saac

If it is just the mirror set you want it may be worth just flying out. I'd speak to the carrier before to find out what arrangements they could offer regarding unusual/outsize hold baggage; you would need to arrange for suitable secure packaging. Alternatively, you could even buy the mirror set a seat and let it fly in comfort with a window seat next to you .  Seriously, I would speak to the carrier, they will generally go out of their way to help you with unusual baggage.  As for grinding a mirror that size, you have my repeat for ambition at least, it is a considerable undertaking.  My 12 inch grind of some years ago stalled at the figuring stage; it was a time sponge. Very rewarding though. Good luck with the project that is some serious aperture, I'm still getting to grips with the school's 16 inch dob. 

Jim   

2 hours ago, AndyThilo said:

Yeah it's not looking good lol. Hopefully I get some clear sky tomorrow to take some test shots of Pleiades to compare with the scope having no rings and a basic UV/IR filter fitted. On the plus side, I might be having it checked by a certain optical master who lives very close to me :). 

Drop Skipper Billy a note , if I remember correctly he experienced a similar problem, albeit on a different setup, same target thought from what I remember. 

Jim 

It's the " Star Link Constallation".  Legend tells of a mad scientist who in the early part of the 21 century was so possessed by the notion that nature could be improved upon by technology that he filled the night sky with thousands of artificial stars so that we would never again experience the terror of a dark sky.  It is the most unusual constellation in the night sky being visible all year round in each hemisphere  

Jim  

Well that is unfortunate and a somewhat shortsighted by Celestron I would have thought ! I guess other so called "push to " apps are available, doesn't SkySafari do something like that ?

Edited,  - just read that the Celestron app uses a form of plate solving using a stored database the other push to apps I was thinking about I believe just point to a locations using GPS reference and are reliant on an initial alignment. 

Jim 

48 minutes ago, Stu said:

This App was just flagged up to me which looks interesting. Have downloaded it and will give it a try.

Anyone used it yet?

https://www.gizmodo.co.uk/2020/01/ces-2020-facial-recognition-for-stars-lets-this-telescope-automatically-find-objects-in-the-night-sky/

Looks interesting and might be something I would consider for use on the school's big Dobsonian; be interested in any follow up report Stu once you give it  a shake down.

Jim 

34 minutes ago, AngryDonkey said:

No sure where 'facial recognition' comes into it.... 🤣

When you take it out and setup it sees that you are happy and issues a sarcastic  "you must be optimistic"   It then waits and again looks at the expression on your face when you see it clouding over and then auto powers down. 

Jim 

5 hours ago, Dave Lloyd said:

Ahh, to lose the long term pleasure of a symmetrical Orion for the fleeting thrill of a supernova blast. 

Yes definitely a bitter sweet moment Dave.

Jim 

36 minutes ago, Gina said:

Watching a farming programme on TV and just seen a huge maize drill (farm machine) entirely 3D printed!!  Amazing!

What was the material Gina, metal?  The inroads industrial 3D printing has made is impressive. 

Jim 

popeye have a read at this thread I think it may be what you are looking for. 

Jim 

Good revision to the grating holder Paul; I really like the easy swap out functionality of the design.  I'm just about nearing completion of mine using the previsions design, assembling the optical components now.  It's a great thing you have done sharing this with the community, thanks again.   

Jim 

Try removing the shaft from the other end - remove the dual focus knob (right hand side) then slide the shaft out from right to left.  I'm not familiar with that particular focuser but it may well be that there is a second grub screw securing the connector hidden from your view where the connector enters the body of the focuser (left hand side). 

Jim  

I agree, an amazing sketch. 

Jim 

Well, the bar for photographs of Jupiter just got pushed a little higher  

Jim 

To be honest for that type of money I would prefer to go down the NV route (white phosphorus preferably) .  

Jim 

Think of the possibilities that await for it Gina, whatever will be will be😀 

Jim

 Filament anxiety, I know it well James😀

Jim

Cool mod Kevin. 😀

Jim 

Louise hi, I’m still a good bit behind you. I was hoping to finish printing the remaining internals (lens holders and lid) but last night I found that my laptop hard drive had crashed. It’s completly dead so Ihad to order a replacement which I could do without just before christmas😩 Anyway hopefully it will be here at the weekend and I can get started again. ,I’m using my small iPad to type this and I detest using the touch screen to type. 

I think you are doing amazingly well and Ken’s advice is brilliant. I don’t expect to be in a position to get my optics installed until after the new year, like I said before I suspect I will need to reorder some lenses. I will keep you posted😊

When I used the Star Analyser grating (about 2 years ago now )  I did the processing with RSpec. I may be wrong but I seem to remember  that RSpec provided  some functionality that allowed you to rotate the spectra until the lines were vertical.  I've never used BAS, I take it that there is nothing similar in the software then that would allow you to rotate the spectra. 

Jim 

19 minutes ago, Thalestris24 said:

I've calmed down a bit now - just a bit! Had to walk away from it last night.

Louise

Don't be afraid to set it aside for a day or two. I've seen myself working on a problem on my car and getting frustrated at getting nowhere fast. Not unusual for me to come back after setting it aside for a few days or a week and it's as though the problem was never there .  The gremlins know we are getting frustrated so they bunker down for fun  

Jim 

1 hour ago, Thalestris24 said:

Hi Jim

Yeah, you have to be careful what you order... I got the mirrors from Thorlabs - I only fitted them the other day! I got some round and square 1" craft mirrors of Ebay - very cheap! I used them in place of the proper ones until I was ready. The Thorlabs ones are a little expensive for what they are but not that much in absolute terms - plus they fit perfectly. I've got so far but am struggling a bit with the finer points. I don't think mine will be stable enough for astro-spectrometry. Getting and maintaining focus is proving very difficult. I'm sometimes getting some odd results but don't understand why.

Here's one I just did of the CFL bulb:

I think that's the zeroth order on the left and I've flipped it so it should fit Ken's calibration ok. It's all on a slant - not sure why. The spectral lines are slanted too - presumably to do with the seating of the grating. I've tried to adjust it but to no avail. I'm getting old and tired and impatient! I'm losing my grip - keep dropping things, and my cataracts make it hard to see what I'm doing! My back's been killing me too. I think 2020 will be my last year of doing astro things .

Louise

I know things like that can make this sort of work really frustrating - my mum suffers from arthritis in her hands and it really restricts what she is able to do and I can see that it lies ahead of me as well at some stage  Keep at it Louise for as long as you can, the mind needs to be challenged. I think as well you should be really proud of what you have achieved so far; you are going to overcome these problems for sure - I'm relying on you as I build mine behind you  

Jim 

32 minutes ago, Thalestris24 said:

I got mine from Surplus Shed too - they are fine! I wasn't going to pay Thorlabs prices!

Louise

Louise I think I was a little too casual with the specifications when I placed the order , a few look too large  - oops  .   I'm looking to have all the internals printed off by the weekend coming and then I will play around with fitting the optics to see exactly what I have have. I'm also still waiting for the micrometer head it's on the slow boat from China   I've yet to place an order for the mirrors but I have a couple of first surface ones from previous projects again they may or may not fit .  Until then I'm enjoying reading the progress you are making  

Jim 

On 09/12/2019 at 22:16, Merlin66 said:

Jim,

The separate lenses of the doublets..... you'll need to space them. Three small strips of sellotape equally spaced around the circumference would work.

The SimSpec spreadsheet with give you a good approximation of wavelength coverage with your camera, as well as the resolution.

 

 

SimSpec V4.3_Paul3D.xls 78.5 kB · 3 downloads

Ken, thanks for that. I ordered the lenses in haste as they were a good bit cheaper on Surplus Shed compared to ThorLab or EO. I'll give it a go and see what happens. Thanks for the SimSpec spreadsheet as well, something to play with over the Christmas holidays. 

Jim 

That was a lovely telescope. It was the kind that I imagined Ogilvy the astronomer in HG Wells' War of The World would have used to observe the green flares from Mars  

Jim 

Shyam, here is a link to a project build for a DOB equatorial tracking base; if you have a basic mechanical DIY skill level then this is a straightforward project. This type of base would allow your dob scope to track the stars and do hence some astrophotography .

Dobsonian Equatorial Tracking Base

Jim