. Only slightly. Andromeda is still a smudge. It's a bigger brighter smudge. Get a really clear dark night and you see some structure. 5 nights in the last year perhaps?

I can split the double double with my 5 inch on a good night. On an average or poor night the 10 inch struggles with it... It's all about the seeing.

The maximum practical resolution of my 10 inch is 500x I think. In a vacuum. On the average evening it's more like 150-180 depending on your target. Planets 200 maybe? I think I've used more than 250 on Jupiter once in the last 2 viewing seasons, and more than 300 on the moon exactly once ever. 

Stick a reasonably high mag eyepiece in your current telescope - say 200 times. Look at a bright star. Can you see the Airy disk? No? Just a wobbly squiggle in the sky? Your telescope is better than the seeing at that point then. A bigger one won't help...

That telescope will squash the tripod that came with your Bresser flat! A better tripod and mount will cost more than the 'scope.

If you want a bigger telecope, relatively cheaply, the answer is a Dobsonian. Bresser make some really good ones that may be available in your location:

https://www.astroshop.eu/telescopes/bresser-dobson-telescope-n-200-1200-messier-hexafoc-dob/p,47842

They have nice large focus tubes and decent focus mechanisms that will carry your camera easily. Although a tracking mount is best for photograpy, a few people do even deep sky photograpy with a Dobsonian...

This is probably cheating....

Cheapy binocular objective lens screwed into a 3d printed adapter with a budget prism from a Meade ST80.

I'd like a lightweight RACI so this was a test - seems to work OK!  I'm on the look out for a second hand crosshair eyepiece and I'll then shim it to get the focus correct. MK2 will have the dovetail to fit to the scope printed in...

No worries! I'm now looking lustfully as the orrerys on the Cochranes  - they are magical things...

I didn't have to write a program - here's an online model:

http://cosinekitty.com/solar_system.html

Untick realtime update, set Cartesian coodinates to Helicentric, Angular Coordinates to Ecliptic. Then stick your date in to get the numbers you want in the Ecl. Long. column.

I tested it against the table in your Cochranes link against a couple of years and got the same numbers.

33 minutes ago, Chaz2b said:

The calculations given from Cochranes are from the first day of the month, also relative from the sun.

I cannot download the page from their site, but it’s www.cochranes.co.uk. then astronomy then orrery, heliocentric longitudes.

Will that help?

chaz

Ah I see! Yes - that helps!

Hello! Would the angles be relative to the position of the Earth? It looks like something you could calculate fairly easily using Python and Skyfield - the program would only be about 7 lines long!

I can help if you like? If you give me an existing calculation for a day I can understand what you want and also sanitly check any numbers I get before I bother you...

Can confirm! This idiot just got some funny looks out in the street... 

Hi all,

to close off this topic nicely, I wrote Brendan a simple Python program to get the data he needed, which I've enclosed in case anyone else finds it handy!  I've commented it fairly extensively so it's probably a nice base for hacking about with even if you're a newcomer to Python (which I am too!)

During the course of my research I found the source that I think Brendan's original web source was using - it's the JPL Horizon app, and access is free:

https://ssd.jpl.nasa.gov/horizons/app.html#/ 

API access is also free...  I think the issue Brendan had was caused by the parser on the website he was using not being set up to deal will NULL fields from the JPL API - the previous value in that field was printed instead. Tut tut!

The Python program uses the module skyfield as mentioned in a previous post. If anyone wants to mess with the program (assuming windows):

Install Python https://www.python.org/downloads/windows/  

Once done:

In a cmd window type "pip install skyfield" and hit enter (this downloads and installs the module required by the program and supporting modules).

Download the program from this post and stick it in a folder.

Navigate to the folder with your cmd window and type "domaths.py" and hit enter to run it. It will output to the screen - redirect to a file in the same directory like this: "domaths.py > afile.csv"

Currently it will print out a year's worth of data, and the location for moonrise calculations etc is set to my house - both can easily be changed by editing the program in a text editor and saving it:

Change this line to match your location:

yourhouse = api.wgs84.latlon(+51.6441483, 0.7694381)

Change this line to change the number of days:

datelist = list((base + delta *x for x in range(1,365))) 

If anyone wants assistance or questions about this program answering - ask!

domaths.py

I've had one a few years and print bits and bobs in ABS. @adyj1 is correct though - it ends up being another hobby. I've replaced the hotend, the control board, the bearings, the bed, built an enclosure, run it over the network with a Raspberry Pi.... Now it's dialled in it is pretty much plug and play - I have to fiddle a bit to get dimensionally accurate pieces for push fitting bearings or pcb boards, but that's my fault for using ABS.

It's a slippery slope though...

Now I want a lathe. And a mill....

Oh yeah - and could you chuck me an extract of your spreadsheet so I know what I'm trying to produce?

Hmmm. 

Does this data look valid? It's calculated between timenow and timelater (24 hours from now) for the moon. I THINK it's in GMT but the time settings are obviously critical in this and I'm trying to get my head round them... Not sure the location is set correctly in my Pi and I'll need to do that to get a valid datetime object.

I'm just cutting and pasting various examples in the docs at the mo - fastest way to gain understanding!

timenow 2022-02-22 17:49
timelater 2022-02-23 17:49
2022-02-23 00:47 Rise
2022-02-23 09:34 Set
['Meridian transit', 'Antimeridian transit']
['2022-02-23 05:16', '2022-02-23 17:44']
Ra now  15h 04m 07.35s
Dec now -16deg 38' 03.1"
Moon phase now: 254.5 degrees
 

If I get sensible numbers I know I have the datetime correct and I can sort out the rest of the calcs and format the output for you! It looks like the data comes back in arrays thanks to numpy so that should be pretty easy.

Edited to add - locations is (+51.6441483, 0.7694381)

3 minutes ago, BrendanC said:

Thanks! It's a very kind offer, and if your Python prog could do this for my lat/long, for a year (or more!), outputting a nice CSV or similar format, I'd definitely be up for it. Only if you'd be doing this for your own amusement (which is kind of what I'm doing with this spreadsheet, truth be told).  Ideally it would also do the Moon's RA, Dec, culmination, height at culmination and phase, but I realise that's pushing it...! 

Well I'm kind of forcing myself to learn Python at the moment so an interesting short task is probably ideal.

Let's start with moonrise and moonset and I'll add the rest of the columns - those two look the hardest believe it or not.

The charts go to 2050 by the way...

I'll fire up my python environment (Raspberry zero!) and get started.  I may be able to find somewhere to host it online too - may be handy!

Funnily enough I was looking at at Python module that can calculate that sort of thing earlier today.

https://rhodesmill.org/skyfield/

https://rhodesmill.org/skyfield/almanac.html#risings-and-settings

Want me to have delve for you? I'm not a Python person but it seems simple enough for what you want it to do...

To push back a bit in the other direction with your concerns about the optics...

I got a 130mm F5 goto newt as my first scope, and after 6 months or so I "upgraded" to a 250mm F5 dob.  I say "upgraded" in quotes because upgraded would normally mean I replaced one scope with another   - of course not, I now have two scopes!  (Actually 4 but that's another story...)

Obviously it then became all about the new scope, and the 130 was neglected.

Then one night I dragged my "old" 130 out for a session -  I needed goto to find some target or other.

I was amazed how competant it was! Yes the views were dimmer, or smaller, or less sharp than the dob, (or all three!) but not by as much as I remembered - it held up very well in comparison. 

So maybe the jump in performance isn't as great as you were expecting? It may not be such a jump in badly LP skies with average UK seeing...

Try to play towards some of the inherent strengths of the larger scope notwithstanding your LP - higher mag views of the planets (not long to wait now!), or split some tight doubles - you may then see it pull away from your smaller scope in perceived performance...

31 minutes ago, Second Time Around said:

The Altair ones are, Steve.  Here's a link to their website and a review:

https://www.altairastro.com/altair-24mm-ultraflat-eyepiece---precision-barrel-stainless-steel-237-p.asp

https://www.skyatnightmagazine.com/reviews/eyepieces/altair-ultraflat-eyepieces-review/

Had I not had the now discontinued 22mm Vixen LVWs I'd been tempted myself.

Interesting - now £125! The AA 24mm UFF was £135 when I bought one 18 months ago. Must be responding to the introduction of the Svbony UFF clones. - they don't do a 24mm yet though.

I really rate my 24mm UFF (not that I have much experience!) 

I use SS6 Pro on an S6 - it runs fine but the downloads/updates of files if you've not started it for a while take AGES. I just fired it up a few times and closed it down and eventually it shows fewer files to download and the process completes. Make sure you're on your Wifi - some of the files are HUGE and look out for alerts and confirmation boxes from the google store app etc as this can hang the process. One dialog box in particular I remember I had to answer but it only showed on the status bar - it didn't pop up. I forget what it was asking - sorry! 

Having said that: my phone ONLY has SS6 and SynScan on it (it's an old phone I use just for astro stuff) so if you've less storage space available maybe it will run even slower..

If you persist with the S6 fire up SS6 every week or so to let it update - even if it's cloudy!

22 minutes ago, sonicninja said:

Does this look about right?

Also, very quickly. Is it possibly to over-tighten the grub screw clutch on a telescope like this. My horizontal control seems to be either loose or ,once the clutch is tightened, completely unmovable. I wonder if Ive over tightened it at some point meaning I cant really use the precise controls

 

That looks pretty much OK!

You are looking for:

1).  The secondary mirror looks like a perfect circle and is bang in the middle of the focus tube.

It's a bit difficult to make out from the pic above but it might be a bit out - looks a little to the right and down from centre. But you be the judge - it could be the pic... Looks circular though - excellent!

2). The primary mirror reflection is centred so the three clips and maybe the mount for the primary (depending on how far the focus tube is racked out)  is concentric with the outside of the secondary mirror

I'd say - yup - looks good on that one.

3). With both the above satisfied, the black dot of the refection of the hole in the collimation cap is in the middle of the doughnut in the centre of the primary mirror.

Yup on that one.

So - check on point 1) - but it looks like it's fine.

Personally, even if it's a bit out with point 1). I'd leave it - it's probably better than the average eyeball at this point anyway.  Astrophotographers have to be far more picky with regard to collimation... 

Read up on doing a star test and do one next time you're out for the final check under real conditions.

I'd also recommend a table top dob like Heritage 130, but for another reason.

With a tripod and a telescope, you'll need a stool for you, and a taller stool for her - the eyepiece is going to be up there, somewhere, from her point of view. Or one of you will be crouching, or standing. Not ideal.

With a table top dob, she can sit on the table, or put the 'scope on the floor. The eyepiece will be at her height.

https://www.harrisontelescopes.co.uk/acatalog/skywatcher-heritage-130p-flextube-dobsonian-telescope.html#SID=1701

That'll show (on a good night) Saturn's rings, the great red spot on Jupiter, the ice caps on Mars, etc etc..  It's also got the aperture for some deep sky objects too.

People call 8 inch Dobsonians the Transit vans of telescopes because of their all round flexibility.  If so, the Heritage 130 is the Transit Connect. Not quite as capable, but easier to park.

51 minutes ago, sonicninja said:

Just purchased the collimation cap so I'll start there. Like a lot of budding new astronomers my expectation is usually based on the images users on this and other forums upload who have painstakingly processed and refined their original photo.

Here are some collimation scenarios for you from my 130PS

Pic 1).

The secondary mirror is properly aligned with the primary mirror, because the outer parts of the mirror mount (the black circle) and the three mirror clips (with two Philips screws on each) are nice and concentric in the secondary mirror, and it looks like a circle as viewed through the collimation cap. Unfortunately the primary mirror is not correctly aligned - the refection of the hole in the collimation cap (the black dot in the centre of the photo) should be inside the white doughnut in the centre of primary mirror. This would indicate the primary mirror is looking directly at the centre of the secondary mirror and therefore directly at the middle of the focus tube and the collimation cap - as you can see below, it's not.

The green is a plastic bag I put the other side of the secondary mirror mount from the focuser to make the edges of the secondary mirror clear as otherwise it all gets confusing (for me!) 

Pic2).

The secondary mirror is not correctly aligned. It looks a bit squashed (not a full circle) and the reflection of the primary mirror is not in its middle.  It does point at the middle of the primary mirror, but this will not result in sharp planets in the centre of the view - there will be a sharp spot off to one side somewhere which will be a fair bit smaller...  

Pic 3).

This is what you should expect to see.  The clips in view around the outside so the primary mirror reflection is central,  and the dot is in the middle of the doughnut so everything is lined up.

32 minutes ago, Louis D said:

I did notice in daytime usage that just as the field stop comes into view, a shadow ring appears just inside it if you continue to look on axis.  If you pull back enough to get rid of the shadow, you lose the field stop.  If you look at the field stop and tilt your head properly, the shadow goes away.  Perhaps this is what the OP is seeing?

That sounds about right What  causing this effect?

I must have deep set eyes because I'm mashing my face into the eyecup to see the field stop... But if I fold it down then I get blackouts etc - too close.

8 minutes ago, sonicninja said:

To be honest I'll probably get some that suit my current level in the hobby i.e not utter rubbish from Aliexpress but nothing too fancy. I'll get a known brand so I know they're at least half decent.

Consider something like this from Aliexpress (the 8-24mm one as I think there are a few decent 8-24mm designs that everyone copies) 

https://www.amazon.co.uk/SVBONY-SV135-Eyepiece-7mm-21mm-Telescope/dp/B08D5XZ3KP/ref=asc_df_B07Z64NK65/?tag=googshopuk-21&linkCode=df0&hvadid=463026995977&hvpos=&hvnetw=g&hvrand=12064661647744846715&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=1006798&hvtargid=pla-932117012575&th=1

It will be better than the two you have currently and you can use it with your 2x barlow to get suitable magnifications for planets.

It could be the only eyepiece you need for a while! I got a Seben branded one and didn't use anything else for nearly a year.

I still use it fairly often now and I'm looking at the next step of either spending a lot more money on a better zoom or on fixed eyepieces to cover the same range...

17 hours ago, sonicninja said:

Thanks everyone, this is perfect. You're all talking me out of spending my daughters future inheritance! Can anyone suggest any eyepieces that might be an advantage with my current set-up?

 

You need a compromise. In the UK you can rarely go beyond 200x magnification due to atmospheric conditions so if you buy an eyepiece that gives you 200+ magnification you're not going to be using it very much or you will be putting up with a mushy fuzzy views of the planets that will have you doubting your telescope.

Also you will be constantly chasing the planets with your manual mount as they rush across the sky due to how zoomed in your view is...

 Lower magnification views will suit the viewing conditions more often giving you lovely sharp detailed planets more often. And you won't be chasing them around the sky as much either - they will stay in view for longer. The trade off obviously is that lower magnifications give you smaller planets!  With time and practice this will cease to be an issue to you as your eye and brain get better at pulling detail out of the small (but sharp and detailed) planet, detail that wouldn't be there at all if you over magnified with the wrong eyepiece for the conditions.

Opinions on the correct eyepiece are going to be like tummy buttons (everybody has one!) so here's my choice based on experience with the same targets and 'scope:

https://www.firstlightoptics.com/ovl-eyepieces/ovl-nirvana-es-uwa-82-ultrawide-eyepieces.html  The 4mm one. 

Lovely and sharp, wideangle view so things stay in frame for longer, and reasonable cost wise.  The only downside I have experienced is that it tends to mist up easily, so keep it in a pocket or somewhere warm when you're not actually using it. Out of stock though - one might come up second hand I suppose.

The BST 5mm would also be a good choice with slightly lower magnification - the  3.2mm I would say magnifies too much for the UK with your 'scope:

https://www.firstlightoptics.com/bst-starguider-eyepieces/bst-starguider-60-5mm-ed-eyepiece.html

You can check your collimation cheaply with a collimation cap by the way:

https://www.firstlightoptics.com/other-collimation-tools/rigel-aline-collimation-cap.html

I have the 130PS and the focuser can be vastly improved by taking it apart, cleaning the glue out that they seem to have inadvertently used instead of grease, and replacing it with actual grease! Then glue a jam jar lid to one side to "gear it down"  - far better.

I've used mine with a 4mm eyepiece (160 odd times magnification) and I've seen the Cassini division and cloud bands on Saturn, cloud bands, shadows of moons and the GRS on Jupiter, the polar ice cap and surface details on Mars (last year obviously) etc etc  - I found it VERY capable once it returned from FLO collimated. I unfortunately originally got one that was not collimated out of the box - the only one FLO had heard of at the time.  

What eyepiece are you currently using to view the planets? You may just need a different one!