saac

Shyam,  the problem is with the mount.  For any serious level of astrophotography you will need a motorised mount as PEMS commented above. Astrophotography, especially for DSO, requires long exposures so the mount needs to be able to track or follow the movement of the stars. A dobsonian style mount does not do this unless it is equipped with a special motorised base - these are generally DIY arrangements. The 10 inch Dob would be excellent for visual use but very limited for photography - you would be able to get afocal shots of say the moon or some very basic shots of the brighter plants but nothing else.  Keep asking questions fella, we are here to help. 

Jim 

21 hours ago, Thalestris24 said:

Hi Jim

I've currently fitted a 121mm fl, 26mm dia doublet from surplus shed for the collimator and a 100mm fl, 31mm dia doublet for the camera lens (think it must have come from my 2" ep but not sure... Still not put the Ovio slit in - will aim to do that tomorrow I don't think I'll worry about IR passing through for now. If there seems to be a problem I have some blackboard black spray paint - might be worth trying, though I don't have any infra red data on it. Oh, I never got my slit holder locking ring to screw in but I can push/click it in, so think that will do . Did you get the 600 lpm grating? You have to be careful with Thorlabs ordering - first time round I inadvertently ordered an IR version - tut! But they kindly sent me a replacement visible light one together with another box of lab snacks!

No rush - we can take our time. The stars will still be there

Louise

Thanks Louise.  My doublets from Surplus shed weren't cemented together - two separate lenses. I'm assuming I just place them together and maybe tape the rims together. Or have I got that completely wrong - I wouldn't be surprised   I went for the 1800 lines per mm grating, maybe without any great thought actually as to how to match that to the cameras I have.  I was keen on the idea of seeing if I can make use of the device in the classroom as well - we cover spectra and emission lines in the syllabus generally using 1800 transmission gratings and I've always wanted to show them via a camera set up. Off to Paris tomorrow on a school trip so progress with be put on hold until "le weekend" - assuming we get back what with the strikes   Good progress Louise I think you are right about the emergence of a spectra in you last post. I'm really impressed by this, it's a nice fun project with really good application as shows the potential of the 3d printers well. 

Jim 

Hey Louise, I now have my grating (Thor Lab) , OVIO slit (some french company)  and lenses (Surplus Shed). The lenses from Surplus shed were nearest match to those specified so I'm not overly confident they will match well - worth a go though.  I'm printing out all the internal components now; just done the grating holder assembly (lots of fettleing required) and now the Ovio slit holder.  Re the CFC lamps you can still get them on Amazon surprisingly , like you I thought they had all but disappeared now - nobody wanted them because of the warm up period.    So,  I'm still good bit behind you, may not get it done this side of Christmas, but I'm following your progress with great interest and making notes. Good luck with your test phase. 

Jim 

2 minutes ago, Thalestris24 said:

What, under starlight?

Louise

That's what I'm confused about ?

Jim 

5 minutes ago, ejp1684 said:

I've found it does let through IR so I've covered mine with aluminium foil. I had some roof flashing so used that on the main sections and kitchen foil on awkward sections. If kitchen foil was good enough for the Pioneer spacecraft, it's good enough for me!

Eric.

Wait, I'm confused, not difficult, won't IR be present in the light from the target anyway?  is this background IR we are talking about and is it really significant to cause a high SN ratio?

Jim 

2 minutes ago, ollypenrice said:

True, but this glosses over the extraordinary effects of marketing and the devious skills of those who manage it...

Olly

"The Heart wants what it wants - or else it does not care"

Jim 

58 minutes ago, BabyPepper said:

If i can build one- .99 strehl telescope objective per year and 10,000 people want that one objective, how much is that telescope worth? Who determins that price scale for supply and demand?

 

The individual who is prepared to part with the seller's asking price. Not really anymore complicated than that  

Jim 

Wow, $21 k , wonder if they had a Black Friday in 1923  

Jim 

1 hour ago, Skipper Billy said:

In the image above it is largely processed out - it is very noticeable in the individual subs - particularly the 2x2 subs. AFAIK its a column of pixels that just doesn't work.

 

Thanks Billy I see what you mean with the individual sub, it is more noticeable there. Thanks for the explanation I had thought that but wasn't 100% sure; if that is a permanent feature  on the camera I can see it would be really frustrating.  I really hope you can get it sorted out .  As before I think that is an otherwise cracking image and my favourite object in the night sky. 

Jim 

Anybody else nervous watching them lift the mirror?

Jim 

On 07/11/2019 at 20:33, spillage said:

 Even she has noticed that we have not  had a clear night in an age. 

Isn't that the main problem, I couldn't justify it given the usage it would ever get. That said it is a lovely bit of kit  

Jim 

Billy I can see the effect in the image that you are talking about albeit if you hadn't said it would be hard to notice. It is an otherwise lovely shot of Pleiades.  As mentioned above I do hope you can get it resolved either by warranty or by processing out.  Just for info could you explain what exactly is meant by a dead column  - is it simply a column on the sensor which is not not reading and is it a common problem?

Jim 

3 hours ago, Synchronicity said:

I hope it's ok to hijack this thread for a bit and ask about combined 3d printer / CNC / laser etching machines.  I stumbled across an article about the forthcoming SnapMaker 2 and see that there are a few manufacturers doing these.  I've also found some articles on how to add the functionality to a standard Creality CR-10. 

Does anyone have any experience or recommendations?

A cast iron justification for needing one would also help as my wife is somewhat sceptical 🙂

Thanks

Michael

Michael, I have a dedicated laser engraver/cutter.  You will want to think about exhaust extraction for the laser engraver it's essential when cutting plywood and some plastics. This will have an impact on where you would site your unit.  Extraction can be noisy and depending on the type  of laser you go for (gas or solid state ) you may need also to think about a water cooling supply. Personally I would avoid these combined units; quite often it will try to be good at everything but end up being poor at each (different design criterion for each mode).   I guess what you need to ask is what would you be using it for and how often would you be using it .  

Jim 

Louise that's great, thanks very much for taking the time to post that it will save me a bit of time searching.    I'm slowly going through the lens finder on Surplus Shed now.  I still can't get over that Ovio web site - absolute nightmare. Never mind though I'm so pleased about the main body being finished , onto the other parts tomorrow.  I'm mindful of the issues you had with the T2 screw printing so fingers crossed. 

Jim  

Thanks Lousie , I was about to ask about the other components.  I've been following your other thread and have just ordered the grating from Thor Lab, the lenses there look a wee bit pricey so I'll take your lead and have a look at surplus shed. Did you find an exact match for the lenses as per the material list for the spectrometer.     What about the micrometer stem , where did you source that?

Lol my main body has just finished printing - good to get that done; my longest print so far about a day and 5 hours I think !! 

Jim 

Lousie I wish I had found this thread earlier , I've just wasted about 30 minutes doing exactly what you did - what a truly awful web site  .  The alternative supplier https://en.jeulin.fr/simple-radial-slits-212076.html provided by Eric now also sells the slit disc without the mount, also a little bit cheaper than the mounted one.  I've placed an order for that so time will tell , fingers crossed.  

Jim 

Ciao Armando , good to have you on board and looking forward to seeing your posts.  Do you have a dark sky where you live ?

Jim 

8 minutes ago, andrew s said:

You pays your money and takes your choice.

Regards Andrew 

Is that a rebuttal of Einstein's quip about God not playing dice with the universe .  

Jim 

1 hour ago, andrew s said:

The paper describing the observation on which this is based gets a poor reception on Physics forum. It seems they come up with new breakthroughs all the time that are not substantiated .

Might be true but don't  hold your breath.

Work is ongoing in many areas "beyond the standard model" .

Regards Andrew 

I thought that may be the case Andrew, and rightly so, extraordinary claims require extraordinary evidence as Carl Sagan said.  I thought it unusual that they weren't offering evidence as such but rather a defence of the justification of a fifth force. Again I don't pretend to understand half of it;  still plodding my way through it .  I'm not rushing to renew my power point on the standard model yet

Jim 

Jim 

Andrew beat me to it  

Jim 

Beep,beep, beep, beep, - the sound of SGL Physics backing up  

Jim 

Not sure if this has been posted before but it may be of interest. If I have understood it properly the paper sets out a case (University of California) for a fifth fundamental force. Apparently the possible presence of a fifth fundamental force has been discussed for some time (c1960s), I was completely unaware of this being blissfully secure and happy with thinking of only four  . This latest paper would appear to offer a more confident expectation of a fifth force and, as seems to be the way now, may even offer a route to further understanding of the proposed dark energy.  It's the type of paper that I'm certainly going to need to read over several times even though it's fairly well written  

Jim

https://arxiv.org/pdf/1604.07411v1.pdf

Some other background reading 

Wikipedia - Fifth Force

Ah I see it now, thanks Lousie.

Jim 

Louise might be worth a look on Astroboot they sometimes have extension tubes of various sizes and threads or cheap eyepiece tubes that could be cannibalised - might be able to adapt something there. Alternatively what about a push fit with a compression ring like those used on Moonlite focusers. I guess I'll be up against the same problem further down the line.  Sorry , thread drift (no pun intended)  

Jim 

5 minutes ago, Thalestris24 said:

I received the replacement screen from China last week. Installed it yesterday and the (new) rotary encoder works properly - yay! My 3D printing quality of life has greatly improved But I'm still struggling to get T2 threads to print out nicely - not sure if it's just shrinkage or other inaccuracies. Of course, I've tried scaling to counteract shrinkage but it never comes out quite right! It may be that I have to scale in one axis, or two axes, only? It's a bit trial and error! 

Louise

Well done Louise and good for them sorting you out with a replacement. Just shows you sometimes making the effort to complain about faulty goods does pay off.  Good luck with printing the threads I haven't done that yet but I'm about to follow you down the path on the Low Spec , my black PLA arrived today  

Jim